ADRENAL MASSES - CORRELATION BETWEEN CT ATTENUATION VALUE AND CHEMICAL-SHIFT RATIO AT MR-IMAGING WITH IN-PHASE AND OPPOSED-PHASE SEQUENCES

PURPOSE: To correlate attenuation values at computed tomography (CT) w ith signal intensity at chemical-shift magnetic resonance (MR) imaging in adrenal masses. MATERIALS AND METHODS: Thirty-eight patients with 47 adrenal lesions underwent MR imaging and unenhanced CT examinations . MR examinations, performed at 1.5 T, included T1-weighted imaging wi th fat and water in phase and gradient-echo imaging with fat and water out of phase (repetition time, 45-180 msec; echo time, 1.4-3.1 msec). Lesion-to-spleen signal intensity ratios were calculated for the in-p hase and opposed-phase images. The chemical-shift ratio, a measure of signal intensity loss between in-phase and opposed-phase images, and t he CT attenuation value (in Hounsfield units) were determined for each lesion. RESULTS: A statistically significant correlation (0.85) was f ound between attenuation and chemical-shift-ratio values (P < .000001) . Attenuation in six benign lesions was within 2 standard deviations o f the mean attenuation in malignant lesions, and the chemical-shift ra tio in eight benign lesions was within 2 standard deviations of the me an chemical-shift ratio in malignant lesions. Six of these eight lesio ns were misclassified on the basis of both attenuation and chemical-sh ift-ratio values. CONCLUSION: CT attenuation values are highly correla ted with chemical-shift ratios. Both values were indeterminate for a s imilar subset of benign lesions.