CT 대장조영술에서 적응적 통계적 영상 재구성법 (ASiR)과 베오 (Veo)에 대한 연구: 저선량 CT에서 영상의 질과 진단력의 비교 평가

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서울대학교 대학원
학위논문 (석사)-- 서울대학교 대학원 : 의학과, 2012. 2. 한준구.
Rationale and Objectives: To evaluate the diagnostic performance of CT colonography (CTC) reconstructed with different levels of ASiR (adaptive statistical iterative reconstruction, GE Healthcare) and Veo (model-based iterative reconstruction, GE Healthcare) at various tube currents in detection of polyps in porcine colon phantoms.

Materials and Methods: Five porcine colon phantoms with 46 simulated polyps were scanned at different radiation doses (10, 30, 50mAs) and were reconstructed using FBP (filtered back projection), ASiR (20, 40, 60%) and Veo. Eleven data sets for each phantom (10mAs-FBP, 10mAs-20% ASiR, 10mAs-40% ASiR, 10mAs-60% ASiR, 10mAs-Veo, 30mAs-FBP, 30mAs-20% ASiR, 30mAs-40% ASiR, 30mAs-60% ASiR, 30mAs-Veo, 50mAs-FBP) yielded a total of 55 data sets. Polyp detection sensitivity and confidence level of two independent observers were evaluated with the McNemars test, Fishers exact test and receiver operating characteristic curve analysis. Comparative analyses of overall image quality score, measured image noise and interpretation time were also performed.

Results: Per-polyp detection sensitivities and specificities were highest in 10mAs-Veo, 30mAs-FBP, 30mAs-60% ASiR and 50mAs-FBP (sensitivity, 100%; specificity, 100%). The Az values for the overall performance of each data set was also highest (1.000) at 50mAs-FBP, 30mAs-FBP, 30mAs-60% ASiR and 10mAs-Veo. Images reconstructed with ASiR showed statistically significant improvement in per-polyp detection sensitivity as the % level of per-polyp sensitivity increased (10mAs-FBP vs. 10mAs-20%, p=0.011; 10mAs-FBP vs. 10mAs-40%, p=0.000; 10mAs-FBP vs. 10mAs-60%, p=0.000; 10mAs-20% vs. 40%, p=0.034). Overall image quality score was highest at 30mAs-Veo and 50mAs-FBP. The quantitative measurement of the image noise was lowest at 30mAs-Veo and second lowest at 10mAs-Veo. There was a trend of decrease in time required for image interpretation as the % level of ASiR increased, and ASiR or Veo was used instead of FBP. However, differences from comparative analyses of overall image quality score, measured image noise and interpretation time did not reach statistical significance.

Conclusion: ASiR and Veo showed improved diagnostic performance with excellent sensitivity and specificity with less image noise and good image quality compared with FBP reconstruction of same radiation dose. Our study confirmed feasibility of low dose CTC with iterative reconstruction as a promising screening tool with excellent diagnostic performance similar to that of the standard dose CTC with FBP.
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College of Medicine/School of Medicine (의과대학/대학원)Dept. of Medicine (의학과)Theses (Master's Degree_의학과)
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