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Chapter 6-Scan Parameters

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This chapter describes the Scan Parameters area of the Exam window and

provides detailed information about each parameter. These selections allow you

to customize your scans and processing in various ways.

6-1

0AS Is~ MRI System Reference Manual T'hoe htlent MqiMt

Scan Parameters Area

6-2

The default location for the Scan Parameters area is on the right side of the

Exam window, as shown in figure 6-1. The Scan Parameters area can be

displayed on either side ofthe Exam window. To change the display location,

refer to the "Displaying the Scan Parameters Area" section in this chapter.

Figure 6-1. The default location for the Scan Parameters area.

This area contains the Slice Stack Moving area, the Basic tab, and the All

tab. The Basic and All tabs are described in this chapter while the Slice Stack Moving area is described in Chapter 5. Refer to Chapter 5, Exam Window

Scanning Functions, for complete Slice Stack Moving area details.

• Basic tab-Contains the 12 default parameters and any parameters that have

been added to the tab.

• All tab -Contains all the parameters in the Oasis MRI system, including the

default parameters listed on the Basic tab.

These tabs are described in the following sections.

Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

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Scan Parameters 0 Basic Tab

The Basic tab contains the fo llowing 12 default parameters, as shown in figure

6-2:

• FOV

• TR

• TE

• FA

• Thickness

• Interval

• Multi slice

• Freq#

• Phase#

• NSA

• Sync. Stop Watch

• Gating

Sync StopWatch

- f otf IIIIIIII'Fo=ff~====,

Figure 6-2. The 12 default parameters on the Basic tab.

6-3

0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt

6-4

This tab also contains any parameters that have been added. To add a parameter

to the Basic tab, follow these steps:

I. Click the All tab and drag the scroll box to the bottom of the scro ll bar to

reveal the Config button, as shown in figure 6-3 .

Click DC Level

Reg1on Cut

W-Width1

W-Levell

Shce Ord A

Shce Ord S

Shce Ord C

Plane Order

Rad1al Stack

L1neJBox

Gwde L1ne

G lntvl

Sync

I H-F

( L-R

( P-A

S-C-A

I off

Line

(Yes ( ON ( ON

Figure 6-3. Adding a parameter to the Basic tab.

Drag scroll box to bo:tom of scroll bar


Note: Changes made to the Basic tab apply to all Exam windows, not just the one currently in use.

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Scan Parameters 0 2. Click the Config button. The Config Setting window opens, as shown in

figure 6-4. Parameter check boxes that are selected and unavailable are the

Basic tab default parameters.

Conflg Setting Slice Plane -- -:l

D 2o13o D Sequence D Echo Time Mode D ShimMode D Oblique

FOV TR TE FA

D IR Pulse Thickness Interval Multi slice

D Multi Echo D Multi Acquisition D Mode D Stacks

Freq# Phase#

OK

..,

Figure 6-4. The Config Setting window.

3. C lick to select each parameter check box that you would like to add to the

Basic tab.

4. C lick OK to add the parameter(s) to the Basic tab and close the Config

Setting window.

To remove a parameter from the Basic tab, follow these steps:

I. C lick the All tab and drag the scroll box to the bottom of the scrol l bar to

reveal the Config button.

2. Click d1e Config button. The Config Setting window opens.

3. Click to clear each parameter check box you wish to remove. The check

mark will be removed and the parameter will not be displayed on the Basic

tab.

4. Click OK to remove the parameter(s) from the Basic tab and close the

Config Setting window.

6·5

0AS Is~ MRI System Reference Manual T'MhtJent MqHt

6-6

All Tab

The All tab, pa1tially shown in figure 6-5, displays all of the scan parameters

including the defaul.t parameters. Because there are so many sca11 parameters,

not all of them can be displayed at once in th is small space. Use the scroll bar to

locate the desired set of parameters, or c lick the Overview button (figure 6-5) to

open the ScanParam eterL ist window, which is shown in figure 6-7 and

described in the next section.

Slice Stack M0111ng

Positioning

SltceOrd A ( H-F ?] - ( L-R ~I -P-A

S-C-A -off ~r-Li-.ne--==--....,~J

- [Yes ~J Ellllllli[oN ~I Sync I ON ~I

Others

Rece1ver Cod

Figure 6-5. The All tab.


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Scan Parameters 0 Scan Parameters Area Buttons

The top of the Scan Parameters area (figure 6-6) contains the following buttons:

Reset

~~Overview

~ ~~ ~ Dynamic scan : time table . ~

... ...

Figure 6-6. The buttons at the top of the Scan Parameters area.

Reset - Resets a ll changed parameters to the previously-saved default values.

Ovea-view-Opens the ScanPara meterList window, as shown in figure 6-7.

All of the various parameters found under the All tab can be viewed and

changed in this convenient window, rather than scrolling through the categories

in the Scan Parameter area. Scanning can a lso be started and scan time can be

monitored in this window.

Figure 6-7. The ScanParameterList window.

Dy na mic scan time table-Opens the Dynamic scan time table window,

which provides a visual display of the execution plan for dynamic scans.

The buttons at the bottom of the Scan Parameters area are used during scanning

and are described in the "START, STOP, and Other Buttons" section in Chapter

5, "Exam Window Scanning Functions."

6-7

0AS Is~ MRI System Reference Manual TIN hUM llb,pet

Note: Refer to the "Launcher Buttons" section of Chapter 3, ''System Overview, " for a detailed description of menu customization for Launcher too/bar buttons.

Changing the Scan Parameters Area Display Location

The Scan Parameters area can be displayed on the right or left side of the Exam

window. To change the display location, use the following procedure:

I. On the System Settings Launcher button menu, click Window Setting (this

command appears if the System Settings Launcher button menu has been

customized). The Window Setting window opens as shown in figure 6-8.

2. Click the Exam Window tab on the Window Setting window.

3. Click the desired graphical representation for the Scan Parameters area

location. Additionally, the Protocol Properties area can be displayed either

graphically or by task name from this tab as well (figures 6-8 and 6-9).

4. Click OK to save your choices and close the Window Setting window. The

changes made take effect when the next Exam window is opened.

Figure 6-8. The Scan Parameters area on left of Exam window, graphical display of task list (Protocol Properties area) selected.

6-8 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

----------------------------------------6 Scan Parameters 0

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04tJ •• 012e •• OUI •• 01_ .... ..... .. ....... Ol'c21 •• OUI · · o.•t ..

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Figure 6-9. The Scan Parameters area on right of Exam window, task name display of task list {Protocol Properties area) selected.

Scan Parameters Descriptions

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The scan parameters are separated into the following sets of related parameters:

Sequence- ! ncludes parameters related to the scan to be performed, such as

slice plane, sequence type, and acquis ition mode.

Seq . Parameter- Includes parameters related to pulse sequences (TR, TE, and

NSA) and slices (thickness, interval, and number).

Advanced - Includes parameters related to add itional functions, such as phase

direction, presaturation, and bandwidth.

RADAR (RADial Acquisition Regime)- Includes parameters related to the

sampling of K-space in a radial pattern.

Saturation- Includes parameters related to the suppression of specific s ignals,

such as fat, water, and silicone.

6·9


Definition: 30 MRA refers to threedimensional magnetic resonance angiography. A slab refers to a collection of slices to be excited with a single excitation pulse, used in 30 acquisitions.

6. 10

T2WPrep (optionai)-A prepulse that enhances the T2 contrast of the imaging

target. When T2WPrep is appl ied to the BASG sequence, tissue contrast

improves but the SNR drops slightly.

MTC (Magnetization Transfer Contrast) - Includes parameters used to change

the contrast of images by moving magnetization from bound protons to free

protons.

VENC (Velocity ENCoding) - Includes parameters related to the use of phase

information to determine the rate and direction of blood flow.

SSP (Sloped Slab Profile) - lncludes parameters related to a sloped slab used to

suppress blood flow saturation in 3D MRA.

MPG (Motion Probing Gradient)- lnc ludes parameters related to scann ing

with the application of a gradient magnetic field to emphasize proton diffusion.

This is used with Diffusion Weighted Imaging (DWI).

Scan Control- Includes parameters related to the tim ing of contrast-enhanced

scans in various scan modes, such as wait t imes, delays, and contrast agents.

RAPID (Rapid Acquisition through a Parallel Imaging Design)- Includes

parameters related to the reduction of phase encode steps, which reduces scan

time.

Gating- Includes parameters used with ECG-, pulse-, and respiratory-gated

scans.

NAVI (NAVIgator Echo) - lncludes parameters related to Nav igator

acquisitions, which are used to reduce a1tifacts produced in a scan region, such

as the heart, where breathing can change the scan position.

PAPE (PA1tial Phase Encode)- Includes parameters related to PAPE, which

improves temporal resolution whi le maintaining image spatial resolution.

F ilter/PostProcessing-Includes parameters related to improving an image's

visual characteristics, as well as other post-processing selections.

Positioning- Includes parameters related to scan position, such as slice order

and plane order.

Others - Includes parameters fo r receiver coils and morning QA functions.

You can change parameter values by selecting from a list of options or by

clicking the up or down arrows (to change a numerical value in a box). You can

also change numerical values by highlighting the value in the box, typing the

new value, and then pressing the ENTER key. Parameters that have a grayed

out appearance are unavailable; th is occurrence depends on the combination

of parameters that have been selected. The Reset button at the top of the Scan

Parameters area resets all parameters to their previously saved default values.

The parameters are described in the remainder of this chapter.


Note: The values that can be set may be limited by the Sequence that is selected and related scan parameters.

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Scan Parameters 0 Sequence

The Sequence section of the ScanParameterList window (figure 6-1 0) contains

the fo llowing parameters:

Figure 6-10. The Sequence section of the ScanParameterList window.

Slice Plane - Provides the following options for the plane of the slices, as

shown in figure 6-11:

• AX- Axial

• SAG - Sagittal

• COR-Coronal

• SA-Sagittal and axial

• CA- Coronal and axial

• SC-Sagittal and coronal

• SCA- Sagittal, coronal, and axial

Figure 6-11 . Slice Plane options.

20 /30 - Provides the following options for the acquisition mode, as shown in

figure 6-12:

• I D - One-dimensional acqu isition. Used only in spectroscopy (lD is

automatically selected when Sequence is MRSSE).

• 2 0 - Two-dimensional acquisition. One slice is acquired per TR.

• 3D- Three-dimensional acquisition. ln 3D acquisitions, data encoded with

s lice pos ition information is collected, in addition to phase encoding and

frequency encoding. Multiple slices of image data are reconstructed us ing the

3D Fourier conversion. 30 acquisitions can produce images with varying s lice

thicknesses.

Figure 6-12. Acquisition mode options.

6. 11

0AS Is~ MRI System Reference Manual Th41hU ... tMqnet

Note: With 30 measurements, the SNR of images is lower at the top and bottom of each slab compared to the center area, making the images susceptible to artifact when using the BASG sequence. Therefore, position the region of interest so that it comes to the center of the slab and set the number of slice encode a little higher.

Note: If homogeneity of the magnetic field is poor, BASG is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. To minimize this effect, be sure to carry out volume shimming before performing the BASG scan.

Note: If the blood currents often run parallel to scanned slice or slab, if they wind drastically, or if their transit paths substantially differ between the right and left vessels, the MRA image should be carefully interpreted.

Note: Slice scan, slab scan, and pre-saturation pulses should be positioned to maximize the TOF effect when scanning with TOF MRA.

Note: Check original images concurrently while interpreting TOFMRA.

6. 12

Sequence- Provides the following options for pulse sequence, as shown in

figure 6- 13:

SE (Spin Echo)- Produces images with

proton density, Tl , and/or T2 weighting.

1§111§·+

• IR (Inversion Recovery) - Uses a 180° inverting radio

frequency (RF) pulse prior to the 90° excitation pulse to

acquire images with specific suppression .

• GE (Gradient Echo)- Uses a variable flip angle to

acquire images with T J or T2* contrast. The contrast

weighting is primarily determined by the flip angle.

FSE Scanogram SE IR GE SARGE RSSG TRSG BASG uTE FSE FJR pnmeFSE primeFJR isoFSE TOF PC SEEPI GEEPI OWEPI RSSG EPI Shim s.Map MRSSE T2RelaxMap

• SARGE (Steady State Acq uisition with Rewound

Gradient Echo)- Uses closely-spaced RF excitation pulses and shott TR (repetit ion ti me)

to create a steady-state signal. Th is sequence

produces images with Tl and T2 weighting.

• RSSG (RF Spoiled SARGE)- Uses c losely

Figure 6-13. Pulse Sequence options.

spaced RF excitation pulses with variable phase shifts. Th is sequence

produces images with Tl weighting.

• TRSG (Time Reversed SARGE)- Acquires the signal that was excited by the

prior RF pulse. This sequence produces images with heavy T2 weighting.

• BASG (Balanced SARGE) - Uses a short TR and acquires the signal under a

steady state, with slice-, phase-, and frequency-rewinder pulses. Th is sequence

produces images w itJ1 high signal-to-noise ratio (SN R), mixed Tim contrast,

and bright fluid.

• 11TE (micro Echo Time) - Used to detect tissue with an extremely short

transverse relaxation time (T2).

• FSE (Fast Spin Echo)- Uses multiple 180° RF pulses to more rapidly

produce images with proton density, Tl , and/or T2 weighting.

• FIR (Fast Inversion Recovery) - Uses a 180° inverting RF pulse prior to ilie

90° excitation pulse to acquire images with specific tissue suppressions.

• primeFSE-Similar to FSE, except that the user can enter T E and bandwidth

values, rather than values for the Inter E. Time (echo interval) and Echo Shift

parameters (these parameters are described later in this chapter).

• primeFI R- Simi Jar to Fl R, except that the user can enter T E and bandwidth

values, ratJ1er than Inter E. Time and Echo Shift parameter values.

• isoFSE (Isotropic Fast Spin Echo)-Optimized 30 FSE sequence that allows

an isotropic (or near isotropic) volume acquisition to be acquired, from which

sl ices can be reconstructed in any plane, thickness or interval desired.


Note: Image quality with EPI depends largely on the homogeneity of magnetic field. Volume shimming is required before running SE EPI to achieve good 1mage quality.

Note: In the S.Map sequence, scanning is carried out with the coil used for the main scan and the TR body coil.

The S-Map sequence is sensitive to patient movement. Keep the patient as still as possible while S-Map scanning to avoid artifact.

When scannmg the abdominal region, breath holds are required in an S·Map sequence when Mode is Normal.

When Wait mode is ON, the system pauses twice: after the prescan and in the middle of the S-Map sequence.

The wide area is to be scanned using the TR body coil. The scanogram should be used with the coil for the main scan. Therefore. make sure that the area which is not scanned through the scanogram does not cause artifact.

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Scan Parameters c;)

• TOF (Time of Flight)- Used to produce MRA using flow/inflow resu lts of

blood.

• PC (Phase Contrast)-Optional. Produces MR angiographs using phase

infonnation of blood flow.

• SE EPI (Spin Echo using Echo Planar Imaging) - Produces images with T l

or T2 weighting using very short acquisition t imes.

• G E EPI (Gradient Echo using EPI) - Produces images with T2* weighting

using ve1y short acquisition times.

• OW EPI (Diffusion Weighted EPI)- Produces diffusion-weighted images,

which depict the restriction of water molecule diffusion.

• RSSG EPI (RF Spoiled SARGE using EPI)- Optional. Produces images with

T I weighting using short acquisition times.

• Shim (Shimming)- Performs highly-precise corrections ofthe static

magnetic fie ld.

• S-Map (Sensitivity Map)- A sequence dedicated to 3D sensitivity map

acquisition. Acquires 30 sensitivity data to be used for shading correction

and RAPID measurement. Tn this sequence, images (acquired data) are not

displayed.

• MRSSE (MR Spectroscopy using Spin Echo)-Optional. Acquires molecular

dens ities of metaboliz ing substances in the human body.

• T2Relax.Map- Used to acquire multiple echo images at various T E times to

calculate the T2 relaxation times for every pixel in the image.

ADAGE

Multiple gradient echoes (typically three to six) are added together to form one

image for improved signal and contrast. With the ADAGE techn ique, multiple

echoes from a gradient echo (GE) sequence are combined to output an image

with improved SNR and/or CNR. Combine is automatically selected from Calc.

Image when Sequence is GE, SARGE, or RSSG and more than 3 echoes are

set to be acquired.

Target-Sets the type oftarget. Available only when Sequence is isoFSE.

• Tissue- A scan is performed with A ip angle of RF Refocus pulses modulated

for tissue.

• Fluid - A scan is performed with flip angle of RF Refocus pulses modulated

for fluid.

EchoTime Mode-Sets the range for the echo time (figure 6-14).

When Sequence is SE, choose one of the following:

• Nonnai - Use for normal scanning.

6. 13


Note: When scanning a patient with an orientation other than feet first supine, the output image has it's orientation rotated, but shimming is not affected.

Note: When scanning with the patient oriented feet first, the output images are in the reverse order of the slice order being set, but shimming is not affected.

6. 14

• Short TE-Use to acquire images with shorter TE than the Normal setting;

however, some parameters such as Dua l Slice and Multi Echo will be restricted.

When Sequence is FSE, FIR, p rimeFSE, or pr imeFIR, choose one of the

following:

• Shortl ET - Use to acquire images with short Inter E.Times, such as 12 and

below. In figure 6-14, ShortiET is selected.

• LongiET -Use to acquire this slice images with Inter E.Times of 12 and

above. This selection is used in FIR imaging.

• Optimized-Use to acquire the higher SNR and less aliasing image with same

Inter E.Time as ShortlET. O ptimized is available for 30 acquisition only.

Figure 6-14. The Echo Time Mode scan parameter.

Mode-Selects the sequence mode.

• Normal- Normal measurement is performed.

• YASC-ASL (optionai)-Creates an image oftluids, such as labeled blood

flow, using a spatial selection IR pulse. When VASC-ASL is selected, m Pulse is displayed and set to Selective.

• GEIR- Performs segment measurement using an IR pulse as a prepulse.

When GEIR is selected, IR P ulse is displayed and set to Segmented. As a

segment becomes larger, contrast may be slightly blurred. Water excitation is

available with GEIR.

• TIGRE- Performs a high-speed Tl contrast measurement in combination

with a fat suppression pulse for frequency selection. When TIGRE is

selected, Saturation is displayed and set to Segm ent FS.

• Nest-Collects signals using the receiver coil and Transmit/Receive Body

coil at nearly the same tin1e during the S-Map sequence. A sensitivity map

not easily affected by movement can be created for regions where movement,

such as breathing, is monitored.

• YASC-FSE-A Fast Spin Echo mode developed for non-contrast PYA

applications. VASC-FSE performs an acquisition in systole and another in

diastole. The difference between the two acquisitions is subtracted to obtain

blood vessel images of either arteries or veins.

Shim Mode- Provides options for the use of shimming results (figure 6-15).

• off-Does not use shimming results.

• Volume- Uses volume shimming resu lts. Shimming results are not used

when there are changes in a patient or coils.

• Auto Volume - When measurement conditions include shim measurements,

shimming is automatically performed during prescanning.


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Scan Parameters 0 • Regional - Performs regional shimming in a specific area designated by the

purple box on the positioning screen. Upon opening a scan task, the regional

shim box moves along with any movement of the slice group. However, once

the regional shim box is activated, the slice group and regional shim no longer

move together.

!It Caution

Volume

off Volume AWlVolume R onal

Figure 6-15. Shim Mode options.

If an error occurs during shimming, contact Hitachi service.

Additiona l Notes for the Mode pa ra meter :

The values that can be set may be limited by the selected Sequence and related

scan parameters.

Since GElR is 3D measurement, the SNR of images is lower at the top and

bottom of each slab compared to the center area . Therefore, position the region

of interest so that it comes to the center of the s lab and set the number of slice

encode a little higher.

Pre-saturation pulses may be used with the 3D GEIR sequence, however MTC

and FatSat pulses cannot be used.

Additiona l Notes for the Shim Mode parameter :

Estimated fie ld distributions are displayed after volume shimming. however they

are not displayed after regional shimming.

The vo lume of interest (VOl) must be within the region of volume shimming.

The results of shimming are canceled and become ineffective when the patient

name or receiver coi l is changed, when Shim Mode is off and any measurement

is carried out, or when Prescan is ON and any measurement is carried out.

When Shim Mode is set to anything other than Regional, the VOl is deleted.

The region of shimming, region of imaging, and the direction of phase encoding

should be identical.

The center of shimming shou ld be identical with the center of the magnetic field.

Additiona l Notes for the S-Map pa ra mete r:

The position and the scan parameters should be set in a way that prevents

aliasing artifact from occurring in the area selected for the main scan.

6. 15


Note: If performing a Black Blood scan with Multi Slice and Multi Acquisition= 1, adjacent slices are excited in 1 TR, so image quality can be degraded. Perform scans with the slice interval larger than the slice thickness of the Double IR Pulse and STIR Pulse or with Multi Acquisition ~ 2.

Note: The values that can be set may be limited by the selected Sequence and related scan parameters.

6. 16

Planes to be scanned wi ll vary depending on the anatomical region being

scanned. Therefore to avoid aliasing a1tifact, COR and SAG planes are

recommended because the direction of the body axis is the readout direction.

When setting FOY, it is recommended to set it 20 to 30 percent larger than the

one for the main scan.

Slab thickness shou ld be set accord ing to the size of the region to be scanned,

adjusting S. Encoding.

SNR can be too low when FOY is smal l. Therefore, it is necessary to ensure

adequate SNR by setting the appropriate NSA.

Oblique-Provides methods for determ ining whether or not scans can be

performed, based on the angulation of slices. Options are (figure 6-16):

• Full -Allows fu ll angulation of slices, but will require protocol changes if a

steep angle is used.

• Limited-Allows a limited degree of angulation, so that the protocol

parameters selected for the acquisition can be used.

Seq. Parameter

r+ii ~~L=--im-=itec:...d --~ Full Limited

Figure 6-16. Oblique methods.

Figure 6-17 shows the Seq. Parameter section of the ScanParameterList window:

Figure 6-17. The Seq. Parameter section of the ScanParameterList window.


Note: TE2. TE3. and TE4 are used only for multiple echoes.

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Scan Parameters 0 FOV-Indicates the s ize in millimeters ofthe visual field to be reconstructed

fo llowing the scan.

FOV2-Sets the size ( in millimeters) of the longitudinal visual ·field

reconstructed fol lowing the scan. The c rosswise visual field is set by the FOV

parameter. Used on ly in spectroscopy (FOV2 is displayed when Sequence is

MRSSE).

TR- lndicates the repetition time in milliseconds of the pulse sequence. During

gated scans, TR values are automatically set when Trigger is selected for the

Gate or Resp mode.

TE- Indicates the echo period in milliseconds for the first echo. This value is

automatically set when the following are selected from the Sequence list:

• BASG • FSE

• FIR • Shim

TE2- Ind icates the echo period for the second echo. This setting is displayed

when the selected Sequence is SE, GE, SARGE, RSSG, or FSE, and the

Multi Echo parameter is set to 2 or more. (When FSE is selected, TE2 is

automatically set based on other parameters, such as E.Factor .)

TE3- Indicates the echo time for the third echo. This setting is displayed when

the selected Sequence is SE and the M ulti Echo parameter is set to 3 or more.

TE4- Indicates the echo time for the fourth echo. This setting is displayed

when the selected Sequence is SE and the M ulti Echo parameter is set to 4 or

more.

Figure 6-18 shows settings fo r the TE through TE4 parameters.

Figure 6-18. Example settings for TE, TE2, TE3, and TE4 boxes.

Delta TE - Indicates the time between echoes. This parameter is available

when Sequence is SARGE (20 ), GE, or RSSG and the Multi Echo parameter

is greater than 2.

Last TE - Indicates the echo time for the last echo. This parameter is available

when Sequence is SARGE (20), GE, or RSSG and the Multi Echo parameter

is greater than 2.

6. 17

0AS Is~ MRI System Reference Manual nt.htletllqnet

Note: TEequiv is the echo time needed in an isoFSE scan to obtain the same contrast as TE in a conventional FSE scan. However the exact same contrast cannot be obtained due to T1 decay contamination.

Note: When Excitation Pulse is Non· selective, aliasing artifact may appear in the slice direction. Make sure the imaging area covers the entire imaging object in the slice direction, or apply presaturation pulses to both edges of a slab to suppress aliasing artifacts.

Note: AdditionaiiR pulse options (Double, Triple) are associated with the CardioSuite, which is a purchasable option.

Note: Tl and FatSat cannot be combined simultaneously in the STIR type fat suppression.

Note: Optimum Tl of the Black Blood scan varies depending on orientation of the slice plane. When reduction of blood signal is small, modify Tl and retry the scan.

6. 18

TEequiv- Represents the echo time needed in an isoFSE scan to obtain the

same T2 contrast as a conventional FSE scan. This parameter is ava ilable when

Sequence is isoFSE. Set TEequiv equal to the TE setting in a conventional

FSE scan to obtain t he same contrast.

Excita tion Pulse- This parameter is displayed when Sequence is isoFSE and

is fixed to Non-selective.

FA (Flip Angle) - The angle of excitation to which the net magnetization is

tipped relative to the main magnetic field.

IR Pulse (Inversion Recovery Pulse) - Indicates if an IR pulse w ill be used for

tissue saturation. This is primarily used with Cardiac scanning.

This parameter can be selected when Sequence is SE, BASG, FSE, DW EPI,

SE EPI, or GE EPI.

The following options are available, as shown in figure 6-19:

• Off- Does not perform tissue saturation; this is the recommended setting.

• Single- Performs tissue saturation with designated Tl.

• Double- Executes blood saturation via Double-1 R. When Double is selected,

TI becomes available.

• Triple (optional)-Executes fat saturation via STlR pulse and blood saturation

via Double-IR. When Triple is selected, TI and Tl2 become available.

• Segmented- Performs segment measurement using the STIR pulse as a

fat suppression prepulse. Segmented is selectable with 3D RSSG (GEIR

imaging). When Segmented is selected, TI and Segment become available.

• Se lective-Applies a spatial selection IR pu lse. Selective is selectable with

VASC-ASL imaging. When Selective is selected, TI and Segment become

available.

off

off L s ingle

Figure 6-19. Example IR Pulse options.

TI-Sets the Inversion Time, wh ich is the time period between the initial 180°

inversion pulse and the 90° excitation pulse in an IR pulse sequence. This box

is available when the selected Sequence is IR or FIR, the ECG Gate Mode is

Delayed or MyoPer, or when IR Pulse is Single. The measurement of the Tl

wil l be calcu lated as follows:

• When Sequence is IR or FIR, or IR P ulse is Single, TI is the interval

between the STIR pulse and the excitation pulse.

• When Gate Mode is Delayed or MyoPer , Tl is the interval between the STIR

pu lse and the zero encode excitation pulse.

Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Note: For a FLAIR sequence of the brain, the IR Thk.Ratio should be set to 4.0.

Note: The gap between slices can be calculated as: Interval- Thickness = Gap

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Scan Parameters 0 • When IR Pulse is Double or Triple, T l is the interval between the Double-lR

pulse and the excitation pulse.

• When IR Pulse is Segmented or Selective, TI is the e lapsed time from the

STTR pulse to the zero encoded excitation pulse.

TU- Sets the interval (in milliseconds) from the STIR pulse to the excitation

pulse. Specify a TU setting when IR P ulse is Tr·iple.

Segment- Sets the number of echoes to be acquired after application of one

STIR pulse. Specify a Segment setting when IR P ulse is Triple.

lRFA- Sets the excitation angle (in degrees) of the IR Pulse spin. Specify an

IRFA setting when Gate Mode is MyoPer .

TR Thk.Ra tio- lndicates the s lice thickness selection of the initial 180° pulse

relative to the slice d1ickness of ilie main scan. The normal setting for this

parameter is 1.3. You can use this parameter when Sequence is FIR or Prime

FIR, or when Sequence is FSE or P rime FSE; and IR P ulse is Single. In figure

6-20, the Sequence is FIR and theIR Tbk.Ratio is set to a value of 1.3.

Figure 6-20. IR Thk. Ratio example.

BBJR Thk.Ratio - Sets the s lice thickness ratio of the Double-lR Pulse for the

main scan sl ice thickness. Specify a BBIR T hk.Ratio when Sequence is FSE

or primeFSE and TR P ulse is Double or Triple.

Thickness - Indicates the s lice thickness (in mill imeters). When Thickness is

changed, Interval automatically updates to maintain the gap between slices.

Interval- Indicates d1e spacing (in millimeters) between slices, measured

from the center of one s lice to the center of the next slice. The interval in 20 multi-slice acquisitions is between parallel slices; the interval in 30 multi-slab

acquisitions is between parallel slabs. Interval automatically updates when

Thickness is changed, thus maintaining the gap between slices.

Multi slice- Indicates the number of slices to be acquired during one scan.

This setting is displayed for 20 acquis itions only.

6. 19


6 • .20

Multi Echo- Indicates the number of echoes to be collected in one scan. As

the Multi Echo value is increased, add itional numbered TE boxes (TE2, TE3,

and so on) become available on the ScanPar·ameterList window. Multi Echo is

available when Sequence is SE, FSE, GE, SARGE, or RSSG. In figure 6-21,

Sequence is GE and Multi Echo is set to a value of2.

Figure 6-21. Multi Echo example.

Multi slab- Available for 3D acquisitions only. Indicates the number of slice

slabs to be acquired in one scan. In figure 6-22, Sequence is TOF and Multi

slab is set to a value of 4.

Q\1!@119 TOF @id4@ r~-o-lum-e-~~.~1

&pi- Umited Seq. Parameter

'" 1220 1· 1·] i· 22.0 1· 1· i 8.7 1-· .. II 25 I . .. I !!Aid 1.0 I·· .. ,.

~ =t:t1 !il.!.ii!&i '*·'·9"' 1~0 1· ..

. . .

Ufi•M· Figure 6-22. Multi slab example.

Recon P itch - Allows the desired thickness of the reconstructed slices to be

input. Recon P itch can be a value no less than one-half of the acquired slice

thickness (the Thickness parameter).

Recon P itch will automatically adjust to maintain the ratio between Thickness

and Recon Pitch values. Additionally, Recon Pitch automatically reverts to

upper and lower limits when an entered value exceeds either limit (the upper

limit is T hickness, and the lower limit is one-halfofThickness).


QS4-86717v3

Scan Parameters 0 Recon Slice- The number of slices to be reconstructed for the acquis ition.

Slice Rejectl % 1- lndicates a percentage of slices at the slab ends that wi ll not

be reconstructed. This is useful for 3D acquisitions that may have decreased

SNR at the s lab ends. One half of the value that is se lected is rejected trom each

end of the s lab (for example, if20 percent is se lected, I 0 percent of the tota l slab

will be rejected from each end).

Overlapi% ]- Jndicates a percentage amount of slab overlap, wh ich is used

to improve the s ignal continuity between slab intervals in 3D TOF multi-slab

acquis itions. The Multi slab parameter must have a value greater than I.

Figure 6-23 shows the Slice#, Slice Rej ectl% 1, and Overlap[% ] parameters set

for a 3D TOF series.

Figure 6-23. Slice#, Slice Reject[%], and Overlap[%] example.

Multi Acquisition - Indicates the number of acquis itions. This setting is

available when the Mode parameter is Interleaved or Sequentia l.

When Mode is Stack, the value in M ulti Acquisition is unavailable, but will be

the same as the value set in the Stacks box, as shown in figure 6-24.

~!''!'!"!'!'!! 2 4&G ~~==ck===r~ • [ 1· !· .

Figure 6-24. Multi Acquisition example.

When the Mode parameter is SingleSlicc, M ulti Acquisition is unavailable.

However, the d isplayed number of acqu isitions will be the same as the number

set in Multi slice for 20 acquisitions, or the number set in Multi slab for 3D

acqu isitions, as shown in figure 6-25.

Multi slab Multi slice

Figure 6-25. SingleS/ice Mode examples for 20 and 30 acquisitions.

6. 21


6 . .2.2

The following examples explain how the M ulti Acquisition, Mode, and

M ulti slice parameters can be set in various combinations to acquire images

differently.

Example 1: M ulti slice is 6, Mode is Interleaved, and M ulti Acquisition is 2.

The value of2 in the M ulti Acquisition box divides the sl ices into two groups

of three slices each. The I nterleaved mode acquires the top and bottom slices,

then the middle slice in each group, all with the same TR. For these parameter

settings, the first acquisition would be slices I and 3, and then slice 2; the second

acquisition would be slices 4 and 6, and then slice 5.

Example 2: M ulti Slice is 6, Mode is Sequentia l, and M ulti Acquis ition is 2.

The value of2 in the M ulti Acquisition box divides the sl ices into two groups

ofthree slices each. The Sequential mode acquires the slices in numerical order,

one group at a time, all with the same TR. For these settings, the first acquisition

would be slices 1, 2, and 3; the second acquisition would be slices 4, 5, and 6.

Example 3: M ulti Slice is 6, Stacks is 2, and Mode is Stack.

Stack mode can be used when slices are set at different angles, such as in axial

lumbar imaging. Stack mode acquires the slices in the first stack, then the slices

in the second stack, all with the same TR. For these parameter settings, the

setting of the Stacks value at 2 with Mode set to Stack causes the M ulti Slice

box to be updated and display a total of 12 slices (6 slices x 2 stacks= 12 total

slices).

Example 4: M ulti Slice is 6 and Mode is SingleSlice.

SingleSlice mode is used to acquire one slice perTR, as in 20 TOF sequences.

For these parameter settings, each slice (of the 6 total slices) will be acquired

individually.

Mode-Specifies the acquisition mode. The options, as shown in figure 6-26,

are:

• Interleaved -Slices are acquired in an odd- and even-numbered fashion (such

as slice numbers I , 3, 5, 7, then slice numbers 2, 4, 6, 8).

• Sequential -Slices are acqu ired in order of slice number (such as 1, 2, 3, 4).

• Stack-Slices are acquired for each angle.

• SingleSiice- Each slice is acquired as a separate acquisition, with the

selected parameters (one slice per TR).

- Interleaved Interleaved Sequenbal Stack SingleSiice

Figure 6-26. Mode options.


QS4-86717v3

Scan Parameters 0 Slice#- Indicates the number of slices to be reconstructed for 3D acquisitions

(figure 6-27).

Figure 6-27. Slice# example.

Stacks- Indicates the number of groups when acqu iring multiple groups with

different angles.

Freq#- lndicates rhe number of sampl ing steps in the frequency axis, as shown

in figure 6-28. Hold the mouse pointer over the Freq# box to view the range that

is available.

IM §s6 ::J .. ' ..

Figure 6-28. The Freq# parameter.

Phase# - Indicates the number of sampling steps in the phase axis, as shown in

figure 6-29. Hold the mouse pointer over the P hase# box to view the range that

is available.

Figure 6-29. The Phase# parameter.

Freq Point- Sets the frequency resolution. Used only in spectroscopy (Freq

Point is displayed when Sequence is MRSSE).

ReconMatrix - Indicates the reconstruction matrix for the image. A value

larger than the frequency encoding value (from the Freq# box) and/or the phase

encoding value (from the P hase# box) can be set, in increments of32 (from 128

to 512).

6· 23


Note: A value must be entered in the APR[%} box to make Half Scan available.

NSA (Number of Signals Averaged)- Indicates the number of s ignal

acquisitions to be averaged. Increasing NSA will improve the SNR ofthe image,

but also increases scan time. Doubling NSA doubles the scan time, but only

increases the SNR by approximate ly 40% because increased noise accompanies

the increased number of signals.

APR[%] (Asymmetric Projection Rate)- lndicates a percentage ofK-space

that w ill not be acquired in the phase encoding d irection. K-space as a whole is

I 00%; the APR[%J parameter can be set to values between 0% and 45% and

can be changed by 5% intervals. This parameter is used in conjunction w ith

Half Scan.

The position of the non acquired K-space region changes for each of the echo

layouts, as shown in figure 6-30. In addition, processing of the non acquired

region c hanges according to the setting of the Half Scan parameter (described

next in this section).

Frequency Frequency Frequency Frequency

PhaseW 4 PhaseW 1 PhaseF 1 Phase~ 5

6-24

3 2 2 4 2 3 3 3 1 4 2 1 4 1

APR APR APR APR

Centnc Ant1 Centnc Sequential ADA

Slice

Phaser, APR

Slice

Phaser, 1 3 2

1 3 2 4 6 5

4 6 5 7 9 8

8 7 9 11 10 12

11 10 12 APR

PEAKS RPEAKS

Figure 6·30. K-space filling for various echo layouts.

Half Scan -Enables image acquisition in a sha tter time by limiting the

sampling of the phase axis inK-space. Spatial resolution is maintained, but

SNR is reduced. Images are created using the acquired data, combined with the

interpo lated data used to fi II the non acquired region of K-space. Acquisitions

are performed in accordance with the val ues set for the phase direction in the

APR[%] parameter. The options, as shown in figure 6-3 l , are:

Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Note: OW/ is sensitive to movement smce the MPG pulse is applied. In multi-shot measurements, use gated scanning with the scan region immobilized to reduce motion artifacts.

QS4-86717v3

Scan Parameters 0 • off-Does not use Half Scan.

• ON-Uses Half Scan.

"'""' off ·~ off ON

Figure 6-31. K-space filling for various echo layouts.

The following examples explain how the APR(%} and Half Scan parameters

function together:

Example 1: APR(%] set at 25 percent and Half Scan is ON (figure 6-32)

This is the equivalent of~ Scan. Data is acquired from three-foUJths (~)or 75% of K-space; one-foUJth ( '.!.!)or 25% of K-space is interpolated.

:1*'1'111[5 :J .. €MIA*'' ( ON ·I

Figure 6-32. The equivalent of three-quarter scan.

Example 2: APR(%] set at 45 percent and Half Scan is ON (figure 6-33)

This is the equivalent of 1/ 2 Scan. Data is acquired from 55% of K-space; 45% of

K-space is interpolated.

1'1''1'1111~~45=-~~---IMIP*ii I ON ·I

Figure 6-33. The equivalent of one-half scan.

Shot Num.- Indicates the number of RF excitations, or TR periods, needed to

acquire data, as shown in figure 6-34. A lower shot number results in a faster

scan time. The shot number can be calculated using the fo llowing equation:

Phase# "'" E. Factor = Shot Num.

Figure 6-34. Shot Num. example.

Shot Num. is available when Sequence is SE EPl, DW EPL or GE EPI. Hold

the mouse pointer over the Shot Num. list to display the range of settings.

6· 25


Note: When Echo A/foe. is Centric and if# RF Prep is extremely small, good images cannot be obtained since data acquisition starts while steady state has not yet been reached.

6 • .26

Shot Num. is displayed, but unavai lable, in the following cases:

• Sequence is FSE, FIR, RSSG or EPI.

• Sequence is Prime FSE or Prime FIR, and Echo Alloc. is Centric.

E.Factor - The number of echoes to be used to create a s ingle image. An

acceleration rate is obtained based on the number of echoes used. However, the

more the echo is delayed, the weaker the signa l strength becomes due to the

decay of signal amplitude (T2 or T2*). As the E.Factor increases, the SNR and

resolution decrease.

E.Factor is avai lable when Sequence is FSE, FIR, or RSSG EPJ.

E.Factor is displayed but unavailable in the following cases:

• Sequence is SE EPI, DW EPI, or GE EPI.

OR

• Sequence is P rime FSE or Prime FIR, and Echo Alloc. is ADA.

Inter E. Time- The time between echoes. Inter E.Time is displayed when

Sequence is any of the following: FSE, FIR, SE EPI, DW EPI, GE EPI, or

RSSG EPI. When Sequence is FSE or FIR, an effective TE is calcu lated by

the system. This TE calculation inc ludes the E.Factor, Echo Alloc., Echo Shift,

and Inter E. Time parameters to determine image weighting.

Echo Shift-Adjusts image contrast by changing the location of the effective

TE in K-space, without changing the number of echoes. An Echo Shift of 1

changes the effective TE by an increment equa l to the value displayed in Inter

E. Time. Echo Shift is available when Sequence is FSE, FIR, SE EPI, GE

EPI, RSSG EPI, or DW EPI. Echo Shift is displayed but unavailable when

Sequence is Prime FSE or Prime FIR.

Echo Shift2 - AIIows Echo Shift to be selected for the second echo. Echo

Shift2 is available when Sequence is Prime FSE or Prime FIR.

Echo Alloc. - AIIows the echo layout method to be selected. A pa11ial listing of

options is shown in figure 6-35.

The options are:

• Sequential

• Centric

• AntiCentric

Centric Ant1Centnc

Figure 6-35. Echo A/foe. options.


QS4-86717v3

Scan Parameters 0 • ADA (Asymmetric Data Allocation)

• PEAKS (optional)

• RPEAKS (optional)

• TPEA KS (optional)

• Seq-Seq (optional)

• Cent-Cent (optional)

• Cent-Seq (optional)

• Cir-Raster (optional)

• C ir-Centric (optional)

• Cir-Anti Centric (optional)

All of these Echo Alloc. commands are available when Sequence is isoFSE.

Sequential, Centric, AntiCentric, and ADA are frequency/ phase 2D echo

layouts (figure 6-36).

The non acquired region will be determined in combination with the value set in

the APR[% J parameter. Processing of the non acquired region will change

according to the Half Scan parameter value. For example, Half Scan is

automatically set when ADA is selected.

Frequency

PhasefC 4

Frequency

Phaseff 1

Frequency

Phase.fe 1

Frequency

PhaseW 8 3 2 2 7 2 3 3 6 1 4 4 5 1 4 5 4 2 3 6 3 3 2 7 2 4 1 8 1

Centnc Ant1 Centnc Sequential ADA

Figure 6-36. Frequency/phase 20 echo layouts.

PEAKS and RPEAKS are optional phase/slice 2D echo layouts (figure 6-37),

wh ich are used during 3D contrast-enhanced MRA. Acquisition is started

in the direction of the epicenter of K-space. When the epicenter is acquired,

acqu isition is performed receding from the epicenter. When the APR[%]

parameter is 0, there is no difference between PEAKS a nd RPEAKS. However,

when the APR[% ] parameter is set to anything above 0, the non acquisition

region differs. Processing of the non acquired region changes according to the

Half Scan parameter value.

6· 27


6 . .28

Slice

Phaser,

1

4

8

11

APR 3 2

6 5

7 9

10 12

PEAKS

Slice

Phaser, 1

4

7

11

3 2

6 5

9 8

10 12

APR

RPEAKS

Figure 6-37. PEAKS and RPEAKS optional phase/slice 20 echo layouts.

TPEAKS is an optional phase/slice 2D echo layout, which is used during 3D contrast-enhanced MRA in the same way as PEAKS and RPEAKS. The

distance between the center of the phase/slice plane and each acquisition point is

used as the standard to set the acquisition order. As shown in figure 6-38,

acquisition is performed from the center of the phase/slice plane, with the time

that K-space data collection begins as the peak of the contrast agent density.

Acquisition is then performed on the side closest to the center.

Slice

Phaser,--------------~

4

Figure 6-38. TPEAKS optional phase/slice 20 echo layout.

Seq-Seq is selectable on ly with 3D RSSG (GEJR imaging). The measurement

order of both phase encode and slice encode is Sequential. With Seq-Seq, temporal efficiency is better than Cent-Seq and Cent-Cent since data is

acquired before the Tl time.

Cent-Cent is used with 30 RSSG (GEIR) or TIGRE imaging. Echo allocation

for both the phase and slice encode directions is Centric. When using this echo

allocation, #RF Prep must be increased. However, increasing #RF Prep results

in the reduction of fat suppression by the FatSat pulse.


QS4-86717v3

Scan Parameters 0 Cent-Seq is an echo allocation option for TIGRE imaging. Echo allocation for

the phase encode direction is Centric, while the echo al location for the sl ice

encode direction is Sequentia l. Centric scans from the center of K-space toward

the peripheral region, while Sequential scans from the peripheral region toward

the center, sequentially.

Figure 6-39 illustrates the Seq-Seq, Cent-Cent, and Cent-Seq echo allocation

options.

I

I

1

2

3

4

5

Seq-Seq

Q) '0

8 c: w

~ t Q.

4 3

r---1 2

Slice Encode

I I

3 2

1

1 2

3

Cent-Seq

Q)

8 c: w

~ t Q.

l

-3 2

1

I

3 2

1

1

2

3

Cent-Cent

4

Slice Encode

---'1 1

2 3

Slice Encode

Figure 6-39. Seq-Seq, Cent-Cent, and Cent-Seq echo allocation options.

Cir-Raster is available only when Sequence is isoFSE. With Cir-Raste r,

the echo train is a llocated along the phase encode axis (ky). Data is acqu ired

sequentially from the edge ofk-space. This echo allocation is su itable for T2W

imaging.

Cir-Centric is available only when Sequence is isoFSE. With Cir-Centric, the

echo train is allocated a long the radial axis (kr). Data is acquired from the center

to the edge ofk-space. This echo allocation is suitable for PDW (proton dens ity

weighting) imaging.

Cir-AntiCentric is available only when Sequence is isoFSE. With Cir

AntiCentric, the echo train is a llocated along the radial axis (kr). Data is

acquired from the edge to the center ofk-space. This echo allocation is suitable

for heavy T2W imaging.

6-29


6-30

Figure 6-40 illustrates the Cir-Raster, Cir-Centric, and Cir-AntiCentric echo

allocation options.

2 3 4

Cir-Raster

Cir-Centric Cir -AntiCentric

Figure 6-40. Cir·Raster, Cir-Centric, and Cir·AntiCentric echo allocation ophons.

Echo Skip - Allows echoes with different polarity to be skipped. Skipping

echoes does not affect the number of echoes to be obtained . Echo Skip is

available for display only and is fixed at ON.

3D Acq. Mode-Selects the measurement fie ld of the ky-kz plane (K-space), as

shown in figure 6-41.

II Circular ~

Normal 1 Circular

Figure 6-41. 3D Acq. Mode options.


QS4-86717v3

Scan Parameters 0 • Normal - Measures the rectangular field in the ky-kz plane (figure 6-42), when

Cent-Cent or Cent-Seq echo allocations are used with TIGRE.

kz -t--1!-1~----..-...----.

r~~

----. ky Normal

Figure 6-42. Normal 3D Acq. Mode K-space measurement field concept.

• Circular - Measures the inscribed circle in the rectangular field of the ky-kz

plane (figure 6-43). Circular is used to decrease scan time or increase

resolution while maintaining scan time. C ircula r is available when Sequence

is GE, SG, R SSG, or VASC-ASL.

kz

i ....... J...- r- t--...

/ '\.

" / r- vv

... ky Circular

Figure 6-43. Circular 3D Acq. Mode K-space measurement field concept.

C hemical Shift- Indicates the optimum polarity of the phase-encoding

grad ient magnetic fie ld. The polarity can be changed to minimize the effects

of image dist01tion. Chemical Shift is available when Sequence is SE EPI,

GE E Pl , DW EPI, or RSSG EPI, and Echo Alloc. is Sequentia l or ADA. As

shown in figure 6-44, the options are:

• Normal- Normal polarity of the phase encoding grad ient magnetic field.

• Reverse- Reverse po larity of the phase encoding gradient magnetic field.

6 ;;we ~Normal Normal Reverse

Figure 6-44. Chemical Shift options.

6. 31


Note: The values that can be set may be limited by the selected Sequence and related scan parameters.

6-32

DE P ulse (Driven Equil ibrium Pulse)-An additional pulse that can be used

following signal coElection to possibly decrease TR and consequently decrease

scan time, while maintaining T2 contrast. A DE pu~se converges. the transverse

relaxation of the magnetization and forces it to longitudinal relaxation. DE

P ulse is available when Sequence is FSE, FIR, Prime FSE, or Prime FIR. The

following options are available, as shown in figure 6-45:

• off- Does not add the DE pulse.

• ON -Adds the DE pulse.

Figure 6-45. DE Pulse options.

M ult i Voxel-lndicates the number ofvoxels acquired in one scan. Used only

in spectroscopy (Multi Voxel is d isplayed only when Sequence is MRSSE).

Advanced

The Advanced section of the ScanParameterList window (figure 6-46)

contains many additional parameters that can be used during image acquisitions.

Figure 6-46. The Advanced section of the ScanParameterList window.

P resat (Presaturation)-AIIows presaturation pulses to be applied that can

reduce artifacts by controlling the signals from movable areas (such as blood

flow signal or the abdominal wall).

Pres.aturation is a technique that uses repeated RF excitation of structures

adjacent to the anatomy of interest to reduce or eliminate the phase effect

artifacts that can be caused by flowing nucle i in these adjacent structures. The

signal from the flowing nuclei is saturated, and therefore nullified, upon entering

the FOV.


Note: Refer to chapter 3-2 of the Oasis How-to Manual for complete presaturation pulse details.

QS4-86717v3

Scan Parameters 0 You can set a maximum of eight presats, with the Presat box displaying the total

number. The first two presats are automatically set as parallel regions adjacent to

the slice surface. These two regions prevent the blood flow s ignal from flowing

into the sl ice plane to be scanned. Presats are displayed in blue. The mouse can

be used to rotate, move, or magnify the pre sat regions.

Normal-Applies presats for each slice acquisition. Figure 6-46a shows a

normal presat.

Figure 6-46a. A Normal presat.

6· 33

0AS Is~ MRI System Reference Manual nt.hU•tMqJMt

6-34

Walking-Allows the position of the presat region to move, or "walk," for

each slice acquired (or each slab in 3D). In this manner, the presat always

remains adjacent to the slice. This is used when acquiring blood vessel images

in angiography.

Walking is avai lable when Sequence is TOF or BASG. If a walki ng presat is

selected, it is the first presat displayed in the viewp01t, and it is displayed in

green. Only one walking presat is available. The mouse can be used to rotate,

move, or magnify the wa lking presat region. The number displayed in the

Presat box is the total number of presats, including the walking presat. Figure

6-47 shows a walking presat.

Figure 6-47. A Walking presat.

Intermittent- Applies presats for each repetition time (which is the value set

in the TR parameter); normally, the presat is applied for each slice acquisition.

Intermittent presats will a llow you to increase the number of slices; however as

the TR increases, the effectiveness of the presat decreases.

The maximum number of intermittent presats available is 2. The intermittent

presats will be displayed in light blue. The mouse can be used to rotate, move,

or magnify the intermittent presats. The number displayed in the Presat box is

the total number ofpresats, inc luding the interm ittent presats.

Figures 6-48 and 6-49 show the Intermittent parameter with values of I and 2

respectively.


----------------------------------------6 Scan Parameters 0

QS4-86717v3

Figure 6-48. lntennlttent set to 1.

Figure 6-49. lntennittent set to 2.

Segment- May improve presat results. Available when Sequence is BASG, and

one or more presats have been selected. Figure 6-50 shows Segment set to I.

Figure 6-50. The Segment parameter.

6·35

0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet

6-36

Dual Slice-Acquires twice as many images w ith the same scan parameters

by acquiring two parallel slices at a time. The number that can be entered in the

Multi slice box is doubled. An even number is required in the NSA parameter

box. Dual Slice is available when Sequence is SE, IR, or GE. The options for

Dual Slice, as shown in figure 6-51 , are:

• off- Does not use dual slice.

• ON-Uses dual slice.

Figure 6-51. Dual Slice options.

Rephase (Flow Compensation) - Used to suppress flow artifacts, such as blood

and CSF. The options, as shown in figure 6-52, include:

• off- No rephase.

• Sl ice- Rephase is applied along the slice direction only.

• Freq-Rephase is applied along the frequency direction only.

• Slice_Freq -Rephase is applied along the s lice and frequency directions.

lUFF off

off Slice Freq Slice Freq

Figure 6-52. Rephase options.

The available Rephase options depend on the selected Sequence. For multi

echo acquisit ions, the presence or absence ofRephase for each echo is as

follows:

Sequence l Echo 2 Echoes

SE No rephase Rephase

GE Rephase Rephase

SARGE Rephase Rephase

RSSG Rephase Rephase

FSE Rephase Rephase

primeFSE Rephase Rephase

F low R eduction-Available when Sequence is SE, the RADAR parameter

is ON, and the Rephase parameter is off. Flow Reduction allows the use of a

dephase pulse to dephase the blood flowing through a sl ice, useful when black

blood imaging the carotid arteries. The options include:


Note: As the frequency bandwidth of the reception signal is reduced, the SNR of the image increases. However. chemical shift artifacts (a phenomena where the difference in the resonance frequencies between water and fat diverge on the image) will become noticeable.

QS4-86717v3

Scan Parameters 0 • off-No dephase.

• Slice - Oephase is applied a long the sl ice direction on ly.

Level-Sets the strength of the flow dephasing gradient magnetic field pulse. If

Level is changed, the suppression effects of artifacts due to blood flow change.

Level options include:

• Light- T he flow dephasing gradient magnetic fie ld pulse strength is light.

• Medium- The flow dephasing gradient magnetic field pulse strength is

medium.

• Heavy- The flow dephasing gradient magnetic field pulse strength is heavy.

Bandwid th[k llz] - lndicates the frequency bandwidth (kHz) of the reception

signal, as shown in figure 6-53. Since noise is distributed evenly across all

frequency bandwidths, reducing the frequency bandwidth value reduces noise

and improves the SNR; however, chemical shift artifacts may become more

noticeable.

Figure 6-53. The Bandwidth[kHz] parameter.

Bandwid th2[kHz] - lndicates the frequency bandwidth (kHz) of the reception

signal for the second and subsequent echoes during a multi-echo acquisition.

This parameter is available when Sequence is SE, GE, SARGE, or RSSG, and

M ulti Echo (under Seq. Parameter) is 2 or more.

In figure 6-54, M ulti Echo is set to 2, and Bandwidth2[kHz] is set to I 0.

04171 El:ll Ell

Figure 6-54. A Bandwidth2[kHz] parameter example.

6-37

0AS Is~ MRI System Reference Manual nt.htletllqnet

Note: The larger the AMI[%] value, the shorter the TE. However, if Half Echo is off, there may be a degradation of spatial resolution.

Note: Half Echo uses frequency direction data in the same manner that Half Scan uses phase direction data.

6-38

AMI[%] (Asymmetric Measurement Imaging)- Indicates the percentage

(usually 20% to 30%) of the early portion of the echo signal that will not be

measured, as there is more noise in the beginning of the echo signal (as shown

in figure 6-55). Asymmetric measurement imaging a llows the user to shorten the

TE and increase the number of slices, and may result in improved contrast on

Tl -weighted images. However, if AMI[% ] is set to 30% or higher without

setting Half Echo to ON, spatia l resolution may be degraded (Half Echo is

described next in th is section).

Frequency direction GC

_j: 100% .., , ~ ...

Asymmetric measurem imaging(%)

Echo signal---___{

Figure 6-55. AMI[%] illustration.

L

Half Echo-Prevents degradation of spatial resolution during AMI[%]. Half Echo creates an image by estimating the uncollected data (based on the

col lected data) in the frequency direction. It a llows for the use of a shorter TE,

or lower bandwidth. The options are:

• off- Does not use half echo.

• ON-Uses half echo.

Echo Type- Indicates the echo allocation method, and is fixed as Half.

Used only in spectroscopy (Half is automatically selected when Sequence is

MRSSE).

Rect .FOV (Rectangular Field of View)- Reduces the number of acquisit ion

points in the phase direction (set in the Phase# parameter). Rect.FOV is used to

match the size of the phase encoding direction for the scan target, as well as for

the FOY that has been set.

The scan time will be reduced by the amount that the value of Phase# is

reduced. Although the spatial resolution is the same as for a normal scan, the

SNR will be reduced in accordance with the number of reductions in the phase

encoding direction.


QS4-86717v3

Scan Parameters 0 As shown in figure 6-56, the options include:

• off- Does not use Rect.FOY.

• Auto-Acquires the size of the patient in the phase encoding direction, and

then automatically determines the FOY actua lly acquired and the number of

acquisition points in the phase direction.

• Manual - Allows the user to select the size of the rectangular FOY.

off

off Auto Manual

Figure 6-56. Rect.FOV options.

Size[% J- Available when Rect.FOV is Manual. Allows you to enter the size

of the rectangular FOV to be acquired; this value is displayed as a percentage of

the current FOV parameter (under Seq. Parameter). Figure 6-57 shows

Size[% ] set to 80, meaning the FOV will be reduced by 20% in the phase

encoding direction.

Figure 6-57. Size[%] example.

Anti.aliasing- Removes aliasing artifacts that are produced when the patient

is larger than the FOY in the phase encoding direction. Anti-a liasing is also

effective in reducing motion artifacts in certain anatomic regions (such as the

chest or abdomen).

As shown in figure 6-58, the options include:

• off- Does not use anti-aliasing.

• Auto - Acquires the size of the patient in the phase encoding direction. The

FOV that is actually acquired and the number of acquisition points in the

phase direction are automatically determined based on the value of the Mode

parameter, which is described next in this section. The available Mode options

are Res and Time.

• Manual -Allows the FOV size to be entered in the Size[% ] box. The

available Mode options are Res, T ime, and TimeRes.

lhPMIFiiii! off off Auto Manual

Figure 6-58. Anti.aliasing options.

6· 39


Note:

If# RF Prep is set to an extremely low value, data with large signal variations will be acquired, causing artifact.

6-40

Mod e-Specifies the manner in which anti-aliasing is performed: maintaining

spatial resolution, maintaining scan time, or both. The following options are

always available:

• Res-Spatial Resolution Mode. Increases the number of acquisition points

in the phase direct ion according to the value ofthe Size[% ] parameter. The

spatial resolution is maintained, but the scan time increases based on the value

of the Size[% ] parameter.

• Time-Scan Time Mode. Increases the acquisition FOY according to the

value of the Size('% ] parameter, but does not change the number of acquisition

po ints in the phase direction . The scan time is maintained, but the spatial

resolution decreases based on the value of the Size[% ] parameter.

The following additional option is available when Anti.a liasing is Manual:

• TimeRes- Scan Time/Spatial Resolution Mode. Doubles the number of

acquisition points in the phase direction and automatically reduces the

effective NSA by half. The NSA parameter must be set to an even number.

The SNR, scan time, and spatial resolution are all maintained.

Figure 6-59 shows the Mode options.

Manual

Res

Res Res Time Time

TimeRes

(a) (b)

Figure 6-59. Mode options when Anti.aliasing is Auto (a) and Manual (b).

Size[%J- Indicates the size ofthe FOV that is measured when Anti.aliasing is

Manual. This number represents a percentage of the number entered in the

FOV parameter (under Seq. Pat-amete r). If Mode is T imeRes, Size[% ]

defaults to 200. Figure 6-60 shows the Size[% ] parameter set to 150.

Figure 6-60. Size[%] parameter option.

# RF Prep-Allows you to enter the number of reserve RF excitations prior to scanning. Th is value can affect both image contrast and artifacts.# RF P rep is

avai lable when Sequence is BASG.

DummyEcho- Aiaows the short TE signal component to be skipped when

acquiring heavily T2-weighted images. DummyEcho is available when Sequence is Prime FSE or P l"ime FIR.


QS4-86717v3

Scan Parameters 0 NaviEcho-Determines if the navigation echo used for compensation is

acquired. NaviEcho is automatically set to ON when Sequence is DW EPI and

Shot Num. is 2 or more.

• off- The navigation echo is acquired.

• ON- The navigation echo is acquired and compensation is implemented.

RF Phase- Allows you to enter the phase angle of the RF pulse when the RF

pulse is used to control the prev ious excitation s ignal. The unit is degrees. RF

Phase is avai lable when Sequence is BASG or PBSG. RF Phase is displayed

but unavai lable when Sequence is RSSG, TOF, PC, or RSSG EPI.

Figure 6-61 shows that Sequence is BASG, with# RF Prep set to 37 and RF

Phase set to I 17.

04 44 5 llmil Eml

Figure 6-61. RF Phase parameter example.

P hase Dir. A- Specifies the phase encoding direction for the axial (AX) plane.

Phase Dil'. A is available when Slice Plane is AX, SA, CA, or SCA. As shown

in figure 6-62, the options are:

• A-P-Sets the phase encoding direction as Anterior-Posterior.

• R-L-Sets the phase encoding direction as Right-Left.

R-L

R-L A-P

Figure 6-62. Phase Dlr. A options.

6. 41

0AS Is· MRI System Reference Manual n. htJ•t llqJMt

Note: If homogeneity of the magnetic field is poor, FatSat is vulnerable to magnetic field distortion and the fat suppression effect is lowered due to the generation of artifacts. Therefore, be sure to carry out volume shimming before performing FatSat.

Note: More echoes need to be acquired to fill the measurement space in order to acquire images with the same spatial resolution as that of Normal Scan. This results in a longer scan time than that of Normal Scan.

Note: If chemical shift occurs when using RADAR, the fat in the image may be blurred ..

6-42

Phase Dir. S -Specifies the phase encod ing direction for the sagittal (SAG)

plane. Phase Dir. S is available when Slice Plane is SAG, SA, SC, or SCA. As

shown in figu re 6-63, the options are:

• A-P-Sets the phase encod ing direction as Anterior-Posterior.

• H-F -Sets the phase encod ing direction as Head-Foot.

Figure 6-63. Phase Dir. S options.

P hase Dir. C -Specifi es the phase encoding direction for the coronal (COR)

plane. Phase Dir. C is available when Slice Plane is COR, CA, SC, or SCA. As

shown in figu re 6-64, the options are:

• R-L-Sets the phase encod ing direction as Righr-Left.

• H-F -Sets the phase encod ing direction as Head-Foot.

Figure 6-64. Phase Dir. C options.

RADAR

RADAR (RADial Acquisition Regime) is a nonorthogonal sampl ing scan

function, which samples K-space in a radial pattern. It is used to reduce motion

artifacts.

The RADAR section of the ScanParameterList window (figure 6-65) contains

the following parameters:

RADAR

'1!!'11'1

7

111 ON

M!ifil- ( Res ·J • r='404===:E=*=:*"fl ... ~ M•Fi ._124--==:E*""- *"Q~ 1§61 30 [·'·]

Figure 6-65. The RADAR section of the ScanParameterList window.

A Caution RADAR can create artifacts in the tangential and circumferential directions,

unlike artifacts that may occur with conventional scan methods. Care shou ld be

taken to avoid a potential misdiagnosis.

RADAR-Specifies whether the RADAR function is ON or off. RADAR can

be used when Sequence is FSE, FIR, primeFSE, primeFIR, SE, or BASG.


Note: Blade refers to a segmented area that rotates in the measurement space.

Phase

QS4-86717v3

Scan Parameters 0 Mode-Specifies measurement mode. As shown in figure 6-66, the options are;

• Res-Scan time increases while resolution is maintained.

• Time-Scan time is maintained and resolution decreases.

I'*' Re;;

Res Time


Proj# - Displays the total number of acquired echoes. Proj# is set

automatically, according to the value of Phase# (under Seq. Parameter).

E. Factor -Sets the number of echoes acquired per Blade. As E. Factor

increases, scan time decreases.

Blade - Disp lays the number of Blades used in the RADAR acquisition. The

system automatically calculates and displays the number of Blades, based on the

values of the Proj.# and E. Factor parameters. Blade approximates the Proj.#

value divided by the E. Factor value (Blade = Proj.# +E. Factor).

Figure 6-67 shows the relationship between Blade and E. Factor values.

E. Factor Blade Phase

Figure 6-67. The relationship between Blade and E. Factor values.

Block- Indicates the number of partitions for the entire scan. Block is available

when Sequence is BASG and Saturation is FatSat, or when Sequence is

BASG and Gating is anything but off.

Segment-Indicates the number of segments per FatSat pulse. Segment is

automatically calculated by the system using the values in the E.Factor, Blade,

and Block boxes as follows:

Segment = (Blade x E.Factor) + Block

6·43

0AS Is~ MRI System Reference Manual ThehtlentMqiMt

Note: When STIR-type fat suppression is carried out using Tl time, do not set Saturation to FatSat.

Note: If you have not set a TR value that makes the phases for water and fat opposite (around 6.8[ms]) when Saturation is PhaseCycle, the fat suppression results may be insufficient.

6-44

Saturation

The Saturation section of the ScanParameterL ist window contains the

fol lowing parameters:

Satura tion -Provides the following options for suppressing specific signals, as


• off- Does not perform signal suppression.

• FatSat-Suppresses MR signals produced by fat elements by eliminating

specific RF waves. Clicking FatSat from the Saturation list also displays the

Wave, Duration, and RF amp.[% ] parameters. The maximum number that

can be set in the M ulti slice box (in the Seq. P a ra meter area) may be reduced

ifTR is to be maintained . In addition, the SNR may decrease and contrast may

change, depending on the settings for the Dura tion and Off.Freq parameters.

• Segment FS- Segmented fatsat pulse used with TIGRE sequences to

maintain fat suppression in dynamic scans.

• PhaseCycle-Scanning is performed multiple t imes and fat signals are

selectively suppressed. M ulti scan mode (in the Scan Control area) must be

set to F luoro or Dynamic and Sequence must be BASG.

• Water Excitation- Water magnetization is selectively excited and fat

magnetization is suppressed. Smaller composite pulses (that add up to 90

degrees) are used; only water protons are flipped to the transverse plane and

can emit a signal.

A Caution When Water Excitation is selected, the input range of FA changes. Check FA

and set it to an appropriate va I ue if necessary.

• Water Saturation - Particular RF waves are irradiated to suppress MR signals

emitted from water. Used only in spectroscopy (Water Saturation is

automatically selected when Sequence is MRSSE).

••"'''

A Caution

off

off FatSat PhaseCycle Water Excitation

MNSF!.

Figure 6-68. Saturation options.

off

off FatSat SegmentFS Water Excitabon

Be sure to carry out shimming before sta1ting a water excitation measurement.


Definition: Precession refers to the secondary spin of hydrogen nuclei when placed within a magnetic field.

QS4-86717v3

Scan Parameters 0 Additional Parameters when FatSat is selected

When FatSat is selected from the Saturation list, as shown in figure 6-69, the

following additional parameters are available:

Saturation

•e•11 Ad S1re

*¥"!! I '"''' Mild !I

••••

Figure 6-69. Clicking Fat Sat from the Saturation list displays additional parameters.

Wave- Provides options for the waveform of the fatsat pulse, as shown in

Figure 6-70. Each of these waveforms maintains a minimum TR, which limits

the number of s lices avai lable. H-Sinc L ight suppresses lipids. H-Sinc Heavy

suppresses lipids and fatty protons, which precess at the same frequency as

water.

AI ( s1ne r....;S;.;.;.In;.;;.e ___ -i

1-\.Sine Ught 1-\.Sine He

Figure 6-70. Wave options.

When acqu iring T2-weighted images with a large FOV, the following settings

are recommended:

• Sine- When Sequence is DW EPI

• H-Sinc Light or H-Sinc Heavy - When Sequence is FSE or Prime FSE

Dura tion - Allows the time (in milliseconds) for the fatsat pulse to be entered.

Duration determines the frequency bandwidth for the patient signal that is

suppressed by the fatsat pulse. Time and frequency bandwidth are inversely

related (for example, a shorter time results in a wider bandwidth).

RF amp.r% 1-AIIows the strength (RF amplitude) of the fatsat pulse to be

entered. If RF amp.[% J is changed, the suppression effects offat signals wi ll

change. 100% ofthe initial value is the optimal strength calculated from the

Wave and Duration parameters.

O ff.Freq[Hz)-Displays the frequency difference (in Hz) between the fat peak

and the water peak. Off.Freq!Hzl is fie ld-strength-dependent and should not be

changed. At 1.2T, the value is -173Hz. Off.F req[Hz) is unavailable when Freq.

graph is Auto or ON.

6· 45


6-46

Segment-May be used to improve fat suppression results when Sequence is

BASG and Saturation is FatSat. In creasing the segment number divides the

fatsat pulse into segments. This may decrease scan time, but also decreases the effectiveness of the fatsat pulse.

Additional Parameters when Segment FS is selected

When Saturation is Segment FS (for use with TIGRE sequences), Wave

options include Sine and H-Sinc, as shown in figure 6-71. The recommended

wave is H-Sinc, as it provides more consistent fat suppression.

··- Sonc

Sine H-Sinc


Additional Parameters when Phase Cycle is selected

When Saturation is P hase Cycle, the fo llowing additional parameter is

avai lable, as shown in figure 6-72:

Quasi TimeRes- May improve time resoEution by sharing data. Quasi

T imeRes is available only when M ulti scan mode (in the Scan Control area) is

F luo ro or Dynamic.

S aturation

*"'" FIN••;• off

fr""'7:~N------.~~

Figure 6-72. Quasi TimeRes options.

Additional Parameters when Water Excitation is selected

When Saturation is Water ExciJtation, as shown in figure 6-73, the following

additional parameter is available :

Saturation

MQI!.

*II f Water Excitatoo .;:)

1-1

1- 1 1-2-1 1-3-3-1


Wave- Indicates the wave for the RF excitation pulse; each group of composite

pulses add up to 90 degrees. As the pulse number increases (and the tota l pulse

is longer), the water selection increases and the fat suppression effects improve;

however, the images will have more noise. The following options are available:


QS4-86717v3

Scan Parameters 0 • 1-1 -One 45° pulse, one 45° pulse.

• 1-2- 1- 0ne 22.5° pulse, one 45° pulse (2x22.5°), one 22.5° pulse.

• 1-3-3-1 - One 11.25° pulse, one 33.7 5° pulse (3 x 11.25°),

one 33.75° pulse (3x 11.25°), one 11.25° pulse.

Additional Parameters when Water Saturation is selected

When Saturation is Water Saturation, the following additional parameters are

available:

Wave- Displays the water saturation pulse excitation waveform.

Water Sat BW-Sets the water saturation pulse bandwidth (ppm).

Freq. Graph Parameter

All Saturation selections include the Freq. graph parameter, which is

explained below.

Freq. graph- Determines whether or not to display a frequency graph in

the Fr·equency Prescan window, which is described in the next section. The

following options are avai lable, as shown in 6-74:

• off- Does not display the frequency graph.

• Auto - When the offset frequency for the fatsat pulse is determined in the

Exam window, that value is used during the acquisition. Auto can only be

used when Saturation is FatSat.

• ON- Displays the frequency graph.

off Auto ON

Figure 6·74. Freq. graph options.

6·47


Note: Hitachi recommends using the Peak method because the Weighted method is prone to error (e.g., metal in field when the field homogeneity is distorted).

6-48

Frequency Prescan Window

The F requency Prescan window, as shown in figure 6-75, displays the

frequency graph results. This window appears at the beginning of a scan when

Freq. gra ph is ON or when F req. graph is Auto and Saturation is FatSat.

Fat peak Frequency Prescan

Water peak

Figure 6-75. The Frequency Prescan window.

This window contains the following features:

Frequency (MHz) - Displays the center frequency of water (MHz).

Offset F requency (MHz)- Represents the precessional frequency difference

(Hz) between fat and water. This value is field-strength-dependent and should

not be changed. At 1.2T, the value is -173Hz; this is the frequency of the fatsat

pulse.

Noise Threshold (%)- Used when Weighted is selected for the Search

Mode, which is described next in this section. Noise Threshold(%) allows the

threshold percentage to be selected for determining the center frequency by the

center of gravity method.

Search Mode-Allows the search method to be selected for determining

frequency values from the following options:

• Peak- Peak method, where the center frequency is set at the signal 's

maximum frequency value.

• Weighted-Center of gravity method, where the center frequency is set to the

center of gravity for signal values at or greater than the threshold.

Reset Param-Returns the values on this window to their initial settings.

CONTINUE button - Restarts the scan.

STOP button -Stops the scan.


QS4-86717v3

Scan Parameters 0 The graph display, as shown in figure 6-76, has the fol lowing features:

Offset frequency (fat peak)

Signal value axis

Center frequency (water peak)

Frequency (MHz) axis

Figure 6-76. Frequency Prescan window features.

• Vertical axis-Signal value

• Horizonta l axis - Frequency MHz)

• Green ve1t ical line- Offset frequency (fat peak)

• Blue vertica l line - Center frequency (wate r peak)

• Red horizontal line - Threshold when using the center of gravity method (not

shown in figure 6-76)

• Orange point - Acquisition data point (not shown in figure 6-76)

A Caution If the center frequency is changed on the graph of the frequency prescan results,

there will be an offset produced in the position of the acquisition plane. The

reference image (scanograrn) should be rescanned.

While the graph is displayed, ifprescanning is canceled using the Stop

button on the Frequency Prescan window or the Abort button on the control

panel, the frequencies that have been set will not be applied to all subsequent

acquis itions.

In addition, once the center frequency and offset frequency have been set, they

will be maintained until one of the fol lowing types of acquisitions is performed:

• Acquisition with F req. graph set to ON.

• Acquis ition with Prescan set to ON.

• Acquisition with the Exam window changed (for example, Sequence or other

parameters have been changed).

• Acquis ition with the receiver coil changed.

6· 49


Note: Hitachi recommends clicking Sine from the Wave list for more uniform frequency response and better uniformity.

6-50

T2W Prep (available with CardioSuite)

T2W P rep - A prepulse that enhances the T2 contrast of the imaging target.

When T2W P rep is applied to the 3D BASG sequence with FatSat, the tissue

contrast improves but the SNR drops slightly. The available options are:

• off- T2W Prep pulses are not irradiated.

• ON - T2W Prep pulses are irradiated. When ON is selected, Duration is

displayed.

Duration -Sets the duration (in milliseconds) of the T2W Prep prepulse

application.

MTC The MTC (Magnetization Transfer Contrast) section of the ScanParameterL ist

window (figure 6-77) contains the following parameters:

MTC • '.t\fd•/.::0

Durat1on I I

RF amp [uT] I I

Off Fceq[fHz] II

Figure 6-77. The MTC section of the ScanParameterList window.

MTC- Changes the contrast of images by changing the magnetization

movement between bound water and free water. The MTC pulse is activated

prior to slice plane excitation.

Wave-Selects the waveform of the MTC pulse, as shown in figure 6-78.

[JiM Sine

Sine Gaussian



QS4-86717v3

Scan Parameters 0 Wave options are Sine and Gaussian, which differ in function as shown in

figure 6-79.

Sine function type Gaussian function type

Duration .. Duration

v~

I RF amp. 1 RF amp.

Figure 6-79. Function comparison for Wave options.

Duration - Indicates the activation time in milliseconds for the MTC pulse.

This value determines the frequency bandwidth of the MTC pulse. A shorter

duration produces a. wider frequency bandwidth and a longer duration time

produces a narrower frequency bandwidth.

RF amp.l ~tTI-Indicates the activation strength (RF amplitude) of the MTC

pulse.

Off.Freqlkzl- lndicates the offset frequency (in kHz) ofthe MTC pulse.

VENC

The VENC (Velocity Encoding) function uses phase information to acquire the

flow rate and flow direction of blood. The VENC section of the

ScanParameterList window (figure 6-80) contains the following parameters:

VENC

•• ON

16§¥ ~0 l· l:;j • II· 1

• I H-F •. ,. off

FiiiiMi! ON

Figure 6-80. The VENC section of the ScanParameterList window.

6. 51


6-52

VENC-Available when Sequence is PC (Phase Contrast). When VENC is

ON, a flow encode pu lse is applied to target the blood flow.

The following parameters are available when VENC is ON:

Target Vel. - Indicates the flow rate for the target vessel in centimeters per

second. This value is a vector volume with size and direction. The value of this

parameter is the maximum val ue that can be acquired on the flow rate image;

however, flow rates that exceed the value set will be acquired as flows in the

reverse direction.

VENC Dir# - lndicates the number of axes where the flow encode pulse will

be appl ied. Provides the fol lowing options, as shown in figure 6-81:

• ! -Applies the flow encode pulse to one axis. Use the VENC Dir. parameter

(described next in this section) to select this axis.

• 3- Applies the flow encode pulse to the following three axes: the A-P axis

(front-back direction), the R-L axis (right-left direction), and the H-F axis

(body axis direction).

Figure 6-81. VENC Dir# options.

VENC Dir. -Available when VENC Did# is 1. Allows you to select the one

a,'<is to which the flow encode pulse will be applied . As shown in figure 6-82, the

options are.

• A-P- Applies the flow encode pulse to the A-P axis.

• R-L-Applies the flow encode pu lse to the R-L axis.

• H-F- Applies the flow encode pulse to the H-F axis.

Figure 6-82. VENC Dir. options.

Vel. Image- Reconstructs a flow velocity image in each axis, in add ition to the

differential combi11ation image.

Com b. Image - Reconstructs the differential combination image (angiography

image); defaults to ON. These images can be used for the MIP post-processing

task. This task is described in the "Task MTP" section of Chapter 8, " Post

Processing Tasks."


Note: When a multi-slab scan is performed using SSP, the following must be considered when selecting the Rate parameter:

Since the slab is excited when sloped in the slice dtrection with SSP. the flip angle varies at the higher and lower parts. The difference of this flip angle appears as contrast.

The difference of contrast of stationary tissue appears as the edge of a step between slabs. However, the step is not always the same. and will not be prominent if Rate is low, but will be if Rate is high.

Note: Single-slab scanning is recommended with SSP.

QS4-86717v3

Scan Parameters 0 SSP The SSP section of the ScanParameterList window (figure 6-83) contains the

following parameters:

194§91111·

Figure 6-83. The SSP section of the ScanParameterList window.

SSP (Sloped Slab Profi le)-Applies an RF pulse using gradient profile

excitation to minimize the saturation of blood flow within a volume (slab).

SSP is available when Sequence is TOF and 2D/3D is 3D. Changing the RF

excitation angle inside the slab affects the spins (in the flowing blood) as they

move through the volume. A smaller angle is needed for blood entering the

volume; the angle should increase as the blood flows through the volume.

Ra te- Indicates the RF pulse ratio (slope) of inflow region to outflow region.

A larger volume demands a steeper slope, as it takes more time for blood to flow

through this larger area. The options are:

• 1.5- The ratio is 1:1.5 (smallest s lope).

• 2 - The ratio is 1:2.

• 2.5- The ratio is I :2.5.

• 3 - The ratio is I :3 (steepest slope).

Direction- Specifies the RF pulse gradient direction. Select one of the

fo llowing options to increase the RF pulse in the specified direction:

• F<H- Increases from feet to head.

• H< F -Increases from head to feet.

• R<L-Increases from right to left.

• L<R- Increases from left to right.

• A<P- Jncreases from anterior to posterior.

• P<A-Increases from posterior to anterior.

The options that can be selected for each slice plane are as follows:

• For AX- F<H and H<F

• For SAG - R<Land L<R

• For COR-A<P and P<A

Example: For the Circle of Wil lis (COW), the F< H direction would be used.

This places the smaller angle at the feet, where the blood enters the volume.

6· 53


Note: Since MPG pulses are applied in Diffusion Tensor Imaging, it is sensitive to motion. In multishot measurements, to reduce artifacts due to motion. use pads to immobilize the patient as much as possible and use gating.

6-54

MPG Motion Probing Gradients (MPG) are the grad ient magnetic fields used in

diffusion weighted imaging. These grad ients are needed when imaging the

proton diffusion phenomenon. The MPG section is available when Sequence is

DWEPI.

The MPG section of the ScanParameterList window contains the following

parameters:

MPG (Motion Probing Gradient) - Specifies if the MPG function is ON or off.

MPG Dir#-Selects the number of axes to which the MPG pulse is applied.


• Single-Applies the MPG pulse to the A-P, R-L, or H-F axis.

• Trace-Applies the MPG pulse to the three axes in sequence.

• Tensor6- Appl ies the MPG pulse to six axes, which includes A-P, R-L, H-F,

and three obl ique directions: A-P with R-L, A-P with H-F, and H-F with R-L

(this is a purchasab le option associated with the Diffusion TensorSuite).

• Tensor7-Applies the MPG pulse to seven axes (this is a purchasable option

associated with the Tensor Suite).

• Tensor1 3 -Applies the MPG pulse to 13 axes (this is a purchasable option

associated with the Tensor Suite).

• Tensor21 - Applies the MPG pulse to 21 axes (this is a purchasable option

associated with the Tensor Suite) .

••• Single

Single Trace TensorS Tensor7 Tensor1 3 Tensor21

Figure 6-84. MPG Dir# options.

Gradient Mode- Indicates the mode to which the MPG pulse is applied. The

fo llowi ng options are provided, as shown in figure 6-85:

• Single- Applies the MPG pulse to the axis selected in MPG Dir #.

• Complex-Applies the MPG pulse to the three axes (A-P, R-L, H-F).

This parameter is unavailable when MPG Dir# is Tensor6, Tensor7, Tensor13,

or Tensor21.

IWW@M Single Single Complex

Figure 6-85. Gradient Mode options.


Note: Hitachi recommends using a b·factor of 1000, which is the clinical standard. Different b-factors can be used based on radiologist preference.

QS4-86717v3

Scan Parameters 0 b-factor - AIIows the b-factor of the MPG pulse to be entered. The application

time and application strength of the MPG pulse are automatically calculated

based on the b-factor value.

MPG Dir.- AIIows you to select the application axis. MPG Dit·. is available

when MPG Dir# is Single. The following options are provided, as shown in

figure 6-86:

• A-P- Applies the MPG pulse to the A-P axis.

• R-L-Applies the MPG pulse to the R-L axis.

• H-F - Applies the MPG pulse to the H-F axis.

Figure 6-86. MPG Dir. options.

Scan Control

The Scan Control section of the ScanParameterList window (figure 6-87),

contains the following parameters:

-.J . ! .. o I

WJ.Ei ,.. Every =-:::J ••••• 1

''*·II I oo oo o _, MHI§IF!~G;;;,;a;,;;,d!!!!!!!!!!!!!!!!!!!!!!~,-1 MMII o_o '4Ai!ii I oo oo o WF!QFiii ON

~----.... §I.IF!$ oft ,...:;;....--==~ 1111111@ oft ~--==~ MI!MI!I9 off ~--===-! ++M+ oft ~-=----I&F¥1 Auto

Figure 6-87. The Scan Control section of the ScanParameterList window.

6· 55


6-56

Scan mode -Specifies the mode, if scans are to be repeated. The following

options are provided, as shown in figure 6-88:

• Once-Repeats only once.

• Discontinuous - The system asks w ith each repetition whether to perform the

scan or not.

• Every - Performs a scan the number of times equal to the value specified in

the R epeat Number parameter, described later in this section.

Once Discontir~uous

Figure 6-88. Scan mode options.

Multi scan mode-Specifies the petformance mode for the scan. The fo llowing

options are avai lable, as shown in figure 6-89:

• Normal- Performs a normal scan.

• Dynamic- Performs a scan that repeats multiple times. The time interval for

scans to be repeated can be set.

• Fluoro- Repeats a scan a number oftimes in as shott a period as possible.

During scann ing, parameters can be changed in real time.

Normal Dynamic Fluoro

Figure 6-89. Multi scan mode options.

Wait mode - Specifies the scan wait mode. The following options are

avai !able, as shown in figure 6-90:

• off-Does not pause before statting a scan.

• Auto - When Wait# is used to perform a multi-acquisition scan with multiple

breath holds, Auto enables the Auto Voice funct ion to automatically give

breath-hold instructions for each acquisition. The user does not have to press

the CONTINUE button for each acqu isition to be acquired.

• ON - Pauses before statting the scan once the prescan is finished; tim ing of

the pause is determined by the value in Wait# .

.. f off off Auto ON

Figure 6-90. Multi scan mode options.

Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.

QS4-86717v3

Scan Parameters 0 Wait#- Indicates the number of acquisitions the system will perfonn prior to

pausing. Wait# is available when Multi scan mode is Normal or Dynamic,

Wait mode is ON, and Multi Acquisition (in the Seq. Parameter area) is 2 or

more. Wait# must be one number lower than the value in Multi Acquisition.

The fo llowing options are available:

• 0 -Scanning is perfom1ed continuous ly.

• 1- Pauses once before starting the main acquisition; the system counts the

prescan as the first acquisition.

• 2 or more- Pauses after performing two or more acquisitions, depending on

the number of acquisitions set in Multi Acquisition. For example, with Multi

Acquisition set to 5, and Wait# set to 3, the system w ill perform the prescan

and two add itional acquisitions before pausing.

After pausing, click the CONTIN UE button (figure 6-91) to resume scanning.

t·M§+d off a•·m•• ::: •

Figure 6-91. Click CONTINUE to resume scanning.

BH Time- Indicates breath-hold time per acqu isition when Wait# is not 0.

Start wait time-Sets the wait time before the scan starts. This is displayed as

minutes:seconds.tenths-of-seconds, as shown in figure 6-92. Start wait t ime is

only available when Multi scan mode is Normal and Wait mode is off.

I oo oo o

Figure 6-92. Start wait time.

Repeat Number - Specifies the number of repetitions of the scan. Repeat

Number is only available when Multi scan mode is Normal and Wait mode is

off.

No of scan set-Allows you to specify the number of scan repetitions and the

repetition interval (or wait) for each set (scans can be divided into a number of

sets with a maximum of3). No of scan set is available when Multi scan mode

is Dynamic.

6·57


6-58

Pre-Cont. (Pre-Contrast)- Specifies the number of repetitions for the first set

of scans. Figure 6-93 indicates three repetitions for this first set.

delay time (for Pre-Cont.) - Specifies the wait time for the start of the first set.

This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Pre-Cont.)-Specifies the interval (in seconds) between

repetitions of the first set. Pre-Cont. must be set to 2 or more.

Scan#1 1st Gap Time

Scan#2 1st Gap Time

Scan#3

.. .. .. .. .. .. Individual Scan Time Individual Scan Time Individual Scan Time

Figure 6-93. Pre contrast illustration.

wait mode (for Pre-Cont.) - Prov ides the fo llowing options for the fi rst set of

repetitions:

• off- Does not pause when starting.

• Every-Pauses with each repetition. When Every is selected, gap time is hidden from view.

• Once- Pauses only for the first repetition.

After pausing, click the CONTINUE button to resume scam1ing.

Early Post Cont. (Early Post Contrast) - Specifies the number of repetitions

for the second set of scans. Early Post Cont. is available when No of scan set is

set to 2 or 3.

delay time (for Early Post Cont.) - Specifies the wa it time for the sta11 of the

second set. This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Early Post Cont.)-Specifi es the interval (in seconds) between

repetitions of the second set. Early Post Cont. must be 2 or more.

wait mode (for Early Post Cont.) - Provides the following options for the

second set of repetitions:

• off-Does not pause when sta11ing.

• Every- Pauses with each repetition. When Every is selected, gap time is

hidden from view.

• Once- Pauses on ly for the fi rst repetition.

After pausing, c lick the CONTrN UE button to resume scanning.


QS4-86717v3

Scan Parameters 0 Late Post Cont. (Late Post Contrast)-Allows you to specifY the number of repetitions for the third set of scans. Late Post Cont. is available when No of

scan set is set to the maximum value of3, as shown in figure 6-94.

Figure 6-94. Late Post Cont. is available when No of scan set is 3 (max. value).

delay time (for Late Post Cont.)-Specifies the wait time for the start of the

third set. This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Late Post Cont.)- Specifies the interval ( in seconds) between

repetitions of the third set. gap time is available when La1e Post Cont. is 2 or

more.

wait mode (for Late Post Cont.) - Provides the following options for the third

set of repetitions.

• off-Does not pause when sta1ting.

• Every- Pauses with each repetition. When Every is selected, gap time is hidden from view.

• Once- Pauses only for the first repetition.

After pausing, c lick the CONTIN UE button to resume scanning.

6· 59


6-60

Contrast agent-Allows a contrast agent to be specifi ed, when scanning with a

contrast agent (figure 6-95). If Multi scan mode is Dynamic, No of scan set

must be a value greater than 1 to make Contrast agent available. The list of

contrast agent options can be custom ized in the Patient Registration Setting

window. Refer to Chapter 4, "Patient Information Functions," for complete

contrast agent option list customization detai ls.

'-=o:::...ff ----L----, None Femseltz Ferric ammot>1um citrate Fendex FerumOXIdes ProHance Gadoteridol Magnev.st Meglumine gadopel\letate Gad Primovist

Figure 6-95. Contrast agent options.

Volume[ml] - Volume[ml] is available when a Contrast agent is selected. Sets

the volume of contrast agent to be used in milliliters, as shown in figure 6-96.

Gad

!2oo I· EJ

Figure 6-96. Volume[ml] example.

Travel Time- Used during contrast-enhanced magnetic resonance angiography

(CE-MRA). Enter the time it will take for contrast to arrive at the target area,

wh ich is determined from the test injection during the dynamic scan

measurement (figure 6-97).

Figure 6-97. Travel Time example.

Additional parameters displayed under Travel Time include:

OffsetTime-Used during CE-MRA. Displays the time that should be the

initial setting for the stop watch. The contrast agent is to be injected when the

stop watch reaches zero.

ContinueTime- Used during CE-MRA. Displays the timing when the contrast

agent is injected and the CONTINUE button is clicked.


QS4-86717v3

Scan Parameters 0 O rg. Image-Specifles whether or not to reconstruct the source images, as

shown in figure 6-98. Org. Image is available when M ulti scan mode is

Dynamic or F luoro, and Sub. I mage (described next in this section) is F ixed,

Moved , or FxMv.

ON

off ON

ON

Fe<ed

Figure 6-98. Org. Image and Sub. Image settings to reconstruct source images.

Sub. Image- Specifies the method for creating subtraction images for dynamic

scans. Sub. I mage is available when M ulti scan mode is Dyna mic or F luoro.


• off- Does not create a subtraction image.

• Fixed - Creates subtraction images us ing the first scan as the mask for all

subsequent scans (fixed mask).

• Moved-Creates subtraction images in which each scan uses the previous

scan as its mask (moved mask).

• FxMv- Creates both types of subtraction images: fixed and moved.

A Caution

off FIX!!d Moved FxMv

Figure 6-99. Sub. Image options.

When subtraction is performed, immobilize the patient as much as possible so

the images are as unsusceptible as possible to body movements.

The examples show how fixed and moved subtraction images are created:

Example: In fi xed subtraction, scan I is subtracted from scan 2, scan I is

subtracted from scan 3, and so on. The mask is fixed using scan I (figure 6-1 00).

Fixed-subtracts 2-1 3-1 4-1

Figure 6-100. A fixed subtraction example.

6. 61


6-62

Example: In moved subtraction, scan I is subtracted from scan 2, scan 2 is

subtracted from scan 3, and so on. The mask moves from scan to scan (figure

6-1 01).

Moved-subtracts 2-1 3-2 4-3

Figure 6-101. A moved subtraction example.

Sub. Mask Start#-Allows you to enter the number of the scan that starts the

subtraction process~ng when Multi scan mode (in the Scan Control area) is

F luoro or Dynamic. A black image (an image with all pixel values set to 0) is

output unti l the stat1 of subtraction processing. The examples show how images

are c reated when the value for this parameter is set to 3.

Example: Fixed mask subtraction, where scan 3 is the mask scan (figure 6-1 02).

Figure 6-102. Fixed mask subtraction using a Sub. Mask Start# value of 3.

Example: Moved mask subtraction where scan 3 is the fi rst mask scan (figure

6-1 03).

Figure 6-103. Moved mask subtraction using a Sub. Mask Start# value of 3.


Note: If moving the patient table during volume shimming correction, the shimming correction effect is lost. Therefore, movement of the patient table by the Centering option is disabled when the center of scan position is included within the volume shimming scan region. If the center of scan position is not included within the volume shimming scan region, the result of volume shimming is canceled and the patient table is moved.

Note: Static magnetic field distribution data of the volume shimming to be used in -egional shimming needs to be acquired again when moving the patient table with the Centering option.

Note: When Shading is NATURAL or when RAPID Mode is RCM, a warning message is displayed prompting you to redo the S-Map measurement if the patient table is moved approximaely 2 inches (Scm) or more by the Centering option. When aliasing artifact or nonuniformity of sensitivity occurs in a scanned image. redo the S-Map measurement.

Note: When the patient table moves long distances or to a position far from the initial positioning image for the first time. a table movement confirmation message is displayed. Confirm the safety of the patient and select CONTINUE.

QS4-86717v3

Scan Parameters 0 When M ulti scan mode is Dynamic, Sub. Mask Start# cannot be greater than

the sum of the P re-Cont., Early Post Cont., and Late Post Cont. values.

Disk save- Available when M ulti scan mode is F luoro. Provides the

following options for saving images to the database (figure 6-1 04).

• off- Only the images for which the SAVE button on the Exam window was

clicked will be saved to the database.

• ON-Saves all images to the database.

=:J· I .. i .I

Figure 6-104. Disk save options.

Table move- Provides the following options for moving the patient table, as

shown in figure 6- 1 05:

• off- Does not move the table.

• Centering - Moves the table to the center of the magnetic field, depending on

the position of the acquisition plane.

• Manual-Moves the table to the position that has been entered in the

Position lmml parameter (described next in this section).

Centenng Manual

Figure 6-105. Disk save options.

Position [mm]- Available when Table move is Manua l. Allows you to enter

the d istance of patient table movement in millimeters, as shown in figure 6-106.

Figure 6-106. The Posltion[mm] parameter.

6· 63


Note: When Auto Voice is ON. the following parameter checks and recalculations are made:

If gap time between each scan (Pre-Cont., Early Post Cont .. and Late Post Cont.) in Dynamic scan mode is shorter than the voice output time (SCANEND(Every) + SCANSTART(Every)), then gap time is recalculated. If wait mode is set to Every, delay time is recalculated.

When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the voice output time (SCANEND(Every) + SCANSTART(Every)), delay time is recalculated.

When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the SCANSTART(Once) or SCANSTART(Every) time, delay time is recalculated.

Note: When Multi scan mode is Fluoro (or Normal and Wait mode is off and a Repeat Number value is specified}, phrases are not output during each scan repetition even if SCANEND(Every) and SCANSTART(Every) are set to ON.

6. 64

Table Wait Mode-Enables/disables the patient table wait mode:

• off- Wait mode is not activated.

• ON - Wait mode is activated. Press the CONTINO E button to move the table.

Cbime (available only wben Auto Voice option is not •·egistered)- Enables/

disables the chime sound when the patient table is moved:

• off- The chime does not sound when the patient table is moved.

• ON - The chime sounds before the table is moved ..

Auto Voice-Specifies whether or not to output an auto voice pattern. The

auto voice pattern can be created in the Auto Voice Setting window, as shown

in figure 6-107. For more information about creating an auto voice pattern, see

the "Auto Voice Setting Window" section of Chapter 9, "Additional Launcher

Functions."

When Auto Voice is off, Start wait t ime (when M ulti scan mode is Normal

or F luoro) or any of the delay time text boxes (when M ulti scan mode is

Dynamic) automatically reset (display 00:00.0 instead of the minutes, seconds,

and tenths of seconds that were entered).

After creating a new auto voice pattern, you will need to close and reopen the

Exam window. Auto Voice then becomes available.

-a Auto Voice Setting

Figure 6-10 7. The Auto Voice Setting window.


Note: • When performing RAPID

sequences, use RAPID receiver coils.

• Some RAPID coils have a restriction on the phase encode direction available for scanning.

• The RAPID factor and direction is different for each RAPID coil.

• Image quality could be reduced if the imaging center deviates greatly from the receiver coil center.

• Image quality could be reduced if slab thickness is set to a smaller value during a RAPID sequence in the slice direction.

Note: With EPI sequence and primeFSEJprimeFIR sequence (only EchoAI/ocation is ADA). RAPID measurement makes that E.Factor decreases with Shot Num. fixed and the total scan time does not decrease.

QS4-86717v3

Scan Parameters 0 Sync. StopWa tch -Starts the timing in the StopWatch window simultaneously

with the acqu isition. Choose from the fo llowing options, as shown in figure

6-108:

• off- Does not synchronize the start of the StopWatch window with the

acquisition.

• ON-Synchron izes the start of the StopWatch window with the acquisition.

I**M•&• off ~1 1-'-o-ff -----f~

ON

Figure 6-108. Sync. StopWatch options.

Prescan- Specifies the prescan mode. Choose from the following options, as


• Auto - Automatically performs appropriate prescan measurements based on

data from the previous scan.

• ON - Performs prescan measurements at the beginning of the first scan,

acquiring new data. This setting should be used on the first scan for each new

patient. ,,.,, Figure 6-109. Prescan options.

RAPID

The Rapid Acquisition through a Parallel imaging Design (RAPID) function

shortens the scan time. By using multichannel receiver coils, phase encoding is

decreased during the acquisition according to the value set in the RAPID box.

Generally, when decreasing the phase encoding for an acquisition, aliasing

is produced in the image following reconstruction. The RAPID acquisition

function acquires the data using multichannel receiver coils. It develops the

image using a sensitivity map of the receiver coils, thus e liminating alias ing

and shortening the scan time. The SNR of the image is reduced as the value of

RAPID is increased.

You cannot use RAPID unless you perfom1 an S-map that covers the imaging

region. When performing an S-map with RCM, set the imaging region so that it

sufficiently covers the area of interest. If this area is not sufficiently covered, an

error wi II occur when starting the main scan.

During S-map with RCM, a wide imaging region is captured using the T R Body

coil. Since the scanogram is performed using the RF coil, care is required so that

even regions that are not captured in the scanogram do not cause wrap artifacts.

6- 6:;,


Note: Using ADA and RAPID results in a decrease in Echo factor per shot, so that the slice number can be increased without increasing scan time. When RAPID is utilized and Echo A/Joe. is set to ADA for EPI, Prime FSE, or Prime FIR sequences, image blurring and distortion are minimized, resulting in improved image quality.

6-66

For example: When taking images ofthe trunk of a patient 's body, the patient's

arms outside the FOV might cause wrap artifacts during S-map acqu isition.

Th is could lead to fau lty sensitivity correction in the main scan, and therefore

care is required when specifying the settings. Similarly, when taking images

of lower extremities such as the knees or upper extremities such as the e lbows,

other body areas outside the FOV might cause wrap a1tifacts during S-map

acquisition. Thi s could lead to fau lty sensitivity correction in the main scan, and

therefore care is required when specifying the settings .

Since the system is sensitive to any movement by the patient, it is important

to have the patient remain as sti ll as possible during S-map Normal mode

acquisition. To accommodate fo r patient motion such as breathing and

peristalsis, we recommend the Nest mode of the S-Map sequence.

In addition, the following precautions are required to acquire effective three

dimensional sensitivity distribution data when using S-Map:

• Specific positioning and imaging parameter settings to prevent wrap a1tifacts

in the region where the main scan is to be performed.

• Although the cross-section to be acquired depends on the area where imaging

is being performed, to avoid wrap attifacts we recommend that you select

COR or SAG, in wh ich the frequency d irection is usua lly along the axis of the

patient's body.


Note: Because aliasing artifact appears stronger in the center area of the image when performing RAPID scans, it is necessary to set a slightly larger FOV and to set the imaging area in the phase direction to cover the entire imaging object using the Anti.aliasing function.

QS4-86717v3

Scan Parameters 0 Figure 6-1 10 shows how the RAPID function creates images.

0 Coil sensitivity map

Aliased image

Image development anti-aliasing

Figure 6-110. Image creation using RAPID.

Resulting image

The RAPID section of the ScanPara meterList window contains the following

parameters:

RAPJD(Phase), RAPTD(Siice)-Decreases the phase and s lice encoding

in the acquisition according to the values entered, resulting in reduced scan

duration. RAPID(Pbase) and RAPID(Siice) values range from 1.0 to 4.0,

with a precision of 0.1 step. As values are entered in the RAPID(Pbase) and

RAPID(Siice) boxes, RAPID(Total) is automatically calculated and updated.

For example, when RAPID(Phase) is 1.4 and RAPID(Siice) is 1.6, RAPID(Total) will be 2.2 (the second digit to the right of the decimal poin t

is omitted). RAPID acquisition is not performed when RAPID(Phase) and

RAPJD(Siice) are both 1.0, which is the default value.

RAPID(Siice) is available when 2D/3D is 3D and Sequence is RSSG or

BASG. RAPID(Siice) is a lso available when 2D/3D is 3D, EchoTime Mode is

Optimized, and Sequence is FSE, Fffi, primeFSE, or pl"imeFSR.

RAPID(Totai) - Oisplays the product ofthe values entered in the

RAPID(Pbase) and RAPTD(Siice) boxes. This calculation is based on the

equation: RAPID(Pbase) x RAPID(Siice) = RAPID(Total).

6·67


Note: Because the timing to acquire a coil sensitivity map is different depending on the RAPID Mode (even if the same RAPID factor is set), the reduction rates of the scan times are different.

Note: Because data for a sensitivity map is acquired during the prescan in PCM mode, the prescan time is longer than that of other modes.

Note: Because data for a sensitivity map is acquired during the main scan in SCM mode, the scan time of the main scan is longer than that of other modes. However, the prescan time is the same as that of a normal scan.

Note: RCM mode uses an S-Map to prepare the 30 sensitivity map in advance. Acquisition of a 30 sensitivity map using an S-Map under typical imaging conditions takes approximately 40 seconds.

6-68

Mode-Specifies the calibration method for the RAP ID acquisition. The

method may be selected automatically, based on the Sequence that has been

selected. The following options are available, as shown in figure 6- 111 :

• PCM (Prescan Cal ibration Method)-Acquires the coil sensitivity map during

prescan. The additional options available with this mode are described next in

this section.

• SCM (Self Calibration Method)-Acquires the coil sensitivity map during the

RAPID scan. Thi s is the default mode when certain sequences are selected.

• RCM (Reference Ca libration Mode) - Uses the sensitivity map acquired

during the S-map scan.

RCM SCM PCM

Figure 6-111. RAPID Mode options.

When Mode is PCM, the following additional parameters are available:

PCM Mode-Determines the control method for collecting a coil sensitivity

map during prescan. The default value is Auto, as shown in figure 6-112.

Figure 6-112. The PCM Mode parameter.


• Auto-Automatically determines whether or not to use the coil sensitivity

map collected during the previous prescan. If it can be used, reacquisition

of the coil sensitivity map is not petfonned. If there is no previous coil

sensitivity map, it is collected. Reacquisition of the sensitivity map will not

be performed ifthe following conditions are the same as during the previous

collection:

- Slice position , obl ique angle, slice interval

-Slice plane, phase direction

-Multi-slice, multi-acquisition

- FOV, reconstruction matrix

• ON-Collects a sensitivity map during each prescan.

Figure 6-113. PCM Mode options.


QS4-86717v3

Scan Parameters 0 PC M Wait mode-Specines whether or not to have a wait mode before

collecting a coil sensitivity map during the prescan. Choose from the fo llowing

options, as shown in figure 6-114:

• off- Does not go to standby before collecting a coi l sensitivity map.

• ON - The status changes to standby before collecting a coil sensitivity map.

l••w•M,_o_ff ___ --f off ON

Figure 6-114. PCM Wait mode options.

PC M NSA-Sets the number of signal averages when collecting the coil

sensitivity map during the prescan. The larger the value, the better the image

quality becomes; however, the prescan time is increased. The default (initial

value) is l , with a maximum value of8.

Gating

The Gating section of the ScanPara meterList window contains the following

parameters:

Gating-Allows the type of gated scan to be selected. Choose from the

following options, as shown in figure 6-115:

• off-Gated scan not selected.

• MS-ECG-Eiectrocardiograph (pu lse wave) gated scan selected.

• C ine- Cine gated scan selected.

• Resp- Respiratory gated scan selected.

Figure 6-115. Gating options.

The additional parameters that are available will vary with the type of gating

selected. the Sequence that is selected, and related scan parameters. In the

following parameter descriptions, applicable gating types are included in

parentheses after the parameter names, as shown in the example:

Example: Beat Rate (MS-ECG, Cine, Resp) indicates that the Beat Rate

parameter applies to MS-ECG, Cine, and Resp gating.

Beat Rate (MS-EC, Cine, Resp)- Enter the heart rate (in beats per minute) for

MS-ECG and Cine gating. Enter the respiratory rate for Resp gating. The heart/

respiratory rate is displayed in the WaveForm window.

6· 69


6-70

# HB Prep (C ine [ava ilable with CardioSuite])-lndicates the reserve heart rate

prior to performing the acquisition. The Gate Mode parameter (located two

parameters below# HB Prep) must be Delayed, as shown in figure 6-116.

C.ne

Figure 6-116. The # HB Prep parameter with the Delayed Gate Mode requirement

Gating Source (MS-ECG, C ine, Resp)- Indicates the signal source for the

gated scan. Se lect from the fol lowing options:

• ECG- Indicates the electrocardiograph as the signal source. ECG can be

selected when Gating is MS-ECG or C ine, as shown in figure 6-117.

• Pulse- Indicates the peripheral pulse as the signal source. P ulse can be

selected when Gating is MS-ECG or Cine, as shown in figure 6-117.

MS-ECG

ECG Pulse

Cine

ECG ECG Pulse

Gating is MS-ECG Gating is Cine

Figure 6-117. Gating Source options.

• Resp- Indicates respiration as the signal source. Resp is the fixed default

when Gating parameter is Resp.

Gate M ode (MS-ECG, Cine) - Indicates the electrocardiographic synchronous

mode. Choose from the following options, as shown in figure 6- 118:

• Gate-Gate method

• Trigger- Trigger method

• Delayed- Delayed enhanced method (available with CardioSuite)

• MyoPer-Myocardial pe1fusion method (available with CardioSuite)

Gate

Gate Trigger Delayed MyoPer

Figure 6-118. Gate Mode options.


QS4-86717v3

Scan Parameters 0 Resp Mode (Resp)- lndicates the respiratory synchronous mode; the fixed

default is Trigger, as shown in figure 6- I 19.

U!i&l! Tngger

Figure 6-119. The Resp Mode parameter.

Count (MS-ECG, Cine, Resp )- Indicates the number of R-wave intervals or

respiratory cycles needed to collect the desired amount of slices. The Count

value is dependent on the heart rate (a higher heart rate, with shorter R-R

intervals, requires an increased Count to obtain more slices). When Gate Mode

or Res1> Mode is Trigger, Count affects the TR. The value of I is automatically

set when Gate Mode is Gate.

Multi Phase (Cine)- Indicates the number of images to be taken at the same

position but at different heart phases. In figure 6-120, Gating is Cine and M ulti

Phase is 24.

Figure 6-120. The Mutt Phase parameter.

Segment (MS-ECG [with CardioSuite], Cine)- Indicates the segment number.

Increas ing the segment number allows less slices per R-R waveform . Segment

can be specified in the fol lowing cases, as shown in figure 6-121:

• When Gate Mode is Gate

• When Gate Mode is Trigge•· and Sequence is BASG, SARGE, or RSSG

• When Gate Mode is Delayed and Sequence is BASG

Gate Mode is Gate, Segment is 3 Gate Mode is Trigger, Segment is 3

Figure 6-121. The Segment parameter.

6. 71


6-72

DelayMode (Resp) - Indicates the input unit for Delay measurement. Select

from the fo llowing:

• Time-Sets the Delay in milliseconds (ms). The Delay represents the time

from the trigger signal to the initial sl ice TE.

• Rate-Sets the Delay as a percentage(%). The Delay represents a percentage

of the breathing cycle from the trigger signal to the TE of the initial slice.

• Min -Automatically appl ies the minimum delay time after the trigger for

image acqui sition to begin.

Delay[ms] (MS-ECG, Cine, Resp) - lndicates the time in milliseconds from the

trigger signal until the TE of the initially acqu ired sl ice.

Delay (%) (Resp)- fndicates a percentage of the breathing cycle as the delay

from the trigger signal to the TE of the initial slice.

Interval (MS-ECG, Cine, Resp) - Indicates the time interval between the

collection of each sl ice or each phase.

Echo Alloc. (MS-ECG, C ine)-AIIows se lection of the echo a llocation method.

This setting can be specifi ed in the following cases:

• When Gate Mode is Gate

• When Gate Mode is T rigger and Sequence is BASG

Choose from the following options:

• Sequential-Arranges segments sequentially.

• Centric- Arranges segments centrically. Centric is available when Sequence

is BASG (2D), BASG (3D, with Gate Mode set to Tt·igger), SARGE (2D),

RSSG, PC, TOF, or RSSG EPI.

Figure 6-122 illustrates the allocation of acquisition data for the two Echo Alloc.

methods.

Phase encoding direction

Segment#1 Segment#2 Segment#3

j Segment#4 Segment#3 Segment#2

Segment#4 Segment#1 Segment#5 Segment#1 Segment#6 Segment#2

Segment#? Segment#3 Segment#4

Sequential Centric

Figure 6-122. Allocation of acquisition data comparison for the Echo Alloc. methods.


Note: When a gating procedure is started with Beat Rejection set to ON, use the value displayed in the WaveFonn window (the patient's heart rate) to enter in the Beat Rate box (in the Gating section of the ScanParameterList window). and don't excessively narrow the range of the regular beat.

Note: When a gating procedure is started with Beat Rejection set to ON and 16 consecutive irregular heart beats are recorded. Beat Rejection is automatically switched to off.

QS4-86717v3

Scan Parameters 0 Echo Shift-Allows the number of echo shifts to be entered. The range is

dependent on the number of segments. Figure 6-123 shows the implementation

of echo shifts.

Phase encoding direction

Segment#1

Segment#2

Segment#3 j Segment#6

Segment#1

Segment#2

Segment#3 Segment#2

Segment#1

Segment#3

Segment #3

Segment#2 Segment#4 Segment#3 Segment#1 Segment#1

Segment#5 Segment#4 Segment#2 Segment#1

Segment#6 Segment#5 Segment#3 Segment#2

Sequential/shift: 0 Sequential/shift: 1 Centric/shift: 0 C:=mtric/shift: 1

Figure 6-123. An Echo Shift illustration.

Beat Rejection- An irregular heart rhythm or pulse (arrhythmia) can cause

image quality deterioration when Gating is MS-ECG or Cine. Beat Rejection

eliminates data acquired when a1Thythmia occurs. Choose from the following

options:

• off-Data acquired when arrhythmia occurs is not e liminated.

• ON - Data acqu ired when arrhythmia occurs is eliminated. When Beat

Rejection is ON, Skip Beat, L level[%[, and H level[%] are accessible.

A Caution The beat rejection function is not effective for patients that suffer from

arrhythmia due to cardiac disease.

Skip Beat- Specifies the number of normal beats skipped after an arrhythmia.

L level[% 1- Enter the shortest regular heartbeat cycle (as a percentage of the

regular hea1tbeat cycle). The regular heartbeat cycle corresponds to the R-R

interval, which the system calculates based on Beat Rate.

H level[% 1- Enter the longest regular hea1tbeat cycle (as a percentage of the

regular hea1tbeat cycle). The regular heartbeat cycle corresponds to the R-R

interval, wh ich the system calculates based on Beat Rate.

Summary of Gating Parameters

The following table provides a summary of scan conditions and the various

parameters that are available when Gating is MS-ECG, Cine or Resp, and

instructions for how the parameters should be set.

6· 73

0AS/S~ MRI System RefeTence Manual n.. Pau ... .._

Parameters When the Gating parameter is: Available MS-ECG Cine Resp

Beat Rate Enter the heart rate Enter the heart rate Enter the respiratory rate

Indicates reserve heart rate; #HBPrep Unavailable range is 0 to 2. Gate Mode Unava ilable

must be set to Delayed 1•

Gating Specify ECG or Pulse Specify ECG or Pulse Resp

Source

Gate Mode Specify Trigger, Gate, Specify Trigger, Gate,

Unavai lable Delayed 1, or MyoPer1

• Delayed 1, or MyoPer1•

Resp Mode Unavailable Unavailable Trigger

Indicates the number of R Indicates the number of R Indicates the number of

Count waves; 1 is set if Gate Mode waves; 1 is set if Gate Mode respiratory cycles

is Gate. is Gate.

Indicates the number of Multi P hase Unavailab le images at same position, but Unavai lable

differing heart phases.

Enter a number if Gate Mode Enter a number if Gate Mode is: is: •Gate •Gate

OR OR

Segment •Trigger, with Sequence •Trigger, with Sequence

Unavailable set to BASG, SARGE, or set to BASG, SARGE, or RSSG RSSG

OR OR • Delayed!, with Sequence set • Delayed 1, with Seq uence set to BASG to BASG

Delay Mode Unavailable Unavailable Select Time (ms) or Rate (%)

Delay[ms] Indicates time from trigger Indicates time from trigger Indicates time from trigger signal to initial slice TE signal to initial slice TE signal to initial s lice TE

Enter rate(%) of breathing Delay(%) Un ava ilable Unavailable cycle from trigger signal to

TE of initial slice

Interval Indicates scan time interva l Indicates scan time interval Indicates scan time interval for each slice or phase for each slice or phase for each slice or phase

Echo Alloc.- Choose from: Choose from: Gate Mode • Sequential • Sequential must be Gate OR OR

Unavailable (or Trigger •Centr ic (with SARGE, • Centric (with SARGE, with BASG RSSG, BASG, TOF, PC, or RSSG, BASG, TOF, PC, or sequence) RSSG EPI) RSSG EPI)

Beat Unavailable

Select off or ON. If ON, enter Unavailable

Rejection a Skip Beat value.

Specifi es the number of Skip Beat Unavailab le normal beats skipped after an Unavailable

arrhythmia. 1 Available with CardioSuite.

6. 74 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Paramete r s

Availa ble

L level[% ]

H level[%)

Note:

Scan Parameters 0 When the Gating parameter is:

M S-ECG C ine R esp

Sets a measurable range for Sets a measurable range for Sets a measurable range for trigger intervals when the beat trigger interva ls when the beat trigger intervals when the beat parameter is off. When Beat parameter is off. When Beat parameter is off. When Beat Rejection is ON, sets the R-R Rejection is ON, sets the R-R Rejection is ON, sets the R-R interval ratio for the shot1est interval ratio for the shot1est interval ratio for the shortest regular heartbeat cycle. regular heartbeat cycle. regular heartbeat cycle.

Sets the R-R interval ratio for

Unavailable the longest regular heartbeat.

Unavai lable Use when Beat Rejection is ON.

NAVI

The NaviPulse (navigator acquisition function) is an optional function used to

reduce scanning artifacts in regions (such as the heart) where the pos ition is

moved by breathing.

Navigator echo position and main scan region must be kept apart.

With this function, breathing movement is monitored by acquiring an additional

echo, called a navigator echo, from the region perpendicu lar to the diaphragm.

Using the monitored change in the position of the diaphragm, scanning

is performed with the patient "free-breathing." The s lice position can be

adjusted according to the displacement observed from the monitored breathing

movement.

QS4-86717v3

Figure 6-1 24 shows how the NaviPulse function works.

Head

I Feet

Acquisition position for navigator echo

I Breath gating for this scan I

--- I Monitoring breath movement I

Figure 6-124. Nav/Pulse illustration.

6. 75


6-76

The Navi section of the ScanParameterList window (figure 6-125), contains


Figure 6-125. The Navi section of the ScanParameterList window.

NaviP ulse- Provides the fo llowing options, as shown in figure 6- 126:

• off- Does not perform navigator acquisition.

• NaviGate- Performs nav igator acqui sition.

• SlicePos-Available on ly when Sequence is BASG, performs navigator

acquisition and adjusts the sl ice position to compensate for slice variation due

to respiratory movement.

off

off NaviGate SltcePos

Figure 6-126. NaviPulse options.

GateWindow-Indicates the gate window width in mill imeters. The

acquis ition data is effective on ly when the position of the diaphragm is in the

gate window prescribed by this width. The default (initial value) is 3 mm.

Data Number·- Indicates the number of acquisition points fo r the navigator

data. The selection can be 64, 128, or 256 points, as shown in figure 6-127.

64 128 256

Figure 6-127. Data Number options.

CorrCoeff-Available when NaviPulse is SlicePos. CorrCoeff sets the ratio

of variation in slice position (due to respiratory movement) to the value of the

position adjustment. For example, if the respiratory movement detected by the

navigator mon itor is I Omm and the CorrCoeff is set to 0.6, the slice is adjusted

by 6mm.


QS4-86717v3

Scan Parameters 0 NaviMonitor - Indicates the method for the NaviMonitor acquisition during

the prescan. Choose from the following options, as shown in figure 6-128:

• ON-NaviMonitor acquisition is always performed prior to an acqu isition.

• Auto - In cases where the monitor acquisition has been performed for the same

acquisition, the system decides if the data is usable or not. If it is usable, the

acquisition will start without the performance of a monitor acquisition during

the prescan. If it is not usable, a NaviMonitor acquisition will be perfonned.

Figure 6-128. NaviMonitor options.

Monitor T ime- Indicates the time for the Nav iMonitor acquis ition.

PAPE

Partia l Phase Encode (PAPE) is an optional function used to improve temporal

resolution whi le maintaining the spatial resolution of the image.

The PAPE section of the ScanParameterList window (figure 6-129) contains

the fo llowing parameters:

Figure 6-129. The PAPE section of the ScanParameterList window.

PAPE- Provides the fo llowing options:

• o ff- PAPE is off.

• ON- PAPE is on.

PAPE can be set to ON when M ulti scan mode is Dynamic or F luoro, and one

of the following combinations are selected from the 2D/3D and Sequence lists:

• 2D and SARGE

• 2D and BASG

• 2D and TRSG

• 2D and RSSG

• 3D and RSSG

Scan Time- Displays time, but is unavailable. This is the time needed to

perform the acquisition, while ignoring the K-space high frequency waves.

6. 77


Note: It is recommended to set Data Rate[%] higher when scanning a region with movement.

6-78

Segment-Indicates the number of segments to be partitioned forK-space. As

the number of segments increases, the scan time per image becomes shorter,

but the update interval for high frequency data becomes longer. The selections

include 3, 5, 7, or 9.

Data Rate[% ]- Indicates the ratio for low-frequency data that will definitely

be measured(%). As this rate is increased, image quality improves but temporal

resolution degrades. The range is from 10 to 60 percent, in five percent

increments.

Scan Cycle- Displays the number of cycles. Scan Cycle is set automatically

and remains at one number lower than the setting for Segment. Scan Cycle

options include: 2, 4, 6, or 8.

Filter/PostProcessing

The Filter/PostProcessing section of the ScanParameterList window contains


Org.Image-Specifies whether or not to reconstruct origina l images. Org.

Image is available when Sequence is PC (Phase Contrast). Choose from the

following options, as shown in figure 6-130:

• off- Does not reconstruct original images.

• ON - Reconstructs original images.

Figure 6-130. Org.lmage options.

Calc.lmage- Specifies whether or not to create differential images for scanned

images. Depending on the sequence selected and imaging conditions, the Calc.

Image options might not be available, might be set automatically, or may not

even be displayed. Available options are:

• off-Does not create differential images.

• Sub-Creates differential images.

• Combine- Combines data acquired with each multi echo into a single image

series. Available when Sequence is GE, SARGE, or RSSG and Multi Echo

is greater than 1.


QS4-86717v3

Scan Parameters 0 Image Type-Specifies the type of images to be displayed. Image Type may

be avai lable, or may be set automatically (unavailable), depending on the option

selected from the Sequence list.

The fo llowing options are available when Sequence is IR or FIR (figure 6-131 ):

• Abs-Displays absolute value images.

• Real - Displays Real images.

~····Ill 1111,._:_5_5 ___ .....,. ,

Real I Figure 6-131. /mage Type options.

The following option is automatically set when Sequence is Shim (figure 6-132):

• Phase- Displays Phase images.

QU.I· Phase

Figure 6-132. Image Type option when Sequence is Shim.

RawData Save- Avai lable to Hitachi fie ld service engineers. Specifies whether

or not to save the raw data to the database before image reconstruction. As

shown in figure 6-1 33, the options are:

• off- Does not save raw data to the database.

• ON- Saves raw data to the database.

Figure 6-133. RawData Save options.

Truncation - Filtering that can be used to reduce artifacts that may appear

when data col lection conditions allow the system to acquire fewer than the

required encoding numbers (for example, low phase encoding settings of 128 or

160). Choose from the fo llowing options, as shown in figure 6-134:

• off- Does not use the truncation fi Iter.

• ! - Applies the lightest amount of fi ltering.

• 2 - Appl ies a medium amount of filte ring, more than 1, but less than 3.

• 3 -Applies the heaviest amount offi ltering.

I ill r@i!l.i' 3 ,.._o_ff-----t

1 2 3

Figure 6-134. Truncation options.

6. 79


Note: When acquiring the S-Map data in preparation for the NATURAL option, make sure the area to be scanned is adequately covered.

6-80

Shading - Filtering that corrects for signal intensity differences throughout the

image. Choose from the following options, as shown in figure 6-135:

• off- Does not use the shad ing correction fi Iter.

• NATURAL-Uses the shad ing correction with 3D sensitivity map. It is

necessary to first acquire the 3D sensitivity map using the S-Map Sequence.

• Hybrid - When used with multiple images that are scanned in the same

position (such as with Dynamic mode), the degree of correction in the fi rst

scan is applied to later scans. When used with multiple images that are not

scanned in the same position (such as 3D scans), the degree of correction is

kept constant along the slice direction.

• Manual -Uses the shad ing correction filter. The Correction parameter

(described next in th is section) wi ll be displayed.

pn.;. NATURAL

off NATURAL Hybnd Manual

Figure 6-135. Shading options.

Correction-ind icates the intensity of the shad ing correction. The higher the

value, the stronger the correction wil l be. Correction is avai lable when Shading is NATURAL, Hybrid or Manual. The options range from Typel to TypeS

when Shading is Hybrid or Manual. The options are off, Typel or Type2 when Shading is NATURAL (figure 6-136).

4'141F' Type1

Type I Type2 Type3 Type4 Type5

(a)

163114'"·1•

{b)

off

off Type1 Type2

Figure 6-136. Correction options when Shading is (a) Hybrid or Manual and {b) NATURAL.

T2 correct.-Corrects for T2 decay that occurs with long echo train sequences.

The options are shown in figure 6-13 7.

iFF.!.!§ off

off Manual

Figure 6-137. T2 correct. options.


Note: When Sequence is isoFSE. T2 correct. is automatically set to Manual and T2 Target is no longer available. Only Level[%] can be set.

QS4-86717v3

Scan Param e ters 0 Leveii% 1- Sets the level of the T2 Amplitude Correction Filter, The larger the

value, the stronger the correction. L evel[% ] is available when T 2 correct. is

Manua l (figure 6-138).

;*i'i"'i§3iii[ Manual IMII [3§11 °oo1 ___l = ~ ~ J IMI!i!i [iOo"" =r -I -1

Figure 6-138. Level[%] and T2 Target parameters.

T2 Target-Sets the T2 value for the T2 amplitude correction area. T2 Target

is available when T2 correct. is M a nual (figure 6-138). T2 Ta rget should be

set to match the TE value.

Ad a ptive F ilter - Performs fi Iter processing for the scanned image (figure

6-139). For more adaptive fi Iter information, refer to the "Review Task

Window'· section of Chapter 7, "Review and Fi lming Functions".

•••!§ lloff ~ II off SmiShO Sm1Sh1 Sm1Sh2 Sm2Sh0 Sm2Sh1 Sm2Sh2 Sm3Sh0 Sm3Sh1 Sm3Sh2 Sm4Sh0 Sm4Sh1 Sm4Sh2 M1n Med Max MRAM1n MRAMax

Figure 6-139. Adaptive Filter options.

Ed ge enhance- Performs edge enhancement for the scanned image. For more

edge enhancement information, refer to the ··Review Task Window" section of

Chapter 7, " Review and Filming Functions''.

MIP I mage- Specifies whether or not to create MTP reference images

automatically after the scan is finished. Choose from the following options, as


• ofT- Does not create MIP reference images.

• ON-Creates MlP reference images automatically after d1e scan is finished.

~~l,lil41'819111111~o_N ______ ~~~

I ~N j

Figure 6-140. MIP Image options.

6. 81


Note: When Diffusion Analysis is ON, the DW EPI sequence is vulnerable to magnetic field distortion. If homogeneity of the magnetic field is poor, image degradation and artifacts may occur. To reduce this effect, be sure to carry out volume shimming before starting Diffusion Tensor Imaging.

6-82

When MIP Image is ON, the following parameters become available:

MIP Edge Enh.- Adjusts the quality of the MIP reference images that are

created. The adjustment range is from -5 to 5. The image smoothness increases

as it approaches -5, and the image sharpness increases as it approaches 5.

MlP Dir.-Selects the view direction ofMIP reference images. Choose from

the following options, as shown in figure 6-141:

• front-Creates MIP reference images viewed from the same direction as the

direction set in Slice P lane.

• AX-Creates MIP reference images viewed from the axial direction.

• COR-Creates MI P reference images viewed from the corona l direction.

• SAG-Creates MIP reference images viewed from the sagittal direction.

• SA-Creates MIP reference images viewed from the sagittal and axial directions.

• CA- Creates MIP reference images viewed from the coronal and axial directions.

• SC-Creates MIP reference images viewed from the sagittal and coronal directions.

• SCA-Creates MIP reference images viewed from the sagittal, coronal, and

axial directions.

@iii AX 1-fr- o-nt----{

AX COR SAG SA CA sc SCA

Figure 6-141. MIP Dir. options.

For more information about MIP reference images, refer to the "Task MIP"

section of Chapter 8, "Post-Processing Functions."

Diffusion Analysis-Specifies whether or not to create diffusion analysis

images automatically after the scan is fi nished. Diffusion Analysis is available

only when Sequence is DW EPI. Choose from the following options:

• off- Does not create diffusion analysis images automatically.

• ON - Creates diffusion analysis images automatically after the scan is

finished.

When Diffusion Analysis is ON, the following parameters become available:

ADC -Available when MPG Dir# is Single or Trace. If Single is selected,

ADC defaults to ON. IfTrace is selected, the fo llowing options become

available:

• off-ADC images are not created automatically after scanning.

• ON - ADC images are created automatically after scann ing.


Note: The b-factor value summarizes the influence of the gradients in OWl. The higher the b-factor value. the stronger the diffusion weighting. Hitachi recommends a b-factor of 1000.

QS4-86717v3

Scan Parameters 0 DWI trace- Avai lable when MPG Did# is T race, Tensor6, Tensor7,

Tensor13, or Tens01·21 (optional). Choose from the following options, as shown

in figure 6-142:

• off-DWI trace images are not created automatically after scanning.

• ON (with bO) - DWI trace images are created automatically after scanningj

including bO image.

• ON (without bO) - DWI images are created automatically after scanning,

without bO images.

I'"""' ON(without bO) •

off ON(wrth bO) ON(wrthout bO)

Figure 6-142. DWI trace options.

FA (Fractional Anisotropy)- (Associated with the Diffusion TensorSuite,

which is a purchasable option.) Available when MPG Dir# is Tensor6,

Tensor7, Tensorl 3, or Tensor21. Calculates an index FA showing the

anisotropy of diffus ion from the obtained diffusion tensor, and creates an FA

map reflecting an FA value. The options are:

• off- FA images a re not created automatically after scanning.

• ON - FA images are created automatically after scanning.

MD ( Mean Diffusibi lity)- (Associated with the Diffusion TensorSuite, wh ich

is a purchasable option.) Available when MPG Dir# is Tensor6, Tensor7,

Tensor13, or Tensot·21. Calculates the mean of the intrinsic values of

diffusibility and creates an image reflecting the MD. The options are:

• off- MD images are not created automatically after scanning.

• ON-MD images are created automatically after scann ing.

Figure 6-143 shows the FA and MD parameters.

l§liiYY@Wr oN ••;;;

Figure 6-143. FA and MD parameters.

Save Corr.lmage- When Save Corr.Image is ON, the original images and the

distortion-corrected images are saved in the system database. When Save Corr.

Image is off, the corrected images are not created automatically after scanning.

Noise T bresbold- lndicates a threshold value to eliminate background noise.

The range is 0 to 100; increasing the value e liminates more noise.

6-83


Note: Distortion correction settings will vary depending on the body part being scanned.

6-84

Correct Distortion - Specifies whether or not to correct distortion of the input

image. The options are:

• off- Image distortion is not corrected for the FA map, MD map, and OWl

Trace images.

• ON- Image distortion is corrected for the FA map, MD map, and DWI Trace

rmages.

D.C.Levei-Corrects image distmtion generated by nonlinearity in the gradient

magnetic field. The options are:

• off- Image dist01tion is not corrected.

• Auto- The system applies distorttion correction as needed.

• GC-(Grad ient Correction) Distomtion correction is always applied.

When D.C.Level is Auto or GC, Region Cut is displayed.

Region Cut- Regitons that cannot be corrected by the distortion correction

funct ion may appear on the edge oftlhe image. Region Cut options (as follows)

determine whether or not the uncorrected regions aTe cut from the image:

• off- The regions are not cut from the image. This is the recommended option

when scanning large anatomical regions (such as large abdomens), to ensure

that a ll of the anatomy of interest is inc luded.

• Auto- The regions are cut fi·om the image when there are regions that cannot

be corrected by the distortion correction function.

W-Widtbl - Indicates the window width of the display for one echo. The set

value becomes the default window width for displaying images. After an image

is displayed, the window width can be changed.

W-Levell - lndicates the window level of the display for one echo. The set

value becomes the default window level for displaying images. After an image

is displayed, the window level can be changed.

W-Widtb2- Available when Multi Echo (in the Seq. Parameter area) is 2 or

greater. Indicates the window width of the display for two echoes. This value

becomes the default window width for displaying images. After an image is

displayed, the window width can be <:hanged.

W-Levei2 -Available when M ulti Echo (in the Seq. Parametea· area) is 2 or

greater. Indicates the window level of the display for two echoes. This value

becomes the default window level for displaying images. After an image is

displayed, the window level can be changed.


QS4-86717v3

Scan Parameters 0 Figure 6-144 shows the window width and level parameters.

Wijd

••• WI!!

MM'

Figure 6-144. Window width and window level parameters.

Positioning

Positioning parameters allow you to select various options involved with the

scanning and viewing of images.

The Positioning section of the ScanParameterList window (figure 6-145)

contains the fo llowing parameters:

Figure 6-145. The Positioning section of the ScanParameterList window.

Slice Ord. A- Specifies the direction in which the axial plane slices wi ll be

scanned and displayed. Choose from the following options, as shown in ·figure

6-146:

• H-F- From head to feet

• F-H- From feet to head

81&14

Figure 6-146. Slice Ord. A options.

6· 85


Note: Plane Order cannot be changed, but the slice order within a plane can be.

6-86

Slice Ord. S-Specifies the direction in which the sagittal plane s lices wi ll be

scanned and displayed. Choose from the following options, as shown in figure

6-1 47:

• R-L-From right to left

• L- R-From left to right

Figure 6-147. Slice Ord. S options.

Slice Ord. C -Specifies the direction in which the coronal plane slices will be

scanned and disp layed. Choose from the following options, as shown in figure

6-148:

• A-P-From anterior to posterior

• P-A- From posterior to anterior

Figure 6-148. Slice Ord. C options.

Plane O•·der -Displays the scanning order of the slice planes. Plane Order is fo r display only, it cannot be changed.

The following planes are available for display:

• AX-Axial plane

• SAG -Sagittal plane

• COR-Coronal plane

• S-A- Sagittal plane, axial plane

• S-C-Sagittal plane, coronal plane

• C-A- Coronal plane, axial plane

• S-C-A-Sagittal pane, coronal plane, axial plane

Figure 6- 149 shows a Plane Order of S-C-A.

IM§i§ S-C-A

Figure 6-149. The Plane Order parameter.


QS4-86717v3

Scan Parameters 0 Radial Sta ck-Allows easier radial slice stack positioning for MRC P

exams. When Radia l Stack is ON, the radia l stacks move as a group, making

positioning at a central point easier.

To use radial stack positioning, make sure Radia l Stack is ON, then enter the

number of radial stacks to be performed in the Stacks box (located in the Seq.

Para meter area of the ScanParameterList window).

Slice Alloca tion- Ind icates the order of slice excitation for multi-slice

scanning. Slice Allocation is available when:

• 2D/3D is 2D

• Sequence is GE, SAR GE, or RSSG

• The Mode parameter of M ulti Acquisition is Interleaved

As shown in figure 6-150, Slice Allocation options include:

• Default-Scans from one s ide of the s lices to the other side.

• Convergence-Scans from both s ides of the s lices towards the cente r.

HMIM!iii+ (....,;o;;...;;e....;..tau....;..lt __ --4·1 Default I Converpenc~

Figure 6-150. Slice Allocation options.

Line/Box-Specifies the manner in which 20 imaging s lice lines appear when

they are displayed in d1e viewports for positioning. L ine/Box is not displayed

when 3D is selected from the 2D/3D box. The following options are available,

as shown in figure 6-15 I:

• Line- Displays the slice surface as a line.

• Box- Displays the slice surface as a box.

iii§. Une ~.;;...._------i

L1ne Box

Figure 6-151. Line/Box options.

6·87

0AS Is~ MRI System Reference Manual n. hUnt llqnet

6-88

Guide L ine -Specifies whether or not guidelines will appear when changing

slice position or number of slices. Guidelines are the dotted lines displayed at

the top and bottom of the slice group. The following options are available:

• Yes- The dotted lines are longer than the sl ice lines and continue to be

displayed when s lices are moved. Figure 6-152 shows the results when Guide

Line is Yes.

Figure 6-152. The Guide Line parameter set to Yes.


QS4-86717v3

Scan Parameters 0 • No- The dotted lines are approximately the same length as the slice lines and

are displayed around the outer edges of the s lice group. The dotted lines will

e longate and display during s lice movement. Figure 6-153 shows the results

when Guide Line is No.

Figure 6-153. The Guide Line parameter set to No.

G.Intvl-Specifies whether or not the slice interval can be changed for each

s lice stack or slab group for scans that involve multiple stacks or slabs. The

following options are avai lable, as shown in figures 6-154 and 6-155:

• off- The slice interval for each slice or slab group can be changed. When

G.lntvl is off, the lntet'Val box is displayed in the Scan Positioning

Information bar at the bottom of the Task View area. Figure 6-154 shows the

G.Intvl parameter set to off.

I'IMI¥··· 1._ott ____ _.·l

Figure 6-154. G.Jntvl set to off.

6· 89


6-90

• ON - The slice intervals for each slice or slab group are set to the same value

and cannot be changed individually. When G.Intvl is ON, Interval is

displayed in the Seq. Parameter area of the ScanParameterList window.

Figure 6-155 shows the G.Intvl parameter set to ON.

iip ON '------.J

Figure 6-155. G.lntvl set to ON.

Sync.-Specifi es whether to simultaneously change all plane settings when the

settings for position , angle, and slice number are changed, and multiple planes

have been selected. Sync. is available only when Slice Plane is SA, SC, CA, or

SCA. Choose from the fo llowing options, as shown in figure 6-156:

• off-Does not change the settings of a ll planes.

• ON-Changes the settings of a ll planes.

Others

I iii! off

off ON

Figure 6-156. Sync. options.

The Others section of the ScanParameterList window contains the following

parameters:

Receiver Coil-Select the receiver coil name from the list of connectable

receiver coils, as shown in figure 6-157. If Receiver Coil is Auto, the receiver

co il name is recognized automatically.

Auto CTL Large Joint PI/ 00 Flex Body(L) 00 Flex Body(XL) OOHead RAPID Body RAPID Breast RAPID C-Spine RAPID Foot RAPID Head RAPID Knee RAPID NV RAPID Shoulder RAPID Wrist TR

Figure 6-157. Receiver Coil options.


QS4-86717v3

Scan Parameters 0 Mode-Specifies the receiver coil mode for multi-mode coils, such as the CTL

and RAPID Foot coils. A mode can be selected from the Mode list that is

available for the receiver coil chosen from the Receiver Coil list, as shown in

figure 6-1 58.

IB'di*IHI*I'I"IIr RAPtDFoot lj8MI I 811 Ext Full 811 Ext Full Bit Ext Full Lt 811 Ext Full Rt 811 Ext Foot 8~ Ext Foot Lt 8il Ext Foot Rt

41


CTLC CTLCT CTL T CTLL CTL C-No Loop CTL CT-No Loop CTL T-No Loop CTL L-No Loop

If Receiver Coil is Auto, Mode changes to Auto, as shown in figure 6-159. The

system will set the most common mode for the receiver coil that is being used.

Figure 6-159. Mode is Auto when Receiver Coil is Auto.

MorningQA-Specifies checks to be petformed during the morning quality

assurance (QA) procedure. When starting the system, scanning is performed

with fixed parameters to confirm that the system is operating correctly. All

parameters that are currently set are disabled, and the fixed parameters are set.

Choose from the fo llowing options, as shown in figure 6-160:

• off- Does not perform Morn ingQA.

• GC Check - Fl D- Acquires the FID (free induction decay) s ignal.

• GC Check- X-Checks X-axis grad ient movement.

• GC Check - Y - Checks Y-axis gradient movement.

• GC Check - Z-Checks Z-axis gradient movement.

• Coil Check- Checks each channel of the coil.

ii@idl&lfl ,._o_ff ____ -f off GC Check- FID GCCheck-X GCCheck- Y GCCheck- Z Co1ICheck

Figure 6-160. Morning OA options.

6. 91


Note: The TIGRE measurement sequence is a fat-suppression imaging method using a fatsat pulse. To obtain the high tatsuppression effect, homogeneity of the static magnetid field is important. Therefore, be sure to carry out volume shimming prior to performing TIGRE sequence scan. Utilizing the regional shimming function (available as an option) together with volume shim data can provide consistent fat suppression.

Note: With a 30 acquistion, the SNR of the images at the top and bottom edges of the slab is lower compared to that at the center region. Therefore, position the region of interest at the center of the slab and set the number of slice encodes to a slightly higher value.

Note: Hitachi recommends Circular 3D Acq. Mode with TPEAKS Echo Alloc. for all TIGRE acquisitions.

6-92

Soft Sound- Specifies the Soft Sound mode, which decreases the noise level

for certain pulse sequences. Activation ofthe Soft Sound mode requires an

increase in TR, and, consequently, an increase in scan time. Choose from the

follo·wing options, as shown in figure 6-161:

• off- Acquisition is not performed in Soft Sound mode.

• ON -Acquisition is performed in Soft Sound mode.

[11!11.1 off . 11 off ON

Figure 6-161. Soft Sound options.

TIGRE

The TIGRE sequence is a 3D fast, TI-weighted, RF-spoi led SARGE sequence

using a fatsat pulse. This sequence can be used forT L -weighted, fat-suppressed,

dynamic imaging with contrast. A segmented fatsat pulse is used to maintain

fat suppression and provide sufficient temporal resolution for dynamic scans.

Shimming must be performed before the TIGRE acquisition.

The specific parameter selections that are required or recommended for TIGRE

are described below.

Sequence Area

Select the following:

• 2D/3D-Select 3D.

• Sequence-Select RSSG.

Seq. Parameter Area • Echo Alloc.-Select either Cent-Cent or Cent-Seq, as shown in figure

6-162:

Cent-Cent- Echo allocation for phase encode and slice encode directions

are both Centric. The #RF Prep value should be increased (as compared

to the Cent-Seq value) to suppress artifacts, even though th is reduces the

effects of fat suppression.

Cent-Seq - Echo a llocation for the phase encode direction is Centric,

wh ile echo allocation for the sl ice encode direction is Sequential.

IW!iii (Cent-Cent Cent-Cent

I Cent-Seq

IMNI.I TPEAKS

- ('"c-irc_u_la-r -..=....::..::;· )

Figure 6-162. Seq. Parameter area settings.


Note: When 3D Acq. Mode is Circular. Slice# and Segment may be restricted.

Note: If Segment is set to an extremetly large value, longitudinal magnetization of fat is recovered and the fat suppression effect may be reduced.

Note: Make sure to carry out volume shimming before performing the 1.1 TE scan. If homogeneity of the magnetic field is poor, 1.1 TE is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. The scan should be

within the center of the magnetic field as much as possible.

Note: When performing a 1.1 TE scan, a coil or pad may appear in the image.

Note: The 1.1 TE scan is designed to acquire a weighted image, not appropriate for T2 value calculation.

QS4-86717v3

Scan Parameters 0 • 3D Acq. Mode- When Cil·cula r is selected, Echo Alloc. is TPEAKS and the

outer corners of K-space are not acquired, which reduces scan time.

Advanced Area For #RF Prep, Hitachi recommends using a value of about 5 when Echo Alloc.

is Cent-Seq, or a value higher than that when Echo AUoc. is Cent-Cent. This

value represents the number of dummy RF pulses needed to maintain the steady

state after the application of the segmented fatsat pulse. Larger numbers may

improve artifact suppression but also reduce the effect of fat suppression.

Saturation Area Select the fo llowing, as shown in figure 6-163:

• Saturation-Select Segment FS.

• Wave- Select H-Sinc.

• RF amp.[%]- Enter 100.

• Segment- Hitachi recommends a value of about 32.

Saturation

**"·'

Figure 6-163. Saturation area settings.

Additional Notes and Cautions for the 11TE pa r·ameter :

IL Caution Use the RAPID knee coil for 11TE measurements. If any other coils are used,

image quality can be subpar.

A Caution Images may be blurred because the bandwidth is low. The T2 attentuation occurs

due to the extension of sampling time.

A Caution Image quality (image formation) may be altered when the parameters associated

with readout gradient strength, such as FOV, Bandwidth, or Oblique, are

changed.

6· 93

0AS Is· MRI System Reference Manual T1MI htJ•t llqJMt

6-94

Additional F luoroscopy Notes a nd Cautions:

A Caution The scan time displayed does not always coincide with the fluoroscopy image

when displaying the latest images.

A Caution If multi-slice imaging is performed, images are not displayed until all slice data

is obtained.

A Caution When scan time is shorter than reconstruction time, data scanned during

reconstruction may not be displayed or saved.


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