확산텐서영상을 이용한 확산 주축의 고유치 영상 재구성
Image Reconstruction of Eigenvalue of Diffusion Principal Axis Using Diffusion Tensor Imaging
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목적 : 확산텐서자기공명영상(DT-MRI : Diffusion Tensor Image)을 이용하여 확산의 주축을 구성하는 세 성분에 대한 고유치(eigenvalue)의 영상을 구현해 보고자 하였다. 대상 및 방법 : 고유치 영상을 구현하기 위해서 3.0 테슬러 MRI(Magnetic Resonance Imaging)를 이용하여 확산텐서영상을 얻었으며, Moore-Penrose pseudo-inverse 방법과SVD(single value decomposition) 방법을 이용하여 확산 주축을 계산하였다. 이 과정을 픽셀단위로 반복적으로 계산하여 새로운 확산 주축 영상들을 만들었으며, 이 확산 주축 영상들과분할 비등방성 영상의 관계를 조사하였다. 결과 : 확산텐서영상 기법으로 얻어진 확산텐서영상을 이용하여, 세 방향의 확산 주축에 대한고유치 영상을 구성하였으며, 고유치 영상들과 분할 비등방성 영상을 함께 분석함으로써, 뇌의해부학적 구조물에 따른 분할 비등방성 값의 차이를 확인할 수 있었다. 또한, 확산 주축에 대한고유치의 변화에 대한 컴퓨터 모의실험에서, 변화하는 고유치에 따른 분할 비등방성 값의 변동추이를 알아볼 수 있었다. 그리고 확산 주축의 크기가 비등방성을 좌우하는 것이 아니라, 세 확산 주축의 조합으로 비등방성의 정도를 표현한다는 것을 확인할 수 있었다. 결론 : 확산 주축 방향의 고유치들을 분리하여 영상화 함으로써, 뇌의 병변에 의한 비등방성의변화의 원인이 확산 주축의 어떠한 변화에 의해 발생하는 것인지 확인할 수 있을 것으로 기대된다.
Abstract
Purpose : The objective of this work to construct eigenvalue maps that have information of magnitude of three primary diffusion directions using diffusion tensor images. Materials and methods : To construct eigenvalue maps, we used a 3.0T MRI scanner. We also compared the Moore-Penrose pseudo-inverse matrix method and the SVD (single value decomposition) method to calculate magnitude of three primary diffusion directions. Eigenvalue maps were constructed by calculating of magnitude of three primary diffusion directions. We did investigate the relationship between eigenvalue maps and fractional anisotropy map. Results : Using Diffusion Tensor Images by diffusion tensor imaging sequence, we did construct eigenvalue maps of three primary diffusion directions. Comparison between eigenvalue maps and Fractional Anisotropy map shows what is difference of Fractional Anisotropy value in brain anatomy. Furthermore, through the simulation of variable eigenvalues, we confirmed changes of Fractional Anisotropy values by variable eigenvalues. And Fractional anisotropy was not determined by magnitude of each primary diffusion direction, but it was determined by combination of each primary diffusion direction. Conclusion : By construction of eigenvalue maps, we can confirm what is the reason of fractional anisotropy variation by measurement the magnitude of three primary diffusion directions on lesion of brain white matter, using eigenvalue maps and fractional anisotropy map.
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