Computational Simulation of Breast Tissue with Lesion Characterized by a Thermal Gradient Oriented to Anomalies Smaller than 1 cm of Diameter.

In this work, the computational simulation of thermal gradients related to internal lesions according to the phenomenon of pathological angiogenesis is proposed, this is based on the finite element method, and using a three¬dimensional geometric model adjusted to suit the real female anatomy. The simulation of the thermal distribution was based on the bioheating equation; it was carried out using the COMSOL Multiphysics® software. As a result, the simulation of both internal and superficial thermal distributions associated to lesions smaller than 1 cm and located inside the simulated breast tissue were obtained. An increase in temperature on the surface of the breast of 0.1 ° C was observed for a lesion of 5 mm in diameter and 15 mm in deep. A qualitative validation of the model was carried out by contrasting the simulation of anomalies of 10 mm in diameter at different depths (10, 15 and 20 mm) proposed in the literature, with the simulation of the model proposed here, obtaining the same behavior for the three cases.Clinical Relevance- The 3D computational tool adjusted to suit the anatomy of the real female breast allows obtaining the temperature distribution inside and on the surface of the tissue in healthy cases and with abnormalities associated with temperature elevations. It is an important characteristic of the model when the behavior of the parameters inside the tissue needs to be analyzed.

Power spectral estimation of high-harmonics in echoes of wall resonances to improve resolution in non-invasive measurements of wall mechanical properties in rubber tube and ex-vivo artery.

The aim of this work is to develop a new type of ultrasonic analysis of the mechanical properties of an arterial wall with improved resolution, and to confirm its feasibility under laboratory conditions. MOTIVATION: it is expected that this would facilitate a non-invasive path for accurate predictive diagnosis that enables an early detection & therapy of vascular pathologies. In particular, the objective is to detect and quantify the small elasticity changes (in Young's modulus E) of arterial walls, which precede pathology. A submicron axial resolution is required for this analysis, as the periodic widening of the wall (under oscillatory arterial pressure) varies between ±10 and 20 µm. This high resolution represents less than 1% of the parietal thickness (e.g., << 7 µm in carotid arteries). The novelty of our proposal is the new technique used to estimate the modulus E of the arterial walls, which achieves the requisite resolution. It calculates the power spectral evolution associated with the temporal dynamics in higher harmonics of the wall internal resonance f0. This was attained via the implementation of an autoregressive parametric algorithm that accurately detects parietal echo-dynamics during a heartbeat. Thus, it was possible to measure the punctual elasticity of the wall, with a higher resolution (> an order of magnitude) compared to conventional approaches. The resolution of a typical ultrasonic image is limited to several hundred microns, and thus, such small changes are undetected. The proposed procedure provides a non-invasive and direct measure of elasticity by doing an estimation of changes in the Nf0 harmonics and wall thickness with a resolution of 0.1%, for first time. The results obtained by using the classic temporal cross-correlation method (TCC) were compared to those obtained with the new procedure. The latter allowed the evaluation of alterations in the elastic properties of arterial walls that are 30 times smaller than those being detectable with TCC; in fact, the depth resolution of the TCC approach is limited to ≈20 µm for typical SNRs. These values were calculated based on echoes obtained using a reference pattern (rubber tube). The application of the proposed procedure was also confirmed via "ex-vivo" measurements in pig carotid segments.

Prototipo de una Prótesis Mioeléctrica para la Emulación de una Articulación de Codo / Prototype of a Myoelectric Prosthesis for the Emulation of an Elbow Joint

En este trabajo se describe el desarrollo de un prototipo de prótesis mioeléctrica para la articulación de codo. Se dividió en tres partes, en la primera se describe el acondicionamiento de la señal mioeléctrica (SME) donde se propuso un circuito que está formado por una etapa de pre-amplificación, seguida de una etapa de filtrado, otra etapa de amplificación y por último la etapa de rectificación. Este circuito cumple con las especificaciones para la detección de la SME según el estado del arte. En la segunda parte se describe el procesamiento de la SME basado en el método TKEO, este se implementó en MatLAB (MathWorks- Natick, Massachusetts, USA) con la finalidad de detectar la actividad muscular, y resultó robusto y eficiente. La tercera parte se enfoca al diseño y construcción del prototipo, para el sistema de transmisión se usó un par de engranes y para el sistema de actuación los actuadores eléctricos; ambos se definieron según los criterios que se describen en este trabajo. Finalmente, se integraron las tres partes para la emulación de los movimientos flexión y extension del prototipo, haciendo uso del microprocesador (Arduino UNO) y del módulo de control de motores (Controlador de servo 1350 de Pololu).

In this paper the development of a prototype for a myoelectric prosthesis elbow joint is described. It is divided into three parts; the first is the conditioning of the myoelectric signal (SME) which proposed a circuit that is formed by a stage of pre-amplification, followed by a stage of filtering, another stage of amplification and finally a stage of rectification. This circuit complies with the specifications for the detection of the SME according to the state of the art. The second part is the processing of the SME based on the method TKEO, this was implemented in MatLAB (MathWorks - Natick, Massachusetts, USA) in order to detect if the muscle is active or not, and proved to be robust and efficient. The third part focuses on the design and realization of the prototype, in the system of transmission was used a couple of gears and for the system of actuation were electrical actuators; both were defined considering several criteria referred to in this work. Finally, the three parts were joined for the emulation of flexion and extension movements of the prototype, using the microprocessor (Arduino UNO) and control module (controller servo Pololu 1350).

Possible patient early diagnosis by ultrasonic noninvasive estimation of thermal gradients into tissues based on spectral changes modeling.

To achieve a precise noninvasive temperature estimation, inside patient tissues, would open promising research fields, because its clinic results would provide early-diagnosis tools. In fact, detecting changes of thermal origin in ultrasonic echo spectra could be useful as an early complementary indicator of infections, inflammations, or cancer. But the effective clinic applications to diagnosis of thermometry ultrasonic techniques, proposed previously, require additional research. Before their implementations with ultrasonic probes and real-time electronic and processing systems, rigorous analyses must be still made over transient echotraces acquired from well-controlled biological and computational phantoms, to improve resolutions and evaluate clinic limitations. It must be based on computing improved signal-processing algorithms emulating tissues responses. Some related parameters in echo-traces reflected by semiregular scattering tissues must be carefully quantified to get a precise processing protocols definition. In this paper, approaches for non-invasive spectral ultrasonic detection are analyzed. Extensions of author's innovations for ultrasonic thermometry are shown and applied to computationally modeled echotraces from scattered biological phantoms, attaining high resolution (better than 0.1 °C). Computer methods are provided for viability evaluation of thermal estimation from echoes with distinct noise levels, difficult to be interpreted, and its effectiveness is evaluated as possible diagnosis tool in scattered tissues like liver.

A performance analysis of echographic ultrasonic techniques for non-invasive temperature estimation in hyperthermia range using phantoms with scatterers.

Optimization of efficiency in hyperthermia requires a precise and non-invasive estimation of internal distribution of temperature. Although there are several research trends for ultrasonic temperature estimation, efficient equipments for its use in the clinical practice are not still available. The main objective of this work was to research about the limitations and potential improvements of previously reported signal processing options in order to identify research efforts to facilitate their future clinical use as a thermal estimator. In this document, we have a critical analysis of potential performance of previous ultrasonic research trends for temperature estimation inside materials, using different processing techniques proposed in frequency, time and phase domains. It was carried out in phantom with scatterers, assessing at their specific applicability, linearity and limitations in hyperthermia range. Three complementary evaluation indexes: technique robustness, Mat-lab processing time and temperature resolution, with specific application protocols, were defined and employed for a comparative quantification of the behavior of the techniques. The average increment per degrees C and mm was identified for each technique (3 KHz/ degrees C in the frequency analysis, 0.02 rad/ degrees C in the phase domain, while increments in the time domain of only 1.6 ns/ degrees C were found). Their linearity with temperature rising was measured using linear and quadratic regressions and they were correlated with the obtained data. New improvements in time and frequency signal processing in order to reveal the potential thermal and spatial resolutions of these techniques are proposed and their subsequent improved estimation results are shown for simulated and measured A-scans registers. As an example of these processing novelties, an excellent potential resolution of 0.12 degrees C into hyperthermia range, with near-to-linear frequency dependence, could be achieved. Specifically defined "numerical" and physical multi-scatter phantoms are described, which mimic ultrasound velocity in tissues of about 1560 m/s @ 35 degrees C and have a quasi-uniform internal scattering structure designed to assure standard signal patterns adequate for processing comparisons in the same time and sound velocity conditions for all the techniques analyzed, and to obtain easily repeatable multi-pulse echo-patterns. A perfect lineal dependence (100% of correlation coefficient) between the unitary average increment measured by each technique and temperature rising was observed while working with simulated A-scan registers, where all the parameters are under an accurate control. Nevertheless a very small quadratic tendency appeared in the results obtained from experimental echo registers, which are more similar to a real tissues case. It would be an interesting future work to analyze the behavior of these techniques in real tissues in order to confirm or reject this light quadratic tendency. Finally, new methods were detailed and applied in order to precisely quantify the advantages of each estimation technique; their respective intrinsic limitations were also underlined.