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1.
Med Eng Phys ; 72: 19-26, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31554572

RESUMO

The diffusion of medical devices is expanding at an astonishing rate. The increasing number of novel patents per year suggests this growth will continue. In contrast to drugs, medical devices are intrinsically dependent on the environment in which they are used and how they are maintained. This created an unprecedented global need for well-trained biomedical engineers who can help healthcare systems to assess them. The International Federation for Medical and Biological Engineering (IFMBE) is the global scientific society of biomedical engineers in official relations with the United Nations World Health Organisation (WHO) and has been very active in promoting the role of the biomedical engineer in Health Technology Assessment (HTA). The IFMBE Health Technology Assessment Division (HTAD) is the IFMBE operative branch in this field, promoting studies, projects and activities to foster the growth of this specific and very important science sector, including summer schools, training material, an HTA eLearning platform, HTA guidelines, awards and more. This article describes the vision, the mission and the strategy of the HTAD, with a focus on the results achieved and the impact this is having on global policymaking.


Assuntos
Engenharia Biomédica/tendências , Internacionalidade , Avaliação da Tecnologia Biomédica/tendências , Distinções e Prêmios , Humanos , Colaboração Intersetorial
2.
J Xray Sci Technol ; 24(1): 23-41, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26890907

RESUMO

OBJECTIVE: The aim of this study is to investigate the validity of using the Multiple Projection Algorithm (MPA) for Breast Tomosynthesis (BT) using real projection images acquired with phantoms at a clinical setting. METHODS: The CIRS-BR3D phantom with ranging thicknesses between 3 cm and 6 cm was used for all image quality evaluations. Five sets of measurements were acquired, each comprised of a 2D mammographic image followed by a set of 25 projections within an arc length of 50°. A reconstruction algorithm based on the MPA was adapted for partial isocentric rotation using a stationary detector. For reference purposes, a Back Projection (BP) algorithm was also developed for this geometry. The performance of the algorithms was evaluated, in combination with pre-filtering of the projections, in comparative studies that involved also a comparison between tomosynthesis slices and 2D mammograms. RESULTS: Evaluation of tomosynthesis slices reconstructed with BP and MPA showed close performance for the two algorithms with no considerable differences in feature detection, size and appearance of the background tissue with the MPA running faster the overall process. Pre-filtering of the projections, led to better BT images compared to non-filtering. Increased thickness resulted in limited detection of the features of interest, especially the smaller sized ones. In these cases, the filtered BT slices allowed improved visualization due to removed superimposed tissue compared to the 2D images. The different breast-like slab arrangements in phantoms of the same thickness demonstrated a slight influence on the quality of reconstructed features. CONCLUSIONS: The MPA which had been applied previously to reconstruct tomograms from projections acquired at synchrotron facilities, is a time efficient algorithm, and is fully compliant with and can be successfully used in BT clinical systems. Compared to 2D mammography, BT shows advantage in visualizing features of small size and for increased phantom thickness or features within a dense background with superimposed structures.


Assuntos
Algoritmos , Mama/diagnóstico por imagem , Mamografia/métodos , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imagens de Fantasmas
3.
Phys Med ; 32(2): 353-61, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26818470

RESUMO

PURPOSE: Breast augmentation is one of the most popular cosmetic surgeries worldwide. The aim of this study is to investigate the effect of breast implant insertion on the detectability and visibility of lesions on mammography and breast tomosynthesis (BT) images. MATERIALS AND METHODS: Three software phantoms, composed of a homogeneous background with embedded silicone gel structures, and two types of breast abnormalities, microcalcifications (µCs) and masses, were generated. Two X-ray breast imaging modalities were simulated: mammography and BT with six incident monochromatic X-ray beams with energies in the interval between 20 and 30 keV. Projection images were generated using an in-house developed Monte Carlo simulator. The detectability of mammographic findings adjacent to the implant material and the influence of the incident beam energy and implant thickness on the feature detection were studied. RESULTS: It was found that implants thicker than 26 mm for the case of mammography and 14 mm for the case of BT obscured the visibility of underlying structures. Although BT demonstrated a lack of contrast, this modality was able to visualize µCs under considerable depths of implant. Increasing the incident beam energy led to better visualization of small µCs, while in the case of breast masses, their detectability was limited. CONCLUSIONS: Silicone gel implants introduce a limitation in the image quality of mammograms resulting in low detectability of features. In addition, silicone gel implants obscure partially or totally parts of the image, depending on the size and the thickness of the implant as well the energy of the X-rays used.


Assuntos
Artefatos , Implantes de Mama , Mama , Mamografia/métodos , Método de Monte Carlo , Silicones , Imagens de Fantasmas
4.
Phys Med Biol ; 59(16): 4681-96, 2014 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-25082791

RESUMO

The aim of this study is to investigate the impact on image quality of using monochromatic beams for lower dose breast tomosynthesis (BT). For this purpose, modeling and simulation of BT and mammography imaging processes have been performed using two x-ray beams: one at 28 kVp and a monochromatic one at 19 keV at different entrance surface air kerma ranging between 0.16 and 5.5 mGy. Two 4 cm thick computational breast models, in a compressed state, were used: one simple homogeneous and one heterogeneous based on CT breast images, with compositions of 50% glandular-50% adipose and 40% glandular-60% adipose tissues by weight, respectively. Modeled lesions, representing masses and calcifications, were inserted within these breast phantoms. X-ray transport in the breast models was simulated with previously developed and validated Monte Carlo application. Results showed that, for the same incident photon fluence, the use of the monochromatic beam in BT resulted in higher image quality compared to the one using polychromatic acquisition, especially in terms of contrast. For the homogenous phantom, the improvement ranged between 15% and 22% for calcifications and masses, respectively, while for the heterogeneous one this improvement was in the order of 33% for the masses and 17% for the calcifications. For different exposures, comparable image quality in terms of signal-difference-to-noise ratio and higher contrast for all features was obtained when using a monochromatic 19 keV beam at a lower mean glandular dose, compared to the polychromatic one. Monochromatic images also provide better detail and, in combination with BT, can lead to substantial improvement in visualization of features, and particularly better edge detection of low-contrast masses.


Assuntos
Mama , Mamografia/métodos , Método de Monte Carlo , Mama/citologia , Estudos de Viabilidade , Feminino , Humanos , Imagens de Fantasmas , Doses de Radiação , Razão Sinal-Ruído
5.
Med Phys ; 39(9): 5621-34, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22957628

RESUMO

PURPOSE: This study investigates the image quality of tomosynthesis slices obtained from several acquisition sets with synchrotron radiation using a breast phantom incorporating details that mimic various breast lesions, in a heterogeneous background. METHODS: A complex Breast phantom (MAMMAX) with a heterogeneous background and thickness that corresponds to 4.5 cm compressed breast with an average composition of 50% adipose and 50% glandular tissue was assembled using two commercial phantoms. Projection images using acquisition arcs of 24°, 32°, 40°, 48°, and 56° at incident energy of 17 keV were obtained from the phantom with the synchrotron radiation for medical physics beamline at ELETTRA Synchrotron Light Laboratory. The total mean glandular dose was set equal to 2.5 mGy. Tomograms were reconstructed with simple multiple projection algorithm (MPA) and filtered MPA. In the latter case, a median filter, a sinc filter, and a combination of those two filters were applied on the experimental data prior to MPA reconstruction. Visual inspection, contrast to noise ratio, contrast, and artifact spread function were the figures of merit used in the evaluation of the visualisation and detection of low- and high-contrast breast features, as a function of the reconstruction algorithm and acquisition arc. To study the benefits of using monochromatic beams, single projection images at incident energies ranging from 14 to 27 keV were acquired with the same phantom and weighted to synthesize polychromatic images at a typical incident x-ray spectrum with W target. RESULTS: Filters were optimised to reconstruct features with different attenuation characteristics and dimensions. In the case of 6 mm low-contrast details, improved visual appearance as well as higher contrast to noise ratio and contrast values were observed for the two filtered MPA algorithms that exploit the sinc filter. These features are better visualized at extended arc length, as the acquisition arc of 56° with 15 projection images demonstrates the highest image reconstruction quality. For microcalcifications, filtered MPA implemented with a combination of median and sinc filters indicates better feature appearance due to efficient suppression of background tissue. The image quality of these features is less sensitive to the acquisition arc. Calcifications with size ranging from 170 to 500 µm, like the ones presently studied, are well identified and visualized for all arcs used. The comparison of single projection images obtained under different beam conditions showed that the use of monochromatic beam can produce an image with higher contrast and contrast to noise ratio compared to an image corresponding to a polychromatic beam even when the latter is acquired with double incident exposure. CONCLUSIONS: Filter optimization in respect to the type of feature characteristics is important before the reconstruction. The MPA combined with median and sinc filters results in improved reconstruction of microcalcifications and low-contrast features. The latter are better visualized at extended arc length, while microcalcifications are less sensitive to this acquisition parameter. Use of monochromatic beams may result in tomographic images with higher contrast acquired at lower incident exposures.


Assuntos
Mamografia/instrumentação , Síncrotrons , Processamento de Imagem Assistida por Computador , Imagens de Fantasmas , Controle de Qualidade
6.
Comput Methods Programs Biomed ; 107(1): 90-6, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22024418

RESUMO

End stage renal disease (ESRD) treatment methods are considered to be among the most expensive procedures for chronic conditions worldwide which also have severe impact on patients' quality of life. During the last decade, Greece has been among the countries with the highest incidence and prevalence, while at the same time with the lowest kidney transplantation rates. Predicting future patients' number on Renal Replacement Therapy (RRT) is essential for health care providers in order to achieve more effective resource management. In this study a Markov Chain Monte Carlo (MCMC) simulation is presented for predicting the future number of ESRD patients for the period 2009-2020 in Greece. The MCMC model comprises Monte Carlo sampling techniques applied on probability distributions of the constructed Markov Chain. The model predicts that there will be 15,147 prevalent patients on RRT in Greece by 2020. Additionally, a cost-effectiveness analysis was performed on a scenario of gradually reducing the hemodialysis patients in favor of increasing the transplantation number by 2020. The proposed scenario showed net savings of 86.54 million Euros for the period 2009-2020 compared to the base-case prediction.


Assuntos
Simulação por Computador , Falência Renal Crônica/epidemiologia , Adulto , Idoso , Algoritmos , Análise Custo-Benefício , Grécia/epidemiologia , Humanos , Falência Renal Crônica/economia , Falência Renal Crônica/terapia , Transplante de Rim/economia , Transplante de Rim/estatística & dados numéricos , Cadeias de Markov , Pessoa de Meia-Idade , Modelos Econômicos , Método de Monte Carlo , Diálise Renal/economia , Diálise Renal/estatística & dados numéricos
7.
Med Eng Phys ; 33(4): 479-89, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21183392

RESUMO

Closed intramedullary nailing is a common technique for treatment of femur and tibia fractures. The most challenging step in this procedure is the precise placement of the lateral screws that stabilize the fragmented bone. The present work concerns the development and the evaluation of a method to accurately identify in the 3D space the axes of the nail hole canals. A limited number of projection images are acquired around the leg with the help of a C-arm. On two of them, the locking hole entries are interactively selected and a rough localization of the hole axes is performed. Perpendicularly to one of them, cone-beam computed tomography (CBCT) reconstructions are produced. The accurate identification and localization of the hole axes are done by an identification of the centers of the nail holes on the tomograms and a further 3D linear regression through principal component analysis (PCA). Various feature-based approaches (RANSAC, least-square fitting, Hough transform) have been compared for best matching the contours and the centers of the holes on the tomograms. The robustness of the suggested method was investigated using simulations. Programming is done in Matlab and C++. Results obtained on synthetic data confirm very good localization accuracy - mean translational error of 0.14 mm (std=0.08 mm) and mean angular error of 0.84° (std=0.35°) at no radiation excess. Successful localization can be further used to guide a surgeon or a robot for correct drilling the bone along the nail openings.


Assuntos
Pinos Ortopédicos , Tomografia Computadorizada de Feixe Cônico , Fixação Intramedular de Fraturas/métodos , Imageamento Tridimensional/métodos , Fluoroscopia
8.
Med Phys ; 37(11): 5604-17, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21158272

RESUMO

PURPOSE: This work presents an improved algorithm for the generation of 3D breast software phantoms and its evaluation for mammography. METHODS: The improved methodology has evolved from a previously presented 3D noncompressed breast modeling method used for the creation of breast models of different size, shape, and composition. The breast phantom is composed of breast surface, duct system and terminal ductal lobular units, Cooper's ligaments, lymphatic and blood vessel systems, pectoral muscle, skin, 3D mammographic background texture, and breast abnormalities. The key improvement is the development of a new algorithm for 3D mammographic texture generation. Simulated images of the enhanced 3D breast model without lesions were produced by simulating mammographic image acquisition and were evaluated subjectively and quantitatively. For evaluation purposes, a database with regions of interest taken from simulated and real mammograms was created. Four experienced radiologists participated in a visual subjective evaluation trial, as they judged the quality of the simulated mammograms, using the new algorithm compared to mammograms, obtained with the old modeling approach. In addition, extensive quantitative evaluation included power spectral analysis and calculation of fractal dimension, skewness, and kurtosis of simulated and real mammograms from the database. RESULTS: The results from the subjective evaluation strongly suggest that the new methodology for mammographic breast texture creates improved breast models compared to the old approach. Calculated parameters on simulated images such as beta exponent deducted from the power law spectral analysis and fractal dimension are similar to those calculated on real mammograms. The results for the kurtosis and skewness are also in good coincidence with those calculated from clinical images. Comparison with similar calculations published in the literature showed good agreement in the majority of cases. CONCLUSIONS: The improved methodology generated breast models with increased realism compared to the older model as shown in evaluations of simulated images by experienced radiologists. It is anticipated that the realism will be further improved using an advanced image simulator so that simulated images may be used in feasibility studies in mammography.


Assuntos
Neoplasias da Mama/diagnóstico , Mamografia/métodos , Radioterapia (Especialidade)/métodos , Algoritmos , Mama/fisiologia , Simulação por Computador , Feminino , Fractais , Humanos , Processamento de Imagem Assistida por Computador/métodos , Mamografia/instrumentação , Modelos Estatísticos , Distribuição Normal , Imagens de Fantasmas , Análise de Regressão , Software
9.
Med Phys ; 37(4): 1893-903, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20443511

RESUMO

PURPOSE: In this article, the image quality of reconstructed volumes by four algorithms for digital tomosynthesis, applied in the case of breast, is investigated using synchrotron radiation. METHODS: An angular data set of 21 images of a complex phantom with heterogeneous tissue-mimicking background was obtained using the SYRMEP beamline at ELETTRA Synchrotron Light Laboratory, Trieste, Italy. The irradiated part was reconstructed using the multiple projection algorithm (MPA) and the filtered backprojection with ramp followed by hamming windows (FBR-RH) and filtered backprojection with ramp (FBP-R). Additionally, an algorithm for reducing the noise in reconstructed planes based on noise mask subtraction from the planes of the originally reconstructed volume using MPA (MPA-NM) has been further developed. The reconstruction techniques were evaluated in terms of calculations and comparison of the contrast-to-noise ratio (CNR) and artifact spread function. RESULTS: It was found that the MPA-NM resulted in higher CNR, comparable with the CNR of FBP-RH for high contrast details. Low contrast objects are well visualized and characterized by high CNR using the simple MPA and the MPA-NM. In addition, the image quality of the reconstructed features in terms of CNR and visual appearance as a function of the initial number of projection images and the reconstruction arc was carried out. Slices reconstructed with more input projection images result in less reconstruction artifacts and higher detail CNR, while those reconstructed from projection images acquired in reduced angular range causes pronounced streak artifacts. CONCLUSIONS: Of the reconstruction algorithms implemented, the MPA-NM and MPA are a good choice for detecting low contrast objects, while the FBP-RH, FBP-R, and MPA-NM provide high CNR and well outlined edges in case of microcalcifications.


Assuntos
Neoplasias da Mama/patologia , Neoplasias da Mama/radioterapia , Mama/patologia , Síncrotrons , Algoritmos , Artefatos , Meios de Contraste/farmacologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional/métodos , Imagens de Fantasmas , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Software , Fatores de Tempo , Tomografia/métodos
10.
Comput Biol Med ; 40(2): 208-14, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20056197

RESUMO

Computer models and simulations of X-ray imaging systems are becoming a very precious tool during the development and evaluation of new X-ray imaging techniques. To provide, however, a faithful simulation of a system, all components must be accurately modelled and tested, followed by verification through experimental measurements. This paper presents a validation study of the XRayImagingSimulator, an in-house developed X-ray imaging simulator, which is extensively used as a basic tool in carrying out complex breast imaging simulations. The approach followed compares results obtained via an experimental setup for breast phantom (CIRS 011A) imaging, using synchrotron radiation (SYRMEP beamline at ELETTRA), with those from its simulated setup under the same conditions. The study demonstrated a very good agreement between experimental and simulated images compared both in terms of subjective and objective criteria. The combination of the XRayImagingSimulator with our BreastSimulator provides a powerful tool for in silico testing of new X-ray breast imaging approaches.


Assuntos
Simulação por Computador , Mamografia/métodos , Imagens de Fantasmas , Algoritmos , Mama/anatomia & histologia , Feminino , Humanos , Mamografia/instrumentação , Método de Monte Carlo , Processamento de Sinais Assistido por Computador , Software , Síncrotrons
11.
Phys Med ; 25(4): 172-80, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19186088

RESUMO

The effect of cylindrical protector dimensions, material and distance from the source on the dose distribution in rotational radiotherapy was studied to assess the potential protection possibilities of small-sized radiosensitive structures, such as spinal cord. The dose distributions were evaluated in terms of dose at the protected region and surface dose, ratio of the dose at the protected region to the maximum dose, and dose gradient. High-density materials, such as lead, tungsten, gold and cerrobend, along with new polymer-metal composite ones were used in simulation studies, performed by an in-house developed Monte Carlo Radiotherapy Simulator. To ensure correct modeling of the composite materials, simulated attenuation data were verified against experimentally measured data. The dependence of the dose at the protected region from the protector diameter and the field size was established. Protectors of higher density and larger diameter provide not only lower dose at the protected region, but also steeper dose gradient and lower ratio of the dose at the protected region to the treatment dose. For the protection of small structures, high-density protectors placed further from the source allow thicker protectors to be used. The surface dose increases insignificantly for the studied protector-surface distances. The results have shown that shielding properties of composite materials are close to those of lead.


Assuntos
Simulação por Computador , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia/métodos , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Equipamentos de Proteção , Dosagem Radioterapêutica , Rotação
12.
Med Phys ; 33(11): 4289-98, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17153407

RESUMO

This article presents simulation studies of field shaping in rotational radiation therapy by means of two categories of beam modifying devices: protectors and shapers. The protectors used are diminished copies of the organs at risk (OARs) and stay parallel to them during gantry rotation. Thus, each protector always keeps the corresponding OAR in its shadow, significantly reducing the irradiation. The shapers are used in order to obtain a more uniform dose distribution in the planning target volume (PTV) while preserving their initial orientation during gantry rotation. Thus, the use of beam modifying devices allows modulation of the beam intensity, to better fit irradiation requirements, at every gantry position. A software tool for calculations of geometrical position and dimensions of the beam modifying devices, using information about the shape, size, and position of the protected organ or area at risk as input, was developed. This tool was integrated into the in-house-developed Monte Carlo radiation therapy simulator (MCRTS), used to simulate the particle transport through the designed system. The verification of the software tool showed good agreement between experimental and simulation data, with discrepancies of less than 3%. Dose distributions in solid-geometry and voxel-based neck models were evaluated. Furthermore, the effectiveness of the shapers to modify the dose distribution outside the protected area was studied. Results demonstrated that the use of the shapers effectively improves dose uniformity. Studies using shapers of different materials were also carried out and resulted in similar dose distributions. The results of the simulation studies with a voxel-based model showed that rotational therapy with beam modifying devices offers adequate protection of the OAR and a uniform dose distribution outside the protected region.


Assuntos
Algoritmos , Modelos Biológicos , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Humanos , Modelos Estatísticos , Método de Monte Carlo , Dosagem Radioterapêutica , Eficiência Biológica Relativa , Reprodutibilidade dos Testes , Rotação , Sensibilidade e Especificidade
13.
Phys Med Biol ; 51(18): 4497-515, 2006 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-16953039

RESUMO

This paper presents a mammography simulator and demonstrates its applicability in feasibility studies in dual-energy (DE) subtraction mammography. This mammography simulator is an evolution of a previously presented x-ray imaging simulation system, which has been extended with new functionalities that are specific for DE simulations. The new features include incident exposure and dose calculations, the implementation of a DE subtraction algorithm as well as amendments to the detector and source modelling. The system was then verified by simulating experiments and comparing their results against published data. The simulator was used to carry out a feasibility study of the applicability of DE techniques in mammography, and more precisely to examine whether this modality could result in better visualization and detection of microcalcifications. Investigations were carried out using a 3D breast software phantom of average thickness, monoenergetic and polyenergetic beam spectra and various detector configurations. Dual-shot techniques were simulated. Results showed the advantage of using monoenergetic in comparison with polyenergetic beams. Optimization studies with monochromatic sources were carried out to obtain the optimal low and high incident energies, based on the assessment of the figure of merit of the simulated microcalcifications in the subtracted images. The results of the simulation study with the optimal energies demonstrated that the use of the DE technique can improve visualization and increase detectability, allowing identification of microcalcifications of sizes as small as 200 microm. The quantitative results are also verified by means of a visual inspection of the synthetic images.


Assuntos
Doenças Mamárias/diagnóstico por imagem , Simulação por Computador , Mamografia/métodos , Técnica de Subtração , Algoritmos , Doenças Mamárias/patologia , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/patologia , Calcinose/diagnóstico por imagem , Calcinose/patologia , Feminino , Humanos , Imageamento Tridimensional , Mamografia/instrumentação , Modelos Biológicos , Imagens de Fantasmas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
Med Eng Phys ; 27(7): 549-54, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16087386

RESUMO

Recent developments in the field of Biomedical Engineering have led to considerable improvement in health care delivery, but also impose continuous change and improvement in education and training schemes of its professionals, in order to assure appropriate front-line knowledge, competencies and skills. Open and distance learning provides a very effective means for continuous education and training purposes. Image processing may be used as an attractive case for exploring the Collaborative Learning Model (CLM) paradigm in Open Distance Learning (ODL). An on-line course on Medical Image Processing, following the principles of collaborative learning, has been developed and evaluated. Each concept of the course is available in three levels of complexity. The first level shows only a very general description, actually the main idea. If the user is interested to continue, a second level is accessible, where the concept is explained in a more detailed manner. Moreover, for some concepts requiring complicated mathematical proofs, a third level is available. The course has been used at the European Course on Biomedical Engineering organized by the Department of Medical Physics, University of Patras, Greece, and was positively evaluated by the students.


Assuntos
Engenharia Biomédica/educação , Instrução por Computador/métodos , Currículo , Educação a Distância/métodos , Educação Profissionalizante/métodos , Processamento de Imagem Assistida por Computador , Internet , Grécia , Física Médica/educação
15.
Phys Med Biol ; 48(22): 3699-719, 2003 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-14680268

RESUMO

This paper presents a methodology for three-dimensional (3D) computer modelling of the breast, using a combination of 3D geometrical primitives and voxel matrices that can be further subjected to simulated x-ray imaging, to produce synthetic mammograms. The breast phantom is a composite model of the breast and includes the breast surface, the duct system and terminal ductal lobular units. Cooper's ligaments, the pectoral muscle, the 3D mammographic background and breast abnormalities. A second analytical x-ray matter interaction modelling module is used to generate synthetic images from monoenergetic fan beams. Mammographic images of various synthesized breast models differing in size, shape and composition were produced. A preliminary qualitative assessment performed by three radiologists and a quantitative evaluation study using fractal and grey-level histogram analysis were conducted. A comparative study of extracted features with published data has also been performed. The evaluation results indicated good correlation of characteristics between synthetic and actual radiographs. Applications foreseen are not only in the area of breast imaging experimentation but also in education and training.


Assuntos
Mama/anatomia & histologia , Computação Matemática , Imagens de Fantasmas , Interpretação de Imagem Radiográfica Assistida por Computador , Software , Feminino , Humanos , Mamografia/instrumentação , Modelos Anatômicos
16.
Biomed Instrum Technol ; 37(1): 25-33, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12613291

RESUMO

The evolution of biomedical technology has led to an extraordinary use of medical devices in health care delivery. During the last decade, clinical engineering departments (CEDs) turned toward computerization and application of specific software systems for medical equipment management in order to improve their services and monitor outcomes. Recently, much emphasis has been given to patient safety. Through its Medical Device Directives, the European Union has required all member nations to use a vigilance system to prevent the reoccurrence of adverse events that could lead to injuries or death of patients or personnel as a result of equipment malfunction or improper use. The World Health Organization also has made this issue a high priority and has prepared a number of actions and recommendations. In the present workplace, a new integrated, Windows-oriented system is proposed, addressing all tasks of CEDs but also offering a global approach to their management needs, including vigilance. The system architecture is based on a star model, consisting of a central core module and peripheral units. Its development has been based on the integration of 3 software modules, each one addressing specific predefined tasks. The main features of this system include equipment acquisition and replacement management, inventory archiving and monitoring, follow up on scheduled maintenance, corrective maintenance, user training, data analysis, and reports. It also incorporates vigilance monitoring and information exchange for adverse events, together with a specific application for quality-control procedures. The system offers clinical engineers the ability to monitor and evaluate the quality and cost-effectiveness of the service provided by means of quality and cost indicators. Particular emphasis has been placed on the use of harmonized standards with regard to medical device nomenclature and classification. The system's practical applications have been demonstrated through a pilot evaluation trial.


Assuntos
Sistemas de Gerenciamento de Base de Dados , Documentação/métodos , Equipamentos e Provisões , Armazenamento e Recuperação da Informação/métodos , Software , Integração de Sistemas , Segurança de Equipamentos/métodos , Sistemas de Informação Administrativa , Controle de Qualidade , Gestão da Segurança/métodos , Gestão da Segurança/normas
17.
Comput Methods Programs Biomed ; 70(3): 241-51, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12581556

RESUMO

This paper presents a software simulation package of the entire X-ray projection radiography process including beam generation, absorber structure and composition, irradiation set up, radiation transport through the absorbing medium, image formation and dose calculation. Phantoms are created as composite objects from geometrical or voxelized primitives and can be subjected to simulated irradiation process. The acquired projection images represent the two-dimensional spatial distribution of the energy absorbed in the detector and are formed at any geometry, taking into account energy spectrum, beam geometry and detector response. This software tool is the evolution of a previously presented system, with new functionalities, user interface and an expanded range of applications. This has been achieved mainly by the use of combinatorial geometry for phantom design and the implementation of a Monte Carlo code for the simulation of the radiation interaction at the absorber and the detector.


Assuntos
Intensificação de Imagem Radiográfica/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Simulação por Computador , Humanos , Computação Matemática , Método de Monte Carlo , Imagens de Fantasmas , Software
18.
J Med Eng Technol ; 26(6): 247-52, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12490030

RESUMO

The image intensifier (II)-based imaging systems, as radiotherapy simulators or C-arm X-ray units, have also been used for image acquisition in computed tomography. When analogue-to-digital conversion is performed on the output signal of the television camera, the accuracy for low-amplitude video signals, corresponding to X-ray pathways crossing high attenuation structures, is limited. To deal with this lack of accuracy, we investigated the benefits of using a logarithmic amplifier (LOGAMP) inserted between the television camera output and the analogue-to-digital converter (ADC) in the image acquisition chain. Such a device was intended to provide better use of the available ADCs of a given resolution and actually to reduce the quantization noise. Simulated data were used in this study, and cases with and without logarithmic amplifier were compared. Based on the simulation results, we formulate requirements for several signal and acquisition system parameters where the use of such a circuit is recommended.


Assuntos
Conversão Análogo-Digital , Fluoroscopia/instrumentação , Intensificação de Imagem Radiográfica/instrumentação , Tomografia Computadorizada por Raios X/instrumentação , Amplificadores Eletrônicos , Simulação por Computador , Desenho de Equipamento , Fluoroscopia/métodos , Imagens de Fantasmas , Intensificação de Imagem Radiográfica/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Processos Estocásticos , Tomografia Computadorizada por Raios X/métodos , Gravação em Vídeo/instrumentação
19.
Acta Radiol ; 42(2): 244-8, 2001 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11259956

RESUMO

PURPOSE: To study image quality in filtered digital tomosynthesis (FDTS) tomograms as a function of their reconstruction arc, using isocentrically acquired, fluoroscopic projection data. MATERIAL AND METHODS: Both digital tomosynthesis (DTS) and cone beam CT (CBCT) reconstruction algorithms are based on backprojection and use cone beam projection data as input. Under limited angle conditions, CBCT is reduced to FDTS, where only a subset of projection data are used for reconstruction. The effect of the reconstruction arc on the spatial resolution, slice thickness, contrast sensitivity, shape distortion and artifacts, was also experimentally studied. The investigation was performed using both simulated and actual fluoroscopic images. RESULTS AND CONCLUSION: Image quality in terms of spatial resolution, slice thickness, shape distortion and artifacts, improved with increasing reconstruction arc and was optimized at 180 degrees, while contrast continued to improve as the arc was increased to 360 degrees. However, DTS was determined to be the technique of choice when reconstruction arcs of less than 40 degrees were used. Consequently, FDTS may be successfully implemented in applications involving extended arc reconstructions, in the range between 40 degrees delimiting the DTS domain and 360 degrees corresponding to CBCT.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos
20.
J Med Eng Technol ; 24(3): 117-22, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11036578

RESUMO

Q-Pro is an application for quality control (QC) and inspection of medical equipment. The system has been designed on the basis of a broad requirements analysis, contributed by clinical engineers from several European countries and with a focus on current and forthcoming regulatory requirements concerning the quality control and risk management for medical equipment. Q-Pro comprises a generalized application, providing the necessary flexibility to accommodate the different degrees of difficulty and specialization in creating or customizing QC protocols, carrying out inspections and managing collected data. The system incorporates a tool library for QC protocol design, widely used multimedia as well as a local database for protocol and inventory data archiving. The paper presents a detailed account of the system context of use, design and functionality.


Assuntos
Equipamentos e Provisões/normas , Sistemas de Informação Administrativa , União Europeia , Controle de Qualidade , Software
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