Angular dose dependence of Matrixx TM and its calibration

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• MatriXX detectors are used for experimental dose verification in IMRT, VMAT, and tomotherapy.
• Standard manufacturer calibration does not account for the angular dependency of the MatriXX detector.
• This angular dependency can lead to dose bias in cumulative plan verification.

Purpose of the Study:

• To characterize the angular dependency of MatriXX detectors.
• To develop a novel calibration method to correct for angular dependency.
• To evaluate the effectiveness of the new calibration method in IMRT and VMAT plan verification.

Main Methods:

• Characterized angular dependency of four MatriXX (Evolution series) detectors.
• Investigated detector response across various gantry angles, focusing on specific ranges (91-110 and 269-260 degrees).
• Developed and applied a new calibration method to mitigate angular response variations.

Main Results:

• Observed significant discrepancies (up to 11%) in detector response between posterior and anterior fields.
• Identified substantial variability in detector response as a function of gantry angle.
• The developed calibration method effectively eliminated dose bias caused by angular dependency.

Conclusions:

• MatriXX detectors exhibit significant angular dependency, impacting dose verification accuracy.
• The novel calibration method successfully corrects for angular dependency.
• This method enhances the reliability of experimental dose verification for IMRT and VMAT.