SPECTによる脳機能解析

Brain function analysis using SPECT

　SPECTによる脳機能解析は，画像統計解析法の導入とMRIとの簡便な融合技術の発展により，最近著しく進歩した。画像統計解析法を用いた診断は，従来の視覚評価や関心領域設定法を客観性および精度において凌駕し，アルツハイマー病などの認知症の診断には必須の解析法となっている。また，MRIとSPECTの融合は，単にSPECTの異常部位の解剖学的位置の把握に用いられるばかりではなく，てんかん発作期と発作間欠期の脳血流SPECT像から，てんかん焦点部位をMRI上で診断するsubtraction ictal SPECT co-registered to MRI（SISCOM）や，MRIを用いたSPECTの部分容積効果補正などにも用いられている。

　Great advances have been recently made in brain function analysis using SPECT. Introduction of statistical image analysis after anatomic standardization and development of a simplified image fusion technique of MRI and SPECT brought these advances. Development of computer assisted analysis using three-dimensional stereotactic surface projection or easy Z-score imaging system based on statistical parametric mapping afforded objective and more reliable assessment of functional abnormalities by means of stereotactic coordinates than visual interpretation of raw tomographic images or a conventional region of interest technique. This stereotactic approach becomes essential to the evaluation of regional cerebral blood flow abnormality in dementia like Alzheimer's disease. Image fusion of MRI and SPECT is helpful not only for a grasp of the exact location of brain perfusion abnormality but also for application to subtraction ictal SPECT co-registered to MRI for diagnosing epileptic foci using interictal and ictal brain perfusion SPECT and to partial volume correction of SPECT using co-registered MRI.