| Part I Individual optimized injection of contrast medium for 256-MDCT coronary angiographyObjective:The aim of the study was to evaluate the feasibility of individually tailored protocols of multiphase contrast-saline mixture for higher quality of the distal segments of coronary artery, right ventricular (RV) and interventricular septum (IVS), compared with conventional injection protocols, and to optimize the injection protocols.Methods:100 patients underwent coronary CT angiography (CTA) imaging with 256-row MDCT in our institute from December 2009 to January 2010. The patients were randomized into two groups. Group 1 received 75ml of contrast medium (CM) at 4.5ml/s, followed by 30ml saline. For group 2, the injection parameters were adapted to patient weight. The body weight of the patients less than 59kg received 71ml CM at 4.5ml/s, followed by 35ml contrast-saline mixture at 20:80 ration. The body weight of the patients between 60 to 74kg received 77ml CM at 4.8ml/s, followed by 35ml contrast-saline mixture. The body weight of the patients over 75kg received 85ml CM at 5.7ml/s, followed by 45ml contrast-saline mixture. The attenuation was measured of 15 coronary segments according to American Heart Association Classification, ascending aorta, descending aorta, pulmonary artery and RV by two experienced radiologists. Visualization of coronary arteries and IVS were rated. The data were analyzed between groups.Results:1. The mean CT values of the proximal, mid segment of the right coronary artery (RCA), the left main artery coronary artery (LM), the proximal and mid segment of the left anterior descending artery (LAD), the first diagonal branch (D1), the proximal segment of the left circumflex artery (LCX) in group 2 were lower than group 1. The mean CT values of the distal segment of LAD, the posterior descending branch, the second diagonal branch (D2), the distal segment of LCX, the obtuse marginal branch, the posterior left ventricular branch, the second obtuse marginal branch in group 2 were higher than group 1. Only attenuation in the distal segment of LAD differed significantly (p<0.05).2. The mean CT values of pulmonary artery and RV cavity in group 2 were higher than group 1, which had statistical differences (p<0.05). The mean CT values of ascending aorta and descending aorta of the two groups had no statistical difference (p>0.05).3. The image quality of all coronary segments had statistical differences (p<0.05). The image quality of the posterior descending branch, the mid and distal segment of LAD, D1, D2, the posterior left ventricular branch, the second obtuse marginal branch of the two groups had statistical differences (p<0.05). The image quality of the proximal, mid and distal segment of RCA, LM, the proximal segment of LAD, the proximal and mid segment of LCX, the obtuse marginal branch of the two groups had no statistical difference (p>0.05).4. For the visualization of IVS, group 2 was better than group 2 (p<0.05).Conclusions:1. Individually tailored protocols can get higher attenuation in the distal segments of the coronary artery, and improve the image quality.2. Individually tailored protocols can provide higher attenuation of RV, get clear visualization of RV and IVS, while acquired at the coronary CTA, which can provide more information for clinic. Part II The study on the prevalence of the Myocardial bridging and the correlation with coronary atherosclerosis by 256-MDCTObjective:The aim of the study was to evaluate the prevalence, length, depth, and the location of Myocardial bridging (MB) using 256-row MDCT coronary CT angiography (CTA) with individually tailored contrast injection protocols, and the concomitant atherosclerosis of MB.Methods:From January 2010 to May 2010,251 patients for various indications underwent CTA imaging with 256-row MDCT and individually tailored contrast injection protocols in our institute. The prevalence, length, depth, and the location of MB were evaluated. The proximal and distal segments to the bridging were evaluated for atherosclerotic plaque, as well as the tunneled coronary.Results:Of the 251 patients,52 (20.7%, mean age 60.92±11.70) patients with a total of 66 coronary segments were found to have MB. The length of bridged segments ranged from 4.2 to 32mm, with an average length of 20.1±5.8mm, and the depth of the bridged segments ranged from 0.5 to 8.9mm, with an average depth of 3.43±1.78mm (superficial 47,71.2%; intramyocardial 19,28.8%). MB was frequently located in the mid segment of LAD (72.7%).13.6% of the proximal segments to the bridge were found atherosclerotic plaque, but compared with the patients without MB, there had no statistical difference (p>0.05). The mean length and the mean depth of the MB patients with atherosclerosis were 19.6±6.3mm and 4.14±0.58mm, respectively. The tunneled coronary and the distal segments to the bridge were hardly involved.Conclusions:1. The prevalence of MB was 20.7%, frequently located in LAD, especially in the mid segment of LAD. The proximal segment of MB were apt to involved with atherosclerosis 2. MDCT is an effective and noninvasive tool to evaluate MB, which can directly demonstrate the anatomic relationship of the MB, myocardium and atherosclerotic plaque. With the using of individually tailored contrast injection protocols, we can get more clear visualization of MB.
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