Publications by authors named "N K Umisedo"

Thermoluminescence (TL) and Radioluminescence (RL) are widely used in dosimetry applications. We present a custom-built integrated system, designated LUMI22, for measuring TL, TL spectroscopy, RL, and RL as a function of temperature. LUMI22 includes a heating system based on Kanthal® A1 alloy (FeCrAl), a microcontroller to regulate the temperature ramps (e.

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Purpose: A Monte Carlo (MC) modeling of single axial and helical CT scan modes has been developed to compute single and accumulated dose distributions. The radiation emission characteristics of an MDCT scanner has been modeled and used to evaluate the dose deposition in infinitely long head and body PMMA phantoms. The simulated accumulated dose distributions determined the approach to equilibrium function, H(L).

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This study describes the characterization of an AlO:C OSLD (Landauer's Luxel™ tape) for dose evaluation in Computed Tomography. The irradiations were conducted using both a constant potential X-ray equipment and a 64-slice clinical CT scanner, and the readouts were performed using a Risø TL/OSL reader. The following aspects were studied: batch homogeneity, energy response, linearity of dose response, reproducibility, reusability, and effect of uncertainties with the normalization of OSL signals per their response to beta radiation.

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Calcium fluoride (CaF), in both natural and synthetic forms, has been exhaustively studied and explored as thermoluminescent (TL) detector. However its sensitivity to ambient light points to the applicability of CaF as OSL (Optically Stimulated Luminescence) detector, increasing the research about its luminescent properties. Although some properties to employ CaF detectors with OSL technique have been already demonstrated, there is a lack of some essential information as the OSL response to different types and energy of ionizing radiation.

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As the ionizing radiation to which workers are exposed is related to possible harmful biological effect, its dose evaluation gains relevance. Although the effects of low doses are still controversial, the radiation protection authorities assume that any dose of ionizing radiation is potentially harmful to the human health and adopt the linear non-threshold model for the dose-effect relation. The Dosimetry Laboratory of the Institute of Physics of the University of São Paulo performs the external individual monitoring of workers exposed to X- and gamma-rays since 1981, with the technique of thermoluminescence.

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