Poster — Thur Eve — 17: Control point analysis comparison of three different treatment planning and delivery complexity levels using a commercial three dimensional diode array

Purpose: To use Control Point Analysis (Sun Nuclear Corporation, Melbourne, Florida, USA) to analyze and compare delivered VMAT plans for three different treatment planning complexity levels. Methods: Nineteen patients were chosen and fully anonymized for the purpose of this study. Ten SBRT, six H&N, one breast and two prostate VMAT plans were generated on Pinnacle3 and delivered on a Varian LINAC. The delivered dose was measured using ArcCHECK™. Each plan was analyzed using SNC Patient 6 and Control Point Analysis. Gamma passing percentage was used to assess the differences between the measured and planned dose distributions and to assess the role of various control point binning scenarios. Results: The prostate cases reported the highest gamma passing percentages for SNC Patient 6 (99.3%–99.5%,3%/3mm) and Control Point Analysis (99.1––99.3%,3%/3mm). The mean percentage of passing control point sectors for the prostate cases increased from 48.9±3.1% for individual control points to 69.5 ± 3.9% for 5 control points binned together to 100±0% for 10 control points binned together. Over all, there was a trend in the percentage of sectors passing gamma analysis increasing with the increase of the number of control points binned together in one sector for both passing criteria considered (48.9±3.1% for individual control points to 69.5±3.9% for 5 control points binned together in one sector to 100±0% for 10 control points binned together in one sector for the prostate). Conclusion: The delivery accuracy per control point depends on the MU/control point (SBRT) and the plan degree of modulation (H&N).