In vivo ultrasonic attenuation slope estimates for detecting cervical ripening in rats: Preliminary results

Department of Electrical Engineering, University of North Dakota, Box 7165, Grand Forks, North Dakota 58202, USA.
The Journal of the Acoustical Society of America (Impact Factor: 1.5). 04/2008; 123(3):1794-800. DOI: 10.1121/1.2832317
Source: PubMed


To effectively postpone preterm birth, cervical ripening needs to be detected and delayed. As the cervix ripens, the spacing between the collagen fibers increases and fills with water, hyaluronan, decorin, and enzymes suggesting that the ultrasonic attenuation of the cervix should decrease. The decrease in ultrasonic attenuation may be detectable, leading to an effective means of detecting cervical ripening. Herein, the traditional attenuation slope-estimation algorithm based on measuring the downshift in center frequency of the ultrasonic backscattered signal with propagation depth was modified and applied to the cervix of rats. The modified algorithm was verified using computer simulations and an ex vivo tissue sample before being evaluated in in vivo animal studies. Spherically-focused f/3 transducers with 33-MHz center frequencies and with 9-mm focal lengths were used in both the simulations and experiments. The accuracy was better than 15% in the simulations, and the attenuation slope of the cervix in the ex vivo experiment was 2.6+/-0.6 dB/cm-MHz, which is comparable to 2.5+/-0.4 dB/cm-MHz measured using a through-transmission insertion loss technique. For the in vivo experiments, a statistically significant effect of ultrasonic attenuation with gestational age was not observed. The large variances in the in vivo results were most likely due to the natural variation in attenuation for biological tissue between animals.

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    • "Ultrasonic attenuation can be used to detect these microstructural changes in cervix as attenuation is related to tissue stiffness, collagen and water concentration of tissues[5], [6], [7], [8], [9]. Our previous studies in both animals and humans have shown that ultrasonic attenuation relates with collagen remodeling of the cervix, gestation age of pregnancy and time to delivery[10], [11], [12], [13]. The aim of this study is to see if preterm cases can be properly identified. "
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    ABSTRACT: One to five transvaginal ultrasound scans were taken of 63 women to estimate the microstructural changes in cervix using ultrasonic attenuation. Spectral log difference algorithm showed a clear decrease in attenuation as the time to delivery comes closer. The decrease in attenuation occurs earlier in preterm birth compared to full term birth which can be used as a predictor for preterm birth. Attenuation estimate did not improve as the ROI size increased.
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    • "also, the evaluation of bone strength requires not only the knowledge of its density but also of its microscopic structure. The analysis of ultrasonic echoes scattered by soft tissues has been successfully applied for tissue characterization [9], [10]. similarly, the trabecular bone backscatter contains information about the properties of the bone structure. "
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    ABSTRACT: A dedicated ultrasonic scanner for acquiring RF echoes backscattered from the trabecular bone was developed. The design of device is based on the goal of minimizing of custom electronics and computations executed solely on the main computer processor and the graphics card. The electronic encoder-digitizer module executing all of the transmission and reception functions is based on a single low-cost field programmable gate array (FPGA). The scanner is equipped with a mechanical sector-scan probe with a concave transducer with 50 mm focal length, center frequency of 1.5 MHz and 60% bandwidth at -6 dB. The example of femoral neck bone examination shows that the scanner can provide ultrasonic data from deeply located bones with the ultrasound penetrating the trabecular bone up to a depth of 20 mm. It is also shown that the RF echo data acquired with the scanner allow for the estimation of attenuation coefficient and frequency dependence of backscattering coefficient of trabecular bone. The values of the calculated parameters are in the range of corresponding in vitro data from the literature but their variation is relatively high.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 07/2012; 59(7):1470-7. DOI:10.1109/TUFFC.2012.2347 · 1.51 Impact Factor
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    • "The spectral difference method, the spectral log difference method, and the hybrid method have all been used for estimating the attenuation in liver, kidney, cervix, rat tumors, etc. (Kuc and Schwartz, 1979; Kuc, 1980; Hall et al., 1996; Oelze et al., 2002; McFarlin et al., 2006; Bigelow et al., 2008). The accuracy and the precision of these methods are strongly dependent on the ROI size (the number of independent echoes laterally and the number of pulse lengths axially) and on the level of homogeneity within the ROI. "
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    ABSTRACT: Accurate characterization of tissue pathologies using ultrasonic attenuation is strongly dependent on the accuracy of the algorithm that is used to obtain the attenuation coefficient estimates. In this paper, computer simulations were used to compare the accuracy and the precision of the three methods that are commonly used to estimate the local ultrasonic attenuation within a region of interest (ROI) in tissue; namely, the spectral log difference method, the spectral difference method, and the hybrid method. The effects of the inhomgeneities within the ROI on the accuracy of the three algorithms were studied, and the optimal ROI size (the number of independent echoes laterally and the number of pulse lengths axially) was quantified for each method. The three algorithms were tested for when the ROI was homogeneous, the ROI had variations in scatterer number density, and the ROI had variations in effective scatterer size. The results showed that when the ROI was homogeneous, the spectral difference method had the highest accuracy and precision followed by the spectral log difference method and the hybrid method, respectively. Also, when the scatterer number density varied, the spectral difference method completely failed, while the log difference method and hybrid method still gave good results. Lastly, when the scatterer size varied, all of the methods failed.
    The Journal of the Acoustical Society of America 04/2011; 129(4):2316-24. DOI:10.1121/1.3559677 · 1.50 Impact Factor
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