Direct measurement of clinical mammographic x-ray spectra using a CdTe spectrometer.

PURPOSE: To introduce and evaluate a method developed for the direct measurement of mammographic x-ray spectra using a CdTe spectrometer. The assembly of a positioning system and the design of a simple and customized alignment device for this application is described. METHODS: A positioning system was developed to easily and accurately locate the CdTe detector in the x-ray beam. Additionally, an alignment device to line up the detector with the central axis of the radiation beam was designed. Direct x-ray spectra measurements were performed in two different clinical mammography units and the measured x-ray spectra were compared with computer-generated spectra. In addition, the spectrometer misalignment effect was evaluated by comparing the measured spectra when this device is aligned relatively to when it is misaligned. RESULTS: The positioning and alignment of the spectrometer have allowed the measurements of direct mammographic x-ray spectra in agreement with computer-generated spectra. The most accurate x-ray spectral shape, related with the minimal HVL value, and high photon fluence for measured spectra was found with the spectrometer aligned according to the proposed method. The HVL values derived from both simulated and measured x-ray spectra differ at most 1.3 and 4.5% for two mammography devices evaluated in this study. CONCLUSION: The experimental method developed in this work allows simple positioning and alignment of a spectrometer for x-ray spectra measurements given the geometrical constraints and maintenance of the original configurations of mammography machines.

Optimization of Image Quality and Dose in Digital Mammography.

Nowadays, the optimization in digital mammography is one of the most important challenges in diagnostic radiology. The new digital technology has introduced additional elements to be considered in this scenario. A major goal of mammography is related to the detection of structures on the order of micrometers (µm) and the need to distinguish the different types of tissues, with very close density values. The diagnosis in mammography faces the difficulty that the breast tissues and pathological findings have very close linear attenuation coefficients within the energy range used in mammography. The aim of this study was to develop a methodology for optimizing exposure parameters of digital mammography based on a new Figure of Merit: FOM ≡ (IQFinv)2/AGD, considering the image quality and dose. The study was conducted using the digital mammography Senographe DS/GE, and CDMAM and TORMAM phantoms. The characterization of clinical practice, carried out in the mammography system under study, was performed considering different breast thicknesses, the technical parameters of exposure, and processing options of images used by the equipment's automatic exposure system. The results showed a difference between the values of the optimized parameters and those ones chosen by the automatic system of the mammography unit, specifically for small breast. The optimized exposure parameters showed better results than those obtained by the automatic system of the mammography, for the image quality parameters and its impact on detection of breast structures when analyzed by radiologists.

Riscos da Radiação X e a Importância da Proteção Radiológica na Cardiologia Intervencionista: Uma Revisão Sistemática / Radiation Risks and the Importance of Radiological Protection in Interventional Cardiology: A Systematic Review

Discutimos aqui aspectos vinculados ao enquadramento legal, a recomendações internacionais e a programas de formação em proteção radiológica; ao angiógrafo e à qualidade da imagem; aos efeitos biológicos e aos riscos das radiações ionizantes; às lesões em operadores e pacientes; aos níveis de referência do paciente; ao limite de dose ocupacional e a suas medidas de prevenção. O uso das radiações ionizantes acarreta riscos, que, contudo, justificam-se em procedimentos diagnósticos e terapêuticos. A consciência e o conhecimento desses riscos minimizam o dano, otimizando a qualidade da imagens e o uso seguro das radiações ionizantes. Tem-se demonstrado a ocorrência de cataratas radioinduzidas em trabalhadores de laboratórios de cateterismo. Diversos estudos sugerem que pode haver um risco significativo de opacidade do cristalino, caso não se utilizem adequadamente os dispositivos de proteção radiológica. Adicionalmente, esses tipos de procedimentos intervencionistas são realizados na América Latina, geralmente por médicos especialistas, com a colaboração de enfermeiros, tecnólogos e técnicos, que, muitas vezes, não têm formação adequada em proteção radiológica.

We discuss some aspects related to the legal framework, international recommendations and training programs on radiological protection; image quality and equipment; the biological effects and risks of ionizing radiation; lesions in patients and operators; patient's reference levels; occupational dose limit and preventive actions. The use of ionizing radiation involves risks that are justified in diagnostic and therapeutic procedures. The awareness and knowledge of these risks minimizes the damage, optimizing the quality of images and safe use of ionizing radiation. There is evidence of radiation-induced cataracts in individuals who work in catheterization laboratories. Several studies suggest there may be a significant risk of lens opacity, if radiological protection devices are not properly used. Additionally, these interventional procedures are performed in Latin America, usually by medical specialists in collaboration with nurses, technologists and technicians, who often do not have adequate training in radiological protection.

Espectros de raios-x medicos com fotodiodos Pin: estudo comparativo / Spectra of x-rays measured with Pin photodiode: comparative study

O trabalho apresenta dois modos distintos para a avaliação de espectros de raios-X utilizados em radiodiagnóstico: uma baseada num modelo semi-empírico e outra pela medição através de um fotodiodo PIN de silício. Valores medidos e calculados usando combinações de filtrações e quilovoltagens típicas são comparados.

The work presents two different approaches for the evaluation of diagnostic X-ray spectra: one based on a semiempirical model and other based on measurements made by using a silicon PIN photodiode. Measured and calculated values using typical kVp and filter combinations are compared.

Nova metodologia para implementaçäo de programas de controle de qualidade em departamentos de radiologia diagnóstica / New metodology for implementation of the quality control program im diagnostic radiology department

Programas de Controle de Qualidade foram estudados e repensados para que pudessem embutir um caráter mais permanente e duradouro. Este trabalho voltou-se para um treinamento contínuo de técnicos, adequando sua bagagem cultural à conscientização do conceito de Qualidade.

Quality Control Programmes were studied in order to include a most permanent and durable character. This work is an approach where the continuous training of technicians aims to the suitability of their cultural history to an awareness of the conception of Quality.

Determinaçäo do tamanho do ponto focal de tubos de raios-x: digitalizaçäo direta vs avaliaçäo óptica / Determination of the size of focal point of x-rays tube: direct digitalization versus optical evaluation

Neste trabalho é discutida uma metodologia comparativa entre técnicas convencionais de midição das dimensões do ponto focal de tubos de raios-X e uma nova técnica utilizando recursos para aquisição digital de imagens. São apresentados resultados de medições com ambos os métodos.

This work shows a comparative methodology between standard techniques for evaluation of X-ray tubes focal spots and a newer one which uses digital resources for image acquisition. Results from measurements by using both methods are presented

Avaliaçäo das dimensöes do ponto focal de tubos de raios-x utilizando um sistema de digitalizaçäo direta / Evaluationof of the dimension of focal point of x-rays tube using a direct digitalization system

Um sistema de digitalização de imagens é proposto como método alternativo na substituição de filmes de exposição direta para medição das dimensões de pontos focais de tubos de raios-X utilizados em radiodiagnóstico. Resultados de medições são apresentados e comparados aos valores nominais.

An image digitalization system is proposed as an alternative method for replacing direct exposure X-ray films on the evaluation of dimensions of diagnostic X-ray tube focal spots. Results of measurements are presented and compared to nominal values.