ObjectiveTo explore the effect of snapshot freeze (SSF) on the image quality of coronary artery in 64 multislice spiral CT for patients with high heart rate. MethodsWe retrospectively analyzed the clinical data of 98 patients with an mean heart rate of ≥ 70 beats/min who underwent coronary CT angiography examination between August 2013 and February 2014. According to the inclusion criteria, 60 patients were included in our study. The image quality of standard reconstruction (STD) and motion-corrected (MC) reconstruction based on SSF platform were analyzed. The image quality was classified into 4 grades, and the image quality of coronary segments named according to AHA standard was evaluated. Then, we compared the image quality between the two different reconstruction methods. ResultsAltogether 180 coronary arteries and 795 coronary segments were evaluated. Before MC reconstruction, there were 133 (73.89%) arteries and 287 (36.10%) segments had pseudomorph, while after MC reconstruction, those two numbers were 89 (49.44%) and 150 (18.87%) (P<0.05). The right coronary artery (RCA) had a higher rate of pseudomorph and a lower image quality score[91.67% (55/60), 3.32±0.40] than left anterior descending artery[60.00% (36/60), 3.69±0.42] and left circumflex artery[70.00% (42/60), 3.44±0.55], especially the S2[90.00% (54/60), 2.45±0.85]. Overall image quality was higher with the use of MC reconstruction on per-artery level (P<0.05) and most of the per-segment level (P<0.05) compared with STD, especially for RCA and its segments (P<0.05). ConclusionSSF improves image quality of coronary artery in patients with high heart rate, especially for RCA.
ObjectiveTo assess the image quality and radiation dose of gemstone CT coronary angiography (CCTA) with low tube voltage and low concentration contrast medium. MethodsSixty-nine patients who underwent CCTA from January to March 2014 were randomly divided into group A and B. CCTA was performed in thirty-four patients in group A with tube voltage of 100 kV and concentration of contrast medium of 300 mgI/mL. And thirty-five patients in group B underwent CCTA with 120 kV and 370 mgI/mL. According to upgrading American Heart Association standard all segments and all vessels were evaluated. We measured the CT value of ascending aortic root, left main coronary artery, and the initial segment of left anterior descending branch, left circumflex, right coronary artery, and also adjacent tissues. Besides, we recorded CT dose volume index (CTDIvol) and the dose length product (DLP) and calculated effective radiation dose. ResultsThe image quality scores were not significantly different between two groups (P>0.05). The density in the contrast enhanced vessel lumens in group A were signifcantly higher than that in group B (P<0.05). There was no significant difference in signal to noise ratio and carrier to noise ratio between the two groups (P>0.05). Noise in group A was higher than that in group B (P<0.05). The CTDIvol and effective radiation dose in group A were significantly lower than those in group B (P<0.05). ConclusionThe combination of 100 kV with low concentration contrast medium (300 mgI/mL) still maintains the image quality, as well as significantly lowers the radiation dose and the dose of iodine.