Multiple energy extraction reduces beam delivery time for a synchrotron-based proton spot-scanning system

Area of Science:

• Medical Physics
• Radiation Oncology
• Accelerator Physics

Background:

• Multiple energy extraction (MEE) is an advanced Hitachi technology for spot-scanning proton therapy systems.
• MEE enables the delivery of various proton beam energies within a single synchrotron cycle.
• This contrasts with single energy extraction (SEE), where each energy requires a separate cycle.

Purpose of the Study:

• To quantify the potential reduction in beam delivery time (BDT) using MEE compared to SEE.
• To evaluate the impact of MEE on treatment delivery efficiency in proton therapy.

Main Methods:

• A predictive model based on synchrotron delivery performance was employed to calculate BDT.
• Total BDT was computed for 2694 patient deliveries under both SEE and MEE (9 energy layers) configurations.
• BDT reduction was also assessed for hypothetical accelerators with enhanced charge capacity.

Main Results:

• A 4-energy layer MEE configuration reduced total BDT by an average of 35% (41 seconds) versus SEE.
• Individual fields demonstrated up to 65% BDT reduction.
• Improvements in charge recapture efficiency increased BDT savings, reaching up to 42% of SEE BDT.

Conclusions:

• The MEE technique achieved a substantial 35% reduction in total BDT.
• Further BDT reduction necessitates increasing charge per spill and charge recapture efficiency.
• Optimizing these parameters will maximize the benefits of MEE for treatment efficiency and throughput.