Development and Validation of RAPID: A Patient-Specific Monte Carlo Three-Dimensional Internal Dosimetry Platform

Area of Science:

• Medical Physics
• Nuclear Medicine
• Computational Biology

Background:

• Accurate internal dosimetry is crucial for effective radiopharmaceutical therapy and radiation safety.
• Patient-specific dosimetry requires advanced computational tools to handle complex 3D dose distributions.

Purpose of the Study:

• To develop and validate RAPID (Radiopharmaceutical Assessment Platform for Internal Dosimetry), a patient-specific Monte Carlo platform for internal dosimetry.
• To assess the accuracy of RAPID's dose calculations against established benchmarks.

Main Methods:

• Utilized serial PET/CT or SPECT/CT images for patient-specific data.
• Employed the Geant4 Monte Carlo code for voxelized 3D internal dose distribution calculations.
• Benchmarked calculations against published S-values and specific absorbed fractions (SAFs) using Zubal and spherical tumor phantoms.

Main Results:

• RAPID's S-values and SAFs in the Zubal phantom were within 5% of published values, with minor deviations for low-energy photons.
• Agreement within 2-9% was achieved for S-values of various radionuclides (e.g., 177Lu, 131I, 68Ga) in spherical tumor phantoms.
• Demonstrated high accuracy across a range of phantom sizes and radionuclide types.

Conclusions:

• RAPID is a validated platform capable of accurate voxel-level internal dosimetry.
• The tool can compute patient-specific 3D dose distributions for diverse radionuclides.
• RAPID shows potential as a valuable tool in personalized nuclear medicine and radiation therapy planning.