Detection of Hepatic Lesion: Comparison of Free-Breathing and Respiratory-Triggered Diffusion-Weighted MR imaging on 1.5-T MR system

ABSTRACT

PURPOSE: To compare free-breathing and respiratory-triggered diffusion-weighted imaging on 1.5-T MR system in the detection of hepatic lesions. MATERIALS AND METHODS: This single-institution study was approved by our institutional review board. Forty-seven patients (mean 57.9 year; MF = 2522) underwent hepatic MR imaging on 1.5-T MR system using both free-breathing and respiratory-triggered diffusion-weighted imaging (DWI) at a single examination. Two radiologists retrospectively reviewed respiratory-triggered and free-breathing sets (B50, B400, B800 diffusion weighted images and ADC map) in random order with a time interval of 2 weeks. Liver SNR and lesion-to-liver CNR of DWI were calculated measuring ROI. RESULTS: Total of 62 lesions (53 benign, 9 malignant) that included 32 cysts, 13 hemangiomas, 7 hepatocellular carcinomas (HCCs), 5 eosinophilic infiltration, 2 metastases, 1 eosinophilic abscess, focal nodular hyperplasia, and pseudolipoma of Glisson's capsule were reviewed by two reviewers. Though not reaching statistical significance, the overall lesion sensitivities were increased in respiratory-triggered DWI [reviewer1 reviewer2, 47/62(75.81%)45/62(72.58%)] than free-breathing DWI [44/62(70.97%)41/62(66.13%)]. Especially for smaller than 1 cm hepatic lesions, sensitivity of respiratory-triggered DWI [24/30(80%)21/30(70%)] was superior to free-breathing DWI [17/30(56.7%)15/30(50%)]. The diagnostic accuracy measuring the area under the ROC curve (Az value) of free-breathing and respiratory-triggered DWI was not statistically different. Liver SNR and lesion-to-liver CNR of respiratorytriggered DWI (87.6+/-41.4, 41.2+/-62.5) were higher than free-breathing DWI (38.8+/-13.6, 24.8+/-36.8) (p value <0.001, respectively). CONCLUSION: Respiratory-triggered diffusion-weighted MR imaging seemed to be better than free-breathing diffusion-weighted MR imaging on 1.5-T MR system for the detection of smaller than 1 cm lesions by providing high SNR and CNR.