Dose conversion coefficients for electron exposure of the human eye lens

Abstract

Due to two errors in the geometry module of the EGSnrc C++ class library egs++ (EGSpp), several data presented in the original work are not correct. The following figures and tables present the correct values of the dose conversion coefficients for electron exposure of the human eye lens.The corrected values deviate at most by about 25% and 50% for 0 • and 45 • angles of incidence, respectively, from the ones presented originally.The conclusions given in sections 4 and 5 of the original paper are, however, still valid. Nevertheless, the text has to be slightly modified: the last sentence in the abstract must be changed to 'Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP) the new values are up to 20 000 times smaller for electron energies below 1 MeV, nearly equal at 1 MeV and above 2 MeV, and by a factor of 1.3 larger at about 1.5 MeV electron energy'. In section 3.2, line one, the words 'near 2 MeV' must be changed to 'below 2 MeV'. In the same section, third bullet point, line five, the words 'from side to top to bottom' must be changed to 'from side to bottom to top'. In section 3.3, line five, the words 'a significant impact' must be changed to 'no significant impact'; the rest of that sentence must be deleted.The first error in EGS++ was corrected by Ernesto Mainegra from the National Research Council of Canada (NRC). A short description of what has to be done to remove the error is given as follows.

Role of Vitreoretinal Surgery in Maximizing Treatment Outcome Following Complications After Proton Therapy for Uveal Melanoma

“…With a radiation threshold as low as 0.5 Gy for the induction of cataract to the human lens, this is not surprising. 14 Anti-vascular endothelial growth factors were scarcely used in this case series, as most of these cases were treated at a time when potential indications for this kind of treatment were only slowly emerging. Although one might speculate that increased use of anti-vascular endothelial growth factors could potentially prevent VH secondary to proliferative radiation retinopathy in the future, it is more difficult to imagine how these treatments will significantly reduce the apparent mechanical effect of a rupture in the retinal barrier.…”

The reference phantoms: voxel vs polygon

“…The detailed model of the eye developed by Behrens et al (2009), which was adopted for calculations of DC for external beams (ICRP, 2010), has been successfully reproduced and incorporated in the PM phantoms. First, a NURBS-surfacebased eye model was produced from the geometrical information of the detailed model of the eye (Behrens et al, 2009) using Rhinoceros software (Robert McNeel & Associates, Seattle, WA, USA). The NURBS model produced was subsequently converted to the PM format.…”

Incorporation of detailed eye model into polygon-mesh versions of ICRP-110 reference phantoms

“…In the present study, a detailed eye model was constructed in polygon-mesh (PM) format based on the eye-model data (see Figure 1, left) of Behrens et al (2009).…”

“…This limitation can be generally found in other voxel phantoms (Pujol and Gibbs 1982, Zankl et al 1988, Petoussi-Henss et al 2002, Park et al 2014, Yeom et al 2014b. Therefore, for better assessment of lens dose coefficients, several investigators (Behrens et al 2009, Nogueira et al 2011, Caracappa et al 2014 developed detailed eye models for low-penetrative radiation, showing a steep dose gradient in the lens; eventually the ICRP adopted a detailed stylized eye model developed by Behrens et al (2009). The lens dose coefficients reported in ICRP Publication 116 (ICRP 2010) were calculated using either this detailed stylized eye model or the ICRP-110 reference phantoms, depending on radiation type, energies, and irradiation geometries.…”

“…As a part of the conversion project, in the present study, we incorporated the detailed stylized eye model developed by Behrens et al (2009) into the phantoms that were constructed by converting the ICRP-110 reference phantom into the PM format. We believe that this approach will result in both simplification of calculation process and improved consistency in lens dose assessment.…”