Subtracted Ct Angiography in the Evaluation of Coronary Artery with Severe Calcification or Stents Using 320-Row CT

Coronary artery disease (CAD) is one of the two main causes of death in Taiwan, as well as in both developing and developed countries. CAD is a major socioeconomic issue due to its high health care expenditure. With rapid technological developments, coronary CT angiography (coronary CTA or CCTA) has become an emerging tool used in the diagnosis of CAD. Improved spatial and temporal resolution of images are reflected in the high diagnostic accuracy achieved with multi-detector CT scanners (64 slice and higher). In selected patients, CCTA is now regarded as a reliable alternative for diagnosing CAD. However, one of the main limitations of CCTA is that its diagnostic accuracy, especially specificity and positive predictive value, significantly decrease in patients with previous coronary stents or heavy calcification (Agatston score ＞ 400) because of their blooming artifact. According to literature and our report, the specificity of CCTA decreases as the coronary calcium score (CS) increases. The specificity is 92.9% for subject with zero CS, 83.3% for those with CS 11-100, and 60% for subjects with CS 401-1,000. The positive predictive value of CCTA in diagnosing in-stent restenosis is relatively poor, the figures are 46%, 68% and 74%, respectively. A 320-row CT scanner is able to cover 16 cm in the z-axis direction. The entire heart’s image can be acquired in a one-beat scan if the heart beat is ＜ 65 beat per minute. Thus, during a single breath-hold of 15-35 seconds, both the images before and after contrast enhancement can be acquired using prospective scanning. Subtracted CCTA can be obtained from the two images after being processed to remove any calcification or stents. This requires exact alignment and may therefore be possible with 320-row CT. To our knowledge, reports of subtracted CCTA using 320-row CT are limited. There are only two papers with few cases reported from the same institute. In this three-year research project, we attempt to collect 300 cases of coronary artery lesions 2 with severe calcification (Agatston score ＞ 400) (100 case) or stents (200 cases). A software for subtraction of CCTA will be installed. CCTA without and with subtraction, as well as invasive coronary angiography, will be performed over one month. Using invasive coronary angiography as the gold standard, this study will analyze and compare the sensitivity, specificity, accuracy, and positive and negative predictive values of 320-row CCTA and subtracted CCTA in assessing coronary artery stenosis associated with heavy calcification or stents. The effective radiation dose of each subject in this study will be 6 to 10 mSv, including 4 mSv from subtracted CCTA. The dose of 6-10 mSv is lower than or equivalent to that of 10 mSv from abdominal CT. It is predicted that the subtracted CCTA will improve the specificity and positive predictive value in assessing coronary artery stenosis or disease associated with heavy calcification or stent. The success of this project will be beneficial to CAD patients in the future.

Project ID:PC10401-0623
External Project ID:MOST103-2314-B182-012-MY3