Diagnostic accuracy of chemical-shift MR imaging to differentiate between adrenal adenomas and non adenoma adrenal lesions.

PURPOSE: The objective of this study was to evaluate the diagnostic accuracy of chemical-shift (CS) magnetic resonance (MR) imaging in the differential diagnosis of adenoma and nonadenoma adrenal masses. MATERIALS AND METHODS: We enrolled 36 patients (9 men, 27 women, mean age 51.3+14.4 years) with unilateral (n=31) or bilateral (n=5) adrenal masses incidentally discovered during imaging examinations [ultrasound (US), computed tomography (CT)] performed for other indications. A total of 41 adrenal lesions were evaluated (mean diameter 3.0+2.2 cm). Histology (n=19), biopsy (n=3) or clinical-imaging follow-up (n=19) demonstrated 29 adenomas, five pheochromocytomas, three cysts and four carcinomas. MR imaging was performed using the following breath-hold sequences: T1-fast field echo (FFE) [repetition time (TR)/echo time (TE)=236/4.6 ms], T2-turbo spin echo-single shot (TSE-SSh) (TR/TE=831/80 ms), T1-DUAL-FFE (TR=236, double TE=4.6/2.3 ms in phase and out of phase) and T1-FFE after gadolinium-DTPA (Gd). Axial and coronal imaging planes were used, with a slice thickness of 3-5 mm. MR images were qualitatively assessed for signal intensity of the adrenal mass relative to the liver on T1, T2, CS and T1-Gd scans; diagnostic criteria for adenomas were isointensity or hypointensity on both T1 and T2 scans, out-of-phase CS signal loss and mild transient enhancement after Gd. RESULTS: Analysis of T1-T2 signal intensity showed diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 80%, 72%, 100%, 100% and 60%, respectively. In contrast, analysis of CS and T1-Gd signal intensity showed diagnostic accuracy, sensitivity, specificity, PPV and NPV for both sequences of 93%, 90% (p<0.05 vs. T1-T2 analysis), 100%, 100% and 80% (p