Diffusion weighted MR imaging of ring enhancing brain lesions.

OBJECTIVE To evaluate the role of diffusion weighted imaging in differentiating the cause of ring enhancing brain lesions. STUDY DESIGN Analytical, descriptive study. PLACE AND DURATION OF STUDY Department of Radiology, The Aga Khan University Hospital, Karachi, from March 2007 to July 2011. METHODOLOGY Diffusion weighted imaging (DWI) was performed on 37 patients having ring enhancing lesions on their post-contrast brain MRI scans. These lesions were characterized into neoplastic and abscess cavity on the basis of diffusion restriction. Correlation of all these findings was done with histopathology obtained in all these patients. Sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of DWI were calculated. Comparisons of mean ADC values of abscess and neoplastic lesions were also done using t-test. RESULTS DWI had a sensitivity of 94.73%, specificity of 94.44%, positive predictive value of 94.73%, and negative predictive value of 94.44% and diagnostic accuracy of 94.5% in differentiating brain abscess from neoplastic brain lesions. Mean ADC value in central cavity and wall of neoplastic lesions and brain abscesses were calculated with significant p-value of 0.001 and 0.025 respectively. CONCLUSION Diffusion weighted imaging is non-invasive method with high sensitivity and specificity which can help in differentiation of ring enhancing neoplastic lesions and brain abscesses. This modality should be read in conjunction with conventional imaging.