2009 Ieee International Ultrasonics Symposium, 2009
Ultrasound backscatter has the potential to provide information useful for the diagnosis and moni... more Ultrasound backscatter has the potential to provide information useful for the diagnosis and monitoring of bone disorders (e.g., osteopenia, osteoporosis, and hard tissue sarcomas). We hypothesize that the Renyi entropy, previously shown to be sensitive to subtle changes in scattering from soft tissues, may also offer some utility in characterizing properties of bone. The goals of the present work were to investigate and compare the ability of energy- and entropy-based analyses of radio-frequency ultrasonic backscatter, to assess material properties of cancellous bone with respect to conventional quantitative computed X-ray tomography (QCT).
The use of polymethylmethacrylate (PMMA)-based bone cement for implantation of metallic prosthese... more The use of polymethylmethacrylate (PMMA)-based bone cement for implantation of metallic prostheses is becoming increasingly common. Failure of a cemented prosthesis often occurs when there is weak bonding at the bone/cement or cement/metal interface. The addition of hydroxyapatite (HA) particles, a synthetically produced version of the natural mineral in bone, may improve the adhesion by promoting bone growth into the cement itself. The curing time of PMMA bone cement determines the speed of implant insertion, which can affect the mechanical strength of the cement. Pure PMMA has a well-characterized curing time of 9-12 minutes, depending on environmental factors such as temperature and humidity. By measuring the propagation of ultrasonic pulses through a sample of bone cement, the curing process can be monitored. As the material hardens, the velocity of an ultrasonic pulse increases, and the attenuation decreases. These parameters were measured as a function of time for PMMA mixed with 0, 10 and 30investigation of the curing process as a function of hydroxyapatite concentration.
This thesis seeks to contribute to a better understanding of the physics of interaction of ultras... more This thesis seeks to contribute to a better understanding of the physics of interaction of ultrasonic waves with inhomogeneous and anisotropic media, one example of which is the human heart. The clinical success of echocardiography has generated a considerable interest in the development of ultrasonic techniques to measure the elastic properties of heart tissue. It is hypothesized that the elastic properties of myocardium are influenced by the interstitial content and organization of collagen. Collagen, which is the main component of tendon, interconnects the muscle cells of the heart to form locally unidirectional myofibers. This thesis therefore employs ultrasonic techniques to characterize the linear elastic properties of both heart and tendon. The linear elastic properties of tissues possessing a unidirectional arrangement of fibers may be described in terms of five independent elastic stiffness coefficients. Three of these coefficients were determined for formalin fixed specimens of bovine Achilles tendon and human myocardium by measuring the velocity of longitudinal mode ultrasonic pulses as a function of angle of propagation relative to the fiber axis of the tissue. The remaining two coefficients were determined by measuring the velocity of transverse mode ultrasonic waves through these tissues. To overcome technical difficulties associated with the extremely high attenuation of transverse mode waves at low megahertz frequencies, a novel measurement system was developed based on the sampled continuous wave technique. Results of these measurements were used to assess the influence of interstitial collagen, and to model the mechanical properties of heart wall.
A low-intensity ultrasound (LIUS) was examined for its possible therapeutic effects on degenerati... more A low-intensity ultrasound (LIUS) was examined for its possible therapeutic effects on degenerative osteoarthritic cartilage. Along with the daily treatment of 5 ng interleukin-1β (IL−1β) for 5 d, an engineered 3D neocartilage construct was used as an in vitro OA model. Followed by 24 h preincubation with the first dose of IL−1β, the constructs were then given ultrasonic stimulation (frequency 1.5 MHz and SATA 30 mW/cm2) once a day up to 5 d for the predetermined time. Fresh IL−1β was added before the stimulation. The difference in the cell number and viability was insignificant between control (US−/IL+) and LIUS-stimulated groups. As the daily stimulation time was extended, the GAG contents in the constructs themselves significantly increased with 50 min stimulation but those released into the culture medium remained unaffected by LIUS. While the gene expression level of aggrecan was similar between control and LIUS (50 min) group, the ratio of collagen type II to type I was found to be higher in the control. The mRNA level of matrix metalloproteinase (MMP)-1 was substantially downregulated in the stimulated construct and that of MMP-13 was indifferent between control and stimulated one. The endogenous expression of transforming growth factor (TGF)-β1 and β3 was barely responsive to the LIUS stimulation. From histologic analysis, more intense GAG deposition was clearly identified with the LIUS-stimulated constructs. This study indicates that LIUS may have a significant potential to be a chondroprotective stimulant for osteoarthritic cartilage. (E-mail: kpark@kist.re.kr)
The Journal of the Acoustical Society of America, Jun 1, 1996
Clinical implementation of quantitative ultrasonic tissue characterization is likely to require i... more Clinical implementation of quantitative ultrasonic tissue characterization is likely to require imaging the heart with sound propagating at varying angles relative to the fibers of the heart. Under these circumstances, the variation of the ultrasonic properties of myocardium with the angle of propagation relative to the myofibers may represent a significant source of potential misinterpretation. In the present study, the systematic approach of assessing the impact of anisotropy on quantitative myocardial tissue characterization is extended by reporting results of a recent in vitro study to measure the anisotropy of the slope of ultrasonic attenuation in specimens of formalin fixed human myocardium. Data obtained from regions of remote infarct are presented and compared to data acquired from regions identified to be free of infarct. The slope of attenuation for both regions exhibit a sinusoid-like dependence on angle that is approximately doubled for propagation parallel to the fibers as compared to perpendicular. These results are, in turn, compared to an earlier study from the laboratory that examined the effects of myocardial infarction on ultrasonic attenuation and interstitial collagen content in freshly excised canine hearts. Discussion regarding the analysis and interpretation of measurements of slope of attenuation is presented as well as a discussion of the possible influence of formalin fixation on our results.
... Brent K. Hoffmeister, Andrew K. Wong, Edward D. Verdonk, Samuel A. Wickline, James G. Miller ... more ... Brent K. Hoffmeister, Andrew K. Wong, Edward D. Verdonk, Samuel A. Wickline, James G. Miller ... data detailing the ultrasonic anisotropy of cardiac muscle and delineating the shift in myofiber orientation from epicardium to endocardium.26 Histologic studies by Streeter et al. ...
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2015
Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused... more 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.
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology, 2002
ABSTRACT A previous study has shown that the cross-sectional area of the left ventricular cavity ... more ABSTRACT A previous study has shown that the cross-sectional area of the left ventricular cavity (LV) increases immediately after defibrillation, suggesting that the defibrillation shock may cause relaxation. Since a single area slice may not reflect the entire myocardium, we wanted to test the relaxation hypothesis by evaluating volume. Ten to twenty defibrillation shocks were delivered in each of six dogs. A catheter was placed in the LV to measure intraventricular volume (IVV). Ultrasound images of the LV were recorded simultaneously with IVV. LV cavity area increased 13% (p
The Journal of the Acoustical Society of America, 2015
Ultrasonic backscatter techniques are being developed to diagnose osteoporosis. Tissues that lie ... more 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 d...
The Journal of the Acoustical Society of America, 2015
Ultrasonic backscatter techniques are being developed to diagnose osteoporosis. Tissues that lie ... more 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.
Backscatter difference measurements may be used to detect changes in bone caused by osteoporosis.... more Backscatter difference measurements may be used to detect changes in bone caused by osteoporosis. The backscatter difference technique measures the power difference between two portions of an ultrasonic backscatter signal. The goal of this study is to evaluate the feasibility of using an ultrasonic imaging system to perform backscatter difference measurements of bone. Ultrasonic images and backscatter signals were acquired from 24 specimens of human cancellous bone. The signals were analyzed in the frequency domain to determine the normalized mean backscatter difference (nMBD) and in the time domain to determine the normalized backscatter amplitude ratio (nBAR). The images were analyzed to determine the normalized pixel value difference (nPVD), which measures the difference in average pixel brightness between regions of interest placed at two different depths in the image. All three parameters were found to increase with bone mineral density. The signal-based parameters, nMBD and nB...
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology, 2002
ABSTRACT Medical equipment can unintentionally allow the flow of power line current through the p... more ABSTRACT Medical equipment can unintentionally allow the flow of power line current through the patient causing complete hemodynamic collapse without fibrillation. This study tests the hypothesis that static wall thickening accompanies AC induced collapse via an isovolumic state. In 3 dogs, we delivered AC current stimulation ranging from 10-160 Hz and 10-1000 μA to the right ventricle. A steerable, quadripolar catheter was placed in the apex of the left ventricle and deflected towards the basal region to measure left ventricular volume. Two dimensional, short-axis ultrasound images of the LV endocardial walls were recorded to measure wall thickness. Our results indicate that wall thickness during collapse is significantly greater than during systole (Δ thickness =11.7±12 mm, p
Medical equipment can unintentionally allow the flow of small amounts of AC current through the p... more Medical equipment can unintentionally allow the flow of small amounts of AC current through the patient causing hemodynamic collapse without fibrillation. This study examines the mechanical response of the left ventricle during AC induced hemodynamic collapse. Six dogs received 5 seconds of AC current stimulation ranging from 4-160 Hz and 10-1000 μA to the right ventricle. A quadripolar catheter was placed in the apex of the left ventricle to measure left ventricular volume. Short-axis ultrasound images were recorded to measure left ventricular cross sectional area and wall thickness. Our results showed that the mean volume of the left ventricle during collapse was significantly smaller (p < 0.05) than the mean volume preceding collapse. Cross sectional area also decreased significantly and wall thickness increased. This suggests that the heart assumes a contracted, systole-like state during collapse.
American journal of physiology. Heart and circulatory physiology, 2003
A previous two-dimensional (2D) ultrasound study suggested that there is relaxation of the myocar... more A previous two-dimensional (2D) ultrasound study suggested that there is relaxation of the myocardium after defibrillation. The 2D study could not measure activity occurring within the first 33 ms after the shock, a period that may be critical for discriminating between shock- and excitation-induced relaxation. The objective of our study was to determine the left ventricular (LV) geometry during the first 33 ms after defibrillation. Biphasic defibrillation shocks were delivered 5-50 s after the induction of ventricular fibrillation in each of the seven dogs. One-dimensional, short-axis ultrasound images of the LV cavity were acquired at a rate of 250 samples/s. The LV cavity diameter was computed from 32 ms before to 32 ms after the shock. Preshock and postshock percent changes in LV diameter were analyzed as a function of time with the use of regression analysis. The normalized mean pre- and postshock slopes (0.2 +/- 2.2 and 3.3 +/- 7.9% per 10 ms) were significantly different (P &...
A number of investigators have performed in vitro measurements of cancellous bone to determine ho... more A number of investigators have performed in vitro measurements of cancellous bone to determine how various ultrasonic parameters depend on bone density and trabecular orientation. To facilitate handling and storage of bone specimens, the marrow is often removed prior to ultrasonic measurements. However, the assumption that marrow does not affect ultrasonic measurements at high frequencies (>1 MHz) has not been tested. The goal of this study is to determine the effect of marrow on the ultrasonic properties of bovine cancellous bone at frequencies greater than 1 MHz. Twelve specimens of cancellous bone were obtained from the proximal end of four bovine tibia. Ultrasonic measurements consisting of normalized broadband ultrasonic attenuation (nBUA), speed of sound (SOS) and apparent integrated backscatter (AIB) were measured in each specimen using 2.25 MHz (centre frequency) broadband ultrasonic pulses. These measurements were performed before and after marrow removal either along th...
2009 IEEE International Ultrasonics Symposium, 2009
Ultrasound backscatter has the potential to provide information useful for the diagnosis and moni... more Ultrasound backscatter has the potential to provide information useful for the diagnosis and monitoring of bone disorders (e.g., osteopenia, osteoporosis, and hard tissue sarcomas). We hypothesize that the Renyi entropy, previously shown to be sensitive to subtle changes in scattering from soft tissues, may also offer some utility in characterizing properties of bone. The goals of the present work were to investigate and compare the ability of energy- and entropy-based analyses of radio-frequency ultrasonic backscatter, to assess material properties of cancellous bone with respect to conventional quantitative computed X-ray tomography (QCT).
2009 Ieee International Ultrasonics Symposium, 2009
Ultrasound backscatter has the potential to provide information useful for the diagnosis and moni... more Ultrasound backscatter has the potential to provide information useful for the diagnosis and monitoring of bone disorders (e.g., osteopenia, osteoporosis, and hard tissue sarcomas). We hypothesize that the Renyi entropy, previously shown to be sensitive to subtle changes in scattering from soft tissues, may also offer some utility in characterizing properties of bone. The goals of the present work were to investigate and compare the ability of energy- and entropy-based analyses of radio-frequency ultrasonic backscatter, to assess material properties of cancellous bone with respect to conventional quantitative computed X-ray tomography (QCT).
The use of polymethylmethacrylate (PMMA)-based bone cement for implantation of metallic prosthese... more The use of polymethylmethacrylate (PMMA)-based bone cement for implantation of metallic prostheses is becoming increasingly common. Failure of a cemented prosthesis often occurs when there is weak bonding at the bone/cement or cement/metal interface. The addition of hydroxyapatite (HA) particles, a synthetically produced version of the natural mineral in bone, may improve the adhesion by promoting bone growth into the cement itself. The curing time of PMMA bone cement determines the speed of implant insertion, which can affect the mechanical strength of the cement. Pure PMMA has a well-characterized curing time of 9-12 minutes, depending on environmental factors such as temperature and humidity. By measuring the propagation of ultrasonic pulses through a sample of bone cement, the curing process can be monitored. As the material hardens, the velocity of an ultrasonic pulse increases, and the attenuation decreases. These parameters were measured as a function of time for PMMA mixed with 0, 10 and 30investigation of the curing process as a function of hydroxyapatite concentration.
This thesis seeks to contribute to a better understanding of the physics of interaction of ultras... more This thesis seeks to contribute to a better understanding of the physics of interaction of ultrasonic waves with inhomogeneous and anisotropic media, one example of which is the human heart. The clinical success of echocardiography has generated a considerable interest in the development of ultrasonic techniques to measure the elastic properties of heart tissue. It is hypothesized that the elastic properties of myocardium are influenced by the interstitial content and organization of collagen. Collagen, which is the main component of tendon, interconnects the muscle cells of the heart to form locally unidirectional myofibers. This thesis therefore employs ultrasonic techniques to characterize the linear elastic properties of both heart and tendon. The linear elastic properties of tissues possessing a unidirectional arrangement of fibers may be described in terms of five independent elastic stiffness coefficients. Three of these coefficients were determined for formalin fixed specimens of bovine Achilles tendon and human myocardium by measuring the velocity of longitudinal mode ultrasonic pulses as a function of angle of propagation relative to the fiber axis of the tissue. The remaining two coefficients were determined by measuring the velocity of transverse mode ultrasonic waves through these tissues. To overcome technical difficulties associated with the extremely high attenuation of transverse mode waves at low megahertz frequencies, a novel measurement system was developed based on the sampled continuous wave technique. Results of these measurements were used to assess the influence of interstitial collagen, and to model the mechanical properties of heart wall.
A low-intensity ultrasound (LIUS) was examined for its possible therapeutic effects on degenerati... more A low-intensity ultrasound (LIUS) was examined for its possible therapeutic effects on degenerative osteoarthritic cartilage. Along with the daily treatment of 5 ng interleukin-1β (IL−1β) for 5 d, an engineered 3D neocartilage construct was used as an in vitro OA model. Followed by 24 h preincubation with the first dose of IL−1β, the constructs were then given ultrasonic stimulation (frequency 1.5 MHz and SATA 30 mW/cm2) once a day up to 5 d for the predetermined time. Fresh IL−1β was added before the stimulation. The difference in the cell number and viability was insignificant between control (US−/IL+) and LIUS-stimulated groups. As the daily stimulation time was extended, the GAG contents in the constructs themselves significantly increased with 50 min stimulation but those released into the culture medium remained unaffected by LIUS. While the gene expression level of aggrecan was similar between control and LIUS (50 min) group, the ratio of collagen type II to type I was found to be higher in the control. The mRNA level of matrix metalloproteinase (MMP)-1 was substantially downregulated in the stimulated construct and that of MMP-13 was indifferent between control and stimulated one. The endogenous expression of transforming growth factor (TGF)-β1 and β3 was barely responsive to the LIUS stimulation. From histologic analysis, more intense GAG deposition was clearly identified with the LIUS-stimulated constructs. This study indicates that LIUS may have a significant potential to be a chondroprotective stimulant for osteoarthritic cartilage. (E-mail: kpark@kist.re.kr)
The Journal of the Acoustical Society of America, Jun 1, 1996
Clinical implementation of quantitative ultrasonic tissue characterization is likely to require i... more Clinical implementation of quantitative ultrasonic tissue characterization is likely to require imaging the heart with sound propagating at varying angles relative to the fibers of the heart. Under these circumstances, the variation of the ultrasonic properties of myocardium with the angle of propagation relative to the myofibers may represent a significant source of potential misinterpretation. In the present study, the systematic approach of assessing the impact of anisotropy on quantitative myocardial tissue characterization is extended by reporting results of a recent in vitro study to measure the anisotropy of the slope of ultrasonic attenuation in specimens of formalin fixed human myocardium. Data obtained from regions of remote infarct are presented and compared to data acquired from regions identified to be free of infarct. The slope of attenuation for both regions exhibit a sinusoid-like dependence on angle that is approximately doubled for propagation parallel to the fibers as compared to perpendicular. These results are, in turn, compared to an earlier study from the laboratory that examined the effects of myocardial infarction on ultrasonic attenuation and interstitial collagen content in freshly excised canine hearts. Discussion regarding the analysis and interpretation of measurements of slope of attenuation is presented as well as a discussion of the possible influence of formalin fixation on our results.
... Brent K. Hoffmeister, Andrew K. Wong, Edward D. Verdonk, Samuel A. Wickline, James G. Miller ... more ... Brent K. Hoffmeister, Andrew K. Wong, Edward D. Verdonk, Samuel A. Wickline, James G. Miller ... data detailing the ultrasonic anisotropy of cardiac muscle and delineating the shift in myofiber orientation from epicardium to endocardium.26 Histologic studies by Streeter et al. ...
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2015
Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused... more 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.
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology, 2002
ABSTRACT A previous study has shown that the cross-sectional area of the left ventricular cavity ... more ABSTRACT A previous study has shown that the cross-sectional area of the left ventricular cavity (LV) increases immediately after defibrillation, suggesting that the defibrillation shock may cause relaxation. Since a single area slice may not reflect the entire myocardium, we wanted to test the relaxation hypothesis by evaluating volume. Ten to twenty defibrillation shocks were delivered in each of six dogs. A catheter was placed in the LV to measure intraventricular volume (IVV). Ultrasound images of the LV were recorded simultaneously with IVV. LV cavity area increased 13% (p
The Journal of the Acoustical Society of America, 2015
Ultrasonic backscatter techniques are being developed to diagnose osteoporosis. Tissues that lie ... more 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 d...
The Journal of the Acoustical Society of America, 2015
Ultrasonic backscatter techniques are being developed to diagnose osteoporosis. Tissues that lie ... more 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.
Backscatter difference measurements may be used to detect changes in bone caused by osteoporosis.... more Backscatter difference measurements may be used to detect changes in bone caused by osteoporosis. The backscatter difference technique measures the power difference between two portions of an ultrasonic backscatter signal. The goal of this study is to evaluate the feasibility of using an ultrasonic imaging system to perform backscatter difference measurements of bone. Ultrasonic images and backscatter signals were acquired from 24 specimens of human cancellous bone. The signals were analyzed in the frequency domain to determine the normalized mean backscatter difference (nMBD) and in the time domain to determine the normalized backscatter amplitude ratio (nBAR). The images were analyzed to determine the normalized pixel value difference (nPVD), which measures the difference in average pixel brightness between regions of interest placed at two different depths in the image. All three parameters were found to increase with bone mineral density. The signal-based parameters, nMBD and nB...
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology, 2002
ABSTRACT Medical equipment can unintentionally allow the flow of power line current through the p... more ABSTRACT Medical equipment can unintentionally allow the flow of power line current through the patient causing complete hemodynamic collapse without fibrillation. This study tests the hypothesis that static wall thickening accompanies AC induced collapse via an isovolumic state. In 3 dogs, we delivered AC current stimulation ranging from 10-160 Hz and 10-1000 μA to the right ventricle. A steerable, quadripolar catheter was placed in the apex of the left ventricle and deflected towards the basal region to measure left ventricular volume. Two dimensional, short-axis ultrasound images of the LV endocardial walls were recorded to measure wall thickness. Our results indicate that wall thickness during collapse is significantly greater than during systole (Δ thickness =11.7±12 mm, p
Medical equipment can unintentionally allow the flow of small amounts of AC current through the p... more Medical equipment can unintentionally allow the flow of small amounts of AC current through the patient causing hemodynamic collapse without fibrillation. This study examines the mechanical response of the left ventricle during AC induced hemodynamic collapse. Six dogs received 5 seconds of AC current stimulation ranging from 4-160 Hz and 10-1000 μA to the right ventricle. A quadripolar catheter was placed in the apex of the left ventricle to measure left ventricular volume. Short-axis ultrasound images were recorded to measure left ventricular cross sectional area and wall thickness. Our results showed that the mean volume of the left ventricle during collapse was significantly smaller (p < 0.05) than the mean volume preceding collapse. Cross sectional area also decreased significantly and wall thickness increased. This suggests that the heart assumes a contracted, systole-like state during collapse.
American journal of physiology. Heart and circulatory physiology, 2003
A previous two-dimensional (2D) ultrasound study suggested that there is relaxation of the myocar... more A previous two-dimensional (2D) ultrasound study suggested that there is relaxation of the myocardium after defibrillation. The 2D study could not measure activity occurring within the first 33 ms after the shock, a period that may be critical for discriminating between shock- and excitation-induced relaxation. The objective of our study was to determine the left ventricular (LV) geometry during the first 33 ms after defibrillation. Biphasic defibrillation shocks were delivered 5-50 s after the induction of ventricular fibrillation in each of the seven dogs. One-dimensional, short-axis ultrasound images of the LV cavity were acquired at a rate of 250 samples/s. The LV cavity diameter was computed from 32 ms before to 32 ms after the shock. Preshock and postshock percent changes in LV diameter were analyzed as a function of time with the use of regression analysis. The normalized mean pre- and postshock slopes (0.2 +/- 2.2 and 3.3 +/- 7.9% per 10 ms) were significantly different (P &...
A number of investigators have performed in vitro measurements of cancellous bone to determine ho... more A number of investigators have performed in vitro measurements of cancellous bone to determine how various ultrasonic parameters depend on bone density and trabecular orientation. To facilitate handling and storage of bone specimens, the marrow is often removed prior to ultrasonic measurements. However, the assumption that marrow does not affect ultrasonic measurements at high frequencies (>1 MHz) has not been tested. The goal of this study is to determine the effect of marrow on the ultrasonic properties of bovine cancellous bone at frequencies greater than 1 MHz. Twelve specimens of cancellous bone were obtained from the proximal end of four bovine tibia. Ultrasonic measurements consisting of normalized broadband ultrasonic attenuation (nBUA), speed of sound (SOS) and apparent integrated backscatter (AIB) were measured in each specimen using 2.25 MHz (centre frequency) broadband ultrasonic pulses. These measurements were performed before and after marrow removal either along th...
2009 IEEE International Ultrasonics Symposium, 2009
Ultrasound backscatter has the potential to provide information useful for the diagnosis and moni... more Ultrasound backscatter has the potential to provide information useful for the diagnosis and monitoring of bone disorders (e.g., osteopenia, osteoporosis, and hard tissue sarcomas). We hypothesize that the Renyi entropy, previously shown to be sensitive to subtle changes in scattering from soft tissues, may also offer some utility in characterizing properties of bone. The goals of the present work were to investigate and compare the ability of energy- and entropy-based analyses of radio-frequency ultrasonic backscatter, to assess material properties of cancellous bone with respect to conventional quantitative computed X-ray tomography (QCT).
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Papers by Brent Hoffmeister