MR-GUIDED INTERSTITIAL CRYOTHERAPY OF THE LIVER WITH A NOVEL, NITROGEN-COOLED CRYOPROBE

The purpose of the study was to test a newly developed, MR-compatible, liquid nitrogen-cooled cryoprobe. The probe has an outer diameter of 3.5 mm and was specifically developed for percutaneous, MR-guided, int erstitial cryotherapy. The probe was inserted percutaneously into the livers of 10 rabbits. The cryotherapy procedure was monitored with a s urface coil in a 1.5 Tesla magnet using a gradient echo sequence. Foll ow-up examinations were performed 3 and 7 days after the freezing proc edure using T-1- and T-2-weighted spin echo sequences. At 7 days the a nimals were sacrificed and the cryolesions were examined histologicall y. The cryoprobe enabled artifact-free MR imaging of the ''ice-ball'' formation during freezing of the rabbit liver. After 1 min of freezing , the iceball at the tip of the probe showed an average maximum diamet er of 10.8 mm. No bleeding complications were observed during or after the freezing procedure. Histologic examination 7 days after cryothera py confirmed that the Liver lesions were the same size as had been pre dicted by the images of the acute iceball. This new, percutaneously in serted, MR-compatible, liquid-nitrogen cooled cryoprobe allows accurat e, artifact-free MR imaging of interstitial cryotherapy.