Clinical application and Protocols: Cardiovascular ... · Clinical application and Protocols: Cardiovascular vascular imaging. Saifhon Admontree B.Sc.(Radiological Technology) Mahidol

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Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

Clinical application and Protocols: Cardiovascular vascular imaging.

Saifhon Admontree

B.Sc.(Radiological Technology) Mahidol University

M.Sc.(Medical Imaging) Chulalongkorn University

AIMC, Ramathibodi Hospital


Disclosure This presentation slide supported by Bayer Thai


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Patient preparation in Cardiac CTA Cardiac CT Angiography technology Contrast protocols and timing Image Reconstruction Protocols Dual Energy CT applications in Cardiac CTA Radiation dose considerations in Cardiac CTA


Patient Preparation Protocol

Patient safety

Allergy (anaphylaxis)

Renal insufficiency

Claustrophobia

Pregnancy

Image quality

Metallic artefacts

Motion artefacts

Breath hold

Gregory Kicska. Patient preparation and coronary CTA techniques. pdf. Aviable from; http://www.nasci.org/Portals/4/Meetings/RSSA/Cardiac/CTA/2013/Kicska.pdf


• งดอาหาร และเครองดมทกระตนการท างานของหวใจ เชน ชา กาแฟ อยางนอย 4-6 ชวโมง

• กนยาลดการเตนของหวใจ พจารณาโดยรงสแพทยและแพทยเจาของไข

• สวมใสเสอผาทสบายและเชดท าความสะอาดบรเวณทตด electrode

• หลกเลยงการตด electrode ต าแหนงกระดก เพราะจะกนสญญาณคลนไฟฟาหวใจสงผลใหกราฟของelectrocardiogram ไมชดเจน

การจดทาผปวย

• ผปวยนอนหงายราบกบเตยง ชแขนขนเหนอศรษะ ในทาทสบาย

• จดผปวยใหอยกงกลางต าแหนง Iso-center

• ฝกซอมผปวยใหกลนใจนงทสด

• บรรเทาความวตกกงวลของผปวย

• ฉดสารละลายน าเกลอเพอทดสอบหลอดเลอด กอนการฉดสารทบรงส

• วางเสอตะกวเพอปองกนอนตรายของรงสตออวยวะสบพนธ (Gonad Shielding) ในผปวยวยเจรญพนธทกครง

เตรยมตวกอนตรวจ

Preparation: 24-1 hr pre-exam


Cardiac CT Angiography technology

Review of Radiology Physics: A Handbook for Teachers and Students - 1.1.1 Slide 1

Dual Energy CT scanners

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16-row MDCT (A) 64-row MDCT (B) 320-row MDCT (C)

Example illustrating the improved depiction of distal coronary artery branches (white arrows) using 64-row (Panel B ) and 320-row CT (Panel C) in a 58-year-old female patient.

M. Dewey, Cardiac CT, DOI 10.1007/978-3-642-41883-9_6, © Springer-Verlag Berlin Heidelberg 2014

Technical Requirements for Cardiac CTA: CT scanner with at least

64 simultaneous rows.


Wide beam (320-detector row) CT scanner

160mm in z-coverage

(320x0.5mm)

Enable volumetric imaging

within one cardiac cycle.

Short rotation time of 0.35s.

320- detector row CT scanner

specifications:

Cardiac CT Angiography technology (Cont’d)

Technical Aspects of Cardiac CT: Improving Speed of volume coverage.

Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land Cardiac CT Angiography technology (Cont’d)

160mm z-coverage (320-MDCT)

Entire heart can be captured in

single heartbeat.

Eliminate Stair-Step and

Misalignment Artifacts

Increase temporal resolution

Wide beam (320-detector row) CT scanner

Advantages of 320- detector row CT in

cardiovascular imaging;

Technical Aspects of Cardiac CT: Improving Speed of volume coverage.


Technical Aspects of Cardiac CT: Improving spatial resolution.

Optimise pixel size (pixel size = FOV/ matrix)


S. Edyvean. Technical Aspects of Cardiac CT.ppt.


Effect of the reconstruction fi eld of view on the image quality of coronary artery reconstructions. Threedimensional reconstructions of the LAD show the relevantly lower spatial resolution obtained using

the 320-mm reconstruction field of view ( Panel A ), when compared with the smaller 180-mm reconstruction field of view ( Panel B ), as illustrated by the mid-LAD ( arrow ) and the first diagonal branch

( arrowhead ). M. Dewey, Cardiac CT, DOI 10.1007/978-3-642-41883-9_6, © Springer-Verlag Berlin Heidelberg 2014

FOV 320mm FOV 180mm

Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land Coronary CT angiography Technique (cont’d)

Bruce Precious. Protocols in Cardiac CT.2016 ppt.

Technical Aspects of Cardiac CT: Improving temporal resolution.

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Ibrahim Danad, Zahi A. Fayad, Martin J. Willemink, James K. Min. New Application of Cardiac CT. JACC: CARDIOVASCULAR IMAGING. 2015 June; 8(6):710–23.

The principles of DECT are based largely on;

Photoelectric effect and can be achieved by exploiting the

energy dependent attenuation of materials

Enables distinct differentiation between 2 basis materials,

based on dissimilar tissue characteristics with respect to

their energy dependent x-ray attenuation.


Technical Aspects of Cardiac CT: Dual Energy Computed Tomography


Dual source scanner (a): two x-ray sources, which are operated at different energies.

Figure 1. a–d. Illustration showing different types of dual energy CT scanners.

Dual spin technology (c): using a volume scanner, the patient is initially scanned at one energy level (135 kVp) and immediately scanned in the same anatomic location using a different energy level (80 kVp).

Dual layer/ spectral detector CT (SDCT) (d):

Rapid kVp switching (b): each x-ray projection, kVp is rapidly switched between low (80 kVp) and high energy (140 kVp) levels.



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Figure 2. Dual layer or spectral detector CT (SDCT)

Single X-ray source


Two layers of Spectral detectors CT,

Top layer (yttrium-based garnet scintillator) absorbing low energy photons,

Bottom layer(gadolinium-oxysulphide) absorbing high energy photons.

Differentiate materials of

different effective atomic numbers.


Types of images from the detector-based spectral CT scanner

Rassouli N, Etesami M, Dhanantwari A, Rajiah P. Detector-based spectral CT with a novel dual-layer technology: principles and applications. Insights Imaging 2017;8:589-98.



Dual energy CT applications in cardiovascular imaging;

Virtual monoenergetic images are useful for boosting contrast and reducing artifacts in suboptimal studies.

Rassouli N, Etesami M, Dhanantwari A, Rajiah P. Detector-based spectral CT with a novel dual-layer technology: principles and applications. Insights Imaging 2017;8:589-98.

(b) 45-keV virtual monoenergetic image (VMI) at the same level shows significant improvement in the contrast attenuation, especially in the left atrium (red arrow).

(a) Coronal 120-kVp shows poor contrast opacification of the vascular structures, particularly the left atrium (yellow arrow), due to contrast extravasation during the scanning.



Virtual monoenergetic images are useful for boosting contrast and reducing artifacts in suboptimal studies, obviating the need for a repeat contrast injection.

Prabhakar Rajiah, Suhny Abbara and Sandra Simon Halliburton. Spectral detector CT for cardiovascular applications. Diagn Interv Radiol DOI 10.5152/dir.2016.1625.

Conventional polyenergetic CT image obtained for evaluation of pulmonary

embolism with poor vascular enhancement due to contrast extravasation

Virtual 40 keV monoenergetic image shows significantly improved

enhancement permitting evaluation of the pulmonary arteries

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Dual energy CT applications in cardiovascular imaging; Virtual unenhanced image (c) created from spectral data obtained just after contrast injection. Like the true unenhanced image at approximately the same level, the virtual unenhanced image shows no contrast in the aorta and other vascular structures.


(a) True unenhanced image (b) Contrast-enhanced image (c) Virtual unenhanced image


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Chandra N, Langan DA. Gemstone Detector: Dual Energy Imaging via Fast kVp Switching in Dual Energy CT in Clinical Practice. London New York: Springer Heidelberg Dordrecht 2011.


Good agreement of virtual unenhanced images (B) and true conventional non-contrast (A) calcium scoring scans (CAC).

A B



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Reduction in calcium blooming artifact.



(A) significant calcium blooming

(green) in coronary artery, with luminal area of 3.5 mm²

(A) (B)

(B) 160 keV image with reduced

blooming and better defined lumen with area of 7.4 mm².


Basic Technical Concepts of CT Angiography:

Contrast administration – arterial opacification.

Computed Tomography – Multidetector (64MDCT)

Time scan acquisition during the arterial phase.

Cardiac CT - ECG synchronization.

Contrast protocols and timing


CT angiography contrast administration:

Proportional to the iodine administration rate

Iodine concentration of contrast medium

Injection flow rate (mL/s)

Injection duration (larger volume of contrast)

Contrast protocols and timing (cont’d)

Fleischmann, D. Radiol Clin N Am, 2010; 48


Iodine concentration of contrast medium

Simulated contrast enhancement

curve of the abdominal aorta

(125 ml of contrast at 4mL/s,

three CM concentrations)

Bae KT. Radiology 2010;256:32

Higher Iodine concentration increased arterial enhancement


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Injection flow rate (mL/s); higher flow rate of CM

Increased arterial enhancement,

Duration decreases.

Contrast protocols and timing (cont’d) Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

Determine the contrast arrival time;

Bolus tracking

Timing bolus

Perform diagnostic scan near peak enhancement

achieved with the contrast bolus

in the target vessel.

CT angiography: basic strategy



Scan Timing Methods;

Timing bolus

Select target location from scout topogram.

Inject small test-bolus (15 – 20 mL contrast).

Acquire low-dose dynamic scan at specified location during injection.

ROI in target structure.

Measure time-attenuation curve

Contrast material arrival time in aortic root


Scan Timing Methods;

Bolus Triggering (or Bolus Tracking)

Select trigger location

Acquire reference image

Place ROI in vascular structure of interest

Inject diagnostic contrast bolus in target structure

Acquire low-dose dynamic scans, monitor attenuation in ROI

Start scan when desired threshold reached Fleischmann, D. Radiol Clin N Am, 2010; 48: 237KT. Radiology 2010;256:32



Saline chaser

Pushes contrast in tubing and peripheral veins into central veins

40 – 50 cc, allows reduction in contrast volume

Increases arterial peak attenuation

Reduced streak artifacts from veins and right heart

Simpler to implement with dual head injectors



Intermediate attenuation in right heart to minimize contrast related streak artifacts but allow visualization of right heart structures.

High right heart attenuated

Streak artifacts

Low right heart attenuated

No streak artifacts RH structures not seen

Intermediate right heart attenuated

No streak artifacts RH structures visible

Kerl JM, Radiology 2008;247(2):356


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Use of lower voltage results in stronger contrast enhancement (such as 100 and 80 kVp results in higher CT attenuation than 120 kVp), because;

X-ray output energy at these

low voltages is closer to the

iodine k edge of 33 keV

Improve vascular and

parenchymal enhancement.



Higher contrast concentrations- higher arterial enhancement

Higher flow rate 4 – 5 mL/s

Saline chaser

Lower kVp when possible

Timing bolus or bolus tracking

CT angiography Summary points




Cardiac CT Angiography Protocol: Patient positioning for cardiac CT


Start and End location

Carina to Cardiac apex.

Scan time delayed

Prospective ECG gating Technique.

Following Breath Exercise the system will automatically select the target phase.

HR ≤ 65bpm = 75%

HR > 66bpm = 40%

Cardiac CT Angiography Protocol: Calcium Scoring Technique


Calcium Scoring

Technique;

Breath exercise

Note: ECG gating technique was used in Cardiac study.

Calcium Scoring Technique (cont’d) Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

Cardiac Analysis: Calcium quantification methods

Calcium Scoring Technique (cont’d)

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Cardiac Analysis: Calcium quantification methods

Agatston volume mass score

Calcium Scoring Technique (cont’d) Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

What is Computed Tomography Angiography?

CT angiography is a type of medical exam that combines a CT scan with an injection of a contrast media to visualize arterial and venous vessels throughout the body.

Cardiac CT Angiography Protocol: Coronary CT angiography Technique


ECG synchronization

use data at same point in cardiac cycle to create image.

Coronary rest period = low coronary motion mid-late diastole.

Coronary CT angiography Technique (cont’d) Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

Basic Principle of Cardiac CT ECG synchronization

Retrospective ECG triggering.

Prospective ECG triggering.

Coronary CT angiography Technique (cont’d)


ECG synchronization Retrospective ECG gating –ECG dose modulation

use data at same point in cardiac cycle to create image. Beam modulated

max mA min mA

Data from entire R – R Overall dose less (40%)

max mA

min mA


ECG synchronization Prospective ECG gating

Axial step-and-shoot, half-scan acquisition Trigger from ECG

beam completely off trigger – completely on

max mA beam on time

60 – 80% less dose


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Intravenous contrast administration

Contrast volume is 1-1.1 cc per kilogram of body weight, dual head injector was used.

Based on 300-370 mgI/mL concentration.

Injection, flow rate 5-6 cc/sec plus NSS 40 cc.


Example of scanning Parameters in Coronary CTA (Toshiba CT scanner)

kVp / mA / Rotation time (sec) /Pith

100 kVp / 300-500mA or AEC/ 0.33-0.5 sec/ Pith 0.2 (Scan with overlapping pitch)

Detector collimation (mm) Helical : 0.5x80, 0.6x64,0.5x160 Axial Volume Mode: 0.5x320

Slice thickness/Interval (mm) 0.5-0.75mm/0.25-0.5mm

DFOV (mm) 180-250 mm (Small FOV)



Start and End location

Carina to Cardiac apex.

Scan time delayed

Bolus tracking technique,

ROI was placed at Descending Aorta


Beyond basic CTA protocol; “Cardiac Mass” ECG gating and add delayed phase 90‐120 seconds.


Standard coronary CTA protocol Delayed phase coronary CTA protocol

Bruce Precious. Protocols in Cardiac CT.2016 ppt.


Image Reconstruction Protocols

Post-processing

techniques

1) Multiplanar Reconstruction (MPR) and MIP 2) Volume Rendering Technique (VRT) 3) Curve Reformation 4) Cardiac Function Analysis

The advent of MDCT particularly with scanners having 64 or more detectors, has continued to improve temporal resolution and allows the acquisition of “isotropic voxels”


• Postprocessing technique that takes the highest-attenuation voxel in a predetermined slab of data and projects it from the user toward the viewing screen, resulting in a two-dimensional image.

• Only the highest-attenuation objects, typically contrast material and bone, are preferentially displayed and retained in the image.

Maximum Intensity Projection(MIP)

Image Reconstruction Protocols (cont’d)

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Multiplanar Reconstruction (MPR)

2D Technique Used (Cardiac CTA study)

5 mm interval 2mm of axial, coronal, sagittal, RAO and LAO Maximum Intensity Projection (MIP) reconstruction.

Axial: 5 mm interval 2mm

Image Reconstruction Protocols ( Cont’d)











5 mm interval 2mm of axial, coronal Maximum Intensity Projection (MIP) reconstruction.




5 mm interval 2mm of axial, coronal, sagittal, RAO and LAO Maximum Intensity Projection (MIP) reconstruction.

Coronal(A) and Sagittal (B): 5 mm interval 2mm

A B


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Multiplanar Reconstruction (MPR) and MIP



5 mm interval 2mm of LAO Maximum Intensity Projection (MIP) reconstruction


Multiplanar Reconstruction (MPR) and MIP


2D Technique Used

(Cardiac CTA study)

5 mm interval 2mm of a RAO Maximum Intensity Projection (MIP) reconstruction.




5 mm interval 2mm of a Short Axis Maximum Intensity Projection (MIP) reconstruction




-Short Axis, -2,3 or 4 Chamber Views reconstruction.

Short Axis (MIP): 5 mm interval 2mm




2D Technique Used

(Cardiac CTA study)

5 mm interval 2mm of a Short Axis Maximum Intensity Projection (MIP) reconstruction





2 CH views reconstruction


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5 mm interval 2mm of a 3 chamber view, Maximum Intensity Projection (MIP) reconstruction








3D Reconstruction: Volume Rendering (VR)


• 3D technique in which the CT attenuation values for each voxel can be assigned a specific color,

• Provides the depth and spatial information and

• Facilitate surface evaluation of the heart and coronary arteries.


3D Technique Used VR Projection/3D rendering



• Because normal coronary arteries are often tortuous, accurate evaluation requires assessment of the entire vessel along its center line.

• Curved reformatted images provide this capability by sampling a given volume (ie, artery) along a predefined curved anatomic plane.

Curved Reformation


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Curve reformat of coronary artery vessel (RCA, LAD,LCX).

LAD LAD

LCX LCX

Curve Reformation

Image Reconstruction Protocols (cont’d) Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land

Workstation with automatic curved multiplanar reformation and three-dimensional data segmentation and analysis capabilities.


Cardiac Analysis: Cardiac Function Analysis



Cardiac Analysis: Cardiac Function Analysis


The 17-segment model was recommend using for reporting myocardial segment.

Cardiac Analysis:

Myocardium Analysis


Cardiac Analysis:

Myocardium Analysis

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Faculty of Medicine Ramathibodi Hospital Mahidol University: Wisdom of the Land Cardiac Analysis:

TAVI (Transcatheter Aortic Valve Implantation) protocol



Radiation Dose consideration in Cardiac CTA


76 CTDIvol and DLP displayed on monitor are based on 32-cm body phantom.

Conversion factor (k= 0.014 mSv/mGy.cm) was applied to estimate the effective dose (E) from dose length product (DLP).

Mean ± SD values and the third quartile or 75th percentile of CTDIvol, DLP and effective

dose of coronary calcium scoring and cardiac CTA in retrospective ECG- gating technique.


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Wide beam detector (320-MDCT) 64-MDCT

Volumetric imaging of whole heart and coronary vessels can be imaged within single heartbeat

Mean effective dose range from 4.4 to 7.2 mSv.

Several heartbeats were acquired to capture the entire heart leading to high radiation dose

Mean effective dose range from 4.1 to 20.0 mSv.

The mean Effective Dose (E) in Cardiac CT Angiography from literature review

Radiation Dose consideration in Cardiac CTA ( Cont’d)


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The patient dose reduction in Cardiac CTA should be considered by means of ;

1) Rigorous scan coverage fit to the heart or according to the clinical consideration.

2) Tube voltage reduction to increase the photoelectric effect of contrast medium and tissue.

3) Use iterative reconstruction algorithm. 4) Anatomical tube current modulation. 5) ECG- tube current modulation and prospectively triggered CT

angiography in case of stable low heart rate. 6) DRLs was used as the optimization tool to reduce the radiation

dose, while as maintain acceptably level of image quality.


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The patient dose reduction in Cardiac CTA should be considered by means of ; ECG- tube current modulation.



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The patient dose reduction in Cardiac CTA should be considered by means of ; prospectively triggered CT angiography in case of stable low heart rate.


% 50

RR-interval

ECG-triggered tube modulation

Continuous scanning

Prospective ECG-triggering


Image noise reduction on axial images cardiac CT reconstructed with adaptive iterative reconstruction (Panel B ) in comparison to standard filtered back projection (Panel A ).

(Images courtesy of Kazuhiro Katada, Fujity University)


The patient dose reduction in Cardiac CTA should be considered by means of ; iterative reconstruction .


1. Ibrahim Danad, Zahi A. Fayad, Martin J. Willemink, James K. Min. New Application of Cardiac CT. JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 6, JUNE 2015:710–23.

2. CT Coronary Angiography: 256-Slice and 320-Detector Row Scanners.

3. Wang M, Qi HT, Wang XM, Wang T, Chen JH, Liu C. Dose performance and image quality: dual source CT versus single source CT in cardiac CT angiography. Eur J Radiol. 2009; 72:396–400.[PubMed: 18835119]

4. Atif Khan, Faisal Khosa, Khurram Nasir, Aya Yassin, and Melvin E. Clouse. Comparison of Radiation Dose and Image Quality: 320-MDCT Versus 64-MDCT Coronary Angiography. AJR Am J Roentgenol. 2011 July ; 197(1): 163–168.

5. Prabhakar Rajiah, Suhny Abbara and Sandra Simon Halliburton. Spectral detector CT for cardiovascular applications. Diagn Interv Radiol DOI 10.5152/dir.2016.1625.

6. Baumller et al. Dual-Source versus 64-Section CT Coronary Angiography at Lower Heart Rates: Comparison of Accuracy and Radiation Dose. Radiology: Volume 253: Number 1—October 2009.

7. J Rixe, G Conradi, A Rolf, A Schmermund, A Magedanz, et al. Radiation dose exposure of computed tomography coronary angiography: comparison of dual-source, 16-slice and 64. BMJ: / Volume 95.

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8. Hirai, J. Horiguchi, C. Fujioka, M. Kiguchi. Prospective versus Retrospective ECG-gated 64-Detector Coronary CT Angiography: Assessment of Image Quality, Stenosis, and Radiation Dose. Radiology: Volume 248: Number 2—August 2008.

9. Frank J. Rybicki, Hansel J. Otero, Michael L. Steigner, Gabriel Vorobiof et al. Initial evaluation of coronary images from 320-detector row computed tomography. Int J Cardiovasc Imaging (2008) 24:535–546.

10. Dianna M.E. Bardo* and Paul Brown. Cardiac Multidetector Computed Tomography: Basic Physics of Image

11. Acquisition and Clinical Applications. Current Cardiology Reviews, 2008, Vol. 4, No. 3.

12. Gregory Kicska. Patient preparation and coronary CTA techniques. pdf. Aviable from;http://www.nasci.org/Portals/4/Meetings/RSSA/Cardiac/CTA/2013/Kicska.pdf. Access: 6 March 2018.

13. Cardiac and CT angiography techniques Cardiovascular Boot Camp. NASCI 40th Annual Meeting October 13, 2011.

14. Kyongtae T. Bae. Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches. Radiology 2010;256:32-61.

15. Rassouli N, Etesami M, Dhanantwari A, Rajiah P. Detector-based spectral CT with a novel dual-layer technology: principles and applications. Insights Imaging 2017;8:589-98

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Clinical application and Protocols: Cardiovascular ... · Clinical application and Protocols: Cardiovascular vascular imaging. Saifhon Admontree B.Sc.(Radiological Technology) Mahidol

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