An absorbed dose-based source strength determination for diffusing alpha-emitters radiation therapy (DaRT)...

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Diffusing alpha-emitter radiation therapy (DaRT) uses ²²⁴Ra seeds for brachytherapy.
• Current source strength determination via gamma spectrometry is limited.
• It fails to account for progeny desorption and construction variations impacting dose.

Purpose of the Study:

• Investigate ²²⁴Ra distribution depth impact on progeny desorption and absorbed dose.
• Propose an absorbed dose-based source strength specification.
• Assess the sensitivity of the proposed standard to desorption variations.

Main Methods:

• Monte Carlo (MC) simulations and diffusion-leakage (DL) model used.
• Varying ²²⁴Ra distribution depths (0-14 nm) modeled.
• Desorption probabilities calculated and used in DL model for dose calculation.

Main Results:

• Progeny desorption highly sensitive to ²²⁴Ra depth; sharp reduction with increased depth.
• Absorbed dose varied up to 80% with desorption probabilities.
• Proposed absorbed dose standard showed high sensitivity to seed construction changes.

Conclusions:

• Significant dependence of absorbed dose on ²²⁴Ra progeny desorption confirmed.
• An absorbed dose-based source strength specification proposed.
• MC methods validated the proposed instrument's suitability for accurate measurements.