Characterization of adrenal lesions with 1.5-T MRI: preliminary observations on comparison of three in-phase and out-of-phase gradient-echo techniques.

Abstract

The purpose of this study was to use previously described quantitative evaluation methods to compare the performance of 3D gradient-recalled echo (GRE) and magnetization-prepared (MP) GRE in-phase and out-of phase sequences with standard 2D GRE technique in the characterization of adrenal lesions. The study sample consisted of 44 consecutively registered patients (22 men, 22 women; mean age, 59.1 ± 11.6 years) with 50 adrenal lesions who underwent standard abdominal MRI that included in-phase and out-of-phase 2D GRE (n = 41), 3D GRE (n = 35), MP GRE (n = 36), or a combination of these techniques. The adrenal signal intensity (SI) index and adrenal-to-spleen, adrenal-to-liver, and adrenal-to-muscle SI ratios of each lesion were calculated and compared for the three techniques by independent samples Student t test. The area under the receiver operating characteristic (ROC) curve (AUC) for each evaluation method was determined, and comparisons of independent ROC curves were performed for all sequences. For all sequences, the mean adrenal SI index and SI ratios of adenomas and nonadenomas differed significantly (p < 0.001). For the 3D GRE and MP GRE techniques, adrenal SI index and modified adrenal-to-spleen ratio, respectively, had the larger AUCs, but the difference was not statistically significant. Different thresholds for the three techniques were recommended for discriminating adenoma from nonadenoma. The results of characterization of adrenal lesions with MP GRE and 3D GRE in-phase and out-of-phase MRI techniques are comparable to those obtained with the reference standard 2D GRE technique. Different thresholds should be selected according to the in-phase and out-of-phase techniques used and for the various evaluation methods.