Value of CT volume imaging for optimal placement of radiofrequency ablation probes in liver lesions

PURPOSE: To determine the value of multiplanar and volume-rendered modes of analysis versus axial imaging for the optimal placement of probes in spiral image computed tomography (CT)-guided radiofrequency (RF) ablation of liver lesions. MATERIALS AND METHODS: Thirty-two malignant hepatic lesions in 21 patients with hepatocellular carcinoma (n = 10) or metastases (n = 11) were treated with percutaneous RF ablation. After axial CT-guided placement (biopsy mode) of the probe in the tumor, a contrast-enhanced spiral image set was obtained and data were viewed in contiguous axial sections and the multiplanar and volume-rendered modes. The position of the probe was characterized as "central," "marginal," or "outside," corresponding with its position in the lesion. Outside positioning was corrected before ablation was performed and, in cases of "marginal" positioning, the probe was redirected after initial ablative therapy in the same session. RESULTS: Multiplanar and volume-rendered analysis reclassified the needle position before 14 of 32 RF ablation procedures (44%; P =.0034, McNemar test). In 10 cases, probe positions considered "central" on biopsy-mode images were found to be "marginal" with multiplanar/volume-rendered analysis. In three cases, probe positions considered "marginal" on biopsy-mode images were found to be "outside" with multiplanar/volume-rendered analysis. In one lesion, multiplanar/volume-rendered analysis upgraded the probe position from "marginal" to "central." Comparison of multiplanar and volume-rendered analysis revealed no difference in probe positioning. The time requirements to obtain additional data were 159 seconds +/- 49 for multiplanar analysis and 434 seconds +/- 78 for volume-rendered analysis. CONCLUSION: A contrast-enhanced spiral CT image data set with multiplanar reformations to verify an optimal probe location after axial CT-guided needle placement should be obtained before RF ablation of liver lesions.