Meningiomas Assessed with In Vivo 3D 1H-Magnetic Resonance Spectroscopy Integrated Into a Standard Neurosurgical Image Guidance System: Determining Biochemical Markers of Clinically Aggressive Behavior and Providing a Resection Advantage

Abstract

15 usable patients with recurrent or newly diagnosed meningiomas using a 3T GE Signa scanner. Quantified spectral metabolite peaks were used to select voxels that had high or low alanine for tissue sampling. 3D 1H-MRSI was integrated into a standard image guided surgery (IGS) system; a mask of the voxel was loaded onto the IGS system allowing surgeons to precisely extract tissue intraoperatively according to biochemical mapping. Ex vivo NMR and conventional histological grading were performed on the extracted tissue. Results: Tumor spectra showed biochemically heterogeneous regions, especially for choline, lactate and alanine. Mean alanine concentrations were lower in more aggressive--histologically and immunohistochemically--regions of the meningiomas in the study. In addition, lower grade meningiomas showed high alanine at the tumor periphery with decreased central alanine. Ex vivo NMR was well-correlated with in vivo 3D 1H-MRSI. Conclusions: Non-invasive detection of various intratumoral biochemical markers using 3D 1H-MRSI can distinguish areas within meningiomas that express more aggressive features. There is regional heterogeneity in the concentrations of these markers within individual tumors. Furthermore, 3D 1H-MRSI may be able to exploit these regional differences to separate more aggressive from less aggressive areas within a given meningioma. Such knowledge may be useful to 5 the neurosurgeon faced with the task of meningioma resection, and in the planning adjuvant therapy for residual meningioma