Image-guided surgery for gliomas

Standard therapy for gliomas consists of maximum tumor resection and conventional external radiotherapy with/without nitrosourea-based chemotherapy. Recent advances in neuroimaging and intra-operative monitoring techniques enable us to maximize tumor resection with minimum post-operative morbidity even when the tumors locate near the eloquent brain regions. In our institutions, fusion images of MRI and methionine uptake determined by positron emission tomography are prepared pre-operatively. Functional brain regions are mapped using functional MRI, tractography, and occasionally, subdural grid electrode placement. Then, the area of methionine uptake is removed as much as possible using a neuronavigation system and intra-operative functional monitoring with cortical and subcortical stimulations. Awake craniotomy is sometimes used. Intra-operative correction for brain shift during surgery due to brain retraction and cerebrospinal fluid leakage is an important issue. Intra-operative CT and MRI are useful to update informations for neuronavigation but they cost a lot. We have been testing the possibility of more precise and less expensive brain shift correction by combining optical imaging of brain surfaces and ultrasound information of deep structures during surgery.