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Hamid Reza Baghani Mostafa Robatjazi Seyed Rabi Mahdavi 《Radiation and environmental biophysics》2020,59(2):265-281
Radiation-shielding of healthy tissue is mandatory in breast intraoperative electron radiotherapy (IOERT). In this regard, dedicated radioprotection disks have been introduced. The aim of this study was to evaluate and compare the performance of three radioprotection disks widely used for breast IOERT. A Monte Carlo simulation approach was used for this purpose. The considered disks included Al + Pb, PMMA + Copper, and PTFE + Steel. They were stimulated by means of the MCNPX Monte Carlo code at depths around R100 and R90 of different electron energies in a water phantom, and their impact on the dosimetric properties of the therapeutic beam was evaluated in both correct and upside down disk placements. The electron energy spectrum immediately above and below each disk was calculated and analyzed. Furthermore, performance characteristics of the studied disks such as backscatter factors (BSFs) and transmission factors (TFs) at different electron energies were determined and compared. The results show that the Al + Pb disk most effectively attenuates the beam, while at the same time exhibits maximum BSF values. Employing the PMMA + Copper disk can minimize the BSF value but at the expense of an increased TF. The Al + Pb disk showed the best performance from the radiation protection viewpoint, while its highest BSF values could lead to perturbation of dose homogeneity within the target volume. PTFE + Steel disk showed an intermediate performance regarding the electron backscattering and transmission among the studied disks. The reverse placement of each disk can substantially increase the BSF value as compared to the correct situation but had less impact on the TF value. 相似文献
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Baghani Hamid Reza Hosseini Aghdam Seyed Rashid Robatjazi Mostafa Mahdavi Seyed Rabi 《Radiation and environmental biophysics》2019,58(2):263-276
Radiation and Environmental Biophysics - Evaluating the stray radiation around medical electron accelerators is a mandatory issue. Surveying the radiation leakage dose is important for patients,... 相似文献
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Seyed Mortaza Robatjazi Seyed Abbas Shojaosadati Rassoul Khalilzadeh Ebrahim Vasheghani Farahani Mehdi Zeinoddini 《Biotechnology letters》2013,35(1):67-73
Magnetically-modified Sphingomonas sp. was prepared using covalent binding of magnetic nanoparticles on to the cell surface. The magnetic modified bacteria were immobilized in the fixed-bed bioreactors (FBR) by internal and external magnetic fields for the biodetoxification of a model organophosphate, parathion: 93 % of substrate (50 mg parathion/l) was hydrolyzed at 0.5 ml/min in internal magnetic field fixed-bed bioreactor. The deactivation rate constants (at 1 ml/min) were 0.97 × 10?3, 1.24 × 10?3 and 4.17 × 10?3 h?1 for immobilized bacteria in external and internal magnetic field fixed-bed bioreactor and FBR, respectively. The deactivation rate constant for immobilized magnetically modified bacteria in external magnetic field fixed-bed bioreactor (EMFFBR) was 77 % lower than that of immobilized cells by entrapping method on porous basalt beads in FBR at 1 ml/min. Immobilized magnetic modified bacteria exhibited maximum enzyme stability in EMFFBR. 相似文献
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