Evaluation of a 3D diode array dosimeter for helical tomotherapy delivery QA

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Helical tomotherapy requires precise quality assurance (QA) for accurate dose delivery.
• Diode array dosimeters are essential tools for verifying treatment plans.
• The Delta4 biplanar diode array is a novel system for 3D dose measurements.

Purpose of the Study:

• To validate the Delta4 biplanar diode array dosimeter for helical tomotherapy delivery QA.
• To assess the detector's characteristics and accuracy in a clinical setting.

Main Methods:

• The Delta4 dosimeter's characteristics (reproducibility, linearity, dose rate dependence, absolute calibration) were evaluated.
• Relative calibration was verified using film and detector rotation.
• Clinical plans were assessed using the gamma index (γ(3%, 3 mm)) passing rate.

Main Results:

• The Delta4 dosimeter exhibited satisfactory characteristics: short-term reproducibility (0.1%), linearity (<0.1%), dose rate dependence (0.4%), and absolute calibration accuracy (0.4%).
• Rotational irradiation response changed by ≤0.2%.
• The γ(3%, 3 mm) passing rate for clinical plans was high, averaging 97 ± 2.7%, with >90% passing for all plans.

Conclusions:

• The Delta4 biplanar diode array is a suitable and accurate dosimeter for helical tomotherapy QA.
• Careful phantom alignment, potentially using megavoltage computed tomography, is recommended for optimal results.