Monte Carlo dosimetry for a new ³²P brachytherapy source using FLUKA code

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Brachytherapy utilizes sealed radioactive sources for localized radiation treatment.
• Accurate dosimetric characterization of brachytherapy sources is crucial for effective and safe treatment planning.

Purpose of the Study:

• To perform a comprehensive dosimetric characterization of a novel 32P brachytherapy source.
• To validate the FLUKA Monte Carlo code for simulating dosimetric parameters.
• To investigate dose rate distributions around sheathed and unsheathed 32P sources in various tissue phantoms.

Main Methods:

• Modeling of the 32P source using FLUKA Monte Carlo code.
• Calculation of absorbed dose rate, radial dose function, anisotropy function, and away-along tables per AAPM TG-60 guidelines in a water phantom.
• Evaluation of dose rate distributions in liver, fat, 9-component soft tissue, and 4-component soft tissue phantoms for both sheathed and unsheathed sources.

Main Results:

• FLUKA code accurately reproduced dosimetric parameters for the 32P source in water, showing good agreement with GEANT4 simulations.
• The presence of a catheter (sheathed source) increased dose values by up to 2.11% compared to the unsheathed source in water.
• Radial dose functions calculated in water differed significantly from those in tissue phantoms, particularly at larger distances.

Conclusions:

• FLUKA code provides a reliable method for characterizing dosimetric parameters of 32P brachytherapy sources.
• Dose distributions vary between water and tissue phantoms due to differences in density and atomic composition, which are not fully addressed by current formalisms like AAPM TG-60.