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A 3-dimensional absorbed dose calculation method based on quantitative SPECT for radionuclide therapy: evaluation for
Michael Ljungberg1, Katarina Sjögreen, Xiaowei Liu
1Department of Radiation Physics, Jubileum Institute, Lund University, Sweden. Michael.ljungberg@radfys.lu.se
Summary
A new method enables patient-specific 3D absorbed dose calculations using quantitative SPECT imaging. This approach corrects for most image-degrading factors, improving accuracy for SPECT-based dosimetry.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Radiotherapy Physics
Background:
- Accurate patient-specific absorbed dose calculation is crucial for effective radiotherapy.
- Quantitative SPECT imaging offers potential for improved dosimetry but faces challenges with image quality and accuracy.
Purpose of the Study:
- To present a general method for patient-specific 3D absorbed dose calculations using quantitative SPECT.
- To evaluate the accuracy of this method using realistic simulations.
Main Methods:
- Developed a computational scheme integrating CT-SPECT image registration and iterative reconstruction.
- Incorporated position-dependent compensation for attenuation, scatter, and collimator-detector response.
- Utilized EGS4 Monte Carlo code for converting activity distribution to absorbed dose distribution.
Main Results:
- The method successfully corrected for object scatter, photon attenuation, and collimator scatter penetration.
- Limited spatial resolution of the SPECT system introduced inaccuracies that collimator response correction could not fully overcome.
Conclusions:
- The presented method compensates for most parameters degrading quantitative SPECT image information.
- Compensation methods are based on physical models, making them generally applicable to various radionuclides.
- The evaluation methodology provides a basis for comparing different quantitative SPECT dosimetry methods.