OBJECTIVETo evaluate application value of apparent diffusion coefficient (ADC) in differentiating brain radiation-injuries and glioma recurrence.

METHODSTotally 23 patients [18 men and 5 women aged 32 to 67 years (mean: 47 years)] with previously resected and irradiated glioma were examined by using a 3.0T MR Scanner, including conventional and diffusion weighted image (DWI) sequences. All the cases were proved by pathology or clinical follow-up. Postprocessing of ADC maps was performed by using Functool software (AW 4.3, GE Healthcare), and the regions of interest (ROIs) were manually drawn on ADC maps in the area corresponding to the contrast-enhancing area on post-contrast axial T1-weighted images, avoiding the hemorrhage or necrosis. The ADC values were calculated automatically. ADC values were measured 10 times in order to reduce errors, and mean ADC value, maximum ADC value, and minimum ADC value were acquired.

RESULTSBoth recurrent glioma and irradiated necrosis tended to have hemorrhage, necrosis, and edema. The mean ADC value and maximum ADC value were lower in the recurrent tumor group than in the radiation-injuries group, but no statistical difference was achieved. However, the minimum ADC value was significantly lower in the recurrent tumor group than in the radiation-injuries group (P=0.016).

CONCLUSIONThe minimum ADC value can be used as an useful tool in differentiating tumor recurrence from radiation-injuries.