Cardiac ct

cardiac imaging protocol of CT

1. Maajid Mohi ud din Lecturer COPMS adesh university bathinda punjab CARDIAC CT

2. I NTRODUCTION Coronary artery disease- major cause of death, enormous economic burden on healthcare. Prime diagnostic tool- Coronary angiography Invasive Longer examination time Pt. prep time and recouping time .

3. Advantage of MDCT technology: sub millimeter spatial resolution, improved temporal resolution and ECG triggered or gated mode of acquisition Non-invasive imaging of heart and coronary arteries. Calcium scoring, CT angiography, and assessment of ventricular function.

4. C ARDIAC S CANNERS EBCT: 1982, specifically for cardiac imaging, able to acquire an image in 100 msec, suited for cardiac imaging at that time. Electrons accelerated in a vacuum funnel and are precisely focused toward and swept across a 210º tungsten ring anode placed under the patient. A cone beam of X-ray photons is emitted which go through the patient and are captured by two 240º detector rows above the patient.

5. Slice collimation is 3 mm, so 40 slices needed to cover the entire heart (12 cm),for a total imaging time of 30 sec. One breath-hold. ECG-based triggering used for motion-free imaging during diastole . Significant motion artifacts still remain.

6. Mostly used for noninvasive evaluation of coronary artery calcium but other applications including assessment of coronary artery stenosis have been reported in limited cases. Expensive and widely not available .

7. SSCT Single-slice helical CT could be used for cardiac imaging with ECG protocols. Temporal resolution was improved over non-helical scanners but, remained insufficient for motion-free cardiac imaging. Could not meet unique demands of imaging the beating heart require optimal spatial resolution, temporal and contrast resolution.

8. MDCT S ub millimeter spatial resolution (0.75 mm), Improved temporal resolution (80–200 msec), and Electrocardiographically (ECG) gated or triggered mode of acquisition, MDCT scanners (16–64-row detectors) makes cardiac imaging possible

9. K EY ISSUES IN CARDIAC IMAGING High temporal resolution Virtually “freeze” the beating heart to image coronary arteries located close to heart muscles, which show rapid movement during cardiac cycle. Imaging is best if performed in diastole phase- most

10. High spatial resolution- resolve very fine structures e.g. proximal coronary segments which range from a few mm in diameter (at the apex of aorta) and decrease to a few sub mm in diameter as they traverse away from aorta in all directions.

11. C ORONARY ARTERY Coronary artery is a vasa vasorum that supplies the heart . The coronary artery arises just superior to the aortic valve and supply the heart The aortic valve has three cusps left coronary (LC), right coronary (RC) posterior non-coronary (NC) cusps.

12. R IGHT CORONARY ARTERY

13. Diagnosing Heart Disease With Cardiac Computed Tomography Computed tomography, commonly known as a CT scan, combines multiple X-ray images with the aid of a computer to produce cross-sectional views of the body. Cardiac CT is a heart-imaging test that uses CT technology with or without intravenous (IV) contrast (dye) to visualize the heart anatomy, coronary circulation, and great vessels (which includes the aorta, pulmonary veins, and arteries).

14. There are several types of CT scans used in the diagnosis of heart disease, including : Calcium-score screening heart scan Coronary CT angiography (CTA) Total body CT scan

15. What is Cardiac CT for Calcium Scoring? A cardiac CT scan for coronary calcium is a non-invasive way of obtaining information about the presence, location and extent of calcified plaque in the coronary arteries—the vessels that supply oxygen-containing blood to the heart muscle. Calcified plaque results when there is a build-up of fat and other substances under the inner layer of the artery. This material can calcify which signals the presence of atherosclerosis, a disease of the vessel wall, also called coronary artery disease (CAD).

16. People with this disease have an increased risk for heart attacks. In addition, over time, progression of plaque build up (CAD) can narrow the arteries or even close off blood flow to the heart. The result may be chest pain, sometimes called "angina," or a heart attack. Because calcium is a marker of CAD, the amount of calcium detected on a cardiac CT scan is a helpful prognostic tool. The findings on cardiac CT are expressed as a calcium score. Another name for this test is coronary artery calcium scoring.

17. What are some common uses of the procedure ? The goal of cardiac CT scan for calcium scoring is to determine if CAD is present and to what extent, even if there are no symptoms. It is a screening study that may be recommended by a physician for patients with risk factors for CAD but no clinical symptoms. The major risk factors for CAD are:

18. High blood cholesterol levels Family history of heart attacks Diabetes High blood pressure Cigarette smoking Overweight or obese Physical inactivity

19. Coronary CT Angiography (CTA ) Coronary computed tomography angiography (CTA) is a noninvasive heart imaging test currently undergoing rapid development and advancement. High-resolution, 3-dimensional pictures of the moving heart and great vessels are produced during a coronary CTA to determine if either fatty or calcium deposits (plaques) have built up in the coronary arteries.

20. Before the test, an iodine-containing contrast dye is injected into an IV in the patient's arm to improve the quality of the images. A medication that slows or stabilizes the patient's heart rate may also be given through the IV to improve the imaging results .

21. During the test, which usually takes about 10 minutes, X-rays pass through the body and are picked up by special detectors in the scanner. The newer scanners produce clearer final images with less exposure to radiation than the older models. These new technologies are often referred to as "multidetector" or "multislice" CT scanning.

22. Another new technology, known as dual-source CT, uses two sources and two detectors at the same time. This technology provides full cardiac detail with about 50% less radiation exposure than traditional CT. Since it's noninvasive, a coronary CTA can be performed much faster than a cardiac catheterization (also called a "cardiac cath " or coronary angiogram), with potentially less risk and discomfort to the patient, as well as less recovery time.

23. Although coronary CTA exams are growing in use, coronary angiograms remain the "gold standard" for detecting coronary artery stenosis, which is a significant narrowing of an artery that could require catheter-based intervention (such as stenting) or surgery (such as bypassing) to treat the narrowed area. However, coronary CTA has consistently shown the ability to rule out significant narrowing of the major coronary arteries. This new technology also can noninvasively detect "soft plaque," or fatty matter, in the coronary artery walls that has not yet hardened but that may lead to future problems without lifestyle changes or medical treatment.

24. Coronary CTA is most useful to determine whether symptoms of chest pain may be caused by a coronary blockage, particularly in individuals that may be at risk, such as those with a family history of cardiac events, diabetes, high blood pressure, smokers, and/or those with elevated  cholesterol . However, there is still much controversy as to when a coronary CTA should be used.

25. Coronary CT Angiography (CTA) Main purpose: morphology Detection and analysis of CAD Depict anatomy of coronary vasculature Possible to obtain functional info Contractility of myocardium Valve morphology and function Viability of myocardium

26. P ATIENT PREPARATION Clinical history (symptoms such as chest pain and dyspnea) History of allergies (e.g., iodinated contrast material and medications ) History of asthma or hyperthyroidism History of renal disease or multiple myeloma (recent creatinine level) Previous diagnostic examinations (stress test, electrocardiogram [ECG], and echocardiogram). Intravenous access via a intravenous line is ensured

27. H EART RATE CONTROL A stable, low heart rate is required at the time of the procedure, The highest image quality for current CCT scans is achieved at heart rates of less than 65 beats per minute ( bpm ) Oral or intravenous b-blockers should be administered before the study, b-Blockers help reduce heart rate variability during the scan, and for that reason, their administration is recommended almost routinely unless they are contraindicated (e.g., patients with asthma). In such situations, diltiazem or verapamil may be used as an alternative agent, although these drugs are not as effective as b-blockers

28. B REATH H OLDING During the test, a breath hold of 15–20 s will need to be performed Before the scan, practicing breath holding helps. ECG GATING First, the skin is cleaned Up to 12 self-adhesive electrodes will be attached to select locations of the skin on the arms, legs and chest Three ECG leads are attached to obtain an adequate ECG tracing for CT A noise-free ECG signal is important to synchronize the ECG signal to the raw image data

29. CTA PROTOCOL Calcium scoring (low dose tech), 40mAS, 120 kvp Method :- Retrospective ECG triggered Head first, supine Kvp – 120, mAs – 160 Detector conf.: 64 x 0.625 mm Pitch :- 0.2 GR :- 0.33 sec Delay :- 5 sec Fov :- 200 mm Matrix:- 256 Slice thickness :- 3 mm, recon :- 0.6 mm , increment :- 0.3 mm

30. Diagnosing Heart Disease With Cardiac Computed Tomography (CT ) Before the test, an iodine-containing contrast dye is injected into an IV in the patient's arm to improve the quality of the images. A medication that slows or stabilizes the patient's heart rate may also be given through the IV to improve the imaging results.

31. During the test, which usually takes about 10 minutes, X-rays pass through the body and are picked up by special detectors in the scanner. The newer scanners produce clearer final images with less exposure to radiation than the older models. These new technologies are often referred to as "multidetector" or "multislice" CT scanning.

32. Another new technology, known as dual-source CT, uses two sources and two detectors at the same time. This technology provides full cardiac detail with about 50% less radiation exposure than traditional CT.