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| September 1, 2009 |
| Dr. Chen’s Ultrasound Paper Featured on Cover of Medical Physics |
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Dr. Hao Chen, Ph.D. and post-doctoral fellow in Division of Medical Physics in Emory’s Department of Radiation Oncology had his journal paper titled “Multilevel hybrid 2D strain imaging algorithm for ultrasound sector/phased arrays” selected as the cover photo for the Journal of Medical Physics, June 2009 edition. Dr. Chen works in Dr. Tian Liu’s lab performing ultrasound imaging for application to radiation oncology. This journal paper explains that ultrasound elastography, which images the local stiffness variations in tissue, are relatively new techniques for the noninvasive evaluation of tissue mechanical properties. The work of Drs. Liu and Chen in elastographic and elasticity imaging applications in abdominal, transvaginal, and transrectal applications are rapidly gaining prominence. In this paper, Dr. Chen utilized a hierarchical multilevel search strategy using a pyramidal format to improve the computational speed of the algorithm. The hybrid method provided sharper boundaries, demonstrating the improved spatial resolution along with smoother strain distributions within the thermal lesion and in the background. Dr. Chen explained, “Our technique could provide high quality elasticity image of liver, uterus, heart, vocal cord etc with sector/phase array ultrasound transducer, and we plan to implement this technology in radiation oncology for early cancer detection and treatment evaluation.”
Paper citation: Hao Chen and Tomy Varghese. “Multilevel hybrid 2D strain imaging algorithm for ultrasound sector/phased arrays,” Med. Phys. Volume 36, Issue 6, pp. 2098-2106 (June 2009).
Permalink: http://dx.doi.org/10.1118/1.3121426
Paper Abstract: Two-dimensional (2D) cross-correlation algorithms are necessary to estimate local displacement vector information for strain imaging. However, most of the current two-dimensional cross-correlation algorithms were developed for linear array transducers. Although sector and phased array transducers are routinely used for clinical imaging of abdominal and cardiac applications, strain imaging for these applications has been performed using one-dimensional (1D) cross-correlation analysis.
However, one-dimensional cross-correlation algorithms are unable to provide accurate and precise strain estimation along all the angular insonification directions which can range from -45o to 45o with sector and phased array transducers.
In addition, since sector and phased array based images have larger separations between beam lines as the pulse propagates deeper into tissue, signal decorrelation artifacts with deformation or tissue motion are more pronounced. In this article, the authors propose a multilevel two-dimensional hybrid algorithm for ultrasound sector and phased array data that demonstrate improved tracking and estimation performance when compared to the traditional 1D cross-correlation or 2D cross-correlation based methods. Experimental results demonstrate that the signal-to-noise and contrast-to-noise ratio estimates improve significantly for smaller window lengths for the hybrid method when compared to the currently used one-dimensional or two-dimensional cross-correlation algorithms. Strain imaging results on ex vivo thermal lesions created in liver tissue and in vivo on cardiac short-axis views demonstrate the improved image quality obtained with this method. ©2009 American Association of Physicists in Medicine
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