MR monitoring of laser-induced lesions of the liver in vivo in a low-fieldopen magnet: Temperature mapping and lesion size prediction

The aims of this study were, firstly, to monitor temperature with magnetic resonance (MR) during laser ablations performed in pig livers in vivo in a low-field open scanner (0.23T) and, secondly, to study the feasibility of l esion size prediction. Spin-echo (SE) images of 29 sec acquired during lase r applications allowed calculation of temperature maps using T-1 and M-0 te mperature sensitivity. Temperature was also measured with thermocouples. Im ages of prediction of tissue damage were calculated using temperature maps and Arrhenius model. T2W sequences were acquired after the ablations. Anima ls were sacrificed immediately. Lesions were photographed macroscopically. Lesion surfaces were measured and compared in T2W images, temperature image s, damage prediction Images, and macroscopic pictures. A correlation exists between temperature measured with MR and with thermocouples (rho = 0.878; P < 0.001, Spearman test). Mean surface of predicted damaged tissue is cons istent with mean early necrosis measured in macroscopic pictures. Early T2W images underestimate mean necrosis size. (C) 2001 Wiley-Liss, Inc.