SURG-31. SPECTROSCOPIC MRI TO GUIDE BIOPSY OF LOWER GRADE GLIOMAS

摘要

Primary brain tumors are serious and life-threatening; thus, accurate histopathologic diagnosis is critical for determining the proper clinical treatment regimen. Grade II/III gliomas (lower grade gliomas, or LGGs), including astrocytomas and oligodendrogliomas, are heterogeneous and potentially contain low- and high-grade areas within the same tumor. Therefore, it is critical to target biopsies to the most aggressive portion of the tumor to avoid tumor under-grading and under-treatment. While glioblastomas are typically targeted based on contrast-enhanced MRI, LGGs have little contrast enhancement to define targets for biopsy treatment guidance. Spectroscopic MRI (sMRI) is a high-resolution MRI imaging method which allows for detection of metabolic abnormalities such as choline and NAA in the entire brain without injection of a contrast agent. We have previously evaluated the relationship between sMRI Cho/NAA ratios and tumor infiltration in surgical specimens from high grade gliomas, demonstrating a strong correlation between sMRI results and glioma infiltration. We also used the location information to correlate sMRI data to genetic and histologic biomarkers (such as 1p19q, IDH, and MGMT). An IRB-approved pilot study to obtain sMRI prior to stereotactic biopsy has been done in 20 non-enhancing LGG cases. Patients with a suspected LGG diagnosis underwent sMRI at the time of their surgical planning MRI. sMRI images were then registered to the T1w-CE and T2/FLAIR images and imported into the Stealth neuronavigation system for biopsy planning. We found that all astrocytomas (regardless of grades) showed strongly elevated Cho/NAA, while the LGGs were hardly delineated on T1w and T2/FLAIR. We found that pathology-confirmed grade II oligodendroglioma do not have choline elevation; however, NAA was mildly decreased, myo-inositol was elevated, and creatine (Cr) was mildly elevated. sMRI is a useful tool to improve biopsy targeting in LGG patients by ensuring that the highest risk regions are sampled.