ABSTRACT: A study has been made of the application of radio frequency (RF) ultrasound to the detection of muscular dystrophy by monitoring passively stretched skeletal muscle. The tests included detection of integrated backscatter changes in response to both static loading, in which muscle samples were stretched and allowed to relax, and stress relaxation. In both static and step strain loading conditions, the dystrophic muscle was found to exhibit little change in backscatter power while normal muscle responded to loading with significant changes in integrated backscatter. The backscatter response is compared with mechanical properties of the tissue (time constants and stress-strain constants). Both mechanical and ultrasonic time constants of relaxation are not significantly different between normal and dystrophic tissue, but stress-strain constants do differ. The difference in response of dystrophic and normal tissue appears to be due to a repression of motion of the constituent anatomy of dystrophic muscle which is responsible for the change of echogenicity with passive stretch.
Ultrasound in Medicine & Biology 02/1995; 21(3):343-52. · 2.29 Impact Factor
ABSTRACT: Quantitating regional myocardial perfusion has been the much sought-after but still elusive goal of many intensive investigations over the years. Videodensitometry of the variation of myocardial echogenicity in two-dimensional (2-D) echocardiograms as a function of time in conjunction with the injection of a bolus of an ultrasound contrast agent has been used clinically as a tool for a direct assessment of regional myocardial perfusion, despite that the precise relationship between tissue echogenicity observed on an image and the echoes detected by the ultrasonic probe is unknown. A study was undertaken to determine whether ultrasonic backscatter calculated from unprocessed radio frequency (RF) echoes returned from myocardium could be used to quantitate regional myocardium perfusion. A real-time ultrasonic scanner has been modified and interfaced to a microcomputer to acquire RF data at a rate up to 10 frames per second. Preliminary experimental data were obtained from four open-chest dogs following intracoronary injection of a bolus of Albunex and two dogs following intravenous injection with this modified scanner. On one hand, these results indicate that the integrated backscatter measured from the region of myocardium perfused by the coronary artery where Albunex is injected and selected for monitoring initially increases, reaches a peak, and then decreases as the contrast agent is washed out and that the magnitude of the peak is approximately linearly proportional to the volume concentration of Albunex microspheres injected, clearly demonstrating the feasibility of this approach for quantitating region myocardial perfusion. On the other hand, intravenous injections did not result in any appreciable change in myocardial backscatter in the left ventricle although a response could be observed in the left ventricular blood pool.
Ultrasound in Medicine & Biology 02/1993; 19(3):181-91. · 2.29 Impact Factor
ABSTRACT: The purpose of this work was to explore the mechanisms which are responsible for the scattering of ultrasound from skeletal muscle tissue. It was undertaken in response to an interesting phenomenon observed in the authors' laboratory whereby scattering power from avian skeletal muscle changed in concordance with passive stretch. Ultrasonic scattering from skeletal muscle samples was measured as they were stretched passively in increments of 10% of their original length up to 40%. The samples were illuminated with an ultrasound beam from a transducer which was oriented orthogonally to and at 20 degrees from the normal to the long axis of the muscle sample. It was found that the integrated backscatter increased significantly over the strain range for the orthogonal orientation, but it changed very little after the initial stretch when the orientation was 20 degrees . It is postulated that this phenomenon may be caused by reorientation of the endomysial collagen fibers surrounding each muscle fiber.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 02/1993; 40(4):354-65. · 1.69 Impact Factor
ABSTRACT: A study has been made of the application of RF ultrasound to the
detection of muscular dystrophy by monitoring passively stretched
skeletal muscle. Normal and dystrophic male chickens were raised to the
age of ten months. The animals were decapitated and the pectoral muscles
were dissected and cut into strips approximately 3 cm in length. The
muscle samples were stretched in 2 mm increments up to 8 mm. Ultrasound
measurements were made at each stretch increment using an Aloka 280SL
scanner which has been modified to allow digitization of the RF signal.
The baseline values of integrated backscatter found were
-25.2±2.4 dB for normal muscle and -20.3±1.6 dB for
dystrophic muscle. A linear fit of integrated backscatter versus strain
yielded a mean slope difference of 8.5±0.7 dB/cm/cm for normal
tissue versus -1.3±0.3 dB/cm/cm for dystrophic issue
Ultrasonics Symposium, 1991. Proceedings., IEEE 1991; 01/1992
ABSTRACT: Traditional methods for measuring acoustic speed require knowledge of either the specimen thickness or the distances between the transducers and the specimen. In general, the accuracy in measuring these quantities determines the accuracy of the experimental technique for measuring speed. This problem is particularly acute in measuring sound speed in biological specimens. A new method for measuring acoustic speed of materials, which eliminates the need for determining these quantities, has been developed. The technique, which necessitates the use of only one transducer, requires measurement of four times of flight of a sound pulse and the knowledge of the speed of sound in a reference fluid medium in which the specimen is placed. Ultrasonic speed in stainless steel and Plexiglas was measured using this method to verify its validity. Results on measurements on porcine liver, myocardium, and soft fat are also reported.
The Journal of the Acoustical Society of America 11/1990; 88(4):1679-82. · 1.55 Impact Factor
ABSTRACT: Cardiac transplant rejection was evaluated using ultrasound
integrated backscatter (IB). Six adult goats received modified Mann
cervical heterotopic cardiac transplants with no administration of
immunosuppressive pharmacology. A-line ultrasonic backscatter from the
left ventricle was collected daily for each animal until the graft
ceased to yield electrical activity. Integrated backscatter with a
4-8-MHz bandwidth was calculated for each day. No biopsies were taken.
Although no consistent day-to-day trend is noted, four of six goats show
a decrease in backscatter over the rejection episode. In all cases, the
IB increased the first two to three days after the transplant and
subsequently decreased in varying magnitudes and at varying durations
Bioengineering Conference, 1990., Proceedings of the 1990 Sixteenth Annual Northeast; 04/1990