Characterization of Geiger-Müller radiation detectors response at the University of Costa Rica's Cyclotron Facilities / Caracterización de la respuesta de detectores de radiación Geiger-Müller en el Ciclotrón de la Universidad de Costa Rica

To ensure a reliable verification of a radiation detector, the right parameters for this response verification must be determined and a specific characterization on the detectors of interest must be performed. These were the main pillars of this study, where four Geiger-Müller at the University of Costa Rica's Cyclotron Facilities' main laboratories were studied and characterized using a 137Cs source. First, a verification of the inverse-square law was performed to corroborate the correct measurement by the detectors as the distance from a 137Cs source to the detectors was varied using a new design for a positioner support to ensure repeatability. This verification yielded a potential fit curve with and equation D=670635 x-1.961 (error percentage of 1.95%) and an R2 value of 0.9836. Then, using combinations of copper plates of widths 1.0 mm and 2.0 mm as attenuators between the source and the detectors, the mass attenuation coefficient for copper was obtained only as a reference value for future calibrations of the detectors. The result for this value was 0.040 cm2 /g. The results obtained in this study and the method developed to achieve these results will serve as a base for calibrations of the detectors at these facilities, which will ensure the safety of the patients and personnel in this building.

Para asegurar respuesta correcta de un detector de radiación, se deben determinar los parámetros correctos para esta verificación y debe realizarse una caracterización específica de los detectores de interés. Estos fueron los pilares principales de este estudio, donde se estudiaron y caracterizaron 4 detectores Geiger-Müller en los laboratorios principales del Ciclotrón de la Universidad de Costa Rica utilizando una fuente radiactiva de 137Cs. Primero, se realizó una verificación de la ley del inverso-cuadrado para corroborar la medición correcta de los detectores según se varía la distancia entre la fuente de 137Cs al detector utilizando un diseño nuevo de un soporte posicionador para la fuente que asegura la repetibilidad entre experimentos. Esta verificación resultó en una curva de ajuste potencial de ecuación D=670635x-1,961 (porcentaje de error de 1,95%) y un valor de R2 de 0,9836. Luego, utilizando combinaciones de placas de cobre de espesores 1,0 mm y 2,0 mm como atenuadores entre la fuente y los detectores, se obtuvo el coeficiente de atenuación másico para el cobre como un valor de referencia para futuras calibraciones de los detectores. Este resultado fue de 0,040 cm2/g. Los resultados obtenidos en esta investigación y el método desarrollado para lograr estos resultados servirán como una base para una futura confirmación metrológica calibraciones de los detectores en estos laboratorios, lo cual colaborará con la seguridad y protección radiológica de pacientes y trabajadores en este edificio.

¿Son reproducibles las mediciones dosimétricas a bajas dosis en cardiología intervencionista? / Are dosimetric measurements at low doses reproducible in interventional cardiology?

Abstract. There are several methods for measuring the absorbed radiation dose of occupationally exposed professionals, but it is unknown if these are reproducible at low doses. The aim of this study is to determine the level of reproducibility of thermoluminescent dosimeters (TLD) and optically stimulated luminescence dosimeters (OSL) in simulated conditions. A reproducibility study was performed using two types of dosimeters, which were placed in the location of medical interventionist work area inside the catheter laboratory. An anthropomorphic phantom was used as a patient and the same projections, collimation and radiographic techniques that were employed in the past 30 angiographies, an examination considered as low exposure in the context of interventional cardiology. Lin's concordance coefficient correlation was calculated, obtaining a value of -0.006 with a 95% CI of -0.069 to 0.056 for TLD dosimeters with OSL. The data obtained showed poor reproducibility at low doses of radiation.

Resumen. Existen varios métodos para medir la dosis de radiación absorbida por los profesionales ocupacionalmente expuestos, pero se desconoce si estos son reproducibles entre sí a bajas dosis. El objetivo del estudio fue determinar el grado de reproducibilidad entre los dosímetros termoluminiscentes (TLD) y los dosímetros luminiscentes ópticamente estimulados (OSL), en condiciones simuladas. Se realizó un estudio de reproducibilidad, empleando 2 tipos de dosímetros, los cuales se dispusieron en la ubicación de trabajo del médico intervencionista dentro del pabellón. Se empleó un fantoma antropomórfico como paciente y se replicaron las mismas proyecciones, colimación y técnicas radiológicas empleadas en las últimas 30 coronariografías, examen considerado de baja exposición en el contexto de cardiología intervencionista. Se aplicó el coeficiente de correlación de concordancia de Lin, obteniéndose un valor de -0,006 con un IC al 95% de -0,069 a 0,056 para los dosímetros TLD con OSL. Los datos obtenidos mostraron una escasa reproducibilidad a bajas dosis de radiación.

Occupational Hazard: Radiation Exposure for the Urologist – Developing a Reference Standard

Introduction To date, there is a paucity of literature offering practicing urologists a reference for the amount of radiation exposure received while surgically managing urolithiasis. This study examines the cumulative radiation exposure of an urologist over 9 months. Materials and Methods We present a case series of fluoroscopic exposures of an experienced stone surgeon operating at an academic comprehensive stone center between April and December 2011. Radiation exposure measurements were determined by a thermoluminescent dosimeter worn on the outside of the surgeon's thyroid shield. Estimations of radiation exposure (mrem) per month were charted with fluoroscopy times, using scatter plots to estimate Spearman's rank correlation coefficients. Results The total 9-month radiation exposure was 87 mrems for deep dose equivalent (DDE), 293 mrem for lens dose equivalent (LDE), and 282 mrem for shallow dose equivalent (SDE). Total fluoroscopy time was 252.44 minutes for 64 ureteroscopies (URSs), 29 percutaneous nephrolithtomies (PNLs), 20 cystoscopies with ureteral stent placements, 9 shock wave lithotripsies (SWLs), 9 retrograde pyelograms (RPGs), 2 endoureterotomies, and 1 ureteral balloon dilation. Spearman's rank correlation coefficients examining the association between fluoroscopy time and radiation exposure were not significant for DDE (p = 0.6, Spearman's rho = 0.2), LDE (p = 0.6, Spearman's rho = 0.2), or SDE (p = 0.6, Spearman's rho = 0.2). Conclusions Over a 9-month period, total radiation exposures were well below annual accepted limits (DDE 5000 mrem, LDE 15,000 mrem and SDE 50,000 mrem). Although fluoroscopy time did not correlate with radiation exposure, future prospective studies can account for co-variates such as patient obesity and urologist distance from radiation source. .

Avaliação do ambiente eletromagnético em estabelecimentos assistenciais de saúde / Electromagnetic environment assessment in health care facilities

A crescente inserção de tecnologia eletroeletrônica em estabelecimentos assistenciais de saúde (EAS), seja como equipamentos terapêuticos, de diagnóstico ou até mesmo suporte vital, tem sido vista pela comunidade científica como a grande responsável pelo aumento dos níveis de energia eletromagnética emitidos ao ambiente hospitalar. Dessa forma, quando a energia eletromagnética presente no ambiente atinge um determinado nível crítico, fica estabelecida uma situação que é propícia ao aparecimento de dois fenômenos indesejados: a interferência eletromagnética (EMI) em equipamentos médicos, e os riscos biológicos (RBL) em seres vivos. Um importante recurso para gerenciar a compatibilidade eletromagnética e evitar o aparecimento destes fenômenos é o conhecimento das características eletromagnéticas presentes nestes ambientes. O objetivo deste trabalho é diagnosticar o comportamento eletromagnético estabelecido em ambientes de grande concentração de fontes emissoras como, por exemplo, o encontrado em centros cirúrgicos, através de uma série de medições in situ das grandezas eletromagnéticas envolvidas nestes meios (campos elétricos, campos magnéticos, ruídos conduzidos). Com base nestas medidas é realizada uma avaliação crítica de modo a comparar a situação estabelecida nos EAS e os limites de segurança preconizados por organismos competentes, tanto para EMI quanto para RBL. Como resultado desta análise, começa a existir maior discernimento quanto à real situação do ambiente eletromagnético encontrado em EAS nacionais, subsidiando informações para a definição de diretrizes mais eficientes para implementação de programas de gestão tecnológica que são direcionados às necessidades específicas destes hospitais.

Advances in technology and the increased use of electro-medical equipment (EME) to support medical procedures such as monitoring, diagnosis, therapeutic or even life support are considered as greatly responsible for the increase of electromagnetic energy within health care facilities (HCF) environments. In such circumstances, when electromagnetic energy reaches a certain critical level, a dangerous situation is established and two undesirable phenomena can take place, both electromagnetic interference (EMI) in medical equipment, and biological risks (BLR) in living beings. The knowledge of electromagneticcharacteristics shown by these environments can represent an important tool in order to promote electromagnetic compatibility and avoid the appearance of undesirable phenomena. Therefore, this work aims to diagnose the electromagnetic profile established in critical areas, such as operating rooms, through a number of “in situ” measurements concerning electromagnetic quantities present in this environment (electric field, magnetic field, conducted noise). Moreover, a critical evaluation follows in order to compare the establishedsituation within HCF and the safety levels prescribed by regulatory organizations regarding EMI and BLR. As a result of this assessment, a better understanding on the actual situation concerning the electromagnetic environment in HCF can be achieved, allowing clinical engineers to define better directives in order to implement an adequate management programs in these hospitals.

Study of seasonal variations for radon pollution in the environment of Muktsar and Ferozepur districts of Punjab using LR-115 plastic track detectors.

Indoor Radon measures have been carried out in the dwellings of Muktsar and Ferozepur districts of punjab using LR-115 plastic track detectors. Indoor Radon values ranged from 95 to 226 bq m(-3) and 75 to 233 bq m(-3) for winter season and 61 to 129 bq m(-3) and 79 to 138 bq m(-3) for summer season for Muktsar and Ferozepur districts respectively. These values are within the safe limits recommended by International Commission on Radiological Protection (ICRP).

Onde usar o monitor individual de radiaçäo / Are where use the individual monitor of radiation?

É apresentada uma análise de dados de doses de trabalhadores que utlizaram simultaneamente 2 ou 3 monitores de radiação individuais em locais diferentes do corpo, durante alguns anos. Os resultados mostram que é importante o uso do avental e pescoceira de chumbo no setor de hemodinâmica, assim como a manipulação correta de fontes não seladas no setor de Medicina Nuclear (MN). No setor de hemodinâmica, as doses equivalentes máximas no pulso chegam a cerca de 10mSv/mês, enquanto que as doses equivalentes máximas sob avental e sob pescoceira de chumbo atingem 0,8mSv/mês.