The Utility of Multiparametric MRI or Difffferentiating Adrenal Adenomas from Adrenal Metastases

Abstract

Purpose: To evaluate the possibility of multiparametric MRI in the differential diagnosis of benign adrenal adenomas and adrenal metastases.Material and methods: In our study we evaluated 27 adenomas and 13 adrenal metastases using MRI in 35 patients who underwent examination and treatment at the basis of the N.N. Blokhin National Research Center of Oncology during the follow-up period from 2019 to 2021. The following parameters were evaluated: contours, homogeneity (homogeneous and heterogeneous), T2-weighted SI ratio (isointensive, moderately hyperintensive or sharply hyperintensive) relative to muscle and spleen, signal intensity (SI) decrease on chemical-shift MRI, measurement of the chemical-shift SI index, adrenal-to-spleen SI ratio, areas under the ROC curve (AUC) for contrast-enhanced MRI, absolute and relative percentage wash-out. Sensitivity, specificity, and positive and negative predictive values were calculated. DWI with b-values 400 and 800 s/mm2 and ADCs imaging were measured in adrenal lesions.Results: Metastases were subjectively more heterogeneous than adenomas (76.9  % vs 63  % of cases, p = 0.0181). Adenomas had higher T2-weighted SI (average value = 228; range from 91 to 732) than metastases (average value  =  331; range from 114 to 581), both quantitatively (p  =  0.0326) and subjectively by visual assessment (p = 0.0171).According to the T1-WI out-of-phase data, a more intense MR signal was observed in metastases (average value 162; range from 102 to 242) compared with adenomas (average value = 74; range from 17 to 183) (p < 0.0001), which was confirmed by normalization to muscle (p < 0.0001) and spleen (p = 0.0002). Adrenal metastases were characterized by a significantly lower chemical shift index (average value = 3.8; range from –16.4 to 47.8; p < 0.0001) compared with adenomas (average value 55.4; range from –4.2 to 85.5), and a higher chemical shift index in the ratio adrenal gland/spleen (p = 0.0079). There were no significant difference in the value of ADC-cards of adenomas and adrenal metastases. However, a higher level of SI on DWI at b = 800 s/ mm2 without normalization (p = 0.0262) and with normalization to muscle (p = 0.0064) and spleen (p = 0.0007) was evaluated in metastases, as well as on DWI at b = 400 s/mm2 with normalization for muscle (p = 0.0086) and spleen (p = 0.035). On native T1-WI FS, there was a lower level of SI revealed in adenomas compared to adrenal metastases (p  =  0.0025), which was confirmed by normalization to the muscle (p  =  0.0028) and spleen (p = 0.0035). In the venous and delayed phases of scanning the SI in adenomas was also lower than in metastases both without normalization (p = 0.0123 and p = 0.007, respectively), and with normalization to the muscle (p = 0.013 and p = 0.0011, respectively) and the spleen (p = 0.0084 and p = 0.0012, respectively). However, the SI in the arterial phase of scanning with and without normalization, the accumulation of MRCS in all phases of MRI scanning, the absolute and relative percentage wash-out of MRCS and the area under the MRCS accumulation curve in the groups had no statistically significant difference.