Calculation of electron dose to target cells in a complex environment by Monte Carlo code "CELLDOSE"

Area of Science:

• Medical physics
• Radiological sciences
• Nuclear medicine

Background:

• Assessing cellular radiation dose in complex environments is crucial for targeted therapies.
• Iodine-131 (131I) in a simulated thyroid provides a model for evaluating dose distribution from electron emissions.

Purpose of the Study:

• To utilize the Monte Carlo code CELLDOSE for mapping electron dose deposition.
• To quantify the dose received by specific target cells in a heterogeneous, multi-source environment.

Main Methods:

• A simulated thyroid model with spherical units representing follicles was developed.
• Iodine-131 (131I) was homogeneously distributed in the lumen of thyroid follicles.
• Dose distribution was assessed in a single follicle and then expanded to include surrounding follicles.

Main Results:

• Electron dose from 131I decreased significantly beyond 2,100 microm.
• Dose to colloid was higher than to thyroid cells within a single follicle.
• Significant dose heterogeneity was observed even with neighboring follicle contributions, with 82.7% of the dose to thyroid cells originating from surrounding follicles.

Conclusions:

• The Monte Carlo code CELLDOSE effectively maps electron dose and builds target cell dose in complex environments.
• This modeling approach is valuable for comparing radiopharmaceuticals in oncology.
• Understanding dose heterogeneity is critical for optimizing targeted radionuclide therapies.