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.

STIR, SPIR and SPAIR techniques in magnetic resonance of the breast: a comparative study

The amount of fat is a component that complicates the clinical evaluation and the differential diagnostic between benign and malign lesions in the breast MRI examinations. To overcome this problem, an effective erasing of the fat signal over the images acquisition process, is essentials. This study aims to compare three fat suppression techniques (STIR, SPIR, SPAIR) in the MR images of the breast and to evaluate the best image quality regarding its clinical usefulness. To mimic breast women, a breast phantom was constructed. First the exterior contour and, in second time, its content which was selected based on 7 samples with different components. Finally it was undergone to a MRI breast protocol with the three different fat saturation techniques. The examinations were performed on a 1.5 T MRI system (Philips®). A group of 5 experts evaluated 9 sequences, 3 of each with fat suppression techniques, in which the frequency offset and TI (Inversion Time) were the variables changed. This qualitative image analysis was performed according 4 parameters (saturation uniformity, saturation efficacy, detail of the anatomical structures and differentiation between the fibroglandular and adipose tissue), using a five-point Likert scale. The statistics analysis showed that anyone of the fat suppression techniques demonstrated significant differences compared to the others with (p > 0.05) and regarding each parameter independently. By Fleiss’ kappa coefficient there was a good agreement among observers P(e) = 0.68. When comparing STIR, SPIR and SPAIR techniques it was confirmed that all of them have advantages in the study of the breast MRI. For the studied parameters, the results through the Friedman Test showed that there are similar advantages applying anyone of these techniques.

Hélices e Espirais em Micro e Nanofibras Celulósicas

A celulose é o polímero renovável mais abundante do mundo. É conhecido pela sua excelente biocompatibilidade, propriedades térmicas e mecânicas. A celulose assim como os polipéptideos e o ADN, pertence a uma família de moléculas orgânicas que dão origem à formação de fases líquidas cristalinas (LCs) colestéricas. A Passiflora Edulis, tal como outras plantas trepadeiras, possui longas e flexíveis gavinhas que permitem à planta encontrar um suporte para se fixar. As gavinhas podem assumir a forma de espirais ou de hélices consoante sejam sustentadas por apenas uma ou por ambas as extremidades. As hélices apresentam muitas vezes duas porções helicoidais, uma esquerda e outra direita, separadas por um segmento recto denominado perversão. Este comportamento é consequência da curvatura intrínseca das gavinhas produzidas pela planta trepadeira. O mesmo comportamento pode ser observado em micro e nanofibras celulósicas fabricadas a partir de soluções líquido-cristalinas, numa escala três a quatro ordens de grandeza inferior à das gavinhas. Este facto sugere que o modelo físico utilizado tenha invariância de escala. Neste trabalho é feito o estudo de fibras e jactos que imitam as estruturas helicoidais apresentadas pelas gavinhas das plantas trepadeiras. As fibras e jactos são produzidos a partir de soluções líquidas cristalinas celulósicas. De modo a determinar as características morfológicas e estruturais, que contribuem para a curvatura das fibras, foram utilizadas técnicas de imagem por ressonância magnética (MRI), microscopia óptica com luz polarisada (MOP), microscopia electrónica de varrimento (SEM) e microscopia de força atómica (AFM) . A variação da forma das estruturas helicoidais com a temperatura parece ser relevante para o fabrico de membranas não tecidas para aplicação em sensores termo-mecânicos.

Análise quantitativa da saturação de gordura em ressonância magnética mamária: comparação das técnicas SPAIR e DIXON

Introdução – A ressonância magnética (RM) mamária com injeção de contraste é uma ferramenta indispensável para a caracterização de lesões mamárias. Para tal, é fulcral uma boa capacidade de saturação de gordura de forma a delimitar as lesões observadas. Este trabalho tem como objetivo analisar quantitativa e qualitativamente as técnicas de saturação de gordura em RM mamária, nomeadamente as técnicas SPAIR e Dixon. Metodologia – Utilizou-se um equipamento de RM de 1,5T com bobina específica para a mama. Aplicou-se, durante o exame, uma sequência adicional em que a técnica de saturação de gordura utilizada foi a Dixon. Posteriormente foram analisadas as imagens obtidas com as técnicas SPAIR e Dixon e colocadas regiões de interesse (ROI) na lesão, na glândula mamária, no tecido adiposo e no ar. Estes valores de sinal obtidos foram registados e calcularam-se as relações sinal-ruído (SNR), contraste-ruído (CNR) e uniformidade de saturação de gordura para as mesmas estruturas a analisar e nas distintas sequências. Resultados – Verificou-se que a técnica de supressão de gordura Dixon apresenta resultados quantitativos e qualitativos superiores à técnica SPAIR. Conclusões – Recomenda-se a utilização da técnica Dixon para saturação de gordura nas sequências de estudo dinâmico com agente de contraste, especificamente nos estudos de RM mamária.

Morfometria do trato vocal por ressonância magnética: simulação de padrões patológicos articulatórios

Introdução – A análise da forma ou morfometria de estruturas anatómicas, como o trato vocal, pode ser efetuada a partir de imagens bidimensionais (2D) como de aquisições volumétricas (3D) de ressonância magnética (RM). Esta técnica de imagem tem vindo a ter uma utilização crescente no estudo da produção da fala. Objetivos – Demonstrar como pode ser efetuada a morfometria do trato vocal a partir da imagem por ressonância magnética e ainda apresentar padrões anatómicos normais durante a produção das vogais [i a u] e dois padrões articulatórios patológicos em contexto simulado. Métodos – As imagens consideradas foram recolhidas a partir de aquisições 2D (Turbo Spin-eco) e 3D (Flash Gradiente-Eco) de RM em quatro sujeitos durante a produção das vogais em estudo; adicionalmente procedeu-se à avaliação de duas perturbações articulatórias usando o mesmo protocolo de RM. A morfometria do trato vocal foi extraída com recurso a técnicas manuais (para extração de cinco medidas articulatórias) e automáticas (para determinação de volumes) de processamento e análise de imagem. Resultados – Foi possível analisar todo o trato vocal, incluindo a posição e a forma dos articuladores, tendo por base cinco medidas descritivas do posicionamento destes órgãos durante a produção das vogais. A determinação destas medições permitiu identificar quais as estratégias mais comummente adotadas na produção de cada som, nomeadamente a postura articulatória e a variação de cada medida para cada um dos sujeitos em estudo. No contexto de voz falada intersujeitos, foi notória a variabilidade nos volumes estimados do trato vocal para cada som e, em especial, o aumento do volume do trato vocal na perturbação articulatória de sigmatismo. Conclusão – A imagem por RM é, sem dúvida, uma técnica promissora no estudo da fala, inócua, não-invasiva e que fornece informação fiável da morfometria do trato vocal.

Three-dimensional modeling of tongue during speech using MRI data

The tongue is the most important and dynamic articulator for speech formation, because of its anatomic aspects (particularly, the large volume of this muscular organ comparatively to the surrounding organs of the vocal tract) and also due to the wide range of movements and flexibility that are involved. In speech communication research, a variety of techniques have been used for measuring the three-dimensional vocal tract shapes. More recently, magnetic resonance imaging (MRI) becomes common; mainly, because this technique allows the collection of a set of static and dynamic images that can represent the entire vocal tract along any orientation. Over the years, different anatomical organs of the vocal tract have been modelled; namely, 2D and 3D tongue models, using parametric or statistical modelling procedures. Our aims are to present and describe some 3D reconstructed models from MRI data, for one subject uttering sustained articulations of some typical Portuguese sounds. Thus, we present a 3D database of the tongue obtained by stack combinations with the subject articulating Portuguese vowels. This 3D knowledge of the speech organs could be very important; especially, for clinical purposes (for example, for the assessment of articulatory impairments followed by tongue surgery in speech rehabilitation), and also for a better understanding of acoustic theory in speech formation.

Learner’s satisfaction within a breast imaging eLearning course for radiographers

Background: An asynchronous eLearning system was developed for radiographers in order to promote a better knowledge about senology and mammography. Objectives: to assess the learners’ satisfaction. Methods: Target population included radiographers and radiogr aphy students, in order to assess eLearning satisfaction according to different experience levels in breast imaging. Satisfaction was measured through a questionnaire developed especially for eLearning systems, using a seven - point Likert scale. Main topics related are content, interface, personalization and learning community. Results: Overall, 85% of learners were satisfied with the course and 87,5% considered that the course is successful. Main areas that were evaluated by most learners in a positive way were interface and content (between six and seven - point); on the other hand, learning community presented a wider distribution of answers . Conclusions: The course provides an overall high degree of learner satisfaction, thus providing more effective knowle dge gain on breast imaging for radiographers.

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.

Determination of free furfuryl alcohol in foundry resins by chromatographic techniques

Two chromatographic methods, gas chromatography with flow ionization detection (GC–FID) and liquid chromatography with ultraviolet detection (LC–UV), were used to determine furfuryl alcohol in several kinds of foundry resins, after application of an optimised extraction procedure. The GC method developed gave feasibility that did not depend on resin kind. Analysis by LC was suitable just for furanic resins. The presence of interference in the phenolic resins did not allow an appropriate quantification by LC. Both methods gave accurate and precise results. Recoveries were >94%; relative standard deviations were ≤7 and ≤0.3%, respectively for GC and LC methods. Good relative deviations between the two methods were found (≤3%).

Chromatographic techniques for the determination of free phenol in foundry resins

Phenol is a toxic compound present in a wide variety of foundry resins. Its quantification is important for the characterization of the resins as well as for the evaluation of free contaminants present in foundry wastes. Two chromatographic methods, liquid chromatography with ultraviolet detection (LC-UV) and gas chromatography with flame ionization detection (GC-FID), for the analysis of free phenol in several foundry resins, after a simple extraction procedure (30 min), were developed. Both chromatographic methods were suitable for the determination of phenol in the studied furanic and phenolic resins, showing good selectivity, accuracy (recovery 99–100%; relative deviations <5%), and precision (coefficients of variation <6%). The used ASTM reference method was only found to be useful in the analysis of phenolic resins, while the LC and GC methods were applicable for all the studied resins. The developed methods reduce the time of analysis from 3.5 hours to about 30 min and can readily be used in routine quality control laboratories.

Relatório de estágio de natureza profissional em PET/CT: Clinical Imaging Sciences Centre, Sussex

Mestrado em Medicina Nuclear - Ramo de especialização: Tomografia por Emissão de Positrões

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

Background - Pelvis and hip radiography are consistently found to be amongst the highest contributors to the collective effective dose (E) in all ten DOSE DATAMED countries in Europe, representing 2.8 to 9.4% of total collective dose (S) in the TOP 20 exams list. The level of image quality should provide all the diagnostic information in order not to jeopardise the diagnosis, but being able to provide the needed clinical information with the minimum dose. A recent study suggests further research to determine whether the “10 kVp rule” would have value for a range of examinations using Computed Radiography (CR) systems. As a “rule of thumb” increasing the kVp by 10 whilst halving the mAs is suggested to give a similar perceptual image quality when compared to the original exposure factors. Aims - In light of the 10kVp rule, this study aims to investigate the influence of tube potential (kVp) variation in relation to perceptual image quality and E for pelvis imaging using automatic exposure control (AEC) and non-AEC in a Computed Radiography (CR) system. Research questions - Does the 10kVp rule works for the pelvis in relation to image quality in a CR system? Does the image quality differs when the AEC is used instead of manual mode using the 10kVp rule and how this impacts on E?

Análise quantitativa da saturação de gordura em ressonância magnética mamária: comparação das técnicas SPAIR e DIXON

Mestrado em Radiações Aplicadas às Tecnologias da Saúde - Ramo de especialização: Ressonância Magnética

Implementação do protocolo eNAL num serviço de radioterapia: um estudo de caso

Mestrado em Radioterapia

Effects of emotional valence and three-dimensionality of visual stimuli on brain activation: an fMRI study

BACKGROUND: Examining changes in brain activation linked with emotion-inducing stimuli is essential to the study of emotions. Due to the ecological potential of techniques such as virtual reality (VR), inspection of whether brain activation in response to emotional stimuli can be modulated by the three-dimensional (3D) properties of the images is important. OBJECTIVE: The current study sought to test whether the activation of brain areas involved in the emotional processing of scenarios of different valences can be modulated by 3D. Therefore, the focus was made on the interaction effect between emotion-inducing stimuli of different emotional valences (pleasant, unpleasant and neutral valences) and visualization types (2D, 3D). However, main effects were also analyzed.METHODS: The effect of emotional valence and visualization types and their interaction were analyzed through a 3x2 repeated measures ANOVA. Post-hoc t-tests were performed under a ROI-analysis approach. RESULTS: The results show increased brain activation for the 3D affective-inducing stimuli in comparison with the same stimuli in 2D scenarios, mostly in cortical and subcortical regions that are related to emotional processing, in addition to visual processing regions. CONCLUSIONS: This study has the potential of clarify brain mechanisms involved in the processing of emotional stimuli (scenarios’ valence) and their interaction with three-dimensionality.