Validation of a dose-point kernel convolution technique for internal dosimetry

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiotherapy Dosimetry

Background:

• Accurate three-dimensional (3D) absorbed dose calculation is crucial for radionuclide therapy.
• Quantitative single-photon-emission computed tomography (SPECT) provides 3D activity distributions.
• Existing methods require validation for clinical application.

Purpose of the Study:

• To validate a dose-point kernel convolution technique for 3D absorbed dose distribution of Iodine-131 (131I).
• To assess the accuracy of the technique by comparing calculated doses with experimental measurements.
• To compare the technique with established dosimetry formalisms.

Main Methods:

• Calculated a dose-point kernel for penetrating radiations using Monte Carlo simulation.
• Convolved the kernel with 3D 131I activity maps from quantitative SPECT using fast Fourier transform (FFT).
• Validated calculations against thermoluminescent dosimeter (TLD) measurements and MIRD formalism in a phantom study.

Main Results:

• The convolution technique achieved a mean percentage difference of -1% (SD 3.6%) compared to TLD measurements.
• The method demonstrated agreement within 15% with the MIRD formalism for phantom dosimetry.
• The 3D FFT convolution calculation was efficient, completing in under 40 seconds on a personal computer.

Conclusions:

• The validated dose-point kernel convolution technique accurately determines 3D absorbed dose distributions from 131I.
• This method offers a computationally efficient and reliable tool for internal dosimetry in nuclear medicine.
• The technique shows promise for improving treatment planning and dose assessment in radionuclide therapies.