作為超音波於醫學診斷的應用，超音波彈性影像常被用來觀察組織病變所伴隨的彈性改變，或偵測組織內部的腫瘤。在超音波彈性影像技術中，剪力波頻散超音波振動成像方法(Shearwave Dispersion Ultrasound Vibrometry, SDUV)為組織的黏彈性提供了一個定量的測量。為了評估SDUV方法對偵測組織黏彈性差異的敏感度，並探討溫度效應對組織黏彈性的影響，本研究首先利用機械震盪器產生剪力波並於假體實驗中驗證其可行性，接著以兩層吉利丁濃度分別為3%與9%的假體測試SDUV方法的辨識能力。最後以離體豬肝進行25到40度之間的黏彈性檢測。本研究產生頻率為50 到300 Hz的剪力波，並使用中心頻率為30 MHz的超音波探頭接收回波。假體實驗結果證明使用震盪器可產生振幅約為50 μm的剪力波，有助於減少量測時的誤差；兩層假體實驗證實SDUV方法能區分5 mm內的組織黏彈性差異；離體實驗結果顯示，從25度加熱到40度時，豬肝的黏彈性從μ1 =3.635±0.25 kPa與 μ2 =2.016±0.21 Pa•s下降至μ1 =2.016±0.21 kPa與μ2=0.93±0.18 Pa•s，且為線性變化。總結而言，本研究證實了SDUV方法有診斷組織內部黏彈性差異的潛力，並且軟組織的黏彈性特性因溫度效應的影響而改變。

As an application of ultrasound in medical diagnostic, ultrasound elasticity imaging is used to observe changes in tissue elasticity associated lesions or tumors detected within the tissue. In these technologies, Shearwave Dispersion Ultrasound Vibrometry (SDUV) provides a quantitative measurement for tissue viscoelasticity. In order to evaluate the sensitivity of SDUV method on detecting viscoelastic differences in the organization and to explore the effects of temperature effect on tissue viscoelasticity, this study using a mechanical vibrator to generate shear wave and verify its feasibility in phantom experiments, followed by two-layer phantom experiments with gelatin concentrations of 3% and 9% to test the identifying ability of SDUV method. Finally, the viscoelasticity of in vitro porcine liver was measured between 25-40 degrees. Shear waves with frequency of 50 to 300 Hz were detected by a 30 MHz ultrasound transducer. The verification results prove that the use of mechanical vibrator can produce shear waves with amplitude of about 50 μm, helps to reduce measurement error; two-layer phantom experiments confirmed SDUV method can distinguish differences in tissue viscoelasticity within 5 mm; in vitro results show that the viscoelasticity of porcine liver linearly changed from μ1 =3.635±0.25 kPa and μ2 =2.016±0.21 Pa•s down to μ1=2.016±0.21 kPa and μ2=0.93±0.18 Pa•s while heating. In conclusion, this study confirms the potential of SDUV method to diagnose viscoelasticity differences within the tissue; furthermore, the viscoelastic properties of the soft tissue changes due to temperature effect.

[1] K. K. Shung, "Diagnostic Ultrasound: Imaging and Blood Flow Measurements," 2006.
[2] J.-W. H. Korstanje, R. W. Selles, H. J. Stam, S. E. R. Hovius, and J. G. Bosch, "Development and validation of ultrasound speckle tracking to quantify tendon displacement," Journal of Biomechanics, vol. 43, pp. 1373-1379, 2010.
[3] Y. Yoshii, H. R. Villarraga, J. Henderson, C. Zhao, K.-N. An, and P. C. Amadio, "Speckle Tracking Ultrasound for Assessment of the Relative Motion of Flexor Tendon and Subsynovial Connective Tissue in the Human Carpal Tunnel," Ultrasound in Medicine & Biology, vol. 35, pp. 1973-1981, 2009.
[4] J. Ophir, I. Céspedes, H. Ponnekanti, Y. Yazdi, and X. Li, "Elastography: A quantitative method for imaging the elasticity of biological tissues," Ultrasonic Imaging, vol. 13, pp. 111-134, 1991.
[5] T.-M. Mak, Y.-P. Huang, and Y.-P. Zheng, "Liver Fibrosis Assessment Using Transient Elastography Guided with Real-Time B-mode Ultrasound Imaging: A Feasibility Study," Ultrasound in Medicine & Biology, vol. 39, pp. 956-966, 2013.
[6] R. C. Molthen, P. M. Shankar, and J. M. Reid, "Characterization of ultrasonic B-scans using non-rayleigh statistics," Ultrasound in Medicine & Biology, vol. 21, pp. 161-170, 1995.
[7] S. W. Smith, H. Lopez, and W. J. Bodine Jr, "Frequency independent ultrasound contrast-detail analysis," Ultrasound in Medicine and Biology, vol. 11, pp. 467-477, 1985.
[8] R. F. Wagner, M. F. Insana, and D. G. Brown, "Statistical properties of radio-frequency and envelope-detected signals with applications to medical ultrasound," Journal of the Optical Society of America A, vol. 4, pp. 910-922, 1987.
[9] I. Cespedes and J. Ophir, "Reduction of Image Noise in Elastography," Ultrasonic Imaging, vol. 15, pp. 89-102, 1993.
[10] J. Ophir, F. Kallel, T. Varghese, M. Bertrand, I. Cespedes, and H. Ponnekanti, "Elastography: a systems approach," Int. J. Imaging Syst. Technol., vol. 8, p. 89, 1997.
[11] S. Y. Emelianov, M. A. Lubinski, W. F. Weitzel, R. C. Wiggins, A. R. Skovoroda, and M. O'Donnell, "Elasticity imaging for early detection of renal pathology," Ultrasound in Medicine & Biology, vol. 21, pp. 871-883, 1995.
[12] B. F. Kennedy, T. R. Hillman, R. A. McLaughlin, B. C. Quirk, and D. D. Sampson, "In vivo dynamic optical coherence elastography using a ring actuator," Opt. Express, vol. 17, p. 21762, 2009.
[13] B. J. Fahey, R. C. Nelson, S. J. Hsu, D. P. Bradway, D. M. Dumont, and G. E. Trahey, "In Vivo Guidance and Assessment of Liver Radio-Frequency Ablation with Acoustic Radiation Force Elastography," Ultrasound in Medicine & Biology, vol. 34, p. 1590, 2008.
[14] S. F. Levinson, M. Shinagawa, and T. Sato, "Sonoelastic determination of human skeletal muscle elasticity," J. Biomech., vol. 28, p. 1145, 1995.
[15] L. Gao, K. J. Parker, S. K. Alam, and R. M. Lernel, "Sonoelasticity imaging: theory and experimental verification," J. Acoust. Soc. Am., vol. 97, p. 3875, 1995.
[16] K. Nightingale, M. S. Soo, R. Nightingale, and G. Trahey, "Acoustic radiation force impulse imaging: in vivo demonstration of clinical feasibility," Ultrasound in Medicine & Biology, vol. 28, pp. 227-235, 2002.
[17] L. Sandrin, B. Fourquet, J. M. Hasquenoph, S. Yon, C. Fournier, F. Mal, et al., "Transient elastography: a new noninvasive method for assessment of hepatic fibrosis," Ultrasound Med Biol, vol. 29, pp. 1705-13, 2003.
[18] L. Sandrin, S. Catheline, M. Tanter, X. Hennequin, and M. Fink, "Time-Resolved Pulsed Elastography with Ultrafast Ultrasonic Imaging," Ultrasonic Imaging, vol. 21, pp. 259-272, 1999.
[19] S. Chen, M. Fatemi, and J. F. Greenleaf, "Quantifying elasticity and viscosity from measurement of shear wave speed dispersion," J Acoust Soc Am, vol. 115, pp. 2781-5, 2004.
[20] C. Shigao, M. W. Urban, C. Pislaru, R. Kinnick, Z. Yi, Y. Aiping, et al., "Shearwave dispersion ultrasound vibrometry (SDUV) for measuring tissue elasticity and viscosity," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 56, pp. 55-62, 2009.
[21] M. W. Urban, S. Chen, and M. Fatemi, "A Review of Shearwave Dispersion Ultrasound Vibrometry (SDUV) and its Applications," Curr Med Imaging Rev, vol. 8, pp. 27-36, 2012.
[22] J. Bercoff, M. Muller, M. Tanter, and M. Fink, "Study of viscous and elastic properties of soft tissues using supersonic shear imaging," in Ultrasonics, 2003 IEEE Symposium on, 2003, pp. 925-928 Vol.1.
[23] J. Bercoff, M. Tanter, and M. Fink, "Supersonic shear imaging: a new technique for soft tissue elasticity mapping," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 51, pp. 396-409, 2004.
[24] S. N. Goldberg, "Radiofrequency tumor ablation: principles and techniques," European Journal of Ultrasound, vol. 13, pp. 129-147, 2001.
[25] Y. C. Fung, "Biomechanics : Mechanical Properties of Living Tissues," Springer-Verlag, 1993.
[26] C. A. Carrascal, "Measurement of kidney viscoelasticity with shearwave dispersion ultrasound vibrometry," 2011.
[27] W. N. Findley, J. S. Lai, and K. Onaran, "Creep and relaxation of nonlinear viscoelastic materials: with an introduction to linear viscoelasticity," Dover, 1989.
[28] Y. Yamakoshi, J. Sato, and T. Sato, "Ultrasonic imaging of internal vibration of soft tissue under forced vibration," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 37, pp. 45-53, 1990.
[29] J. R. Doherty, G. E. Trahey, K. R. Nightingale, and M. L. Palmeri, "Acoustic radiation force elasticity imaging in diagnostic ultrasound," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 60, pp. 685-701, 2013.
[30] Z. Yi, C. Shigao, Z. Xiaoming, and J. F. Greenleaf, "Detection of shear wave propagation in an artery using pulse echo ultrasound and Kalman filtering," in Ultrasonics Symposium, 2004 IEEE, 2004, pp. 1251-1253 Vol.2.
[31] H. Hasegawa and H. Kanai, "Improving accuracy in estimation of artery-wall displacement by referring to center frequency of RF echo," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 53, pp. 52-63, 2006.
[32] Z. Yi, C. Shigao, T. Wei, and J. F. Greenleaf, "Kalman filter motion detection for vibro-acoustography using pulse echo ultrasound," in Ultrasonics, 2003 IEEE Symposium on, 2003, pp. 1812-1815 Vol.2.
[33] P. Abolmaesumi, M. R. Sirouspour, and S. E. Salcudean, "Real-time extraction of carotid artery contours from ultrasound images," in Computer-Based Medical Systems, 2000. CBMS 2000. Proceedings. 13th IEEE Symposium on, 2000, pp. 181-186.
[34] R. G. Brown and P. Y. C. Hwang, Introduction to random signals and applied Kalman filtering. New York: Wiley, 1997.
[35] H. W. Sorenson, "Least-squares estimation: from Gauss to Kalman," Spectrum, IEEE, vol. 7, pp. 63-68, 1970.
[36] A. C. Raptis and S. Shuh-Haw, "Ultrasonic Properties of Coal Slurries and Flow Measurements by Cross Correlation," Sonics and Ultrasonics, IEEE Transactions on, vol. 28, pp. 248-256, 1981.
[37] J. A. Jensen and I. R. Lacasa, "Estimation of blood velocity vectors using transverse ultrasound beam focusing and cross-correlation," in Ultrasonics Symposium, 1999. Proceedings. 1999 IEEE, 1999, pp. 1493-1497 vol.2.
[38] R. Zahiri-Azar and S. E. Salcudean, "Motion Estimation in Ultrasound Images Using Time Domain Cross Correlation With Prior Estimates," Biomedical Engineering, IEEE Transactions on, vol. 53, pp. 1990-2000, 2006.
[39] M. W. Urban, S. Chen, and J. F. Greenleaf, "Error in estimates of tissue material properties from shear wave dispersion ultrasound vibrometry," IEEE Trans Ultrason Ferroelectr Freq Control, vol. 56, pp. 748-58, 2009.
[40] M. W. Urban, C. Shigao, and J. F. Greenleaf, "Error in estimates of tissue material properties from shear wave dispersion ultrasound vibrometry," Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 56, pp. 748-758, 2009.
[41] L. Huwart, F. Peeters, R. Sinkus, L. Annet, N. Salameh, L. C. ter Beek, et al., "Liver fibrosis: non-invasive assessment with MR elastography," NMR in Biomedicine, vol. 19, pp. 173-179, 2006.
[42] M. Muller, J. L. Gennisson, T. Deffieux, M. Tanter, and M. Fink, "Quantitative viscoelasticity mapping of human liver using supersonic shear imaging: preliminary in vivo feasibility study," Ultrasound Med Biol, vol. 35, pp. 219-29, 2009.
[43] X. Zhang and J. F. Greenleaf, "Measurement of wave velocity in arterial walls with ultrasound transducers," Ultrasound Med Biol, vol. 32, pp. 1655-60, 2006.
[44] K. Hoyt, B. Castaneda, M. Zhang, P. Nigwekar, P. A. di Sant'agnese, J. V. Joseph, et al., "Tissue elasticity properties as biomarkers for prostate cancer," Cancer Biomark, vol. 4, pp. 213-25, 2008.
[45] I. Nenadic, M. W. Urban, and J. F. Greenleaf, "Ex Vivo measurements of myocardial viscoelasticity using Shearwave Dispersion Ultrasound Vibrometry (SDUV)," in Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE, 2009, pp. 2895-2898.
[46] C. Pislaru, M. W. Urban, I. Nenadic, and J. F. Greenleaf, "Shearwave dispersion ultrasound vibrometry applied to in vivo myocardium," in Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE, 2009, pp. 2891-2894.
[47] C. Amador, M. W. Urban, J. F. Greenleaf, and L. V. Warner, "Measurements of swine renal cortex shear elasticity and viscosity with Shearwave Dispersion Ultrasound Vibrometry (SDUV)," in Ultrasonics Symposium (IUS), 2009 IEEE International, 2009, pp. 491-494.
[48] C. C. Huang, P. Y. Chen, and C. C. Shih, "Estimating the viscoelastic modulus of a thrombus using an ultrasonic shear-wave approach," Med Phys, vol. 40, p. 042901, 2013.
[49] E. L. Madsen, J. A. Zagzebski, R. A. Banjavie, and R. E. Jutila, "Tissue mimicking materials for ultrasound phantoms," Medical Physics, vol. 5, pp. 391-394, 1978.