Development of an interlaced-crossfiring geometry for proton grid therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Traditional grid therapy uses single photon beams.
• Proton beamlet grid therapy offers a new approach.

Purpose of the Study:

• Evaluate interlacing and crossfiring mm-wide proton beamlets for grid therapy.
• Achieve homogeneous target dose with high normal tissue heterogeneity.

Main Methods:

• Monte Carlo simulations (TOPAS) for dose profiles of proton beamlets (1-3 mm FWHM).
• Simulated grids of proton beamlets targeting a cubic volume in water.
• Optimized beamlet spacing for dose distribution.

Main Results:

• Smallest beams (1 mm) showed greatest width increase with depth.
• Interlaced-crossfiring achieved target dose coverage (σ < ±5%).
• Grid pattern maintained near target (valley-to-peak ratio < 0.5).
• Optimal beamlet spacing (7-8 mm) balanced homogeneity and sparing.

Conclusions:

• Proton beamlet grid therapy enables homogeneous target dose.
• Maintains dose distribution grid pattern in normal tissue near target.
• Expected to improve tumor control and normal tissue sparing in grid therapy.