Differential diagnostic value of plain CT scan in adrenal adenoma and non-adenoma: A two-center control study of mean attenuation value, minimum attenuation value, and CT histogram

OBJECTIVES: To investigate the value of mean attenuation value (AV(mean)), minimum attenuation value (AV(min)), and CT histogram (CTH) for the differential diagnosis of adrenal adenoma and non-adenoma in two medical centers. METHODS: The plain CT data of 403 cases of adrenal adenoma and 141 cases of non-adenoma in center A were retrospectively analyzed, and compared with data of 86 cases of adenoma and 71 cases of non-adenoma in center B. All cases were confirmed by pathology or clinical follow-up. The diagnostic efficacy of AV(mean) ≤ 10 Hounsfield units (HU), AV(min) ≤ 0 HU, and CTH negative pixels ≥ 10% for adrenal adenoma, and AV(min) and CTH for adenoma with AV(mean) > 10Hu were compared between the two medical centers. RESULTS: In medical centers A and B, the AUC of AV(mean) for the differential diagnosis of adenoma and non-adenoma was 0.956 and 0.956, respectively, and the corresponding sensitivity, specificity, and accuracy were, 0.591 and 0.663, 1.000 and 1.000, 0.697, and 0.815, respectively, when the threshold was ≤ 10 HU. The AUC of AV(min) was 0.941 and 0.958, respectively, and the corresponding sensitivity, specificity, and accuracy were 0.869 and 0.826, 0.986, and 0.972, 0.899, and 0.892, respectively, when the threshold was ≤ 0 HU. The AUC of CTH negative pixels was 0.948 and 0.952, respectively, and the corresponding sensitivity, specificity, and accuracy were 0.759 and 0.674, 1.000 and 1.000, 0.822, and 0.822, respectively, when the threshold was ≥ 10%. Among adenoma with AV(mean) >10 HU, the best threshold of AV(min) in center A and center B were -0.250HU and 2.375HU, and the corresponding AUC, sensitivity and specificity were 0.858 and 0.846, 0.691 and 0.586, 0.986 and 0.958; the best threshold of CTH in center A and center B were 0.895% and 0.775%, and the corresponding AUC, sensitivity and specificity were 0.873 and 0.822, 0.818 and 0.724, 0.837 and 0.915. CONCLUSION: AV(mean), AV(min), and CTH are all important parameters for differentiating adrenal adenoma from non-adenoma. Even for adenomas with AV(mean) > 10 HU, AV(min) and CTH still had high diagnostic efficiency. The three parameters are complementary, assisting clinicians to develop personalized treatments.