Development of an MR Spectroscopic Index to Differentiate Tumor from Treatment Induced Gliosis

Radhika Srinivasan¹, Jan Wooten¹, Jason C. Crane¹, Soonmee Cha¹, Suzanne Chang¹, Scott Vandenberg¹, John Kurhanewicz¹, Sarah J. Nelson¹

The goal of this study was to identify MR spectroscopic (MRS) markers that are likely to be able to differentiate active tumor from treatment induced gliosis. This is an important problem because while tumor regions should be included in follow-up treatment plans, regions represented by gliosis should be left untouched since these areas represent areas of normal brain that are influenced by treatment. Typically high choline levels are used to indicate tumor presence. The challenge in differentiating tumor from gliosis using this metric is that both of them could result in elevated levels of choline. To evaluate strategies to resolve this ambiguity we first determine the characteristic MR Spectroscopic markers that differentiate tumors from gliosis using High Resolution Magic Angle Spectroscopy (HR-MAS) of samples that are confirmed to belong to either tumor or gliosis using histopathology. The specific markers derived from this study are evaluated by ex-vivo HR-MAS of biopsies from within tumor regions in patients with newly diagnosed GBM. Finally these markers are evaluated against known MR markers of tumor presence from in-vivo 3T MR data. Following these studies the development of a suitable MRS index that has the potential to differentiate tumor from gliosis will be presented.