A system to help physicians with fracture detection in stents.

Fractures in stents are usually detected by visual analysis, which may be affected by the presence of noise and image deformations. The lack of research into automating stent fracture detection has motivated this work, in which techniques are developed to facilitate diagnosis by observation (Image Delineation Algorithm) and, when possible, to point out areas of possible fractures (Fracture Detection Algorithm). The use of classical elements and the development of additional computational techniques contributed to the process of image analysis, providing a possible way to aid medical diagnosis. The developed algorithms are applied to image samples from femoropopliteal arteries, and the results are compared to those of medical diagnosis. As a result, aside from the improvement of image display, a kappa concordance index of 0.878 for the detection of fractures confirms the method as satisfactory, with very good agreement with medical diagnosis.

A comparison of left ventricular border detection techniques applied to 2D echocardiograms

INTRODUCTION: Cardiology has been one of the most important areas of medicine. For several applications to diagnose the heart functions diseases the measurement of left ventricular (LV) cavity area and LV fractional area change are of vital necessity. To achieve this task, it is necessary to trace the border of left ventricle, which manual tracing is a tedious and time-consuming work. To solve this problem, many techniques to automate this border detection have been developed using the specialist tracing as gold standard. METHODS: The purpose of this approach is to analyze the features of the main techniques applied to left ventricle border detection in medical imaging. To facilitate understanding, the left ventricle border detection techniques are divided into three categories: image-based techniques, model-based techniques and pixel-based techniques. For each of the category, a literature review was made to get examples of the techniques applied to left ventricle border detection and to describe them. The result of this review is a comparative tablewhere the main features of each technique is compared. CONCLUSION: From the comparative table we can conclude that the not mentioning of many features of the techniques by the authors and the lack of a standardization of the evaluation techniques hamper a more satisfactory comparison.

A system to help physicians with fracture detection in stents

Fractures in stents are usually detected by visualanalysis, which may be affected by the presence of noiseand image deformations.The lack of research into automatingstent fracture detection has motivated this work, inwhich techniques are developed to facilitate diagnosis byobservation (Image Delineation Algorithm) and, whenpossible, to point out areas of possible fractures (FractureDetection Algorithm). The use of classical elements andthe development of additional computational techniquescontributed to the process of image analysis, providing apossible way to aid medical diagnosis.The developed algorithmsare applied to image samples from femoropoplitealarteries, and the results are compared to those of medicaldiagnosis. As a result, aside from the improvement ofimage display, a kappa concordance index of 0.878 forthe detection of fractures confirms the method as satisfactory,with very good agreement with medical diagnosis.

Análise do desempenho de um eletrocardiógrafo interpretativo para utilização em um sistema computacional de auxílio diagnóstico em síndromes coronarianas agudas / Performance analysis of an interpretive electrocardiograph for use in a computer-aided diagnostic system for acute coronary syndromes

O eletrocardiograma  (ECG) registra a atividade elétrica cardíaca de forma não invasiva e permite obter uma avaliação rápida do ritmo cardíaco, muito útil na definição da conduta terapêutica imediata em pacientes com suspeita de síndrome coronariana aguda  (SCA), que é uma entidade clínica que engloba a angina instável e os infartos agudos do miocárdio com e sem supra-desnível do segmento  ST. Atualmente, eletrocardiógrafos de diversos fabricantes são capazes de fornecer diagnósticos automáticos dos ECGs, mas, apesar disso, existem poucos estudos publicados acerca do desempenho desses equipamentos. O objetivo deste trabalho é avaliar o desempenho de um eletrocardiógrafo interpretativo para determinar sua adequabilidade para uso em um sistema computacional que utiliza informações da história clínica obtida pelo médico generalista e do laudo eletrocardiográfico emitido pelo equipamento avaliado, permitindo auxiliar no diagnóstico de síndromes coronarianas agudas, quando o paciente não é atendido por cardiologistas. Foi utilizado um eletrocardiógrafo interpretativo Nihon  Kohden Cardiofax  9620 que foi testado com um simulador de sinais eletrocardiográficos Metron  PS  420 e, ainda, teve seu desempenho comparado com um sistema de telemedicina disponível em uma região semi-rural brasileira. Os testes resultaram em 93,8 por cento de sensibilidade e 83,3 por cento de especificidade, que foram considerados satisfatórias em situações clínicas compatíveis com isquemia miocárdica aguda, validando a sua utilização em um sistema de inteligência artificial para auxílio ao diagnóstico em SCA.

The electrocardiogram  (ECG) is the recording of the heart’s  electrical activity from the surface of the body and has been worldwide used in routine medical practice since the last century. This is a first-rate tool for a rapid interpretation of cardiac rhythm and for assessment and immediate therapeutic management in patients with suspected acute coronary syndrome, which is a clinical entity that includes unstable  angina and acute myocardial infarction with and without ST-segment elevation. Currently, electrocardiographs from various manufacturers are capable of providing automatic diagnosis of ECGs, but there are few published studies about the performance of these equipments. The objective of this paper is to evaluate the performance of an interpretive electrocardiograph in order to determine their suitability for use in a computer system that uses the medical history information obtained by the general practitioner and the electrocardiographic report emitted by the equipment evaluated to aid the diagnosis of acute coronary syndromes, when the patient is not treated by cardiologists. We used an interpretive electrocardigraph Nihon  Kohden Cardiofax  9620. The electrocardiograph simulator Metron  PS  420 was the choice for the simulated tests, and also we compared the performance of the Cardiofax with a telemedicine system available in a semi-rural area in Brazil. The tests resulted in 93.8 percent sensitivity and 83.3 percent specificity that were considered satisfactory in clinical situations compatible with acute myocardial ischemia, validating their use in an artificial intelligence system for the diagnosis of ACS.

Cardiovascular simulator improvement: pressure versus volume loop assessment.

This article presents improvement on a physical cardiovascular simulator (PCS) system. Intraventricular pressure versus intraventricular volume (PxV) loop was obtained to evaluate performance of a pulsatile chamber mimicking the human left ventricle. PxV loop shows heart contractility and is normally used to evaluate heart performance. In many heart diseases, the stroke volume decreases because of low heart contractility. This pathological situation must be simulated by the PCS in order to evaluate the assistance provided by a ventricular assist device (VAD). The PCS system is automatically controlled by a computer and is an auxiliary tool for VAD control strategies development. This PCS system is according to a Windkessel model where lumped parameters are used for cardiovascular system analysis. Peripheral resistance, arteries compliance, and fluid inertance are simulated. The simulator has an actuator with a roller screw and brushless direct current motor, and the stroke volume is regulated by the actuator displacement. Internal pressure and volume measurements are monitored to obtain the PxV loop. Left chamber internal pressure is directly obtained by pressure transducer; however, internal volume has been obtained indirectly by using a linear variable differential transformer, which senses the diaphragm displacement. Correlations between the internal volume and diaphragm position are made. LabVIEW integrates these signals and shows the pressure versus internal volume loop. The results that have been obtained from the PCS system show PxV loops at different ventricle elastances, making possible the simulation of pathological situations. A preliminary test with a pulsatile VAD attached to PCS system was made.

Cardiovascular simulator improvement: pressure versus volume loop assessment

This article presents improvement on a physical cardiovascular simulator (PCS) system. Intraventricular pressure versus intraventricular volume (PxV) loop was obtained to evaluate performance of a pulsatile chambermimicking the human left ventricle. PxV loop shows heart contractility and is normally used to evaluate heartperformance. In many heart diseases, the stroke volume decreases because of low heart contractility.This pathologicalsituation must be simulated by the PCS in order to evaluate the assistance provided by a ventricular assistdevice (VAD).The PCS system is automatically controlled by a computer and is an auxiliary tool for VAD controlstrategies development. This PCS system is according to a Windkessel model where lumped parameters are used for cardiovascular system analysis. Peripheral resistance, arteriescompliance, and fluid inertance are simulated.The simulator has an actuator with a roller screw and brushlessdirect current motor, and the stroke volume is regulated by the actuator displacement. Internal pressure and volume measurements are monitored to obtain the PxV loop. Left chamber internal pressure is directly obtained by pressure transducer; however, internal volume has been obtained indirectly by using a linear variable differential transformer, which senses the diaphragm displacement. Correlationsbetween the internal volume and diaphragm position are made. LabVIEW integrates these signals and shows the pressure versus internal volume loop. The results that have been obtained from the PCS system show PxV loops at different ventricle elastances, makingpossible the simulation of pathological situations. A preliminary test with a pulsatile VAD attached to PCS systemwas made.

Artificial neural network: border detection in echocardiography.

Being non-invasive and low cost, the echocardiography has become a diagnostic technique largely applied for the determination of the left ventricle systolic and diastolic volumes, which are used indirectly to calculate the left ventricle ejection volume, the cardiac cavities muscular contraction, the regional ejection fraction, the myocardial thickness, and the ventricular mass, etc. However, the image is very noisy, which renders the delineation of the borders of the left ventricle very difficult. While there are many techniques image segmentation, this work chooses the artificial neural network (ANN) since it is not very sensitive to noise. In order to reduce the processing time, the operator selects the region of interest where the neural network will identify the borders. Neighborhood and gradient search techniques are then employed to link the points and the left ventricle contour is traced. The present method has been efficient in detecting the left ventricle borders echocardiography images compared to those whose borders were delineated by the specialists. For good results, it is important to choose properly the areas to be analyzed and the central points of these areas.

A new technique to control brushless motor for blood pump application

This article presents a back-electromotive force (BEMF)-based technique of detection for sensorless brushless direct current motor (BLDCM) drivers. The BLDCM has been chosen as the energy converter in rotary or pulsatile blood pumps that use electrical motors for pumping. However, in order to operate properly, the BLDCM driver needs to know the shaft position. Usually, that information is obtained through a set of Hall sensors assembled close to the rotor and connected to the electronic controller by wires. Sometimes, a large distance between the motor and controller makes the system susceptible to interference on the sensor signal because of winding current switching. Thus, the goal of the sensorless technique presented in this study is to avoid this problem. First, the operation of BLDCM was evaluated on the electronic simulator PSpice. Then, a BEMF detector circuitry was assembled in our laboratories. For the tests, a sensordependent system was assembled where the direct comparison between the Hall sensors signals and the detected signals was performed. The obtained results showed that the output sensorless detector signals are very similar to the Hall signals at speeds of more than 2500 rpm. Therefore, the sensorless technique is recommended as a responsible or redundant system to be used in rotary blood pumps.

New centrifugal blood pump with dual impeller and double pivot bearing system: wear evaluation in bearing system, performance tests, and preliminary hemolysis tests.

A new dual impeller centrifugal blood pump has been developed as a research collaboration between Baylor College of Medicine and Institute Dante Pazzanese of Cardiology for long-term left ventricle assist device (LVAD). A design feature of this new pump is a dual impeller that aims to minimize a stagnant flow pattern around the inlet port. Several different materials were tested in order to adopt a double pivot bearing design originally developed by Prof. Dr. Yukihiko Nosé from Baylor College of Medicine. Hydraulic performance tests were conducted with two different inlet ports' angle configurations 30 degrees and 45 degrees . Pump with inlet port angle of 45 degrees achieved best values of pressure ahead and flow after 1800 rpm. Preliminary hemolysis tests were conducted using human blood. The pump showed good performance results and no alarming trace of hemolysis, proving to be a feasible long-term LVAD.

An electro-fluid-dynamic simulator for the cardiovascular system.

This work presents the initial studies and the proposal for a cardiovascular system electro-fluid-dynamic simulator to be applied in the development of left ventricular assist devices (LVADs). The simulator, which is being developed at University Sao Judas Tadeu and at Institute Dante Pazzanese of Cardiology, is composed of three modules: (i) an electrical analog model of the cardiovascular system operating in the PSpice electrical simulator environment; (ii) an electronic controller, based on laboratory virtual instrumentation engineering workbench (LabVIEW) acquisition and control tool, which will act over the physical simulator; and (iii) the physical simulator: a fluid-dynamic equipment composed of pneumatic actuators and compliance tubes for the simulation of active cardiac chambers and big vessels. The physical simulator (iii) is based on results obtained from the electrical analog model (i) and physiological parameters.

A new technique to control brushless motor for blood pump application.

This article presents a back-electromotive force (BEMF)-based technique of detection for sensorless brushless direct current motor (BLDCM) drivers. The BLDCM has been chosen as the energy converter in rotary or pulsatile blood pumps that use electrical motors for pumping. However, in order to operate properly, the BLDCM driver needs to know the shaft position. Usually, that information is obtained through a set of Hall sensors assembled close to the rotor and connected to the electronic controller by wires. Sometimes, a large distance between the motor and controller makes the system susceptible to interference on the sensor signal because of winding current switching. Thus, the goal of the sensorless technique presented in this study is to avoid this problem. First, the operation of BLDCM was evaluated on the electronic simulator PSpice. Then, a BEMF detector circuitry was assembled in our laboratories. For the tests, a sensor-dependent system was assembled where the direct comparison between the Hall sensors signals and the detected signals was performed. The obtained results showed that the output sensorless detector signals are very similar to the Hall signals at speeds of more than 2500 rpm. Therefore, the sensorless technique is recommended as a responsible or redundant system to be used in rotary blood pumps.

Anisotropic median-diffusion for filtering noisy electrocardiogram signals.

Low Noise Electrocardiogram (ECG) has been widely used for heart disease diagnosis. The anisotropic median-diffusion is the filter obtained by intercalating a median filtering in each diffusion step. We propose to use anisotropic median-diffusion to filter noisy ECG signals. We describe how to estimate appropriate parameters of the proposed filter. We validate our method using ECG signals from the MIT-BIH databases (many of them with premature ventricular contraction) and compare our method with other filtering methods. Experiments show that the proposed technique can effectively remove the noise without changing the instants and amplitudes of events, as well as preserving the morphologies of ECG signals in sections of the QRS complex.

New centrifugal blood pump with dual impeller and double pivot bearing system: wear evaluation in bearing system, performance tests, and preliminary hemolysis tests

A new dual impeller centrifugal blood pump has been developed as a research collaboration between Baylor College of Medicine and Institute Dante Pazzanese of Cardiology for long-term left ventricle assist device (LVAD).A design feature of this new pump is a dual impeller that aims to minimize a stagnant flow pattern around the inlet port. Several different materials were tested in order to adopt a double pivot bearing design originally developed by Prof. Dr. Yukihiko Nosé from Baylor College of Medicine. Hydraulic performance tests were conducted with two different inlet ports’ angle configurations 30° and 45°. Pump with inlet port angle of 45° achieved best values of pressure ahead and flow after 1800 rpm. Preliminary hemolysis tests were conducted using human blood. The pump showed good performance results and no alarming trace of hemolysis, proving to be a feasible long-term LVAD.

Coração artificial auxiliar / Heart artificial auxiliary

A geração de tecnologia própria, sempre presente na cardiologia brasileira, proporcionou a formação de profissionais capacitados, criando grupo de pesquisas e empresas de produção de equipamentos. Com base em dados do Minsitério da Saúde, as doenças cardiovasculares representavam aproximadamente 11,8% do total de óbitos das capitais em 1930 em nosso país; em 1996 este percentual cresceu drasticamente chegando a 27,2%; já em 2004 esse índice chegou à 31,8%, o que corresponde à causa de maior mortalidade no Brasil. Em função desse quadro, pesquisas que visam o desenvolvimento de dispositivos para suporte à vida destes pacientes são de grande importância (Ministério da Saúde, 2007).O Instituto Dante Pazzanese de Cardiologia (IDPC) e a Fundação Adib Jatene vêm desenvolvendo um modelo de Coração artificial auxiliar (CAA), configurado como dispositivo de assistência ventricular (DAV), com princípio de funcionamento eletromecânico. O DAV é configurado para assistência ventricular esquerda, pois a grande maioria das insuficiências cardíacas ocorrem no ventrículo esquerdo. O dispositivo...

Tele-ECG (tele-eletrocardiografia à distância via celular) / Tele-ECG (Tele-Echocardiography by distance of cellular phone)

O Instituto Dante Pazzanese de Cardiologia(IDPC) presta atendimento a paciente de diversas regiões; dentre estes, observou-se uma parcela significativa de pacientes externos provenientes de localidades distantes, vindos de Unidades Básicas de Saúde (UBS) que normalmente não possuem especialista em cardiologia. Muitos destes pacientes poderiam ser evitados, reduzindo os custos logísticos da operação, inclusive o custo social. O Sistema Tele-EGG tem como objetivo aplicar uma solução em telemedicina, que consiste de um eletrocardiógrafo convencional, de 12 derivações simultâneas, interligado a um módulo de transmissão/recepção de dados que utiliza a telefonia móvel (celular) para enviar o sinal de ECG e os dados do paciente para uma central de exames. Valendo-se da mobilidade que o sistema oferece, a instalação dos equipamentos, nos mais variados locais, independe de haver uma estrutura fixa com microcomputadores e internet de banda larga: basta haver um sinal de telefonia celular. A central de exames consiste de uma sala de terminais de computadores...

Endurance test on a textured diaphragm for the auxiliary total artificial heart (ATAH).

We performed an endurance test on a textured diaphragm made of polyurethane (BioSpan, The Polymer Technology Group, San Francisco, CA, U.S.A.) to be used in the auxiliary total artificial heart (ATAH), an electromechanical device that can be totally implantable without removing the natural heart due to the device's reduced dimension. The objective of this endurance test was to predict whether this diaphragm would be capable of resisting in vivo tests with the ATAH implanted for fifteen days in calves. In this study, a mock loop system simulating the human circulatory system was used. The test protocol was elaborated to reproduce extreme physiological conditions. The technique to produce the textured diaphragms made of polyurethane is shown. The textured surface is used as basis to fix a layer of calf-skin gelatin. The technique used to make the diaphragm guaranteed a totally textured surface without cracking. The diaphragm demonstrated enough resistance to be used at the 15 day in vivo experiments.

Improvement on the auxiliary total artificial heart (ATAH) left chamber design.

The auxiliary total artificial heart (ATAH) is an electromechanically driven artificial heart with reduced dimensions, which is able to be implanted in the right thoracic or abdominal cavities of an average human patient without removing the natural heart or the heart neurohumoral inherent control mechanism for the arterial pressure. This device uses a brushless direct current motor and a mechanical actuator (roller screw) to move two diaphragms. The ATAH's beating frequency is regulated through the change of the left preload, based on Frank-Starling's law, assisting the native heart in obtaining adequate blood flow. The ATAH left and right stroke volumes are 38 ml and 34 ml, respectively, giving approximately 5 L/min of cardiac output at 160 bpm. Flow visualization studies were performed in critical areas on the ATAH left chamber. A closed circuit loop was used with water and glycerin (37%) at 25 degrees C. Amberlite particles (80 mesh) were illuminated by a 1 mm planar helium-neon laser light. With left mean preload fixed at 10 mm Hg and the afterload at 100 mm Hg, the heart rate varied from 60 to 200 bpm. Two porcine valves were used on the inlet and outlet ports. The flow pattern images were obtained using a color micro-camera and a video recorder. Subsequently, these images were digitized using a PC computer. A persistent stagnant flow was detected in the left chamber inlet port. After improvement on the left chamber design, this stagnant flow disappeared.

Improvement on the auxiliary total artificial heart (ATAH). Left chamber design

The auxiliary total artificial heart (ATAH) is an electromechanically driven artificial heart with reduced dimensions, which is able to be implanted in the right thoracic or abdominal cavities of an average human patient without removing the natural heart or the heart neurohumoral inherent control mechanism for the arterial pressure. This device uses a brushless direct current motor and a mechanical actuator (roller screw) to move two diaphragms. The ATAH’s beating frequency is regulated through the change of the left preload, based on Frank- Starling’s law, assisting the native heart in obtaining adequate blood flow. The ATAH left and right stroke volumes are 38 ml and 34 ml, respectively, giving approximately 5 L/min of cardiac output at 160 bpm. Flow visualization studies were performed in critical areas on the ATAH left chamber. A closed circuit loop was used with water and glycerin (37%) at 25°C. Amberlite particles (80 mesh) were illuminated by a 1 mm planar helium-neon laser light.With left mean preload fixed at 10mmHg and the afterload at 100mmHg, the heart rate varied from 60 to 200 bpm. Two porcine valves were used on the inlet and outlet ports. The flow pattern images were obtained using a color microcamera and a video recorder. Subsequently, these images were digitized using a PC computer. A persistent stagnant flow was detected in the left chamber inlet port. After improvement on the left chamber design, this stagnant flow disappeared. Key Words: Total artificial heart— Ventricle assist device—Cardiac output—Mock circulation system—Flow visualization...

Testes in vitro e in vivo com o Coração Artificial Auxiliar (CAA): um novo modelo de coração artificial totalmente implantável e heterotópico / In vitro and in vivo tests with the Auxiliary Total Artificial Heart (ATAH): a new device of a totally implantable and heterotopic artificial heart

Um novo modelo de coração artificial está sendo desenvolvido e testado em nossos laboratórios, o Coração Artificial Auxiliar (CAA). Este dispositivo foi projetado com dimensões reduzidas para ser implantado em paralelo ao coração natural do paciente, dentro da cavidade torácica direita de forma heterotópica. Foram realizados testes in vitro, em um circuito simulador do sistema circulatório humano, para verificação do desempenho hidrodinâmico do CAA. Os resultados mostraram que o CAA pode fornecer um fluxo de até 5,8 L/min, com uma pré-carga de 20 mmHg e uma pós-carga de 100 mmHg. A freqüência de batimento do CAA e, consequentemente, o débito cardíaco são dependentes da pré-carga do ventrículo esquerdo, funcionamento semelhante ao coração natural (Lei de Frank Starling). Testes in vivo animal estão sendo realizados para avaliar os resultados obtidos com os testes in vitro e para verificar o comportamento do CAA em ambiente e condições fisiológicas difíceis de serem simuladas. Os testes in vivo estão sendo também importantes para o desenvolvimento de técnicas cirúrgicas e treinamento dos cirurgiões cardiovasculares envolvidos no projeto. Até o momento, dois estudos agudos in vivo foram realizados, com o CAA funcionando por 5h, implantado na cavidade torácica direta de carneiros adultos (50 + ou - 5 kg). Os resultados destes estudos in vivo demonstraram que o funcionamento do CAA é sincronizado ao coração natural, sendo possível estudar o comportamento do CAA quando, gradativamente, o coração natural teve sua contratilidade reduzida até sua parada total.