[A case of glial microtumor treated with brachytherapy using MRI guided stereotactic system]

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. However, a Gd-DTPA enhanced T1 weighted image (T1WI) demonstrated an enhancing lesion (2 cm 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 T1WI. 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 diagnosis of the frozen section was a grade 2 astrocytoma. Subsequently brachytherapy with 192Ir seeds was performed, 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 neurological 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 T2WI in brachytherapy. Brachytherapy using this system is considered to be useful in the treatment of glial microtumor in an area in which it is difficult to identify it on CT.