Is there a need for attenuation correction in the 99mTc-DMSA scans on pediatric patients?

Introduction: The quantification of th e differential renal function in adults can be difficult due to many factors - on e of the se is the variances in kidney depth and the attenuation related with all the tissue s between the kidney and the camera. Some authors refer that t he lower attenuation i n p ediatric patients makes unnecessary the use of attenuation correction algorithms. This study will com pare the values of differential renal function obtained with and with out attenuation correction techniques . Material and Methods: Images from a group consisting of 15 individuals (aged 3 years +/ - 2) were used and two attenuation correction method s were applied – Tonnesen correction factors and the geometric mean method . The mean time of acquisition (time post 99m Tc - DMSA administration) was 3.5 hours +/ - 0.8h. Results: T he absence of any method of attenuation correction apparently seems to lead to consistent values that seem to correlate well with the ones obtained with the incorporation of methods of attenuation correction . The differences found between the values obtained with and without attenuation correction were not significant. Conclusion: T he decision of not doing any kind of attenuation correction method can apparently be justified by the minor differences verified on the relative kidney uptake values. Nevertheless, if it is recognized that there is a need for a really accurate value of the relative kidney uptake, then an attenuation correction method should be used.

FMRI 3D registration based on Fourier space subsets using neural networks

In this work, we present a neural network (NN) based method designed for 3D rigid-body registration of FMRI time series, which relies on a limited number of Fourier coefficients of the images to be aligned. These coefficients, which are comprised in a small cubic neighborhood located at the first octant of a 3D Fourier space (including the DC component), are then fed into six NN during the learning stage. Each NN yields the estimates of a registration parameter. The proposed method was assessed for 3D rigid-body transformations, using DC neighborhoods of different sizes. The mean absolute registration errors are of approximately 0.030 mm in translations and 0.030 deg in rotations, for the typical motion amplitudes encountered in FMRI studies. The construction of the training set and the learning stage are fast requiring, respectively, 90 s and 1 to 12 s, depending on the number of input and hidden units of the NN. We believe that NN-based approaches to the problem of FMRI registration can be of great interest in the future. For instance, NN relying on limited K-space data (possibly in navigation echoes) can be a valid solution to the problem of prospective (in frame) FMRI registration.

3D-2D image registration by nonlinear regression

We propose a 3D-2D image registration method that relates image features of 2D projection images to the transformation parameters of the 3D image by nonlinear regression. The method is compared with a conventional registration method based on iterative optimization. For evaluation, simulated X-ray images (DRRs) were generated from coronary artery tree models derived from 3D CTA scans. Registration of nine vessel trees was performed, and the alignment quality was measured by the mean target registration error (mTRE). The regression approach was shown to be slightly less accurate, but much more robust than the method based on an iterative optimization approach.

A sustentabilidade das finanças públicas das regiões autónomas portuguesas

Dissertação de Mestrado em Ciências Económicas e Empresariais

Estrutura da boa vida em pessoas com doença crónica

Doenças crónicas (DC) são doenças que têm de ser geridas em vez de curadas. Giovannini, Bitti, Sarchielli e Speltini (1986) caracterizam as doenças crónicas como: a) doenças de longa duração, b) que tendem a prolongar-se por toda a vida do doente, c) que provocam invalidez em graus variáveis, d) são devidas a causas não reversíveis, e) que exigem formas particulares de reeducação, f) que obrigam o doente a seguir determinadas prescrições terapêuticas, g) que normalmente exigem a aprendizagem de um novo estilo de vida, h) que necessitam de controlo periódico, de observação e de tratamento regulares. As DC não se definem pela sua aparente ou real gravidade. As pessoas que têm DC podem fazer a vida do dia-a-dia como qualquer outro cidadão, e grande parte deles acaba por falecer de velhice ou de outras doenças, que não a DC que os acompanhou grande parte da vida. Para estas pessoas viverem uma boa vida o processo de ajustamento é decisivo. O ajustamento à DC torna-se então um objectivo fundamental para as pessoas e para a sociedade. O ajustamento pode definir-se como uma resposta a uma alteração do meio ambiente, que leva um organismo a adaptar-se a essa alteração. Esta definição, explicam as autoras, implica que ele ocorre ao longo do tempo e, também, que é um resultado desejável. Para Stanton, Revenson, e Tennen, (2007), o ajustamento engloba inúmeros componentes que cruzam domínios interpessoais, cognitivos, emocionais, físicos e comportamentais. Estes autores referem que da revisão da literatura se pode concluir que, grosso modo a DC requer, ajustamento em múltiplos domínios, que o ajustamento se desenrola ao longo do tempo, e que existe uma heterogeneidade acentuada no modo como os indivíduos se ajustam à DC. O ajustamento é um conceito do senso comum que tanto é verbo como substantivo.

O ajustamento à doença crónica: aspectos conceptuais

Quando alguém é afectado por uma doença crónica tem que alterar o seu estilo de vida de modo a poder viver o melhor possível com a doença que o vai acompanhar, se não durante toda a vida, pelo menos durante grande parte da vida. Em função das características pessoais e da interacção como o meio envolvente, social e físico, alguns ajustar-se-ão melhor e mais facilmente do que outros. Estas alterações denominam-se Ajustamento ou Adaptação. Embora estes termos sejam sinónimos, por vezes a denominação expressa orientação teórica diferente: a primeira, mais interactiva, para designar o comportamento resultante dessa interacção, momento a momento, com o meio envolvente, a segunda mais estrutural. “Ajustamento” é um termo do senso comum, utilizado na linguagem de todos os dias. O dicionário diz que ajustamento e adaptação são sinónimos e, em contexto de psicologia, saúde e doenças, os dois termos também são utilizados como sinónimos. No entanto, na psicologia, por vezes, estes termos podem expressar conceitos diferentes, consoante a orientação teórica que os utiliza. O interesse pela mudança subjacente ao ajustamento ou à adaptação considera dois aspectos: a estrutura e o processo. A estrutura refere-se a factores estáveis tais como a traços de personalidade ou estrutura cognitiva e, também, a características estáveis do meio ambiente, enquanto o processo refere-se às mudanças que vão ocorrendo em consequência das interacções, momento a momento, com as situações que surgem, explicam Lazarus e Folkman (1985).

Evaluation of 99mTc-Sestamibi as a potential tool to investigate PgP activity in inflammation

Introduction: In the XXI Century ’s Society the scientific investigation process has been growing steadily , and the field of the pharmaceutical research is one of the most enthusiastic and relevant . Here, it is very important to correlate observed functional alterations with possibly modified drug bio distribution patterns . Cancer, inflammation and inf ection are processes that induce many molecular intermediates like cytokines, chemokines and other chemical complexes that can alter the pharmacokinetics of many drugs. One cause of such changes is thought to be the modulator action of these complexes in t he P - Glyco p rotein activity, because they can act like inducers/inhibitors of MDR - 1 expression. This protein results from the expression of MDR - 1 gene, and acts as an ATP energy - dependent efflux pump, with their substrates including many drugs , like antiretrovirals, anticancers, anti - infectives, immunosuppressants, steroids or opioids . Objectives: Because of the lack of methods to provide helpful information in the investigation of in vivo molecular changes in Pgp activity during infection/infl ammation processes, and its value in the explanation of the altered drug pharmacokinetic, this paper want to evaluate the potential utility of 99m Tc - Sestamibi scintigraphy during this kind of health sciences investigation. Although the a im is indeed to create a technique to the in vivo study of Pgp activity, this preliminary Project only reaches the in vitro study phase, assumed as the first step in a n evaluation period for a new tool development. Materials and Methods: For that reason , we are performing in vitro studies of influx and efflux of 99m Tc - Sestamibi ( that is a substrate of Pgp) in hepatocytes cell line (HepG2). We are interested in clarify the cellular behavior of this radiopharmaceutical in Lipopolysaccharide(LPS) stimulated cells ( well known in vitro model of inflammation) to possibly approve this methodology. To validate the results, the Pgp expression will be finally evaluated using Western Blot technique. Results: Up to this moment , we still don’t have the final results, but we have already enough data to let us believe that LPS stimulation induce a downregulation of MDR - 1, and consequently Pgp, which could conduce to a prolonged retention of 99m Tc - Sestamibi in the inflamed cells . Conclusions: If and when this methodology demonstrate the promising results we expect, one will be able to con clude that Nuclear Medicine is an important tool to help evidence based research also on this specific field .

Contribuição para o desenvolvimento e a implementação do sistema de planeamento de emergência na Região Autónoma dos Açores

Dissertação de Mestrado em Vulcanologia e Riscos Geológicos

Cyclotech - contribution to solve the Technetium shortage by using low energy medical cyclotrons

This paper presents work in progress, to develop an efficient and economic way to directly produce Technetium 99metastable (99mTc) using low-energy cyclotrons. Its importance is well established and relates with the increased global trouble in delivering 99mTc to Nuclear Medicine Departments relying on this radioisotope. Since the present delivery strategy has clearly demonstrated its intrinsic limits, our group decided to follow a distinct approach that uses the broad distribution of the low energy cyclotrons and the accessibility of Molybdenum 100 (100Mo) as the Target material. This is indeed an important issue to consider, since the system here presented, named CYCLOTECH, it is not based on the use of Highly Enriched (or even Low Enriched) Uranium 235 (235U), so entirely complying with the actual international trends and directives concerning the use of this potential highly critical material. The production technique is based on the nuclear reaction 100Mo (p,2n) 99mTc whose production yields have already been documented. Until this moment two Patent requests have already been submitted (the first at the INPI, in Portugal, and the second at the USPTO, in the USA); others are being prepared for submission on a near future. The object of the CYCLOTECH system is to present 99mTc to Nuclear Medicine radiopharmacists in a routine, reliable and efficient manner that, remaining always flexible, entirely blends with established protocols. To facilitate workflow and Radiation Protection measures, it has been developed a Target Station that can be installed on most of the existing PET cyclotrons and that will tolerate up to 400 μA of beam by allowing the beam to strike the Target material at an adequately oblique angle. The Target Station permits the remote and automatic loading and discharge of the Targets from a carriage of 10 Target bodies. On other hand, several methods of Target material deposition and Target substrates are presented. The object was to create a cost effective means of depositing and intermediate the target material thickness (25 - 100μm) with a minimum of loss on a substrate that is able to easily transport the heat associated with high beam currents. Finally, the separation techniques presented are a combination of both physical and column chemistry. The object was to extract and deliver 99mTc in the identical form now in use in radiopharmacies worldwide. In addition, the Target material is recovered and can be recycled.

Determination of the radiochemical purity of 99mTc-Tetrofosmin: comparision between five methods

GOAL: The manufacturing and distribution of strips of instant thin - layer chromatography with silica gel (ITLC - SG) (reference method) is currently discontinued so there is a need for an alternative method f or the determination of radiochemical purity (RCP) of 99m Tc - tetrofosmin. This study aims to compare five alternative methods proposed by the producer to determine the RCP of 99m Tc - tetrofosmin. METHODS: Nineteen vials of tetrofosmin were radiolabelled with 99m Tc and the percentages of the RCP were determined. Five different methods were compared with the standard RCP testing method (ITLC - SG, 2x20 cm): Whatman 3MM (1x10 cm) with acetone and dichloro - methane (method 1); Whatman 3MM (1x1 0 cm) with ethyl acetate (method 2); aluminum oxide - coated plastic thin - layer chromatography (TLC) plate (1x10 cm) and ethanol (method 3); Whatman 3MM (2x20 cm) with acetone and dichloro - methane (method 4); solid - phase extraction method C18 cartridge (meth od 5). RESULTS: The average values of RCP were 95,30% ± 1,28% (method 1), 93,95 ± 0,61% (method 2), 96,85% ± 0,93% (method 3), 92,94% ± 0,99% (method 4) and 96,25% ± 2,57% (method 5) (n=12 each), and 93,15% ± 1,13% for the standard method (n=19). There we re statistical significant differences in the values obtained for methods 1 (P=0,001), 3 (P=0,000) and 5 (P=0,004), and there were no statistical significant differences in the values obtained for methods 2 (P=0,113) and 4 (P=0,327). CONCLUSION: From the results obtained, methods 2 and 4 showed a higher correlation with the standard method. Unlike method 4, method 2 is less time - consuming than the reference method and can overcome the problems associated with the solvent toxicity. The remaining methods (1, 3 and 5) tended to overestimate RCP value compared to the standard method.