Program Information
Design, Evaluation and First Applications of a Off-Site State-Of-The-Art 3D Dosimetry System
J Malcolm1*, S Mein2 , A McNiven3 , D Letourneau4 , M Oldham5 , (1) Duke Medical Physics Graduate Program, Durham, NC, (2) Duke Medical Physics Graduate Program, Durham, NC(3) Princess Margaret Cancer Centre, Toronto, ON, (4) Princess Margaret Cancer Centre, Toronto, ON, (5) Duke University Medical Center, Durham, NC
Presentations
SU-D-213-5 (Sunday, July 12, 2015) 2:05 PM - 3:00 PM Room: 213
Purpose:To design, construct and commission a prototype in-house three dimensional (3D) dose verification system for stereotatic body radiotherapy (SBRT) verification at an off-site partner institution. To investigate the potential of this system to achieve sufficient performance (1mm resolution, 3% noise, within 3% of true dose reading) for SBRT verification.
Methods:The system was designed utilizing a parallel ray geometry instigated by precision telecentric lenses and an LED 630nm light source. Using a radiochromic dosimeter, a 3D dosimetric comparison with our gold-standard system and treatment planning software (Eclipse) was done for a four-field box treatment, under gamma passing criteria of 3%/3mm/10% dose threshold. Post off-site installation, deviations in the system’s dose readout performance was assessed by rescanning the four-field box irradiated dosimeter and using line-profiles to compare on-site and off-site mean and noise levels in four distinct dose regions. As a final step, an end-to-end test of the system was completed at the off-site location, including CT-simulation, irradiation of the dosimeter and a 3D dosimetric comparison of the planned (Pinnacle³) to delivered dose for a spinal SBRT treatment(12 Gy per fraction).
Results:The noise level in the high and medium dose regions of the four field box treatment was relatively 5% pre and post installation. This reflects the reduction in positional uncertainty through the new design. This At 1mm dose voxels, the gamma pass rates(3%,3mm) for our in-house gold standard system and the off-site system were comparable at 95.8% and 93.2% respectively.
Conclusion:This work will describe the end-to-end process and results of designing, installing, and commissioning a state-of-the-art 3D dosimetry system created for verification of advanced radiation treatments including spinal radiosurgery.
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