Histogram Analysis of Apparent Diffusion Coefficient Maps for Differentiating Primary CNS Lymphomas From Tumefactive Demyelinating Lesions

OBJECTIVE. This study intended to investigate the usefulness of histogram analysis of apparent diffusion coefficient (ADC) maps for discriminating primary CNS lymphomas (PCNSLs), especially atypical PCNSLs, from tumefactive demyelinating lesions (TDLs). MATERIALS AND METHODS. Forty-seven patients with PCNSLs and 18 with TDLs were enrolled in our study. Hyperintense lesions seen on T2-weighted images were defined as ROIs after ADC maps were registered to the corresponding T2-weighted image. ADC histograms were calculated from the ROIs containing the entire lesion on every section and on a voxel-by-voxel basis. The ADC histogram parameters were compared among all PCNSLs and TDLs as well as between the subgroup of atypical PCNSLs and TDLs. ROC curves were constructed to evaluate the diagnostic performance of the histogram parameters and to determine the optimum thresholds. RESULTS. The differences between the PCNSLs and TDLs were found in the minimum ADC values (ADC(min)) and in the 5th and 10th percentiles (ADC 5% and ADC 10%) of the cumulative ADC histograms. However, no statistical significance was found in the mean ADC value or in the ADC value concerning the mode, kurtosis, and skewness. The ADC(min), ADC 5%, and ADC 10% were also lower in atypical PCNSLs than in TDLs. ADC(min) was the best indicator for discriminating atypical PCNSLs from TDLs, with a threshold of 556 x 10-6 mm(2)/s (sensitivity, 81.3 %; specificity, 88.9%). CONCLUSION. Histogram analysis of ADC maps may help to discriminate PCNSLs from TDLs and may be particularly useful in differentiating atypical PCNSLs from TDLs.