64 Slice MDCT에서 HR Variation이 Image Quality에 미치는 영향에 대한 고찰

The Effect of Heart Rate Variation for CT Coronary Angiography : 64 slice MDCT is also Troublemaker or Troubleshooter?

Purpose 16 slice MDCT is Widely used for coronary CT angiography, however it is well known that image quality is more affected the variation of heart rate than heart rates. Recently, 64 slice MDCT has been introduced, it has the merit of faster scan time. Therefore, it might be improve image quality for minimizing the variation of heart rate during scan time. The purpose of this study is, (a) to analyze the variation of heart rate according to time-course during CT scanning (b) to evaluate how to impact to the image quality by the differences of heart rate variation. Materials and Methods Total 200 patients were enrolled in this study. 100 patients who underwent cardiac CT With 16 MDCT from Jan 2004 to Jul 2004(74 men, 26 women; mean age 55.15±12.75 years), 100 patients who underwent cardiac CT With 64 MDCT from Jun 8, 2006 to Jun 30, 2006(68 men, 32 women; mean age 58.4±11.56 years). Mean heart rate is no significant difference between two groups(16 MDCT 71.04±3.52bpm, 64 MDCT 69.31±4.71bpm). Equipments were used 16 MDCT(Mx8000 IDT, Philips) and 64 MDCT(Brilliance 64, Philips) which are the same rotation times(420msec, i.e. temporal resolution is same as 53msec). We recorded the variation of HR during pre and post scan as well as scanning period. We evaluated the image quality by dividing several groups according to the variation of HR ; Group I(0-5bpm), Group II(11-15bpm), Group III(11-5bpm), Group IV(16-20bpm), Group V(above 20bpm). The results are also compared for the evaluation of quality between 16 MDCT and 64 MDCT. For the qualitative analysis of image quality, we used 4 grade scoring system(Excellent : 4 points, Good : 3 points, Fair : 2 points, Bad : 1 point). For the quantitative analysis, we analyzed the presence and frequency of banding artifacts including stair-step artifact and acceleration artifact. Results The result of mean HR variation on 64 MDCT was significantly diminished comparing With 16 MDCT(5.48±4.20 bpm vs 10.31±5.90, P<0.05). For the qualitative analysis of image quality. The overall score of 64 MDCT is statistically larger than that of 16 MDCT(3.41±0.7 VS 2.84±0.9, P<0.05). For the quantitative analysis the frequency of stairstep artifacts is markedly occurred on 16 MDCT(64 MDCT: 0.5±1.04, 16 MDCT: 2.4±3.2, P<0.05). Furthermore, acceleration artifact was extremely rare on 64 MDCT (64 MDCT: 1, 16 MDCT : 11, P<0.05). Conclusion In this study, we suggest that 64 MDCT have the merit to improve image quality by reducing scan time and minimizing the variation of heart rate comparing With 16 MDCT. We conclude that 64 MDCT will be play an important role for the evaluation of ischemic heart disease due to markedly eliminating acceleration artifact which is frequently occurred in patients who could not sufficient breath-hold.