The Study Of Low Dose Dual-source CT Coronary Angiography And Imaging Of Myocardial Brigde

Objective: To analyze the differences of radiation dose and image quality of prospectiveversus retrospective ECG gated coronary angiography with dual source CT, in order toprovide individualized scanning procedure for the clinical application of low dose coronaryangiograph.Materials and Methods:90patients who were referred for coronary CT angiography withdual source CT scanner were enrolled and divided into two groups: prospective group (PG)included40cases, tube voltage was120KV, and reference tube current was400mAs withapplication of automatic tube current modulation (ATCM) scanning technique; Theretrospective group (RG) included50cases, tube voltage was120KV, reference tubecurrent was400mAs with application of ATCM technique, and ECG automatic tube currentmodulation and pitch-rate matching technology were also used. Two radiologistindependently assessed image quality in segments (diameter>1mm)) by using a four-pointscale; and the assessable image quality was defined as scored1,2and3. Radiation dose ofCTA exam was calculated.Results:(1) Of the40cases in PG,554segments of coronary artery were showed, thepercentage of assessable coronary segments (≤3points) was99.27%and scored as excellent(1point) was segments was96.93%.645segments of coronary artery were revealed in RG(50cases),98.76%could fulfill the requirement of diagnosis and88.99%were excellent.The total segments with assessable image quality was significant difference (p=0.024)between these two groups, and the segments scored1in PG group were more than RGgroup (P＜0.001).(2) the mean radiation dose of PG group and RG group was4.46mSvand6.61mSv, and it was statistically significant difference (P＜0.001). Conclusions: With various procedures of radiation dose reduction, low radiation dosecould also be achieved with RG without heart rate control. PG is the most effectiveapproach for the reduction of radiation dose, yet low and stable heart rate wereindispensible for high image quality. In clinical work, the appropriate scan mode andparameters should be selected based on patients’ conditions to ensure image quality andlow-dose scan. Chapter Ⅰ The CT imaging characteristics of incomplete and completemyocardial bridges-mural coronary arteryObjective: To study the types of the myocardial bridge (MB) and the CT imagingcharacteristics of MB and mural coronary artery (MCA).Materials and Methods: Fifty patients with dual source coronary CT angiography(DSCTA) evidenced with MB were included. The MB was divided into into two groups:incomplete MB group (partial encasement) and complete MB group (full encasement). Thediameter of MCA, proximal segment and distal segment in best systole phase and diastolephase, the MCA stenosis rate, the presence of atheromatous change proximal to the MBwere evaluated.Results: A total of58MBs were detected, the average length was2.02cm,23wereincomplete MBs and35were complete MBs. Thirty-two (55.2%) MBs were in the middlesegment of left anterior descending artery (LAD);17(29.3%) MBs were in the distalsegment of LAD;1MB was in the proximal segment of LAD;3MBs in the first diagonal branch;4MBs in the first obtuse marginal branch,1MB in posterior descending artery ofright coronary artery. The diameter and stenosis rate of MCA of both incomplete MB andcomplete MB in diastole and systole phase was1.93mm,1.71mm,4.7%,20.4%and2.21mm,1.63mm,8.1%and33.7%. It was statistically significant difference of diameterchange and stenosis rate between these two groups (P=0.008, P=0.014). Atherosclerosislesion was evidenced in8incomplete MB（34.78%） and15complete MB（42.86%）at theproximal segment of MB, and there were no significant difference between two groups(P=0.339).Conclusions: Complete MB induced the narrowing of MCA more serious than incompleteMB, and last longer. DSCTA can vividly display the incomplete and complete myocardialMB, accurately evaluate the shape change of MB-MCA in diastole and systole phase anddetect the atherosclerosis lesion in the proximal segment of MB. Chapter Ⅱ Diagnosis of myocardial bridges: a comparison betweencomputed tomography and invasive coronary angiographyObjective: To assess the evaluation of dual-source CT coronary angiography (CTA) indiagnosing myocardial bridges, and compared with invasive coronary angiography (CAG).Materials and Methods: Analysis of83cases simultaneously underwent CTA and CAGexam. CTA and CAG images were analyzed by two cardiovascular and interventionalradiologists who did not know the results of CTA and CAG. Calculate the detection rate ofmyocardial bridges diagnosed in CTA and CAG and compared the difference using χ2test.Results:⑴CTA detected41cases and a total of48myocardial bridges, the rate was49.4%(41/83).20were incomplete MB and28were complete MB.29located in themiddle left anterior descending artery,11in the distal left anterior descending artery, two in the posterior descending artery of right coronary, one in the first acute margial branch,three in the first obtuse marginal branch, one in the intermidiate branch, one in the firstdiagonal branch; and7cases with double myocardial bridge.⑵CAG revealed19patientsand a total of19myocardial bridges which were the same as detected in CTA examination,the detection rate was22.9%(19/83), and16located in the middle left anterior descendingartery,2located in the distal left anterior descending artery, one in the posterior descendingartery of right coronary artery. Compared the difference of detection rate between CTA andCAG, there were significant difference (P <0.001).Conclusions: CT coronary angiography can display the anatomy relationship betweencoronary artery and myocardium directly and non-invasive, which were better than CAG,but CAG was helpful at the evaluation of hemodynamic change. Chapter Ⅲ First-pass myocardial perfusion of the patients with isolatedmyocardial BridgeObjective: To investigate the first-pass myocardium perfusion (MP) of the patients withisolated MB on dual source CT coronary angiography (CTA) compared with normalcontrol cases.Materials and Methods:42cases with isolated MB of LAD on CTA were enrolled as thecase group (MB group), and all cases with the symptom of chest pain. According with MBtype and degree of systolic narrowing, there were subgroups (complete myocardial bridgegroup and incomplete myocardial bridge group, stenosis≥50%group and systolic stenosis<50%).20patients with normal coronary arteries on CTA were enrolled as the controlgroup. All patients were scanned with retrospective ECG-gated technique and reconstructedthe optimal systolic (30%-40%RR) and diastolic (65%-75%RR) images, slice thickness 0.75mm, increment0.5mm, reconstruction kernel B26f. The systolic and diastolic imageswere sent into the Terry workstation, and measured the segmental myocardial perfusion inHounsfield units (HU) with semiautomated method for17segments American HeartAssociation. The region of myocardium supplied by the left anterior descending artery wassegment1,2,7,8,13,14and17, calculated the average CT value as the MP. Measured theattenuation of the aorta artery (AA) at the root, and then calculated the corrected MP(c-MP).Results:(1) The CT value of AA in control group was367.1HU, and398HU in MB group,which was positively correlated with the myocardium average CT value (r=0.768-0.854，P＜0.001).(2) The myocardium CT value and c-MP of MB group and control group at diastolic phasewere94.0HU and96.0HU (p=0.216),0.236and0.263(P <0.001), respectively; themyocardium CT value and c-MP of MB group and control group at systolic phase were89.3HU and94.6HU (P<0.001),0.225and0.259(P<0.001), respectively.(3) The myocardium CT value of complete MB group at diastolic and systolic phase were90.9HU and86.5HU, of incomplete MB group were100.8HU and95.7HU (P＜0.05)。Thec-MP of complete myocardial bridge group in diastole and systole were0.235and0.224,the incomplete myocardial bridge group was0.240and0.228, and there were no significantdifference (P＞0.05), but both were much smaller than the control group (P＜0.05).(4) The myocardium CT value of stenosis≥50%group at diastolic and systolic phase were91.7HU and87.2HU, of stenosis <50%group were96.9HU and92.1HU (P＜0.05)。Thec-MP of stenosis≥50%group in diastole and systole were0.234and0.223, the stenosis<50%group were0.239and0.227, and there were no significant difference (P＞0.05), butboth were much smaller than the control group (P＜0.05).Conclusions: By measuring the diastolic and systolic myocardium CT value of the patientswith isolated MB can be evaluate the blood supply to a certain extent. The average CT ofmyocardium was lower than the control group in the patient with isolated myocardial bridge of LAD with the symptom of chest pain, more obvious in MB group and systolicstenosis≥50%group.