(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To evaluate auto planning for prostate SBRT using an in-house script versus a vendor provided tool.
Methods: Ten previously treated prostate SBRT patients were selected. We used heterogeneous planning to give 36.25 Gy in five fractions to the PTV and escalate dose to 40 Gy in regions not adjacent to risk organs. Four treatment plans were made per patient – two (one using 6FFF and one using 10FFF) using an in-house script-based planning tool (SCRIPT) and another two using the vendor provided auto planning tool in Pinnacle (AUTO). We evaluated various dose volume parameters for bladder, urethra, and rectum. For PTV, the Paddick conformity index (CI), gradient index (GI), and low dose spread (LDS, the ratio of 25% prescription isodose volume to the PTV volume) were compared among four plans for each patient. To evaluate the delivery efficiency, total monitor units (MU) and beam-on time were also compared.
Results: The AUTO plans achieved lower V(39Gy) of urethra compared to the SCRIPT plans: 0.2 cc vs 0.9 cc for 6 FFF and 0.1 cc vs 0.5 cc for 10 FFF (p < 0.05), respectively. Comparing the 6FFF and 10FFF plans, LDS was lower for 10 FFF (19.1 vs 16.4 for SCRIPT plans and 18.1 vs 16.1 for AUTO plans; p < 0.05). For all the other parameters measured, the differences between the four plans were not statistically significant. The delivery time for 10FFF plans was significantly less than 6FFF (p < 0.05). Planning time for SCRIPT was 14 minutes vs. 36 minutes for AUTO.
Conclusion: The resultant plans were all clinically acceptable. Plan quality was comparable among all plan types. However, delivery time and low dose spread to peripheral normal tissue was lower with 10FFF beams. Planning time for SCRIPT plans was faster than that of plans created using AUTO.
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