Assessing Ir-192 as an alternative to I-125 in ophthalmic treatment

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dc.contributor.authorANGELOCCI, L.pt_BR
dc.contributor.authorNOGUEIRA, B.R.pt_BR
dc.contributor.authorSOUZA, C.D. dept_BR
dc.contributor.authorZEITUNI, C.A.pt_BR
dc.contributor.authorROSTELATO, M.E.C.M.pt_BR
dc.coverageInternacionalpt_BR
dc.date.accessioned2022-02-04T14:42:48Z
dc.date.available2022-02-04T14:42:48Z
dc.date.issued2020pt_BR
dc.description.abstractPurpose or Objective: Brachytherapy sources for ocular melanoma usually contain Co-60, I-125, Pd-103 or Ru/Rh-106 as radionuclides. Ir-192 is not a preconized radioactive material for this purpose, although it is used for other brachytherapy applications. Higher mean energy from Ir-192 emission (ca. 380 keV) may be a reason for the preference of I-125 (35 keV) or Pd-103 (21 keV) over it, since low penetration is desired on the small structures of the human eye. This is not, however, an excluding criterion, considering Co-60 and Ru/Rh-106 have even higher mean energies. The demand in Brazil for lower-cost seeds to treat ocular melanoma lead to the development of an Ir-192 seed to make treatment more accessible, but since it is not used as an ophthalmic brachytherapy source, before its dosimetry is considered, one should care about the possibility of using it over more stablished materials. Considering this, the aim of this work is to assess the possibility of using Ir-192 seeds as ophthalmic brachytherapy sources by comparing some dosimetric parameters of a new seed model with the most stablished I-125 seed in literature, OncoSeed 6711. Material and Methods: As an initial study on the topic, this work relies only on Monte-Carlo simulations using MCNP4C transport code. Parameters analyzed are air-kerma strength, dose-rate constant and depth-dose curve, attention given to points within the human eye dimensions. The medium considered was homogeneous water, as it is a good approximation to the eye tissues in terms of composition and density and allows for future comparisons with TG-43 based calculations. OncoSeed 6711 is not produced anymore, but its long term as the reference source for dosimetry was considered. A 20 mm COMS ophthalmic applicator was also modeled and considered to be fully loaded with each seed model to compare the same parameters at a realistically clinical approach. Results: As expected, due to the higher energy of the Ir-192 emission spectrum, dose fall-off on the transversal axis of the seeds is less pronounced for the new seed model. The steeper dose gradient for I-125 is also visible on the doserate constant value. The effect of using a COMS applicator only strengthens this characteristic. Depth-dose curves were calculated up to the distance of 5 cm, both for a single seed and for an applicator fully loaded with 24 seeds. All the eye components relevant for dosimetry are located within this range, like the cells of the crystallin and the optical nerve. Conclusion: If one expects to use Ir-192 as an alternative to I-125 in ophthalmic cancer treatment, at least the dosimetry following TG-43 protocol should be carried with utmost attention, as undesirable dose to healthy nearby tissues is unavoidable. Crafting a different applicator most suited for this radionuclide is a possibility that can be taken into account. Another recommendation is to go beyond TG-43 water-based protocol and actually estimate dose to relevant eye components.pt_BR
dc.format.extentS735-S736pt_BR
dc.identifier.citationANGELOCCI, L.; NOGUEIRA, B.R.; SOUZA, C.D. de; ZEITUNI, C.A.; ROSTELATO, M.E.C.M. Assessing Ir-192 as an alternative to I-125 in ophthalmic treatment. <b>Radiotherapy and Oncology</b>, v. 152, p. S735-S736, 2020. Supplement 1. DOI: <a href="https://dx.doi.org/10.1016/S0167-8140(21)01402-X">10.1016/S0167-8140(21)01402-X</a>. Disponível em: http://repositorio.ipen.br/handle/123456789/32695.
dc.identifier.doi10.1016/S0167-8140(21)01402-Xpt_BR
dc.identifier.issn0167-8140pt_BR
dc.identifier.orcid0000-0003-2943-6097pt_BR
dc.identifier.orcid0000-0002-7303-6720pt_BR
dc.identifier.orcid0000-0003-4609-2281pt_BR
dc.identifier.orcidhttps://orcid.org/0000-0003-2943-6097
dc.identifier.orcidhttps://orcid.org/0000-0002-7303-6720
dc.identifier.orcidhttp://orcid.org/0000-0003-1335-8864
dc.identifier.percentilfi82.67pt_BR
dc.identifier.percentilfiCiteScore87.67pt_BR
dc.identifier.suplementoSupplement 1pt_BR
dc.identifier.urihttp://repositorio.ipen.br/handle/123456789/32695
dc.identifier.vol152pt_BR
dc.relation.ispartofRadiotherapy and Oncologypt_BR
dc.rightsopenAccesspt_BR
dc.sourceESTRO, November 28 - December 1, 2020, Onlinept_BR
dc.titleAssessing Ir-192 as an alternative to I-125 in ophthalmic treatmentpt_BR
dc.typeResumos em periódicospt_BR
dspace.entity.typePublication
ipen.autorBEATRIZ RIBEIRO NOGUEIRA
ipen.autorMARIA ELISA CHUERY MARTINS ROSTELATO
ipen.autorCARLOS ALBERTO ZEITUNI
ipen.autorCARLA DARUICH DE SOUZA
ipen.autorLUCAS VERDI ANGELOCCI
ipen.codigoautor7563
ipen.codigoautor7
ipen.codigoautor944
ipen.codigoautor7717
ipen.codigoautor12698
ipen.contributor.ipenauthorBEATRIZ RIBEIRO NOGUEIRA
ipen.contributor.ipenauthorMARIA ELISA CHUERY MARTINS ROSTELATO
ipen.contributor.ipenauthorCARLOS ALBERTO ZEITUNI
ipen.contributor.ipenauthorCARLA DARUICH DE SOUZA
ipen.contributor.ipenauthorLUCAS VERDI ANGELOCCI
ipen.date.recebimento22-02
ipen.identifier.fi6.280pt_BR
ipen.identifier.fiCiteScore8.0pt_BR
ipen.identifier.ipendoc28462pt_BR
ipen.identifier.iwosWoSpt_BR
ipen.range.fi6.000 ou mais
ipen.range.percentilfi75.00 - 100.00
ipen.type.genreResumo
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sigepi.autor.atividadeROSTELATO, M.E.C.M.:7:230:Npt_BR
sigepi.autor.atividadeZEITUNI, C.A.:944:230:Npt_BR
sigepi.autor.atividadeSOUZA, C.D. de:7717:230:Npt_BR
sigepi.autor.atividadeNOGUEIRA, B.R.:7563:230:Npt_BR
sigepi.autor.atividadeANGELOCCI, L.:12698:230:Spt_BR
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