An integrated approach to whole-body vibration

Obiettivo di questa tesi è la determinazione e quantificazione degli effetti della whole-body vibration al corpo umano, in termini di consumo energetico, tramite un approccio globale e integrato. L’obiettivo è ottenuto considerando il corpo umano come una struttura organica complessa. Allo scopo di comprendere come questo risponda alle vibrazioni verticali, il consumo energetico del corpo umano è stato misurato per mezzo della variazione della temperatura superficiale con tecniche di misurazione a termografia infrarossa. Lo spostamento dei muscoli invece con il sistema di analisi di movimento Vicon MX. Infine, per quanto riguarda il consumo di ossigeno con il sistema telemetrico Cosmed K4. Il primo passo è stato l’istituzione di un protocollo appropriato che soddisfi l’obiettivo di questo studio. Infatti, la mancanza di coerenza nei protocollo di whole-body vibration che si trovano allo stato dell’arte, ha reso essenziale l’istituzione di un apposito protocollo, ed a questo scopo è stata definita la struttura dell’esperimento. Di conseguenza, è stata avviata una serie di prove per esaminare la risposta del corpo umano alle vibrazioni verticali, cambiando la durata e la frequenza della vibrazione, nonché la durata del periodo di riposo. In totale, quattro persone in piedi sono state sottoposte a vibrazioni verticali, in una pedana vibrante, a frequenze da 20 a 50 Hz. Dopo l’instaurazione del protocollo finale, sono stati avviate una serie di prove di laboratorio. In particolare, sono state scelte tre frequenze per le vibrazioni: 20, 30 e 45 Hz. I risultati ottenuti più interessanti di questo studio, riguardano il consumo di ossigeno, la temperatura superficiale e i coefficienti di trasmissibilità dell’accelerazione.The objective of this thesis is to determine and quantify the effects of whole-body vibration to the human body in terms of energy expenditure, by means of a global and integrated approach. This objective is attained by considering the human body as a complex organic structure. In order to understand how it responds to vertical vibrations, the energy expenditure of the human body was measured by means of the variation in superficial temperature with the aid of infrared thermography, the displacement of the muscles with the aid of the Vicon MX motion analysis system and the oxygen uptake with the aid of the Cosmed K4 telemetric system. The establishment of an appropriate protocol which satisfies the aim of this study was the first goal. The lack of consistency in whole-body vibration protocols in the current published studies makes the establishment of an appropriate protocol essential, and in this sense, an experiment setup was implemented. Therefore, a series of experiments was conducted to examine the response of the human body to vertical vibrations, changing the duration and the frequency of vertical vibration, and the duration of rest period. A number of four persons were subjected to vertical vibrations on a vibrating table in a standing position at a frequency ranging from 20 to 50 Hz. After the establishment of the final protocol, a series of laboratory experiments took place. Three different vibration frequencies were chosen: 20, 30 and 45 Hz corresponding to three different tests. The most interesting findings regard the oxygen consumption, the superficial temperature evolution, and the transmissibility coefficients for the acceleration

A Transcutaneous Data and Power Transfer System for Osteogenesis Monitoring Sensors

Implant devices are widely used in health care applications such as life support systems, patient rehabilitation devices and patient monitoring devices. Medical implants have enabled physicians to obtain relevant real time information regarding an organ, or a site of interest with in the body and suggest treatment accordingly. In some cases, the position of the implant within the body or threats of infections prevents wired communication techniques to extract information from the implant. Wireless communication is the alternative in such cases. Distraction osteogenesis is one such application where wireless communication can be established with callus growth monitoring sensors to obtain bone growth data and activate distraction device. As a solution for wireless communication, the computational design, fabrication and testing of a spiral antenna that can operate in the 401-406 MHz Medical Implant Communication Services (MICS) band is detailed. The proposed system uses ZL70103 MICS band transceiver from Microsemi Corporation and enables wireless communication with the implant. Antenna is tested in an in-vivo system that makes use of biomimetic material and pig femur bone to mimic an application environment. Power requirements for the implant actuator system that performs distraction cannot be satisfied by a single battery. Percutaneous wires for powering the implant poses threats of infection and frequent surgeries for battery replacement alters patient’s immune systems. Wireless charging is viable solution in this case. A short range inductive power transfer system prototype is designed and tested on a custom testbed to analyze the power transfer efficiency with change in distance

An Investigation of Radiometer and Antenna Properties for Microwave Thermography

Microwave thermography obtains information about the subcutaneous body temperature by a spectral measurement of the intensity of the natural thermally generated radiation emitted by the body tissues. At lower microwave frequencies the thermal radiation can penetrate through biological tissue for significant distances. The microwave thermal radiation from inside the body can be detected and measured non-invasively at the skin surface by the microwave thermography technique, which uses a radiometer to measure the radiation which is received from an antenna on the skin. In the microwave region the radiative power received from a volume of material has a dependence on viewed tissue temperature T(r) of the form, where k is the Boltzmann's constant, B the measurement bandwidth, c(r) is the relative contribution from a volume element dv (the antenna weighting function). The weighting function, c(r), depends on the structure and the dielectric properties of the tissue being viewed, the measurement frequency and the characteristics of the antenna. In any practical radiometer system the body microwave thermal signal has to be measured along with a similar noise signal generated in the radiometer circuits. The work described in this thesis is intended to lead to improvement in the performance of microwave thermography equipment through investigations of antenna weighting functions and radiometer circuit noise sources. All work has been carried out at 3.2 GHz, the central operating frequency of the existing Glasgow developed microwave thermography system. The effects of input circuit losses on the operation of the form of Dicke radiometer used for the Glasgow equipment have been investigated using a computational model and compared with measurements made on test circuits. Very good agreement has been obtained for modelled and measured behaviour. The losses contributed by the microstrip circuit structure, that must be used in the radiometer at 3.2 GHz, have been investigated in detail. Microwave correlation radiometry, by "add and square" method, has been applied to the received signals from a crossed-pair antenna arrangement, the antennas being arranged to view a common region at a certain depth. The antenna response has been investigated using a noise source and by the nonresonant perturbation technique. The received pattern formed by the product of the individual antenna patterns gives a maximum depth in phantom dielectric material. The depth can be adjusted by changing the spacing of the antennas and the phase in an antenna path. However, the pattern is modulated by a set of positive and negative interference fringes so that the complete receive pattern has a complicated form. On uniform temperature distributions the total radiometric signal is zero with the positive and negative contributions cancelling each other out. The fringe modulation can be removed by placing the antennas close enough together, The pattern is then simple and gives a modest maximum response at a known depth in a known material. The radiometer system remains sensitive to the temperature gradients only and the wide range of dielectric properties and tissue structures in the region being investigated usually makes the system response difficult to interpret. For crossed-pair antennas in phase the effective penetration depth in high-and medium-water content tissues is about 2.5 cm at a frequency of 3.2 GHz. The field pattern observed was of the form expected from the measurements of the individual antenna behaviour with the appropriate interference pattern superimposed. The nonresonant perturbation technique has been developed and applied to assist the development of the medical application of both microwave thermographic temperature measurement and microwave hyperthermia induction. These techniques require the electromagnetic field patterns of the special antennas used to be known. These antennas are often formed by short lengths of rectangular or cylindrical waveguide loaded with a low-loss dielectric material to achieve good coupling to body tissues. The high microwave attenuation in biological materials requires the field configurations to be measured close to the antenna aperture in the near-field wave. The nonresonant perturbation is a simple technique which can be used to measure electromagnetic fields in lossy material close to the antenna. It has been applied here to measure accurately the antenna weighting function and the effective penetration depth in tissue simulating dielectric phantom materials. (Abstract shortened by ProQuest.)