체질량 지수 및 관전압 변화에 따른 CT 관상동맥 조영술의 영상의 질 및 방사선 피폭량 비교 = Image Quality and Radiation Exposure in Coronary CT Angiography According to Tube Voltage and Body Mass Index

다국어 초록 (Multilingual Abstract)

Purpose: To investigate the image quality and radiation dose of a coronary CT angiography (CCTA) according to tube voltage and body mass index (BMI).
Materials and Methods: This study included 139 patients who underwent CCTA using a retrospective electrocardiography-gating technique. A total of 48 patients (BMI <2 5, group A) were examined with 100 kVp, 45 patients (BMI > 25, group B) with 120 kVp, and 46 patients (BMI < 25, group C) with 120 kVp. Attenuation and image noise of the aorta and coronary arteries was measured. Moreover, the image quality of 9 coronary segments was graded on a scale of 1-5, where grade 4 or 5 was considered to be diagnostic. Image quality parameters and radiation dose were compared using a t-test or Chi-squared test.
Results: Vessel attenuation in group A was significantly higher than in groups B or C (group A, 592 ± 85 HU; group B, 437 ± 46 HU; group C, 469 ± 62 HU, p<0.001). Image noise was similar in group A and group B (23 ± 5 HU versus 22 ± 6 HU, p=0.427), but significantly higher in group A compared to group C (23 ± 5 HU versus 17 ± 4 HU, p<0.001). A significant difference was observed in the signal-to-noise ratio between the three groups (group A, 24 ± 6; group B, 19 ± 3; group C, 27 ± 5: p<0.05). Moreover, the contrast-to-noise ratio was significantly higher in group A than group B (group A 18 ± 5 versus group B 14 ± 3, p < 0.001) but not significantly different between group A and group C (group C 20 ± 4, p=0.127). The percentage of coronary segments with diagnostic image quality was 97.9% in group A, 96.0% in group B, and 99.0% in group C. The mean image quality score was 4.5 ± 0.5 in group A, 4.1 ± 0.4 in group B, and 4.2 ± 0,4 in group C (p<0.001). The effective radiation doses were 8.5 ± 0.8 mSv in group A, 14.3 ± 1.3 mSv in group B, and 14.9 ± 1.3 mSv in group C. A 42% reduction in mean effective radiation dose in group A was observed compared with groups B and C.
Conclusion: In patients with BMI less than 25 and a low-dose CCTA with 100 kVp leads to a significant reduction in radiation exposure without degradation of image quality.

국문 초록 (Abstract)

목적: 체질량 지수(Body mass index, 이하 BMI) 와 관전압의 변화에 따른 CT 관상동맥 조영술(Coronary CT angiography, 이하 CCTA)의 영상의 질 및 방사선 피폭량에 대하여 알아보고자 하였다.
대상과 방법: 64열 다중 검출 CT로 후향적 심동조화를 이용한 CCTA를 시행 받은 139명의 환자를 BMI 및 관전압에 따라 세 개의 군으로 나누었다[A군(n=48), BMI < 25, 100 kVp; B군(n=45), BMI > 25, 120 kVp; C군(n=46), BMI < 25, 120 kVp]. 대동맥 및 관상동맥 근위부의 조영 증강 정도와 잡음을 측정하였으며 관상동맥 9분절의 영상의 질을 1-5점으로 평가하였고 4점과 5점을 진단에 적합한 것으로 하였다. 각 환자군 간의 영상의 질 지표와 방사선 피폭량을 t-검정과 카이제곱 검정을 이용하여 비교하였다.
결과: 혈관의 조영 증강 정도는 A군에서 B군과 C군보다 높았다(group A, 592 ± 85 HU; group B, 437 ± 46 HU; group C, 469 ± 62 HU, p < 0.001). 영상 잡음은 A군과 B군 사이에는 유의한 차이가 없었으나(23 ± 5 HU와 22 ± 6 HU, p=0.427), A군에서 C군에 비해 유의하게 높았다(23 ± 5 HU 와 17 ± 4 HU, p < 0.001). 신호 대 잡음 비는 평균 A군 24 ± 6, B군 19 ± 3, C군 27 ± 5로 세 군 간에 각각 유의한 차이가 있었다. 조영 증강 대 잡음 비는 평균 A군 18 ± 5, B군 14 ± 3, C군 20 ± 4로 A군에서 B군에 비해 유의하게 높았으나(p < 0.001) A군과 C군 사이에는 유의한 차이가 없었다(p=0.127). 진단에 적합한 영상을 보인 관상동맥 분절은 A군 97.9%, B군 96.0%, C군 99.0%였으며 영상 질의 평균 점수는 A군 4.5 ± 0.5, B군 4.1 ± 0.4, C군 4.2 ± 0.4로 세 군 간에 각각 유의한 차이가 있었다(p < 0.001). 유효 방사선량은 A군 8.5 ± 0.8 mSv, B군 14.3 ± 1.3 mSv, C군 14.9 ± 1.3 mSv로, A군이 다른 두 군에 비하여 약 42% 낮았다.
결론: BMI가 25 이하인 환자에서 관전압을 100 kVp로 낮추어 CCTA를 시행하는 경우 진단에 적절한 영상을 얻을 수 있으며 효과적으로 방사선 피폭량을 줄일 수 있다.

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