Experimental cryosurgery of the liver under magnetic resonance guidance

The feasibility and the advantages of magnetic resonance (MR)-guided interstitial cryosurgery of the liver in an 0.5 Tesla open MR system have been evaluated. Cryosurgery was performed using an Erbocryo PS system with a nonmagnetic cryoprobe of 6 mm diameter. The probe was inserted into the liver parenchyma under real-time MR control. Using continuous MR imaging two freezing cycles of 12 min each were applied. After conventional and dynamic gadolinium-enhanced MR imaging, the animals were sacrificed after 30 min, 3 hr, 24 hr, 7 days, and 21 days. Each lesion was analyzed using light microscopy. A total of seven cryolesions were made in five animals without any complications from cryosurgery. During real-time imaging, cryolesions appeared as a hemispherical growing signal loss with a mean volume of 16.4 cm3. Macroscopic volumes of the lesions showed a good correlation with dynamic enhanced MR images during follow-up, whereas real-time images usually showed an underestimation of the lesion volumes. Cryosurgery of the liver in an open-configuration MR system is a feasible and safe method. MR imaging allows the guidance and the follow-up of cryolesions of the liver with good accuracy.