Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

Abstract

Background:The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipidpoor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand.Purpose: To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods:Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] 3 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test.Results: A total of 220 patients (mean age 6 standard deviation, 66 years 6 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of 210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of 21 HU), contrast-enhanced attenuation (3% [

Development and Validation of a Clinical-Image Model for Quantitatively Distinguishing Uncertain Lipid-Poor Adrenal Adenomas From Nonadenomas

“…Although adenomas have been reported to show rapid wash in the portal vein phase ( 13 , 27 ), they often showed no statistically significant difference in univariate analysis. A recent study ( 12 ) indicated that the ratio of portal venous phase attenuation to unenhanced attenuation allowed sufficient identification of lipid-poor adenomas and nonadenomas. Therefore, we attempted to incorporate the portal vein phase attenuation into the combined model, which was an independent risk factor in multivariate analysis.…”

“…Nevertheless, the delayed phase and additional radiation exposure may limit the utility of the washout CT protocol ( 12 ). However, the relative percentage wash-in ratio of adrenal lesions from the unenhanced to the portal venous phase can remedy the above defects ( 12 , 13 ). To our knowledge, only a few studies including a large number of lipid-rich adenomas have simultaneously assessed unenhanced attenuation and contrast wash-in features on CT ( 12 , 14 ).…”

“…However, the relative percentage wash-in ratio of adrenal lesions from the unenhanced to the portal venous phase can remedy the above defects ( 12 , 13 ). To our knowledge, only a few studies including a large number of lipid-rich adenomas have simultaneously assessed unenhanced attenuation and contrast wash-in features on CT ( 12 , 14 ). There is currently no combined model established on easily available demographic information and CT characteristics for distinguishing lipid-poor adenomas and nonadenomas.…”

“…Thus, lipid-poor adrenal lesions usually need a dedicated adrenal washout CT protocol for further characterization (8)(9)(10)(11). Nevertheless, the delayed phase and additional radiation exposure may limit the utility of the washout CT protocol (12). However, the relative percentage wash-in ratio of adrenal lesions from the unenhanced to the portal venous phase can remedy the above defects (12,13).…”

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

“…The detection rate of adrenal incidentalomas gradually increases with the application of cross-sectional imaging, accounting for approximately 4-10% of all abdominal computed tomography (CT) examinations (1)(2)(3)(4). Adrenal incidentalomas include solid tumors, such as adrenal adenoma, adrenal pheochromocytoma, adrenocortical carcinoma, and adrenal metastasis, of which adrenal adenoma accounts for 70-80% (4,5).…”