Role of Perfusion MRI and 1H Spectroscopy in the Evaluation of Brain Tumors- a Study in the Asian Subpopulation

Introduction: The role of MR Perfusion and 1H Spectroscopy in the evaluation of brain tumors has been extensively studied. We attempt to validate the same in the Asian sub population. Materials and Methods: 25 cases of primary and 2 secondary brain tumors were evaluated; 17 pretreatment and 11 post treatment. Routine pre and post contrast sequences, dynamic susceptibility weighted perfusion and CSI or SVS spectroscopy was performed Results: All viable tumors showed elevated rCBV, N-Cho, Cho/ Cr &Cho/ NAA and decreased N-NAA. Sensitivity of Cho/NAA was lower compared to the N-Cho. Peritumoral rCBV and altered spectra helped determine true tumor extent. Contrast T1WI allowed grading in only 60% cases of solid gliomas whereas with rCBV it was possible in all cases. rCBV increased progressively from grade II to IV. Grade IV gliomas had lower Cho level than grade IIIs and had elevated lipids. Rim enhancing necrotic tumors had high Cho, NAA, Cho /NAA & Cho/Cr, a lactate and a lipid peak. Metastasis showed characteristic perfusion mean curve (recovery phase) and no /absent NAA. Both viable tumor and post treatment changes showed post contrast enhancement however elevated rCBV, Cho, Cho/NAA, Cho/Cr was seen in viable tumor tissue where as low rCBV, NAA, Cho& Cr and elevated lipid- lactate was seen in post treatment necrosis. Conclusion: Perfusion MRI and spectroscopy allowed preoperative identification and grading of brain tumors, characterization as primary intraaxial or metastatic tumor as well as distinction of viable tumor tissue from post treatment changes.