Various wedge isodose angles for treatment planning.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Wedge filters are crucial for shaping dose distributions in radiotherapy.
• Generating specific wedge angles can be challenging with traditional methods.
• Digital techniques offer potential for precise dose modulation.

Purpose of the Study:

• To investigate the creation of various wedge angles using digital combination of isodose distributions.
• To analyze the relationship between weighting factors and generated wedge angles for an 8-MV photon beam.
• To develop empirical equations for predicting wedge angles based on weighting parameters.

Main Methods:

• Combining isodose distributions from a single physical wedge and an open field.
• Applying different weights to the isodose distributions.
• Analyzing the generated wedge angles at 10 cm depth and using the 50% isodose curve.
• Fitting the experimental data using two proposed empirical equations.

Main Results:

• Various wedge angles, including those smaller than the nominal angle, were successfully generated.
• A nonlinear relationship was observed between the imposed weights and the resulting wedge angle.
• The difference in wedge angles defined at 10 cm depth and by the 50% isodose curve was less than 6 degrees.

Conclusions:

• Digital combination of isodose distributions provides a flexible method for generating custom wedge angles.
• The nonlinear weighting relationship requires careful consideration for accurate dose planning.
• The developed empirical equations can aid in predicting and achieving desired wedge angles in clinical practice.