Is it Possible to Assess the Functional Status of Hormone Secretion or Non- Secretion of Adrenal Masses Through Their Magnetic Resonance Imaging (MRI) Characteristics?

Background: Diagnostic imaging techniques, including magnetic resonance imaging (MRI) should be performed on all patients with incidentalomas. However, limited number of studies on whether the quantitative measurements (signal intensity index, adrenal to spleen ratio) in MRI could predict the functional status of adrenal adenomas are available. Methods: Between 2015-2020, 404 patients (265 females, 139 males) with adrenal mass who were referred to the university hospital for further investigation were included. After detailed diagnostic hormonal evaluation, all patients were examined with the MRI 1.5 T device (Signa, GE Medical Systems; Milwaukee, USA). The signal intensities of the adrenal lesions on T2W images were qualitatively evaluated and noted as homogenous or heterogeneous in comparison with the liver signal intensity (SI). A chemical-shift SI index and chemical shift adrenal-to-spleen SI ratio were also calculated. Results: While 331(81.9%) of the patients had nonfunctional adrenal mass, the rest (n=73, 18.1%) were patients with functional (autonomous cortisol secretion-ACS, Cushing syndrome-CS, pheochromocytoma, primary hyperaldosteronism-PA) adrenal masses. In phase vs. phase values of patients with NFAI, Pheo(n=17), ACS (n=30), CS (n=11), and PA (n=15) were 474.04±126.7 vs. 226.6±132.4, 495.3±182.8 vs. 282.17±189.1, 445.2±134.8 vs. 203.3±76.2, 506.8±126.5 vs. 212.2±73.6 and 496.2±147.5 vs. 246.6±102.1, respectively. Mean signal intensity index (SII) and adrenal to spleen ratio (ASR) of all groups (NFAI, Pheo, ACS, CS, PA) were 52.0±24.8 and 0.51, 44.9±22.5 and 0.55, 49.5±24.5 and 0.53, 56.2±16.4 and 0.43, 47.6±25.1 and 0.54, respectively. Based on the currently accepted measurements in the case of ASR and SII, all lesions were similar and observed as fat rich adenomas (p*= 0.552, p** = 0.45). Conclusion: The quantitative assessment (SII, ASR) of intracellular lipids in an incidentally discovered adrenal tumor could only help distinguish adrenal masses in the case of adenomas or non-adenomas. As an initial diagnostic evaluation, clinical and laboratory assessment to distinguish hormone secretion should be done for all patients with adrenal incidentalomas.