Enhanced efficiency in helical tomotherapy quality assurance using a custom-designed water-equivalent phantom

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• TomoTherapy is an advanced image-guided, intensity-modulated radiation therapy (IMRT) system.
• It enables precise helical dose delivery and megavoltage computed tomography (MVCT) for target localization.
• Current quality assurance (QA) for TomoTherapy is time-consuming.

Purpose of the Study:

• To develop and evaluate a custom-designed phantom to improve the efficiency of daily TomoTherapy QA.
• To reduce the time required for essential QA procedures.
• To ensure the accuracy and reliability of the TomoTherapy system.

Main Methods:

• Fabrication of a custom phantom with ionization chamber ports, density plugs, and film cartridges.
• Development of a streamlined QA protocol utilizing the phantom.
• Verification of static beam quality, output, image quality, image registration accuracy, and helical dose delivery energy.
• Simultaneous evaluation of machine output, percent depth dose, and off-axis factors using a static field.
• Assessment of image quality and registration accuracy via a single phantom scan.

Main Results:

• The custom phantom and QA procedure reduced daily QA time to under 30 minutes.
• The QA process effectively verified static beam characteristics, image quality, and registration accuracy.
• The phantom also proved useful for patient plan-specific QA.
• Six months of QA data demonstrated the process's reliability.

Conclusions:

• The custom phantom significantly enhances the efficiency of TomoTherapy daily QA.
• The developed QA procedure is simple, efficient, and verifies multiple critical parameters simultaneously.
• This improved QA approach contributes to the reliable and accurate delivery of radiation therapy.