In biomechanical applications where an ultrasound signal is used to determine the position of a specific organ or tissue, like for example a bone, a so-called A-mode ultrasonography is used. A ultrasonic pulse is generated by a transducer, injected in the tissue to be examined, and then the echoes are received and processed. Echoes are generated by changes in acoustic impedance in the medium, like for example a change of tissue from muscle to bone. To determine the position of the reflecting interface, the time-of-flight is measured and, utilizing well-know values for the transmission speed, the distance or depth is computed. If the localization device is to be designed to be small, wearable, and low-power, it is expected that the signal willbe of worse quality with respect to traditional ultrasonography systems, especially under the point of view of signal-to-noise ratio. In these conditions, the reliability of the algorithm that implement the time-of-flight calculation is of paramount importance. In this paper, a simulated soft tissue?bone interface (implemented with an ultrasound gel-pad) has been measured with intentionally low excitation signals and with the presence of imperfections similar to those expected in a physiological system. Several classic algorithms have been tested and benchmarked in this condition, and a new method with better reliability and repeatability is proposed.
Palabras clave: Time-of-flight, ultrasonic sensors, biomecanical systems, cross-correlation, kurtosis.
IEEE International Instrumentation and Measurement Technology Conference, Turín, Turín (Italia). 22 mayo 2017
Fecha de publicación: mayo 2017.
J.M. Fresno, R. Giannetti, G. Robles, A survey of time-of-flight algorithms to determine bone positions in movement, IEEE International Instrumentation and Measurement Technology Conference - I2MTC 2017. ISBN: 978-1-5090-3596-0, pp. 335-340, Turín, Italia, 22-25 Mayo 2017