Differentiate Adrenal Metastases From Adrenocortical Adenoma Using Dual Energy CT

Background and objectiveDifferentiating adenral adenomas from metastases was frenquently encontered in the daily work of radiologists, which was also important in the tumor staging, therapy and prognosis. Being differ from the conventional CT using density as the only parameter, dual energy CT(DECT) generated spectral imagings, which described the attenuation of the lesion on the basis of their energy-related attenuation characteristics, and would also provide the imformation about the neoplasm composition. DECT had been used in clinic works. The purpose of this study was to prospectively evaluate the ability of dual energy scanning in distinguishing adrenal metastases from adrenocortical adenoma on post-contrast CT images.Materials and methods40adrenal lesions (24adenomas,16metastases) in35patients (16men,19women, mean age52.2±12.7years) were enrolled in this study. On pre-contrast CT scan,10HU was used as standard to divide the adenomas into lipid-rich group (<10HU,14lessions) and lipid-poor group(>10HU,10lessions). The following conventional and spectral signs were ananlysed between the groups of lipid-rich adenomas and metastases, and lipid-poor adenomas and metastases respectively:(1) CT value on pre-and post-contrast imagings, patient’s age, tumor’s size, and the adjacent of the tumor, calcification and necrosis;②Iodine-contribution value(ICad), Water-contribution value(WCad), Fat-Iodine contribution value(FCad) on dual phases post-contrast imagings. Area under the receiver operating characteristic curve (ROC) was used to determine the threshold, and explore the best parameters of the differential diagnosis.ResultsThere was no statistically difference in the average size, age composition between thelipid-rich adenomas and metastases, lipid-poor adenomas and metastases. The CT value on pre-contrast scan of lipid-rich adenomas were statistically significant lower than that of metastasis, while there was no statistically difference between the lipid-poor adrenal adenomas and metastasis. Analysing spectral parameters on dual phases scan showed that the ICad, WCad and FCad of lipid-rich adenoma, lipid-poor adenoma were statistically significant lower than that of metastases (expected for the ICad of lipid-poor adenomas and metastases) respectively. Between spectral parameters on dual phases, the parameters on arterial phase was better than that on the portal venous phase. Comparing the spectral parameters on arterial phase, the WCad value has a higher sensitivity, while, the FCad value has a higher specificity.ConclusionDECT could improving the sensitivity and specificity in differentiating adrenal lipid-rich adenomas from metastasis and lipid-poor adenomas from metastasis on post-contrast imaging. The parameters of WCad and FCad has an important significance on increasing the sensitivity and specificity in differentiating lipid-poor adenomas from metastasis, and that was hard to differentiate on convintional pre-contrast and post-contrast imagings.