MAGNETIC-RESONANCE SPECTROSCOPY GUIDED BRAIN-TUMOR RESECTION - DIFFERENTIATION BETWEEN RECURRENT GLIOMA AND RADIATION CHANGE IN 2 DIAGNOSTICALLY DIFFICULT CASES

Background: It is often difficult to differentiate a recurrent glioma from the effects of post-operative radiotherapy by means of convention al neurodiagnostic imaging, Proton magnetic resonance spectroscopic im aging (H-1-MRSI), that allows in vivo measurements of the concentratio n of brain metabolites such as choline-containing phospholipids (Cho), may provide in vivo biochemical information helpful in distinguishing areas of tumor recurrence from areas of radiation effect. Patients an d Methods: Two patients who had undergone resection and post-operative radiotherapy fbr a cerebral glioma became newly symptomatic. Computed tomographic (CT) and magnetic resonance imaging (MRI) performer: afte r the Intravenous infusion of contrast material, and in one case, [18F ]fluorodeoxyglucose positron emission tomography (PET), could not diff erentiate between the possibilities of recurrent glioma and radiation effect. The patients underwent H-1-MRSI prior to reoperation and the H -1-MRSI results were compared to histological findings originating fro m the same locations. Results: A high Cho signal measured by H-1-MRSI was seen in areas of histologically-proven dense tumor recurrence, whi le low Cho signal was present where radiation changes predominated. Co nclusions: The differentiation between the recurrence of a cerebral gl ioma and the effects of post-operative irradiation was achieved using H-1-MRSI in these two patients whose conventional neurodiagnostic imag ing was equivocal for such a distinction. Where these two conditions a re present, metabolite images from H-1-MRSI, such as that based on Cho , can be co-registered with other imaging modalities such as MRI and m ay also be integrated with functional MRI or functional PET within a m ultimodal imaging-guided surgical navigation system to assure maximal resection of recurrent tumor while minimizing the risk of added neurol ogical damage.