Applications Study Of Multi-slice Computed Tomography On Coronary Artery Imaging

Part 1 Different contrast injection protocols for noninvasive 64-slice computed tomographic coronary angiographyObjectives To determine the optimal contrast injection protocol for 64-slice computed tomographic coronary angiography.Methods One hundred and fifty consecutive patients scheduled to undergo retrospectively electrocardiographically gated 64-slice computed tomography.Each 30 patients were assigned to use a different contrast protocols:group 1:uniphasic protocol(contrast injection without saline flush); group 2:biphasic protocol(contrast injection with saline flush);group 3A,3B and 3C: triphasic protocol(contrast material+different saline diluted contrast material+saline flush).Attenuation was measured in the right atrium,right ventricle,left atrium,left ventricle,ascending aorta,right coronary artery and left coronary artery was evaluated and analyzed by s one-way analysis of variance test(ANOVA).The quality of the coronary artery image was evaluated and compared using person Chi-square.Results Among the triphasic protocol groups,group 3A(30%:70%contrast material-saline mixture was used in second phase) used the least contrast material and had the least frequency of streak artifacts,but there were no significant differences in coronary artery attenuation,image quality,visualization right and left heart structures respectively.Among the uniphasic protocol group(group 1),biphasic protocol group (group 2) and triphasic protocol subgroup(group 3A),there were no significant differences in image quality scores of coronary artery(P=0.18);uniphasic protocol group had the highest frequency of streak artifacts(20 cases)(P＜0.05) and had the most amount contrast material(67.0±5.3 ml);biphasic protocol group had the least amount of contrast material(59.9±4.9 ml)(P＜0.05) and had the highest attenuation of left main coronary artery and right coronary artery(P＜0.01),but had the least amount of clear visualization right heart structure(6 cases);triphasic protocol group(group 3A) had the most amount of clear visualization right heart structures(29 cases) were the most among the three groups(P＜0.05).Conclusions Biphasic protocol are superior to the traditional uniphasic protocols for using the least total contrastmedia,having the least Streak artifacts and without image quality degradation.Triphasic protocol (30%:70%contrastmedia-saline mixture was used in second phase) are superior to for clearly visualization of both left ventricle and right ventricle cavities without contrast material volume increase and image quality degradation.Part 2 Evaluation of Coronary Stents In Vitro With 64-slice Computed TomographyObjectives To assess the visualization of different coronary artery stents and the delineation of in-stent stenosis using 64-slice computed tomography (MSCT) with different scan modes when it were placed at different positions.Methods A total of 18 different coronary stents(10 stents with lumen diameter stenosis of 50%) were placed in a vascular phantom and scanned with a 64-slice computed tomography at the distance of 0 mm,25mm,50mm,75mm,and 100mm from the centre of scanner to the phantom.The scan modes were retrospective ECG gating helical scan(tub current:400mA and 600mA) and non-ECG triggering axial scan(tube current:350mA). Visible lumen diameter and attenuation in the stented segments of the phantom were measured.Two readers assessed stenosis delineation.Results(1)The visible lumen diameter and percent of the visible in-stent stenosis had significantly negative correction with the distance between the center of scanner and the phantom(r=-0.71, -0.78 respectively)(all P＜0.01).The attenuation of stent lumen,the attenuation of the water around the stent and the noise of the water around the stent had significantly positive correction with the distance between the center of scanner and the phantom (r=0.39,0.11,0.46 respectively).(2) Different scan mode and different tube current had no effect on the visible lumen diameter,the attenuation of stent lumen,the percent of the visible in-stent stenosis and the attenuation of the water around the stent (P＞0.05),but had effect on the noise of the water around stent(P＜0.01)。Conclusion The distance between the center of scanner and the stents has effect on the display of the stents.The scan mode has little effect on the display of the stent.MSCT Shows limit value in detecting in-stent restenosis. Part 3 Study of Morphological Characteristics of Calcified Plaques and Lumenal Stenosis On 64-slice Computed Tomographic Coronary AnigiographyObjective To research the morphological characters of coronary artery calcified plaque and it's relation to the degree of stenosis of local coronary artery lumen by multi-slice computed tomography.Methods One hundred and eleven patients who had received 64-slice computed tomographic coronary angiography and conventional coronary angiography(CAG) were found calcified plaques burden.The calcified plaques were classified as punctate,nodular,strip-like and nubbly in long-axis view,and were classified as crescent,semilunar,round moon and circinate in short-axis view.The morphologic characters of these calcification plaques were retrospectively analyzed.The stenosis degree of the corresponding coronary artery lumen was judged in accordance with the results of CAG.Severe stenosis was defined as stenosis of≥75%of the luminal diameter.Results Totally 528 calcified plaque segments were analyzed in coronary computed tomography angiography(CTA) in these 111 patients.Among these there were 383(72.5%) punctate calcified plaque segments and 145(23.5%) non- punctate calcified plaque segments.No obvious stenosis in coronary artery was caused by punctate calcified plaques.There were 34 non-punctate calcified plaques which caused severe stenosis.The ratio of different morphological coronary artery calcification which caused sever stenosis was significant different(all p＜0.01).There were 4 nodular calcified plaques,8 stripe-like calcified plaques and 22 nubbly calcified plaques which caused severe stenosis.42.3% (22/52) nubbly calcified plaque caused severe stenosis.At the same time,there were 0 crescent calcified plaques,8 semilunar calcified plaques,18 round moon calcified plaques and 8 circinate calcified plaques which caused severe stenosis.66.7%moon calcified plaque and circinate calcified plaques caused severe stenosis.Conclusion Different coronary artery calcified plaques generate different degree of stenosis of local coronary artery lumen.Severe stenosis are mostly caused by nubbly calcified plaque(long-axis view),moon calcified plaque(short-axis view) and circinate calcified plaque(short-axis view). Part 4 Prospective ECG triggering for dual-source CT coronary angiography:Comparison with conventional coronary angiography.Objective To evaluate the accuracy and feasibility of dual-source computed tomography coronary angiography(CTCA) using prospective ECG triggering for the assessment of coronary artery disease(CAD).Methods A tall of 30 patients with heart rate less than 75 beats per minute underwent prospective ECG triggering and conventional coronary angiography(Study group) and 45 patients underwent retrospective ECG gating and conventional coronary angiography(Control group).Two independent radiologists assessed the severity of stenosis of CT coronary angiograms,and two independent cardiologists assessed the severity of stenosis of conventional angiograms.All of them used blinging method.Effective radiation doses were calculated and image quality was valuated.Results The differences in diagnostic performance on a per-patient basis between prospective CT angiography and retrospective CT angiography were not significantly different:sensitivity was 100.0%,97.4%,respectively(P=0.86);specificity was 66.7%,100.0%,respectively (P=0.65);PPV was 96.4%,100.0%,respectively(P=0.89);NPV was 100.0%,87.5%, respectively(P=0.43);diagnostic accuracy was 96.7%,97.8%,respectively(P=0.66). Similarly,no level of significance was reached on a per-vessel analysis:sensitivity was 95.9%,91.1%,respectively(P=0.46);specificity was 97.2%,97.0%,respectively (P=0.85);PPV was 95.9%,96.0%,respectively(P=0.66);NPV was 97.2%,93.2%, respectively(P=0.41);diagnostic accuracy was 96.7%,94.4%,respectively(P=0.53). In the same way no level of significance was reached on a per-segment analysis sensitivity was 95.9%,91.1%,respectively(P=0.46);specificity was 97.2%,97.0%, respectively(P=0.85);PPV was 95.9%,96.0%,respectively(P=0.66);NPV was 97.2%,93.2%,respectively(P=0.41);diagnostic accuracy was 96.7%,94.4%, respectively(P=0.53) when comparing prospective CT angiography and retrospective CT angiography.Consensus-determined image quality in coronary artery branches was similar between prospective CT angiography and retrospective CT angiography (3.3±0.5 vs 3.2±0.3,respectively;P=0.23).Calculated effective dose with prospective CT angiography was 71%lower than that with retrospective CT angiography(3.1mSv±1.3 vs 10.8 mSv±4.6,respectively;P＜0.01).Conclusion Prospective CT angiography can reduce radiation dose below that of retrospective CT angiography,while maintain image quality and the ability to assess luminal obstructions in patients with a stable heart rates of less than 75 beats per minute.Part 5 Prevalence of coronary artery calcium among natural population in BeijingObjective To investigate prevalence and amount of CAC as determined by Multi-slice computed tomography(MSCT) in Beijing community natural population.Methods A stratified random sample of 1800 community natural residents in Beijing was enrolled in the study.All subjects would undergo non-enhanced coronary scan by retrospectively ECG-Gated MSCT.Agatston scoring was used for CAC.Coronary artery calcium score(CACS) was calculated for each subject.Groups were compared with respect to age,gender.Results There were 1548 subjects(53.3±7.8 years) enrolled in our study.CAC was found in 29.8%(461/1548) of the subjects.The prevalence of CAC was significantly higher in male subjects (37.7%,270/716) than female subjects(23.0%,191/832)(p＜0.001).The CACS of male subjects and female subjects were 77.5±252.0 and 37.8±178.9,respectively.It was significantly higher in males than females(p＜0.05).The CACS increased significantly with increasing age in males and female subjects(p＜0.05).In the study, age and mellitus diabetes were significantly associated with CACS in both men and women(all p＜0.05).Additionally,hypertension showed significant associations with CACS in women only(p＜0.001).Conclusion There is an increase in the prevalence and amount of coronary artery calcification with age in Beijing community population. Males have significantly higher prevalence and amount of CAC than females.The development of CAC of Chinese and it's relation to the cardiac events should be studied further.