Evaluating Monaco 6.2.2 in complex radiotherapy across matched LINACs: improved MLC modelling and dose accuracy with...

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• The Monaco Treatment Planning System (TPS) utilizes virtual source models (VSMs) for accurate dose calculation.
• Previous VSM versions required extensive characterization of multileaf collimator (MLC) and jaw parameters.
• Stereotactic radiotherapy (SRT) demands high precision in dose delivery, necessitating accurate beam modeling.

Purpose of the Study:

• To evaluate the updated Monaco TPS VSM 2.0, which simplifies beam modeling by removing editable MLC and jaw parameters.
• To assess the impact of VSM 2.0 on dosimetric accuracy for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) cases.
• To compare VSM 2.0 performance against a validated custom VSM 1.6 and Elekta's Accelerated Go Live 6 MV FFF beam model.

Main Methods:

• VSM 2.0 was implemented and evaluated on two beam-matched linear accelerators (LINACs).
• MLC characteristics were measured using a high-resolution detector.
• Output factors (OPF), ion chamber measurements in a thorax phantom, and recalculations of clinical SRT cases were performed.
• Gamma analysis was used to compare dose distributions between VSM 2.0 and previous models.

Main Results:

• VSM 2.0 demonstrated improved MLC modeling capabilities.
• Ion chamber measurements met IAEA TD1583 tolerances.
• Gamma pass rates (1%, 1 mm) showed improvement for SRS and SBRT treatments on matched LINACs.
• VSM 2.0 offers enhanced agility in MLC modeling and simplifies commissioning workflows.

Conclusions:

• VSM 2.0 represents a significant advancement in Monte Carlo-based TPS beam modeling.
• The updated model provides improved dosimetric accuracy and operational simplicity for SRT and SBRT.
• VSM 2.0 facilitates more consistent and high-quality beam models, enhancing treatment delivery precision.