iDOSE⁴ 기법을 적용한 측두골의 확대영상 검사 시, DFOV 크기에 따른 영상의 질과 선량감소에 대한 연구

• 영문명: Study on Image Quality and Dose Reduction according to DFOV Size when Examining the Magnified Image of the Temporal Bone using the iDOSE⁴ Technique
• 발행기관: 대한CT영상기술학회
• 저자명: 오동준(Dong Jun Oh) 윤승민(Seung Min Yun) 이숙희(Sook Hee Lee) 김형기(Hyung Ki Kim)
• 간행물 정보: 『대한CT영상기술학회지』대한전산화단층기술학회지 제14권 제2호, 187~197쪽, 전체 11쪽
• 주제분류: 의약학 > 방사선과학
• 파일형태: PDF
• 발행일자: 2012.11.30

국문 초록

목적 측두골의 확대영상 검사 시, iDOSE 기법을 적용하여 Small DFOV로 재구성한 확대영상과 Zoom factor를 이용한 확대영상을 비교 평가하여, 선량의 증가없이 영상의 질을 개선하고 이를 임상에 적용하고자 한다. 대상 및 방법 CT장치는 128-MDCT(Injenuity 128, Philips Medical System, Netherlands)를 사용하였으며, 재구성방법과 DFOV 크기에 따른 공간분해능과 노이즈의 측정을 위해 AAPM(American Association of Physcists in Medicine, 이하 AAPM) 팬텀을 이용하여 EBW v3.5(extend brilliance workspace version 3.5, 이하 EBW)로 측정하였다. DFOV의 크기와 재구성 방법이 화질에 미치는 영향을 알아보기 위해서, DFOV 크기는 80mm와 180mm를 비교 측정하였고, 재구성 방법은 FBP와 iDOSE(Ievel 1~4)를 측두골검사 Protocol에 준하여 AAPM 팬텀을Scan하였다. 임상적용에 따른 평가는 수술 및 진단목적으로 측두골CT를 검사한 환자 10명을 대상으로, iDOSE 기법을 적용하여 Small DFOV로 재구성한 확대영상과 Zoom factor를 이용한 확대영상의 화질을 정성적으로 평가하였고, iDOSE 기법을 적용하여 Small DFOV로 재구성한 확대영상의 MPR coronal 영상의 질을 평가하였다. 결과 AAPM 팬텀의 공간분해능 블록의 시각적인 Hole test결과 DFOV 크기 80mm에서 재구성 방법에 따른 공간분해능은 1.0mm로 동일하였고, DFOV의 크기 l80mm에서 1.0~1.25 mm까지 식별 가능하였다. PSF를 이용한 MTF 측정결과 DFOV 크기 80mm에서 MTF 50%는 13.0~13.3lp/cm. MTF 10%는 14.1~14.4lp/cm로 측정되었고, DFOV 크기 180mm에서 MTF 50%는 7.2.~8.3lp/cm. MTF 10%는 10.6~11.9 lp/cm로 측정되었다. Hole test와 MTF 측정결과 Small DFOV에서의 공간분해능이 높아졌으며, 재구성 방법에 따른 공간분해능의 차이는 근소하였다. 하지만 180mm의 DFOV에서의 공간분해능은 iDOSE의 Level이 올라갈수록 낮게 측정이 되었다. AAPM 팬텀의 노이즈 측정결과 FBP로 재구성한 DFOV 크기 80mm와 180mm에서의 노이즈의 측정치는 432.4~247.8이고, iDOSE Level 4로 재구성한 DFOV 크기 80mm와 180mm에서의 노이즈의 측정치는 287.5~185.3 측정이 되어 DFOV가 작을수록 iDOSE의 노이즈제거 효과가 높았다. 이를 임상에 적용하여 측두골의 확대영상을 평가한 결과 Small DFOV와 iDOSE 기법 Level 4를 적용하여 재구성한 측두골의 확대영상이 임상적으로 높게 평가가 되었고, MPR coronal영상의 질이 개선되었다. 결론 측두골의 확대영상 검사 시, Small DFOV의 적용에 따른 장점인 공간분해능의 향상을 최대화하였고, 이에 따른 노이즈의 증가를 iDOSE의 적용으로 최소화하여 영상의 질을 개선할 수 있었다. 이와 더불어 측두골의 MPR coronal 확대영상의 질이 향상되어 Direct coronal scam으로 인한 추가적인 선량을 감소할 수 있었다.

영문 초록

I. Purpose When examining the magnified image of the temporal bone, by comparatively evaluating both the magnified image restructured with Small DFOV by applying the iDOSE technique and also the magnified image using Zoom factor, the quality of the image was improved without increase in dosage and subsequently applied clinically. II. Meterial and Methods For the CT device, the 128-MDCT(Injenuity 128, Philips Medical System, Netherlands) was used, while, spatial resolution and noise according to restructure method and DFOV size was measured through the EBW v3.5 by using AAPM (American Association of Physcists in Medicine, hereafter AAPM) Phantom. To find out how the DFOV size and restructure method affects image quality, the DFOV size was comparatively measured both in 80 mm and 180 mm, while, for the restructure method, AAPM Phantom was scanned by basing FBP and IDOSE(Lvel1~4) on temporal bone examination protocol. Evaluation following clinical application included both qualitatively evaluating the magnified image restructured through Small DFOV by applying the iDOSE technique and also the magnified image quality using Zoom Factor, with 10 patients examined for their temporal bone CT for operation and diagnosis purposes at the subject group. Also the image quality of the MPR coronal magnified image restructured through the Small DFOV by applying the iDOSE technique was evaluated. III. Result Tue results of the visual hole test of the spatial resolution block of the AAPM Phantom revealed that, at DFOV size 80 mm, spatial resolution by restructure method was the same at 1.0 mm, while at DFOV size 180 mm, it was differentiable at 1. 0 to 1. 25 mm. The results of the MTF measurement using PSF revealed that, at DFOV size 80 mm, MTF 50% was 13.0 to 13.3lp/cm. At MTF 10%, it was measured to be 14.1 to 14.4lp/cm and, at DFOV size 180mm, MTF 50% was 7.2. to 8.3lp/cm. MTF 10% was measured at 10.6 to 11.9p/cm. The hole test and MTF measurement results showed the spatial resolution at Small DFOV increasing, while the difference in spatial resolution according to restructure method was only slight. However, the spatial resolution at DFOV 180 mm was measured lower as iDOSE levels became higher. The noise measurement results of the AAPM phantom revealed that the noise values at DFOV size 80mm and 180mm restructured with FBP to be 432.4 to 247.8, while the noise values at DFOV sire 80 mm and 180mm restructured with iDOSE Level 4 to be at 287.5 to 185.3, thereby displaying that the smaller the DFOV, the higher the noise removal effect of the iDOSE. After evaluating the magnified image of the temporal bone by applying the results clinically, the magnified image of the temporal bone restructured by applying Small DFOV and iDOSE technique Level 4 was highly evaluated and also the MPR coronal image was improved. IV. Conclusions When examining the magnified image of the temporal bone, the improvement of spatial resolution, considered an advantage by applying Small DFOV, was maximized, and the subsequent increase in noise was minimized by applying iDOSE, so that image quality was improved. Also, because the quality of the magnified MPR coronal image of the temporal bone was improved, additional dosage resulting from direct coronal scan could be reduced.

목차

Abstract

Ⅰ. 서론

Ⅱ. 대상 및 방법

Ⅲ. 결과

Ⅳ. 고찰

Ⅴ. 결론

참고문헌

국문초록

키워드

Temporal bone Display field of view Zoom factor dosage