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Acoustic properties of bone
ABSTRACTS, ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION SYMPOSIUM
Experimental results in the measured samples (pure water, saline solutions, plasma crystal solutions, human blood diluted with physiological saline and pure blood) have been obtained. These studies show that the velocity is related to the electrolytic composition and protein content of the samples and that the velocity in blood is higher than the value usually accepted for diagnostic purposes. Babcock ACOUSTIC PROPERTIES OF BONE, Baxter J. Garcia, Lynchburg Research Center, Lynchburg, VA 24505
and Wilcox
Company,
Research was undertaken to investigate the potential of ultrasonic techniques in non-invasive clinical characterization of bone tissue. Ultrasonic determination of the elastic constants of bone was investigated both theoretically and experimentally. Elastic constants were derived from experimental measurements of longitudinal and shear wave velocities by critical angle and pulse transmission methods. Results of critical angle measurements were compared with theoretical predictions based on classical The relation of ultrasonic velocity to two aspects of elasticity theory. bone composition, anisotropy and mineral content, was investigated. Ultrasonic velocity was found to differ by 30 percent in the cross-grain and along-grain directions. The bulk modulus of bone was found to be a sensitive function of bone density; e.g., a change in bone density of 10 percent was accompanied by a change in modulus of 60 percent. Ultrasonic attenuation in bovine and human bone was measured in the frequency range 2 to 0 MHz. Typical values of the attenuation coefficient are 12 dB/cm and 30 dB/cm at 2.0 and 8.0 MHz, respectively, with an approximately linear variation with frequency. The dependence of the attenuation coefficient on state of preservation of the tissue, and on bone mineral content was investigated. State of preservation appeared to have little effect on measured values of the attenuation coefficient. No significant change in the attenuationfrequency curve was observed until bone density had been reduced by more than 15 percent. Very high attenuation values, e.g., 40 dB/cm at 2.0 MHz Highest were observed in several samples of formalin-fixed human bone. It was concluded values occurred in a pathological (osteoporotic) sample. that ultrasonic methods show promise in non-invasive clinical diagnosis of bone pathology and that further research into these techniques is justified. ANISOTROPIC TEMPERATURE DEPENDENCE OF THE ULTRASONIC VELOCITIES IN BONE, Hyo Sub Yoon and J. Lawrence Katz, Center for Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, hY 12181 In our previous ultrasonic studies of bone, we have determined the material symmetry of bone, which is found to be consistent with the hexagonal system, and have measured the ultrasonic velocities as a function of frequency (l-10 MHz) along the eight unique orientations in a femoral bone specimen. Since bone has been shown to be viscoelastic even at ultrasonic frequencies, frequency and temperature dependence of the ultrasonic velocities in bone are closely related to each other, e.g., by the time-temperature equivalence due to large attenuation of ultrasound in bone above principle. However, 10 MHz, it is difficult to investigate frequency dependence of the ultrasonic velocities in this range especially by either pulse-through-transmission or A right-angle reflector technique is very attractive pulse-echo techniques. for this purpose because it is based on the critical angle reflection in a liquid/ solid boundary rather than the direct transmission, of an ultrasonic beam. In this investigation, the ultrasonic velocities have been measured both along the perpendicular to the long bone axis in the bovine femur as a function of temperature in the range 20 to 80 OC. Bone specimens have been prepared by the usual metallographic techniques, cutting with a low speed diamond saw and grinding on silicon carbide strips (240, 320, 400 and 600 grit). This work was supported in part by the Whitaker Foundation and in part by USPHSthrough NIDR Grant No. 5Tl-DE-117-15. SESSION8:
A-SCAN ANALYSIS II
ULTRASONICECHOIMAGING WITH PSEUDO-RANDOM AND PULSEDSOURCES: A COMPARATIVE STUDY, D. Nahamooand A. C. Kak, School of Electrical Engineering, Purdue University, West Lafayette, IN 47907
184
Experimental results in the measured samples (pure water, saline solutions, plasma crystal solutions, human blood diluted with physiological saline and pure blood) have been obtained. These studies show that the velocity is related to the electrolytic composition and protein content of the samples and that the velocity in blood is higher than the value usually accepted for diagnostic purposes. Babcock ACOUSTIC PROPERTIES OF BONE, Baxter J. Garcia, Lynchburg Research Center, Lynchburg, VA 24505
and Wilcox
Company,
Research was undertaken to investigate the potential of ultrasonic techniques in non-invasive clinical characterization of bone tissue. Ultrasonic determination of the elastic constants of bone was investigated both theoretically and experimentally. Elastic constants were derived from experimental measurements of longitudinal and shear wave velocities by critical angle and pulse transmission methods. Results of critical angle measurements were compared with theoretical predictions based on classical The relation of ultrasonic velocity to two aspects of elasticity theory. bone composition, anisotropy and mineral content, was investigated. Ultrasonic velocity was found to differ by 30 percent in the cross-grain and along-grain directions. The bulk modulus of bone was found to be a sensitive function of bone density; e.g., a change in bone density of 10 percent was accompanied by a change in modulus of 60 percent. Ultrasonic attenuation in bovine and human bone was measured in the frequency range 2 to 0 MHz. Typical values of the attenuation coefficient are 12 dB/cm and 30 dB/cm at 2.0 and 8.0 MHz, respectively, with an approximately linear variation with frequency. The dependence of the attenuation coefficient on state of preservation of the tissue, and on bone mineral content was investigated. State of preservation appeared to have little effect on measured values of the attenuation coefficient. No significant change in the attenuationfrequency curve was observed until bone density had been reduced by more than 15 percent. Very high attenuation values, e.g., 40 dB/cm at 2.0 MHz Highest were observed in several samples of formalin-fixed human bone. It was concluded values occurred in a pathological (osteoporotic) sample. that ultrasonic methods show promise in non-invasive clinical diagnosis of bone pathology and that further research into these techniques is justified. ANISOTROPIC TEMPERATURE DEPENDENCE OF THE ULTRASONIC VELOCITIES IN BONE, Hyo Sub Yoon and J. Lawrence Katz, Center for Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, hY 12181 In our previous ultrasonic studies of bone, we have determined the material symmetry of bone, which is found to be consistent with the hexagonal system, and have measured the ultrasonic velocities as a function of frequency (l-10 MHz) along the eight unique orientations in a femoral bone specimen. Since bone has been shown to be viscoelastic even at ultrasonic frequencies, frequency and temperature dependence of the ultrasonic velocities in bone are closely related to each other, e.g., by the time-temperature equivalence due to large attenuation of ultrasound in bone above principle. However, 10 MHz, it is difficult to investigate frequency dependence of the ultrasonic velocities in this range especially by either pulse-through-transmission or A right-angle reflector technique is very attractive pulse-echo techniques. for this purpose because it is based on the critical angle reflection in a liquid/ solid boundary rather than the direct transmission, of an ultrasonic beam. In this investigation, the ultrasonic velocities have been measured both along the perpendicular to the long bone axis in the bovine femur as a function of temperature in the range 20 to 80 OC. Bone specimens have been prepared by the usual metallographic techniques, cutting with a low speed diamond saw and grinding on silicon carbide strips (240, 320, 400 and 600 grit). This work was supported in part by the Whitaker Foundation and in part by USPHSthrough NIDR Grant No. 5Tl-DE-117-15. SESSION8:
A-SCAN ANALYSIS II
ULTRASONICECHOIMAGING WITH PSEUDO-RANDOM AND PULSEDSOURCES: A COMPARATIVE STUDY, D. Nahamooand A. C. Kak, School of Electrical Engineering, Purdue University, West Lafayette, IN 47907
184