SU-E-J-75: Practical Annual Quality Assurance Program for a Real Time Optical Tracking System

To verify the accuracy of a real time optical surface tracking system using a practical annual quality assurance program with an anthropomorphic breast phantom.

An anthropomorphic breast phantom was used to determine the accuracy of registration, shift, source to surface distance (SSD), and live monitoring features of the AlignRT system. Both the two and three camera AlignRT systems were tested. Registration and shift accuracy were evaluated by comparing software output with known phantom displacements and rotations at 0, 90, and 270 couch angles. These tests were performed in static capture and live monitoring modes. SSD accuracy was determined by comparing AlignRT results with expected values from the treatment planning system and optical distance indicator at 0, 90, and 270 degree couch rotations.

For the two camera system, registration accuracy at 0, 90, and 270 degree couch angles was within 1.0mm in the lateral, longitudinal, and vertical directions and 0.04 degree. For shifts of +/-10mm and +/-5 degree, static mode shift accuracy was within 1.6mm and 0.23 degree. Registration accuracy of the shifted phantom in live monitoring mode was within 1.7mm and 0.2 degree. For the three camera system, registration accuracy at 0, 90, and 270 degree couch angles was within 1.1 mm in the lateral, longitudinal, and vertical directions and 0.2 degree. For shifts of +/-10mm and +/-5 degree, static mode shift accuracy was within 0.9mm and 0.2 degree. Registration accuracy of the shifted phantom in live monitoring mode was within 1.1mm and 0.2 degree. SSD determination was accurate to within 2mm for both systems and modes.

The AlignRT system accuracy can be easily verified for annual quality assurance using a realistic clinical setup to within 2mm/0.5 degree. System accuracy was comparable for both two and three camera systems in static and live monitoring modes.