DISTINCTION BETWEEN BENIGN AND MALIGNANT ADRENAL MASSES - VALUE OF T1-WEIGHTED CHEMICAL-SHIFT MR-IMAGING

OBJECTIVE. Accuracy of T1-weighted chemical-shift MR imaging for the d ifferentiation between benign and malignant adrenal masses was blindly assessed among three radiologists. SUBJECTS AND METHODS. MR imaging w as performed at 1.5 T in 50 patients with 58 adrenal masses, proved be nign (n = 38) or malignant (n = 20) based on surgery or growth (malign ant) or stable size (benign) for at least 1 year, In-phase spin-echo s equences or in-phase breath-hold fast multiplanar spoiled gradient-rec alled echo (FMPSPGR) sequences with a TE of 4.2 msec were compared wit h opposed-phase breath-hold FMPSPGR sequences with a TR/TE of 35-155/2 .2-2.9 and a 90 degrees flip angle for the detection of lipid in adren al masses. Three radiologists who were blinded to diagnosis and clinic al data independently rated the likelihood of a benign adrenal lesion on a five-point scale of confidence. RESULTS. Mean sensitivity, specif icity, and positive predictive value for a definite or probable diagno sis of a benign lesion by the three readers were 87%, 92%, and 95%, re spectively. At the highest (definite) confidence of a benign lesion, t he mean positive predictive value was 99%, with lower sensitivity (54% ). Areas under receiver operating characteristic curves for the three radiologists were .98 (95% confidence interval [CI] = .94-1.00), .96 ( CI = .91-1.00), and .95 (CI = .89-1.00), Interobserver variation for t he diagnosis of a benign mass was low (kappa = .79). CONCLUSION. Chemi cal-shift imaging using breath-hold opposed-phase T1-weighted MR image s is a reliable and reproducible technique for the diagnosis of most b enign adrenal masses at the highest threshold of confidence.