| ObjectiveMore and more attention is paid for a simple and accurate examination method for diagnosing coronary heart disease. Recently, with the development of CT equipment and exploration of software, scan speed has been greatly increased. Movement organ may be clearly imaged. Multi - slice spiral CT ( MSCT) coronary artery angiography has been a key - point of present radiological study. No relative paper about assessment of acute myocardial infarction and reperfusion with MSCT has been reported. By analyzing the results of MSCT coronary angiography, the aim is to explore the impact of heart rate on the image quality of 16 - slice spiral CT coronary angiography and optimization of image reconstruction window, and evaluate the value of 16 - slice spiral CT examination in diagnosing coronary artery diseases and in evaluating acute myocardial infarction and reperfusion after obstruction of coronary artery by animal model.MethodsThe impact of heart rate on the image quality of MSCTCA69 cases who have accepted MSCTCA were divided into four groups according to the heart rate, the first group including20 cases with heart rates(HR) ≤ 60 beats per minute (bpm) , the second group 15 cases with HR within 61 -65bpm, the third group 18 cases with 66 -70bpm and the fourth group 16 cases with HR > 70bpm. The image quality of MSCTCA was scored four grades from 0 to 3 by observing heart motion artifact and vessel continuity. The images scoredmore than 2 were determined as the susscessful examination. The impact of heart rate on the image quality of MSCTCA were assessed and the examination susscessful rate was calculated according to score result. The optimial reconstruction windows for different coronary segments in every group were evaluated.Diagnosis of coronary artery stenosis with MSCT26 patients who were suspected suffering coronary artery diseases underwent coronary angiography with ECG - gated 16 - detector spiral CT ( MSCTCA) ,of whom 23 patients accepted selective coronary angiography(SCA) before or after MSCTCA. 5 patients of them had coronary artery bypass surgery. 3 patients who had undergone coronary artery bypass surgery didnt performed selective coronary angiography (SCA). Raw data were retrospectively ECG - gated reconstructed and reconstruction images were post processed including volume rendering ( VR) , multi - planar or curved reconstruction and maximum density projector ( MIP) and so on. Every coronary artery segment and its branches were evaluated and coronary artery segments no less than 1.5mm in diameter was counted. Considering selective coronary angiography as the golden standard, the veracity of MSCTCA for diagnosis of the marked stenoses of coronary artery was evaluated.Evolution of myocardial infarction and reperfusion with MSCT12 hybrid canines were devided into two groups. The group of acute myocardial infarction( AMI) was performed pre - enhanced CT scanning before left anterior descending (LAD) ligated and enhanced CT scanning with MSCT at one hour and two hours after ligatation, respectively. The other reperfusion group was also performed pre - enhanced CT scanning before left anterior descending ( LAD) ligated and enhanced CT scanning at one hour after ligation and 30mins after reperfusion, respectively. The morphological changes of ischemic myocardium were observed. The CT value of normal myocardium and that of infarction area were measured. The M/L ratios of the CT value of normal and ischemic myocardium to that of left ventricle cavity were calculated. The statistical analysis was performed by t test.ResultsThe impact of heart rate on the image quality of MSCTCAThe successful rates of examination of the left coronary artery and its main branches from the first to fourth group were 95% ,,93.3% A83. 3% and 50% , respectively; and those of right coronary artery were 90% ?93. 3% ,,77. 8% and 50% Respectively. Statistically, significant difference only existed between the third and fourth group for left circumflex artery segments ( P < 0. 05 ). All coronary artery segments of the first group were optimally visualized on the images reconstructed at 75% image reconstruction window of cardiac cycle; bilateral coronary artery of 80% cases (12/15) were also visualized best at 75% image reconstruction window in the second group;for the third group, 72. 2% of left coronary artery segments and 55. 5% right coronary artery segments were best demonstrated at 75% image reconstruction window, 33.3% of right coronary artery segments at 45% image reconstruction window of cardiac cycle; the optimal reconstruction image of left and right coronary artery segments in fourth group were obtained seperately at 75 -95% and 35 -45% reconstruction window of cardiac cycle, respectively.Diagnosis of coronary artery stenosis with MSCT92. 7% coronary artery segments could be evaluable. The major causes leading to unevalution of images included cardiac motion and calcification artifacts. Except the unevaluable coronary artery segments, the sensitivityAspecificity^ positive predictive value and negative predictive value of MSCTCA in diagnosis of ^50% coronary artery stenosis were 84.7% ,,97.8% ,,90. 5% and 98. 1% compared with SCA,respectively. The sensitivityNspecificity,, positive predictive value and negative predictive value of MSCTCA in diagnosing ^75% coronary artery stenosis or occlusion were 85. 7% ,,98. 3% ,,75% and 99. 2% , respectively. Among 14 stents in 5 patients who had stent placement surgery, MSCTCA, confirmed by SCA, showed 7 stents normal in configuration, and 2 stents distorted, 2 stents with bilateral restenoses, 4 restenosis in distal or proximal parts of normal shaped stent. 8 graft vessels were shown clearly in 3 patientsand there was no stenosis in anastomosis in 7graft vessels.Evolution of myocardial infarction and reperfusion with MSCTFor 12 hybrids, ischemic areas showed low density at one hour after left anterior coronary artery ligation. In AMI group, the density of ischemic area was relatively much lower at 2 hours after ligation. In AMI reperfusion group, the density of ischemic area did not obviously change after 30mins reperfusion, but line — shaped enhancement could be found around the lesion in 2 cases.For AMI group, the CT values of normal myocardium of left ventricle before and after enhancement were (46.75 ±3.71) HU and (119.78 ± 14. 56) HU , respectively. The values of normal and infarction myocardium and the M/L ratios of normal and infarction myocardium were (134. 16 ± 24. 61) HU, (69. 52 ± 7.89) HU, (28. 33 ± 5. 95 ) and ( 13. 19 ± 7. 06 ) at one hour after ligation of LAD, respectively The values of normal and infarction myocardium and the M/L ratios of normal and infarction myocardium were( 158.74 ±4.29) HU, (58.40 ± 9.55)HU,(31.74 ±5. 04) and(11. 58 ±3.81) at 2 hours after ligation of LAD, respectively. Statistically significant differences of the CT values and the M/L ratios between normal and infarction myocardium at one or two hours after ligation exited (P<0.001). In AMI reperfusion group, the CT values of normal myocardium of left ventricle before and after enhancement were (50. 86 ±5.70) HU and (125.41 ±2.64)HU,respectively. The values of A^B^C and D at one hour after ligation were (144.83 ± 12.7)HU,(66.95 ±3.36)HU,(28.97 ±6. 14) and (13. 39 ±5. 31) ,respectively. After 30mins reperfusion, the values of A,B,C and D were (161.74 ±6.19)HU,(61.36 ±6.20)HU,(32.20 ±3.91) and (12.27 ±3.04) , respectively. For AMI reperfusion group, statistically significant differences of the CT values and the M/L ratios also exited between normal and infarction myocardium at one hour after ligation and 30mins after reperfusion (P <0.001). However, there was no statistically difference between one hour after ligation and 30mins reperfusion ( P >0.05 ).ConclusionsFor 16 - slice spiral CT, the successful rate of MSCTCA examination grad-...
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