Helical tomotherapy quality assurance with ArcCHECK

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Helical tomotherapy requires precise quality assurance (QA) for safe and effective cancer treatment.
• Current QA procedures can be time-consuming and may not fully simulate clinical delivery conditions.

Purpose of the Study:

• To design and evaluate a novel, efficient QA procedure for helical tomotherapy.
• The procedure aims to measure multiple beam parameters in a single delivery, mimicking treatment conditions.

Main Methods:

• A customized QA procedure was developed and preprogrammed on the tomotherapy system.
• Dosimetry measurements utilized an ArcCHECK diode array and an A1SL ion chamber.
• Comparative measurements were performed against ion chambers in liquid/solid water, onboard detectors, and MapCHECK for 10 weeks.

Main Results:

• The new QA procedure demonstrated good agreement (within 1.3%) for beam output and cone ratio compared to routine QA.
• Beam energy measurements showed comparability (0.3%) to solid water, with minor deviations in symmetry (~2.5%) on some weeks.
• The ArcCHECK phantom proved suitable for helical tomotherapy QA when background collection is managed properly.

Conclusions:

• The proposed weekly QA procedure using ArcCHECK and a water phantom enhances efficiency in helical tomotherapy.
• ArcCHECK is a viable alternative for helical tomotherapy QA, improving the overall QA process.
• Proper background data collection is crucial for accurate ArcCHECK phantom measurements.