Sensitivity analysis on imaging the calcaneus using microwaves

Fajardo, Jesús E.; Vericat, Fernando; Irastorza, G; Carlevaro, C. Manuel; Irastorza, Ramiro M.

doi:10.1088/2057-1976/ab3330

Cited by 5 publications

(8 citation statements)

References 35 publications

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“…The geometry of each model considers the whole heel as a two dielectric media: (I) surrounding tissue (muscle/tendon), and (II) calcaneus (considered as trabecular bone). This simplified model is based on the results presented in the sensitivity analysis of our previous work [10]. The range of values of conductivity and permittivity of the materials employed in computer model are shown in Table 1 [10].…”

Section: Electromagnetic Simulationsmentioning

confidence: 99%

“…In the simulations we computed the absolute value of the total field (|E z |) in the receiver antennas (Rx). This magnitude was measured in the seven receiver antennas right in front of the transmitter (Tx), since in [10] was shown that these antennas have considerably more information than the others. A complete simulation gives a total of 7×16 = 112 measurement points.…”

Section: Electromagnetic Simulationsmentioning

confidence: 99%

“…Phase measurement presents considerable practical difficulties and hardware cost which makes amplitudeonly methods highly attractive [7,8,9]. Simulating the same array of antennas, Fajardo et al [10] have computationally studied the feasibility of detecting dielectric properties of the calcaneus with phaseless data of two dimensional (2D) models. The authors have concluded that the problem is highly sensitive to the conductivity of the tissues that surround the calcaneus and the conductivity of the calcaneus itself.…”

Section: Introductionmentioning

confidence: 99%

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Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks

Fajardo

Lotto

Vericat

et al. 2019

Med Biol Eng Comput

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The aim of this study is to use a Multilayer Perceptron (MLP) Artificial Neural Network (ANN) for phaseless imaging the human heel (modeled as a bilayer dielectric media: bone and surrounding tissue) and the calcaneus cross-section size and location using a two dimensional (2D) microwave tomographic array. Computer simulations were performed over 2D dielectric maps inspired by Computed Tomography (CT) images of human heels for training and testing the MLP. A morphometric analysis was performed to account for the scatterer shape influence on the results. A robustness analysis was also conducted in order to study the MLP performance in noisy conditions. The standard deviations of the relative percentage errors on estimating the dielectric properties of the calcaneus bone were relatively high. Regarding the calcaneus surrounding tissue, the dielectric parameters estimations are better, with relative percentage error standard deviations up to ≈ 15%. The location and size of the calcaneus are always properly estimated with absolute error standard deviations up to ≈ 3 mm.

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Section: Electromagnetic Simulationsmentioning

confidence: 99%

Section: Electromagnetic Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks

Fajardo

Lotto

Vericat

et al. 2019

Med Biol Eng Comput

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“…The current state-of-art in using MWT for bone imaging focuses on extracting the electrical properties of the calcaneus, which is also called the heel bone [6,[21][22][23]. In this paper, microwave imaging is performed across the lower midsection of the leg to estimate the electrical properties of the tibia and/or fibula bones; the tibia is the bigger bone located in the shaft of the lower leg, while the fibula is the smaller bone.…”

Section: Introductionmentioning

confidence: 99%

A numerical feasibility study on monitoring bone health using microwave tomography: towards a wearable design

Alkhodari

Zakaria

Qaddoumi

2021

Preprint

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Background: Osteoporosis is the major cause of bone weakness and fragility in more than 10 million people in the United States. This disease causes bone fractures in the hip or spine, which result in increasing the risk of disabilities or even death. The current gold standard in osteoporosis diagnostics, X-ray, although reliable, it uses ionizing radiations that makes it unfeasible for early and continuous monitoring applications. Recently, microwave tomography (MWT) has been emerging as a biomedical imaging modality that utilizes non-ionizing electromagnetic signals to screen bones' electrical properties. These properties are highly correlated to bones' density, which makes MWT to be an effective and safe alternative for frequent testing in osteoporosis diagnostics. Results: Both of the conventional and wearable simulated systems were successful in localizing the tibia and fibula bones in the enhanced MWT images. Furthermore, structure extraction of the leg’s model from the blind MWT images had a minimal error compared to the original one (L2-norm: 15.60%). Under five sequentially-incremental bone volume fraction (BVF) scenarios simulating bones' treatment procedure, bones were detected successfully and their density were found to be inversely proportional to the real-part of the relative permittivity values. Conclusions: This study paves the way towards implementing a safe and user-friendly MWT system that can be wearable to monitor bone degradation or treatment for osteoporosis cases. Methods: An anatomically-realistic finite-element (FE) model representing the human leg was initially generated and filled with corresponding tissues' (skin, fat, muscles, and bones) dielectric properties. Then, numerically, the forward and inverse MWT problems were solved within the framework of the finite-element method contrast source inversion algorithm (FEM-CSI). Furthermore, image reconstruction enhancements were investigated by utilizing prior information about different tissues as an inhomogeneous background as well as by adjusting the imaging domain and antennas locations based on the prior structural information. In addition, the utilization of a medically-approved matching medium that can be used in wearable applications, namely an ultrasound gel, was suggested. Additionally, an approach based on k-means clustering was developed to extract the prior structural information from blind reconstructions. Lastly. the enhanced images were used to monitor variations in BVF.

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“…La definición del primero fue inspirado en [100] y el segundo se basó en el Método de Morris [101] (ver Apéndice C). Estos métodos se evaluaron en los parámetros de dispersión (parámetros S) sólo para el módulo del campo eléctrico, aunque también realizamos la evaluación del comportamiento de la fase en [102].…”

Section: Análisis De Sensibilidad Aplicación a La Tmo En El Calcáneounclassified

Tomografía de microondas

Freites¹,

Ernesto²

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En este trabajo se estudió la factibilidad de la detección de cambios en las propiedades dieléctricas del hueso calcáneo mediante la medición de amplitud de microondas en un arreglo tomográfico de antenas monopolo. Con este fin, se llevaron a cabo análisis de sensibilidad local y global desde el punto de vista del problema electromagnético directo. La principal conclusión es que efectivamente es posible detectar, con equipos disponibles en la actualidad, cambios en las propiedades dieléctricas del hueso mediante mediciones de amplitud de campo eléctrico en arreglos tomográficos de microondas. En particular estos análisis muestran que el talón humano puede ser modelado a nivel de sus propiedades dieléctricas, como dos medios: calcáneo y tejido circundante. Basados en estos resultados, y a fin de implementar el problema electromagnético inverso, se estudiaron distintos modelos de redes neuronales artificiales como estimadores de parámetros dieléctricos y geométricos de dispersores cilíndricos homogéneos y heterogéneos, tanto bidimensionales como tridimensionales contenidos en un arreglo tomográfico similar al usado para el problema directo. Encontramos factibilidad en el uso del método, incluso para situaciones de alto contraste dieléctrico, donde los algoritmos más simples fallan. Esto sin mencionar que dichos algoritmos, a diferencia de los basados en redes neuronales artificiales, requieren en su mayoría información de ambos, amplitud y fase, para el proceso de inversión. Este resultado establece un método novedoso de calibración y medición de muestras a partir de información de amplitud de microondas, basado en redes neuronales artificiales. Aplicamos el método al problema de la reconstrucción de las propiedades dieléctricas y geométricas del calcáneo, concluyendo que con estas técnicas de redes neuronales y a partir de información de sólo la amplitud del campo eléctrico, es posible estimar de manera precisa la posición y el tamaño de este tejido y también, aunque con menor precisión, sus propiedades dieléctricas. En particular, el método resulta útil para estimar las propiedades dieléctricas del tejido alrededor del calcáneo, lo cual serviría para acelerar de manera significativa algoritmos iterativos determinísticos clásicos diseñados con ese fin.

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Sensitivity analysis on imaging the calcaneus using microwaves

Cited by 5 publications

References 35 publications

Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks

Microwave tomography with phaseless data on the calcaneus by means of artificial neural networks

A numerical feasibility study on monitoring bone health using microwave tomography: towards a wearable design

Tomografía de microondas

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