Technical considerations concerning digital technologies

This chapter addresses technical issues concerning digital technologies. Radiological equipment and technique are briefly introduced together with a discussion about requirements and advantages of digital technologies. Digital technologies offer several advantages when compared to conventional analogical systems, or screen–film (SF) systems. While in clinical practice the practitioners should be aware of technical factors such as image acquisition, management of patient dose, and diagnostic image quality. Thus, digital technologies require an up-to-date scientific knowledge concerning their use in projection radiography. In this chapter, technical considerations concerning digital technologies are provided.

Assessment of patient dose in digital systems

The assessment of patient dose has gained increased attention, still being an issue of concern that arises from the use of digital systems. The development of digital technology offers the possibility for a reduction of radiation dose around 50% without loss in image quality when compared to a conventional screen–film system. Digital systems give an equivalent or superior diagnostic performance and also several other advantages, but the risk of overexposure with no adverse effect on image quality could be present. This chapter refers to the management of patient dose and provides an explanation of dose-related concepts. In this chapter, exposure influence in dose and image representation and the effects of radiation exposure are also discussed.

Image quality in diagnostic radiology

This chapter provides a theoretical background about image quality in diagnostic radiology. Digital image representation and also image quality evaluation methods are here discussed. An overview of methods for quality evaluation of diagnostic imaging procedures is provided. Digital image representation and primary physical image quality parameters are also discussed, including objective image quality measurements and observer performance methods.

Practical insights into digital radiology

Digital radiography detectors—based on different technological solutions—are currently available for clinical applications and widespread in clinical practice. Computed radiography (CR) and digital radiology systems have been available for clinical applications and the trend over the last few years has become digital. Radiology departments have been changing from traditional screen–film technology to digital technology. This chapter is intended to give the reader a practical understanding about the key aspects concerning digital systems, related to the performance of different technologies, image quality, and dose and patient safety/protection. The discussion around an optimization framework for digital systems is provided.

Digital radiology and Picture Archiving and Communication System (PACS)

Plain radiography still accounts for the vast majority of imaging studies that are performed at multiple clinical instances. Digital detectors are now prominent in many imaging facilities and they are the main driving force towards filmless environments. There has been a working paradigm shift due to the functional separation of acquisition, visualization, and storage with deep impact in the imaging workflows. Moreover with direct digital detectors images are made available almost immediately. Digital radiology is now completely integrated in Picture Archiving and Communication System (PACS) environments governed by the Digital Imaging and Communications in Medicine (DICOM) standard. In this chapter a brief overview of PACS architectures and components is presented together with a necessarily brief account of the DICOM standard. Special focus is given to the DICOM digital radiology objects and how specific attributes may now be used to improve and increase the metadata repository associated with image data. Regular scrutiny of the metadata repository may serve as a valuable tool for improved, cost-effective, and multidimensional quality control procedures.

Estudo de caso. A implementação do projeto de internalização do RX do Centro de Diagnóstico Pneumológico do Porto

Portugal atravessa uma crise económico-financeira. A austeridade económica é prioritária, e a área de saúde não é exceção. Nesta conjuntura justifica-se de todo a realização de análises económicas na saúde. Este estudo é uma análise custo - mínimo ao Projeto de Internalização do RX do Centro Diagnóstico Pneumológico (CDP) do Porto com o objetivo de rentabilizar o equipamento radiológico instalado no CDP do Porto, pretende-se usar a capacidade máxima instalada e permitida pelo equipamento para produção de radiografias a utentes provenientes dos Agrupamentos de Centros de Saúde (ACES) do Porto. O Projeto de Internalização do RX do CDP do Porto é um projeto da Administração Regional de Saúde (ARS) do Norte, que pretende encaminhar os utentes dos ACES do Porto para realização de exames radiográficos no RX do CDP do Porto. Para proceder à análise económica foram identificados os custos e os benefícios relevantes do RX do CDP do Porto e elaboradas 3 estimativas: 1. Realização dos exames radiográficos do CDP do Porto a utentes do CDP do Porto e realização de exames radiográficos a utentes dos ACES do Porto nos gabinetes de radiologia convencionados pela ARSNorte; 2. Projeto de Internalização do RX do CDP do Porto com realização dos exames radiográficos até esgotar a capacidade máxima instalada do equipamento radiológico com recurso a utentes dos ACES do Porto; 3. Realização dos exames radiográficos nos ACES do Porto e dos exames do CDP do Porto nos gabinetes de radiologia convencionados. Os resultados da análise levaram à conclusão que a implementação do Projeto de Internalização do RX do Porto é rentável, ou seja, o projeto permitirá ganhos financeiros para a ARSNorte se for implementado na sua plenitude.

Trypanosoma cruzi prevalence and clinical forms in blood donor candidates in Brazil

The prevalence and clinical forms of Trypanosoma cruzi were evaluated among blood donor candidates attended at a general hospital in Rio de Janeiro, Brazil, from January 1997 to April 1999. The investigation was done by means of the indirect hemagglutination test and was confirmed via ELISA. Data were collected from clinical examinations, conventional electrocardiogram, chest radiography and echocar-diography. The results showed that despite Trypanosoma cruzi prevalence of 1.17% (128 patients), mainly in males aged 40 years or over, 70.8% of these patients, mainly males aged 19 to 39 years, demonstrated abnormalities that allowed the diagnosis of cardiopathy and/or esophagopathy. This once again corroborates the importance of Trypanosoma cruzi infection in urban centers.

Radiographic outcomes and evaluation of developmental dysplasia of the hip in children

The Developmental Dysplasia of the Hip (DDH), also know as Congenital Dislocation of the Hip, is common in infants and children and may persist into adulthood. The radiographic interpretation is highly conditioned by appropriate patient positioning and image quality criteria. The main goal of this study is to demonstrate the value of radiographic evaluation of DDH. Through the retrospective analysis of 65 radiographs of the hips, only 2 (3.1%) female patients with 1-2 years of age presented radiographic findings of DDH. The inappropriate field size and the improper placement and size of the gonadal shields, were the most common errors observed.

Avaliação da margem do PTV em tumores ginecológicos com irradiação dos gânglios lomboaórticos, que realizaram IMRT

Mestrado em Radioterapia.

Results of radiation protection programmes on mammography

In this paper, we present the results of mammography quality control tests related to the work with Portuguese mammography equipment, either in conventional or in digital mammography computed radiography, showing the main differences in the tested equipments. Quality control in mammography is a very special area of quality control in radiology, which demands relatively high knowledge on physics. Digital imaging is changing the standards of the radiographic imaging. Regarding mammography, this is yet a controversial issue owing to some limitations of the digital detectors, like the resolution for instance. A complete set of results regarding radiation protection of the patients submitted to mammography diagnosis is presented. A discussion of the quality image parameters and its interpretation in conventional and digital mammography is presented. In conclusion, we present a sample of results that can be considered as characteristics of mammography equipment in Portugal.

10 kVp rule – An anthropomorphic pelvis phantom imaging study using a CR system: impact on image quality and effective dose using AEC and manual mode

Purpose - This study aims to investigate the influence of tube potential (kVp) variation in relation to perceptual image quality and effective dose (E) for pelvis using automatic exposure control (AEC) and non-AEC in a Computed Radiography (CR) system. Methods and materials - To determine the effects of using AEC and non-AEC by applying the 10 kVp rule in two experiments using an anthropomorphic pelvis phantom. Images were acquired using 10 kVp increments (60–120 kVp) for both experiments. The first experiment, based on seven AEC combinations, produced 49 images. The mean mAs from each kVp increment were used as a baseline for the second experiment producing 35 images. A total of 84 images were produced and a panel of 5 experienced observers participated for the image scoring using the two alternative forced choice (2AFC) visual grading software. PCXMC software was used to estimate E. Results - A decrease in perceptual image quality as the kVp increases was observed both in non-AEC and AEC experiments, however no significant statistical differences (p > 0.05) were found. Image quality scores from all observers at 10 kVp increments for all mAs values using non-AEC mode demonstrates a better score up to 90 kVp. E results show a statistically significant decrease (p = 0.000) on the 75th quartile from 0.37 mSv at 60 kVp to 0.13 mSv at 120 kVp when applying the 10 kVp rule in non-AEC mode. Conclusion - Using the 10 kVp rule, no significant reduction in perceptual image quality is observed when increasing kVp whilst a marked and significant E reduction is observed.

Para uma leitura não biográfica da obra de Mário de Sá Carneiro (e uma apreciação de o modernismo em Mário de Sá-Carneiro de Fernando Cabral Martins)

Este artigo pretende sublinhar a importância de entender a obra de Mário de Sá- Carneiro através de uma leitura atenta da sua produção literária que não procura provas da “veracidade” dessa leitura na biografia do poeta do Orpheu. Partindo de uma análise do trabalho crítico de Fernando Cabral Martins, levanta-se a problemática de deturpar uma análise de crítica literária com abordagens influenciadas por normas de história da literatura que inserem a obra no seu contexto histórico, o que tem sido o caso na recepção da obra de Sá-Carneiro, onde o mito do autor tende a ofuscar o seu legado literário. Assim, este artigo questiona se em O Modernismo em Mário de Sá-Carneiro, Fernando Cabral Martins consegue libertar a obra sá-carneiriana da sombra do poeta biográfico, e oferece uma avaliação panorâmica da tradição crítica dedicada ao autor, apontando para casos de interpretações que se prenderam com questões que ficam para fora do texto, como tem sido o caso com a natureza homossexual da obra e do homem.

Development and validation of a psychometric scale for assessing PA chest image quality: a pilot study

Purpose - To develop and validate a psychometric scale for assessing image quality perception for chest X-ray images. Methods - Bandura's theory was used to guide scale development. A review of the literature was undertaken to identify items/factors which could be used to evaluate image quality using a perceptual approach. A draft scale was then created (22 items) and presented to a focus group (student and qualified radiographers). Within the focus group the draft scale was discussed and modified. A series of seven postero-anterior chest images were generated using a phantom with a range of image qualities. Image quality perception was confirmed for the seven images using signal-to-noise ratio (SNR 17.2–36.5). Participants (student and qualified radiographers and radiology trainees) were then invited to independently score each of the seven images using the draft image quality perception scale. Cronbach alpha was used to test interval reliability. Results - Fifty three participants used the scale to grade image quality perception on each of the seven images. Aggregated mean scale score increased with increasing SNR from 42.1 to 87.7 (r = 0.98, P < 0.001). For each of the 22 individual scale items there was clear differentiation of low, mid and high quality images. A Cronbach alpha coefficient of >0.7 was obtained across each of the seven images. Conclusion - This study represents the first development of a chest image quality perception scale based on Bandura's theory. There was excellent correlation between the image quality perception scores derived using the scale and the SNR. Further research will involve a more detailed item and factor analysis.

Image quality and dose analysis for a PA chest X-ray: comparison between AEC mode acquisition and manual mode using the 10 kVp ‘rule’

Purpose - To compare the image quality and effective dose applying the 10 kVp rule with manual mode acquisition and AEC mode in PA chest X-ray. Method - 68 images (with and without lesions) were acquired using an anthropomorphic chest phantom using a Wolverson Arcoma X-ray unit. These images were compared against a reference image using the 2 alternative forced choice (2AFC) method. The effective dose (E) was calculated using PCXMC software using the exposure parameters and the DAP. The exposure index (lgM provided by Agfa systems) was recorded. Results - Exposure time decreases more when applying the 10 kVp rule with manual mode (50%–28%) when compared with automatic mode (36%–23%). Statistical differences for E between several ionization chambers' combinations for AEC mode were found (p = 0.002). E is lower when using only the right AEC ionization chamber. Considering the image quality there are no statistical differences (p = 0.348) between the different ionization chambers' combinations for AEC mode for images with no lesions. Considering lgM values, it was demonstrated that they were higher when the AEC mode was used compared to the manual mode. It was also observed that lgM values obtained with AEC mode increased as kVp value went up. The image quality scores did not demonstrate statistical significant differences (p = 0.343) for the images with lesions comparing manual with AEC mode. Conclusion - In general the E is lower when manual mode is used. By using the right AEC ionising chamber under the lung the E will be the lowest in comparison to other ionising chambers. The use of the 10 kVp rule did not affect the visibility of the lesions or image quality.

Increasing source to image distance for AP pelvis imaging: impact on radiation dose and image quality

Aim - A quantative primary study to determine whether increasing source to image distance (SID), with and without the use of automatic exposure control (AEC) for antero-posterior (AP) pelvis imaging, reduces dose whilst still producing an image of diagnostic quality. Methods - Using a computed radiography (CR) system, an anthropomorphic pelvic phantom was positioned for an AP examination using the table bucky. SID was initially set at 110 cm, with tube potential set at a constant 75 kVp, with two outer chambers selected and a fine focal spot of 0.6 mm. SID was then varied from 90 cm to 140 cm with two exposures made at each 5 cm interval, one using the AEC and another with a constant 16 mAs derived from the initial exposure. Effective dose (E) and entrance surface dose (ESD) were calculated for each acquisition. Seven experienced observers blindly graded image quality using a 5-point Likert scale and 2 Alternative Forced Choice software. Signal-to-Noise Ratio (SNR) was calculated for comparison. For each acquisition, femoral head diameter was also measured for magnification indication. Results - Results demonstrated that when increasing SID from 110 cm to 140 cm, both E and ESD reduced by 3.7% and 17.3% respectively when using AEC and 50.13% and 41.79% respectively, when the constant mAs was used. No significant statistical (T-test) difference (p = 0.967) between image quality was detected when increasing SID, with an intra-observer correlation of 0.77 (95% confidence level). SNR reduced slightly for both AEC (38%) and no AEC (36%) with increasing SID. Conclusion - For CR, increasing SID significantly reduces both E and ESD for AP pelvis imaging without adversely affecting image quality.