Comparative study of CT and MR guided cryoablation for hepatic tumors

Abstract

Objective To compare CT and MR imaging in guiding and monitoring cryoablation of hepatic tumors. Methods A total of 131 lesions in 121 patients with malignant tumors of liver were treated with imaging-guided percutaneous cryotherapy. There were 73 males and 48 females, mean age 60 years. Of the 121 patients, 61 patients had cryoablation under CT guidance and 60 patients under the guidance of MRI. CT-guidance was performed with the Philips big-bore CT in spiral mode, with 5 mm slice thickness.The MR guidance was performed with GE 0.35 T scanner assisted with infrared navigator (Xinaomdt), and both fast gradient echo sequence and fast spin-echo sequence were used. The cryoablation system is a magnetic resonance compatible system (Galil, Israel), equipped with 17 G cryoprobes that are 1.47 mm in outside diameter. A combination of multiple eryo-probes and conformal cryoablation were adopted in accordance with the location, the shape and the adjacent structure of each lesion. Each cryoablation included two freezing-thawing cycles. Scanning was performed intermittently during the operation to monitor the degree of ablation. The mean scanning time, the lesion depiction and ablation process monitoring, the efficacies of lesion ablation, complications,and survival time were analyzed with x2 test Results The mean scanning time was (5.6±1.8)min for CT and (22.0±2.6)min for MR. CT provideda good depiction of the lesion and the ribs which were poorly displayed on MR images. The metal probe could create artifacts on the CT images and it was difficult for CT to show the formation of ice ball of the lesion formed after embolization with lipiodol. MR was superior to CT in displaying, guiding and monitoring of ablation of lesions near such special ragions as the diaphragm dome, the hepatic hilum, and the gallbladder. MR was not affected by high-density embolization material and the metal probes, and thus was superior to CT in depicting the lesion,and monitoring the formation of ice ball and the process of lesion ablation, etc.However, MR scan was time consuming, and image quality of low-field open MR was less desirable than that of CT. The 12-month overall survival rates were 90.2%(55/61) and 90.0%(54/60), respectively. The overall efficacies of lesion ablation were 75.4%(46/61) and 83.4%(50/60), respectively. Conclusion CT has advantages of fast scanning and good display of such structures as ribs in the path of puncture as compared with MR. MR can display a lesion with multi-planar imaging, and is superior to CT in monitoring the procedure of ablation,especially in displaying, guiding and monitoring ablation of lesions near such special regions as the diaphragm dome, the hepatic hilum, and the gallbladder. Key words: Liver neoplasms; Radiology,interventional; Comparative study