KEY POINTS
- This in silico dosimetric study used TOPAS Monte Carlo simulations in water to evaluate proton minibeam radiation therapy across proton energies of 50–230 MeV, beam widths of 0.5–2.0 mm, and center-to-center distances of 3–5 beam widths.
- Optimal settings were selected using three dose-based criteria: minimising beam width in normal tissue, maximising valley dose in the target, and minimising peak dose in normal tissue.
- For shallow targets of 2 cm or less, 0.5 mm beams with center-to-center distance equal to 3 beam widths kept normal-tissue beam widths below 1 mm and maintained a Bragg-peak-to-entrance dose ratio above 1, but did not achieve target homogeneity with a single array.
- For intermediate and deep targets of 8–20 cm, 1.0–1.5 mm beams with center-to-center distance equal to 4–5 beam widths kept normal-tissue widths below 7 mm, maintained peak-to-valley dose ratio above 3, and achieved lateral dose homogeneity in the target.
- For very deep targets beyond 20 cm, 2 mm beams with center-to-center distance equal to 4 beam widths maintained normal-tissue widths below 10 mm and peak-to-valley dose ratio above 3, but at the cost of a Bragg-peak-to-entrance dose ratio of approximately 0.5.
CLINICAL TAKEAWAY
This study provides a useful dosimetric map for selecting proton minibeam parameters by target depth and may help design early-phase clinical trials. However, the work was performed in homogeneous water phantoms without patient anatomy, tissue heterogeneity, relative biological effectiveness modelling, or clinical outcome validation, so it should be treated as technical groundwork rather than evidence of clinical benefit.