CARDIOVASCULAR IMAGING WITH COMPUTED TOMOGRAPHY(CT)

1. CARDIOVASCULAR IMAGING WITH COMPUTED TOMOGRAPHY(CT) Hakan SOLMAZ, Institude of Biomedical Engineering, Boğaziçi University

2. Computed Tomography of the HeartKey Points • greater spatial and temporal resolution • detailed anatomic information • image reconstruction in 3-D • estimation of calcified and noncalcified plaque in coronary arteries

3. Computed Tomography of the Heart ABrief History of CT • Comes from the Greek word "tomos" meaning "slice" or "section" and graphia meaning "describing". • The first clinical CT scanners were installed between 1974 and 1976, were dedicated to only head imaging. • The first CT scanner developed by Hounsfield.

4. Computed Tomography of the Heart How Does CT Work? • combines the use of a digital computer together with a rotating x-ray device • cross sectional images or "slices" • lungs, liver, kidneys, pancreas, pelvis, extremities, brain, spine, and blood vessels .

5. Computed Tomography of the Heart How Does CT Work?

6. Computed Tomography of the HeartHow Does a CT Look Like Outside view of a CT system Inside view of a CT system showing the patient table showing the X-ray tube and detector

7. Computed Tomography of the HeartWhy is CT Performed? • CT has the unique ability to image a combination of soft tissue, bone, and blood vessels • Conventional X-Ray imaging shows the dense bone structures, • X-ray angiography depicts the blood vessels, • MR imaging is excellent in showing soft tissue and blood vessels

8. Computed Tomography of the HeartWhy is CT Performed? • CT can provide detailed cross sectional images and diagnostic information for nearly every part of the body; • the brain, vessels of the brain, eyes, inner ear, sinuses • the neck, shoulders, cervical spine and blood vessels of the neck • the chest, heart, aorta, lungs, mediastinum • the thoracic and lumbar spine • the upper abdomen, liver, kidney, spleen, pancreas and other abdominal vessels

9. Computed Tomography of the HeartCT of the Heart • Planar Imaging vs CT Imaging • Planar image processors can not show smaller structures • They create images of the silhouette of the contrastfilled vessels • 3-D CT image can reveal complex anatomy and spatial relationships

10. Computed Tomography of the HeartCT of the Heart • Planar Imaging vs CT Imaging • CT imaging is slower than planar imaging • planar radiograph ~ 4 to 10 ms exposure time • tomographic image slice ~ 50 to 250 ms • each image slice must be acquired during the late diastole

11. Computed Tomography of the HeartCT of the Heart standard chest radiograph which is a planar projection three-dimensional computed tomographic image

12. Computed Tomography of the HeartTwo Types of CT Scanners • Electron-beam CT • developed for cardiac imaging; 50-100 ms per image slice • reflecting electron beam onto a stationary tungsten target • Multidetector CT • developed for body imaging • mechanically rotating an x-ray tube

13. Computed Tomography of the HeartTwo Types of CT Scanners • new multidetector CT scanners; • high spatial and temporal resolution

14. Computed Tomography of the HeartPrinciples of Cardiovascular CT Examination • the image data are acquired during one breath-hold within a chosen scan protocol • most protocols require iodinated contrast agents to enhance cardiovascular structures • two Acquisition modes; • The sequential 2-D mode • The spiral 3-D mode

15. Computed Tomography of the HeartPrinciples of Cardiovascular CT Examination • A smaller slice thickness allows better resolution • radiation exposure and scan time increase • volume covered is reduced • A slower heart rate allows better CT image quality • betablockers are desirable to slow the heart rate

16. Computed Tomography of the HeartClinical Cardiovascular Indications • CT can be used for a number of cardiovascular indications, but sometimes with another imaging test; • Hypertension; CT + MRI • acute midsternal chest; CT + angiography

17. Computed Tomography of the HeartClinical Cardiovascular Indications • Cardiac CT is especially useful in evaluating the • myocardium, • coronary arteries, • pulmonary veins, • thoracic aorta, • pericardium

18. Computed Tomography of the HeartClinical Cardiovascular Indications • Cardiomyopathy with contrast enhanced CT • ischemic cardiomyopathy, CT typically shows; • Focal ventricular wall thinning • Fibrous or calcified replacement of myocardium • Aneurysm formation

19. Computed Tomography of the HeartClinical Cardiovascular Indications • non-ischemic cardiomyopathy, CT typically shows; • global dilatation and myocardial thinning, • focal myocardial hypertrophy

20. Computed Tomography of the HeartClinical Cardiovascular Indications two chamber view three chamber view

21. Computed Tomography of the HeartClinical Cardiovascular Indications four chamber view short-axis view

22. Computed Tomography of the HeartClinical Cardiovascular Indications • Coronary artery stenosis with contrastenhanced CT scan • allow one to assess stenosis • Coronary CT angiography is challenging • the blood vessels are small, tortuous, and in rapid motion during the cardiac cycle • CT doesn’t have enough spatial and temporal resolution to show all the coronary segments • There may be plaque calcification

23. Computed Tomography of the HeartClinical Cardiovascular Indications • Uses of CT angiography; • To rule out severe proximal stenosis • To assess anomalous coronary arteriesand to determine their origins and their relationship • evaluate the severity of stenosis in venous aortocoronary grafts

24. Computed Tomography of the HeartClinical Cardiovascular Indications • Coronary CT can exclude significant obstructive disease and assess atherosclerotic plaque

25. Computed Tomography of the HeartClinical Cardiovascular Indications The smaller images are the views at the level of aortic valve

26. Computed Tomography of the HeartClinical Cardiovascular Indications • Pericardial diseases; • Detailed anatomic information about the pericardium • Inflammation of the pericardium can be detected with contrast-enhanced CT

27. Computed Tomography of the HeartClinical Cardiovascular Indications • Cardiac masses can be described on CT according to their, • size, density, and spatial relationship to adjacent structures • Although CT can also detect tumors, it is limited

28. Computed Tomography of the HeartClinical Cardiovascular Indications • additionaly; • valve stenosis and regurgitation, • aortic disease, • pulmonary embolism, • pulmonary veins imaging

29. Computed Tomography of the HeartFrequently Asked Questions • Does the CT examination hurt? • No, it does not, except the case of iodine contrast injection, which is discomfortable during the needle is placed • Is CT Imaging Safe? • the diagnostic benefit of a CT scan usually outweighs the risk of x-ray radiation exposure or injections of imaging contrast

30. Computed Tomography of the HeartFrequently Asked Questions • How long will the CT examination take? • the actual procedure will typically be between 10 minutes and 45 minutes • Can I Move While I am in the CT Scanner? • You should not move when you are on the CT table and the images are being acquired. CT exams of the chest and abdomen require the patient to hold their breath for a short period of time, for example, 10 to 25 seconds

31. Computed Tomography of the HeartReferences • http://imaginis.com • Physical Principles of Medical Imaging; Perry Sprawls, Proff. Of Radiology, Emory University School of Medicine • http://www.radiologyinfo.org • http://www.clevelandclinic.org/heartcenter • http://www.ctisus.org