The value of 15-minute delayed contrast-enhanced CT to differentiate hyperattenuating adrenal masses compared with chemical shift MR imaging.

Objectives: To investigate the diagnostic performance of 15-min delayed contrast-enhanced computed tomography (15-DECT) compared with that of chemical shift magnetic resonance (CSMR) imaging in differentiating hyperattenuating adrenal masses and to perform subgroup analysis in underlying malignancy and non-malignancy.

Methods: This study included 478 adrenal masses in 453 patients examined with 15-DECT and 235 masses in 217 patients examined with CSMR. Relative percentage washout (RPW) and absolute percentage washout (APW) on 15-DECT, and signal intensity index (SII) and adrenal-to-spleen ratio (ASR) on CSMR were measured. Sensitivity, specificity and accuracy of 15-DECT and CSMR were analysed for characterisation of adrenal adenoma. Subgroup analyses were performed in patients with and without underlying malignancy. Attenuation and size of the masses on unenhanced CT correlated with the risk of non-adenoma.

Results: RPW calculated from 15-DECT showed the highest diagnostic performance for characterising hyperattenuating adrenal masses regardless of underlying malignancy, and the sensitivity, specificity and accuracy were 91.7 %, 74.8 % and 88.1 %, respectively in all patients. The risk of non-adenoma increased approximately threefold as mass size increased 1 cm or as its attenuation value increased by 10 Hounsfield units.

Conclusions: 15-DECT was more accurate than CSMR in characterising hyperattenuating adrenal masses regardless of underlying malignancy.

Key Points: Delayed contrast-enhanced CT and chemical shift magnetic resonance (CSMR) characterise adrenal lesions. 15-min DECT is more accurate than CSMR in characterising hyperattenuating adrenal masses. Sensitivity of CSMR decreases as the CT attenuation of adenomas increases. Risk of non-adenoma is increased 2.9-fold as size increased by 1 cm. Risk of non-adenoma is increased 2.9-fold as attenuation increased by 10 HU.