Calibration developments for multicamera optical tracking systems.

Intra-Operative Electron Radiation Therapy (IOERT) is a technique for cancer treatment that delivers a high dose of radiation directly to the post-resected tumour bed or to an unresected tumour during surgery. Recently, a tracking system (OptiTrack, NaturalPoint Inc., USA) was installed into the operating room that allows for navigation and thus assist oncologists in the treatment planning of this procedure. The system is an optical tracking system composed of eight independent cameras, and then a calibration process is required for a correct tracking performance. The current state consists on calibrating just before every IOERT procedure, increasing surgery preparation time by approximately one hour.

In order to study the feasibility of defining new calibration protocols based on calibrating every certain period of time, this project assesses the temporal stability of tracking system calibrations and determines an optimum methodology for the detection of miscalibration within the tracking system.

To achieve this, software applications were developed to control the Optitrack system by means of the Application Programming Interface provided by the vendor. Also, a group of experiments were performed using developed applications to acquire tracking data.

Results show the temporal stability of the tracking system calibration during five days, and the feasibility of detecting tracking system miscalibrations by using the proposed methodology.

This study will allow the hospital to save time and resources by stablishing protocols for calibration in which calibration is performed every 2-5 days. The calibration state of the system will be evaluated before every surgery in order to determine if the system needs to be calibrated or not following a proposed methodology (with an average duration of 5 minutes).