Diffusion-weighted imaging and the apparent diffusion coefficient on 3T MR imaging in the differentiation of craniopharyngiomas and germ cell tumors

The apparent diffusion coefficient (ADC) on diffusion-weighted imaging (DWI) plays an important role in diagnosing intracranial tumors and predicting the histopathological grade of the tumor. However, the differences in the ADC values between craniopharyngiomas and germ cell tumors (GCTs) have not been clarified. We therefore evaluated the DWI and ADC values at b = 1000 and b = 4000 s/mm(2) on 3T magnetic resonance (MR) imaging and assessed the possibility of differentiating between craniopharyngiomas and GCTs. We retrospectively reviewed 19 patients with craniopharyngioma and 24 patients with GCT who underwent surgery and received a histopathological diagnosis. Thirty-four patients underwent DWI with b = 1000 and b = 4000 s/mm(2) and nine patients underwent periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) DWI with b = 1000 s/mm(2). The ADC was determined by manually placing regions of interests (ROIs) in the respective tumor regions on the ADC maps and is expressed as the minimum (ADC(MIN)), mean (ADC(MEAN)), and maximum (ADC(MAX)) absolute values. The craniopharyngiomas showed lower intensity on DWI at b = 1000 and b = 4000 s/mm(2) than the GCTs. Furthermore, the craniopharyngiomas demonstrated significantly high ADC values (ADC(MIN), ADC(MEAN), and ADC(MAX)) in comparison with the GCTs on DWI at b = 1000 and b = 4000 s/mm(2). The logistic discriminant analysis clarified the advantage of ADC(MIN) at b = 4000 s/mm(2) in differentiating between craniopharyngiomas and GCTs compared with the other ADC values. DWI and the ADC values may help clinicians to differentiate between craniopharyngiomas and GCTs. The ADC(MIN) at b = 4000 s/mm(2) is particularly useful for differentiation.