ADC histogram analysis for adrenal tumor histogram analysis of apparent diffusion coefficient in differentiating adrenal adenoma from pheochromocytoma

PurposeTo determine the diagnostic performance of apparent diffusion coefficient (ADC) histogram analysis in diffusion-weighted (DW) magnetic resonance imaging (MRI) for differentiating adrenal adenoma from pheochromocytoma. Materials and MethodsWe retrospectively evaluated 52 adrenal tumors (39 adenomas and 13 pheochromocytomas) in 47 patients (21 men, 26 women; mean age, 59.3 years; range, 16-86 years) who underwent DW 3.0T MRI. Histogram parameters of ADC (b-values of 0 and 200 [ADC(200)], 0 and 400 [ADC(400)], and 0 and 800 s/mm(2) [ADC(800)])mean, variance, coefficient of variation (CV), kurtosis, skewness, and entropywere compared between adrenal adenomas and pheochromocytomas, using the Mann-Whitney U-test. Receiver operating characteristic (ROC) curves for the histogram parameters were generated to differentiate adrenal adenomas from pheochromocytomas. Sensitivity and specificity were calculated by using a threshold criterion that would maximize the average of sensitivity and specificity. ResultsVariance and CV of ADC(800) were significantly higher in pheochromocytomas than in adrenal adenomas (P<0.001 and P=0.001, respectively). With all b-value combinations, the entropy of ADC was significantly higher in pheochromocytomas than in adrenal adenomas (all P0.001), and showed the highest area under the ROC curve among the ADC histogram parameters for diagnosing adrenal adenomas (ADC(200), 0.82; ADC(400), 0.87; and ADC(800), 0.92), with sensitivity of 84.6% and specificity of 84.6% (cutoff, 2.82) with ADC(200); sensitivity of 89.7% and specificity of 84.6% (cutoff, 2.77) with ADC(400); and sensitivity of 94.9% and specificity of 92.3% (cutoff, 2.67) with ADC(800). ConclusionADC histogram analysis of DW MRI can help differentiate adrenal adenoma from pheochromocytoma. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:1195-1203