Improved diagnosis of incidental adrenal masses by dual-energy CT

1. Contrast-enhanced dual-energy computed tomography (CT) may accurately differentiate benign adrenal adenomas from other potentially malignant lesions using fat-iodine material density analysis with a sensitivity and specificity of 96% and 100%, respectively.

2. Material-density analysis may allow non-invasive diagnostic evaluation of incidental adrenal masses based on the lipid-content as evaluated by fat-water and fat-iodine images.

Evidence Rating Level: 3 (Average)

Study Rundown: Incidental adrenal masses are commonly found during abdominal imaging studies and often require a protracted diagnostic workup to differentiate benign masses such as adenomas from malignant masses. With the advent of dual-energy multidetector CT scanners, the physical composition of a particular lesion can be profiled using a process known as material density analysis, which differentiates biologic materials on the basis of differing densities to produce characteristic imaging findings. This can be used to better distinguish tissue types on the basis on contrast uptake, lipid and water content, and mineralization.

The present study retrospectively examined a small cohort of patients with known adrenal nodules using both non-contrast and contrast-enhanced dual-energy multidetector CT of the abdomen. To determine lesion type, unenhanced CT density values were compared to the corresponding dual-energy material density values of fat-iodine and fat-water for each adrenal mass. The study authors found that the use of material density analysis allowed for superior differentiation of adrenal adenomas from nonadenomatous lesions when compared to nonenhanced CT imaging alone. The study was limited by its small sample size and potential for selection bias in that all nonadenoma subjects were oncologic patients with known adrenal metastatic disease. Future prospective studies utilizing a larger patient cohort and a more heterogenous population of adrenal lesions is necessary to more definitively define the diagnostic utility of contrast-enhanced dual-energy CT imaging.

Click to read the study in Radiology

Relevant Reading: Adrenal Masses: Characterization with combined unenhanced and delayed enhanced CT

In-Depth [retrospective cohort]: This study examined 38 patients (58% male, 42% female) with 47 known adrenal nodules, comparing the specificity of lesion identification by nonenhanced multidetector CT with that of contrast-enhanced dual-energy multidetector CT using material density analysis. Dual-energy density measurements of fat-iodine, iodine-fat, fat-water and water-fat were recorded alongside nonenhanced CT lesion density values. Significant differences in all mean material density values were recorded for both lipid-rich and lipid-poor types of adenomas as compared to nonadenomas (P<0.0001), demonstrating a sensitivity of 96% (23 of 24 adenomas identified) with a set sensitivity of 100%. Nonenhanced CT density-based identification only successfully identified 16 of 24 adenomas, resulting in a significantly lower sensitivity of 67% with a set specificity of 100% (P=0.035). Of the identified adenomas, 33% were lipid-poor and were still accurately identified primarily on the basis of a single fat-iodine density value, thresholded at 997 mg/cm3. All nonadenomatous lesions identified were metastatic malignancies in the selected patient population.

Image: PD

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