Simplified estimation method for dose distributions around field junctions in proton craniospinal irradiation

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Craniospinal irradiation (CSI) requires multiple therapeutic beams due to large target volumes.
• Ensuring dose uniformity at the junctions of these beams is critical for effective radiotherapy.
• Proton therapy offers potential advantages but requires precise dose calculations at field junctions.

Purpose of the Study:

• To develop and validate a simplified model for estimating dose uniformity in proton CSI field junctions.
• To assess the accuracy of the model in predicting dose distributions and the impact of setup variations.
• To provide a practical tool for optimizing proton CSI treatment planning.

Main Methods:

• Developed a simplified field-junction model approximating lateral dose distributions with the error function.
• Measured lateral dose distributions of proton beams using a 2D ionization chamber array.
• Compared model-estimated dose profiles with experimental measurements from CSI-simulated irradiation.

Main Results:

• Model estimations of dose profiles around field junctions showed good agreement with 2D ionization chamber array measurements.
• The simplified model successfully predicted dose distributions and the effect of setup position gaps on dose uniformity.
• Despite limitations of the measurement array (partial volume effect), the model's consistency with measurements was notable.

Conclusions:

• The simplified field-junction model is a viable method for estimating dose uniformity in proton CSI.
• This model can aid in understanding and optimizing dose delivery at beam junctions, crucial for CSI treatments.
• The approach facilitates the evaluation of setup uncertainties and their impact on dose uniformity, enhancing treatment precision.