Magnetic resonance spectroscopy in focal brain lesions.

Objective: To describe the spectrum of Magnetic Resonance spectroscopy in focal brain lesions and determine its diagnostic accuracy using histopathology as gold standard in differentiating neoplastic and non-neoplastic focal brain lesions.

Methods: The study was conducted in Department of Radiology, Aga Khan University Hospital, Karachi from Dec 2006 till Jan 2009. Fifty three patients found to have focal brain lesions on magnetic resonance imaging (MRI) were included in the study. Magnetic Resonance spectroscopy (MRS) was performed in these focal lesions. These lesions were deemed neoplastic and non-neoplastic on MR Spectrum findings. Correlation of all these findings was done with histopathology obtained in all these patients. Sensitivity, specificity, positive, negative predictive values and diagnostic accuracy of MR Spectroscopy was calculated. Percentage agreement between spectroscopy and histopathology was also calculated using kappa statistics.

Results: Increase Choline/creatine and Choline/NAA ratio noted in neoplastic lesions compared to nonneoplastic lesion with significant p-value. MR Spectroscopy has a sensitivity of 93.02%, specificity of 70%, positive predictive value of 93.02%, negative predictive value of 70% and diagnostic accuracy of 88.67% in differentiating neoplastic and non-neoplastic brain lesions. Kappa statistics shows a good agreement between MR Spectroscopy and histopathology (k = 0.630).

Conclusion: Magnetic Resonance spectroscopy (MRS) is non-invasive sensitive, however, relatively nonspecific modality in differentiating neoplastic and non-neoplastic brain lesions. This modality should be considered as an adjunct to conventional imaging rather than replacement for histopathological evaluation.