@article{white_yousefian_banks_alexanderian_mueller_2021, title={Inferring pore radius and density from ultrasonic attenuation using physics-based modeling}, volume={149}, ISSN={["1520-8524"]}, DOI={10.1121/10.0003213}, abstractNote={This work proposes the use of two physics-based models for wave attenuation to infer the microstructure of cortical bone-like structures. One model for ultrasound attenuation in porous media is based on the independent scattering approximation (ISA) and the other model is based on the Waterman Truell (WT) approximation. The microstructural parameters of interest are pore radius and pore density. Attenuation data are simulated for three-dimensional structures mimicking cortical bone using the finite-difference time domain package SimSonic. These simulated structures have fixed sized pores (monodisperse), allowing fine-tuned control of the microstructural parameters. Structures with pore radii ranging from 50 to 100  μm and densities ranging from 20 to 50 pores/mm3 are generated in which only the attenuation due to scattering is considered. From here, an inverse problem is formulated and solved, calibrating the models to the simulated data and producing estimates of pore radius and density. The estimated microstructural parameters closely match the values used to simulate the data, validating the use of both the ISA and WT approximations to model ultrasonic wave attenuation in heterogeneous structures mimicking cortical bone. Furthermore, this illustrates the effectiveness of both models in inferring pore radius and density solely from ultrasonic attenuation data.}, number={1}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={White, R. D. and Yousefian, O. and Banks, H. T. and Alexanderian, A. and Mueller, M.}, year={2021}, month={Jan}, pages={340–347} }
 @article{du_yousefian_horn_muller_2020, title={Evaluation of Structural Anisotropy in a Porous Titanium Medium Mimicking Trabecular Bone Structure Using Mode-Converted Ultrasonic Scattering}, volume={67}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2019.2963162}, abstractNote={The mode-converted (longitudinal to transverse, L-T) ultrasonic scattering method was utilized to characterize the structural anisotropy of a phantom mimicking the structural properties of trabecular bone. The sample was fabricated using metal additive manufacturing from high-resolution computed tomography (CT) images of a sample of trabecular horse bone with strong anisotropy. Two focused transducers were used to perform the L-T ultrasonic measurements. A normal incidence transducer was used to transmit longitudinal ultrasonic waves into the sample, while the scattered transverse signals were received by an oblique incidence transducer. At multiple locations on the sample, four L-T measurements were performed by collecting ultrasonic scattering from four directions. The amplitude of the root mean square (rms) of the collected ultrasonic scattering signals was calculated for each L-T measurement. The ratios of rms amplitudes for L-T measurements in different directions were calculated to characterize the anisotropy of sample. The results show that the amplitude of L-T converted scattering is highly dependent on the direction of microstructural anisotropy. A strong anisotropy of the microstructure was observed, which coincides with simulation results previously published on the same structure as well as with the anisotropy estimated from the CT images. These results suggest the potential of mode-converted ultrasonic scattering methods to assess the anisotropy of materials with porous, complex structures, including trabecular bone.}, number={5}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Du, Hualong and Yousefian, Omid and Horn, Timothy and Muller, Marie}, year={2020}, month={May}, pages={1017–1024} }
 @article{yousefian_karbalaeisadegh_mueller_2021, title={Frequency-dependent analysis of ultrasound apparent absorption coefficient in multiple scattering porous media: application to cortical bone}, volume={66}, ISSN={["1361-6560"]}, DOI={10.1088/1361-6560/abb934}, abstractNote={Abstract
               The effect of matrix viscoelastic absorption on frequency-dependent attenuation in porous structures mimicking simplified cortical bone is addressed in this numerical study. An apparent absorption is defined to quantify the difference between total attenuation (resulting from both absorption and scattering) and attenuation exclusively due to scattering. A power-law model is then used to describe the frequency-dependent apparent absorption as a function of pore diameter and density. The frequency response of the porous structures to a Gaussian pulse is studied to determine the frequency range over which the system can be considered linear. The results show that for low scattering regimes (normalized frequency 
                     
                     
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                  0.80), the system and its apparent absorption can be considered linear. Hence, the total attenuation coefficient results from the summation of scattering and absorption coefficients. However, for highly scattering regimes, the system can no longer be considered linear, as the apparent absorption vs. frequency deviates from a linear trend. As the pore density increases, the apparent absorption coefficient increases as well.}, number={3}, journal={PHYSICS IN MEDICINE AND BIOLOGY}, author={Yousefian, Omid and Karbalaeisadegh, Yasamin and Mueller, Marie}, year={2021}, month={Feb} }
 @article{karbalaeisadegh_yousefian_iori_raum_muller_2019, title={Acoustic diffusion constant of cortical bone: Numerical simulation study of the effect of pore size and pore density on multiple scattering}, volume={146}, ISSN={["1520-8524"]}, DOI={10.1121/1.5121010}, abstractNote={While osteoporosis assessment has long focused on the characterization of trabecular bone, the cortical bone micro-structure also provides relevant information on bone strength. This numerical study takes advantage of ultrasound multiple scattering in cortical bone to investigate the effect of pore size and pore density on the acoustic diffusion constant. Finite-difference time-domain simulations were conducted in cortical microstructures that were derived from acoustic microscopy images of human proximal femur cross sections and modified by controlling the density (Ct.Po.Dn) ∈[5−25] pore/mm2 and size (Ct.Po.Dm) ∈[30−100] μm of the pores. Gaussian pulses were transmitted through the medium and the backscattered signals were recorded to obtain the backscattered intensity. The incoherent contribution of the backscattered intensity was extracted to give access to the diffusion constant D. At 8 MHz, significant differences in the diffusion constant were observed in media with different porous micro-architectures. The diffusion constant was monotonously influenced by either pore diameter or pore density. An increase in pore size and pore density resulted in a decrease in the diffusion constant (D =285.9Ct.Po.Dm−1.49, R2=0.989 , p=4.96×10−5,RMSE=0.06; D=6.91Ct.Po.Dn−1.01, R2=0.94, p=2.8×10−3 , RMSE=0.09), suggesting the potential of the proposed technique for the characterization of the cortical microarchitecture.}, number={2}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Karbalaeisadegh, Yasamin and Yousefian, Omid and Iori, Gianluca and Raum, Kay and Muller, Marie}, year={2019}, month={Aug}, pages={1015–1023} }
 @article{mohanty_yousefian_karbalaeisadegh_ulrich_grimal_muller_2019, title={Artificial neural network to estimate micro-architectural properties of cortical bone using ultrasonic attenuation: A 2-D numerical study}, volume={114}, ISBN={1879-0534}, DOI={10.1016/j.compbiomed.2019.103457}, abstractNote={The goal of this study is to estimate micro-architectural parameters of cortical porosity such as pore diameter (φ), pore density (ρ) and porosity (ν) of cortical bone from ultrasound frequency dependent attenuation using an artificial neural network (ANN). First, heterogeneous structures with controlled pore diameters and pore densities (mono-disperse) were generated, to mimic simplified structure of cortical bone. Then, more realistic structures were obtained from high resolution CT scans of human cortical bone. 2-D finite-difference time-domain simulations were conducted to calculate the frequency-dependent attenuation in the 1–8 MHz range. An ANN was then trained with the ultrasonic attenuation at different frequencies as the input feature vectors while the output was set as the micro-architectural parameters (pore diameter, pore density and porosity). The ANN is composed of three fully connected dense layers with 24, 12 and 6 neurons, connected to the output layer. The dataset was trained over 6000 epochs with a batch size of 16. The trained ANN exhibits the ability to predict the micro-architectural parameters with high accuracy and low losses. ANN approaches could potentially be used as a tool to help inform physics-based modelling of ultrasound propagation in complex media such as cortical bone. This will lead to the solution of inverse-problems to retrieve bone micro-architectural parameters from ultrasound measurements for the non-invasive diagnosis and monitoring osteoporosis.}, journal={COMPUTERS IN BIOLOGY AND MEDICINE}, author={Mohanty, Kaustav and Yousefian, Omid and Karbalaeisadegh, Yasamin and Ulrich, Micah and Grimal, Quentin and Muller, Marie}, year={2019}, month={Nov} }
 @article{yousefian_karbalaeisadegh_muller_2019, title={Modeling ultrasound attenuation in porous structures with mono-disperse random pore distributions using the independent scattering approximation: a 2D simulation study}, volume={64}, ISSN={["1361-6560"]}, DOI={10.1088/1361-6560/ab2a32}, abstractNote={The validity of the independent scattering approximation (ISA) to predict the frequency dependent attenuation in 2D models of simplified structures of cortical bone is studied. Attenuation of plane waves at central frequencies ranging from 1 to 8 MHz propagating in structures with mono-disperse random pore distributions with pore diameter and pore density in the range of those of cortical bone are evaluated by finite difference time domain numerical simulations. An approach to assess the multiple scattering of waves in random media is discussed to determine the pore diameter ranges at which the ISA is applicable. A modified version of the ISA is proposed to more accurately predict the attenuation in porosity ranges where it would traditionally fail. The results show that the modified ISA can model the frequency-dependent attenuation of ultrasonic wave with pore diameter and density ranges comparable to those of cortical bone.}, number={15}, journal={PHYSICS IN MEDICINE AND BIOLOGY}, author={Yousefian, Omid and Karbalaeisadegh, Yasamin and Muller, Marie}, year={2019}, month={Aug} }
 @article{mohanty_yousefian_karbalaeisadegh_ulrich_muller_2019, title={Predicting Structural Properties of Cortical Bone by Combining Ultrasonic Attenuation and an Artificial Neural Network (ANN): 2-D FDTD Study}, volume={11662}, ISBN={["978-3-030-27201-2"]}, ISSN={["1611-3349"]}, DOI={10.1007/978-3-030-27202-9_37}, abstractNote={The goal of this paper is to predict the micro-architectural parameters of cortical bone such as pore diameter (ϕ) and porosity (ν) from ultrasound attenuation measurements using an artificial neural network (ANN). Slices from a 3-D CT scan of human femur are obtained. The micro-architectural parameters of porosity such as average pore size and porosity are calculated using image processing. When ultrasound waves propagate in porous structures, attenuation is observed due to scattering. Two-dimensional finite-difference time-domain simulations are carried out to obtain frequency dependent attenuation in those 2D structures. An artificial neural network (ANN) is then trained with the input feature vector as the frequency dependent attenuation and output as pore diameter (ϕ) and porosity (ν). The ANN is composed of one input layer, 3 hidden layers and one output layer, all of which are fully connected. 340 attenuation data sets were acquired and trained over 2000 epochs with a batch size of 32. Data was split into train, validation and test. It was observed that the ANN predicted the micro-architectural parameters of the cortical bone with high accuracies and low losses with a minimum R2 (goodness of fit) value of 0.95. ANN approaches could potentially help inform the solution of inverse-problems to retrieve bone porosity from ultrasound measurements. Ultimately, those inverse-problems could be used for the non-invasive diagnosis and monitoring of osteoporosis.}, journal={IMAGE ANALYSIS AND RECOGNITION, ICIAR 2019, PT I}, author={Mohanty, Kaustav and Yousefian, Omid and Karbalaeisadegh, Yasamin and Ulrich, Micah and Muller, Marie}, year={2019}, pages={407–417} }
 @article{yousefian_balabokhin_tarbutton_2020, title={Point-by-point prediction of cutting force in 3-axis CNC milling machines through voxel framework in digital manufacturing}, volume={31}, ISSN={["1572-8145"]}, DOI={10.1007/s10845-018-1442-7}, number={1}, journal={JOURNAL OF INTELLIGENT MANUFACTURING}, author={Yousefian, Omid and Balabokhin, Andrey and Tarbutton, Joshua}, year={2020}, month={Jan}, pages={215–226} }
 @article{yousefian_white_karbalaeisadegh_banks_muller_2018, title={The effect of pore size and density on ultrasonic attenuation in porous structures with mono-disperse random pore distribution: A two-dimensional in-silico study}, volume={144}, ISSN={["1520-8524"]}, DOI={10.1121/1.5049782}, abstractNote={This work proposes a power law model to describe the attenuation of ultrasonic waves in non-absorbing heterogeneous media with randomly distributed scatterers, mimicking a simplified structure of cortical bone. This paper models the propagation in heterogeneous structures with controlled porosity using a two-dimensional finite-difference time domain numerical simulation in order to measure the frequency dependent attenuation. The paper then fits a phenomenological model to the simulated frequency dependent attenuation by optimizing parameters under an ordinary least squares framework. Local sensitivity analysis is then performed on the resulting parameter estimates in order to determine to which estimates the model is most sensitive. This paper finds that the sensitivity of the model to various parameter estimates depends on the micro-architectural parameters, pore diameter (ϕ) and pore density (ρ). In order to get a sense for how confidently model parameters are able to be estimated, 95% confidence intervals for these estimates are calculated. In doing so, the ability to estimate model-sensitive parameters with a high degree of confidence is established. In the future, being able to accurately estimate model parameters from which micro-architectural ones could be inferred will allow pore density and diameter to be estimated via an inverse problem given real or simulated ultrasonic data to be determined.}, number={2}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Yousefian, Omid and White, R. D. and Karbalaeisadegh, Yasamin and Banks, H. T. and Muller, Marie}, year={2018}, month={Aug}, pages={709–719} }