Wedge filter effects on dosimetric parameters of a linear accelerator

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Wedge filters are crucial in radiation therapy for shaping dose distributions.
• Understanding their impact on dosimetric parameters is essential for accurate treatment planning.

Purpose of the Study:

• To measure and compare open-field and wedged-field output factors for two different linear accelerators.
• To investigate the variability of wedge factors with field size and their effect on other dosimetric parameters.

Main Methods:

• Measured output factors as a function of field size for open and wedged fields on two linear accelerators.
• Determined wedge factors by calculating the ratio of output with and without the wedge filter.
• Analyzed variations in output factors and wedge factors across different field sizes and wedge angles.

Main Results:

• One linear accelerator exhibited output factor differences up to 5% between wedged and open fields, with wedge factors varying by field size.
• The second linear accelerator showed less than 1% variation in output factors and wedge factors (for a 60-degree wedge) across field sizes.
• Wedge filters were confirmed to alter isodose distributions, percent depth dose curves, output factors, and wedge factors.

Conclusions:

• The impact of wedge filters on dosimetric parameters varies significantly between different linear accelerators.
• Accurate characterization of wedge effects is critical for ensuring precise radiation delivery and patient safety.