Comparison of Lesion Conspicuity of Radiofrequency Ablation Zones among MR Sequences According to Time in the Normal Rabbit Liver

ABSTRACT

PURPOSE: To compare the lesion conspicuity of radiofrequency ablation (RFA) zones among MR sequences according to time in the normal rabbit liver. MATERIALS AND METHODS: RFA zones were created in 12 rabbit livers with a 17-gauge internally cooled electrode (1-cm active tip, 30 Watts, 3 minutes). Three rabbits were sacrificed immediately, three days, two weeks, and six weeks after the RFA procedure, respectively. Before sacrifice, T1-, T2-weighted images (WI), and gadolinium-enhanced (GE)-T1WI images were obtained. The lesion conspicuity of the RFA zone and the contrast-to-noise ratio (CNR) of the RFA zone to the liver parenchyma were analyzed and compared among the MR sequences according to time. RESULTS: On T1WI, the RFA zones were only clearly seen on acute phase. On T2WI, the RFA zones were clearly seen on all phases except the hyperacute phase. On GE T1WI, the RFA zones were clearly seen on all phases. The CNRs of the RFA zone to the liver parenchyma of GE-T1WI (8.1-12.4) were significantly higher than the CNRs of TIWI (1.6-2.7) and T2WI (1.7-6.3) on all phases (p < 0.05), but the visual lesion conspicuity between GE T1WI and T2WI were similar. CONCLUSION: On hyperacute phase, GE T1WI showed better lesion conspicuity of the RFA zone than T1WI and T2WI. On other phases, GE T1WI and T2WI showed similar lesion conspicuity.