Energy absorption and exposure build-up factors in hydroxyapatite

The effective atomic number (Z eff) and electron density (N el) of hydroxyapatite (HA) and cortical bone have been computed for total photon interaction in the wide energy range of 1 keV-100 GeV using WinXCom. The variations of effective atomic number and electron density with energy of HA are compared with that of cortical bone. GP. fitting method has been used to compute energy absorption and exposure build-up factor of HA for wide energy range (0.015 MeV-15 MeV) up to the penetration depth of 40mean free path. The computed absorption build-up factor is used to estimate specific absorbed fraction of energy (Ï) and relative dose of photon in HA. Build-up factor increases with increase of penetration depth. The results of the present paper will also help in estimating safe dose levels for radiotherapy patients and also will be useful in dosimetry and diagnostics. © 2012 Elsevier Ltd. All rights reserved

Computation of exposure build-​up factors in teeth

The G-​P fitting method has been used to compute the exposure build-​up factor of teeth [enamel outer surface (EOS)​, enamel middle (EM)​, enamel dentin junction towards enamel (EDJE)​, enamel dentin junction towards dentin (EDJD)​, dentin middle (DM) and dentin inner surface (DIS)​] for a wide energy range (0.015-​15 MeV) up to the penetration depth of 40 mean free paths. The dependence of exposure build-​up factor on incident photon energy, penetration depth, electron d. and effective at. no. has also been studied. The computed exposure build-​up factor is useful to est. the relative dose distribution in different regions of teeth

Yield constants of external Bremsstrahlung excited by 90Sr-​90Y, 147Pm and 204Tl in CdO and lead compounds

Bremsstrahlung yield of 90Sr-​90Y, 147Pm and 204Tl in CdO, PbF2, Pb(NO3)​2 and PbCl2 has been measured using 3.8 cm×3.8 cm NaI(Tl) crystal and is compared with Tseng and Pratt theory. The Z dependence of external Bremsstrahlung (EB) is also measured and compared with the theory. The Bremsstrahlung photon yield and energy yield consts. (K' and K) are evaluated from the measured and theor. yields. These values decrease with the increase in Emax of beta. The evaluated K' and K may be useful to calc. the photon yield and the energy yield, when these beta particles interact with the compds. of modified at. no. ranging from 42 to 73

Bremsstrahlung exposure of tissues from beta-therapeutic nuclides

The Bremsstrahlung exposure rate from beta point source, probability of energy loss by beta during the Bremsstrahlung emission and the Bremsstrahlung activity of tissues have been calculated. The Bremsstrahlung yield for tissues in the wide energy range is also estimated from 0.01 to 100 MeV using the tabulated values given for elements by Lucien pages. The estimated Bremsstrahlung activities of pure beta nuclides in all types of tissues are extremely large (102106 GBq). The patients receiving such nuclides would never receive that much activity because of prohibitive radiation toxicity (few 100 MBq). Thus the patients receiving these pure beta emitting nuclides do not have to be hospitalized for radiation precautions. © 2010 Elsevier B.V. All rights reserved

Numerical method for external Bremsstrahlung cross sections in compounds

A numerical method is used to evaluate External Bremsstrahlung (EB) cross section in compounds such as NaI, SiLi, and GeLi first time using tabulated data given for elements. Modified atomic number defined for compound is used to evaluate cross section. This evaluated theoretical data may be useful for the analysis of experimental spectrum and yield of EB in thick target compounds

External bremsstrahlung spectra of the 90Sr source in some lead compounds measured using NaI detector

The spectral distributions of external bremsstrahlung (EB) excited by beta particles from a 90Sr/ 90Y source in thick target compounds PbCl 2, PbF 2, Pb(NO 3) 2 and CdO were measured using a 3.8 cm à 3.8 cm NaI(Tl) crystal. The spectra, unfolded using the Liden-Starfelt procedure, showed fairly good agreement with theory (Tseng and Pratt) at low energies and some deviation (less than 15) at higher energies. The discrepancy between theory and experiment increases with modified atomic number of the target compound and photon energy. The application of the measured/theoretical spectrum to estimate the bremsstrahlung dose is also discussed. © 2011 Elsevier Ltd. All rights reserved

Exposure of bremsstrahlung from beta-emitting therapeutic radionuclides

There has been an increased interest in beta therapeutic nuclear medicine, which emits relatively high-energy (>1 MeV) β-rays and the production in vivo of Bremsstrahlung sufficient for external imaging, the produced Bremsstrahlung radiation hazard warrants evaluation. The Bremsstrahlung dose from patient administered β-ray emitted radionuclide has been calculated by extending the national council on Radiation Protection and measurement model of a point source in air to account for biologic elimination of activity. We have estimated the probability of bremsstrahlung production, specific Bremsstrahlung constant (defined by Zanzonico et al.) and activity (Arelease) in bone cortical, bone compact, different regions of tooth enamel (enamel dentin junction (EDJ), enamel middle surface, enamel inner surface), different regions of dentin (outer surface, middle surface, enamel dentin junction (EDJ)), soft tissue, lungs and skeleton for different therapeutic beta-emitting radionuclide. In the present calculations we have used modified atomic number (Zmod) defined for bremsstrahlung process. Proper localization and quantification of incorporated beta emitters in bone and tooth are possible, because Bremsstrahlung production is greater in bone and tooth than soft tissue due to their high modified atomic number (Zmod). Radionuclide therapy with pure β-ray emitters emitted in bone, tooth, soft tissue, lungs and skeleton does not require medical confinement of patients for radiation protection. © 2009 Elsevier Ltd. All rights reserved

Theoretical data of External Bremsstrahlung radiation cross-section of bone

Theoretical data of external Bremsstrahlung (EB) radiation cross section of bone is estimated using tabulated results of EB cross section given for various elements at various photon and electron energies. This data may be useful in the analysis of Bremsstrahlung imaging which is the technique applied in medical therapy. © 2006 Elsevier Ltd. All rights reserved

Studies on External Bremsstrahlung in thick target compounds

Most of external Bremsstrahlung (EB) works of beta have been carried out using only metal as a thick target but using compound as a thick target is lacking. Present study is made to (i) follow the interpolation technique to extend the existing theory from elements to compounds (ii) focus on various compounds which can be used as targets for incident beta particles to produce EB spectrum (iii) compare experimental results with the theory suitably extended to compound. Experiment has been carried out in a good geometry set up. In the present study, beta source such as 204Tl (0.766 MeV) and thick target compounds, PbCl2 and CdO have been used. After carrying out the unfolded procedure, measured spectrum has been compared with the theoretical spectrum. © 2007 Elsevier B.V. All rights reserved