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3.0T 자기 공명 영상에서 강자성 임플란트로 인한 자화감수성 인공음영에 대한 WARP 기법의 적정한 VAT값에 대한 고찰 KCI 등재
A study on the proper VAT of WARP technique for susceptibility artifact image due to ferromagnetic implant in 3.0T Magnetic Resonance Imaging
pp.111-118
목 적 : 3.0T 자기 공명 영상에서 강자성 임플란트로 인해 발생한 자화감수성 인공음영에 대한 시퀀스별 WARP기법의 적정한 VAT(view angle tilting)값을 알아보았다.
대상 및 방법 : 자화감수성 인공음영(susceptibility artifact image)이 head용 워터 팬텀영상의 왜곡정도를 평가하기 위하여 head용 워터 팬텀에 강자성 임플란트(ferromagnetic implant)인 금속 와이어를 부착하여 영상을 획득하였다. 진행하였고(VAT(view angle tilting)) Warp를 사용하였다. 사용된 장비는 3.0T MRI system(MAGNETOM Skyra, Siemens, Munich, Germany)이었으며 20ch head/neck coil을 사용하여 TSE T2, TSE T1, FLAIR, Turbo IR T1 시퀀스에 WARP를 적용하여 VAT를 0~100% 범위내에서 10%씩 변화하여 각각 24개의 axial 영상을 얻었다. TSE T2 영상변수는 TR/TE 4410ms/79ms, Matrix 512×291이었으며, TSE T1 영상변수는 TR/TE 693ms/10ms, Matrix 512×291이었으며, Turbo IR T1 영상변수는 TR/TE 2000ms/9.5ms, Matrix 384×307이었으며, FLAIR 영상변수는 TR/TE 9000ms/96ms, Matrix 384×180이었다. 시퀀스별로 slice thickness 4mm, slice gap 0.4mm, NEX 1, bandwidth는 500Hz 였다. 정량평가는 팬텀영상의 대부분을 ROI로 설정 하여 표준편차를 구하였다. 정성 평가는 팬텀 영상 내에 dark area크기, image blurring 정도를 5점 척도로 하여 영상의 변화가 없는 경우 1점, 영상의 질이 약간 우수한 경우 2점, 보통 3점, 우수한 경우 4점, 매우 우수한 경우 5점으로 숙련된 방사선사 3명이 관찰 후 평가하였다.
결 과 : 정량분석으로 TSE T2와 TSE T1의 표준편차(SD)는 VAT 10%에서 VAT 적용전보다 많은 감소를 보였으며, VAT가 증가 할수록 감소하는 경향을 나타냈다. 그러나 IR 계열의 FLAIR와 Turbo IR T1은 WARP의 적용에 따른 영상차이가 없었다. 변동계수는 모든 시퀀스에서 30%이하였다. 또한 VAT 변화에 따라 영상의 위치변화도 나타났다. 정성분석으로 TSE T2는 VAT가 30~60%일 때 우수한 것으로 나타났고, TSE T1은 VAT가 10~70%일 때 우수한 것으로 나타났다. FLAIR와 Turbo IR T1은 WARP사용에 따른 영상의 변화가 없었다
결 론 : WARP는 TSE T2와 TSE T1의 자화감수성 인공음영을 줄이는데는 매우 효과적인 영상기법이었다. 그러나 WARP는 VAT를 증가시키면 image blurring도 증가함으로 VAT값을 최소화해서 사용 되어져야 할 것으로 사료된다.
Purpose: The proper VAT (view angle tilting) of WARP technique was examined according to each sequence for susceptibility artifact image caused by ferromagnetic implant in 3.0T magnetic resonance imaging.
Material and Methods : The experiment was peformed by attaching ferromagnetic metal wire, to the water phantom for head in order to evaluate how much susceptibility artifact image distorted. The image acquisition system was 3.0T MRI system(MAGNETOM Skyra, Siemens, Munich, Germany) and 20ch head/neck coil was used. WARP was applied to TSE T2, TSE T1, FLAIR, and Turbo IR T1 sequence, it was gradually changed by 10% in the range of 0~100%. And 24 axial images were obtained respectively. TSE T2 image parameter was TR/TE 4410ms/79ms, Matrix 512×291. And TSE T1 image parameter was TR/TE 693ms/10ms, Matrix 512×291. Turbo IR T1 image parameter was TR/TE 2000ms/9.5ms, Matrix 384×307. FLAIR image parameter was TR/TE 9000ms/96ms, Matrix 384×180. Slice thickness 4mm, slice gap 0.4mm, and NEX 1, and bandwidth was 500Hz according to each sequence. In the quantitative evaluation, ROI was defined on most of phantom image, and then standard deviation was calculated. In the qualitative evaluation, dark area size and image blurring level in the phantom axial image was observed and then was evaluated by 3 professional radiologic technologists using a 5-point scale: 1, no change; 2, slightly excellent image; 3, fairly excellent; 4, quite excellent; 5, very excellent.
Results : The quantitative analysis showed that the standard deviation (SD) of TSE T2 and TSE T1 more decreased in VAT 10% than that before applying VAT, and showed a decreasing tendency as VAT was increased. However, there was no image difference according to application of WARP in case of Turbo IR T1 and FLAIR. Coefficient of variation(CV) was less than 30% in all sequences. In the mean while, image shift was increased consistent with VAT. The qualitative analysis showed that TSE T2 was excellent in range of 30~60%, TSE T1 was excellent 10~70% in VAT. Image didn't change in FLAIR and Turbo IR T1 according to the use of WARP. In the quantitative evaluation, ROI was defined on most of phantom image, and then standard deviation was calculated. In the qualitative evaluation, dark area size and image blurring level in the phantom axial image was observed and then was evaluated by 3 professional radiologic technologists using a 5-point scale: 1, no change: 2, slightly excellent image: 3, fairly excellent: 4, quite excellent: 5, very excellent.
Conclusion : WARP was a very effective image technique for reducing susceptibility artifact image on TSE T2 and TSE T1. However, it is thought that WARP with minimized VAT should be used because image blurring also increases if VAT is increased.
Ⅱ. 대상 및 방법
1. 실험 대상
2. 장비 및 검사방법
3. 영상의 분석
Ⅲ. 결 과
1. 정량적 분석(Quantitative analysis)
2. 정성적 분석(Qualitative analysis)
Ⅳ. 결론 및 고찰
Ⅴ. 참고문헌
