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Knowledge-Based RapidPlan Model for Prostate SBRT with and Without Lymph Nodes

O Apaza*, F Munoz , M Almada , A Alarcon , P Castro Pena , C Venencia , Instituto Zunino, Cordoba - ARGENTINA


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: The use of Knowledge-Based Planning (KBP) in radiotherapy it is becoming increasingly common. The objective of this work was to create and validate a KBP RapidPlan model for prostate SBRT with and without lymph nodes.

Methods: Forty SBRT prostate patients’ clinical plans (CP) with a total dose of 36.25Gy/5 fractions and a second group of 40 SBRT prostate/lymph node CP with a total dose of 40Gy/25Gy/ 5 fractions were selected. OARs and PTVs structures and constraints were added to the Model Structure and Objectives. Dosimetric and geometric data were extracted from the selected patient plans and added to the DVH estimation model. Two KBP models were generated (Model1: SBRT prostate and Model2: prostate/lymph node) and verified using RapidPlan of Eclipse v15.1 (Varian). The quality of the models was evaluated using R² and �² value. The models were validated for 10 patients in each SBRT protocol, comparing the RapidPlan with the CP for PTVs, rectum and bladder.

Results: During the verification process some structures were excluded if it did not well represent the model estimation using in field DVH plots. For Model1 the R²>0.46 and X² <1.61 and for Model2 R²>0.41 and X²<1.3. For Model1 the differences between RapidPlan and CP was: PTV_High_3625, 0.19±0.10 [Gy] for D98% and 0.77±0.92 [Gy] for D2%; bladder, maximum difference (MD) 0.82±0.63 [%] for V18Gy; rectum, MD 2.33±1.5[%] for V18Gy. For Model2 the results were: PTV_High_4000, 0.55±0.36 [Gy] for D98% and 1.83±1.14 [Gy] for D2%; PTV_Low_2500, 0.40±0.25 [Gy] for D98%; bladder, MD 12.55±9.42 [cc] for V25Gy; rectum MD 3.09±2.63 [%] for V20Gy.

Conclusion: We successfully implemented two models with RapidPlan for prostate SBRT with and without lymph nodes. Small adjustments are required in the optimization process to achieve clinical protocol restrictions and obtain high quality plans. More plans are required to improve statistics.


Not Applicable / None Entered.


TH- External beam- photons: treatment planning/virtual clinical studies

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