Wedge factors: dependence on depth and field size

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Accurate dose calculation in radiation therapy requires precise understanding of beam modifiers.
• Wedge factors (WF) are crucial for shaping dose distributions in tangential breast radiotherapy.
• Variations in WF with field size and depth can impact treatment accuracy.

Purpose of the Study:

• To analyze the variation of wedge factors (WF) with field size and depth for 6 and 15 MV X-ray beams.
• To quantify the impact of field size and depth on WF.
• To propose a correction method for WF depth dependence.

Main Methods:

• Measurements of WF were performed for varying field sizes and depths.
• Analysis of WF dependence on field size and depth was conducted for 6 and 15 MV X-ray beams.
• An empirical correction formula for WF depth dependence was developed.

Main Results:

• The maximum field size effect on WF was measured to be 1.4%.
• WF exhibited a linear dependence on depth, with a maximum variation of 0.22%/cm for a 60-degree wedge and 6 MV beam.
• The proposed empirical correction addresses WF depth dependence.

Conclusions:

• Field size and depth significantly influence wedge factor values.
• The characterized WF variations are essential for accurate dose calculations in radiotherapy planning.
• The proposed empirical correction can improve the accuracy of dose delivery in radiation therapy.