Ultrasonic Characterization of Canine Myocardium Contraction
ABSTRACT Absfracf-Other investigators have found ultrasonic backscatter from canine myocardium to exhibit a significant variation throughout the cardiac cycle. Also, several studies have shown a change in an ultrasonic property of canine myocardium when ischemia is induced. In an attempt to gain some understanding of the physical mechanisms responsible for these variations, several ultrasonic measurements were made on canine papillary muscle in vitro during both isotonic (constant load) and isometric (constant length) contractions. Integrated backscatter was found to exhibit a significant cyclic variation (p < 0.05) during isotonic (constant load) contractions, but not during isometric (constant length) contractions. This result suggests that the variation in the physical arrangement of structures within the tissue that occurs during contraction plays an important role in determining ultrasonic backscatter. No significant cyclic variation was found in the backscattered signal envelope statistics or in acoustic attenuation during either isotonic or isometric contractions.
- SourceAvailable from: mit.edu
[Show abstract] [Hide abstract]
- "Support for stochastic modeling also comes from the fact that the US images of soft tissues have a random texture pattern termed speckle, similar to the appearance of a rough surface irradiated by a coherent laser source. In prior works, the first order statistics of the amplitude of backscattered signals from several tissues, such as the liver (Sommer et al. 1987), heart (Wear et al. 1986), breast (Shankar et al. 2001), eye (Romijn et al. 1991), and kidney (Wear et al. 1997), have been studied. Our previous studies on healthy skin tissues showed that the K, Weibull and generalized gamma (GG) distributions were able to model the envelope pdfs well (Raju and Srinivasan 2002). "
ABSTRACT: Quantitative ultrasonic methods were studied for characterizing skin lesions in vivo using contact dermatitis as an example. The parameters studied include skin thickness, echogenicity, attenuation coefficient slope and parameters related to echo statistics (signal-to-noise ratio and shape parameters of Weibull, K and generalized gamma distributions). Data were collected using a high-frequency ultrasound (US) system (center frequency = 33 MHz). To compensate for depth-dependent diffraction effects, correction curves as a function of the distance between the transducer and the tissue were first empirically obtained. Diffraction-corrected quantitative parameters were then compared between healthy and affected skin of volunteers, who underwent patch testing for allergic and irritant contact dermatitis. A significant increase in skin thickness, decrease in echogenicity of the upper dermis and decrease in attenuation coefficient slope were found at the affected sites compared to those of healthy skin. However, no differences in parameters related to the echo statistics of the mid-dermis were found. These results indicate that a combination of quantitative ultrasonic parameters have the potential for extracting information for characterizing skin conditions.Ultrasound in Medicine & Biology 07/2003; 29(6):825-38. DOI:10.1016/S0301-5629(03)00009-7 · 2.21 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: This paper studies the absolute myocardial backscatter as a function of the frequency and phase of the cardiac cycle. This was achieved by calibration of the ultrasonic instrumentation and the random diffraction process. We have discovered a first-order model in which the scattering from the myocardium is Rayleigh scattering with a cardiac cycle variation in the scattering cross section. Furthermore, the statistics are approximately those of a radio frequency waveform with two independent Gaussian components (Rayleigh envelope). Deviations from the first-order model suggest measurable fine structure related to myocardial ultrastructure. This model has profound effects on the choice of optimal radiation patterns and signal processing schemes for preparing diagnostic parameters (e.g., integrated backscatter).Ultrasonic Imaging 05/1986; 8(2):107-20. DOI:10.1016/0161-7346(86)90003-9 · 0.91 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The temporal correlation properties of ultrasonic echoes from contracting myocardium are investigated theoretically. Myocar- dium is modeled as a dense suspension of moving particles, with time- varying scattering amplitudes. Single scattering is assumed. Echoes from different particles are added coherently. The variance of particle velocity is proposed as an indicator of contractile performance. It is shown how this parameter may be extracted from the average corre- lation of pairs of echoes arising from separate ultrasound pulses. An experiment is performed in which a manufactured target with known motion characteristics is interrogated using a commercial medical ul- trasound scanner. The experimental results are found to be in good agreement with theory. Finally, practical considerations for perform- ing and interpreting these measurements in human myocardium are discussed. EVERAL INVESTIGATIONS have demonstrated that it may be possible to evaluate cardiac contractile per- formance accurately with ultrasound. One technique in- volves the measurement of the frequency average of the intensity of ultrasonic echoes emanating from myocar- dium. Echo intensity has been found to vary throughout the cardiac cycle in normal canine myocardium, with the maximum level occurring at end-diastole and the mini- mum at end-systole ( l), (2). In addition, the magnitude of this effect has a regional dependence throughout the heart, with areas of greater contractile activity exhibiting greater amplitudes of variation (3). The extent of the cyclic variation of echo intensity has also been observed to drop significantly in canine myocardium making a tran- sition from normal to ischemic 141. Thus the magnitude of cyclic variation may be interpreted as a measure of contractile performance. A second technique entails quantitative analysis of video images of the heart produced by ultrasound scan-IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 02/1987; 34(3):368-75. DOI:10.1109/T-UFFC.1987.26955 · 1.51 Impact Factor