Nadia Falzone1, José M Fernández-Varea2, Glenn Flux3, Katherine A Vallis4. 1. Department of Oncology, CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom Department of Biomedical Science, Tshwane University of Technology, Pretoria, South Africa nadia.falzone@oncology.ox.ac.uk. 2. Facultat de Física (ECM and ICC), Universitat de Barcelona, Barcelona, Spain; and. 3. Physics Department, Royal Marsden NHSFT, Sutton, Surrey, United Kingdom. 4. Department of Oncology, CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom.
Abstract
UNLABELLED: 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 (67)Ga, (80m)Br, (89)Zr, (90)Nb, (99m)Tc, (111)In, (117m)Sn, (119)Sb, (123)I, (125)I, (195m)Pt, and (201)Tl 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. Dose-point kernels were determined up to 30 μm. Energy deposition at DNA scales was also compared with an α emitter, (223)Ra. 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 (223)Ra. 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.
UNLABELLED: 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 (67)Ga, (80m)Br, (89)Zr, (90)Nb, (99m)Tc, (111)In, (117m)Sn, (119)Sb, (123)I, (125)I, (195m)Pt, and (201)Tl 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. Dose-point kernels were determined up to 30 μm. Energy deposition at DNA scales was also compared with an α emitter, (223)Ra. 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 (223)Ra. 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.
Authors: Vincenzo Abbate; Samantha Y A Terry; Katarzyna M Osytek; Philip J Blower; Ines M Costa; Gareth E Smith Journal: EJNMMI Res Date: 2021-07-05 Impact factor: 3.138
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Authors: Elise Verger; Jordan Cheng; Vittorio de Santis; Madeleine Iafrate; Jessica A Jackson; Cinzia Imberti; Gilbert O Fruhwirth; Philip J Blower; Michelle T Ma; Daniel R Burnham; Samantha Y A Terry Journal: Nucl Med Biol Date: 2021-06-15 Impact factor: 2.408
Authors: Edward O'Neill; Veerle Kersemans; P Danny Allen; Samantha Y A Terry; Julia Baguña Torres; Michael Mosley; Sean Smart; Boon Quan Lee; Nadia Falzone; Katherine A Vallis; Mark W Konijnenberg; Marion de Jong; Julie Nonnekens; Bart Cornelissen Journal: J Nucl Med Date: 2019-11-22 Impact factor: 11.082