1
|
Gonzalez EA, Bell MAL. Photoacoustic Imaging and Characterization of Bone in Medicine: Overview, Applications, and Outlook. Annu Rev Biomed Eng 2023; 25:207-232. [PMID: 37000966 DOI: 10.1146/annurev-bioeng-081622-025405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Photoacoustic techniques have shown promise in identifying molecular changes in bone tissue and visualizing tissue microstructure. This capability represents significant advantages over gold standards (i.e., dual-energy X-ray absorptiometry) for bone evaluation without requiring ionizing radiation. Instead, photoacoustic imaging uses light to penetrate through bone, followed by acoustic pressure generation, resulting in highly sensitive optical absorption contrast in deep biological tissues. This review covers multiple bone-related photoacoustic imaging contributions to clinical applications, spanning bone cancer, joint pathologies, spinal disorders, osteoporosis, bone-related surgical guidance, consolidation monitoring, and transsphenoidal and transcranial imaging. We also present a summary of photoacoustic-based techniques for characterizing biomechanical properties of bone, including temperature, guided waves, spectral parameters, and spectroscopy. We conclude with a future outlook based on the current state of technological developments, recent achievements, and possible new directions.
Collapse
Affiliation(s)
- Eduardo A Gonzalez
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Muyinatu A Lediju Bell
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Electrical and Computer Engineering and Department of Computer Science, Johns Hopkins University, Baltimore, Maryland, USA;
| |
Collapse
|
2
|
Wear KA, Han A, Rubin JM, Gao J, Lavarello R, Cloutier G, Bamber J, Tuthill T. US Backscatter for Liver Fat Quantification: An AIUM-RSNA QIBA Pulse-Echo Quantitative Ultrasound Initiative. Radiology 2022; 305:526-537. [PMID: 36255312 DOI: 10.1148/radiol.220606] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is believed to affect one-third of American adults. Noninvasive methods that enable detection and monitoring of NAFLD have the potential for great public health benefits. Because of its low cost, portability, and noninvasiveness, US is an attractive alternative to both biopsy and MRI in the assessment of liver steatosis. NAFLD is qualitatively associated with enhanced B-mode US echogenicity, but visual measures of B-mode echogenicity are negatively affected by interobserver variability. Alternatively, quantitative backscatter parameters, including the hepatorenal index and backscatter coefficient, are being investigated with the goal of improving US-based characterization of NAFLD. The American Institute of Ultrasound in Medicine and Radiological Society of North America Quantitative Imaging Biomarkers Alliance are working to standardize US acquisition protocols and data analysis methods to improve the diagnostic performance of the backscatter coefficient in liver fat assessment. This review article explains the science and clinical evidence underlying backscatter for liver fat assessment. Recommendations for data collection are discussed, with the aim of minimizing potential confounding effects associated with technical and biologic variables.
Collapse
Affiliation(s)
- Keith A Wear
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Aiguo Han
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Jonathan M Rubin
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Jing Gao
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Roberto Lavarello
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Guy Cloutier
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Jeffrey Bamber
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| | - Theresa Tuthill
- From the Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, WO62, Room 2114, Silver Spring, MD 20993 (K.A.W.); Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Ill (A.H.); Department of Radiology, University of Michigan, Ann Arbor, Mich (J.M.R.); Ultrasound Research and Education, Rocky Vista University, Ivins, Utah (J.G.); Department of Engineering, Pontificia Universidad Católica del Perú, Lima, Peru (R.L.); Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, Canada (G.C.); Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Division of Radiotherapy and Imaging, Joint Department of Physics, London, UK (J.B.); and Pfizer, Cambridge, Mass (T.T.)
| |
Collapse
|
3
|
Viano AM, Ankersen JP, Hoffmeister BK, Huang J, Fairbanks LC. Ultrasonic Bone Assessment: Ability of Apparent Backscatter Techniques to Detect Changes in the Microstructure of Human Cancellous Bone. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:3309-3325. [PMID: 34138705 DOI: 10.1109/tuffc.2021.3090359] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ultrasonic backscatter techniques may offer a useful approach for detecting changes in bone caused by osteoporosis. The goal of this study was to investigate how bone mineral density (BMD) and the microstructure of human cancellous bone affect three ultrasonic backscatter parameters that have been identified as potentially useful for ultrasonic bone assessment purposes: the apparent integrated backscatter (AIB), the frequency slope of apparent backscatter (FSAB), and the frequency intercept of apparent backscatter (FIAB). Ultrasonic measurements were performed with a 3.5-MHz broadband transducer on 54 specimens of human cancellous bone prepared from the proximal femur. Microstructural parameters and BMD were measured using X-ray microcomputed tomography (micro-CT). Relationships between AIB, FSAB, FIAB, and the micro-CT parameters were investigated using univariate and multivariate statistical analysis techniques. Moderate-to-strong univariate correlations were observed between the backscatter parameters and microstructure and BMD in many cases. The partial correlation analysis indicated that the backscatter parameters are dependent on microstructure independently of BMD in some cases. Multiple stepwise linear regression analysis used to generate multivariate models found that microstructure was a significant predictor of the backscatter parameters in most cases.
Collapse
|
4
|
Hoffmeister BK, Gray AJ, Sharp PC, Fairbanks LC, Huang J. Ultrasonic Bone Assessment Using the Backscatter Amplitude Decay Constant. ULTRASOUND IN MEDICINE & BIOLOGY 2020; 46:2412-2423. [PMID: 32553693 DOI: 10.1016/j.ultrasmedbio.2020.04.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 03/29/2020] [Accepted: 04/26/2020] [Indexed: 06/11/2023]
Abstract
Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. The present study introduces a new technique that measures the exponential decay in the amplitude of the backscatter signal quantified by a parameter called the backscatter amplitude decay constant (BADC). Measurements were performed on 54 specimens of cancellous bone from 14 human femurs using a 3.5-MHz transducer. Six methods were tested to determine BADC. The recommended method measures the time slope of the natural log of the rectified signal. Measured values of BADC ranged from approximately 0.1 μs-1 to 0.6 μs-1. Moderate to strong correlations (Spearman's ρ >0.7) were found between BADC and the density and microstructural characteristics of the specimens determined using X-ray microcomputed tomography. The results of this study suggest that BADC may be able to detect changes in the density and microstructure of cancellous bone caused by osteoporosis and other diseases.
Collapse
Affiliation(s)
| | - Aubrey J Gray
- Department of Physics, Rhodes College, Memphis, Tennessee, USA
| | - Phoebe C Sharp
- Department of Physics, Rhodes College, Memphis, Tennessee, USA
| | | | - Jinsong Huang
- University of Tennessee Health Science Center, Memphis, Tennessee, USA
| |
Collapse
|
5
|
Wear KA. Mechanisms of Interaction of Ultrasound With Cancellous Bone: A Review. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:454-482. [PMID: 31634127 PMCID: PMC7050438 DOI: 10.1109/tuffc.2019.2947755] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Ultrasound is now a clinically accepted modality in the management of osteoporosis. The most common commercial clinical devices assess fracture risk from measurements of attenuation and sound speed in cancellous bone. This review discusses fundamental mechanisms underlying the interaction between ultrasound and cancellous bone. Because of its two-phase structure (mineralized trabecular network embedded in soft tissue-marrow), its anisotropy, and its inhomogeneity, cancellous bone is more difficult to characterize than most soft tissues. Experimental data for the dependencies of attenuation, sound speed, dispersion, and scattering on ultrasound frequency, bone mineral density, composition, microstructure, and mechanical properties are presented. The relative roles of absorption, scattering, and phase cancellation in determining attenuation measurements in vitro and in vivo are delineated. Common speed of sound metrics, which entail measurements of transit times of pulse leading edges (to avoid multipath interference), are greatly influenced by attenuation, dispersion, and system properties, including center frequency and bandwidth. However, a theoretical model has been shown to be effective for correction for these confounding factors in vitro and in vivo. Theoretical and phantom models are presented to elucidate why cancellous bone exhibits negative dispersion, unlike soft tissue, which exhibits positive dispersion. Signal processing methods are presented for separating "fast" and "slow" waves (predicted by poroelasticity theory and supported in cancellous bone) even when the two waves overlap in time and frequency domains. Models to explain dependencies of scattering on frequency and mean trabecular thickness are presented and compared with measurements. Anisotropy, the effect of the fluid filler medium (marrow in vivo or water in vitro), phantoms, computational modeling of ultrasound propagation, acoustic microscopy, and nonlinear properties in cancellous bone are also discussed.
Collapse
|
6
|
Lee KI. Correlations of the frequency dependence of the ultrasonic backscatter coefficient with the bone volume fraction and the trabecular thickness in bovine trabecular bone: Application of the binary mixture model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 145:EL393. [PMID: 31153347 DOI: 10.1121/1.5107435] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/24/2019] [Indexed: 06/09/2023]
Abstract
The ultrasonic backscatter coefficient and the exponent n (frequency dependence of the backscatter coefficient) were measured in 24 bovine femoral trabecular bone samples. The binary mixture model for ultrasonic scattering from trabecular bone was applied to predict the variations of the ultrasound parameters with the bone volume fraction (BV/TV) and the trabecular thickness (Tb.Th) in trabecular bone. The backscatter coefficient exhibited significant, positive correlations with the BV/TV (R = 0.82) and the Tb.Th (R = 0.79). In contrast, the exponent n was found to be significantly, negatively correlated with the BV/TV (R = -0.77) and the Tb.Th, (R = -0.71).
Collapse
Affiliation(s)
- Kang Il Lee
- Department of Physics, Kangwon National University, Chuncheon 24341, Republic of
| |
Collapse
|
7
|
Hoffmeister BK, Mcpherson JA, Smathers MR, Spinolo PL, Sellers ME. Ultrasonic backscatter from cancellous bone: the apparent backscatter transfer function. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2015; 62:2115-25. [PMID: 26683412 DOI: 10.1109/tuffc.2015.007299] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused by osteoporosis. Many techniques are based on measurements of the apparent backscatter transfer function (ABTF), which represents the backscattered power from bone corrected for the frequency response of the measurement system. The ABTF is determined from a portion of the backscatter signal selected by an analysis gate of width τw delayed by an amount τd from the start of the signal. The goal of this study was to characterize the ABTF for a wide range of gate delays (1 μs ≤ τd ≤ 6 μs) and gate widths (1 μs ≤ τw ≤ 6 μs). Measurements were performed on 29 specimens of human cancellous bone in the frequency range 1.5 to 6.0 MHz using a broadband 5-MHz transducer. The ABTF was found to be an approximately linear function of frequency for most choices of τd and τw. Changes in τd and τw caused the frequency-averaged ABTF [quantified by apparent integrated backscatter (AIB)] and the frequency dependence of the ABTF [quantified by frequency slope of apparent backscatter (FSAB)] to change by as much as 24.6 dB and 6.7 dB/MHz, respectively. τd strongly influenced the measured values of AIB and FSAB and the correlation of AIB with bone density (-0.95 ≤ R ≤ +0.68). The correlation of FSAB with bone density was influenced less strongly by τd (-0.97 ≤ R ≤ -0.87). τw had a weaker influence than τd on the measured values of AIB and FSAB and the correlation of these parameters with bone density.
Collapse
|
8
|
Hoffmeister BK, Spinolo PL, Sellers ME, Marshall PL, Viano AM, Lee SR. Effect of intervening tissues on ultrasonic backscatter measurements of bone: An in vitro study. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 138:2449-57. [PMID: 26520327 PMCID: PMC4627934 DOI: 10.1121/1.4931906] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 09/07/2015] [Accepted: 09/12/2015] [Indexed: 05/28/2023]
Abstract
Ultrasonic backscatter techniques are being developed to diagnose osteoporosis. Tissues that lie between the transducer and the ultrasonically interrogated region of bone may produce errors in backscatter measurements. The goal of this study is to investigate the effects of intervening tissues on ultrasonic backscatter measurements of bone. Measurements were performed on 24 cube shaped specimens of human cancellous bone using a 5 MHz transducer. Measurements were repeated after adding a 1 mm thick plate of cortical bone to simulate the bone cortex and a 3 cm thick phantom to simulate soft tissue at the hip. Signals were analyzed to determine three apparent backscatter parameters (apparent integrated backscatter, frequency slope of apparent backscatter, and frequency intercept of apparent backscatter) and three backscatter difference parameters [normalized mean backscatter difference (nMBD), normalized slope of the backscatter difference, and normalized intercept of the backscatter difference]. The apparent backscatter parameters were impacted significantly by the presence of intervening tissues. In contrast, the backscatter difference parameters were not affected by intervening tissues. However, only one backscatter difference parameter, nMBD, demonstrated a strong correlation with bone mineral density. Thus, among the six parameters tested, nMBD may be the best choice for in vivo backscatter measurements of bone when intervening tissues are present.
Collapse
Affiliation(s)
| | - P Luke Spinolo
- Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA
| | - Mark E Sellers
- Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA
| | - Peyton L Marshall
- Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA
| | - Ann M Viano
- Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA
| | - Sang-Rok Lee
- Department of Kinesiology and Dance, New Mexico State University, Las Cruces, New Mexico 88003, USA
| |
Collapse
|
9
|
Yang L, Lashkari B, Tan JWY, Mandelis A. Photoacoustic and ultrasound imaging of cancellous bone tissue. JOURNAL OF BIOMEDICAL OPTICS 2015. [PMID: 26222963 DOI: 10.1117/1.jbo.20.7.076016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We used ultrasound (US) and photoacoustic (PA) imaging modalities to characterize cattle trabecular bones. The PA signals were generated with an 805-nm continuous wave laser used for optimally deep optical penetration depth. The detector for both modalities was a 2.25-MHz US transducer with a lateral resolution of ~1 mm at its focal point. Using a lateral pixel size much larger than the size of the trabeculae, raster scanning generated PA images related to the averaged values of the optical and thermoelastic properties, as well as density measurements in the focal volume. US backscatter yielded images related to mechanical properties and density in the focal volume. The depth of interest was selected by time-gating the signals for both modalities. The raster scanned PA and US images were compared with microcomputed tomography (μCT) images averaged over the same volume to generate similar spatial resolution as US and PA. The comparison revealed correlations between PA and US modalities with the mineral volume fraction of the bone tissue. Various features and properties of these modalities such as detectable depth, resolution, and sensitivity are discussed.
Collapse
Affiliation(s)
- Lifeng Yang
- University of Electronic Science and Technology of China, School of Optoelectronic Information, Chengdu 610054, ChinabUniversity of Toronto, Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, Tor
| | - Bahman Lashkari
- University of Toronto, Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, Toronto M5S 3G8, Canada
| | - Joel W Y Tan
- University of Toronto, Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, Toronto M5S 3G8, Canada
| | - Andreas Mandelis
- University of Electronic Science and Technology of China, School of Optoelectronic Information, Chengdu 610054, ChinabUniversity of Toronto, Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, Tor
| |
Collapse
|
10
|
Numerical investigation of ultrasonic attenuation through 2D trabecular bone structures reconstructed from CT scans and random realizations. Comput Biol Med 2013; 45:143-56. [PMID: 24480174 DOI: 10.1016/j.compbiomed.2013.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 11/23/2022]
Abstract
In this paper, we compare ultrasound interrogations of actual CT-scanned images of trabecular bone with artificial randomly constructed bone. Even though it is known that actual bone does not have randomly distributed trabeculae, we find that the ultrasound attenuations are close enough to cast doubt on any microstructural information, such as trabeculae width and distance between trabeculae, being gleaned from such experiments. More precisely, we perform numerical simulations of ultrasound interrogation on cancellous bone to investigate the phenomenon of ultrasound attenuation as a function of excitation frequency and bone porosity. The theoretical model is based on acoustic propagation equations for a composite fluid-solid material and is solved by a staggered-grid finite-difference scheme in the time domain. Numerical experiments are performed on two-dimensional bone samples reconstructed from CT-scanned images of real human calcaneus and from random distributions of fluid-solid particles generated via the turning bands method. A detailed comparison is performed on various parameters such as the attenuation rate and speed of sound through the bone samples as well as the normalized broadband ultrasound attenuation coefficient. Comparing results from these two types of bone samples allows us to assess the role of bone microstructure in ultrasound attenuation. It is found that the random model provides suitable bone samples for ultrasound interrogation in the transverse direction of the trabecular network.
Collapse
|
11
|
Rosado-Mendez IM, Nam K, Hall TJ, Zagzebski JA. Task-oriented comparison of power spectral density estimation methods for quantifying acoustic attenuation in diagnostic ultrasound using a reference phantom method. ULTRASONIC IMAGING 2013; 35:214-34. [PMID: 23858055 PMCID: PMC3879804 DOI: 10.1177/0161734613495524] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Reported here is a phantom-based comparison of methods for determining the power spectral density (PSD) of ultrasound backscattered signals. Those power spectral density values are then used to estimate parameters describing α(f), the frequency dependence of the acoustic attenuation coefficient. Phantoms were scanned with a clinical system equipped with a research interface to obtain radiofrequency echo data. Attenuation, modeled as a power law α(f)= α0 f (β), was estimated using a reference phantom method. The power spectral density was estimated using the short-time Fourier transform (STFT), Welch's periodogram, and Thomson's multitaper technique, and performance was analyzed when limiting the size of the parameter-estimation region. Errors were quantified by the bias and standard deviation of the α0 and β estimates, and by the overall power-law fit error (FE). For parameter estimation regions larger than ~34 pulse lengths (~1 cm for this experiment), an overall power-law FE of 4% was achieved with all spectral estimation methods. With smaller parameter estimation regions as in parametric image formation, the bias and standard deviation of the α0 and β estimates depended on the size of the parameter estimation region. Here, the multitaper method reduced the standard deviation of the α0 and β estimates compared with those using the other techniques. The results provide guidance for choosing methods for estimating the power spectral density in quantitative ultrasound methods.
Collapse
Affiliation(s)
- Ivan M Rosado-Mendez
- Department of Medical Physics, University of Wisconsin, 1111 Highland Ave., Madison, WI 53705, USA.
| | | | | | | |
Collapse
|
12
|
Liu W, Zagzebski JA. Trade-offs in data acquisition and processing parameters for backscatter and scatterer size estimations. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2010; 57:340-52. [PMID: 20178900 PMCID: PMC2853955 DOI: 10.1109/tuffc.2010.1414] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
By analyzing backscattered echo signal power spectra and thereby obtaining backscatter coefficient vs. frequency data, the size of subresolution scatterers contributing to echo signals can be estimated. Here we investigate trade-offs in data acquisition and processing parameters for reference phantom-based backscatter and scatterer size estimations. RF echo data from a tissue-mimicking test phantom were acquired using a clinical scanner equipped with linear array transducers. One array has a nominal frequency bandwidth of 5 to 13 MHz and the other 4 to 9 MHz. Comparison of spectral estimation methods showed that the Welch method provided spectra yielding more accurate and precise backscatter coefficient and scatterer size estimations than spectra computed by applying rectangular, Hanning, or Hamming windows and much reduced computational load than if using the multitaper method. For small echo signal data block sizes, moderate improvements in scatterer size estimations were obtained using a multitaper method, but this significantly increases the computational burden. It is critical to average power spectra from lateral A-lines for the improvement of scatterer size estimation. Averaging approximately 10 independent A-lines laterally with an axial window length 10 times the center frequency wavelength optimized trade-offs between spatial resolution and the variance of scatterer size estimates. Applying the concept of a time-bandwidth product, this suggests using analysis blocks that contain at least 30 independent samples of the echo signal. The estimation accuracy and precision depend on the ka range where k is the wave number and a is the effective scatterer size. This introduces a region-of-interest depth dependency to the accuracy and precision because of preferential attenuation of higher frequency sound waves in tissuelike media. With the 5 to 13 MHz, transducer ka ranged from 0.5 to 1.6 for scatterers in the test phantom, which is a favorable range, and the accuracy and precision of scatterer size estimations were both within approximately 5% using optimal analysis block dimensions. When the 4- to 9-MHz transducer was used, the ka value ranged from 0.3 to 0.8 to 1.1 for the experimental conditions, and the accuracy and precision were found to be approximately 10% and 10% to 25%, respectively. Although the experiments were done with 2 specific models of transducers on the test phantom, the results can be generalized to similar clinical arrays available from a variety of manufacturers and/or for different size of scatterers with similar ka range.
Collapse
Affiliation(s)
- Wu Liu
- Department of Medical Physics, University of Wisconsin–Madison, 1111 Highland Avenue, Madison WI 53705, USA
- Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Dr, Stanford, CA 94305, USA
| | - James A. Zagzebski
- Department of Medical Physics, University of Wisconsin–Madison, 1111 Highland Avenue, Madison WI 53705, USA
| |
Collapse
|
13
|
Wear KA. Mechanisms for attenuation in cancellous-bone-mimicking phantoms. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2008; 55:2418-25. [PMID: 19049921 PMCID: PMC6935503 DOI: 10.1109/tuffc.949] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Broadband ultrasound attenuation (BUA) in cancellous bone is useful for prediction of osteoporotic fracture risk, but its causes are not well understood. To investigate attenuation mechanisms, 9 cancellous-bone-mimicking phantoms containing nylon filaments (simulating bone trabeculae) embedded within soft-tissue-mimicking fluid (simulating marrow) were interrogated. The measurements of frequency-dependent attenuation coefficient had 3 separable components: 1) a linear (with frequency) component attributable to absorption in the soft-tissue-mimicking fluid, 2) a quasilinear (with frequency) component, which may include absorption in and longitudinal-shear mode conversion by the nylon filaments, and 3) a nonlinear (with frequency) component, which may be attributable to longitudinal-longitudinal scattering by the nylon filaments. The slope of total linear (with frequency) attenuation coefficient (sum of components #1 and #2) versus frequency was found to increase linearly with volume fraction, consistent with reported measurements on cancellous bone. Backscatter coefficient measurements in the 9 phantoms supported the claim that the nonlinear (with frequency) component of attenuation coefficient (component #3) was closely associated with longitudinal-longitudinal scattering. This work represents the first experimental separation of these 3 components of attenuation in cancellous bone-mimicking phantoms.
Collapse
Affiliation(s)
- Keith A Wear
- U.S. Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, MD, USA.
| |
Collapse
|
14
|
Wear KA, Harris GR. Frequency dependence of backscatter from thin, oblique, finite-length cylinders measured with a focused transducer-with applications in cancellous bone. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 124:3309-14. [PMID: 19045813 PMCID: PMC9166175 DOI: 10.1121/1.2980524] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A model is presented for the echo from a thin, oblique, finite-length cylinder. The echo is calculated from the line integral of the transducer directivity pattern along the cylinder axis. The model was validated with broadband pulse-echo measurements from (1) a perpendicular (to the ultrasound beam) nylon wire as a function of lateral displacement from the beam center, (2) a tilted nylon wire as a function of the angle of inclination relative to the ultrasound beam, and (3) a quasi-parallel-nylon-wire phantom, which mimicked the scattering properties of cancellous bone. The transducer directivity pattern (as a function of position and frequency) was measured with a membrane hydrophone. The model predicts an approximately cubic frequency dependence of backscatter coefficient from the phantom, as has been observed experimentally in cancellous bone. The model also predicts the relationship between the cylinder length and the exponent of a power law fit to backscatter coefficient versus frequency, which is 4 for very short (compared to a wavelength) cylinders and asymptotically approaches 3 for very long cylinders.
Collapse
Affiliation(s)
- Keith A Wear
- U. S. Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, Maryland 20993, USA.
| | | |
Collapse
|
15
|
Wear KA, Padilla F, Laugier P. Comparison of the Faran Cylinder Model and the Weak Scattering Model for predicting the frequency dependence of backscatter from human cancellous femur in vitro. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 124:1408-10. [PMID: 19045632 PMCID: PMC9341363 DOI: 10.1121/1.2956480] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
This letter presents the first side-by-side comparison of the Faran Cylinder Model and the Weak Scattering Model for predicting backscatter from human femur. Both models are applied to the same dataset of frequency-dependent backscatter coefficients from 26 human femur cancellous bone samples in vitro. The Faran Cylinder Model predicts a slightly slower rate of increase of backscatter with frequency than the Weak Scattering Model, but both models are in reasonable agreement with the data and with each other, given the uncertainty in the measurements.
Collapse
Affiliation(s)
- Keith A Wear
- Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland 20993, USA
| | | | | |
Collapse
|
16
|
Wear KA. Ultrasonic scattering from cancellous bone: a review. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2008; 55:1432-41. [PMID: 18986932 PMCID: PMC6935504 DOI: 10.1109/tuffc.2008.818] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This paper reviews theory, measurements, and computer simulations of scattering from cancellous bone reported by many laboratories. Three theoretical models (binary mixture, Faran cylinder, and weak scattering) for scattering from cancellous bone have demonstrated some consistency with measurements of backscatter. Backscatter is moderately correlated with bone mineral density in human calcaneus in vitro (r(2) = 0.66 - 0.68). Backscatter varies approximately as frequency cubed and trabecular thickness cubed in human calcaneus and femur in vitro. Backscatter from human calcaneus and bovine tibia exhibits substantial anisotropy. So far, backscatter has demonstrated only modest clinical utility. Computer simulation models have helped to elucidate mechanisms underlying scattering from cancellous bones.
Collapse
Affiliation(s)
- K A Wear
- Center for Devices & Radiol. Health, U.S. Food & Drug Adm., Silver Spring, MD, USA.
| |
Collapse
|
17
|
Padilla F, Jenson F, Bousson V, Peyrin F, Laugier P. Relationships of trabecular bone structure with quantitative ultrasound parameters: in vitro study on human proximal femur using transmission and backscatter measurements. Bone 2008; 42:1193-202. [PMID: 18396124 DOI: 10.1016/j.bone.2007.10.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 09/28/2007] [Accepted: 10/23/2007] [Indexed: 10/22/2022]
Abstract
The present study was designed to assess the relationships between QUS parameters and bone density or microarchitecture on samples of human femoral trabecular bone. The normalized slope of the frequency-dependent attenuation (nBUA), the speed of sound (SOS) and the broadband ultrasound backscatter coefficient (BUB) were measured on 37 specimens of pure trabecular bones removed from upper parts of fresh human femurs. Bone mineral density (BMD) was assessed using a clinical scanner. Finally, 8 mm diameter cylindrical cores were extracted from the specimens and their microarchitecture was reconstructed after synchrotron radiation microtomography experiments (isotropic resolution of 10 microm). A large number of microarchitectural parameters were computed, describing morphology, connectivity and geometry of the specimens. BMD correlated with all the microarchitectural parameters and the number of significant correlations was found among the architectural parameters themselves. All QUS parameters were significantly correlated to BMD (R=0.83 for nBUA, R=0.81 for SOS and R=0.69 for BUB) and to microarchitectural parameters (R=-0.79 between nBUA and Tb.Sp, R=-0.81 between SOS and Tb.Sp, R=-0.65 between BUB and BS/BV). Using multivariate model, it was found that microstructural parameters adds 10%, 19%, and 4% to the respective BMD alone contribution for the three variables BUA, SOS and BUB. Moreover, the RMSE was reduced by up to 50% for SOS, by up to 21% for nBUA and up to 11% when adding structural variables to BMD in explaining QUS results. Given the sample, which is not osteoporosis-enriched, the added contribution is quite substantial. The variability of SOS was indeed completely explained by a multivariate model including BMD and independent structural parameters (R(2)=0.94). The inverse problem on the data presented here has been addressed using simple and multiple linear regressions. It was shown that the predictions (in terms of R(2) or RMSE) of microarchitectural parameters was not enhanced when combining 2 or 3 QUS in multiple linear regressions compared to the prediction obtained with one QUS parameter alone. The best model was found for the prediction of Tb.Th() from BUA (R(2)=0.58, RMSE=17 microm). Given the high values of RMSE, these linear models appear of limited clinical value, suggesting that appropriate models have to be derived in order to solve the inverse problem. In this regard, a very interesting multivariate model was found for nBUA and BUB with Tb.Th and Tb.N, in agreement with single scattering theories by random medium. However, the source of residual variability of nBUA and BUB (15% and 45% respectively) remained unexplained.
Collapse
Affiliation(s)
- F Padilla
- CNRS, UMR7623 LIP, Paris, F-75006 France.
| | | | | | | | | |
Collapse
|
18
|
Deligianni DD, Apostolopoulos KN. Characterization of dense bovine cancellous bone tissue microstructure by ultrasonic backscattering using weak scattering models. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2007; 122:1180-90. [PMID: 17672664 DOI: 10.1121/1.2749461] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A weak scattering model was proposed for the ultrasonic frequency-dependent backscatter in dense bovine cancellous bone, using two autocorrelation functions to describe the medium: one with discrete homogeneities (spherical distribution of equal spheres) and another, which considers tissue as an inhomogeneous continuum (densely populated medium). The inverse problem to estimate trabecular thickness of bone tissue has been addressed. A combination of the two autocorrelation functions was required to closely approximate the backscatter from bovine bone with various microarchitecture, given that the shape of trabeculae ranges from a rodlike to a platelike shape. Because of the large variation in trabecular thickness, both at an intraspecimen and an interspecimen level, thickness distributions for individual trabeculae for each bone specimen were obtained, and dominant trabecular sizes were determined. Comparison of backscatter measurements to theoretical predictions indicated that there were more than one dominant trabecular sizes that scatter sound for most specimens. Linear regression, performed between dominant trabecular thickness and estimated correlation length, showed significant linear correlation (R(2)=0.81). Attenuation due to scattering by a continuous distribution of scatterers was predicted to be linear over a frequency range from 0.3 to 0.9 MHz, suggesting a possibility that scattering may be a significant source of attenuation.
Collapse
Affiliation(s)
- D D Deligianni
- Biomedical Engineering Laboratory, Department of Mechanical Engineering and Aeronautics, University of Patras, Rion, Greece.
| | | |
Collapse
|
19
|
Hoffmeister BK, Jones CI, Caldwell GJ, Kaste SC. Ultrasonic characterization of cancellous bone using apparent integrated backscatter. Phys Med Biol 2006; 51:2715-27. [PMID: 16723761 DOI: 10.1088/0031-9155/51/11/002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Apparent integrated backscatter (AIB) is a measure of the frequency-averaged (integrated) backscattered power contained in some portion of a backscattered ultrasonic signal. AIB has been used extensively to study soft tissues, but its usefulness as a tissue characterization technique for cancellous bone has not been demonstrated. To address this, we performed measurements on 17 specimens of cancellous bone over two different frequency ranges using a 1 MHz and 5 MHz broadband ultrasonic transducer. Specimens were obtained from bovine tibiae and prepared in the shape of cubes (15 mm side length) with faces oriented along transverse (anterior, posterior, medial and lateral) and longitudinal (superior and inferior) principal anatomic directions. A mechanical scanning system was used to acquire multiple backscatter signals from each direction for each cube. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (R2 = 0.817) and longitudinal (R2 = 0.488) directions using the 5 MHz transducer. In contrast, the correlations with density were much weaker for the 1 MHz transducer (R2 = 0.007 transverse, R2 = 0.228 longitudinal). In all cases where a significant correlation was observed, AIB was found to decrease with increasing BMD.
Collapse
Affiliation(s)
- B K Hoffmeister
- Department of Physics, Rhodes College, 2000 North Parkway, Memphis, TN 38112, USA.
| | | | | | | |
Collapse
|
20
|
Padilla F, Jenson F, Laugier P. Estimation of trabecular thickness using ultrasonic backcatter. ULTRASONIC IMAGING 2006; 28:3-22. [PMID: 16924879 DOI: 10.1177/016173460602800102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We present a method to estimate trabecular thickness (Tb.Th) in trabecular bones from ultrasound backscatter measurements. The estimation scheme is based on a nonlinear adjustment of predictions from a model to experimental data. The model assumes weak scattering from bone, where scattering is assumed to arise from the elastic solid trabeculae. The fluctuations of acoustical properties between bone tissue and the saturating fluid are assumed to be random and are described by the 3-D spatial autocorrelation function of the medium. In this paper, a Gaussian autocorrelation function is used. The inversion procedure is applied to a set of data measured on 33 femoral bone specimens. Results show that the model can predict both the magnitude and the frequency-dependence of the backscatter coefficient (root mean square error RMSE = 1 dB). The estimated trabecular thickness values are compared to the true trabecular thickness measured on high resolution microcomputed tomography 3-D reconstruction of bones microarchitecture. A close agreement is obtained on average over the group of specimens between predictions and the reference values: true Tb.Th is 132 +/- 12 microm and estimated Tb.Th is 134 +/- 15 microm. However, a moderate correlation between actual and estimated Tb.Th values is found (R2 = 0.44, p<10(-4), RMSE = 8.7 microm) suggesting a modest predictability at the individual level. Sources for the variability of the estimator are studied. Using synthetic rf signals, we demonstrate that the fundamental limitation of the estimator due to speckle noise is approximately 5 microm. Taking into account the measurement errors, the total uncertainty on Tb.Th estimates is of the order of 7 microm. The influence of the attenuation compensation function used to derive the backscatter coefficient is studied. In particular, we demonstrate the necessity of compensating for the effect of the gating time window. The results are discussed with respect to their meaningful clinical value. The requirements to be fulfilled by the performance of the technique change with regard to the question being posed. Two different strategies are examined: 1. characterize trabecular thickness without consideration of bone quantity (or bone mineral density) and 2. estimate trabecular thickness after adjustment for BMD. Considering the first strategy, a comparison between the precision of our estimator and the biological variability leads us to the conclusion that our estimator should only permit to distinguish between micro-architectures characterized by extreme values of trabecular thickness (i.e., very thin or very thick trabecular thickness). In this respect, it would be interesting to test whether the estimator is able to discriminate between rod-like (thin) and plate-like (thick) structures that are known to influence differently bone strength. The second strategy is more demanding in terms of technique performance and our estimator is not able yet to catch small differences in Tb.Th values expected after adjustment to bone density. Progress in the field will require a significant reduction in speckle noise and measurement errors and/or the development of other and more efficient microstructural estimators.
Collapse
Affiliation(s)
- Frédéric Padilla
- Laboratoire d'Imagerie Paramétrique, CNRS UMR 7623, Université-Pierre et Marie Curie-Paris 6, France.
| | | | | |
Collapse
|
21
|
Wear KA. Fred Lizzi's statistical framework and the interpretation of ultrasound backscatter from bone. ULTRASONIC IMAGING 2006; 28:41-2. [PMID: 16924881 DOI: 10.1177/016173460602800104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
|
22
|
Jenson F, Padilla F, Bousson V, Bergot C, Laredo JD, Laugier P. In vitro ultrasonic characterization of human cancellous femoral bone using transmission and backscatter measurements: relationships to bone mineral density. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2006; 119:654-63. [PMID: 16454319 DOI: 10.1121/1.2126936] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Thirty-eight slices of pure trabecular bone 1-cm thickness were extracted from human proximal femurs. A pair of 1-MHz central frequency transducers was used to measure quantitative ultrasound (QUS) parameters in transmission [normalized broadband ultrasound attenuation (nBUA), speed of sound (SOS)] and in backscatter [broadband ultrasound backscatter (BUB)]. Bone mineral density (BMD) was measured using clinical x-ray quantitative computed tomography. Site-matched identical region of interest (ROIs) of 7 x 7 mm2 were positioned on QUS and QCT images. This procedure resulted in 605 ROIs for all the specimens data pooled together. The short-term precision of the technique expressed in terms of CV was found to be 2.3% for nBUA, 0.3% for SOS and 4.5% for BUB. Significant linear correlation between QUS and BMD were found for all the 605 ROIs pooled, with r2 values of 0.73, 0.77, and 0.58 for nBUA, SOS, and BUB, respectively (all p < 0.05). For the BUB, the best regression was obtained with a polynomial fit of second order (r2 = 0.63). An analysis of measurements errors was developed. It showed that the residual variability of SOS is almost completely predicted by measurements errors, which is not the case for BUA and BUB, suggesting a role for micro-architecture in the determination of BUA and BUB.
Collapse
Affiliation(s)
- F Jenson
- Laboratoire d'Imagerie Paramétrique, Université Paris VI, UMR CNRS 7623, 15 rue de l'Ecole de Medecine, 75006 Paris, France
| | | | | | | | | | | |
Collapse
|
23
|
Bigelow TA, O'Brien WD. Signal processing strategies that improve performance and understanding of the quantitative ultrasound SPECTRAL FIT algorithm. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2005; 118:1808-19. [PMID: 16240839 DOI: 10.1121/1.2000752] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Quantifying the size of the tissue microstructure using the backscattered power spectrum has had limited success due to frequency-dependent attenuation along the propagation path, thus masking the frequency dependence of the scatterer size. Previously, the SPECTRAL FIT algorithm was developed to solve for total attenuation and scatterer size simultaneously [Bigelow et al., J. Acoust. Soc. Am. 117, 1431-1439 (2005)]. Herein, the outcomes from signal processing strategies on the SPECTRAL FIT algorithm are investigated. The signal processing methods can be grouped into two categories, viz., methods that improve the performance of the algorithm and methods that provide insight. The methods that improve the performance include compensating for the windowing function used to gate the time-domain signal, averaging the spectra in the normal frequency domain rather than the log domain to improve the precision of the scatterer size and attenuation estimates, improving the selection of the usable frequency range for the SPECTRAL FIT algorithm, and improving the compensation for electronic noise. The methods that provide insight demonstrate that the anomalous rapid fluctuations of the backscattered power spectrum do not affect the SPECTRAL FIT algorithm, and accurate attenuation estimates can be obtained even when the correct scatterer geometry (i.e., form factor) is not known.
Collapse
Affiliation(s)
- Timothy A Bigelow
- Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois, 405 North Mathews, Urbana, Illinois 61801, USA
| | | |
Collapse
|
24
|
Bigelow TA, Oelze ML, O'Brien WD. Estimation of total attenuation and scatterer size from backscattered ultrasound waveforms. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2005; 117:1431-9. [PMID: 15807030 DOI: 10.1121/1.1858192] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Quantitative ultrasound techniques using backscattered echoes have had limited success in vivo due to the frequency-dependent attenuation along the entire propagation path masking the frequency dependence of the backscatter. Herein, total attenuation and scatterer size are estimated simultaneously by an analysis of the in vivo backscattered power spectrum using two approaches. The simulations used to evaluate the two approaches used frequencies between 4 and 11 MHz with an effective scatterer radius of 25 microm. The first approach was based on approximations of the in vivo backscattered power spectrum (i.e., assumed Gaussian function), wherein attenuation and size were estimated by assuming each was a Gaussian transformation performed on Gaussian power spectra. The approach had poor accuracy due to the backscattered power spectra not being sufficiently modeled by a Gaussian function. The second approach estimated attenuation and size by fitting a modified reference spectrum to the in vivo backscattered power spectrum without any assumptions about the shape of the spectrum. The accuracy of the size estimate was better than 20% for signal-to-noise ratio >6 dB, window lengths greater than 4 mm, and attenuation between 0 and 1 dB/cm-MHz. However, the precision quickly degraded with increasing noise, increasing attenuation, and decreasing window length.
Collapse
Affiliation(s)
- Timothy A Bigelow
- Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801, USA
| | | | | |
Collapse
|
25
|
Hakulinen MA, Töyräs J, Saarakkala S, Hirvonen J, Kröger H, Jurvelin JS. Ability of ultrasound backscattering to predict mechanical properties of bovine trabecular bone. ULTRASOUND IN MEDICINE & BIOLOGY 2004; 30:919-27. [PMID: 15313324 DOI: 10.1016/j.ultrasmedbio.2004.04.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2003] [Revised: 04/05/2004] [Accepted: 04/15/2004] [Indexed: 05/10/2023]
Abstract
Ultrasound (US) backscatter measurements have been proposed for the quantitative evaluation of bone quality. In this study, we explored the ability of broadband US backscatter (BUB) and integrated reflection coefficient (IRC) to predict density and mechanical properties of trabecular bone, as compared to normalized broadband US attenuation (nBUA) and speed of sound (SOS). These acoustic parameters were measured in 41 in vitro samples of bovine trabecular bone and correlated with a number of mechanical parameters and with volumetric bone mineral density (BMDvol). BUB correlated statistically significantly with the volumetric bone mineral density (r = 0.61, p < 0.01), Young's modulus (r = 0.40, p < 0.01) and ultimate strength (r = 0.40, p < 0.01). IRC was even more strongly correlated with BMD(vol) (r = 0.92, p < 0.01) and most of the mechanical parameters (0.81 < r < 0.85). Strong correlations were also found between mechanical parameters and SOS (0.87 < r < 0.90). No significant correlation was found between attenuation (nBUA) and either BMD(vol) or mechanical parameters. Reproducibilities (standardized CV%) of BUB (3.5%) and IRC (1.5%) were comparable to those of nBUA (2.3%) and SOS (0.5%). To conclude, BUB and IRC are promising parameters for the evaluation of density and mechanical properties of trabecular bone. Advantageously, BUB and IRC can be determined with a single transducer, hypothetically enabling measurements at many clinically relevant fracture sites.
Collapse
Affiliation(s)
- Mikko A Hakulinen
- Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital and University of Kuopio, Kuopio, Finland.
| | | | | | | | | | | |
Collapse
|
26
|
Oelze ML, O'Brien WD. Defining optimal axial and lateral resolution for estimating scatterer properties from volumes using ultrasound backscatter. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2004; 115:3226-3234. [PMID: 15237847 DOI: 10.1121/1.1739484] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. Typically, the backscattered power spectrum is calculated from a region of interest (ROI) within some larger volume. The dimensions of the ROI are defined axially by the spatial length corresponding to the time gate and laterally by the number of scan lines included in the ROI. Averaging the backscattered power spectra from several independent scan lines can reduce the presence of noise caused by electronics and by the random scatterer spacings, but also decreases the lateral resolution of the interrogation region. Furthermore, larger axial gate lengths can be used to reduce the effects of noise and improve the precision and accuracy of scatterer property estimates but also decreases the axial resolution. A trade-off exists between the size of the ROI (the number of scan lines used, the separation distance between each scan line, the axial gate length) and the accuracy and precision of scatterer property estimates. A series of simulations and measurements from physical phantoms were employed to examine these trade-offs. The simulations and phantom measurements indicated the optimal lateral and axial sizes of the ROI, where estimate accuracy and precision were better than 10% and 5%, respectively, occurred at 4 to 5 beamwidths laterally and 15 to 20 spatial pulse lengths axially.
Collapse
Affiliation(s)
- Michael L Oelze
- Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois, 405 North Mathews, Urbana, Illinois 61801, USA.
| | | |
Collapse
|
27
|
Abstract
As was true 10 years ago, tremendous interest surrounds the concept of "bone quality," as shown by the intense and growing research activity in the field. The urgency to advance knowledge in this area is motivated by the need to understand not only the causes of increased skeletal fragility with aging and disease, but also the mechanisms by which drugs reduce fracture risk. As reflected in the preceding articles, in the past decade collaborations between biologists, physicists, engineers and clinicians have led to new insights regarding the biological, material and structural features that contribute to skeletal fragility. Despite these new insights, important issues remain unresolved. Our challenges lie in identifying, describing and understanding the totality of features and characteristics that determine a bone's ability to resist fracture, and using this information to identify new therapeutic targets and develop better biomarkers and noninvasive imaging modalities. This summary is intended to integrate reports in the literature with presentations and discussions that occurred during the meeting, to highlight areas of consensus and those of continued controversy, and thus to identify critical areas for future research.
Collapse
|
28
|
Wear KA, Laib A. The dependence of ultrasonic backscatter on trabecular thickness in human calcaneus: theoretical and experimental results. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2003; 50:979-86. [PMID: 12952089 PMCID: PMC6931151 DOI: 10.1109/tuffc.2003.1226542] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Trabecular thickness within cancellous bone is an important determinant of osteoporotic fracture risk. Noninvasive assessment of trabecular thickness potentially could yield useful diagnostic information. Faran's theory of elastic scattering from a cylindrical object immersed in a fluid has been used to predict the dependence of ultrasonic backscatter on trabecular thickness. The theory predicts that, in the range of morphological and material properties expected for trabecular bone, the backscatter coefficient at 500 kHz should be approximately proportional to trabecular thickness to the power of 2.9. Experimental measurements of backscatter coefficient were performed on 43 human calcaneus samples in vitro. Mean trabecular thicknesses on the 43 samples were assessed using micro computed tomography (CT). A power law fit to the data showed that the backscatter coefficient empirically varied as trabecular thickness to the 2.8 power. The 95% confidence interval for this exponent was 1.7 to 3.9. The square of the correlation coefficient for the linear regression to the log transformed data was 0.40. This suggests that 40% of variations in backscatter may be attributed to variations in trabecular thickness. These results reinforce previous studies that offered validation for the Faran cylinder model for prediction of scattering properties of cancellous bone, and provide added evidence for the potential diagnostic utility of the backscatter measurement.
Collapse
Affiliation(s)
- Keith A Wear
- U.S. Food and Drug Administration, Center for Devices and Radiological Health, Rockville, MD 20852, USA.
| | | |
Collapse
|
29
|
Wear KA. Characterization of trabecular bone using the backscattered spectral centroid shift. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2003; 50:402-7. [PMID: 12744396 PMCID: PMC9134221 DOI: 10.1109/tuffc.2003.1197963] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ultrasonic attenuation in bone in vivo is generally measured using a through-transmission method at the calcaneus. Although attenuation in calcaneus has been demonstrated to be a useful predictor for osteoporotic fracture risk, measurements at other clinically important sites, such as hip and spine, could potentially contain additional useful diagnostic information. Through-transmission measurements may not be feasible at these sites due to complex bone shapes and the increased amount of intervening soft tissue. Centroid shift from the backscattered signal is an index of attenuation slope and has been used previously to characterize soft tissues. In this paper, centroid shift from signals backscattered from 30 trabecular bone samples in vitro were measured. Attenuation slope also was measured using a through-transmission method. The correlation coefficient between centroid shift and attenuation slope was -0.71. The 95% confidence interval was (-0.86, -0.47). These results suggest that the backscattered spectral centroid shift may contain useful diagnostic information potentially applicable to hip and spine.
Collapse
Affiliation(s)
- Keith A Wear
- U.S. Food and Drug Administration, Center for Devices and Radiological Health, Rockville, MD 20852, USA.
| |
Collapse
|
30
|
Jenson F, Padilla F, Laugier P. Prediction of frequency-dependent ultrasonic backscatter in cancellous bone using statistical weak scattering model. ULTRASOUND IN MEDICINE & BIOLOGY 2003; 29:455-464. [PMID: 12706197 DOI: 10.1016/s0301-5629(02)00742-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The goal of this study was to propose a model for the ultrasonic frequency-dependent backscatter coefficient in cancellous bone. This model allows us to address the inverse problem and to predict the mean trabecular thickness. A weak scattering model is used and the backscatter coefficient is expressed in terms of an autocorrelation function of the medium. Different autocorrelation functions (Gaussian, exponential and densely populated media) were used to compute the backscatter coefficient and comparison is made with experimental data for 19 specimens and for frequency ranging from 0.4 to 1.2 MHz. For each specimen, a nonlinear regression was performed and the mean trabecular thickness is estimated. Experimental data and theoretical predictions were averaged over the 19 specimens. A good agreement between experimental data and predictions was found for both the magnitude and the frequency-dependence of the backscatter coefficient. We also found a good agreement between the experimental mean trabecular thickness (Tb. Th = 130 +/- 6.5 micro m) derived from the analysis of bone 3-D microarchitecture using high-resolution microtomography and theoretical predictions (d(Gauss) = 140 +/- 10 micro m, d(exponential) = 153 +/- 12.5 micro m and d(dense) = 138 +/- 6.5 micro m). These results open interesting prospects for the estimation of the mean trabecular thickness from in vivo measurements.
Collapse
|