Whole-lesion CT histogram analysis as an advanced technique in the portal venous phase: differentiating lipid poor adrenal adenomas from pheochromocytomas.

Purpose: Adrenal computed tomography (CT) has limitation due to imaging overlaps inthe washout characteristics of pheochromocytomas and adenomas (especially lipid-poor). The aim of this study was to investigate the distinguishability of lipid-poor adrenal adenomas and pheochromocytomas using whole-lesion CT histogram analysis.

Materials and methods: Histopathologically proven 24 lipid-poor adenomas and 29 pheochromocytomas (total 53 lesions in 53 patients) were included in this retrospective study. Data obtained from standard and volumetric examinations of the lesions by dedicated adrenal CT were compared between the two groups using univariate analysis. Parameters that showed differences were further evaluated using multivariate logistic regression analysis.

Results: Univariate analysis revealed significant differences between the two groups in terms of lesion size, lesion volume, percentage of relative wash out, peak HU values and the percentage of voxels with attenuation ≥ 100 HU, ≥ 110 HU and ≥ 120 HU (p = 0.0001, P = 0.0001, P = 0.01, P = 0.008, p = 0.04, p = 0.02, p = 0.02, respectively). Multivariate analysis revealed lesion size ≥ 22.05 mm (OR: 22; p < 0.0001), the percentage of voxels with attenuation ≥ 120 HU being ≥ 9% (OR: 3.27; p = 0.04), peak HU value ≥ 161.5 HU (OR: 4.40; p = 0.01) as risk factors for pheochromocytomas.

Conclusions: Whole lesion CT histogram analysis can be used to differentiate pheochromocytomas from lipid-poor adenomas. Lesion volume, the percentage of voxels with attenuation ≥ 120 HU and peak HU values are independent parameters that can assist in this differentiation. These findings may help avoid unnecessary biopsies and surgeries for lipid-poor adenomas, while identifying pheochromocytoma risk may improve perioperative patient management. Our results should be validated by future prospective studies.