Accessory spleen versus lymph node: Value of iodine quantification with dual-energy computed tomography

ObjectivesTo evaluate whether iodine quantification with Dual-Energy Computed Tomography (DECT) improves the differentiation of accessory spleens (AS) from lymph nodes (LN) compared to CT number measurements.MethodsAbdominal DECT images of 75 patients with either AS (n = 35) or LN (n = 48) (benign entity) were retrospectively evaluated. Hounsfield Units (HU) and iodine concentrations of AS, LN and the main spleen were measured. Receiver operating characteristics (ROC) were performed to calculate an optimal threshold for distinguishing AS from LN. Sensitivity, specificity, and accuracy were calculated for distinguishing AS from LN by iodine concentration measurements.ResultsMean CT numbers and iodine concentrations were higher for AS (148 ± 29 HU and 48.2 ± 11 × 100 μg/cc) than LN (83 ± 19 HU and 31.5 ± 6.2 × 100 μg/cc, respectively, P < 0.001 each). Mean CT numbers were lower for AS compared to the main spleen (161 ± 29HU, P < 0.01), whereas mean iodine concentrations (47.7 ± 10 × 100 μg/cc) were not significantly different (P = 0.095). An iodine concentration greater than 38 × 100 μg/cc suggested AS with a sensitivity, specificity and accuracy of 91%, 85%, and 88%, respectively (Area under ROC curve 0.941).ConclusionsIodine measurements might contribute to the differentiation of AS from LN. Iodine concentrations similar to that of the main spleen may help to confirm the diagnosis of AS.