Deterministic Modeling of Carbon-Ion Dose and LET Distributions for a Preclinical Carbon-Ion Radiation Therapy (CIRT) Experimental Platform
Abstract
Purpose
The purpose of this study was to characterize carbon-ion radiation transport and energy deposition for the Brookhaven National Laboratory (BNL) experimental platform using deterministic TRiP98 (GSI heavy-ion treatment planning system) simulations in water. Accurate modeling of physical dose and linear energy transfer (LET) distributions is essential for assigning reliable dose–LET values to biological endpoints in preclinical carbon-ion radiation therapy (CIRT) experiments.
Methods
TRiP98 was used to simulate both monoenergetic and spread-out Bragg peak (SOBP) configurations of a 128 MeV/nucleon carbon-12 beam in a water-equivalent phantom. A synthetic water CT was generated to serve as the target geometry, and forward-planned fluence files were constructed to reproduce the physical modulation of the BNL range modulation wheel. Central-axis depth–dose and dose-mean LET (LETd) distributions were computed for both beam configurations. Voxelwise output was post-processed to extract one-dimensional depth profiles and two-dimensional lateral dose and LET maps for analysis.
Results
The TRiP98 simulations reproduced the expected physical characteristics of carbon-ion beams in water. The SOBP configuration exhibited a uniform dose plateau across the modulation width with a gradual entrance buildup and a sharp distal fall-off, confirming appropriate weighting of the range-modulated energy layers. In contrast, the monoenergetic beam produced a narrow, sharply peaked Bragg maximum with minimal distal dose. LETd increased monotonically with depth for both configurations, with pronounced maxima near the distal edge of the SOBP and at the Bragg peak of the monoenergetic beam. Lateral LETd distributions demonstrated a narrow high-LET core along the beam axis with minimal lateral broadening.
Conclusion
These results demonstrate that TRiP98 can model carbon-ion dose and LET distributions relevant for the BNL experimental platform in water. The framework establishes a baseline for the assignment of dose-LET values for subsequent preclinical CIRT experiments.