Evaluation of peritumoral fiber structures of N-ethyl-N-nitrosourea-induced rat brain glioma using Diffusion tensor MR imaging : comparison between vector map and histology

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We investigated fiber structures in the peripheral zone of N-ethyl-N-nitrosourea (ENU)-induced rat brain glioma by comparison between diffusion tensor MR (DT-MR) images and neurofilament (NF) immunostained histological sections.In this study, six Fisher-334 rats, which had been treated transplacentally with ENU, underwent in vitro MR imaging. All procedures met institutional Laboratory Animal Care and Use Committee approval. The experiments were performed on a horizontal 7T/40 cm magnet equipped with a 12cm gradient set up to 400mT/m interfaced to an experimental NMR system. The fixed brain was put into the tube filled with 0.1M phosphate buffer for in vitro DT-MR imaging. Acquisition parameters were 2000/36/12-14 (TR msec/TE msec/averaging), 24mm field of view, 0.5mm slice thickness, 256x256 scan matrix (0.0938x0.0938x0.5mm^3). A data set of diffusion-weighted images with b-value=1027sec/mm^2 in six different noncolinear directions and T2-weighted images was obtained. From the diffusi … More on-tensor data, DT-MR imaging-based color maps and vector maps were generated. After DT-MR imaging, neurofilament immunohistochemistry was performed using the avidin-biotin-peroxidase complex method. We visually evaluated peritomoral white matter architecture described by the vector maps in comparison with corresponding neurofilament (NF) immunostained histological sections.We obtained the following results. (1)In normal white matter, the vector map could depict well-ordered vector bars corresponding ordered NF structures in immunostained histological sections. (2)The vector map could clearly show peritumoral widening and disruption of the vector bars along the border between normal white matter and tumor, which were confirmed by the histological sections. (3)The vector maps showed well-ordered vector bars in the peritumoral area with abnormal hyper intensity on T2-weighted images, where histology revealed normal well-ordered NF bundles without tumor cells in the area. (4)The vector map could not fully describe scattered residual NF bundle pieces in the tumor. Less