Proton MR spectroscopy of cerebral gliomas at 3 T: spatial heterogeneity, and tumour grade and extent

This study aimed to evaluate the usefulness of proton MR spectroscopic imaging (1H-MRSI) at 3 T in differentiating high- from low-grade gliomas, and tumour from necrosis, oedema or normal tissue. Forty-four patients with brain gliomas and four with meningiomas were retrospectively reviewed. The normalised metabolites choline (nCho), N-acetylaspartate (nNAA), creatine (nCr) and lactate/lipids (nLL), and the metabolite ratios Cho/NAA, NAA/Cr and Cho/Cr were calculated. Necrotic-appearing areas showed two spectroscopic patterns: ''necrosis'' with variable nCho and high nLL, and ''cystic necrosis'' with variable nLL or nonevident peaks. Peri-enhancing oedematous-appearing areas showed three spectroscopic patterns (''tumour'' with abnormal Cho/NAA, ''oedema'' with normal Cho/NAA and ''tumour/oedema'' with normal nCho and abnormal Cho/NAA) in gliomas, and one (''oedema'') in meningiomas. Peri-enhancing or peri-tumour normal-appearing areas showed two patterns (''infiltrated'' with abnormal nCho and/or Cho/NAA and ''normal'' with normal spectra) in gliomas and one (''normal'') in meningiomas. Discriminant analysis showed that classification accuracy between high- and low-grade glioma masses was better with normalised metabolites or all parameters together than metabolite ratios and that among peri-enhancing areas was much better with normalised metabolites. The analysis of spatial distribution of normalised metabolites by 3-T 1H-MRSI helps to discriminate among different tissues, offering information not available with conventional MRI. (orig.)