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Percutaneous ablation is a viable treatment option for patients with early-stage hepatocellular carcinoma (HCC) who are not candidates for surgical resection or liver transplantation,1 but the efficacy of this procedure depends heavily on the surgeon’s ability to place the ablation probe accurately into the target tumor. This paper introduces a surgical navigation system for guiding an ablation needle percutaneously, using an electromagnetic tracking system and a mini-stereotactic aiming device. A clamp to attach an EM sensor was designed to attach to the a patient-attached needle guider. The pose information from the guider sensor after calibration was used to project a virtual line that follows the needle guider movements, and shows the applicator path before insertion. A surgical navigation application was developed in the 3D Slicer platform and a pose calibration technique was incorporated to ensure that the virtual needle path that is projected from the needle guider aligns with the physical needle once a needle is inserted into the guider. The estimated ablation zone, based on manufacturer’s guidelines, is displayed at the tip of the virtual path to help the user ensure total tumor coverage. The guidance software allows updating the estimated ablation zone in real-time depending on the treatment specifications. The ablation zone is displayed as a 3D model and as an ellipse overlaid on the 2D ultrasound video. A rotation analysis to obtain the angular error between two virtual lines (guider and a pre-calibrated needle) was performed in two different setups. The first was the ideal setup without anything that could bend the pre-calibrated needle, and the second used a Polyvinyl Alcohol cryogel Phantom. The results for the rotation analysis, mean and STD, for the ideal setup, was (0.33 ± 0.29)°; while using the PVA-c phantom the results (2.70 ± 0.07)°. These results suggest that the disposable mini-stereotactic needle guider has the potential to assist the surgeons in the accurate placement of the ablation needle in the clinical setting.
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