Falzone N., Fernández-Varea J.M., Flux G., Vallis K.A.
Department of Oncology, CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Off Roosevelt Dr., Oxford, United Kingdom; Department of Biomedical Science, Tshwane University of Technology, Pretoria, South Africa; Facultat de Física (ECM and ICC), Universitat de Barcelona, Barcelona, Spain; Physics Department, Royal Marsden NHSFT, Sutton, Surrey, United Kingdom
Falzone, N., Department of Oncology, CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Off Roosevelt Dr., Oxford, United Kingdom, Department of Biomedical Science, Tshwane University of Technology, Pretoria, South Africa; Fernández-Varea, J.M., Facultat de Física (ECM and ICC), Universitat de Barcelona, Barcelona, Spain; Flux, G., Physics Department, Royal Marsden NHSFT, Sutton, Surrey, United Kingdom; Vallis, K.A., Department of Oncology, CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Off Roosevelt Dr., Oxford, United Kingdom
Several radionuclides used in medical imaging emit Auger electrons, which, depending on the targeting strategy, either may be exploited for therapeutic purposes or may contribute to an unintentional mean absorbed dose burden. In this study, the virtues of 12 Auger electron-emitting radionuclides were evaluated in terms of cellular S values in concentric and eccentric cell-nucleus arrangements and by comparing their dose-point kernels. Methods: The Monte Carlo code PENELOPE was used to transport the full particulate spectrum of 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn, 119Sb, 123I, 125I, 195mPt, and 201Tl by means of event-by-event simulations. Cellular S values were calculated for varying cell and nucleus radii, and the effects of cell eccentricity on S values were evaluated. Dosepoint kernels were determined up to 30 μm. Energy deposition at DNA scales was also compared with an α emitter, 223Ra. Results: PENELOPE-determined S values were generally within 10% of MIRD values when the source and target regions strongly overlapped, that is, S(nucleus←nucleus) configurations, but greater differences were noted for S(nucleus←cytoplasm) and S(nucleus←cell surface) configurations. Cell eccentricity had the greatest effect when the nucleus was small, compared with the cell size, and when the radiation sources were on the cell surface. Dose-point kernels taken together with the energy spectra of the radionuclides can account for some of the differences in energy deposition patterns between the radionuclides. The energy deposition of most Auger electron emitters at DNA scales of 2 nm or less exceeded that of a monoenergetic 5.77-MeV α particle, but not for 223Ra. Conclusion: A single-cell dosimetric approach is required to evaluate the efficacy of individual radionuclides for theranostic purposes, taking cell geometry into account, with internalizing and noninternalizing targeting strategies. COPYRIGHT © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
bromine 80m; bromine derivative; indium 111; iodine 123; iodine 125; plutonium; plutonium 195m; radioisotope; radon; radon 223; strontium; strontium 117m; technetium 99m; thallium 201; theranostic radionuclide; tin; unclassified drug; radioisotope; Article; Auger electron spectroscopy; cell nucleus; cell size; cell surface; controlled study; dosimetry; electron; mathematical model; Monte Carlo method; priority journal; radiation absorption; radiation energy; animal; apoptosis; biological model; comparative study; computer simulation; human; linear energy transfer; Monte Carlo method; Neoplasms; radiation dose; radiation response; radiation scattering; scintiscanning; statistical model; Animals; Apoptosis; Computer Simulation; Humans; Linear Energy Transfer; Models, Biological; Models, Statistical; Monte Carlo Method; Neoplasms; Radiation Dosage; Radioisotopes; Scattering, Radiation