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Limitations of conventional internal dosimetry at the cellular level
G M Makrigiorgos1, S J Adelstein, A I Kassis
1Department of Radiology, Harvard Medical School, Shields Warren Radiation Laboratory, Boston, Massachusetts.
Summary
Conventional internal dosimetry significantly underestimates cellular radiation dose when radiolabeled compounds concentrate within specific cells. This study developed a new model for accurate internal dosimetry, crucial for targeted radionuclide therapy.
Area of Science:
- Medical Physics
- Radiological Sciences
- Biophysics
Background:
- Classic internal dosimetry relies on assumptions that may not hold true at the cellular level.
- Selective uptake of radiolabeled compounds by specific cells can significantly alter radiation dose distribution.
- Accurate dosimetry is critical for effective and safe radionuclide therapy.
Purpose of the Study:
- To theoretically examine the validity of classic internal dosimetry assumptions at the cellular level.
- To develop an alternate dosimetric model accounting for selective cellular uptake.
- To compare dose estimates from the new model with conventional dosimetry for various radionuclides.
Main Methods:
- Developed a new dosimetric model for multicellular clusters with hexagonal geometry.
- Accounted for selective intracellular uptake of radiolabeled compounds.
- Compared cellular dose estimates for electrons from 99mTc, 201Tl, 111In, and 123I using both models.
Main Results:
- Conventional dosimetry underestimates radiation dose to labeled cells by 2- to 25-fold for low-energy electrons (<10 keV).
- Conventional dosimetry slightly overestimates dose to nonlabeled cells (20%–50%) under selective uptake conditions.
- Photon contributions did not significantly alter the conclusions regarding electron dosimetry.
Conclusions:
- Classic internal dosimetry assumptions are inadequate for scenarios with selective cellular uptake.
- The developed model provides more accurate cellular dose estimates, especially for low-energy electrons.
- Accurate dosimetry considering cellular heterogeneity is essential for optimizing radionuclide therapy outcomes.