A novel angular dependency model for MatriXX response and its application to true composite dose verification for...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Accurate dose verification is crucial for intensity-modulated radiation therapy (IMRT).
• The MatriXX detector's response can be affected by beam angle, complicating dose verification.
• Patient-specific quality assurance (QA) for IMRT requires reliable and efficient verification methods.

Purpose of the Study:

• To propose and validate a model for the angular dependency of the MatriXX detector response.
• To assess the applicability of the MatriXX detector, using an angular-model-based approach, for true composite dose verification of IMRT plans.
• To compare the performance of the MatriXX detector with and without the angular-model-based correction against Gafchromic films.

Main Methods:

• Developed a model attributing MatriXX angular dependence to the translation of its effective measurement plane.
• Performed true composite dose verifications for AAPM TG 119 IMRT plans using MatriXX and Gafchromic EBT3 films.
• Evaluated dose verification accuracy using gamma passing rates (3%/3 mm and 3%/2 mm) and statistical analysis.

Main Results:

• MatriXX with the angular-model-based approach achieved >98.3% gamma passing rates (3%/3 mm) and >98.1% (3%/2 mm).
• Uncorrected MatriXX showed significantly lower gamma passing rates compared to films.
• No statistical difference was found between MatriXX with angular correction and film-based dose verification results.

Conclusions:

• The proposed model effectively addresses the angular dependency of the MatriXX detector.
• The angular-model-based approach enables acceptable and accurate dose verification for composite beam IMRT plans.
• This method simplifies patient-specific QA for IMRT, enhancing efficiency and reliability.