Purpose/Objective(s) To perform quality assurance (QA) of initial patient IMPT treatment plans and monitoring dose delivered of each fractional, a software, myQA Ion PT (myQA-ION) system was validated and evaluated using commissioning data and patient data. Materials/Methods In myQA-ION, the Monte Carlo (MC) dose engine was commissioned for the Proteus One (P1) proton system based on measured commissioning data, which was also used for commissioning of P1 in our treatment planning system (TPS). Single spots and 10x10cm2 single layers for 7 energies ranging from 70 to 226MeV. The spot sizes, R90 and distal falloff of the extracted PDDs of the 7 energies were compared to the measured commissioning data. The 3D Gamma values (down to 1%,1mm) were obtained to validate the myQA-ION system against TPS for these single spot and single layer plans. Patient IMPT plans from sites of brain, HN, thoracic, and pelvic were sent to myQA-ION for 3D gamma comparisons. Treatment delivery logs of each proton beam of these patients were also imported into the myQA-ION to calculate per beam fractional dose on patient simulation CTs. Gamma tests of the irradiated volumes, PTV, and OARs were also obtained. Results The myQA-ION P1 model calculated spot size, range, distal falloff, and field size of the single spot and square fields are in good agreement with the commissioning measurement data. The 3D gamma comparisons of single spot and energy layers showed minimum 97.7% for 1% and 1mm criteria (see Table) for 70MeV, which has sharpest dose fall off, thus was partially affected by 1mm dose grid resolutions of both TPS and myQA-ION. For patient plans, the global gamma (3%, 3mm) of irradiate volume has the values of 99.5% +/- 0.6%; gamma of PTV has the values of 99.9% +/- 0.12%; gamma of OARs has the values of 99.9% +/- 0.04%. For recalculated patient dose of treatment logs, the gamma of irradiated volume per beam has the values of 98.5% +/- 1.2%, the gamma values for PTV and OAR has the minimum values of 98.8% +/- 0.2%. The trend of gamma test of treatment log to TPS dose is consistent among different fractions. Conclusion The validation of myQA-ION system demonstrated high fidelity between its calculated spots and PDDs and the commissioning data and proved by their high gamma pass rate (1%,1mm criteria) of the 3D dose between TPS and myQA-ION. The independent myQA-ION calculated treatment plans and the treatment log-based dose verification provides safe and more efficient delivery based IMPT QA and per fraction dose auto monitoring.

Purpose/Objective(s)For proton therapy plans, switching proton machines without re-optimization can greatly improve the clinical efficiency, when proton machines belong to different platforms. This study focused on machine switching efficiency between Proteus-1 and Proteus-plus platforms by modeling a Proteus-1 proton machine with built-in range shifter (P1RS) for direct recalculation of treatment plans between P1 and universal nozzle of Proteus-plus (P+US) systems.Materials/MethodsFor institutions with multiple platform proton machines (i.e., P+ to P1), re-planning is usually required if a patient needs to be moved from P+ to P1 machines due to their different spot sizes. This usually requires re-planning of the patient and creates significant time delay when one machine is down or overloaded. We are proposing commissioning a P1 machine model use built-in range shifter (P1RS) with snout position fixed at 45cm upstream from isocenter. The in-air spot size and PDD of the P1RS are compared to those of the P+US. The P+ patient plans are recalculated using P1RS machine directly with both pencil beam and Monte Carlo dose engines.ResultsThe P1RS machine model has similar in-air spot size as those of P+US (see Table). There are noticeable differences between the PDDs of the two models. For patient plan with field size less than 20cm by 24cm, preliminary investigation of direct conversion of treatment plans between the two machine models indicates that it is feasible.ConclusionP1 model with a built-in range shifter can simulate a P+US system. Direct recalculation of treatment plan between the two systems is feasible with acceptable dosimetric differences and could increase machine switching capabilities and improve clinical flow efficiency.

P1 system with 45cm away from isocenter can effectively simulate a large spot PBS system, P+. Lung SABR IMPT plan qualities between the two systems were dosimetrically comparable. Volumetric dose-repainting were applicable to both systems to reduce interplay effect. However, the plan beam-on and delivery time of P1 system were significantly shorter than that of P+. Therefore, potential less patient movement during treatment leads to less dose uncertainties to patients.

These long-term results show that proton therapy can provide favorable biochemical control outcomes for patients with localized prostate cancer. Additional strategies are needed to improve disease control for patients with very high-risk disease. Late grade 3+ GI toxicity rates are low and, as noted with other radiation modalities, the rate of late grade 3+ GU toxicity increases with time even after 5 years. There was an expected decline in overall sexual function as the patient cohort aged following proton therapy. These long-term results establish benchmarks for future comparative trials.

With an understanding and mitigation of these root causes, the goals of patient-specific QA, specifically detecting actual deviation of beam delivery or identifying limitations of dose calculation algorithm in used treatment planning system, can be directly related to the failure of PBS-QA measurements.