Characterization of adrenal adenomas and metastases: correlation between unenhanced computed tomography and chemical shift magnetic resonance imaging.

Purpose: To evaluate the correlation of absolute attenuation values of unenhanced computed tomography (CT) with signal intensity (SI) quantitative analysis on chemical shift (CS) magnetic resonance (MR) imaging in differentiating adrenal adenomas from metastases.Material and Methods: Forty-one adrenal masses (27 adenomas, 14 metastases) were studied with CS MR imaging and unenhanced CT. MR included T1-weighted breathhold gradient-echo in-phase (IP) and opposed-phase (OP) sequences. The SI index (SI-i) [(SIIP−SIOP/SIIP)]×100% and chemical-shift ratio (CS-r) relative to the spleen [(SIlesion/SIspleen)OP/(SIlesion/SIspleen)IP] were calculated for each lesion. CT absolute attenuation values were also determined.Results: The mean attenuation value of metastases was significantly greater than that of adenomas (<0.0001). On MR, the mean SI-i of adenomas was significantly greater than that of metastases (P<0.0001) and no overlaps were evident. The CS-r of malignant and benign lesions overlapped considerably, and ...