Room: AAPM ePoster Library
To develop Monte Carlo (MC)-based plan optimization for intensity modulated proton therapy (IMPT) and to compare the resulting spot scanning proton plans to MC re-calculated plans generated in a commercial treatment planning system (TPS).
The Eclipse TPS is used to generate a three field IMPT plan for the ProBeam?? spot scanning system (Varian Medical Systems) for a clinically motivated head and neck case. The same spot candidates are used to generate a MC-based in-house IMPT plan using a framework to calculate dose distributions of the individual spots with the proton Macro Monte Carlo (pMMC) algorithm. Fluence map optimization of spot weights is performed using a quasi-Newton L-BFGS algorithm with dose volume objectives set on the target volume and organs at risk. The in-house IMPT plan is compared to the MC re-calculated proton plan created in the commercial TPS by means of dose differences and dosimetric parameters.
Compared to the MC re-calculation of the TPS plan, the in-house optimized plan shows a more conformal dose distribution to the target volume with dose difference in the normal tissue up to -30% (-20 Gy). PTV homogeneity is improved and dose to organs at risk such as inner ear and lacrimal gland is substantially reduced (mean dose -4.2 Gy and -2.5 Gy, respectively) with the in-house IMPT plan compared to the TPS plan.
An MC-based in-house framework to generate IMPT plans was successfully developed. MC-based optimization shows dosimetric advantages for conformity, target homogeneity and organ at risk sparing.
Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by Varian Medical Systems.