Mechanical properties of soft human tissue are linked to their pathological state. One way to assess these properties is through the Young modulus measurement, which is related to the shear wave speed in the medium when considering tissues as nearly incompressible. In order to characterize its elastic properties using sonoelastography, we introduce a new technique for shear wave estimation from a static interference pattern based on Shear Wave Holography. A relation between the mathematical representation of the interference pattern and the local shear speed is derived using the Phase Derivative approach. The experimental scheme is presented, detailing the advantages of the new configuration. Homogeneous and heterogeneous elastic media were simulated, generating an interference pattern on them. The shear speed estimation algorithm was explained and applied to obtain the speed map, calcul...

Architectural and archaeological heritage is the most representative part of history of a country. For these reasons, over the years, the scientific community has focused its attention on three-dimensional (3D) modeling techniques, conservation, structural analysis and other related applications. Laser scanning, shape from structured light, shape from silhouette, shape from video and shape from photometry are among the techniques that have been used over the past years for 3D modeling of archeological heritage. The application of 3D modeling can be found in several disciplines. In Architecture, it is used to generate digital models from which drawings can be produced. Aerial and terrestrial photogrammetry Photogrammetry is commonly used for digitization of 3D models in different applications due to the fast acquisition process and low cost of equipment. Digitization of structures with te...

Imaging of musculoskeletal tissue dynamics is currently an exploratory field with the goal of aiding rehabilitation and performance evaluation of pathological or asymptomatic patients. In this pilot study, initial elasticity assessments of the biceps brachii were conducted in a novel crawling wave sonoelastography (CWS) system implemented on a research ultrasound instrument with graphical processing unit capabilities, displaying quantitative elasticity values at 4 frames per second. The CWS system computes the tissue stiffness with the generation of an interference pattern from external vibrators, which can overcome depth limitations of imaging systems with internal excitation sources. Validation on gelatin-based phantoms reported low bias of elasticity values (4.7%) at low excitation frequencies. Preliminary results on in vivo muscle characterization are in accordance with average elast...

La realidad aumentada (AR) aplicada al patrimonio cultural pretende mejorar la experiencia de aprendizaje en sitios arqueológicos, no solo para los visitantes sino también para los investigadores. La estimación de Pose 3D es un problema común en aplicaciones para AR, reconocimiento de objetos, modelado 3D, entre otros. Los sistemas AR utilizan diferentes métodos para estimar la pose de la cámara: detección de bordes y detección de puntos clave, entre otros. La elección del método a utilizar depende de las características del escenario a detectar. En este trabajo se realiza un estudio comparativo de los principales métodos de estimación de pose basados ​​en modelos 3D. Además, presentamos la implementación y validación de un algoritmo de estimación de pose, orientado a la inicialización de un sistema AR aplicado a la “Huaca de la Luna”, una pirámide de ladrillos...

Elastography is a modality that estimates tissue stiffness and, thus, provides useful information for clinical diagnosis. Attention has focused on the measurement of shear wave propagation; however, many methods assume shear wave propagation is unidirectional and aligned with the lateral imaging direction. Any deviations from the assumed propagation result in biased estimates of shear wave speed. To address these challenges, directional filters have been applied to isolate shear waves with different propagation directions. Recently, a new method was proposed for tissue stiffness estimation involving creation of a reverberant shear wave field propagating in all directions within the medium. These reverberant conditions lead to simple solutions, facile implementation and rapid viscoelasticity estimation of local tissue. In this work, this new approach based on reverberant shear waves was e...

The determination of shear wave speed is an important subject in the field of elastography, since elevated shear wave speeds can be directly linked to increased stiffness of tissues. MRI and ultrasound scanners are frequently used to detect shear waves and a variety of estimators are applied to calculate the underlying shear wave speed. The estimators can be relatively simple if plane wave behavior is assumed with a known direction of propagation. However, multiple reflections from organ boundaries and internal inhomogeneities and mode conversions can create a complicated field in time and space. Thus, we explore the mathematics of multiple component shear wave fields and derive the basic properties, from which efficient estimators can be obtained. We approach this problem from the historic perspective of reverberant fields, a conceptual framework used in architectural acoustics and rela...

Quantifying the local stiffness of muscular tissue can be a useful tool for the improvement of diagnosis, treatment or monitoring of muscle abnormality-related diseases. Shear wave elastography techniques provide information about tissue stiffness by measuring the shear wave speed (SWS). Recently, a new framework involving the generation of a reverberant shear wave field that propagates in all directions within the medium was proposed. The aim of this study is to evaluate the feasibility of Reverberant Shear Wave Elastography (R-SWE) for the in vivo assessment of the viscoelastic properties of skeletal muscle, using the biceps brachii. Four experiments were performed at a vibration frequency range between 200-300 Hz in steps of 50 Hz, with the ultrasound transducer placed along the muscle fibers in both relaxed and contracted (MVC) states. The estimation of the SWS and a dispersion analy...

Crawling Waves Sonoelastography (CWS) is an elastography technique based on an interference pattern produced by the application of two external vibration sources. In this study, a 3D printed holder was designed to overcome the compatibility limitations of normal excitation modules for different ultrasound systems, previously developed in the literature. This holder was assembled with a transducer and two voice coil actuators, and its performance was tested in homogeneous and inclusion tissue-mimicking phantom. A phase derivative estimator was used to reconstruct the shear wave speed (SWS) map. The coefficient of variation (CV), bias and contrast-to-noise ratio (CNR) were used as quantitative metrics for comparison. These metrics have shown a comparable SWS estimation in the background (SWSb) of the homogeneous phantom with previous studies (e.g. SWSb = 3.58± 0.42 m/s). In the same way, ...

Skin diseases cause changes in the elasticity of the skin. Recently, a new ultrasound method which combines crawling waves elastography with a high-frequency ultrasound (HF-US) system was reported for the estimation of skin elasticity. This study applies crawling waves method with an HF-US system in homogeneous and heterogeneous phantoms with similar shear wave speeds found in the literature to validate this technique. In addition, estimation performance was compared between the Phase Derivative (PD) estimator and the Regularized Wave-length Average Velocity Estimator (R-WAVE). Results corroborate the feasibility of this method. Additionally, it suggests that R-WAVE estimator can provide better measurements than PD with a lower coefficient of variation and fewer artifacts. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

La tierra ha sido un material de construcción tradicional para construir estructuras en muchos continentes diferentes. En particular, los edificios de adobe están ampliamente difundidos en Sudamérica, y en Perú donde forman parte de la identidad cultural de la nación. Hoy en día, el conocimiento de los edificios de adobe existentes está lejos de una comprensión completa del sistema constructivo y una monitorización de la salud estructural (SHM) puede cuantificar y reducir las incertidumbres sobre su comportamiento estructural sin causar daños a los edificios. En este proceso, es deseable la implementación de herramientas automáticas para la extracción de características de los parámetros modales. En particular, la automatización es importante porque, durante una monitorización a largo plazo, se registra una enorme cantidad de datos y la comprobación directa de los datos...

Constant survey of historical constructions is very important to ensure their conservation. In the case of ancient buildings, their use, the materials aging, vibrations, environmental effects (temperature, rain, snow) and seismic events are all possible causes of deterioration and damage. A continuous Structural Health Monitoring can provide useful information for automated condition evaluations of the health-state of historic buildings; however, it is known that the effects of environmental conditions such as the variation of temperature and humidity can make this assessment difficult. Therefore, continuous monitoring of environmental conditions and dynamic parameters is needed to develop suitable models to assess the current health-state. Additionally, historical structures could be located in a place where the harsh local conditions (viability, electricity, internet connection, etc.) ...

Skin elastic properties change during a cutaneous disorder or in the aging process. Deep knowledge of skin layers helps monitoring and diagnosing structural changes. High frequency ultrasound (HF-US) has been recently introduced to diagnose and evaluate some dermatological disorders in the clinical practice. US elastography adds elasticity information of the analyzed tissue. In particular, harmonic elastography estimates the speed of shear waves produced by external vibration sources, in order to relate the shear wave speed to the Young's modulus. In the epidermis and dermis layers, shear waves are not generated; in contrast, surface acoustic waves (SAWs) exist as they propagate in the top of the tissue. This study uses crawling wave sonoelastography for the estimation of SAWs in human thigh dermis in vivo. Experiments were performed in ten volunteers in the range of 200 - 500 Hz. As oth...

Total Station has been one of the most common acquisition devices for achieving maps through topographic survey. Nowadays, Terrestrial Laser Scanner (TLS) and Photogrammetry are commonly used to generate accurate meshes. In addition, commercial products such as Kinect offer low cost technology to acquire point-cloud information. The present paper aims to measure the accuracy of these digital modelling techniques by employing elevation contour maps, surface deviations and distance measurements. For this purpose, a 450 m sector of the Qhapaq Nan located in Lima-Peru, was selected as a case of study. A camera-enabled drone was used for acquiring pictures to obtain a high-resolution photogrammetric model. Subsequently, a 3D survey of the monument was conducted with a time-of-flight laser scanner. Contour elevation lines where extracted from TLS, Photogrammetry and Total Station models at the...

In this work, we study the conditions in which a reverberant field is created by varying the number and locations of multiple mechanical sources, and then fitting axial and lateral autocorrelation profiles to theoretical models. Numerical simulation showed that at least 60 incident plane waves were necessary to generate a R-SWF. The general trend is that by applying more incident waves, the coefficient of determination improves and the error decreases. We report a bias error lower than 6% in the mean shear wave speed (pmb{C}{s}). Phantom experiments showed a similar tendency. Moreover, we demonstrated that the creation of a R-SWF based on the superposition of incident plane waves was possible. At least three vibration sources located at the top of the phantom surface were necessary to measure an average pmb{C}{s} with an error less than 9%. © 2020 IEEE.

Breast cancer is a public health problem with ? 1.7 million new cases per year worldwide and with several limitations in the state-of-art screening techniques. Ultrasound elastography involves a set of techniques intended to facilitate the noninvasive diagnosis of cancer. Among these, Vibro-elastography is an ultrasound-based technique that employs external mechanical excitation to infer the elastic properties of soft tissue. In this paper, we evaluate the Vibro-elastography performance in the differentiation of benign and malignant breast lesions. For this study, a group of 18 women with clinically confirmed tumors or suspected malignant breast lesions were invited to participate. For each volunteer, an elastogram was obtained, and the mean elasticity of the lesion and the adjacent healthy tissue were calculated. After the acquisition, the volunteers underwent core-needle biopsy. The hi...

Se evalúa la toxicidad del extracto acuoso en cocimiento de la harina de maca en dos organismos acuáticos, un invertebrado la Artemia franciscana y un vertebrado el pez Guppy (Poecilia reticulata). Así mismo, se evalúa la toxicidad aguda por vía intraperitoneal en el ratón (Mus musculus) que es el modelo animal comúnmente utilizado para ensayos preclínicos a nivel de laboratorios. Se comprobó que existe toxicidad del Lepidium meyenii para estos tres animales que dependen de la dosis y el tiempo de exposición.

Pneumonia is one of the major causes of child mortality. Unfortunately, in developing countries there is a lack of infrastructure and medical experts in rural areas to provide the required diagnostics opportunely. Lung ultrasound echography has proved to be an important tool to detect lung consolidates as evidence of pneumonia.

Pneumonia is one of the major causes of child mortality, but it is curable if one can achieves early diagnostics. Unfortunately, in developing countries there is a lack of infrastructure and medical experts in rural areas to provide the required diagnostics opportunely. Lung ultrasound echography has proved to be an important tool to detect lung consolidates as evidence of pneumonia. The use of ultrasound to detect pneumonia is limited by the image analysis for interpretation, which is carried by human experts. Pattern recognition and image analysis is a potential tool to facilitate recognition of pneumonia consolidates in absence of medical experts for automatic diagnostics. To perform an automatic analysis of lung ultrasound images for pneumonia detection, the noise introduced by the image portion of the skin, notably complicates the processing and interpretation. This paper presents a...

Advances in information and communications technologies provide a new opportunity to improve the access to healthcare in remote rural areas (RA) where there is a lack of infrastructure and medical experts. This paper implements a new model for tele-ultrasound (US) based on volumetric sweep imaging protocols specially designed for the acquisition of US. Non-physician health personnel from the RA are trained on the use of these protocols in a few days. The operator utilizes the medical box (MB), a specially designed telecommunication system, to guide, compress, encrypt and transmit the US sweeps through the cloud to the radiologist who performs the diagnosis remotely. The report is automatically sent back to the MB. The system was able to send US volumetric images with poor connectivity conditions in 6 minutes on average. These results of implementing this tele-ultrasound model in RAs are ...

We thank Medical Imaging Ministries of the Americas and Medical Innovation and Technology for allowing the publication of their illustrated posters and videos as supplemental material; Pilar Stewart, Thomas Chaumont, Italo Fernandez Salgado, Silvina Zabala‐Travers, MD, Nicole Stephens, and Cheree Harlee, RDMS, for assistance in the study; Jane Lichorowic and Nadezhda Kiriyak for illustrating Figure 1; and Sarah Klingenberger for help with the figures. This work was supported by CONCYTEC/FONDECYT (175‐FONDECYT‐DE), Innovate Peru (596‐INNOVATEPERU‐EDAI‐2015 and PR‐PVE‐201), and the Pontificia Universidad Catolica del Peru (PUCP DGI‐2016‐345). Dr Castaneda and all authors affiliated with Medical Innovation and Technology have a financial stake in Medical Innovation and Technology, which seeks to deploy ultrasound in rural areas. All data analysis and manuscript writing w...