SUBTRACTION CT ANGIOGRAPHY DR TRAN THI MINH PHUONG
SUBTRACTION CT ANGIOGRAPHY DR. TRAN THI MINH PHUONG DEPARTMENT OF CT-MRI
SUBTRACTION CTA • In subtraction CT angiography (s. CTA), a noncontrast CT acquisition is subtracted from a contrast-enhanced CTA acquisition.
SUBTRACTION CTA • Subtraction is a post-processing technique to eliminate high-density structures, such as bone, metal, calcification, from CT images. • A subtraction dataset is obtained by subtracting a non-contrast acquisition (mask image) from a contrast-enhanced image.
CHALLENGES • Accurate registration of the two datasets is essential. • The (minimal) time delay between the noncontrast and contrast acquisitions can introduce differences between scans due to patient motion or vascular pulsation.
DEDICATED REGISTRATION ALGORITHM • This deformable registration algorithm matches the position of bony structures and calcifications on the mask image to the contrast scan prior to subtraction. • Accordingly, subtracted image data are obtained from which high-density structures have been removed and which can be used for evaluation in conjunction with the conventional contrast-enhanced images.
APPLICATION • Automatically remove bone, calcium and stents • Visualization of the true vessel lumen for better quantification • Whole body CTA, brain CTA, carotids, aorta, run-off • Zero-click workflow
A NUMBER OF CLINICAL APPLICATIONS FOR NEUROLOGICAL CT ANGIOGRAPHY • Cerebral aneurysms — especially close to the bone • Patients with ischemic disease — ICA, basilar artery • Cases with stenosis or occlusion — close to bone • Patients with a clip or coil • Patients with calcification • Patients with hypervascular tumor • Patients scanned from neck to head
SUBTRACTION CT ANGIOGRAPHY OF THE LOWER LIMBS • Reducing the number of nonanalyzable arterial segments compared with DSA. • The ability of the technique to detect significant stenosis is close to that of DSA. • The risk of the negative results observed with nonsubtraction MDCT is reduced without the need for analysis of axial images. • Compared with DSA, subtraction MDCT allows a substantial reduction (2. 4 -fold) in radiation exposure to the patient.
SUBTRACTION CT ANGIOGRAPHY OF THE CORONARY ARTERY • Diagnostic accuracy of conventional coronary CT angiography (CCTAconv) may be compromised by blooming artifacts from calcifications or stents. • Blooming artifacts may be reduced by subtraction coronary CT angiography (CCTAsub) in which non-contrast and contrast CT data sets are subtracted digitally.
CTA Cardiac Subtraction
CTA Cardiac Subtraction (tt)
CONCLUSION • Subtraction CT angiography is enable noninvasive vascular imaging with fine detail, approaching the resolution as seen during invasive DSA. • Reduce the postprocessing workload; Reduce image reconstruction time => Reduce waiting time for patients.
REFERENCES • https: //www. ajronline. org/doi/10. 2214/ajr. 183. 5. 1831 445 • https: //us. medical. canon/news/pressreleases/2007/06/13/217/ • https: //global. medical. canon/products/computedtomography/sure_subtraction • https: //insightsimaging. springeropen. com/articles/10. 1186/s 13244 -019 -0685 -y • https: //www. ncbi. nlm. nih. gov/pmc/articles/PMC 6609 439/ • https: //pubmed. ncbi. nlm. nih. gov/29696430/
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