applications guide quantitative cardiac parameter mapping ...10.1007/s10554-016-1034... ·...

Applications Guide

Quantitative Cardiac Parameter

Mapping

(T1 | T2 | T2*)

Work-in-Progress # 780 (VD13A SP4)

N4_VD13A_CV_TXMAP_Z001KZZF_WIP780

MAGNETOM Aera

MAGNETOM Skyra

MAGNETOM Avanto + Dot

MAGNETOM Verio + Dot

syngo MR Numaris 4 VD13A SP4

July 2013

10303439_732C&780-ASD-S02-01

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Quantitative Cardiac Parameter Mapping

Important Note

This document provides a description of techniques developed by Siemens. Siemens

has tested the software provided with this work-in-progress package in combination with

the proposed clinical application. However, each user should be aware of the fact that

incorrect use of this software may produce unknown results.

The sequences contained in this software package do not exceed the FDA safety

performance parameter guidelines for MRI exams. Specifically, there is no change to

patient risk as compared to routine operation of the MAGNETOM with regard to: static

magnetic field; the time rate of change of the gradient magnetic fields; the rate at which

RF power is deposited into the body (SAR); or the acoustic noise created by the

MAGNETOM.

The software has been tested internally but not yet in a clinical environment. For

routine applications, its functionality may not be complete, and use of this software

will remain investigational.

In general, the clinical user will, in his/her sole responsibility, decide on the use of

this application package or on subsequent therapeutic or diagnostic techniques and

shall apply such techniques in his/her sole responsibility.

Siemens will not take responsibility for the correct application of, or consequences

arising from use of, this applications package.

The software in this package may change in the future, or may not be available in future

software versions. Siemens has the right to remove this software at any point. In case of

any questions that are related to the use of this package please contact the Siemens

representative in charge of this package (contact information is provided in the next

page).

Siemens representatives in charge of the package:

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North America: ..................................................................................................................

Bruce Spottiswoode, Ph.D. Siemens Healthcare MR Research and Development Chicago, IL [email protected] ..................................................................................................................

Rest of the world: ..................................................................................................................

Andreas Greiser, Ph.D. Siemens AG Healthcare Sector MR PI CARD Erlangen, Germany [email protected]

.................................................................................................................

Additional developers of this works-in-progress package: Christopher Glielmi, Ph.D. Siemens Healthcare MR Research and Development New York, NY [email protected] ..................................................................................................................

Shivraman Giri, Ph.D. Siemens Healthcare MR Research and Development Chicago, IL [email protected] .................................................................................................................

Randall Kroeker, Ph.D. Siemens Healthcare MR Research and Development Winnipeg, Canada [email protected] ..................................................................................................................

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Table of Contents Improvements since previous versions of the WIP ........................................................... 5

6779

131616171819212424252628282933333637

Introduction ....................................................................................................................... T1 mapping using MOLLI..................................................................................................

Sequence description.................................................................................................... User interface ................................................................................................................ Example images.......................................................................................................... Scanning tips ...............................................................................................................

T2 mapping using T2-prepared TrueFISP ...................................................................... Sequence description.................................................................................................. User interface .............................................................................................................. Example images.......................................................................................................... Scanning tips ...............................................................................................................

T2* mapping using multi-echo GRE................................................................................ Sequence description.................................................................................................. Use interface ............................................................................................................... Example images.......................................................................................................... Scanning tips ...............................................................................................................

Installation....................................................................................................................... Protocols ......................................................................................................................... User feedback................................................................................................................. References...................................................................................................................... Acknowledgements ......................................................................................................... Appendix 1: Hints for the use of the Cardiac Shim .........................................................

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Improvements since previous versions of the WIP

The first version of the TX mapping WIP for VD11D, WIP732B, was ported

directly from the original VB17A WIP448. The only practical difference between

WIP448 and WIP732B relates to the TI times in T1 mapping. In WIP448 the TI

time was defined as the duration between the beginning of the adiabatic

inversion pulse and the center of k-space, whereas in WIP732B the TI time is

more correctly defined from the end of the adiabatic inversion pulse to the center

of k-space. More specifically, the reported TI times in WIP732B are 10240 s

shorter than those in WIP448, and in WIP732C and WIP780 the reported TI

times are 2560 s shorter than in WIP448.

This version of the WIP, WIP780 (VD13A), incorporates a number of

improvements compared to WIP 732B, including:

T1 mapping:

New adiabatic inversion pulse for improved inversion efficiency. The hypersec

adiabatic inversion pulse in the previous WIP versions achieved an inversion

factor of about -0.925. A new shorter tan/tanh design with optimized

parameters is now incorporated, resulting in an inversion factor of about

-0.965.

Correction factor to accommodate for imperfect inversion. For the new

tan/tanh adiabatic inversion pulse, the T1 estimate is divided by 1.035. This

correction is possible because tan/tanh pulse results in a reduced

dependence on both T1 and T2.

Phase sensitive inversion recovery (PSIR) fitting technique for more reliable

T1 estimation and shorter processing times.

New outputs:

o T1* maps, which haven’t experienced the Look-Locker correction, and

can thus be used for more accurate measurement of T1 in blood,

where fresh spins are flowing into the imaging plane.

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o “Goodness of fit” maps introduced as an optional quality assurance

metric.

o Optional synthetic PSIR and MagIR image series’ derived from the

pixel-wise T1 maps.

Protocol improvements offering a shorter scan time and minimal T1

measurement dependence on heart rate.

T2 mapping:

Improved adiabatic T2 preparation with only two refocusing pulses for

shortening the achievable T2 prep time and for reduced RF power

requirements.

Dummy gradients played out during recovery heartbeats.

Protocol improvements offering a centric gradient echo readout strategy for

more accurate T2 measurements with minimal T1 dependence.

T2* mapping:

Improved slice profile to minimize errors due to dephasing.

Introduction

In recent years, quantitative MRI has become increasingly important for

assessment of a range of cardiac diseases. Such techniques can reduce the

subjectivity encountered in traditional non-quantitative techniques, and can

detect global pathological changes within the heart.

Quantification of T1 relaxation is of great importance for the characterization of

myocardial tissue to assess both ischemic and non-ischemic cardiomyopathies[1].

Prior to the administration of contrast, an elevated value of myocardial T1 is

associated with edema which may be related to the inflammatory response to

myocardial injury. Following the administration of a T1-shortening contrast agent,

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a shortened T1 corresponding to increased contrast agent concentration is

associated with fibrotic scar or diffuse fibrosis which has a greater extracellular

volume than normal[2,7,8].

Quantitative T2 mapping is utilized to assess pathologic conditions, such as

acute ischemia, myocarditis and heart transplant rejection, which alter the

myocardial water content and consequently prolong the T2 relaxation times[9-14].

T2 mapping has been shown to accurately and reliably detect regions of

edematous myocardial tissue without the limitations of qualitative T2-weighted

imaging[15].

Similarly, myocardial T2* measurement is a valuable tool for non-invasive

assessment of iron overload, and is clinically employed for planning and

monitoring iron-chelating treatments for transfused thalassemia major patients[17-

20].

This package consolidates T1, T2 and T2* estimation techniques to offer a

comprehensive cardiac parameter mapping with advanced reconstruction

techniques such as motion correction and inline map generation.

T1 mapping using MOLLI

Sequence description

In this package, T1 Mapping is performed using ECG triggered Modified Look-

Locker Inversion Recovery (MOLLI)[3,4]. This technique allows the acquisition of

single shot TrueFISP images acquired at different inversion times after a single

inversion pulse, all gated to the same cardiac phase, thereby enabling a pixel-

based T1 quantification in the myocardium. After the inversion, the magnetization

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following the T1 relaxation curve is repetitively sampled over several heartbeats

until the longitudinal magnetization has fully recovered. By combining several

(typically 2 - 3) inversions with slightly shifted TI times within one protocol, the

relaxation curve is sampled in an interleaved manner, resulting in a sufficient

number of points for accurate T1 quantification acquired within a single breath-

hold. Figure 1 shows the original MOLLI implementation, comprising three

inversion pulses with T1 sampling performed over 3, 3 then 5 heartbeats, and T1

recovery periods of 3 heartbeats.

Figure 1: MOLLI pulse sequence scheme. There are three Look-Locker (LL)

experiments, each prepared by a separate 180 degree inversion pulse (inv). The

inversion time (TI) of the first LL experiment is defined as TIminimum. TI of the second

and third LL experiment are determined by TIminimum + TIincrement and TIminimum +

2TIincrement, respectively. After the inversion pulses, images are read out in a non

segmented fashion with a constant flip angle (). There are a defined number of pausing

heart cycles in between LL experiments in order to allow for undisturbed signal recovery.

Sourced from Ref. 2.

For a group of N frames as inversion recovery images

with different inversion times TIn, the signal for each pixel in position (x,y) is

given by:

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S(x,y,TIn) = A(x,y) - B(x,y) * exp(-TIn/T1(x,y)) (1)

T1(x,y) = T1*(x,y) * (B(x,y)/A(x,y) - 1) (2)

Where A, B, and T1* are estimated by a three parameter fit on the measured

data[5].

To generate the inline T1 map, the acquired inversion recovery images are first

registered using a novel motion correction algorithm[5,6] which is based on

estimating synthetic images presenting contrast changes similar to the acquired

images by solving a variational energy minimization problem. Thereafter, the T1

estimate is computed on a per-pixel basis by performing a non-linear curve fitting

using the three parameter signal model (Eq. 1,2). Note that this version of the

WIP also outputs a T1* map, which can be used to provide a more realistic

estimate of T1 in blood since the inflow of fresh spins obviates the need for the

Look-Locker correction. Also, an improved phase sensitive fitting algorithm has

been implemented for more reliable T1 estimation and shorter processing time.

User interface

Figure 2 shows the Sequence Special card for T1 mapping, which provides

flexible control of the sequence timing and acquisition parameters. Additional

processing steps and optional images can also be set using a number of

checkboxes.

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Figure 2: User interface parameters for T1 mapping.

Parameter map type

This selection controls the type of parameter map (T1/T2/T2*). For MOLLI T1

mapping, this should be set to “T1 Map”. It can also be set to “None”, in which

case the sequence behaves just like the normal product CV sequence.

No. of inversions

This parameter controls the number of inversions, which is equivalent to the

number of passes of the T1 relaxation curve to sample the signal for various

effective TI times.

MOLLI TI start

This parameter defines the initial TI time TI1 as realized in the first heartbeat.

According to the MOLLI acquisition scheme, the next heartbeat has an effective

TI of TI1+RR1.

MOLLI TI increment

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For the normal case where the number of inversions is greater than 1, this

parameter defines the time shift relative to the preceding TI (TIincrement in

Figure 1). These shifts in TI ensure a more uniform sampling coverage along the

T1 relaxation curve.

Acq HB (array)

This parameter array controls the number of heartbeats that are used for data

acquisition after each inversion.

Recov HB (array)

This parameter array controls the number of heartbeats that are used for

recovery of the magnetization before the next inversion is played out. During the

recovery heartbeats, the sequence plays gradient noises so that the subject

doesn’t assume that the scan has finished and inadvertently starts breathing.

Motion correction

This checkbox activates registration of individual inversion images. If selected,

non linear motion correction will be performed before curve-fitting and map

generation. Both the original and registered images will be output as separate

series. If the deformation exceeds a pre-defined threshold for a specific TI image,

then the original (underformed) image for that specific TI will be used for the T1

curve fitting.

Goodness of fit map

Enabling this checkbox outputs a goodness of fit image defined as the sum of the

square of the fitting residuals. This can be used for quality assurance. Note that

this image will be inherently scaled by the magnitude of the MR image, so areas

such as the lungs will appear dark.

Synth MagIR and PSIR

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This checkbox uses the known T1 for each pixel to create a series of synthetic

images describing the magnitude inversion recovery (MagIR) and phase

sensitive inversion recovery (PSIR). Each series comprises 40 images with TI

increments of 25 ms, starting at 200 ms.

Systolic imaging

This checkbox should be enabled if imaging is performed during systole. It

prevents possible SAR warnings in the case of a short trigger delay by including

the time during diastole in the SAR calculations.

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Example images

Figure 3 shows the improvement offered by the non rigid motion correction.

Figures 4 and 5 provide example images from a normal volunteer, and Figures 6

and 7 show the utility of T1 maps in cases with pathology.

Figure 3: Example of MOLLI motion correction. a–c: Original images showing noticeable

motion. d–f: Results by directly applying nonrigid registration causing incorrect

deformation. g–i: Motion correction based on synthetic image estimation. Image from

Ref. 6.

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Figure 4: Example images output by MOLLI T1-mapping in a healthy subject. Top rows

show the original images acquired at different TI times. The bottom rows show the

motion corrected images using a novel non-rigid registration algorithm described in Ref.

[5, 6]. Thereafter, a three parameter fit on the pixel-wise signal values is utilized to

produce T1 estimates.

(a) (b) (c)

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(d)

Figure 5: Additional images output by the T1 mapping sequence (a) T1 map, (b) T1*

map (see Eq. 2), (c) goodness of fit map, and (d) select synthetic MagIR images.

(a) (b) (c) Figure 6: Pre-contrast T1-maps (top row), post-contrast T1-maps (2nd row), late

gadolinium enhancement (3rd row) for patients with: (a) chronic MI, (b) acute

myocarditis, and (c) HCM. Adapted from Ref. 8.

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(a) (b)

Figure 7: (a) Conventional (FLASH segmented) LGE for a patient with extensive MI,

showing a large apical thrombus. (b) The MOLLI T1 map acquired post contrast shows

that the thrombus has long T1 as expected. Courtesy: Dr. Peter Kellman, NHLBI,

Bethesda, MD, USA.

Scanning tips

The MOLLI T1 mapping is performed in a breathhold fashion. Please ensure that

the trigger delay and acquisition window are modified so that the scan window is

positioned during diastole. Also, we recommend reviewing the source images in

addition to the parameter map to ensure that they are co-registered and free of

artifacts. A number of protocols are described towards the end of this document,

including the original MOLLI implementation as well as shorter sequence

versions tailored for pre-contrast, post-contrast, slow and fast heart rates.

For T1 mapping at 3T the use of the Cardiac Shim option is recommended. For

further details, please check appendix 1.

T2 mapping using T2-prepared TrueFISP

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This package provides a T2 Mapping technique[15] that uses a T2-prepared (T2p)

TrueFISP sequence to produce single-shot T2-weighted images, each with

different T2 preparation times. An optional fast non-rigid registration algorithm is

utilized to compensate for in-plane motion between these images. Finally, a

pixel-wise myocardial T2-map is generated using unsupervised curve-fitting

based on the following two parameter equation.

S(x,y) = M0(x,y) * exp(−TET2P/T2(x,y)) (3)

The schematic in Figure 8 shows the sequence operation, which comprises

varying T2-preparations followed by single-shot TrueFISP readout, and

separated by several heartbeats for full T1 regrowth.

Figure 8. Schematic of data acquisition and reconstruction for T2 Mapping. T2p-

TrueFisp images are acquired at intervals of at least 3 RR intervals to allow for sufficient

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magnetization recovery in between acquisitions. For each image, the acquisition window

is in the same diastolic phase. An optional motion correction is applied to correct for mis-

registration between the different images. Finally, a pixel-wise T2 fit is done assuming

mono-exponential signal decay

User interface

Figure 9 shows the Sequence Special card for T2 mapping, which provides

flexible control of the number of T2 preps, the T2 prep duration (TE), and the

recovery period.

Figure 9: User Interface parameters for T2 Mapping

Parameter map type

This selection controls the type of parameter map (T1/T2/T2*). For T2 mapping,

this should be set to “T2 Map”. It can also be set to “None”, in which case the

sequence behaves just like the normal product CV sequence.

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No. Of T2 preps

Represents the number of T2-prepared images used for T2 fitting. The minimum

value is 3 and the maximum value is 12.

T2 prep duration (array)

Represents the T2 prep duration. The array ranges from 1 to the number

selected in “No. of T2 Preps”.

Motion correction

This checkbox activates registration of individual T2 prep images. If selected,

motion correction will be performed before curve-fitting and map generation.

Recov HB

This parameter controls the number of heartbeats that are used for recovery of

the magnetization before the next T2p and readout. During the recovery

heartbeats, the sequence plays gradient noises so that the subject doesn’t

assume that the scan has finished and inadvertently start breathing.

Systolic imaging




Example images

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Figure 10: Advantage of Motion Correction. Top row shows the original uncorrected T2-

weighted images and the corresponding T2 map. Slight variations in cardiac cycle and/or

inconsistent breathhold can produce erroneous map due to the pixel-wise nature of the

fit. On the other hand, with non-rigid motion correction, such minor inconsistencies can

be eliminated and more accurate T2 map can be generated.

Figure 11: Comparison of T2 map images with T2-weighted STIR and late gadolinium

enhancement (LGE) images. The patient > 90% occlusion of RCA, confirmed by x-ray

angiogram. STIR images show no hyper-intensity in inferior regions and high stagnant

endocardial blood signal. The T2 map nicely delineates increased T2 values in inferior

regions and at endocardial borders. LGE image show the extent of the infarct.

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Figure 12: Patient with a myocardial infarct, showing an elevation in both T1 and T2

maps, and a correlation with late gadolinium enhancement image. Courtesy: Drs. Arai

and Kellman, NHLBI, Bethesda, MD, USA

Scanning tips

The T2 mapping is performed in a breathhold fashion. Ideally, the trigger delay

and acquisition window should be modified so that the scan window is positioned

during diastole, but acquisition is also possible during systole if a thicker

myocardium is desired. In the case of systole imaging, be sure to select “Systolic

imaging” on the Special card. A number of imaging protocols are described

towards the end of this document.

The sequence acquires multiple images in one breath-hold, each at a different T2

preparation time. The possible values for T2p are: 0 (i.e. no T2p) and 15-55 ms;

It is recommended that the maximum T2p value be in the vicinity of the expected

T2 of the tissue being imaged. For instance, T2 of healthy human myocardium is

reported to be around 55 ms. Accordingly, the maximum T2p value should be

about 55 ms.

To minimize breath-hold time in cardiac imaging, we recommend the acquisition

of 3 T2P images, i.e. in the WIP special card, set the “No of T2 Preps” to 3.

These 3 images are acquired in single-shot mode, with a gap of 3-4 RR intervals

3

4

5

6

7

8

9

10

11

12

13

80

90

100

110

120

130

140

150

160

T1 map T2 map PSIR LGE


in between to allow for sufficient T1 recovery. If the patient has a sufficiently low

heart rate (RR interval > 1000) -, then a gap of 2-3 RR intervals may be used

(this is done by setting Recov HB in the T2 mapping Special card).

The default protocol is set up accordingly to acquire three T2p at 0ms, 25ms, and

55 ms; these times were chosen to optimize linear least squares fitting for

myocardial T2 Mapping. If the sequence is to be used to generate a T2 map of a

different tissue, then a different set of T2p times should be used. A detailed list of

T1 and T2 values of different tissues can be found in reference [16]. Note that

both conventional and adiabatic T2 preparation can be selected for T2 mapping.

A centric FLASH readout is more accurate in measuring T2 values, whereas

linear TrueFisp slightly overestimates T2. On the other hand, TrueFisp results in

a higher SNR than FLASH. The reason for keeping a linear readout for TrueFisp

is to avoid artifacts due to off resonance. The error in T2 estimate using a linear

TrueFisp is due to T1 effects between the T2p and the center of the readout. T2

mapping is not recommended post contrast, but its worth noting that if the linear

TrueFisp version is run post contrast, the shorter T1 may result in large errors.

As such, we recommend using the centric FLASH version of the T2 mapping

sequence. Figure 13 shows examples of T2 mapping acquired using centric

FLASH and linear TrueFisp readouts.

T2Prep TE = 0 ms T2Prep TE = 25 ms T2Prep TE = 55 ms

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T2Prep TE = 0 ms T2Prep TE = 25 ms T2Prep TE = 55 ms

Figure 13. T2 Maps using FLASH (top) and TrueFisp (bottom) readout schemes.

For T2 mapping at 3T the use of the Cardiac Shim option is recommended. For

further details, please check appendix 1.

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T2* mapping using multi-echo GRE


This WIP uses ECG-triggered GRE sequence to acquire multiple signal echoes

during the T2* decay.

Figure 14: Schematic of data acquisition for T2* mapping. Data is acquired over several

heartbeats and at the same diastolic phase of the cardiac cycle. As all echoes are

acquired in a short time after an RF pulse, all multi-echo images are intrinsically

registered. Therefore, no motion correction is required during map generation.

The signal at each echo-time (TE) is given by,

S(tn) = ρ0 exp(-TEn/T2*) (4)

Where, TEn = nth echo-time, ρ0 = initial signal intensity, and T2* = effective T2

*

for the voxel. Equation (4) assumes a unique T2* value per voxel. In voxels where

multiple T2* components are present, this estimation will provide an “effective”

T2* estimate.

To generate an inline T2* map, an integrated image reconstruction performs

pixel-wise T2* estimation using a robust fitting technique[20,21], in which the signal

at each TE is iteratively weighted to reflect its fidelity to monoexponential decay

curve. Signal points farther from the ideal relaxation curve are weighted lower,

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reducing their influence on the fit. The weights of outlier points can be completely

zero, eliminating their negative impact on the fit.

Use interface

A dedicated UI element is available in the Sequence Special card to generate

T2* maps.

Figure 15: User Interface parameters for T2* Mapping

Parameter map type

This selection controls the type of parameter map (T1/T2/T2*). For T2* mapping,

this should be set to “T2* Map”. This will convert the protocol to multi-echo GRE

protocol, required for T2* mapping. It can also be set to “None”, in which case the

sequence behaves just like the normal product CV sequence.

Systolic imaging

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Example images

Following figures provide some examples and clinical cases using the inline

myocardial T2* mapping.

Figure 16: DB-prep GRE images [A-1, B-1] and corresponding T2*-map [A-2, B-2]

produced using inline analysis in two healthy volunteers. The contours in these images

mark septal regions from which the average T2* value was estimated. The average T2*

value within septal regions were 29.8 ± 4.0 ms and 27.2 ± 3.3 ms for these two subjects,

which are significantly above T2* < 20 ms range indicating cardiac iron overload.

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Figure 17: T2* estimates in 3 patients with suspected iron overload. [A-1, B-1, C-1] A DB-

prep GRE image showing the region used for T2* estimate within CMRTools. The

estimated T2* is listed directly below each image. [A-2, B-2, C-2] Corresponding T2*

maps obtained with inline analysis. Average of pixel-wise T2* estimate was obtained

from indicated septal region. In all 3 cases, the average value obtained from T2*-map

closely matches the one calculated using CMRTools.

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Scanning tips

The T2*-map measurement should be performed in a breathhold fashion. The

readout is typically positioned at mid-diastolic period so as to minimize cardiac

motion. Moreover, it is important that the images are acquired in the same

cardiac phase. Therefore, if there is high variation in the length of the cardiac

cycle, then imaging during systole may improve phase consistency.

For T2* estimation in the heart, dark-blood preparation is utilized to minimize the

effects of moving blood. Such dark-blood protocols produce more homogeneous

appearance and more accurate T2* estimates[19].

Installation

Prerequisite scanner software baseline

The required baseline for this software is:

VD13A (WIP 780): N4_VD13A_LATEST_20120616_P16 (SP4)

Installation of sequence / ICE files

- Copy installation folder “CD_contents_780” (VD13A) into a temporary folder

on the scanner.

- Double-click the “__InstallFiles_TXMapping.bat” file to copy the

sequence/ICE files to appropriate directories. Please check the output to

ensure that all files have been copied across properly.

If this is a reinstallation then the ICE dll’s may not install properly. If this happens,

please reboot the scanner and try again.

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Protocols

This package delivers protocols targeting heart T1, T2, T2* mapping. The

protocols for heart are ECG-triggered protocols. These protocols should be used

with breathholding and the trigger delay should be adjusted so that data is

acquired during the diastolic period of cardiac motion.

Import of protocols

With reference to Figure 18:

Open the EXAM EXPLORER and select the USER tree, press the right

mouse button and select the dialog “Exam Explorer Import”.

In the next dialog window, select “Import” and the appropriate drive where the

protocol file (with extension “.edx”) is located. This can be found in the folder

“protocols” in the installation folder.

Import the protocols, which will appear as a new element at the bottom of the

USER tree.

The inserted protocols are shown in Figure 19, and discussed below.

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Figure 18: Importing protocols

T1 mapping:

T2 mapping:

T2* mapping:

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Figure 19. Recommended protocols for T1, T2, and T2* mapping.

T1 mapping protocols

pre-con_MOLLI_5(3)3_192mat (~8 second breath hold)

Use pre-contrast with fast heart rates (> 90 bpm). The 5(3)3 nomenclature refers

to 5 acquisition heartbeats, followed by 3 recovery heartbeats, then a further 3

acquisition heartbeats. This is faster than the original MOLLI 3(3)3(3)5

configuration, and the resulting T1 estimate is less dependent on heart rate. The

192 matrix is to minimize the readout time to reduce blurring during fast heart

rates.

post-con_MOLLI_4(1)3(1)2_192mat (~8 second breath hold)

Use post-contrast with fast heart rates (> 90 bpm). The shorter T1 values post

contrast mean that less recovery time is necessary between acquisition periods.

The 192 matrix is to minimize the readout time to reduce blurring during fast

heart rates.

pre-con_MOLLI_5(3)3_256mat (~10 second breath hold)

Use pre-contrast with slower heart rates (< 90 bpm). This is similar to “pre-

con_MOLLI_5(3)3_192mat”, except a 256 matrix can be acquired given the

longer quiescent period associated with a slower heart rate.

post-con_MOLLI_4(1)3(1)2_256mat (~10 second breath hold)

Use post-contrast with slower heart rates (< 90 bpm). This is similar to “pre-

con_MOLLI_5(3)3_192mat”, except a 256 matrix can be acquired given the

longer quiescent period associated with a slower heart rate.

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MOLLI_5(3)3(3)5_256mat (~15 second breath hold)

This is the original MOLLI protocols described in Ref. 3, and is included for

consistency. Note that this protocol will produce slightly different (larger) T1

estimates than the counterpart in WIP 732B because of the new adiabatic

inversion pulse and the adiabatic correction factor.

T2 mapping protocols

T2_3pt_3recovHB_gre (~11 second breath hold)

This involves 3 T2 preparations (0, 25 and 55 ms) separated by recovery periods

of 3 heart beats. The gradient echo readout is recommended for more accurate

T2 estimates with less dependence on T1. The gradient echo readout is also

more robust to artifacts, but offers a lower SNR than the TrueFISP counterpart.

T2_3pt_3recovHB_trufi (~11 second breath hold)

This uses the identical acquisition strategy to the previous sequence, but with a

TrueFISP readout. This protocol is included for consistency with previous version

of this WIP, and should be used if a higher SNR is required.

T2* mapping protocols

T2star_8echo_db_gre_1recovHB (~16 second breath hold)

A segmented 8 echo monopolar gradient echo readout is used with a dark blood

preparation pulse to sample the T2* decay. Similar to T2star_8echo_db_gre

except a recovery heartbeat is inserted between each segment for more

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consistent blood/artifact suppression. This protocol also includes iPAT2, fat

suppression and a larger flip angle. Recommended for 3T systems.

T2star_8echo_db_gre (~16 second breath hold)

This protocol remains unchanged from the previous WIP version. Recommended

for 1.5T systems.

User feedback

The authors would be grateful for feedback from collaborators using this WIP. In

particular, any comments on the following items would be of high interest:

Clinical applications

General performance and effectiveness of the package

Specific protocol improvement

Suggestions for addition and/or removal of features

In addition, DICOM images or clinical case studies using this WIP package are

very welcome.

References

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with Cardiomyopathies: When and Why. Herz 2000;25(4):384-391-391.

2. Ugander M, Bagi PS, Oki AJ, Chen B, Hsu L-Y, Aletras AH, Shah S, Greiser

A, Kellman P, Arai AE. Quantitative T1-maps delineate myocardium at risk

as accurately as T2-maps - experimental validation with microspheres.

Journal of Cardiovascular Magnetic Resonance 2011;13(Supplement 1):62.

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3. Messroghli DR, Radjenovic A, Kozerke S, Higgins DM, Sivananthan MU,

Ridgway JP. Modified Look-Locker inversion recovery (MOLLI) for high-

resolution T1 mapping of the heart. Magn Reson Med 2004; 52:141–146.

4. Messroghli DR, Greiser A, Fröhlich M, Dietz R, Schulz-Menger J.

Optimization and Validation of a Fully-Integrated Pulse Sequence for

Modified Look-Locker Inversion-Recovery (MOLLI) T1 Mapping of the Heart.

J Magn Reson Imag 2007; 26:1081–1086.

5. Xue H, Shah S, Greiser A, Guetter C, Chefd’hotel C, Zuehlsdorff S, Guerhing

J, Kellman P. Improved motion correction using image registration based on

variational synthetic image estimation: application to inline T1 mapping of

myocardium, Journal of Cardiovascular Magnetic Resonance 2011, 13(Suppl

1):P21

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Zuehlsdorff S, Guehring J, Kellman P. Motion correction for myocardial T1

mapping using image registration with synthetic image estimation. Magn

Reson Med. 2012 Jun;67(6):1644-55

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fraction mapping in the myocardium, part 1: evaluation of an automated

method. J Cardiovasc Magn Reson. 2012 Sep 10;14:63

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Ugander M, Arai AE. Extracellular volume fraction mapping in the

myocardium, part 2: initial clinical experience J Cardiovasc Magn Reson.

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Bock P, Dietz R, Friedrich MG, Schulz-Menger J: Diagnostic performance of

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myocardial injury: utility in acute coronary syndrome and other clinical

scenarios. Circulation 2008, 118:795-796.

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improves diagnostic confidence in edema imaging in acute myocardial

infarction compared to turbo spin echo. Magn Reson Med 2007, 57:891-897.

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Acknowledgements

The authors gratefully acknowledge the invaluable collaboration with Dr. Peter

Kellman and Hui Xue (NIH, Bethesda, MD), Dr. Martin Ugander (Karolinska

University Hospital, Lund, Sweden), Dr. Daniel Messroghli and Cardiovacular

MRI group at Charité (Berlin-Buch, Germany), Dr. Eric Schelbert (UPMC,

Pittsburgh, PA), Dr. Orlando Simonetti (Ohio State University, Columbus, OH),

Dr. David Firmin, Dr. Dudley Pennell, Dr. Taigang He (Royal Brompton Hospital,

London, UK). Moreover, authors are also thankful to many Siemens colleagues

including Dr. Wolfgang Rehwald, Peter Weale, Dr. Xiaoming Bi, Saurabh Shah,

Dr. Jens Guehring, Dr. Aurelien Stalder, Dr Marie-Pierre Jolly and Dr. Sven

Zuehlsdorff.

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Appendix 1: Hints for the use of the Cardiac Shim

For TrueFISP based mapping protocols, in particular at 3T the use of the Cardiac

Shim can be beneficial to reduce off-resonance artefacts. With VD11D and

VD13A the Cardiac Shim is provided as a product option, as part of the

adjustment framework. In the protocols provided with this package, the Cardiac

Shim can be activated as the shim option in the “Adjustments” subcard. While its

use can help a lot to improve the results, some caution is indicated regarding the

workflow if the procedure is used outside the Dot framework. The adjustment

volume that shall be adopted for covering the heart volume is not automatically

propagated to new successive protocols if they are dragged from the exam

database to the exam queue. Therefore, it is recommended to check the

adjstment volume before a mapping protocol is started. The display of the

adjustment volume represented as a green box can be activated in the graphical

slice positioning tool in the “View” dropdown menue. The best approach to

propagate the adopted adjustment volume from a previous scan to a protocol

open for editing is to right click on the desired source protocol in the scan queue

and select “Copy Parameter” > “Adjust volume” or if desired “Slices &

Adjustvolumes”.

Figure 20: Propagation of the adjustment volume to the open protocol

applications guide quantitative cardiac parameter mapping ...10.1007/s10554-016-1034... ·...

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