Feasibility of extracellular volume fraction derived from single-phase spectral CT for differentiating between adrenal metastases and adenomas.

Abstract

Purpose: The extracellular matrix of adrenal metastases could be different from that of the adrenal adenomas, which may be characterized by the extracellular volume (ECV) fraction. This study aimed to assess the feasibility of ECV fraction derived from single-phase spectral CT for differentiating between adrenal metastases and adenomas.

Methods: This retrospective study included 163 patients with unilateral nodules, including lipid-poor adrenal adenoma (n = 52, group A), lipid-rich adrenal adenoma (n = 65, group B) and adrenal metastasis (n = 46, group C). All patients underwent contrast-enhanced spectral CT of the adrenal gland with a 10-minute delayed phase. The iodine density of each lesion was assessed and ECV fraction was examined. Various parameters were compared among the three groups. Diagnostic performance was evaluated by quantifying the area under the receiver operating characteristic curve (AUC).

Results: The ECV fraction in group C (33.81 ± 11.94%) was significantly higher than that in group A (20.86 ± 10.22%) and group B (11.44 ± 6.26%) (p < 0.001), while iodine density in group C (0.93 ± 0.41 mg/mL) was also higher than that in group A (0.61 ± 0.33 mg/mL) and group B (0.33 ± 0.19 mg/mL) (p < 0.001). ECV fraction showed significantly higher AUC (AUC = 0.790, 95%CI 0.691-0.869) for differentiating between group A and C than iodine density (AUC = 0.717, 95%CI 0.612-0.808; p = 0.002). Simultaneously, ECV fraction had significantly higher AUC (AUC = 0.945, 95%CI 0.858-0.986) for differentiating between group B and C than iodine density (AUC = 0.897, 95%CI 0.795-0.959, p = 0.03).

Conclusion: Based on single 10-minute delayed phase spectral CT, ECV fraction showed high diagnostic performance in differentiating between adrenal metastases and adrenal adenomas, both for lipid-poor or lipid-rich adenomas. The ECV fraction could help recognize metastases in unilateral or bilateral adrenal masses for better treatment planning, especially in patients with a history of extra-adrenal malignancy.