SU-E-T-535: Proton Dose Calculations in Homogeneous Media

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Proton therapy offers precise dose delivery, but accurate dose calculation algorithms are crucial for optimal treatment planning.
• Existing pencil beam algorithms (PBA) often have limitations in modeling scatter events, impacting dose distribution accuracy.
• Improving the modeling of elastic and nonelastic scatter is essential for enhancing the precision of proton dose calculations.

Purpose of the Study:

• To develop an advanced pencil beam dose calculation algorithm for scanned proton beams.
• The primary goal is to improve the modeling of scatter events, particularly nonelastic scatter, for greater accuracy.
• Enhance the prediction of the lateral dose profile through the Bragg peak.

Main Methods:

• Developed a pencil beam algorithm (PBA) using Fermi-Eyges theory for proton transport in homogeneous media.
• Modeled elastic and nonelastic scatter effects using Gaussian distributions with parameters derived from theoretical calculations and Monte Carlo (MC) simulations.
• Validated the PBA against MC simulations in a water phantom, assessing agreement using penumbral width differences and percentage of points within 2% dose difference or 1mm distance to agreement.

Main Results:

• The developed PBA demonstrated an order of magnitude improvement in agreement for calculated versus simulated penumbral widths compared to previous models.
• Achieved over 99% agreement between PBA and MC calculations for dose distributions involving oblique beams and surface irregularities.
• The algorithm accurately predicted the lateral profile shape through the Bragg peak.

Conclusions:

• The enhanced PBA, incorporating nonelastic scatter, shows superior accuracy in predicting proton beam dose distributions compared to existing models.
• The improved accuracy of this algorithm can enhance the reliability of treatment planning for scanned proton therapy.
• This advancement holds potential for improving patient treatment outcomes in proton therapy.