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Abstract: This study presents the results of the intensity variation of the radiation field in a mammographic system using the thermoluminescent dosimeter TLD-900 (CaSO4:Dy). These TLDs were calibrated and characterized in an industrial X-ray system used for instruments calibration, in the energy range used in mammography. They were distributed in a matrix of 19 lines and five columns, covering an area of 18cm×8cm in the center of the radiation field on the clinical equipment. The results showed a variation of the intensity probably explained by the non-uniformity of the field due to the heel effect. [Copyright &y& Elsevier]

Based on uniformity measurements of large-area reference sources used in calibration procedures of surface contamination monitors, an investigation was carried out to obtain a method that estimates the bias originated from surface source intensity distribution deviation from the ideal uniform distribution and corrects it. It relies on correcting the estimated instrument efficiency by applying correction factors driven from the uniformity distribution profiles of the sources used in calibration procedure. Simulations of the monitor calibration procedure are run for 2 distinct surface source distributions: the real and the ideally uniform distributions. Correction factors are driven from counting rate estimates obtained from each source representation. In order to evaluate adequacy of this proposition it was validated against a method proposed by the NPL in the Good Practices Guide No.14., (Copyright © 2020. Published by Elsevier Ltd.)

A pencil-type ionization chamber, developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN), was characterized with the objective to verify the possibility of its application in radiation field mapping procedures. The characterization tests were evaluated, and the results were satisfactory. The results obtained for the X radiation field mapping with the homemade chamber were compared with those of a PTW Farmer-type chamber (TN 30011-1). The maximum difference observed in this comparison was only 1.25%, showing good agreement., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In this work the peak kilovoltage (kVp), practical peak voltage (PPV) and air kerma rate were measured with the noninvasive meters Radcal Accu-kV® Diagnostic Sensor™ model 40×12-W, and PTW Diavolt. The results were compared in order to ensure the quality control, compare the meters and establish the new quantity PPV, at the Calibration Laboratory of IPEN. These tests were performed using the standard diagnostic radiology quality beam RQR5, and the results are in good agreement., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The surface homogeneity of planar sources used to calibrate contamination detectors is important considering that their dimensions are bigger than the most kind of detectors tested and the positioning in relation to the source may vary in each measurement. Using a special pancake detector the counting efficiency of alpha and beta sources was measured in several positioning covering all area of the sources. The (14)C source showed the worse performance and the (241)Am source showed the best behavior., (Copyright 2009 Elsevier Ltd. All rights reserved.)

A new monitor ionization chamber was developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN) in order to monitor X-ray beams. The main difference of this monitor ionization chamber in relation to other monitor chambers is its geometry, which consists of a ring-shaped sensitive volume. Because of this geometry, the monitor chamber has a central hole through which the direct radiation beam passes. The operational characteristics of the monitor chamber were evaluated: saturation, ion collection efficiency and polarity effect. Besides these tests, the short- and medium-term stabilities of its response were also evaluated. During the tests the leakage current was always negligible. All results showed values within those recommended internationally (IEC, 1997. Medical electrical equipment-dosimeters with ionization chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging. IEC 61674. International Electrotechnical Commission, Genève)., (Copyright 2009 Elsevier Ltd. All rights reserved.)