Photoacoustic-based thermal image formation and optimization using an evolutionary genetic algorithm

Abstract Introduction For improved efficiency and security in heat application during hyperthermia, it is important to monitor tissue temperature during treatments. Photoacoustic (PA) pressure wave amplitude has a temperature dependence given by the Gruenesein parameter. Consequently, changes in PA signal amplitude carry information about temperature variation in tissue. Therefore, PA has been proposed as an imaging technique to monitor temperature during hyperthermia. However, no studies have compared the performance of different algorithms to generate PA-based thermal images. Methods Here, four methods to estimate variations in PA signal amplitude for thermal image formation were investigated: peak-to-peak, integral of the modulus, autocorrelation of the maximum value, and energy of the signal. Changes in PA signal amplitude were evaluated using a 1-D window moving across the entire image. PA images were acquired for temperatures ranging from 36oC to 41oC using a phantom immersed in a temperature controlled thermal bath. Results The results demonstrated that imaging processing parameters and methods involved in tracking variations in PA signal amplitude drastically affected the sensitivity and accuracy of thermal images formation. The sensitivity fluctuated more than 20% across the different methods and parameters used. After optimizing the parameters to generate the thermal images using an evolutionary genetic algorithm (GA), the percentage of pixels within the acceptable error was improved, in average, by 7.5%. Conclusion Optimization of processing parameters using GA could increase the accuracy of measurement for this experimental setup and improve quality of PA-based thermal images.

Reproducibility of abdominal fat assessment by ultrasound and computed tomography / Reprodutibilidade da avaliação da gordura abdominal pela ultrassonografia e tomografia computadorizada

Abstract Objective: To test the accuracy and reproducibility of ultrasound and computed tomography (CT) for the quantification of abdominal fat in correlation with the anthropometric, clinical, and biochemical assessments. Materials and Methods: Using ultrasound and CT, we determined the thickness of subcutaneous and intra-abdominal fat in 101 subjects-of whom 39 (38.6%) were men and 62 (61.4%) were women-with a mean age of 66.3 years (60-80 years). The ultrasound data were correlated with the anthropometric, clinical, and biochemical parameters, as well as with the areas measured by abdominal CT. Results: Intra-abdominal thickness was the variable for which the correlation with the areas of abdominal fat was strongest (i.e., the correlation coefficient was highest). We also tested the reproducibility of ultrasound and CT for the assessment of abdominal fat and found that CT measurements of abdominal fat showed greater reproducibility, having higher intraobserver and interobserver reliability than had the ultrasound measurements. There was a significant correlation between ultrasound and CT, with a correlation coefficient of 0.71. Conclusion: In the assessment of abdominal fat, the intraobserver and interobserver reliability were greater for CT than for ultrasound, although both methods showed high accuracy and good reproducibility.

Resumo Objetivo: Testar a precisão e a reprodutibilidade da ultrassonografia (US) e da tomografia computadorizada (TC) para a quantificação da gordura abdominal, em correlação com as avaliações antropométricas e clinicolaboratoriais. Materiais e Métodos: Foram determinadas, por meio da US e da TC, as espessuras subcutâneas e intra-abdominais em 101 indivíduos, sendo 39 homens (38,6%) e 62 mulheres (61,4%), com idade média de 66,3 anos (60-80 anos). Os dados obtidos pela US foram correlacionados com os parâmetros antropométricos, clinicolaboratoriais e com as áreas abdominais medidas pela TC. Resultados: A espessura da gordura intra-abdominal foi a variável que obteve maior coeficiente de correlação com as áreas adiposas abdominais. A TC mostrou maior reprodutibilidade nas mensurações da gordura abdominal, apresentando maior taxa de concordância intraexaminador e interexaminador em comparação com a US. Observou-se índice de correlação de 71% entre a US e a TC. Conclusão: Houve maior concordância intraexaminador e interexaminador na avaliação da gordura abdominal por TC, comparativamente à US, porém ambos os métodos mostraram alta precisão e boa reprodutibilidade.

A magneto-motive ultrasound platform designed for pre-clinical and clinical applications

Abstract Introduction Magneto-motive ultrasound (MMUS) combines magnetism and ultrasound (US) to detect magnetic nanoparticles in soft tissues. One type of MMUS called shear-wave dispersion magneto-motive ultrasound (SDMMUS) analyzes magnetically induced shear waves (SW) to quantify the elasticity and viscosity of the medium. The lack of an established presets or protocols for pre-clinical and clinical studies currently limits the use of MMUS techniques in the clinical setting. Methods This paper proposes a platform to acquire, process, and analyze MMUS and SDMMUS data integrated with a clinical ultrasound equipment. For this purpose, we developed an easy-to-use graphical user interface, written in C++/Qt4, to create an MMUS pulse sequence and collect the ultrasonic data. We designed a graphic interface written in MATLAB to process, display, and analyze the MMUS images. To exemplify how useful the platform is, we conducted two experiments, namely (i) MMUS imaging to detect magnetic particles in the stomach of a rat, and (ii) SDMMUS to estimate the viscoelasticity of a tissue-mimicking phantom containing a spherical target of ferrite. Results The developed software proved to be an easy-to-use platform to automate the acquisition of MMUS/SDMMUS data and image processing. In an in vivo experiment, the MMUS technique detected an area of 6.32 ± 1.32 mm2 where magnetic particles were heterogeneously distributed in the stomach of the rat. The SDMMUS method gave elasticity and viscosity values of 5.05 ± 0.18 kPa and 2.01 ± 0.09 Pa.s, respectively, for a tissue-mimicking phantom. Conclusion Implementation of an MMUS platform with addressed presets and protocols provides a step toward the clinical implementation of MMUS imaging equipment. This platform may help to localize magnetic particles and quantify the elasticity and viscosity of soft tissues, paving a way for its use in pre-clinical and clinical studies.

Evaluation of postural balance in mild cognitive impairment through a three-dimensional electromagnetic system / Avaliação do equilíbrio corporal no comprometimento cognitivo leve através de sistema eletromagnético tridimensional

ABSTRACT INTRODUCTION: Elderly people with cognitive impairment are at greater risk for falls; thus, an understanding of the earliest stages of cognitive decline is necessary. OBJECTIVE: To compare postural balance between elderly people with and without mild cognitive impairment using a three-dimensional system. METHODS: Thirty elderly people with mild cognitive impairment and thirty healthy elderly subjects were selected. Static posturography was performed using three-dimensional electromagnetic equipment and the following parameters were evaluated: maximum displacement, mean speed and total trajectory. Open- and closed-eye stabilometric variable comparisons between groups and within each group were carried out, and a relationship between the Mini Mental State Examination and the total trajectory of all elderly subjects was determined. RESULTS: The analysis among open- and closed-eye conditions showed a significant difference in maximum anteroposterior displacement in the control group and a significant difference in all stabilometric variables in the mild cognitive impairment group. A significant difference between the groups in all variables in the closed-eye condition was observed. There was a strong correlation between cognitive performance and total trajectory. CONCLUSION: Evaluations showed decrease in balance in elderly people with mild cognitive impairment. Presence of anteroposterior displacement can be an early sign of postural control impairment, and the evaluation with visual restriction can be useful in detecting small postural instabilities.

Resumo Introdução: Idosos com alteração cognitiva apresentam maior risco de quedas; assim, é importante compreender as primeiras fases do declínio cognitivo. Objetivo: Comparar o equilíbrio corporal entre idosos com e sem comprometimento cognitivo leve através de um sistema tridimensional. Método: Trinta idosos com comprometimento cognitivo leve e 30 idosos saudáveis foram selecionados. A posturografia estática foi realizada utilizando equipamento eletromagnético tridimensional, e foram avaliados os parâmetros deslocamento máximo, velocidade média e trajetória total. Foi realizada comparação das variáveis estabilométricas com olho aberto e olho fechado intragrupo e intergrupos, e foi estabelecida a relação entre o Mini Exame do Estado Mental e a trajetória total de todos os idosos. Resultados: A análise entre olho aberto e olho fechado no grupo de controle evidenciou uma diferença significativa no deslocamento anteroposterior máximo; no grupo com comprometimento cognitivo leve, houve diferença significativa em todas as variáveis estabilométricas. Foi observada diferença significativa entre os grupos em todas as variáveis na condição de olho fechado. Houve forte correlação entre desempenho cognitivo e trajetória total. Conclusão: As avaliações evidenciaram diminuição do equilíbrio nos idosos com comprometimento cognitivo leve. O deslocamento anteroposterior pode ser um sinal precoce de comprometimento do controle postural, e a avaliação com restrição visual pode ser útil na detecção de pequenas instabilidades posturais.

A computational tool as support in B-mode ultrasound diagnostic quality control

INTRODUCTION: The quality control (QC) of biomedical equipment is a very important process for the quality assurance of the instruments used in diagnoses and treatments. Ultrasound diagnostic imaging is one of the most widely used techniques for diagnostic imaging in hospitals and medical clinics. However, the time required to complete several B-mode imaging QC tests in ultrasound equipment is very critical for a hospital with a high number of exams. Here, we present a computational tool to assist in the acquisition and storage of data from multiple QC tests in B-mode ultrasound diagnostic equipment to promote an efficient alternative for QC in clinical routines. METHODS: The project was planned and implemented in C++ programming language and compiled for two computing platforms: Windows and Linux. The most common QC routine tests for B-mode ultrasound were combined in a simple graphical user interface. RESULTS: After entering all of the correct QC information in the graphical user interface, a final report in PDF format was created. CONCLUSION: The proposed program has been helpful for students and diagnostic professionals and is a quick and easy application for several QC tests for B-mode ultrasound diagnostic equipment. Our program seeks to help in the dissemination and application of QC tests for B-mode ultrasound equipment in hospitals and clinics and for the technical training of ultrasound professionals.

Um estudo piloto na avaliação das estratégias posturais em jovens e idosos usando um sistema eletromagnético tridimensional / A pilot study on the evaluation of postural strategies in young and elderly subjects using a tridimensional electromagnetic system

Para manter o equilíbrio postural, algumas estratégias posturais são normalmente usadas. OBJETIVO: Avaliar as estratégias posturais de jovens e idosos em diferentes condições sensoriais usando um sistema de sensores eletromagnéticos tridimensionais posicionados na primeira vértebra torácica e região sacral. Também reportamos valores de oscilação postural dos jovens e idosos. MÉTODO: Estudo transversal observacional. Participaram do estudo 25 jovens e 16 idosas. O equipamento PolhemusTM com dois sensores foi usado para avaliar os parâmetros de oscilação postural (deslocamento máximo, velocidade média e trajetória). A aquisição dos dados foi realizada com os sujeitos em pé, realizando um teste de 90 segundos para as quatro condições sensoriais: olhos abertos e fechados nas superfícies estável e instável. RESULTADOS: Os sensores 1 e 2 apresentaram alta correlação cruzada em todas as condições sensoriais para ambos os grupos (r > 0.99; p < 0.001). Comparando a correlação cruzada entre os grupos, não foram observadas diferenças significativas. CONCLUSÃO: Este estudo apresentou uma importante ferramenta na análise de oscilação postural e na avaliação das estratégias posturais de jovens e idosos em diferentes condições sensoriais. Os jovens e idosos apresentaram uma forte correlação entre os sensores (estratégia do tornozelo), porém, não foram observadas diferenças significativas entre os grupos.

One resorts to various postural strategies while attempting to maintain balance. OBJECTIVE: To assess the postural strategies adopted by young and elderly subjects in varying sensory conditions by using a system of tridimensional electromagnetic sensors positioned on the projection of the first thoracic vertebra and on the sacral region. Postural oscillation values for young and elderly subjects were also reported. METHOD: This observational cross-sectional study enrolled 25 young and 16 elderly individuals. A PolhemusTM device equipped with two sensors was used to assess postural oscillation parameters (maximum displacement, mean velocity, and trajectory). Data acquisition was carried out with subjects standing while undergoing a 90-second test in four sensory conditions: eyes opened, eyes closed, on a stable surface, and on an unstable surface. RESULTS: Sensors 1 and 2 presented significant cross-correlations in all sensory conditions for both groups (r > 0.99; p < 0.001). No statistically significant differences were seen when the cross-correlations for both groups were compared. CONCLUSION: This study presented an important tool to analyze postural oscillation and assess the postural strategies of young and elderly subjects in different sensory conditions. Young and elderly individuals presented strong correlations between sensors (ankle strategy), but no statistically significant differences were seen between groups.

A newmethod to analyze the subjective visual vertical in patients with bilateral vestibular dysfunction

OBJECTIVE: The aim of this study was to assess the subjective visual vertical in patients with bilateral vestibular dysfunction and to propose a new method to analyze subjective visual vertical data in these patients. METHODS: Static subjective visual vertical tests were performed in 40 subjects split into two groups. Group A consisted of 20 healthy volunteers, and Group B consisted of 20 patients with bilateral vestibular dysfunction. Each patient performed six measurements of the subjective visual vertical test, and the mean values were calculated and analyzed. RESULTS: Analyses of the numerical values of subjective visual vertical deviations (the conventional method of analysis) showed that the mean deviation was 0.326±1.13º in Group A and 0.301±1.87º in Group B. However, by analyzing the absolute values of the subjective visual vertical (the new method of analysis proposed), the mean deviation became 1.35±0.48º in Group A and 2.152±0.93º in Group B. The difference in subjective visual vertical deviations between groups was statistically significant (p,<0.05) only when the absolute values and the range of deviations were considered. CONCLUSION: An analysis of the absolute values of the subjective visual vertical more accurately reflected the visual vertical misperception in patients with bilateral vestibular dysfunction.

Influência da obesidade e da força de preensão palmar no equilíbrio postural estático de idosas ativas / Influence of obesity and handgrip strength in the static postural balance of active older women

O objetivo deste estudo foi investigar a influência da obesidade e da força de preensão palmar (FPP) no equilíbrio postural estático de idosas ativas nas condições de olhos abertos e fechados. Participaram 31 idosas (16 eutróficas e 15 obesas). A idade média e o Índice de Massa Corpórea (IMC) das eutróficas foram, respectivamente, 68,3±2,7 anos e 23,4±1,6kg/m², e das obesas 69,1±2,7 anos e 33,5±3kg/m². A FPP foi avaliada usando um dinamômetro (JAMAR). O equilíbrio postural estático foi avaliado usando um sistema tridimensional nas condições de olhos abertos (OA) e fechados (OF), durante 90 segundos cada condição. A FPP das idosas eutróficas foi 25,1±4,6kgf e das obesas foi 24,8±5,2kgf, não havendo diferenças significativas. No equilíbrio postural, foram observadas diferenças significativas entre os grupos apenas no deslocamento máximo a-p com AO (p=0,04) e OF (p<0,01), com as idosas obesas apresentando menor deslocamento a-p em relação às eutróficas. Não houve correlação entre o deslocamento máximo a-p com IMC e a FPP. No presente estudo FPP não influenciou o equilíbrio postural estático, enquanto a obesidade foi fator determinante de menor deslocamento ântero-posterior de idosas ativas.

The objective of this study was to investigate the influence of the obesity and handgrip strength on the static balance of active older women in the opened and closed eyes conditions. Thirty one women aged from 65 to 75 years (16 eutrophic and 15 obese) were evaluated. Mean age and BMI of the eutrophic women were, respectively, 68.3±2.7 years and 23.4±1.6kg/m², and of the obese women were 69.1±2.7 years and 33.5±3kg/m². Handgrip strength was evaluated using a dynamometer (JAMAR). A tridimensional sensors system was used to evaluate the static postural balance. The tests were performed for 90 seconds, with eyes opened and closed. The mean handgrip strength of the eutrophic women was 25.1±4.6kgf and of the obese women was 24.8±5.2kgf, (p>0,05). Significant differences between groups were only observed in the maximum displacement with opened eyes (p=0,04) and closed eyes(p<0,01). There was no correlation between the maximum displacement neither with the BMI or the handgrip strength. The present study showed smaller a-p displacement in obese than in eutrophic women, with major statistic difference in the eyes closed condition. In the present study, the handgrip strength did not influence the static balance, however the obesity was a determinant factor for the smaller a-p displacement of the active older women.

Análise do equilíbrio postural estático utilizando um sistema eletromagnético tridimensional / Analysis of static postural balance using a 3d electromagnetic system

A detecção precoce de distúrbios posturais é fundamental para a promoção de intervenções adequadas para pacientes com desequilíbrios. OBJETIVO: Este é um estudo piloto que descreve uma nova ferramenta para avaliação do equilíbrio postural estático. FORMA DE ESTUDO: Coorte contemporânea com corte transversal. MATERIAL E MÉTODO: Foram avaliados 25 voluntários (15 mulheres e 10 homens). Idade média de 25,8±4,2anos, peso 63,9±13,1Kg, estatura 1,68±0,08m e índice de massa corporal 22,3±3,3kg/m2. A posturografia foi realizada por meio da análise de oscilação postural utilizando um equipamento eletromagnético com um sensor fixado sobre o processo espinhoso da 1ª vértebra torácica. Os testes foram realizados com os sujeitos na posição ortostática durante 90 segundos, para as condições de olhos abertos (OA) e fechados (OF) em superfície estável e instável. RESULTADOS: Quando analisada a influência da superfície (estável x instável) para o equilíbrio postural na condição OA, foram observadas diferenças significativas nos parâmetros de trajetória médio-lateral (m-l) (p=0.004) e total (p=0.014) e de velocidade m-l (p=0.004) e total (p=0.014). Na condição OF, foram observadas diferenças significativas em todos os parâmetros estudados (p<0.001). Houve influência da visão em todos os parâmetros apenas na superfície instável (p<0.05). CONCLUSÃO: A ferramenta utilizada se mostrou eficaz para a análise da oscilação postural.

Early detection of postural disorders is essential for timely interventions in patients with imbalance. AIM: A pilot study describing a new tool for evaluating static postural balance. STUDY DESIGN: A cross-sectional study of a contemporary series. MATERIAL AND METHOD: Twenty-five volunteers (15 women and 10 men) were evaluated. The mean age was 25.8 ± 4.2 years, the mean weight was 63.9 ± 13.1Kg, the mean height was 1.68 ± 0.08 m and the body mass index was 22.3±3.3kg/m2. Posturography was done by analysing postural sway with an electromagnetic system; a sensor was attached to the skin over the spinous process of the first thoracic vertebra. Tests were carried out with the subjects in the orthostatic position for 90 seconds, with eyes opened(EO) and closed(EC) on stable and unstable surfaces. RESULTS: When the influence of the surface was analyzed (stable x unstable) in the EO condition, there were significant differences in the middle-lateral parameters (m-l) (p=0.004) and total path (p=0.01), and in the m-l (p=0.004) and total (p=0.014) speed. In the EC condition, there were significant differences in all parameters (p<0.001). The influence of the vision was observed in all parameters only on unstable surfaces (p<0.05). CONCLUSION: The new tool was efficient for analysing postural sway.

Neuronavegador cirúrgico guiado por imagens de ressonância magnética pré-operatória, baseado num transdutor de posição magnético / Surgical neuronavigator guided by preoperative magnetic resonance images, based on a magnetic position sensor

Neurocirurgia guiada por imagem permite ao neurocirurgião navegar dentro do cérebro do paciente, usando imagens préoperatórias como orientação, através do uso de sistemas de rastreamento 3D, durante o procedimento cirúrgico. Seguindo um procedimento de calibração, a posição tridimensional e a orientação dos instrumentos cirúrgicos podem ser transmitidas ao computador. Estas informações espaciais são usadas para acessar a região de interesse nas imagens pré-operatórias com a finalidade de apresentá-las ao cirurgião durante o procedimento cirúrgico. Contudo, quando se faz a craniotomia para a remoção da lesão, o movimento do tecido cerebral pode ser fonte significativa de erro nestes sistemas de navegação. A arquitetura implementada neste trabalho visa o desenvolvimento de um sistema que permite planejamento e orientação cirúrgica guiada por imagem de ultrassom. Para orientação cirúrgica foi desenvolvido um software que permite extrair fatias do volume de imagens de ressonância magnética (IRM), com orientação fornecida por um transdutor espacial baseado em indução magnética (Polhemus®). As fatias extraídas com este software são importantes porque mostram a região do cérebro que o neurocirurgião está observando durante o ato cirúrgico e, além disso, elas podem ser correlacionadas com imagens de ultrassom (IUS) intra-operatórias para detectar e corrigir a deformação do tecido cerebral durante a cirurgia. A ferramenta para navegação pre-cirúrgica foi desenvolvida para fornecer três fatias ortogonais obtidas através do volume de imagens. Na metodologia usada para a implementação do software, foi utilizada a linguagem de programação Python™ e a biblioteca gráfica Visualization Toolkit (VTK). O programa para extrair fatias do volume de IRM permitiu a aplicação de transformações ao volume, com base nos valores de coordenadas fornecidos pelo transdutor de posição Polhemus®.

Image guided neurosurgery enables the neurosurgeon to navigate inside the patient’s brain using pre-operative images as a guide and a tracking system, during a surgery. Following a calibration procedure, three-dimensional position and orientation of surgical instruments may be transmitted to computer. The spatial information is used to access a region of interest, in the pre-operative images, displaying them to the neurosurgeon during the surgical procedure. However, when a craniotomy is involved and the lesion is removed, movements of brain tissue can be a significant source of error in these conventional navigation systems. The architecture implemented in this work intends the development of a system to surgical planning and orientation guided by ultrasound image. For surgical orientation, the software developed allows the extraction of slices from the volume of the magnetic resonance images (MRI) with orientation supplied by a magnetic position sensor (Polhemus®). The slices extracted with this software are important because they show the cerebral area that the neurosurgeon is observing during the surgery, and besides they can be correlated with the intra-operative ultrasound images to detect and to correct the deformation of brain tissue during the surgery. Also, a tool for per-operative navigation was developed, providing three orthogonal planes through the image volume. In the methodology used for the software implementation, the Python™ programming language and the Visualization Toolkit (VTK) graphics library were used. The program to extract slices of the MRI volume allowed the application of transformations in the volume, using coordinates supplied by the position sensor.