Voxel based internal dosimetry during radionuclide therapy

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiotherapy

Background:

• Radionuclides like Iodine-131 are crucial in cancer treatment, necessitating accurate absorbed dose estimation for efficacy and safety.
• Effective comparison of different radiotherapy techniques relies on precise knowledge of absorbed doses to tumors and normal tissues.
• Voxel-based internal dosimetry offers patient-specific accuracy for absorbed dose calculations.

Purpose of the Study:

• To develop a computer algorithm for calculating absorbed dose in every voxel of quantitative SPECT scintigraphy images.
• To establish a general internal dosimetry protocol for radionuclide therapy.

Main Methods:

• Utilized MATLAB to create an algorithm for converting SPECT count rates to voxel-specific Iodine-131 activity.
• Employed a 3D convolution method with a 5x5x5 matrix to compute absorbed dose from cumulative activity.
• Enabled calculation of dose-volume histograms and mean absorbed doses for defined regions of interest.

Main Results:

• The algorithm accurately calculated a mean absorbed dose of 20.6 Gy for a 64MBq Iodine-131 source.
• A maximum dose of 50 Gy was determined for the central voxel.
• Results showed good agreement with the established MIRDOSE3.1 program (20.1 Gy mean dose).

Conclusions:

• MATLAB-based voxel internal dosimetry provides accurate, patient-specific absorbed dose calculations.
• The developed method facilitates the computation of dose-volume histograms and mean absorbed doses.
• This approach enhances the precision of radionuclide therapy dosimetry.