Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Voxel-based Investigations of Phase Mask Effects on Susceptibility Weighted Images

화소 간 분석을 이용하여 자화율 가중 영상(SWI)에 나타난 위상 마스킹의 효과 분석

  • Hwang, Eo-Jin (Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University) ;
  • Kim, Min-Ji (Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University) ;
  • Kim, Hyug-Gi (Department of Biomedical Engineering, College of Electronic Information Engineering, Kyung Hee University) ;
  • Ryu, Chang-Woo (Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University) ;
  • Jahng, Geon-Ho (Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University)
  • 황어진 (경희대학교 의과대학 강동경희대학교병원 영상의학과) ;
  • 김민지 (경희대학교 의과대학 강동경희대학교병원 영상의학과) ;
  • 김혁기 (경희대학교 생체의공학과) ;
  • 류창우 (경희대학교 의과대학 강동경희대학교병원 영상의학과) ;
  • 장건호 (경희대학교 의과대학 강동경희대학교병원 영상의학과)
  • Received : 2012.11.08
  • Accepted : 2013.03.05
  • Published : 2013.03.31
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Abstract

To investigate effects of phase mask on susceptibility-weighted images (SWI) using voxel-based analyses in normal elderly subjects. A three-dimensional (3D) gradient echo sequence ran to obtain SWIs in 20 healthy elderly subjects. SWIs with two (SWI2) and four (SWI4) phase multiplications were achieved with positive (PSWI) and negative (NSWI) phase masks to investigate phase mask effects. The voxel-based comparisons were performed using paired t-tests between PSWI and NSWI and between SWI2 and SWI4. Differences of signal intensities between magnitude images and SWI4 were larger than those between magnitude images and SWI2s. Differences of signal intensities between magnitude images and PSWIs were larger than those between magnitude images and NSWIs. Moreover, the signal intensities from NSWI2s and NSWI4s were greater than those from PSWI2s and PSWI4s, respectively. More differences of signal intensities between NSWI4 and PSWI4s were found than those between NSWI2s and PSWI2s in the whole brain images. The voxel-based analyses of SWI could be beneficial to investigate susceptibility differences on the entire brain areas. The phase masking method could be chosen to enhance brain tissue contrast rather than to enhance venous blood vessels. Therefore, it is recommended to apply voxel-based analyses of SWI to investigate clinical applications.

이 연구의 목적은 영상의 화소 간 분석(voxel-based analysis)을 이용하여 자화율 가중 영상(SWI)에 나타난 위상 마스킹의 효과를 알아보는 것이었다. 20명의 정상 노인에서 SWI 영상의 정보를 획득하기 위하여 3차원 경사자장 에코 시퀀스를 이용하여 영상을 얻었다. SWI 영상에서의 위상 마스킹의 효과를 관찰하기 위해 원래의 경사자장 크기(magnitude) 영상에 위상 영상을 2번 곱한 SWI2 영상, 4번 곱한 SWI4 영상, 영상 내 정맥 혈관을 강조한 양의 위상 마스크 SWI 영상 (PSWI), 그리고 조직 부분을 강조한 음의 위상 마스크 SWI 영상(NSWI)을 만들었다. paired t-test를 이용한 PSWI와 NSWI간 신호강도의 차이, SWI2와 SWI4간의 신호강도의 차이, 그리고 경사자장 크기영상 영상과 위상 마스킹에서 얻은 SWI 영상의 신호강도의 차이를 voxel-based 분석으로 수행하였다. 신호 강도 차이는 magnitude과 SWI4 영상 간의 차이가 magnitude과 SWI2 영상 간의 차이보다 더 크게 나왔다. 또한, 신호강도 차이는 magnitude과 PSWI 영상 간의 차이가 magnitude과 NSWI보다 더 많았다. 그리고 NSWI2와 NSWI4간의 신호강도 차이가 PSWI2와 PSWI4간의 신호강도 차이 보다 더 크게 나타났으며, 그리고 NSWI4와 PSWI4간의 신호강도 차이가 NSWI2와 PSWI2간의 신호강도 차이보다 더 크게 나타났다. 위 실험은 화소 간 분석을 통한 SWI 영상 연구가 뇌 전체의 자화율 효과를 볼 때 매우 유용할 것이라는 사실뿐만 아니라, 각기 다른 위상 마스킹 방법을 응용함으로써 선택적으로 정맥 혈관 대비, 혹은 뇌 조직 대비를 강조할 수 있다는 사실을 입증하였다. 그러므로, 자화율 가중 영상의 화소 간 분석은 많은 임상 예에 적용될 수 있을 것이다.

Keywords

References

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