MR monitoring during cryotherapy in the liver: predictability of histologic outcome.

For well-controlled application of cryotherapy to focal liver lesions, real-time monitoring is necessary to limit the final necrotic effect in the treated area. In this study, near real-time magnetic resonance (MR) monitoring images of normal rabbit liver were obtained during the freezing procedure. The MR-monitored, freezing-induced lesions were followed with MR images for up to 3 weeks. Corresponding histologic samples were also obtained over the same time period. Our results indicate that MR images obtained during the freezing procedure can adequately depict the area of final necrosis. Furthermore, histologic changes at each stage of lesion development correlated well with MR signal intensities on follow-up images. With the development of an MR-compatible cryogen probe, MR imaging may prove to be a robust method for monitoring, controlling, and following up cryotherapy in the liver.