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Lai B.-L.,National Tsing Hua University | Sheu R.-J.,National Tsing Hua University | Lin U.-T.,Institute of Radiological science
Health Physics | Year: 2015

Monte Carlo simulations are generally considered the most accurate method for complex accelerator shielding analysis. Simplified models based on point-source line-of-sight approximation are often preferable in practice because they are intuitive and easy to use. A set of shielding data, including source terms and attenuation lengths for several common targets (iron, graphite, tissue, and copper) and shielding materials (concrete, iron, and lead) were generated by performing Monte Carlo simulations for 100-300 MeV protons. Possible applications and a proper use of the data set were demonstrated through a practical case study, in which shielding analysis on a typical proton treatment room was conducted. A thorough and consistent comparison between the predictions of our point-source line-of-sight model and those obtained by Monte Carlo simulations for a 360° dose distribution around the room perimeter showed that the data set can yield fairly accurate or conservative estimates for the transmitted doses, except for those near the maze exit. In addition, this study demonstrated that appropriate coupling between the generated source term and empirical formulae for radiation streaming can be used to predict a reasonable dose distribution along the maze. This case study proved the effectiveness and advantage of applying the data set to a quick shielding design and dose evaluation for proton therapy accelerators. © Lippincott Williams & Wilkins. Source

Tsai C.-S.,Institute of Radiological science
Communications in Computer and Information Science | Year: 2011

The design and making of the radiographic simulation system contain five parts including input unit, analog-to-digital converter, ALU and CU, memory, and output unit. In this work, we totally stored about 40 significant images of the skeleton system for different considerations of anatomy and physiology in the database. The images of the skeleton system in this radiographic simulation system can use as the auxiliary teaching materials for related undergraduate courses and currium design of radiologic diagnostic technology in Tzu-Chi college of Technology. The radiographic simulation system may play the role and functions of a real x-ay unit and use as a auxiliary teaching tool. It seem that it is suitable like a safe hi-efficiency teaching medium and tool for e-learning. © 2011 Springer-Verlag Berlin Heidelberg. Source

Chang K.-P.,Institute of Radiological science | Chen C.-K.,Institute of Nuclear Energy Research of Taiwan | Shen L.-H.,Institute of Nuclear Energy Research of Taiwan
Journal of Radioanalytical and Nuclear Chemistry | Year: 2011

Accurately determining the amount of a radionuclide actually administered to a patient is an important aspect of quality control in nuclear medicine. In this study, in order to accurately assess the "apparent" radioactivities of radionuclides with impurities by a dose calibrator, two methods, (1) curve fitting, and (2) relative sensitivities calculation, have been employed to determine the parameter, M (relative response). From the comparisons between the measurement and re-calculated radioactivity using the M values, each method was found to have its own advantage and disadvantage, depending upon the fraction ratio of the impurity as well as the energy level of the impurity's photons. This study might be helpful for improving the assessment of radiopharmaceuticals' "true" activity and its "apparent" activity measured by a dose calibrator. © 2011 Akadémiai Kiadó, Budapest, Hungary. Source

Huang Y.-H.,Tzu Chi University | Yang P.-M.,Taipei Medical University | Chuah Q.-Y.,Tzu Chi University | Lee Y.-J.,National Yang Ming University | And 4 more authors.
Autophagy | Year: 2014

Ionizing radiation induces cellular senescence to suppress cancer cell proliferation. However, it also induces deleterious bystander effects in the unirradiated neighboring cells through the release of senescence-associated secretory phenotypes (SASPs) that promote tumor progression. Although autophagy has been reported to promote senescence, its role is still unclear. We previously showed that radiation induces senescence in PTTG1-depleted cancer cells. In this study, we found that autophagy was required for the radiation-induced senescence in PTTG1-depleted breast cancer cells. Inhibition of autophagy caused the cells to switch from radiation-induced senescence to apoptosis. Senescent cancer cells exerted bystander effects by promoting the invasion and migration of unirradiated cells through the release of CSF2 and the subsequently activation of the JAK2-STAT3 and AKT pathways. However, the radiation-induced bystander effects were correlated with the inhibition of endogenous autophagy in bystander cells, which also resulted from the activation of the CSF2-JAK2 pathway. The induction of autophagy by rapamycin reduced the radiation-induced bystander effects. This study reveals, for the first time, the dual role of autophagy in radiation-induced senescence and bystander effects. © 2014 Landes Bioscience. Source

Sheu R.-J.,National Tsing Hua University | Sheu R.-J.,National Synchrotron Radiation Research Center | Lai B.-L.,Institute of Radiological science | Lin U.-T.,Institute of Radiological science | Jiang S.-H.,National Tsing Hua University
Health Physics | Year: 2013

Proton therapy accelerators in the energy range of 100-300 MeV could potentially produce intense secondary radiation, which must be carefully evaluated and shielded for the purpose of radiation safety in a densely populated hospital. Monte Carlo simulations are generally the most accurate method for accelerator shielding design. However, simplified approaches such as the commonly used point-source line-of-sight model are usually preferable on many practical occasions, especially for scoping shielding design or quick sensitivity studies. This work provides a set of reliable shielding data with reasonable coverage of common target and shielding materials for 100-300 MeV proton accelerators. The shielding data, including source terms and attenuation lengths, were derived from a consistent curve fitting process of a number of depth-dose distributions within the shield, which were systematically calculated by using MCNPX for various beam-target shield configurations. The general characteristics and qualities of this data set are presented. Possible applications in cases of single- and double-layer shielding are considered and demonstrated. Copyright © 2013 Health Physics Society. Source

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