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Estimation of layer thickness by the cost function optimization: phantom study

Tasinkiewicz J., Podhajecki J., Wojcik J., Falińska K., Litniewski J.

Hydroacoustics

2015

Vol. 18

161-166

The aim of this work is to present preliminary results of the layer thickness assessment method based on optimization approach. The developed method is based on a multilayer model structure. The measured acoustic signal reflected from the layer is compared with a simulated signal on the basis of a multilayer model. The cost function is defined as the difference between the reflected signal measured using pulse echo approach and the simulated signal. The thickness of the solid layer is the parameter which minimizes the cost function yielding desired solution. Minimization of the cost function is performed with the simulated annealing algorithm. The results obtained with the developed method using measurement data of a custom design model are compared with the reference value and the accuracy of the method is checked. The relative error of the thickness estimation is 1.44%.

Assesment of cortical bone thickness using cepstrum analysis. Simulation study

Falińska K., Litniewski J., Tasinkiewicz J.

Hydroacoustics

2014

Vol. 17

47--56

Assessment of cortical bone thickness is important from a medical point of view because bone-layer thickness has a diagnostic value. The thinning of the cortical bone layer reduces the mechanical strength of the bone and exposes it to an increased risk of osteoporotic fractures [1]. The hip bone (proximal femur) is the most critical fracture site. The thickness of the cortical layer in the proximal femur is often too thin to be detected from ultrasonic echoes using traditional peak detection methods (for example the envelope method). In such a case the cepstrum analysis technique may be very useful. In this study the cepstrum method was applied to analyze numerically simulated echoes reflected from the layer and to determine layer thickness. In simulation, the transducer operated at 1 MHz and pulses of a 1.5 µs duration were assumed. The thickness of the thinnest layer for which the applied cepstrum analysis gave, the correct result equaled 1 mm, which was ¼ ƛ(ƛ– wavelength of an ultrasonic wave). That value of the d/ƛ ratio is sufficient for future measurements performed in-vivo conditions.