7テスラMRIによる脳神経画像診断の新しい展開

Neuroimaging Using Ultrahigh-Field Magnetic Resonance Imaging at 7 Tesla: Current Concepts

はじめに

　MRIの進歩はとどまるところを知らず，超高磁場7テスラ（T）MRI（¹Hの共鳴周波数：300MHz）の時代がいよいよ始まろうとしている。ヒト用7T MRIは世界で約40台が稼働しており，本学にも国内で2台目の7T装置（MR950，GE Healthcare）が導入され，2011年4月より稼動を開始した。本稿では7T MRIの特徴と今後の可能性について，われわれの初期経験を交えて概説する。

Abstract

　The introduction of ultrahigh-field MRI at 7 tesla (7T) has increased the interest in the use of neuroimaging techniques in clinical research. The high signal-to-noise ratio and profound susceptibility effect at 7T can remarkably improve the spatial resolution and image contrast of structural imaging, susceptibility imaging, and functional imaging techniques, whereas the heating effects of the radio frequency and the inhomogeneities of the local magnetic field can have substantial negative effects on parameter setting, acquisition time, and image quality. T₁ prolongation at 7T can improve the enhancement effects of gadolinium agents and the inflow effects on MR angiography and arterial spin labeling. Ultrahigh-field MRI is expected to have a high clinical impact in the near future; however, further technological advances tailored to ultrahigh-field systems as well as the accumulation of scientific evidence will be needed to establish its clinical significance.