| Objective:To investigate the optimal reconstruction phase of coronary angiography with 16-slice spiral CT and the impact of saline in coronary angiography, and evaluate the clinical application value.Materials and methods:1. Patients data: Three hundred and fifty-two patients (288 males and 64 females; mean age 57 years; range 34~77) with suspected or diagnosed coronary artery disease were studied using 16-slice spiral CT from December 2002 to October 2004.And forty-two patients underwent conventional coronary angiography within a week. Fifteen patients had previously undergone percutaneous transluminal coronary angioplasty with stent implantation and three patients had undergone coronary artery bypass grafting.2. Scanning protocol: All the examinations were performed with a 16-slice spiral CT scanner (SIEMENS SOMATOM Sensation 16) and the technique of retrospective ECG-gating was applied. All patients underwent plain and enhanced scan.Auto-triggering enhanced scan was applied and the scan range was from the trachea carina to the diaphragmatic face of the heart.3. Post-processing method: Raw data was reconstructed at the time point of 300ms, 400ms, 500ms, 600ms before each R wave respectively, and the axial images in different phases were reconstructed in a Wizard work station using maximum intensity projection, multiplanar reformation and volume rendering technique.4. Evaluation methods:4.1 Patients were divided into two groups randomly for contrast material administration: group 1(120ml Omnipaque) and group 2(100ml Omnipaque followed by 40ml saline). The injection rate was 3.5ml/s. The attenuation of ascending aorta, pulmonary artery and superior vena cava on the original section of left and right coronary artery was recorded. The attenuation of the left main, left anterior descending, circumflex and the right coronary artery was also assessed.4.2 The image quality of coronary artery was divided into five grades and the grade of every coronary artery in different reconstruction phases was evaluated. The branches of coronary artery were divided into twelve segments and the displayed segments of every coronary artery in different reconstruction phases were analyzed.4.3 The results of calcification score were classified into five grades: without calcification (0), subtle (1-10), gentle (11-100), moderate (101-400) and severe (>400) calcification.4.4 The coronary artery segments were divided into assessable and unassessable segments according to the quality grade of images.4.5 The degree of stenosis of coronary artery was divided into four groups: gentle (<50%), moderate (51%~75%), severe (76%~99%) stenosis and occlusion (100%).4.6 The findings of CT were compared with those of conventional coronary angiography.5. Statistical assay: The data was analyzed using the software of SPSS 11.0. P<0.05 was taken to indicate statistical difference. Results:1. The attenuation of ascending aorta in group 1 was significantly inferior to group 2 and the attenuation of the superior vena cava in group 1 was significantly superior to group 2.The attenuation of pulmonary artery on the original section of the left and right coronary artery in group 2 was both inferior to group 1, but the difference was significant on the original section of the right coronary artery and not significant on the original section of the left coronary artery. The attenuation of the main coronary artery branches in group 1 was all significantly inferior to group 2.2. The left main coronary artery was displayed well in every phase and the optimal reconstruction phase of the left anterior descending, the circumflex and the right coronary artery was the time point of 400ms and 500ms, 400ms, 400ms before R wave respectively.3. The segments that could be assessable were 89.9% of the total segments by 16-slice spiral CT and the sensitivity, specificity, positive predictive and negative predictive in diagnosing coronary artery stenoses were 90.6%, 80.2%, 79.1%, 91.3% respectively.Conclusion:1. Using saline could not only save the contrast material, but also decrease the enhancement of the superior vena cava and the right heart and increase the enhancement of coronary artery, which may improve the quality of images.2. Image reconstruction in the optimal phase could decrease the artifacts of cardiac motion as much as possible, which improves the quality of images further.3. Coronary angiography with 16-slice spiral CT could display the trunks and the main branches of coronary artery clearly. And it plays important roles in the aspects of detecting calcification, diagnosing stenoses. So it could be used as the screening method of coronary artery diseases. |
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