Differentiation of Adrenal Adenomas from Non-Adenomatous Lesions: Diagnostic Value of Unenhanced Spectral CT
by
, , , , , and
Tommasa Catania
1, 
Grazia Morabito
1,*,
Simone Barbera
1,
Massimo Venturini
2,
Federico Fontana
2,
Eduardo Maccarrone
1,
Grazia Maria Arillotta
1,
Velio Ascenti
3,
Silvio Mazziotti
1,
Thomas Joseph Vogl
4
,
Giovanni Foti
5,
Tommaso D’Angelo
1 and
Giorgio Ascenti
1 1
Diagnostic and Interventional Radiology Unit, BIOMORF Department, University Hospital “Policlinico G. Martino”, 98124 Messina, Italy
2
Diagnostic and Interventional Radiology Unit, Circolo Hospital, ASST dei Sette Laghi, University of Insubria, 21100 Varese, Italy
3
Department of Radiology, Policlinico Universitario, University of Milan, 20133 Milano, Italy
4
Department of Diagnostic and Interventional Radiology, University Hospital Frankfurt, 60590 Frankfurt am Main, Germany
5
Department of Radiology, IRCCS Sacred Heart Hospital Don Calabria, 37024 Negrar, Italy
*
Author to whom correspondence should be addressed.
Tomography 2026, 12(5), 68; https://doi.org/10.3390/tomography12050068
Submission received: 20 March 2026
/
Revised: 29 April 2026
/
Accepted: 7 May 2026
/
Published: 12 May 2026
Simple Summary
Accurate differentiation between adrenal adenomas and non-adenomatous lesions is essential for appropriate patient management, yet it remains challenging with conventional imaging. Spectral computed tomography is increasingly used in clinical practice and provides additional quantitative information beyond standard Hounsfield Unit analysis. In this study, we evaluated whether specific spectral imaging parameters can improve lesion characterization. Our findings show that changes in attenuation values between low and high keV can enhance diagnostic accuracy compared with traditional thresholds. These results may help reduce unnecessary follow-up examinations or invasive procedures and support more confident decision-making, while also encouraging further research in larger prospective cohorts.
Abstract
Background: Differentiating adrenal adenomas from non-adenomatous lesions remains a critical challenge in the management of adrenal incidentalomas. Conventional unenhanced CT relies on attenuation thresholds of 10 HU and 20 HU, which present trade-offs between sensitivity and specificity. Objectives: To evaluate the diagnostic performance of unenhanced Spectral CT using the attenuation difference between 40 keV and 140 keV virtual monoenergetic images for differentiating adrenal adenomas from non-adenomatous lesions. Methods: In this retrospective single-center study, 60 patients with adrenal lesions who underwent unenhanced dual-energy CT were included. Mean attenuation values were measured on conventional images and on virtual monoenergetic images at 40 keV and 140 keV. The spectral attenuation difference (Δ40–140 keV) was calculated. ROC analysis was performed to determine the optimal threshold and diagnostic performance. Additional analyses included DeLong comparison of correlated ROC curves and bootstrap resampling to estimate 95% confidence intervals for the area under the curve. Results: Forty-nine lesions were adenomas and eleven were non-adenomatous. The optimal threshold for Δ40–140 keV was −17 HU. When evaluated as a continuous variable, Δ40–140 keV yielded an area under the curve of 0.940 (95% confidence interval: 0.851–1.000), compared with 0.939 (95% confidence interval: 0.870–0.992) for conventional unenhanced attenuation. DeLong comparison showed no statistically significant difference between the two curves (p = 0.980). Diagnostic performance was as follows: HU ≤ 10 (AUC 0.816, diagnostic accuracy 0.70), HU ≤ 20 (AUC 0.883, diagnostic accuracy 0.87), and Δ40–140 keV ≤ −17 HU (AUC 0.940, diagnostic accuracy 0.90). The spectral attenuation difference demonstrated the highest overall diagnostic accuracy. Conclusions: Unenhanced Spectral CT using Δ40–140 keV improves discrimination between adrenal adenomas and non-adenomatous lesions compared with conventional attenuation thresholds. This technique may reduce indeterminate findings and limit the need for additional imaging.
