Application of a 3D volumetric display for radiation therapy treatment planning I: quality assurance procedures

Abstract

Purpose: To design and implement a set of quality assurance tests for an innovative 3D volumetric display for radiation treatment planning applications. Methods: A genuine 3D display (Perspecta Spatial 3D, Actuality-Systems Inc., Bedford, MA) has been integrated with the Pinnacle TPS (Philips Medical Systems, Madison WI), for treatment planning. The Perspecta 3D display renders a 25 cm diameter volume that is viewable from any side, floating within a translucent dome. In addition to displaying all 3D data exported from Pinnacle, the system provides a 3D mouse to define beam angles, apertures and measure distance. The focus of this work is the design and implementation of a quality assurance program for 3D displays and specific 3D planning issues as guided by AAPM Task Group Report 53. A series of quality assurance tests have been designed to document the spatial accuracy of the CT images, contours, beams and dose distribution as displayed on Perspecta. Three dimensional matrices and rulers and phantoms with known spatial dimensions were used to check Perspecta’s absolute spatial accuracy. In addition, a system of tests were designed to confirm Perspecta’s ability to import and display Pinnacle data consistently. CT scans of phantoms were used to confirm beam field size, divergence and gantry and couch angular accuracy as displayed on Perspecta. Beam angles were verified through Cartesian coordinate system measurements and by CT scans of phantoms rotated at known angles. Beams designed on Perspecta were exported to Pinnacle and checked for accuracy. Dose at sampled points were checked for consistency with Pinnacle and agree within 1% and 1mm. Results: All data exported from Pinnacle to Perspecta was displayed consistently.  The 3D spatial display of images, contours and dose distributions were consistent with Pinnacle display. When measured by the 3D ruler, the distances between any two points calculated using Perspecta agreed with Pinnacle within the measurement error (