ct scanner presented by: dr m a oghabian medical physics department, tehran university of medical...
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CT ScannerCT Scanner
Presented by:Presented by:
Dr M A OghabianDr M A Oghabian
Medical Physics Department,Medical Physics Department,
Tehran University of Medical Tehran University of Medical SciencesSciences
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Computed TomographyComputed Tomography
CT uses a rotating x-ray tube, with the beam CT uses a rotating x-ray tube, with the beam in the form of a thin slice (about 1 - 10 mm)in the form of a thin slice (about 1 - 10 mm)
The “image” is a simple array of x-ray The “image” is a simple array of x-ray intensity (Projections), and many hundreds of intensity (Projections), and many hundreds of these are used to make the CT image, which these are used to make the CT image, which is a “slice” through the patientis a “slice” through the patient
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First generation CT ScannerFirst generation CT Scanner(Rotate/Translate Pencil beam)(Rotate/Translate Pencil beam)
180 translational movement180 translational movement 180 Rotary movement180 Rotary movement 160 parallel rays across a 24 cm FOV160 parallel rays across a 24 cm FOV Each 2 slices=4.5 min.Each 2 slices=4.5 min. Processing time=1.5min.Processing time=1.5min.
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Second generation CT scannersSecond generation CT scannersRotate/Translate Narrow fan beam~10 degreeRotate/Translate Narrow fan beam~10 degree
Narrow fan beam~10 degreeNarrow fan beam~10 degree Linear array of 30 detectorsLinear array of 30 detectors 6 linear movement6 linear movement 6 rotary movement6 rotary movement Scan time~ 18 Sec.Scan time~ 18 Sec.
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Third generation CT ScannersThird generation CT Scanners(Rotate/Rotate , Wide fan beam)(Rotate/Rotate , Wide fan beam)
Wide fan beamWide fan beam More than 800 detectorsMore than 800 detectors No translational motionNo translational motion Scan time ~ 0.5 Sec.Scan time ~ 0.5 Sec.
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44thth Generation CT Scanners Generation CT ScannersRotate/StationaryRotate/Stationary
Fan beam geometryFan beam geometry More than 4800 detectorsMore than 4800 detectors
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Electron Beam Computed Tomography Electron Beam Computed Tomography (EBCT)(EBCT)
- x-ray source is not x-ray - x-ray source is not x-ray tube but a focused, tube but a focused, steered, microwave-steered, microwave-accelerated EB incident accelerated EB incident on a tungsten target.on a tungsten target.
- It has no moving parts .- It has no moving parts .- Target covers one-half - Target covers one-half
of the imaging circle; of the imaging circle; detector array covers detector array covers the other half.the other half.
- Images in less than - Images in less than 50ms.50ms.
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EBCT(CONT’D)EBCT(CONT’D) There are 4 targets and 4 There are 4 targets and 4
detector arrays resulting in 4 detector arrays resulting in 4 contiguous images contiguous images simultaneously.simultaneously.
The detector array may The detector array may consists of two separate rings consists of two separate rings
Each solid -state detector Each solid -state detector consists of a luminescent consists of a luminescent crystal and cadmium crystal and cadmium tungstate coupled with silicon tungstate coupled with silicon photodiodes.photodiodes.
Heat dissipation is no problem Heat dissipation is no problem in EBCT.in EBCT.
Developed for fast imaging.Developed for fast imaging. Used for cardiac imagingUsed for cardiac imaging
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A look inside a rotate/rotate CTA look inside a rotate/rotate CT
X-Ray Tube
Detector Arrayand Collimator
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Comparison of data acquisition for axial and helical technologies.
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Reciprocating rotation (A) versus fast continuous rotation using Reciprocating rotation (A) versus fast continuous rotation using slip-ring technology (B)slip-ring technology (B)
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A Look Inside a Slip Ring CT A Look Inside a Slip Ring CT
X-RayTube
Detector Array
Slip Ring
Note: how most
of theelectronics
isplaced on
the rotatinggantry
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(A) Pitch =1 (B) Pitch = 2
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Comparison of the accuracy of 3D reconstruction for Comparison of the accuracy of 3D reconstruction for conventional (A) and spiral/helical (B) CT scanning.conventional (A) and spiral/helical (B) CT scanning.
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More New CT Features:More New CT Features:
Multislice ScanningMultislice Scanning
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Multislice CT, where up to 64 variable Multislice CT, where up to 64 variable thickness slices can be collected thickness slices can be collected simultaneously simultaneously
CT fluoroscopy, where the patient is CT fluoroscopy, where the patient is stationary, but the tube continues to stationary, but the tube continues to rotate rotate
3-dimensional CT and CT endoscopy 3-dimensional CT and CT endoscopy
Clinical Benefits Of Multi-SliceClinical Benefits Of Multi-SliceMulti-phase Organ StudiesMulti-phase Organ Studies
Liver – Pancreas Arterial, Renal NephrogramLiver – Pancreas Arterial, Renal Nephrogram
Arterial Phase ScanningArterial Phase Scanning Hypervascular TumorsHypervascular Tumors
CT AngiographyCT Angiography Multi-Plane Reconstructions, Contrast EnhancementMulti-Plane Reconstructions, Contrast Enhancement
New CT ApplicationsNew CT Applications CT fluoroscopyCT fluoroscopy CT ColonographyCT Colonography Cardiac: morphology, functionCardiac: morphology, function Advanced Lung AnalysisAdvanced Lung Analysis
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Detector ConfigurationsDetector Configurations
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 1.25 mm Detector Configuration4 x 1.25 mm Detector Configuration
16-row Mosaic Detector16-row Mosaic Detector
DiodeDiode FET Switching ArrayFET Switching Array
Flex Connector AFlex Connector A Flex Connector BFlex Connector B
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Detector ConfigurationsDetector Configurations
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 2.5 mm Detector Configuration4 x 2.5 mm Detector Configuration
16-row Mosaic Detector16-row Mosaic Detector
DiodeDiode FET Switching ArrayFET Switching Array
Flex Connector AFlex Connector A Flex Connector BFlex Connector B
X-ray Tube Focal Spot
X-ray Beam Collimator
4 x 3.75 mm Detector Configuration4 x 3.75 mm Detector Configuration
Detector ConfigurationsDetector Configurations
16-row Mosaic Detector16-row Mosaic Detector
DiodeDiode FET Switching ArrayFET Switching Array
Flex Connector AFlex Connector A Flex Connector BFlex Connector B
Detector ConfigurationsDetector ConfigurationsX-ray Tube Focal Spot
X-ray Beam Collimator
4 x 5.0 mm Detector Configuration4 x 5.0 mm Detector Configuration
16-row Mosaic Detector16-row Mosaic Detector
DiodeDiode FET Switching ArrayFET Switching Array
Flex Connector AFlex Connector A Flex Connector BFlex Connector B
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0,5mm
1mm
2,5mm
5mm
Multi slice CT collimationMulti slice CT collimation
Speed: Single vs. 4 SliceSpeed: Single vs. 4 Slice
235 mm5 mm
8240
255 mm5 mm
9300
174,725
ChestCoverage ThicknessTime (s)mAAbdomen/PelvisCoverageThicknessTime (s)mA
Scan Time (s)Tube Load (mAs)
Single Slice
235 mm5 mm
31240
255 mm5 mm
34300
6517,720
4 slice
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MULTISLICE SPIRAL CTMULTISLICE SPIRAL CT
Introduced at the 1998.Introduced at the 1998. They are based multiple They are based multiple
detector. detector. rows ranging between 8, rows ranging between 8, 16, 24, 32 and 64 depending on the 16, 24, 32 and 64 depending on the manufacturer.manufacturer.
The overall goal is to improve The overall goal is to improve the volume coverage speed the volume coverage speed performance.performance.
Complete x-ray tube/detector Complete x-ray tube/detector
array rotation in less than 1s.array rotation in less than 1s.
Partial scan images can be Partial scan images can be obtained in approximately obtained in approximately 100ms.100ms.
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MULTISLICE IMAGING(CONT’D)MULTISLICE IMAGING(CONT’D)
ADVANTAGESADVANTAGES Improved spatial resolution this advantage improved MPR,3D Improved spatial resolution this advantage improved MPR,3D
images.images. Reduction of radiation exposure.Reduction of radiation exposure. Motion artifacts are greatly reduced.Motion artifacts are greatly reduced. Patient breathhold is much less demanding.Patient breathhold is much less demanding. Imaging larger z-axis volume in less time is possible with MI.Imaging larger z-axis volume in less time is possible with MI. Less contrast medium required.Less contrast medium required. Because of imaging speed, coronary artery is comparable Because of imaging speed, coronary artery is comparable
with EBCT.with EBCT. Improved accuracy in needle placement CT fluoroscopy.Improved accuracy in needle placement CT fluoroscopy.
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Real Time GuidanceReal Time Guidance Great Image QualityGreat Image Quality Low RiskLow Risk Faster ProceduresFaster Procedures
CT FluoroscopyCT Fluoroscopy
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REAL-TIME CT FLUOLOROSCOPYREAL-TIME CT FLUOLOROSCOPY
CT fluoroscopy acquire CT fluoroscopy acquire dynamic images in real dynamic images in real time.time.
Fast continuous imaging, Fast continuous imaging, fast image reconstruction & fast image reconstruction & continuous image display.continuous image display.
Patient movement is low Patient movement is low during Tube rotation.during Tube rotation.
Fast image Reconstruction Fast image Reconstruction algorithm is required.algorithm is required.
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CT ANGIOGRAPHY (CTA)CT ANGIOGRAPHY (CTA)
CTA allows maximum CTA allows maximum visualization of the visualization of the pulmonary artery and its pulmonary artery and its segmental braches.segmental braches.
CTA requires low kVp CTA requires low kVp and MA, for example and MA, for example 90Kvp/100mA.90Kvp/100mA.
CTA employs MIP and CTA employs MIP and MPR to maximum MPR to maximum advantage.advantage.
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3D Stereo Imaging3D Stereo Imaging
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Enhanced 3D
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CT EndoscopyCT Endoscopy
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CT VIRTUAL REALITY IAMAGINGCT VIRTUAL REALITY IAMAGING
The use of virtual reality is The use of virtual reality is the creation the inner views the creation the inner views of tubular structures.of tubular structures.
Offers both endoluminal and Offers both endoluminal and extra luminal information.extra luminal information.
It reduces complication (eg. It reduces complication (eg. infection and perforation)infection and perforation)..
Four requirements:Four requirements: data acquisitiondata acquisition image processingimage processing 3D rendering3D rendering image display and analysis.image display and analysis.