Purpose: To determine the utility of diffusion-weighted MR imaging (DWI) for the diagnosis of adrenal tumors.
Materials and methods: Forty-two patients (24 men and 18 women; age, 61.5 +/- 12.7 years old; range, 34-86 years) with 43 adrenal tumors (11 functioning cortical adenomas, 20 nonfunctioning cortical adenomas, 7 metastatic tumors, and 5 pheochromocytomas) were retrospectively investigated. DWIs were obtained by single-shot spin-echo type echo-planar imaging sequence (1.5 Tesla [T]; TR = 8000 ms, TE = 72, b-factor = 0 and 1000 s/mm(2)), and apparent diffusion coefficient (ADC) value was calculated. Chemical shift images were obtained by gradient echo sequence (TR = 161, TE = 2.38 [out-of-phase, OP] and 4.76 [in-phase, IP], FA = 60), and the signal intensity index (SII; [IP-OP]/IP *100%) was calculated.
Results: There was no difference in ADC values between adenomas (1.09 +/- 0.29*10(-3) mm(2)/s; range, 0.52-1.64) and metastatic tumors (0.85 +/- 0.26*10(-3); 0.51-1.23; p = 0.14). Pheochromocytomas showed the higher mean ADC value (1.59 +/- 0.34*10(-3); 1.04-1.96) compared with those of adenomas or metastatic tumors (P < 0.05 and P < 0.005, respectively). The mean SII of adenomas (62.1 +/- 17.9%; 14.5-88.4) was significantly higher than those of pheochromocytomas (4.0 +/- 10.0%; -19.6-3.3; P < 0.005) or metastatic tumors (-1.5 +/- 11.7%; -18.3-8.2; P < 0.01). There was no correlation between ADC values and SII.
Conclusion: Although pheochromocytomas showed higher ADC values, we did not find that ADC value had diagnostic utility for differentiating adenomas and metastatic tumors.