Applying a polynomial formula to photon beam output and equivalent square field

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Accurate calculation of radiation beam output is crucial for effective radiotherapy.
• Existing methods for calculating electron beam output and equivalent squares have limitations.

Purpose of the Study:

• To evaluate Chen's polynomial formula for calculating photon and electron beam output factors.
• To derive and analyze an equation for equivalent square field size based on Chen's formula.

Main Methods:

• Applied Chen's polynomial formula to calculate output factors for various linear accelerators (100 kVp to 18 MeV).
• Derived an equation for equivalent square field size from the polynomial formula.
• Compared calculated outputs with measured values.

Main Results:

• Calculated outputs using Chen's formula were within 1% of measured values.
• The derived equivalent square equation shows dependence on formula parameters, photon energy, medium, and collimator design, not just field dimensions.

Conclusions:

• Chen's formula provides accurate electron and photon beam output factors for therapeutic units.
• The derived equivalent square equation offers a more precise method than traditional approximations.