Role of magnetic resonance spectroscopy in grading of primary brain tumors

To assess the usefulness of MR spectroscopy [MRS] in grading of primary brain tumors. MRS was performed in a 22 patients with primary brain tumors. Metabolite ratios of Choline [Cho] / N-acetyle Laspartate [NAA]. Cho/ Creatine [Cr], Cho+Cr/NAA as well as lipids and lactate [LL]/Cr were calculated at short and intermediate echo time [TE]. Additionally, myoinositol [ml]/Cr was calculated at short TE. Tumors were subdivided into low grades and high grade on the basis of histopathology Receiver operating characteristic analysis of metabolite ratios was performed to find the cut off values between high and low grade tumors. The resulting sensitivity, specificity and accuracy were calculated. At intermediate TE, Cho/NAA, Cho+Cr/NAA and Cho/Cr were significantly higher in high grade tumors than in low grade ones. At short TE, Cho/Cr and LL/Cr ratios were significantly higher in high grade tumors than in low grade ones. The diagnostic accuracy of metabolite ratios at intermediate TE was 86% whereas at short TE, the diagnostic accuracy was 75%. Combination of both TEs revealed a diagnostic accuracy of 88%. Cho/NAA, Cho+Cr/Cr/NAA and Cho/Cr are reliable in determining the tumor grade. LL/Cr is highly related to high grade tumors. Combination of both short and intermediate TEs provides better accuracy, in grading of brain neoplasm, compared to that when using each TE separately