Bone surface topology mapping and its role in trabecular bone quality assessment using scanning confocal ultrasound

Oon

Biomech Model Mechanobiol

et al. 2014

The microarchitecture and alignment of trabecular bone adapts to the particular mechanical milieu applied to it. Due to this anisotropic mechanical property, measurement orientation has to be taken into consideration when assessing trabecular bone quality and fracture risk prediction. Quantitative ultrasound (QUS) has demonstrated the ability in predicting the principal structural orientation (PSO) of trabecular bone. Although the QUS prediction for PSO is very close to that of μCT, certain angle differences still exist. It remains unknown whether this angle difference can induce significant differences in mechanical properties or not. The objective of this study is to evaluate the mechanical properties in different PSOs predicted using different methods, QUS and μCT, thus to investigate the ability of QUS as a means to predict the PSO of trabecular bone noninvasively. By validating the ability of QUS to predict the PSO of trabecular bone, it is beneficial for future QUS applications because QUS measurements in the PSO can provide information more correlated with the mechanical properties than with other orientations. In this study, seven trabecular bone balls from distal bovine femurs were used to generate finite element models based on the 3-dimensional μCT images. Uniaxial compressive loading was performed on the bone ball models in the finite element analysis (FEA) in 6 different orientations (three anatomical orientations, two PSOs predicted by QUS and the longest vector of mean intercept length (MIL) tensor calculated by μCT). The stiffness was calculated based on the reaction force of the bone balls under loading and the von Mises stress results showed that both the mechanical properties in the PSOs predicted by QUS is significantly higher than the anatomical orientations and comparatively close to the longest vector of MIL tensor. The stiffness in the PSOs predicted by QUS is also highly correlated with the stiffness in the MIL tensor orientation (ATTmax vs. MIL, R2=0.98, p<001; UVmax vs. MIL, R2=0.92, p<001). These results were validated by in vitro mechanical testing on the bone ball samples. This study demonstrates that the PSO of trabecular bone predicted by QUS has an equally strong apparent stiffness with the orientation predicted by μCT.

Section: Methodsmentioning

confidence: 99%

Principal trabecular structural orientation predicted by quantitative ultrasound is strongly correlated with $$\upmu $$ μ FEA determined anisotropic apparent stiffness

Oon

Biomech Model Mechanobiol

et al. 2014

“…It has been reported by Xia et al (2007) that a subtle change in sample thickness can cause significant difference in ultrasound velocity calculation, which implied that simply assuming a uniform sample thickness for ultrasound measurement can cause an error that led to inaccurate prediction for bone strength and fracture risk.…”

Section: Discussionmentioning

confidence: 97%

“…Quantitative ultrasound measurements were performed by using a scanning confocal acoustic navigation system (Xia et al, 2007), which consisted of a computer-controlled two-dimensional scanner unit and a pair of focused transducers (V302-SU-F2.00IN, Olympus NDT Inc., Waltham, MA) with a center frequency of 1 MHz. The diameter of the transducers is 25.4 mm and the focal length of the transducers is 50.8 mm.…”

Section: B Quantitative Ultrasound Measurementmentioning

confidence: 99%

“…To progress from an ideal spherical bone model used in the previous work, trabecular bone specimens with more practical cubic geometry are tested. To eliminate the samples thickness difference in different QUS scanning angles, reflection mode QUS as described by Xia et al (2007) is performed to measure the sample thickness in different scanning orientations. The sample thickness measured by reflection mode is combined with the transmission mode QUS scan to evaluate the structural and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Enhanced correlation between quantitative ultrasound and structural and mechanical properties of bone using combined transmission-reflection measurement

The Journal of the Acoustical Society of America

Qin

2015

Quantitative ultrasound (QUS) is capable of predicting the principal structural orientation of trabecular bone; this orientation is highly correlated with the mechanical strength of trabecular bone. Irregular shape of bone, however, would increase variation in such a prediction, especially under human in vivo measurement. This study was designed to combine transmission and reflection modes of QUS measurement to improve the prediction for the structural and mechanical properties of trabecular bone. QUS, mechanical testing, and micro computed tomography (μCT) scanning were performed on 24 trabecular bone cubes harvested from a bovine distal femur to obtain the mechanical and structural parameters. Transmission and reflection modes of QUS measurement in the transverse and frontal planes were performed in a confined 60° angle range with 5° increment. The QUS parameters, attenuation (ATT) and velocity (UV), obtained from transmission mode, were normalized to the specimen thickness acquired from reflection mode. Analysis of covariance showed that the combined transmission-reflection modes improved prediction for the structural and Young's modulus of bone in comparison to the traditional QUS measurement performed only in the medial-lateral orientation. In the transverse plane, significant improvement between QUS and μCT was found in ATT vs bone surface density (BS/BV) (p < 0.05), ATT vs trabecular thickness (Tb.Th) (p < 0.01), ATT vs degree of anisotropy (DA) (p < 0.05), UV vs trabecular bone number (Tb.N) (p < 0.05), and UV vs Tb.Th (p < 0.001). In the frontal plane, significant improvement was found in ATT vs structural model index (SMI) (p < 0.01), ATT vs bone volume fraction (BV/TV) (p < 0.01), ATT vs BS/BV (p < 0.001), ATT vs Tb.Th (p < 0.001), ATT vs DA (p < 0.001), and ATT vs modulus (p < 0.001), UV vs SMI (p < 0.01), UV vs BV/TV (p < 0.05), UV vs BS/BV (p < 0.05), UV vs Tb.Th (p < 0.01), UV vs trabecular spacing (p < 0.05), and UV vs modulus (p < 0.01). These data suggested that the combined transmission-reflection QUS method is capable of providing information more relevant to the structural and mechanical properties of trabecular bone.

The Journal of the Acoustical Society of America

“…This complexity has limited the development and application of ultrasound approaches to assess bone status and osteoporosis when compared to the development and application of DEXA systems. A major limitation associated with current clinical ultrasound systems (Grigorian et al, 2002)-often called ultrasound densitometers-consist of determining bone mass density as DEXA does, without taking advantage of the fact that ultrasound is sensitive to microarchitecture and tissue composition (Sakata et al, 2004;Xia et al, 2007;Mizuno et al, 2008;Sasso et al, 2008;Lin et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Fabric dependence of quasi-waves in anisotropic porous media

Cardoso

Cowin

2011

Assessment of bone loss and osteoporosis by ultrasound systems is based on the speed of sound and broadband ultrasound attenuation of a single wave. However, the existence of a second wave in cancellous bone has been reported and its existence is an unequivocal signature of poroelastic media. To account for the fact that ultrasound is sensitive to microarchitecture as well as bone mineral density (BMD), a fabric-dependent anisotropic poroelastic wave propagation theory was recently developed for pure wave modes propagating along a plane of symmetry in an anisotropic medium. Key to this development was the inclusion of the fabric tensor-a quantitative stereological measure of the degree of structural anisotropy of bone-into the linear poroelasticity theory. In the present study, this framework is extended to the propagation of mixed wave modes along an arbitrary direction in anisotropic porous media called quasi-waves. It was found that differences between phase and group velocities are due to the anisotropy of the bone microarchitecture, and that the experimental wave velocities are more accurately predicted by the poroelastic model when the fabric tensor variable is taken into account. This poroelastic wave propagation theory represents an alternative for bone quality assessment beyond BMD.