Enhanced dynamic wedge output factors for Varian 2300CD and the case for a reference database

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• Physical wedges are used in radiation therapy to compensate for dose inhomogeneity.
• Enhanced dynamic wedges (EDW) were developed by Varian to address limitations of physical wedges.
• Accurate output factors are crucial for reliable treatment planning and dose delivery.

Purpose of the Study:

• To measure Enhanced Dynamic Wedge (EDW) output factors for 6 MV and 20 MV photon energies on a Varian 2300CD linear accelerator.
• To compile and compare measured EDW output factors with published data for various Varian linear accelerator models.
• To assess the validity and consistency of reference databases for EDW output factors.

Main Methods:

• Experimental measurement of EDW output factors (EDWOF) using a Varian 2300CD at 6 MV and 20 MV.
• Systematic literature review to identify published EDWOF data for different Varian linear accelerator models.
• Statistical comparison of measured data against compiled literature values, including mean differences and coefficients of variation.

Main Results:

• Excellent agreement was observed between measured and published 6 MV EDWOF, with percentage differences from 0.01% to 0.57% (mean 0.03%).
• Published EDWOF showed coefficients of variation ranging from 0.17% to 0.85% (6 MV) and 0.1% to 0.9% (18 MV).
• This study presents the first published EDWOF for 20 MV and a comprehensive compendium for various Varian models.

Conclusions:

• Measured EDWOF values demonstrate high consistency across different Varian linear accelerator models and institutions.
• The findings support the validity of reference databases and the potential for establishing standard datasets for dosimetry.
• This work provides crucial data for future commissioning, beam modeling, and quality assurance in radiation therapy.