Clinical Application Of Low Doses Of Flash CT Coronary Angiography

Part I Preliminary Study on the Assessment of Coronary Artery Stenosis Diseases Using SOMATOM Definition CT Flash ScansObjectiveTo evaluate the value of SOMATOM Definition Flash CT scanning in the assessment of coronary artery stenosis diseases.Materials and methods52patients underwent computed tomography angiography exams using SOMATOM definition flash scans in our study; and CT findings were retrospectively reviewed, then compared with the results of coronary artery gngiography. The degree of stenosis in coromary artery were divided into three groups according to the range of obstruction on vascular cavity, mild stenosis (<50%), severe stenosis (>75%), and the rest were moderate stenosis. Grounding on the criterion of American Heart Association, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the diagnosis on coronary artery stenosis with CTA were analyzed.χ2test was used, and P<0.05was considered statistically significant.ResultsThe diagnosis sensitivity, specificity, positive predictive value, negetive predictive value and accuracy of coronary artery stenosis with Flash CT scanning were84.3%,95.7%,89.7%,93.2%,and92.2%, respectively. And the effective radiation dose was0.98±0.39mSv. There was no significant difference in the discovery of moderate and severe coronary artery stenosis between Flash CT and CAG(P=0.344and0.453, respectively); While there was significant difference in the diagnosis of mild coronary artery stenosis (P=0.041). ConclusionsAs a noninvasive diagnostic technique, Flash CT angiography is of great valuable on the diagnosis of coronary artery stenosis, especially for the diagnosis of moderate and severe coronary artery stenosis. And it’s effective radiation dose is very low. Part Ⅱ Application of low kilovoltage and IRIS reconstruction of Flash CT coronary angiography in overweight patientsObjectiveTo evaluate the image quality and the radiation dose of Flash CT coronary angiography using low kilovoltage and IRIS reconstruction in overweight patients.Materials and methodsOne hundred patients with body mass index (BMI) of25.0-30.0kg/m2underwent Flash CT with tube voltage of120kVp (Group A, n=50) and100kVp (Group B, n=50), while the images of group B were rebuilt with IRIS as group C. fifty patients in group A were examined with120kVp, fifty patients in group B with100kVp, and fifty patients in group C, whose images were rebuilt by IRIS from group B. All patients were scanned using adaptive sequence. According to the vascular segment to its image quality grading, analysis of the various vascular segments of the image can be assessed. The difference of coronary CT value and image noise (SD) were measured in aorta, left coronary and right coronary, while the SNR and contrast to noise ratio (CNR) were calculated and the radiation dose was recorded.The general information and radiation dose were compared between the two groups with t test. The mean intraluminal CT value, SD, SNR, and CNR were compared among the three groups with one-way analysis of variance. The image quality of coronary artery segments was compared in three groups using rank sum test.The different scores of image quality were compared among the three groups with χ2test. The interobserver agreement was determined by Kappa statistics.ResultsThere was no significant difference in Coronary artery segment image quality overall scores among the three groups (H=5.872, P>0.05).There was significant difference in excellent images among3groups (χ2=7.604, P<0.05). There was significant difference between group A and group B (χ2=7.534, P<0.0167), and the group A was better than the group B; While there was no significant difference between group A and group C (χ2=1.838, P>0.0167). There was significant difference in the mean intraluminal attenuation, image noise, SNR, and CNR among3groups (P<0.05). The mean intraluminal attenuation of group B and group C was significantly higher than that of group A. Image noise was the greatest and CNR was the lowest in the group B, while SNR of group C was the highest. The effective dose was (3.5±0.7) mSv in group C and (8.6±1.3) mSv in group A (t=-16.91, P<0.05).ConclusionsBetter image quality and lower radiation dose can be got by using Low kilovoltage and IRIS reconstruction for overweight patients in flash CT coronary angiography.