Magnetic Fiducial Seeds for Tumor Localization in Video-Assisted Thoracoscopic Surgery (VATS): A Phantom and Ex Vivo Feasibility Study

Objective: In this study, we presented a method utilizing magnetic fiducial seeds and a magnetometer probe to help localize the non-palpable nodule prior to the final resection step in video-assisted thoracoscopy surgery. Methods: The magnetic fiducial seeds were built through tiny magnet with a diameter of 2 mm and a height of 1.5 mm. The magnetometer probe was used to detect the position of the magnetic seeds based on the distribution of the magnetic field strength. Two tests were conducted to evaluate the performance of the presented method. Results: In the phantom tests, results show that the average angular error, radial error, and probe tip to target distance error were 2.98 degrees, 2.96 mm, and 5.76 mm, respectively. In the case study with animal cadaver, the small fiducial seeds were inserted into the target lung of the pig cadaver under CT guidance prior to thoracoscopic surgery, and a 2.8-degree difference in the trajectories of the probe and the seed was measured and a 2.7 mm radial error was obtained between the nodule and the needle trajectory suggested by the probe. The probe tip to target distance was 9.7 mm in this case study. Conclusion:The study has shown that the presented method is an easy and convenient method to localize the target non-palpable nodule during video-assisted thoracoscopic surgery without a great impact on current clinical workflow. Significance: The VATS procedure could benefit from our proposed method.