Development of dosimetry using detectors of diagnostic digital radiography systems

Abstract

Dosimetry using an imaging plate (IP) of computed radiography (CR) systems was developed for quality control of output of the x-ray equipment. Sensitivity index, or the S number, of the CR systems was used for estimating exposure dose under the routine condition: exposure dose from 1.0 to 1.0 x 10(2) microC kg(-1), tube voltages from 50 to 120 kV, and added filtration from 0 to 4.0 mm Al. The IP was calibrated by using a 6 cc ionization chamber having traceability to the National Standard Ionization Chamber. The uncertainty concerning the fading effect was suppressed less than 1.9% by reading the latent image 4 min+/-5 s after irradiation at the room temperature 25.9+/-1.0 degrees C. The S number decreased linearly on the logarithmic graph regardless of the beam quality as exposure dose increased. The relationship between the exposure dose (E) and the S number was fitted by the equation E=a' X S(-b). The coefficient a' decreased when the added filtration and the tube voltage were increased. The coefficient b was 0.977+/-0.007 in all beam qualities. The dosimetry using the IP and the equation can estimate the exposure dose in a range from 9.0 x 10(-2) to 5.0 microC kg(-1) within an uncertainty of +/-5% required by the Japanese Industry Standard. This dose range partially included the doses under routine condition. The doses between 1.0 and 1.0 x 10(2) microC kg(-1) under the routine condition can be shifted to the 5% region by using an absorber. The IP dosimetry is applicable to the quality control of the CR systems.

Determining air kerma from pixel values in digital mammography

“…Several studies have investigated the use of pixel values in dose estimation (Floyd et al 1990, Tucker and Rezentes 1997, Ariga et al 2007, Kauppinen 2008, Vano et al 2008. However, all of these studies have been performed for computed radiography (CR) systems and, apart from that of Kauppinen (2008), the systems have been used for general radiography (>50 kV).…”

Dosimetria em radiologia diagnóstica digital: Uso dos indicadores de exposição de sistemas digitais como estimadores de dose absorvida

“…Enquanto alguns desses elétrons se recombinam imediatamente com os íons de európio, uma parte fica armazenada nos centros F [Bushberg, et al, 2002]. Essa energia fica armazenada em um estado metaestável e é a base para a formação da imagem latente, que pode ficar armazenada por horas, embora estudos indiquem que não seja recomendado demorar muito para fazer a leitura do IP devido a perdas do sinal por fading [Ariga, 2007] O algoritmo responsável pelo cálculo do lgM utiliza somente valores de pixel referentes a exposição do paciente à radiação, excluindo os valores de regiões que não contribuem para a dose no paciente (regiões fora do corpo mas que recebem diretamente o feixe colimado representando altos níveis de cinza, ou regiões que estão fora do campo do feixe representando baixos níveis de cinza), para isso, o histograma dos valores de pixel é segmentado, e o lgM é calculado como o logaritmo da mediana dos valores de pixel do histograma segmentado [Schaetzing, 2004]. A Figura 6 mostra um exemplo de um histograma segmentado.…”

Dosimetric properties and radiation hardness of the storage phosphor europium doped potassium chloride for radiation therapy dosimetry

“…Authors have noted: a dynamic range of over 5 orders of magnitude, excellent linearity, no apparent limitation on dose rate, high efficiency, high spatial resolution, no wet chemical processing, digital readout, a low useful dose limit, and large detection areas [7,8,[20][21][22] . Furthermore, the versatility of IPs have led to numerous applications, including autoradiography of weak beta and gamma emitters, such as 14 C, 3 H, and 195m Pt, in mice [23] and agarose gel from electrophoresis [24], non destructive imaging with beta emitters [25], protein crystallography [26], 50 MeV proton beam dosimetry [27], neutron dosimetry [21,28,29], skin entrance dosimetry during interventional radiology [30], integral dosimetry around a cyclotron [31], and quality assurance of kV x ray tubes [32].…”