Commissioning and clinical implementation of Monaco treatment planning system on a compact pencil beam scanning...

Treatment planning system (TPS) requires comprehensive commissioning and validation prior to clinical use to ensure accurate dose calculation and safe clinical implementation.

To enable clinical use of the Monaco proton TPS, we commissioned it on a single-room compact proton therapy system and implemented a clinically integrated workflow using daily synthetic CT (sCT) to track fractional dose delivery.

The Monte Carlo (MC) dose calculation algorithm in Monaco TPS (version 6.1) was commissioned on an IBA Proteus ONE system. Commissioning included data acquisition, beam modeling, and model validation. Data included in-air spot profiles for 70-227 MeV at five planes (+20 cm and +10 cm upstream, isocenter, -10 cm and -20 cm downstream), integral depth-dose curves in water, and absolute monitor unit calibration. Model validation comprised: percent depth-dose in water for monoenergetic beams using a 10 × 10 cm² field across energies; output checks with standard cube plans mimicking diverse treatment sites and target volumes; and independent end-to-end testing with an IROC brain phantom. Clinically, a patient with basal cell carcinoma of the skin was treated with a two-field IMPT plan delivering 60 Gy in 30 fractions. Probability-based robust optimization required 100% target coverage under 3 mm setup and 3.5% range uncertainties. An in-house sCT generated from daily CBCT images was used to evaluate dose delivery accuracy throughout treatment.

Distal range (R90, R80, R20) differences between Monaco and measurement were within 1 mm for 70-227.7 MeV. Output differences for all standard cube plans were within 3%. For the IROC brain phantom, the TLD-to-Monaco MC dose ratio was 1.00, with gamma passing rates of 94% (coronal) and 98% (sagittal). sCT-based evaluation showed 99% CTV receiving ≥98% of the prescribed dose across the course.

Monaco's proton MC beam model and dose calculation algorithm were commissioned and validated on IBA Proteus ONE for clinical use. The first patient (November, 2024) was successfully treated, with daily dose delivery accuracy monitored via an in-house sCT platform.