Incident and reflected two waves correlation with cancellous bone structure

The correlation in bone microstructure for ultrasound pulse echo technique is still less accurate compared to through transmission technique. Previous works demonstrated, reflected two modes wave has significant association with bone porosity. The paper aims is to conduct simulation using pulse echo technique to examine the relationship between fast and slow waves with porosity of 2-dimensional cancellous bone models by comparing the result to through transmission technique. The “incident” and “reflected” waves were separated using bandlimited deconvolution method by estimating time threshold of fast and slow waves' transfer function. The parameters of the waves were computed, plotted versus porosity for six different thicknesses and the correlation coefficients between them were compared. The incident and reflected fast wave attenuations show marginally significant correlation with porosity for both bone models orientations. Wave propagation for parallel orientation dominated by incident and reflected fast wave, meanwhile, perpendicular orientation dominated by incident slow wave. The thickness factor affected wave amplitude but less affected the attenuation. Because of propagation loss, reflected wave shows lower correlation to porosity compared to incident wave. Hence, analyzing fast and slow waves might improve the measurement accuracy of pulse echo technique compared to using single mode wave to estimate bone quality

Experiment and simulation of reflected slow and fast wave correlation with cancellous bone models

Incorporating fast and slow wave analysis into ultrasound measurements can improve the accuracy of bone quality estimation to detect the risk of osteoporosis-related fractures. Since the pulse-echo technique can perform measurements at critical bone locations, this technique is offered by applying fast and slow wave analysis to improve the accuracy of the measurement technique. Thus, the objective of this paper is to conduct simulation and experiment for the pulse-echo technique to investigate correlation reflected fast and slow wave with various porosity of cancellous bone models. The recorded reflected wave (mix wave) is separated method into individual reflected fast and slow wave using bandlimited deconvolution. Further, the parameters for the mix, fast and slow waves are calculated, plotted against porosity and correlation of the parameter's data is observed. The result between simulation and experiment also compared in terms of parameters behaviour versus porosity. The result shows that the reflected fast and slow wave separated using bandlimited deconvolution method has characteristics that represent wave that propagate through solid or pore part of the porous structure as found by previous works. Moreover, the simulation result shows that the parameter of reflected fast and slow wave shows a high correlation with porosity. However, for experiment, only attenuation parameters shows significant correlation with porosity ({\mathrm{R}^{2}}_{\text{fast}}=0.51 and {\mathrm{R}^{2}}_{\text{slow}}=-0.76). The experiment may experience additional undesired noise in comparison with the simulation. Nevertheless, the attenuation parameters were consistent between the simulation and the experiment. The overall result shows that studying fast and slow waves instead of mix waves for bone quality estimation can help improve the accuracy of pulse-echo measurement

Active thermography for the investigation of corrosion in steel surfaces

The present work aims at developing an experimental methodology for the analysis of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in reflexion configuration (RC). The peculiarity of this AT approach consists in exciting by means of a laser source the sound surface of the specimens and acquiring the thermal signal on the same surface, instead of the corroded one: the thermal signal is then composed by the reflection of the thermal wave reflected by the corroded surface. This procedure aims at investigating internal corroded surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to improve the experimental set up. Surface thermal profiles were acquired by an IR thermocamera and means of salt spray testing; at set time intervals the specimens were investigated by means of AT. Each duration corresponded to a surface damage entity and to a variation in the thermal response. Thermal responses of corroded specimens were related to the corresponding corrosion level, referring to a reference specimen without corrosion. The entity of corrosion was also verified by a metallographic optical microscope to measure the thickness variation of the specimens