Angular correction in reconstruction of electron spectra from depth dose distributions

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Current methods for reconstructing electron spectra from depth-dose data often neglect the angular distribution of incident electrons.
• This approximation is valid for electrons with small angular spread but introduces errors for scattered electrons with larger incidence angles.
• Scattered electrons significantly impact dose distribution in shallow depths, increasing surface energy deposition.

Purpose of the Study:

• To investigate the systematic errors in reconstructed electron spectra caused by ignoring incident electron angular distribution.
• To develop a simple model for correcting these errors and improving spectral reconstruction accuracy.
• To validate the proposed model against established simulation techniques.

Main Methods:

• Utilized a database of monoenergetic depth-dose curves generated for normal electron incidence.
• Analyzed the impact of large average angles of incidence due to scattering from treatment head and collimating systems.
• Developed and applied a 1-D model incorporating electron angular distribution at the central beam axis.

Main Results:

• Ignoring electron incident angular distribution leads to systematic errors in the low-energy region of reconstructed electron spectra.
• The proposed 1-D model effectively corrects these systematic errors.
• Reconstructed electron spectra using the model show excellent agreement with Monte Carlo simulations in the low-energy range.

Conclusions:

• Accurate reconstruction of electron spectra requires consideration of incident electron angular distribution.
• The developed 1-D model offers a significant improvement for spectral reconstruction, particularly at low energies.
• This correction enhances the reliability of electron beam dosimetry in radiation therapy.