Program Information
Investigation of Treatment Delivery Variation Effects On Delivered Dose for Several Treatment Sites
D Defoor*, S Stathakis , N Papanikolaou , University of Texas HSC SA, San Antonio, TX
Presentations
SU-I-GPD-T-492 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To compare and quantify the reproducibility of radiotherapy treatments for different treatment sites to better understand the potential consequences of plan complexity.
Methods: MLC log files were analyzed and fractional dose recalculated for 5 head and neck, brain, and prostate patients for a total of 15 patients. MLC log files were recorded for each fraction and the MLC positions in the original plan were replaced by the recorded MLC positions. The dose was then recalculated for each fraction using the recorded MLC positions. Each fraction was then compared to the original treatment plan using 3D gamma analysis of the entire volume, gamma analysis of each ROI and dosimetric statistics for the PTV and OARs. The standard deviation of these parameters over the course of treatment was then compared between treatment sites.
Results: Head and Neck treatments had the highest standard deviation per fraction of PTV dose with a D2 std of 1.1cGy and a D98 std of 1.9cGy. IMRT brain treatments had a standard deviation per fraction of PTV dose for D2 std of 0.8cGy and a D98 std of 0.4cGy. IMRT prostate treatments had a standard deviation per fraction of PTV dose for D2 std of 0.88cGy and a D98 std of 0.82cGy. The overall maximum dose varied by 1.63cGy, 0.73cGy and 0.91cGy for HN, Brain and prostate treatments respectively.
Conclusion: IMRT Head and Neck treatments had a significantly larger variation of PTV and plan maximum dose than either IMRT Brain or IMRT Prostate treatments.
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