Human Cancellous Bone Samples Research Articles

Correlation between RF signal first-arrival and minimum spectral transit time in cancellous bone

Measurement of the singular ultrasound velocity of a homogeneous sample may be calculated by division of its thickness and propagation transit time, generally utilizing a detection criterion of an RF signal’s first-arrival. A porous composite sample composed of two materials of differing ultrasound velocity will however exhibit a range of transit times. Ultrasound transit time spectroscopy (UTTS) considers propagation of an array of sonic-rays, with minima and maxima values ranging from entire higher and lower velocity materials, respectively. The aim of this Technical Note is to test the hypothesis that conventional RF signal transit time measurement correlates with the minimum spectral transit time, utilizing previously obtained experimental data from human cancellous bone samples. Linear regression yielded a coefficient of determination (R2) of 94%. The authors consider a practical consequence of the hypothesis is that information on the variability of transit time within a heterogeneous test sample may be better assessed by UTTS than conventional RF first-arrival transit time measurement. Noting the fundamental relationships between transit time, velocity, and elasticity of a test sample, there is further potential for UTTS to describe both velocity and elasticity spectroscopies within a wide range of structurally complex composites.

Mechanical Loading Causes Detectable Changes in Morphometric Measures of Trabecular Structure in Human Cancellous Bone

The relationships between mechanical loads and bone microstructure are of interest to those who seek to predict bone mechanical properties from microstructure or to predict how organization of bone microstructure is driven by mechanical loads. While strains and displacements in the material are inherently responsible for mechanically caused changes in the appearance of the microstructure, it is the morphometric measures of microstructural organization that are often available for assessment of bone quality. Therefore, an understanding of how strain history is reflected in morphometric measures of bone microstructure has practical implications in that it may provide clinically measurable indices of mechanical history in bone and improve interpretation of bone mechanical properties from microstructural information. The objective of the current study was to examine changes in morphometric measures of cancellous bone microstructure in response to varying levels of continuum level strains. The experimental approach included stereologic analysis of microcomputed tomography (μCT) images of human cancellous bone samples obtained at sequentially increasing levels of strain in a custom-made loading apparatus mounted in a μCT scanner. We found that the degree of anisotropy (DA) decreased from baseline to failure and from failure to postfailure. DA partially recovered from postfailure levels upon unloading; however, the final DA was less than at failure and less than at baseline. We also found that average trabecular thickness (Tb.Th.Av) increased with displacements at postfailure and did not recover when unloaded. Average trabecular number decreased when the specimens were unloaded. In addition, the heterogeneity of Tb.Th as measured by intra-specimen standard deviation (Tb.Th.SD) increased and that of trabecular number (Tb.N.SD) decreased with displacements at postfailure. Furthermore, the intraspecimen coefficient of variation of trabecular number decreased at postfailure displacements but did not recover upon unloading. Finally, the coefficient of variation of trabecular separation at unload was less than that at baseline. These measures can be developed into image-based indices to estimate strain history, damage, and residual mechanical properties where direct analysis of stresses and strains, such as through finite element modeling, may not be feasible. It remains to be determined how wide a time interval can be used to estimate strain history before remodeling becomes an overriding effect on the trabecular architecture.

Transient ultrasound propagation in porous media using Biot theory and fractional calculus: Application to human cancellous bone

A temporal model based on the Biot theory is developed to describe the transient ultrasonic propagation in porous media with elastic structure, in which the viscous exchange between fluid and structure are described by fractional derivatives. The fast and slow waves obey a fractional wave equation in the time domain. The solution of Biot's equations in time depends on the Green functions of each of the waves (fast and slow), and their fractional derivatives. The reflection and transmission operators for a slab of porous materials are derived in the time domain, using calculations in the Laplace domain. Their analytical expressions, depend on Green's function of fast and slow waves. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Application of the Biot model to ultrasound in bone: Direct problem

Ultrasonic wave propagation in human cancellous bone is considered using Biot's theory modified by the Johnson-Koplik-Dashen model for viscous exchange between fluid and structure. The transmission coefficient is derived for a slab of porous material. Experimental results for fast and slow waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Application of the Biot model to ultrasound in bone: Inverse problem

This paper concerns the ultrasonic characterization of human cancellous bone samples by solving the inverse problem using experimentally measured signals. The inverse problem is solved numerically by the least squares method. Five parameters are inverted: porosity, tortuosity, viscous characteristic length, Young modulus, and Poisson ratio of the skeletal frame. The minimization of the discrepancy between experiment and theory is made in the time domain. The ultrasonic propagation in cancellous bone is modelled using the Biot theory modified by the Johnson-Koplik-Dashen model for viscous exchange between fluid and structure. The sensitivity of the Young modulus and the Poisson ratio of the skeletal frame is studied showing their effect on the fast and slow waveforms. The inverse problem is shown to be well posed, and its solution to be unique. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

The role of bone marrow on acoustic properties of cancellous bone ‐ finite difference time domain modelling study

Quantitative ultrasound (US) parameters are related to structure and properties of cancellous bone. The effect of bone marrow on US propagation, i.e. absorption and scattering, is still poorly understood. However, substitution of fatty marrow with water is known to significantly affect the US parameters. The present study investigates the role of marrow on US parameters, using microtomography based 3D‐finite difference time domain (FDTD) modelling. Eleven human cancellous bone samples were analysed with a micro‐CT system (SkyScan 1072) to determine microstructure and morphology. Wave 3000 Pro software (Cyberlogic Inc.) was used for simulations. Models were created to simulate experimental US measurement geometry with focused 1MHz transducers. Simulations were repeated before and after replacing the marrow with water. The voxel size of the simulation mesh significantly affected sample structure and simulations. US attenuation and speed decreased and increased, respectively, when marrow was replaced with water (p<0.01). US reflection at sample surface and backscattering from internal structures increased (p<0.01) when marrow was replaced with water. Contribution of bone marrow was stronger in samples with low bone volume fraction. This implicates that inter‐individual differences in the composition of marrow may significantly affect measured ultrasound parameters, especially when investigating osteoporotic bone with low density.

Ultrasonic characterization of human cancellous bone using the Biot theory: Inverse problem

This paper concerns the ultrasonic characterization of human cancellous bone samples by solving the inverse problem using experimental transmitted signals. The ultrasonic propagation in cancellous bone is modeled using the Biot theory modified by the Johnson et al. model for viscous exchange between fluid and structure. The sensitivity of the Young modulus and the Poisson ratio of the skeletal frame is studied showing their effect on the fast and slow wave forms. The inverse problem is solved numerically by the least squares method. Five parameters are inverted: the porosity, tortuosity, viscous characteristic length, Young modulus, and Poisson ratio of the skeletal frame. The minimization of the discrepancy between experiment and theory is made in the time domain. The inverse problem is shown to be well posed, and its solution to be unique. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Application of fractional calculus to ultrasonic wave propagation in human cancellous bone

Ultrasonic wave propagation in human cancellous bone is considered. Fractional calculus is used to describe the viscous interactions between fluid and solid structure. Reflection and transmission scattering operators are derived for a slab of cancellous bone in the elastic frame using Biot's theory. Experimental results are compared with theoretical predictions for slow and fast waves transmitted through human cancellous bone samples.

Ultrasonic wave propagation in human cancellous bone: Application of Biot theory

Ultrasonic wave propagation in human cancellous bone is considered. Reflection and transmission coefficients are derived for a slab of cancellous bone having an elastic frame using Biot’s theory modified by the Johnson et al. model for viscous exchange between fluid and structure. Numerical simulations of transmitted waves in the time domain are worked out by varying the modified Biot parameters. The sensitivity of each physical parameter used in the theory has been studied in transmission. Some parameters play an important role in slow wave waveform, such as the viscous characteristic length and pore fluid bulk modulus. However, other parameters play an important role in the fast wave waveform, such as solid density and shear modulus. We also note from these simulations that some parameters, such as porosity, tortuosity, thickness, solid bulk modulus and skeletal compressibility frame, play an important role simultaneously in both fast and slow waveforms compared to other parameters which act on the waveform of just one of the two waves. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Ultrasonic wave propagation in human cancellous bone: Application of Biot theory

Ultrasonic wave propagation in human cancellous bone is considered. Reflection and transmission coefficients are derived for a slab of cancellous bone having an elastic frame using Biot's theory modified by the model of Johnson et al. [J. Fluid Mech. 176, 379-402 (1987)] for viscous exchange between fluid and structure. Numerical simulations of transmitted waves in the time domain are worked out by varying the modified Biot parameters. The variation is applied to the governing parameters and is about 20%. From this study, we can gain an insight into the sensitivity of each physical parameter used in this theory. Some parameters play an important role in slow-wave wave form, such as the viscous characteristic length lambda and pore fluid bulk modulus Kf. However, other parameters play an important role in the fast-wave wave form, such as solid density rhos and shear modulus N. We also note from these simulations that some parameters such as porosity phi, tortuosity alpha(infinty), thickness, solid bulk modulus Ks, and skeletal compressibility frame Kb, play an important role simultaneously in both fast and slow wave forms compared to other parameters which act on the wave form of just one of the two waves. The sensitivity of the modified Biot parameters with respect to the transmitted wave depends strongly on the coupling between the solid and fluid phases of the cancellous bone. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Expression of smooth muscle actin in osteoblasts in human bone

It is well known that certain connective tissue cells (viz., dermal fibroblasts) can express the gene for a muscle actin – α-smooth muscle actin – and can contract. This process contributes to skin wound closure and is responsible for Dupuytren's contracture. The objective of this study was to determine if human osteoblasts can also express the gene for α-smooth muscle actin. Immunohistochemistry using a monoclonal antibody for α-smooth muscle actin was performed on human cancellous bone samples obtained from 20 individuals at the time of total joint arthroplasty. The percentages of resting and active osteoblasts on the bone surfaces containing this muscle actin isoform were evaluated. Explants of human bone were also studied for the expression of α-smooth muscle actin in the tissue and in the outgrowing cells with time in culture. Western blot analysis was performed to quantify the α-smooth muscle actin content of the outgrowing cells relative to smooth muscle cell controls. Nine ± 2% (mean ± SEM; n=20) of the cells classified as inactive osteoblasts and 69±3% ( n=19) of the cells identified as active osteoblasts on the bone surface contained α-smooth muscle actin. This difference was highly statistically significant (Student's t test, p<0.0001). Similar profiles of α-smooth muscle actin-expressing cells were found in explants cultured for up to 12 weeks. Cells forming a layer on the surface of the explants and growing out from them in monolayer also contained α-smooth muscle actin by immunohistochemistry and Western blot analysis. Human osteoblasts can express the gene for α-smooth muscle actin. This expression should be considered a phenotypic characteristic of this cell type, conferred by its progenitor cells: bone marrow stromal-derived stem cells, and perhaps pericytes and smooth muscle cells.

Ultrasonic assessement of physical properties of osteoporotic bones

Ultrasonic measurements in human cancellous hone were carried out in vivo and in samples. The pulse transmission method (I MHz) and Fourier analysis of transmitted pulses in the frequency range of 0.25–0.70 MHz was applied.Broadband ultrasound attenuation (BUA) in the calcaneus in vivo was measured in 109 healthy female volunteers in the age of 17–85 years and 44 women with a history of osteoporotic fractures, in the age of 40–89 years. The decrease of BUA in the calcaneus in vivo in healthy women begins at the fourth decade of life. In osteoporotic women mean BUA was 59.9 dB/MHz (S.D. = 8.8 dB/MHz). In the healthy group above 40 years old, mean BUA was 76.6 dB/MHz (S.D. = 10.3 (113/MHz). Precision estimated from 12 repeated measurements in six women was in the range between 1.9 % and 4.1 %.Attenuation (BUA) and velocity of ultrasound was measured in human cancellous bone samples from lumbar vertebra and calcaneus. The porosity of samples was in the range of 50 %–90 %. The negative correlation between porosity and ultrasound velocity (r = 0.92, p < 0.001) and porosity and broadband ultrasound attenuation (r = 0.89; p < 0.001) was found. In lumbar vertebrae anisotropy of ultrasound velocity and an increase of anisotropy in more porous samples was stated.

The enkephalinergic osteoblast.

The enkephalinergic osteoblast.