Filmless methods for quality assurance of Tomotherapy using ArcCHECK

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Tomotherapy utilizes synchronized gantry rotation, multileaf collimator (MLC), and couch movement for intensity-modulated radiation therapy (IMRT).
• The dynamic nature of Tomotherapy necessitates robust quality assurance (QA) protocols.
• Accurate QA is crucial for ensuring treatment efficacy and patient safety.

Purpose of the Study:

• To develop and validate methodologies for precise QA measurements on Tomotherapy units using an ArcCHECK device.
• To assess gantry angle and speed, MLC synchronization and leaf open time.
• To evaluate couch translation, speed, uniformity, and constancy of the longitudinal beam profile.

Main Methods:

• Utilized AAPM TG148 and manufacturer-recommended test plans, including helical and static star shot tests.
• Employed ArcCHECK's high-speed data acquisition and virtual inclinometer for gantry and MLC measurements.
• Developed in-house MATLAB programs to analyze ArcCHECK and machine log data for couch and beam profile analysis.

Main Results:

• Gantry angle deviation was less than 0.4°, and leaf open time differences were within 0.5%.
• MLC synchronization showed high mean values (e.g., 0.995 at 135°).
• Couch translation and speed measurements exhibited less than 0.1% deviation, with couch speed uniformity better than 1%.

Conclusions:

• Developed accurate and efficient methods for Tomotherapy QA using ArcCHECK.
• Validated methodologies against machine log data, demonstrating high precision.
• Confirmed the capability to precisely measure critical parameters like MLC leaf open time and synchronization.