A diffusion-leakage model coupled with dose point kernels (DPK) for dosimetry of diffusing alpha-emitters radiation...

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Diffusing Alpha-Emitters Radiation Therapy (DaRT) is a novel brachytherapy utilizing ²²⁴Ra progeny diffusion for targeted cell killing via alpha particles.
• Current DaRT dose calculation models, based on diffusion-leakage (DL), often neglect the contribution of beta particle radiation.
• Accurate absorbed dose calculation is crucial for optimizing DaRT treatment efficacy and patient outcomes.

Purpose of the Study:

• To develop an enhanced absorbed dose calculation method for DaRT by integrating dose point kernels (DPKs) into the existing DL model.
• To account for the dose contribution from beta particles emitted by ²²⁴Ra progeny.
• To incorporate the non-local energy deposition characteristics of beta particles in dose calculations.

Main Methods:

• Modeled the DaRT source using COMSOL Multiphysics and implemented the DL model to determine progeny spatial distribution.
• Generated DPKs for dominant beta emitters (²¹²Pb, ²¹²Bi) in the ²²⁴Ra decay chain using Monte Carlo methods.
• Convolved progeny number densities with DPKs to compute total absorbed dose over a 30-day period, considering both high and low diffusion scenarios.

Main Results:

• Calculated DPKs demonstrated significant energy deposition extending several millimeters from the source.
• The integrated dose calculation showed >10 Gy within 1.8 mm (low diffusion) and 2.2 mm (high diffusion) radial distances.
• Significant dose differences (>1 Gy) were observed compared to alpha-only local energy deposition methods within 1.3-1.8 mm radial distances.

Conclusions:

• The proposed method, coupling DL models with DPKs, accurately calculates absorbed dose for DaRT by including beta particle contributions.
• This enhanced dosimetry improves the precision of dose delivery in DaRT, potentially leading to better tumor control.
• The findings highlight the importance of considering non-local energy deposition and beta dose in advanced brachytherapy techniques.