構造を可視化する術中画像支援技術の開発 [in Japanese] Development of Advanced Image-guided Neurosurgery with Intraoperative MRI [in Japanese]
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術中MRIは, ブレインシフトを克服した正確なナビゲーションの実現, 脳腫瘍の摘出コントロール, 術中の合併症の早期発見に役立つ. その役割は, 術中の脳構造の可視化であり, 脳神経外科手術のquality assuranceといえる. 錐体路の可視化には, トラクトグラフィーが有用である. われわれは変形フュージョンと呼ばれる技術を開発し, 術前画像を術中画像へ適切に変形して重畳した. 術中の錐体路の内外側への偏移の推定が可能であった. 術中の出血性合併症について擬似血液を用いて血液の濃度と信号値の関係について評価した. Fast FLAIR法における信号値は良好な直線関係を認めた. 今後の普及が期待される.
Image-guided surgery has developed on the basis of navigation-technology born in the late 1980s, enhanced by improvements in various imaging modalities. Intraoperative MRI (iMRI) plays an important role in accurate navigation that is free from the influence of brain shift, allows fine resection control during the tumor surgery, and provides early detection of intraoperative complications. Thus, the role of iMRI is to visualize the intraoperative brain structure and function, namely, to serve as quality assurance (QA) for the neurosurgery. There are increasing number of reports related to iMRI, up to 290 at last count, with at least 200 units installed in ORs throughout the world at present.<br> Diffusion tensor imaging (DTI) and tractography enables visualization of the pyramidal tract intraoperatively. High magnetic-field MRI units are capable of conducting DTI to compensate for brain shift during surgery. Lower magnetic-field MRI units, however, are not as powerful. We have developed an advanced imaging technique, “reshape & fuse” in which preoperative images are fused appropriately to deformed intraoperative images using a non-rigid registration algorithm. Using this technique, we were able to successfully estimate the intraoperative shift of the pyramidal tract both toward the inside and outside of the brain.<br> Intraoperative hemorrhagic complications can be detected with iMRI, although characterization of the super acute hemorrhage on MRI has not been established yet. We investigated the relationship between blood concentration and MR signals, comparing among the values yielded by T1, T2 and fast FLAIR on various blood concentrations using artificial blood samples. Values of fast FLAIR had the best linearity among the three, suggesting that fast FLAIR is sensitive enough to detect a small amount of blood, and at the same time, able to estimate the concentration of blood in a mixture with CSF. This finding could lead to better visualization of intraoperative super acute hemorrhagic events.<br> Expanding iMRI and developing related imaging technologies would contribute greatly to the QA of neurosurgery, pushing forward the frontier for intraoperative visualization of the brain.
- Japanese Journal of Neurosurgery
Japanese Journal of Neurosurgery 23(11), 854-861, 2014
The Japanese Congress of Neurological Surgeons