Design and validation of a surgical navigation system for brachytherapy based on mixed reality

An accurate position of the needle is vitally important in low-dose-rate seed implantation brachytherapy. Our paper aims to implement a mixed reality navigation system to assist with the placement of the I¹²⁵ seed implantation thoracoabdominal tumor brachytherapy needle and to validate the accuracy and quality of this type of method.

With the surgical navigation system, based on mixed reality through a novel modified multi-information fusion method, the fusion of virtual organs and a preoperative plan for a real patient and the tracking of surgical tools in real time were achieved. Personalized image recognition and pose estimation were used to track needle punctures in real time and to perform registration processes. After a one-time registration with a hexagonal prism tracker that used an iterative closest point algorithm, all information, including medical images and volume renderings of organs, needles, and seeds, was precisely merged with the patient. Doctors were able to observe the tumor target and to visualize the preoperative plan. This system was validated in both phantom and animal experiments. The accuracy of this system was validated by calculating the positional and rotational error of each needle insertion. The accuracy of implantation of each seed was determined in an animal experiment to test the accuracy in low-dose-rate brachytherapy. The efficiency of this system was also validated through time consumption assessments.

In the phantom experiment, the average error of the needle locations was 0.664 mm and the angle error was 4.74°, average time consumption was 16.1 min with six needles inserted. Based on the results of the animal experiment, the accuracy of the needle insertion was 1.617 mm, while the angle error was 5.574° and the average error of the seed positions was 1.925 mm.

This paper describes the design and experimental validation of a novel surgical navigation system based on mixed reality for I¹²⁵ seed brachytherapy for thoracoabdominal tumors. This system was validated through a series of experiments, including phantom experiments and animal experiments. Compared with the traditional image-guided system, the procedure presented here is convenient, displays clinically acceptable accuracy and reduces the number of CT scans, allowing doctors to perform surgery based on a visualized plan. All the experimental results indicated that the procedure is ready to be applied in further clinical studies.