Apparent T2 relaxation times of lipid and macromolecules: A study of high-grade tumor spectra

Abstract

Purpose: To determine T2 relaxation times of lipid and macromolecules (Lip/MMs) observed by 1H magnetic resonance spectroscopy (1H MRS) of metastases (MET) and glioblastomas (GBM), so that they may be better characterized. Materials and Methods: 1H spectra were acquired at multiple echo times from brain lesions using point-resolved spectroscopy sequence (PRESS) at TE = 30 msec either with metabolite-nulling (six GBM and 11 MET), or without metabolite-nulling (four MET and one mucocele). All lesions were previously untreated and had subsequent histopathological classification. Results: The T2 of the 1.3-ppm Lip/MM peak was concentration-dependent, but at high concentrations it was significantly different (P = 0.015) between GBM (42 ± 6 msec) and MET (63 ± 18 msec). The broad 2.05-ppm and 0.09-ppm Lip/MM peaks had similar T2s in MET and GBM. The T2 of the narrow 2.05-ppm Lip/MM peak sometimes observed had a T2 of 100 ± 17 msec in MET and 75 msec in the mucocele. Conclusion: We observed significantly higher T 2 of the 1.3-ppm Lip/MM peak in MET compared with GBM at high 1.3-ppm proton concentrations, in agreement with a higher 1.3/ 0.9-ppm peak ratio found in MET. The relatively long T2 of the 2.05-ppm Lip/MM peak sometimes observed in MET may cause it to be confused with N-acetyl aspartate (NAA). © 2007 Wiley-Liss, Inc.