Proton MR spectroscopy and preoperative diagnostic accuracy: An evaluationof intracranial mass lesions characterized by stereotactic biopsy findings

BACKGROUND AND PURPOSE: NW imaging; has made it easier to distinguish among the different types of intracranial mass lesions, Nevertheless, it is some times impossible to base a diagnosis solely on clinical and neuroradiologic findings, and, in these eases, biopsy must be performed. The purpose of th is study was to evaluate the hypothesis that proton MR spectroscopy is able to improve preoperative diagnostic accuracy in cases of intracranial tumor s and may therefore obviate stereotactic biopsy, METHODS: Twenty-six patients with intracranial tumors underwent MR imaging, proton MR spectroscopy, and stereotactic biopsy, MR spectroscopic findings were evaluated for the distribution pattern of pathologic spectra (NAA/Cho ratio <1) across the lesion and neighboring tissue, for signal ratios in d ifferent tumor types, and for their potential to improve preoperative diagn ostic accuracy. RESULTS: Gliomas and lymphomas showed pathologic spectra outside the area o f contrast enhancement while four nonastrocytic circumscribed tumors (menin gioma, pineocytoma, metastasis, and germinoma) showed mo pathologic spectra outside the region of enhancement. No significant correlation was found be tween different tumor types and signal ratios. MR spectroscopy improved dia gnostic accuracy by differentiating infiltrative from circumscribed tumors; however, diagnostic accuracy was not improved in terms of differentiating the types of infiltrative or circumscribed lesions. CONCLUSION: MR spectroscopy can improve diagnostic accuracy by differentiat ing circumscribed brain lesions from histologically infiltrating processes, which may be difficult or impossible solely on the basis of clinical or ne uroradiologic findings.