In vivo single-voxel proton MR spectroscopy in brain lesions with ring-like enhancement

It is often difficult to make a correct diagnosis of ring-like enhanced les ions on Gd-enhanced MR brain images. To differentiate these lesions using p roton MR spectroscopy (H-1-MRS), we retrospectively evaluated the correlati on between the H-1-MR spectra and histopathological findings. We evaluated proton MR spectra obtained from the lesions in 45 patients, including metas tasis (n = 19), glioblastoma (n = 10), radiation necrosis (n = 7), brain ab scess (n = 5), and cerebral infarction (n = 4). The rate of misdiagnosis wa s found to be lowest at the threshold level of 2.48 for the (choline contai ning compounds)/(creatine and phosphocreatine) ratio (Cho/Cr) obtained from the whole lesions, which include the enhanced rim and the non-enhanced inn er region. That is, the positively predictive values of a Cho/Cr greater th an 2.48 for diagnosing metastasis or glioblastoma was 88.9 and 60.0%, respe ctively, and the positively predictive value of a Cho/Cr less than 2.48 for diagnosing radiation necrosis or cerebral infarction was 71.4 and 100%, re spectively. For further differentiating between metastasis and glioblastoma , information about the presence and absence of an N-acetyl-aspartate (NAA) peak and lipid- or lactate-dominant peak was found to be useful. In 73.7% of metastasis cases a lipid-dominant peak was observed in the whole lesion without an NAA peak in the inner region, whereas the same pattern was obser ved in only 10% of the glioblastoma cases. Correlation with the histopathological findings showed that a high Cho sign al is suggestive of neoplasm. Lipid signal in the non-enhanced central regi on was correlated to necrosis. Lactate signals were often observed in gliob lastoma, abscess and sometimes metastasis, presumably reflecting the anaero bic glycolysis by the living cells in the ring-like enhanced rim. Single-vo xel proton MR spectroscopy may serve as a potential tool to provide useful information of differentiation of ring-like enhanced lesions that cannot be diagnosed correctly using enhanced MR images alone. Copyright (C) 2001 Joh n Wiley & Sons, Ltd.