Mixed reality-guided intraoperative visual support for combined intracavitary and interstitial brachytherapy for cervical cancer.

Purpose: This study aimed to develop and evaluate a mixed reality-guided intraoperative visual support system for safe and accurate needle applicator insertion for combined intracavitary and interstitial brachytherapy (IC/IS-BT). Materials and Methods: A QR code was printed as a position and scale alignment reference when merging the real and virtual worlds. The QR code was positioned near the RANDO phantom, and MRI and CT scanning were performed. Treatment planning data, including the target and organs at risk structures and dose distribution from a cervical cancer patient who underwent brachytherapy, were attached to MRI and CT images of the RANDO phantom using a radiation treatment planning system and stored as DICOM data. DICOM data were then converted to object files (OBJ) that represent 3D shapes. These OBJ files were imported into the computer-generated virtual world, and the mixed reality application was built and executed on head-mounted displays (HMDs). Results: The system successfully merged the real and virtual worlds through the HMD, displaying 3D support data on the phantom. This system allows all HMD wearers to share 3D support data. Positions and scales between the real and virtual worlds are aligned using the upper left-hand corner of the QR code as the reference point, and the worlds are merged. Phantom-based evaluations demonstrated that projection errors measured by Operator A were 3.1 ± 1.1 mm in the anterior-posterior (A-P) direction and 2.6 ± 1.1 mm in the right-left (R-L) direction; corresponding projection errors for Operator B were 2.1 ± 1.4 mm in the A-P direction and 2.4 ± 1.1 mm in the R-L direction (n = 10 measurements per operator). The average frame rate was 69.7 ± 11.5 fps, corresponding to a latency of 14 msec. Conclusions: This report presents the system configuration, accuracy assessment and potential clinical applications for IC/IS-BT.