MRI誘導定位脳手術による密封小線源療法が有用であった微小グリオーマの1例

A Case of Glial Microtumor Treated with Brachytherapy Using MRI Guided Stereotactic System

I．はじめに

　近年，CT，MRIなどの画像診断技術の進歩により，各種のより微小な病変が検出されるようになった．脳腫瘍，特にグリオーマの領域においても，従来見逃されがちだった小病変が（早期）微小グリオーマとして注目されつつある．今回，われわれはCTL描出不明瞭で，MRIでも脳梗塞との鑑別困難であった左運動領野近傍の小病変に対し，MRI誘導定位脳手術装概を用い，生検により組織診断後，密封小線源療法（brachytherapy）を行った微小グリオーマを経験し，良好な結果を得たので，その有用性について若トの文献的考察を加えて報告する．

A 34 year old male suffered from convulsion on his right side with loss of consciousness. Neither plain nor enhanced CT could clearly demonstrate a lesion. Howev-er, a Gd-DTPA enhanced Ti weighted image (T₁WI) de-monstrated an enhancing lesion (2cm in diameter) in the left frontal lobe including the motor cortex. This lesion was not identified on plain T1WI. A T₂, weighted image (T₂WI) showed a high intensity lesion without mass effect slightly larger than the enhanced area on "HIW.This lesion was suspected to be a glial microtumor, but, because it was difficult to differentiate it from a cerebral infarction, it was confirmed to be a neoplasm by means of an MRI guided stereotactic biopsy. The histological dia-gnosis of the frozen section was a grade 2 astrocytoma.

Subsequently brachytherapy with seeds was per-formed, and about 80Gy of interstitial irradiation was given to the edge of the enhanced area on MRI. The minimum dose in the high intensity area on T2WI was about 50Gy. The patient was discharged with no neuro-logical deficits. The Gd-DTPA enhanced lesion decreased in size six months after the treatment.

MRI guided stereotactic system makes it possible to target a high intensity lesion on T,WI in brachytherapy. Brachytherapy using this system is considered to be use-ful in the treatment of glial microtumor in an area in which it is difficult to identify it on CT.