First experience with third-party validations: A robust calibration and QA procedure for proton FLASH delivery.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Proton FLASH radiotherapy offers reduced normal tissue toxicity and maintained tumor control due to ultra-high dose rates.
• Accurate dosimetry and quality assurance (QA) for FLASH are challenging due to extreme dose rates.
• Reliable calibration and QA procedures are essential for clinical advancement of FLASH therapy.

Purpose of the Study:

• To introduce an effective routine calibration and QA procedure for proton FLASH delivery.
• To ensure high-quality dosimetry performance for both preclinical and clinical applications.
• To address the challenges in accurate dosimetry for ultra-high dose rate proton therapy.

Main Methods:

• A strip ionization chamber array (SICA) detector was calibrated against an Advanced Markus ion chamber (IC) under variable and ultra-high dose rates.
• The SICA detector was used for real-time monitoring of proton FLASH deliveries.
• Third-party Imaging and Radiation Oncology Core (IROC) thermoluminescent dosimeters (TLDs) were used for independent verification.

Main Results:

• The calibration process was rapid, taking under 10 minutes for daily QA.
• The SICA detector showed excellent correlation (R-value ≈ 1.00) with the IC.
• Real-time monitoring by SICA provided critical delivery data, with planned and delivered doses within 1% accuracy verified by TLDs.

Conclusions:

• Effective calibration and QA using a SICA detector enable accurate real-time dose and dose rate monitoring for proton FLASH.
• The developed procedure ensures high accuracy, validated by independent IROC measurements.
• This approach facilitates the future clinical application of proton FLASH radiotherapy.