Apparent diffusion coefficients in oligodendroglial tumors characterized by genotype

PURPOSE: To investigate whether oligodendroglial tumors with or without 1p/19q loss differ in their diffusion-weighted imaging characteristics. Oligodendroglial tumors with or without 1p/19q loss differ in their therapeutic responsiveness and prognosis, and recent reports also suggest that these tumors may differ in their magnetic resonance characteristics and blood volume. MATERIALS AND METHODS: Apparent diffusion coefficients (ADCs) were assessed in three grade II oligodendrogliomas, nine grade II and five grade III oligoastrocytomas with known 1p/19q status. Regions of interest (ROIs) were placed on ADC maps: 1) around tumor margins to generate pixel histograms; 2) over minimum and maximum tumor ADC; 3) on areas comparable to the highest choline (Cho)/creatine (Cr) ratio determined from chemical shift imaging (CSI); and 4) across tumor margins to measure the ADC transition coefficient (ATC). RESULTS: Tumor ADC was significantly different from normal brain (P < 0.001). ADC in regions of highest Cho/Cr was greater than minimum ADC and did not correlate with the Cho/Cr ratio. ADC and ATC were not significantly different between oligodendroglial subtypes or grades. Tumors with intact 1p/19q had higher maximum (P = 0.021) and histogram ADC (P = 0.015), and greater ATC (P = 0.001) compared to those with 1p/19q loss, which may reflect differences in edema and cellularity. CONCLUSION: This preliminary study identified differences in ADC and ATC between oligodendroglial tumor genotypes that may reflect underlying biology. Confirmation in a larger series is warranted.