Scholars@Duke

• Background
• 

  Education, Training, & Certifications

  • Ph.D., Duke University 1995
  • B.S.E., Duke University 1990
• 

  Previous Appointments & Affiliations

  • Assistant Research Professor of Biomedical Engineering, Biomedical Engineering, Pratt School of Engineering 1996 - 1997
• 

  Academic Positions Outside Duke

  • Professor of Biomedical Engineering, University of Virginia. 2009 - 2013
  • Associate Professor of Biomedical Engineering, University of Virginia. 2003 - 2009
  • Assistant Professor of Biomedical Engineering, University of Virginia. 1997 - 2003
• Research
• 

  Selected Grants

  • Ultrasonic Skin Elasticity Measurement Device awarded by MicroElastic Ultrasound Systems, Inc. 2017 - 2018
  • Research in High Energy Physics at Duke University awarded by Department of Energy 1991 - 1997
• 

  External Relationships

  • Advanced Robotic Construction
  • Boundless Science, LLC
  • CoapTech
  • CoolTech, LLC
  • FreeFlow Medical Devices
  • Hemosonics, LLC
  • Impulse Ultrasound, LLC
  • Key Technologies, Inc.
  • MicroElastic Ultrasound Systems Inc
  • Orchard Ultrasound Innovation
  • Sonus Microsystems
• Publications & Artistic Works
• 

  Selected Publications

  • Academic Articles

    • Morgan, Matthew R., Gregg E. Trahey, and William F. Walker. “Intrinsic Tradeoffs in Multi-Covariate Imaging of Sub-Resolution Targets.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 67, no. 10 (October 2020): 1980–92. https://doi.org/10.1109/tuffc.2020.2993241.
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    • Morgan, Matthew R., Nick Bottenus, Gregg E. Trahey, and William F. Walker. “Synthetic Aperture Focusing for Multi-Covariate Imaging of Sub-Resolution Targets.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 67, no. 6 (June 2020): 1166–77. https://doi.org/10.1109/tuffc.2020.2966116.
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    • Morgan, Matthew R., Gregg E. Trahey, and William F. Walker. “Speckle coherence of piecewise-stationary stochastic targets.” The Journal of the Acoustical Society of America 146, no. 3 (September 2019): 1721. https://doi.org/10.1121/1.5126686.
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    • Morgan, Matthew R., Gregg E. Trahey, and William F. Walker. “Multi-covariate Imaging of Sub-resolution Targets.” Ieee Transactions on Medical Imaging 38, no. 7 (July 2019): 1690–1700. https://doi.org/10.1109/tmi.2019.2917021.
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    • Corey, F Scott, and William F. Walker. “Sonic Estimation of Elasticity via Resonance: A New Method of Assessing Hemostasis.” Annals of Biomedical Engineering 44, no. 5 (May 2016): 1405–24. https://doi.org/10.1007/s10439-015-1460-y.
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    • Viola, Francesco, Xiefan Lin-Schmidt, Castigliano Bhamidipati, Doris M. Haverstick, William F. Walker, Gorav Ailawadi, and Michael B. Lawrence. “Sonorheometry assessment of platelet function in cardiopulmonary bypass patients: Correlation of blood clot stiffness with platelet integrin αIIbβ3 activity, aspirin usage, and transfusion risk.” Thrombosis Research 138 (February 2016): 96–102. https://doi.org/10.1016/j.thromres.2015.11.036.
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    • Durst, Christopher, Stephen Monteith, Jason Sheehan, Krisztina Moldovan, John Snell, Matt Eames, Thomas Huerta, et al. “Optimal imaging of in vitro clot sonothrombolysis by MR-guided focused ultrasound.” Journal of Neuroimaging : Official Journal of the American Society of Neuroimaging 23, no. 2 (April 2013): 187–91. https://doi.org/10.1111/j.1552-6569.2011.00662.x.
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    • Guenther, Drake A., and William F. Walker. “Broadband optimal contrast resolution beamforming.” Ultrasonics 52, no. 3 (March 2012): 387–401. https://doi.org/10.1016/j.ultras.2011.09.005.
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    • Mauldin, F William, Francesco Viola, and William F. Walker. “Complex principal components for robust motion estimation.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 57, no. 11 (November 2010): 2437–49. https://doi.org/10.1109/tuffc.2010.1710.
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    • Ellis, Michael A., Francesco Viola, and William F. Walker. “Super-resolution image reconstruction using diffuse source models.” Ultrasound in Medicine & Biology 36, no. 6 (June 2010): 967–77. https://doi.org/10.1016/j.ultrasmedbio.2010.03.002.
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    • Mauldin, F William, Francesco Viola, Theresa C. Hamer, Eman M. Ahmed, Shawna B. Crawford, Doris M. Haverstick, Michael B. Lawrence, and William F. Walker. “Adaptive force sonorheometry for assessment of whole blood coagulation.” Clinica Chimica Acta; International Journal of Clinical Chemistry 411, no. 9–10 (May 2010): 638–44. https://doi.org/10.1016/j.cca.2010.01.018.
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    • Viola, Francesco, F William Mauldin, Xiefan Lin-Schmidt, Doris M. Haverstick, Michael B. Lawrence, and William F. Walker. “A novel ultrasound-based method to evaluate hemostatic function of whole blood.” Clinica Chimica Acta; International Journal of Clinical Chemistry 411, no. 1–2 (January 2010): 106–13. https://doi.org/10.1016/j.cca.2009.10.017.
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    • Mauldin, F William, Francesco Viola, and William F. Walker. “Reduction of echo decorrelation via complex principal component filtering.” Ultrasound in Medicine & Biology 35, no. 8 (August 2009): 1325–43. https://doi.org/10.1016/j.ultrasmedbio.2009.01.013.
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    • Guenther, Drake A., and William F. Walker. “Robust finite impulse response beamforming applied to medical ultrasound.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 56, no. 6 (June 2009): 1168–88. https://doi.org/10.1109/tuffc.2009.1159.
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    • Guenther, Drake A., and William F. Walker. “A method for accurate in silico modeling of ultrasound transducer arrays.” Ultrasonics 49, no. 4–5 (May 2009): 404–12. https://doi.org/10.1016/j.ultras.2008.10.010.
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    • Guenther, Drake A., and William F. Walker. “Generalized cystic resolution: a metric for assessing the fundamental limits on beamformer performance.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 56, no. 1 (January 2009): 77–90. https://doi.org/10.1109/tuffc.2009.1007.
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    • Viola, Francesco, Ryan L. Coe, Kevin Owen, Drake A. Guenther, and William F. Walker. “MUlti-Dimensional Spline-Based Estimator (MUSE) for motion estimation: algorithm development and initial results.” Annals of Biomedical Engineering 36, no. 12 (December 2008): 1942–60. https://doi.org/10.1007/s10439-008-9564-2.
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    • Viola, Francesco, and William F. Walker. “Computationally efficient spline-based time delay estimation.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 55, no. 9 (September 2008): 2084–91. https://doi.org/10.1109/tuffc.900.
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    • Fuller, Michael I., Karthik Ranganathan, Shiwei Zhou, Travis N. Blalock, John A. Hossack, and William F. Walker. “Experimental system prototype of a portable, low-cost, C-scan ultrasound imaging device.” Ieee Transactions on Bio Medical Engineering 55, no. 2 Pt 1 (February 2008): 519–30. https://doi.org/10.1109/tbme.2007.903517.
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    • Viola, F., M. A. Ellis, and W. F. Walker. “Time-domain optimized near-field estimator for ultrasound imaging: initial development and results.” Ieee Transactions on Medical Imaging 27, no. 1 (January 2008): 99–110. https://doi.org/10.1109/tmi.2007.903579.
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    • Ellis, Michael A., Drake Guenther, and William F. Walker. “A spline-based approach for computing spatial impulse responses.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 54, no. 5 (May 2007): 1045–54. https://doi.org/10.1109/tuffc.2007.350.
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    • Ranganathan, Karthik, and William F. Walker. “Cystic resolution: a performance metric for ultrasound imaging systems.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 54, no. 4 (April 2007): 782–92. https://doi.org/10.1109/tuffc.2007.311.
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    • Guenther, Drake A., and William F. Walker. “Optimal apodization design for medical ultrasound using constrained least squares part I: theory.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 54, no. 2 (February 2007): 332–42. https://doi.org/10.1109/tuffc.2007.247.
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    • Fuller, Michael I., Travis N. Blalock, John A. Hossack, and William F. Walker. “Novel transmit protection scheme for ultrasound systems.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 54, no. 1 (January 2007): 79–86. https://doi.org/10.1109/tuffc.2007.213.
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    • Viola, Francesco, and William F. Walker. “A comparison between spline-based and phase-domain time-delay estimators.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 53, no. 3 (March 2006): 515–17. https://doi.org/10.1109/tuffc.2006.1610558.
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    • Ha, Jun S., William F. Walker, and John A. Hossack. “Determination of an optimal image frame interval for frame-to-frame ultrasound image motion tracking.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 52, no. 3 (March 2005): 386–96. https://doi.org/10.1109/tuffc.2005.1417261.
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    • Viola, Francesco, and William F. Walker. “A spline-based algorithm for continuous time-delay estimation using sampled data.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 52, no. 1 (January 2005): 80–93. https://doi.org/10.1109/tuffc.2005.1397352.
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    • Ranganathan, Karthik, Mary K. Santy, Travis N. Blalock, John A. Hossack, and William F. Walker. “Direct sampled I/Q beamforming for compact and very low-cost ultrasound imaging.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 51, no. 9 (September 2004): 1082–94. https://doi.org/10.1109/tuffc.2004.1334841.
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    • Viola, Francesco, Margaret D. Kramer, Michael B. Lawrence, James P. Oberhauser, and William F. Walker. “Sonorheometry: a noncontact method for the dynamic assessment of thrombosis.” Annals of Biomedical Engineering 32, no. 5 (May 2004): 696–705. https://doi.org/10.1023/b:abme.0000030235.72255.df.
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    • Viola, Francesco, and William F. Walker. “Radiation force imaging of viscoelastic properties with reduced artifacts.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 50, no. 6 (June 2003): 736–42. https://doi.org/10.1109/tuffc.2003.1209564.
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    • Viola, Francesco, and William F. Walker. “A comparison of the performance of time-delay estimators in medical ultrasound.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 50, no. 4 (April 2003): 392–401. https://doi.org/10.1109/tuffc.2003.1197962.
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    • Ranganathan, Karthik, and William F. Walker. “A novel beamformer design method for medical ultrasound. Part I: Theory.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 50, no. 1 (January 2003): 15–24. https://doi.org/10.1109/tuffc.2003.1176522.
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    • Ranganathan, Karthik, and William F. Walker. “A novel beamformer design method for medical ultrasound. Part II: Simulation results.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 50, no. 1 (January 2003): 25–39. https://doi.org/10.1109/tuffc.2003.1176523.
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    • Negron, Laura A., Francesco Viola, Eric P. Black, Cynthia A. Toth, and William F. Walker. “Development and characterization of a vitreous mimicking material for radiation force imaging.” Ieee Trans Ultrason Ferroelectr Freq Control 49, no. 11 (November 2002): 1543–51. https://doi.org/10.1109/tuffc.2002.1049736.
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    • Park, Eric Y. H., McRae J. Smith, Emily S. Stropp, Karen R. Snapp, Jeffrey A. DiVietro, William F. Walker, David W. Schmidtke, Scott L. Diamond, and Michael B. Lawrence. “Comparison of PSGL-1 microbead and neutrophil rolling: microvillus elongation stabilizes P-selectin bond clusters.” Biophysical Journal 82, no. 4 (April 2002): 1835–47. https://doi.org/10.1016/s0006-3495(02)75534-3.
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    • Cheezum, M. K., W. F. Walker, and W. H. Guilford. “Quantitative comparison of algorithms for tracking single fluorescent particles.” Biophysical Journal 81, no. 4 (October 2001): 2378–88. https://doi.org/10.1016/s0006-3495(01)75884-5.
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    • Walker, W. F. “C- and D-weighted ultrasonic imaging using the translating apertures algorithm.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 48, no. 2 (March 2001): 452–61. https://doi.org/10.1109/58.911728.
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    • Fabian, C. M., K. N. Ballu, J. A. Hossack, T. N. Blalock, and W. F. Walker. “Development of a parallel acquisition system for ultrasound research.” Proceedings of Spie  the International Society for Optical Engineering 4325 (January 1, 2001): 54–62. https://doi.org/10.1117/12.428238.
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    • McAllister, M. J., K. W. Rigby, and W. F. Walker. “Evaluation of translating apertures based angular scatter imaging on a clinical imaging system.” Proceedings of the Ieee Ultrasonics Symposium 2 (January 1, 2001): 1555–58. https://doi.org/10.1109/ULTSYM.2001.992017.
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    • Walker, W. F., F. J. Fernandez, and L. A. Negron. “A method of imaging viscoelastic parameters with acoustic radiation force.” Physics in Medicine and Biology 45, no. 6 (June 2000): 1437–47. https://doi.org/10.1088/0031-9155/45/6/303.
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    • McAllister, M. J., and W. F. Walker. “Novel approaches to angular scatter imaging using the translating apertures algorithm.” Proceedings of Spie  the International Society for Optical Engineering 3982 (January 1, 2000): 360–69.
    • Negron, L. A., W. F. Walker, and F. J. Fernandez. “Tissue elasticity using acoustic radiation force.” Proceedings of Spie  the International Society for Optical Engineering 3982 (January 1, 2000): 306–14.
    • Walker, W. F. “Internal deformation of a uniform elastic solid by acoustic radiation force.” The Journal of the Acoustical Society of America 105, no. 4 (April 1999): 2508–18. https://doi.org/10.1121/1.426854.
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    • Walker, W. F., and G. E. Trahey. “The application of k-space in pulse echo ultrasound.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 45, no. 3 (January 1998): 541–58. https://doi.org/10.1109/58.677599.
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    • Walker, W. F., and G. E. Trahey. “Aberrator integration error in adaptive imaging.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 44, no. 4 (December 1, 1997): 780–91. https://doi.org/10.1109/58.655192.
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    • Walker, W. F., and G. E. Trahey. “Speckle coherence and implications for adaptive imaging.” The Journal of the Acoustical Society of America 101, no. 4 (April 1997): 1847–58. https://doi.org/10.1121/1.418235.
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    • Ng, G. C., P. D. Freiburger, W. F. Walker, and G. E. Trahey. “A speckle target adaptive imaging technique in the presence of distributed aberrations.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 44, no. 1 (January 1997): 140–51. https://doi.org/10.1109/58.585209.
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    • Ng, G. C., W. F. Walker, and G. E. Trahey. “Improvement of signal correlation for adaptive imaging using the translating transmit aperture algorithm.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1996): 1395–1400.
    • Ng, G. C., P. D. Freiburger, W. F. Walker, and G. E. Trahey. “New technique for adaptive imaging in the presence of distributed aberrations.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1995): 1455–59.
    • Walker, W. F., and G. E. Trahey. “Limits on the performance of near field phase aberration correction.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1995): 1461–65.
    • Walker, W. F., and G. E. Trahey. “Application of K-space in medical ultrasound.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1995): 1379–83.
    • Nightingale, K. R., P. J. Kornguth, W. F. Walker, B. A. McDermott, and G. E. Trahey. “A novel ultrasonic technique for differentiating cysts from solid lesions: preliminary results in the breast.” Ultrasound in Medicine & Biology 21, no. 6 (January 1995): 745–51. https://doi.org/10.1016/0301-5629(95)00020-r.
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    • Walker, W. F., and G. E. Trahey. “A Fundamental Limit on Delay Estimation Using Partially Correlated Speckle Signals.” Ieee Transactions on Ultrasonics, Ferroelectrics and Frequency Control 42, no. 2 (January 1, 1995): 301–8. https://doi.org/10.1109/58.365243.
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    • Walker, W. F., and G. E. Trahey. “Real-time synthetic receive aperture imaging: experimental results.” Proceedings of the Ieee Ultrasonics Symposium 3 (December 1, 1994): 1657–60.
    • Walker, W. F., and G. E. Trahey. “Fundamental limit on the accuracy of speckle signal alignment.” Proceedings of the Ieee Ultrasonics Symposium 3 (December 1, 1994): 1787–91.
    • Walker, W. F., and G. E. Trahey. “Fundamental limit on the performance of correlation based phase correction and flow estimation techniques.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 41, no. 5 (September 1, 1994): 646–54.
    • Nightingale, K. R., P. J. Kornguth, W. F. Walker, S. C. Glasgow, E. A. Jett, and G. E. Trahey. “Generation and detection of acoustic streaming to differentiate between solid and cystic breast lesions.” Proceedings of the Ieee Ultrasonics Symposium 3 (January 1, 1994): 1653–56. https://doi.org/10.1109/ultsym.1994.401907.
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    • Walker, W. F., and G. E. Trahey. “A Fundamental Limit on the Performance of Correlation Based Phase Correction and Flow Estimation Techniques.” Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 41, no. 5 (January 1, 1994): 644–54. https://doi.org/10.1109/58.308499.
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    • Walker, W. F., B. H. Friemel, L. N. Bohs, and G. E. Trahey. “Real-time imaging of tissue vibration using a two-dimensional speckle tracking system.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1993): 873–77.
    • Walker, W. F., and G. E. Trahey. “Fundamental limit on the performance of phase aberration correction and correlation based flow estimates in medical ultrasound.” Proceedings of the Ieee Ultrasonics Symposium 2 (December 1, 1993): 1149–53.
    • Alsberg, E., G. E. Trahey, L. N. Bohs, B. H. Friemel, K. R. Nightingale, and W. F. Walker. “Three-dimensional flow visualization via reconstruction from successive two-dimensional vector velocity maps (Accepted).” Proceedings of 16th Annual International Conference of the Ieee Engineering in Medicine and Biology Society, n.d. https://doi.org/10.1109/iembs.1994.411884.
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  • Book Sections

    • Viola, F., C. A. Toth, and W. F. Walker. “Mechanical characterization of the vitreous body with acoustic radiation force,” 3:1777–80, 2004.
    • Walker, W. F., L. A. Negron, T. J. Mondzelewski, M. J. McAllister, F. J. Fernandez, and C. A. Toth. “Imaging the stiffness of the vitreous body with acoustic radiation force,” 2:1635–38, 1999.

  • Other Articles

    • Walker, W. F., R. E. Davidsen, and C. A. Toth. “Application of acoustic radiation force in ophthalmic ultrasound.” Proceedings of the Ieee Ultrasonics Symposium, December 1, 1997.

  • Conference Papers

    • Corey, F. S., and W. F. Walker. “Sonic Estimation of Elasticity via Resonance (SEER).” In 2015 Ieee International Ultrasonics Symposium, Ius 2015, 2015. https://doi.org/10.1109/ULTSYM.2015.0221.
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    • Lawrence, M. B., X. Lin-Schmidt, F. Viola, G. Ailawadi, and W. F. Walker. “Sonorheometry assessment of aspirin effects on platelet contributions to blood clot stiffness ex vivo in patients undergoing cardiopulmonary bypass procedures.” In Journal of Thrombosis and Haemostasis, 11:511–511, 2013.
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    • Ellis, M. A., and W. F. Walker. “Super-resolution image reconstruction with reduced computational complexity.” In Proceedings  Ieee Ultrasonics Symposium, 2351–54, 2009. https://doi.org/10.1109/ULTSYM.2009.5441782.
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    • Fuller, M. I., K. Owen, T. N. Blalock, J. A. Hossack, and W. F. Walker. “Real time imaging with the sonic window: A pocket-sized, C-scan, medical ultrasound device.” In Proceedings  Ieee Ultrasonics Symposium, 196–99, 2009. https://doi.org/10.1109/ULTSYM.2009.5441943.
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    • Mauldin, F. W., F. Viola, X. Lin-Schmidt, M. B. Lawrence, and W. F. Walker. “Adaptive radiation force ultrasound for monitoring hemostasis in whole blood.” In Proceedings  Ieee Ultrasonics Symposium, 173–76, 2009. https://doi.org/10.1109/ULTSYM.2009.5441879.
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    • Mauldin, F. W., F. Viola, and W. F. Walker. “Robust motion estimation using complex principal components.” In Proceedings  Ieee Ultrasonics Symposium, 2429–32, 2009. https://doi.org/10.1109/ULTSYM.2009.5441867.
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    • Ellis, M. A., and W. F. Walker. “Reduced rank formulation for increased computational efficiency in medical ultrasound model-based beamforming.” In Conference Record  Asilomar Conference on Signals, Systems and Computers, 1923–26, 2008. https://doi.org/10.1109/ACSSC.2008.5074764.
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    • Owen, K., D. A. Guenther, and W. F. Walker. “Beamformer enhancement by post-processing for improved spatial resolution and signal-to-noise ratio.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, Vol. 6920, 2008. https://doi.org/10.1117/12.772942.
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    • Ellis, M. A., F. Viola, and W. F. Walker. “Diffuse targets for improved contrast in beamforming adapted to target.” In Proceedings  Ieee Ultrasonics Symposium, 216–19, 2007. https://doi.org/10.1109/ULTSYM.2007.65.
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    • Guenther, D. A., and W. F. Walker. “Optimal contrast resolution beamforming.” In Proceedings  Ieee Ultrasonics Symposium, 37–41, 2007. https://doi.org/10.1109/ULTSYM.2007.23.
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    • Owen, K., and W. F. Walker. “Novel method for design and fabrication of single piston transducers for extended depth of field.” In Proceedings  Ieee Ultrasonics Symposium, 793–96, 2007. https://doi.org/10.1109/ULTSYM.2007.203.
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    • Viola, F., F. William Mauldin, S. P. Tropello, B. Gail Macik, M. B. Lawrence, and W. F. Walker. “Sonorheometry: A new method for assessing coagulation potential.” In Proceedings  Ieee Ultrasonics Symposium, 1001–4, 2007. https://doi.org/10.1109/ULTSYM.2007.255.
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    • Viola, F., D. A. Guenther, R. L. Coe, and W. F. Walker. “Multi-dimensional spline-based non-rigid image registration.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, Vol. 6513, 2007. https://doi.org/10.1117/12.710574.
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    • Guenther, Drake A., and William F. Walker. “Optimal apodization design for medical ultrasound using constrained least squares part II: simulation results.” In Ieee Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 54:343–58, 2007. https://doi.org/10.1109/tuffc.2007.248.
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    • Guenther, D. A., and W. F. Walker. “Receive channel FIR filters for enhanced contrast in medical ultrasound.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, Vol. 6513, 2007. https://doi.org/10.1117/12.709702.
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    • Ellis, M. A., and W. F. Walker. “Piecewise-linear approximation for improved accuracy in near-field ultrasound simulation.” In Proceedings  Ieee Ultrasonics Symposium, 1:1698–1701, 2006. https://doi.org/10.1109/ULTSYM.2006.428.
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    • Viola, F., M. A. Ellis, and W. F. Walker. “Ultrasound imaging with beamforming adapted to target.” In Proceedings  Ieee Ultrasonics Symposium, 1:128–31, 2006. https://doi.org/10.1109/ULTSYM.2006.45.
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    • Viola, F., M. A. Ellis, and W. F. Walker. “Near-field, broadband adaptive beamforming for ultrasound imaging.” In Conference Record  Asilomar Conference on Signals, Systems and Computers, 1543–47, 2006. https://doi.org/10.1109/ACSSC.2006.355017.
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    • Walker, W. F., D. A. Guenther, R. L. Coe, and F. Viola. “A novel spline-based algorithm for multidimensional displacement and strain estimation.” In Proceedings  Ieee Ultrasonics Symposium, 1:1221–25, 2006. https://doi.org/10.1109/ULTSYM.2006.311.
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    • Walker, W. F., M. I. Fuller, E. V. Brush, M. D. C. Eames, K. Owen, K. Ranganathan, T. N. Blalock, and J. A. Hossack. “The Sonic Window: Second generation results.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, Vol. 6147, 2006. https://doi.org/10.1117/12.661507.
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    • Fuller, M. I., E. V. Brush, M. D. C. Eames, T. N. Blalock, J. A. Hossack, and W. F. Walker. “The sonic window: Second generation prototype of low-cost, fully-integrated, pocket-sized medical ultrasound device.” In Proceedings  Ieee Ultrasonics Symposium, 1:273–76, 2005. https://doi.org/10.1109/ULTSYM.2005.1602848.
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    • Li, Y., T. N. Blalock, W. F. Walker, and J. A. Hossack. “Phased subarrays for low cost C-scan applications.” In Proceedings  Ieee Ultrasonics Symposium, 2:1408–11, 2005. https://doi.org/10.1109/ULTSYM.2005.1603118.
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    • Li, Y., T. N. Blalock, W. F. Walker, and J. A. Hossack. “"Synthetic axial acquisition" full resolution C-scan ultrasonic imaging.” In Proceedings  Ieee Ultrasonics Symposium, 2:1392–95, 2005. https://doi.org/10.1109/ULTSYM.2005.1603114.
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    • Ranganathan, K., D. A. Guenther, and W. F. Walker. “Design of apodization profiles using a cystic resolution metric for ultrasound.” In Proceedings  Ieee Ultrasonics Symposium, 2:1207–10, 2005. https://doi.org/10.1109/ULTSYM.2005.1603068.
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    • Santy, M. K., T. N. Blalock, and W. F. Walker. “Design and evaluation of a PC card for acoustic radiation force based mechanical characterization.” In Proceedings  Ieee Ultrasonics Symposium, 3:1428–30, 2005. https://doi.org/10.1109/ULTSYM.2005.1603124.
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    • Viola, F., and W. F. Walker. “Adaptive signal processing in medical ultrasound beamforming.” In Proceedings  Ieee Ultrasonics Symposium, 4:1980–83, 2005. https://doi.org/10.1109/ULTSYM.2005.1603264.
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    • Fuller, M. I., K. Ranganathan, S. Zhou, T. N. Blalock, J. A. Hossack, and W. F. Walker. “Portable, low-cost medical ultrasound device prototype.” In Proceedings  Ieee Ultrasonics Symposium, 1:106–9, 2004. https://doi.org/10.1109/ULTSYM.2004.1417679.
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    • Guenther, D. A., K. Ranganathan, M. J. McAllister, K. W. Rigby, and W. F. Walker. “Synthetic aperture methods for angular scatter imaging.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, 5:52–60, 2004. https://doi.org/10.1117/12.540671.
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    • Guenther, D. A., K. Ranganathan, M. J. McAllister, W. F. Walker, and K. W. Rigby. “Ultrasonic synthetic aperture angular scatter imaging.” In Conference Record  Asilomar Conference on Signals, Systems and Computers, 1:163–67, 2004.
    • Guenther, D. A., K. Ranganathan, M. J. McAllister, W. F. Walker, and K. W. Rigby. “Synthetic aperture angular scatter imaging: System refinement.” In Proceedings  Ieee Ultrasonics Symposium, 1:243–47, 2004.
    • Ranganathan, K., M. K. Santy, M. I. Fuller, S. Zhou, T. N. Blalock, J. A. Hossack, and W. F. Walker. “A prototype low cost handheld ultrasound imaging system.” In Progress in Biomedical Optics and Imaging  Proceedings of Spie, 5:24–32, 2004. https://doi.org/10.1117/12.537724.
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    • Ranganathan, K., and W. F. Walker. “A new performance analysis metric for medical ultrasound.” In Proceedings  Ieee Ultrasonics Symposium, 3:1737–40, 2004.
    • Viola, F., and W. F. Walker. “Efficient and accurate spline-based time delay estimation.” In Proceedings  Ieee Ultrasonics Symposium, 2:870–73, 2004.
    • Viola, F., and W. F. Walker. “Spline based time delay estimation.” In Conference Record  Asilomar Conference on Signals, Systems and Computers, 1:173–77, 2004.
    • Fuller, M. I., T. N. Blalock, J. A. Hossack, and W. F. Walker. “A portable, low-cost, highly integrated, 3D medical ultrasound system.” In Proceedings of the Ieee Ultrasonics Symposium, 1:38–41, 2003.
    • Girard, E., S. Zhou, W. Walker, T. Blalock, and J. Hossack. “High element count two dimensional transducer array.” In Proceedings of the Ieee Ultrasonics Symposium, 1:964–67, 2003.
    • Ha, J. S., W. F. Walker, and J. A. Hossack. “Optimum frame interval for ultrasound image motion estimation.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1541–44, 2003.
    • Ranganathan, K., M. K. Santy, J. A. Hossack, T. N. Blalock, and W. F. Walker. “Direct sampled I/Q beamforming: A strategy for very low cost ultrasound.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1863–66, 2003.
    • Viola, F., and W. F. Walker. “A new algorithm for continuous time delay estimation using sampled data.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1834–38, 2003.
    • Mann, J. A., and W. F. Walker. “Constrained adaptive beamforming: Point and contrast resolution.” In Proceedings of Spie  the International Society for Optical Engineering, 5035:12–23, 2003. https://doi.org/10.1117/12.479959.
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    • Mann, J. A., and W. F. Walker. “A constrained adaptive beamformer for medical ultrasound: Initial results.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1807–10, 2002.
    • Ranganathan, K., and W. F. Walker. “The minimum sum squared error (MSSE) beamformer design technique: Initial results.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1697–1700, 2002.
    • Viola, F., and W. F. Walker. “Ultrasound echo decorrelation due to acoustic radiation force.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1903–6, 2002.
    • Viola, F., and W. F. Walker. “Shear strain elastography.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1907–11, 2002.
    • Walker, W. F., and M. J. McAllister. “Angular scatter imaging: Clinical results and novel processing.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1565–69, 2002.
    • Walker, W. F., and M. J. McAllister. “Angular scatter imaging in medical ultrasound.” In Conference Record of the Asilomar Conference on Signals, Systems and Computers, 1:931–35, 2002.
    • Inrana, M. F., and W. F. Walker. “Erratum: (Medical Imaging 2002 Ultrasonic Imaging and Signal Processing (26-28 February 2002)).” In Proceedings of Spie  the International Society for Optical Engineering, 4687:462, 2002.
    • Insana, M. F., and W. F. Walker. “Proceedings of SPIE - The International Society for Optical Engineering: Introduction.” In Proceedings of Spie  the International Society for Optical Engineering, Vol. 4687, 2002.
    • Ranganathan, K., and W. F. Walker. “A novel aperture design method in ultrasound imaging.” In Proceedings of Spie  the International Society for Optical Engineering, 4687:13–24, 2002. https://doi.org/10.1117/12.462159.
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    • Viola, F., D. M. Longo, M. B. Lawrence, and W. F. Walker. “Analysis of clot formation with acoustic radiation force.” In Proceedings of Spie  the International Society for Optical Engineering, 4687:235–42, 2002. https://doi.org/10.1117/12.462160.
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    • Ranganathan, K., and W. F. Walker. “A novel aperture design method for improved depth of field in ultrasound imaging.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1543–46, 2001.
    • Viola, F., and W. F. Walker. “Comparison of time delay estimators in medical ultrasound.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1485–88, 2001.
    • Viola, F., and W. F. Walker. “Imaging viscoelastic properties of the vitreous.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1623–26, 2001.
    • Walker, W. F. “The significance of correlation in ultrasound signal processing.” In Proceedings of Spie  the International Society for Optical Engineering, 4325:159–71, 2001. https://doi.org/10.1117/12.428192.
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    • Ranganathan, K., and W. F. Walker. “Analysis of C- and D-weighted imaging using the translating apertures algorithm.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1605–9, 2000.
    • Cheezum, M. K., W. F. Walker, and W. H. Guilford. “A comparison of particle tracking algorithms: Implications for in vitro motility and single molecule fluorescence.” In Biophysical Journal, 78:249A-249A, 2000.
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    • Halpin, G., L. D. Benefield, W. F. Walker, and S. MacGuire. “An Evaluation of an Integrated Pre-Engineering Program: Results from the Freshman Year and Beyond.” In Asee Annual Conference Proceedings, 625–46, 1999.
    • Lawrence, M. B., M. J. Smith, and W. F. Walker. “Force modulation of selectin mediated leukocyte adhesive dynamics.” In Annual International Conference of the Ieee Engineering in Medicine and Biology  Proceedings, 1:60, 1999.
    • Walker, W. F., and M. J. McAllister. “C- and D-weighted imaging: theory and simulation.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1557–61, 1999.
    • Walker, W. F., T. J. Mondzelewski, M. J. McAllister, F. J. Fernandez, and C. A. Toth. “Imaging of vitreous mechanical properties.” In Investigative Ophthalmology & Visual Science, 40:S571–S571. ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 1999.
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    • Walker, W. F. “New class of aperture domain flow estimation algorithms.” In Proceedings of the Ieee Ultrasonics Symposium, 2:1227–32, 1997.
    • Alsberg, E., G. E. Trahey, L. N. Bohs, B. H. Friemel, K. R. Nightingale, and W. F. Walker. “Three-dimensional flow visualization via reconstruction from successive two-dimensional vector velocity maps.” In Annual International Conference of the Ieee Engineering in Medicine and Biology  Proceedings, 16:598–99, 1994.
• Teaching & Mentoring
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  Recent Courses

  • EGR 79: Thrive 2021
  • EGR 79S: Thrive 2020
  • EGRMGMT 551: Engineering Management Internship Assessment 2020
  • EGRMGMT 590: Advanced Topics in Engineering Management 2020
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