The Clinical Value Of 16-slice Spiral CT Noninvasive Coronary Angiography

Objective: During the past decade, considerable progress has been achieved in the field of noninvasive coronary imaging with MRI,EBCT and 4-slice MSCT scanners. However, image quality was insufficient for reliable detection of coronary stenosis in a substantial number of cases. Recently, a new generation of MSCT scanners with more and thinner detector rows and increased rotation speed has been introduced. The purpose of the present study is to determine the main technique of the lasted-generation 16-slice spiral CT coronary angiography, analyze the factors affecting image quality, and evaluate the reconstruction imaging in the diagnosis of coronary artery disease. Method: 60 patients (46 male, 14 female, aged 23-81, average 55±11years) with coronary disease or suspected coronary disease (including 3 patients with coronary artery bypass grafts and 5 patients with implantation of stents) were studied with a 16-slice CT scanner(0.42s rotation time,16x0.75mm detector collimation).Criteria for exclusion included allergy to iodine contrast media, renal insufficiency, cardiac dysfunction, irregular heart rate and so on. 18 Patients with a heart rate 65-70/min received 25mg β-blocker 1 hour before the scan. 27 patients with a heart rate above 70/min received 50mg β-blocker. The calcification score and the relationship between calcification score and age,the affected coronary artery segments and the stenosis were evaluated with non-enhanced image. The stenosis degree of artery and patency of stents was also evaluated with enhanced image (1.0mm thickness,0.5mm increment) using VR,MIP,MPR,VE reconstruction type. To evaluate the clinical Value of 16-slice spiral CT noninvasive coronary angiography, all coronary arteries and side branches with a diameter of 2mm or more were assessed by blinded observers for the presence stenosis exceeding 50% diameter reduction. Results: The coronary calcification score (excluding calcification score=0) has a positive correlation with the age r=0.83(P<0.01), so does the affected coronary artery segments r=0.92(p<0.01). As to the evaluation of image quality, 52 patients (86.7%) were the first and second class, 4 patients(10%) were three and four class,2 patients(3.33%) were five and six class. 575(92.4%)segments of 60 patients were judged to be evaluable, 47(7.6%)segments were judged to be unevaluable. The main factors affecting image quality are heart rate(47.6%) ,severe calcifications(31.9%) ,incomplete breath-hold(17.0%) and arrhythmia(8.5%). Within the 20 patients who have selective coronary angiography(SCA),194 segments of 18 patients are classified as excellent by 16-slice CT. In comparison to SCA as the standard of reference, MSCTcorrectly detected 27 of 29 segments with significant stenosis(≥50% diameter reduction), the sensitivity, specificity and positive,negative predictive value to identify≥50% stenosis was 93.1%,97.0%,84.4%,98.8% respectively. When 2 of 11 coronary artery segments with significant stenosis judged unevaluable were included in the analyses, the sensitivity, specificity and positive,negative predictive value to identify≥50% stenosis was 87.1%,97.1%,84.4%,97.7%. The 7 bypass grafts were clearly display. 2 bypass grafts was occluded. The 8 stents were nonobstructed. Conclusion: 16-slice spiral CT with retrospectively ECG-gating scan is a cheap, convenient, reliable noninvasive diagnostic method for coronary heart disease. It can display the coronary artery wall and lumen to come up with the insufficiency of SCA. Coronary calcification is simple for risk prediction .As to evaluation of coronary stenosis, the sensitivity and specificity is high if image quality is sufficient. The higher negative predictive value can avoid unnecessary invasive SCA. It has great potential value in the follow-up of CABG and implantation of stents. It can be used as a screening method in the diagnosis of coronary heart disease.