@article{jing_cannata_wang_2013, title={Experimental verification of transient nonlinear acoustical holography}, volume={133}, ISSN={["1520-8524"]}, DOI={10.1121/1.4796120}, abstractNote={This paper presents an experimental study on nonlinear transient acoustical holography. The validity and effectiveness of a recently proposed nonlinear transient acoustical holography algorithm is evaluated in the presence of noise. The acoustic field measured on a post-focal plane of a high-intensity focused transducer is backward projected to reconstruct the pressure distributions on the focal and a pre-focal plane, which are shown to be in good agreement with the measurement. In contrast, the conventional linear holography produces erroneous results in this case where the nonlinearity involved is strong. Forward acoustic field projection was also carried out to further verify the algorithm.}, number={5}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Jing, Yun and Cannata, Jonathan and Wang, Tianren}, year={2013}, month={May}, pages={2533–2540} }
 @article{wang_jing_2013, title={Transcranial ultrasound imaging with speed of sound-based phase correction: a numerical study}, volume={58}, ISSN={["1361-6560"]}, DOI={10.1088/0031-9155/58/19/6663}, abstractNote={This paper presents a numerical study for ultrasound transcranial imaging. To correct for the phase aberration from the skull, two critical steps are needed prior to brain imaging. In the first step, the skull shape and speed of sound are acquired by either CT scans or ultrasound scans. In the ultrasound scan approach, phased array and double focusing technique are utilized, which are able to estimate the thickness of the skull with a maximum error of around 10% and the average speed of sound in the skull is underestimated by less than 2%. In the second step, the fast marching method is used to compute the phase delay based on the known skull shape and sound speed from the first step, and the computation can be completed in seconds for 2D problems. The computed phase delays are then used in combination with the conventional delay-and-sum algorithm for generating B-mode images. Images of wire phantoms with CT or ultrasound scan-based phase correction are shown to have much less artifact than the ones without correction. Errors of deducing speed of sound from CT scans are also discussed regarding its effect on the transcranial ultrasound images. Assuming the speed of sound grows linearly with the density, this study shows that, the CT-based phase correction approach can provide clear images of wire phantoms even if the speed of sound is overestimated by 400 m s−1, or the linear coefficient is overestimated by 40%. While in this study, ultrasound scan-based phase correction performs almost equally well with the CT-based approach, potential problems are identified and discussed.}, number={19}, journal={PHYSICS IN MEDICINE AND BIOLOGY}, author={Wang, Tianren and Jing, Yun}, year={2013}, month={Oct}, pages={6663–6681} }
 @article{jing_wang_clement_2012, title={A k-Space Method for Moderately Nonlinear Wave Propagation}, volume={59}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2012.2372}, abstractNote={A k-space method for moderately nonlinear wave propagation in absorptive media is presented. The Westervelt equation is first transferred into k-space via Fourier transformation, and is solved by a modified wave-vector time-domain scheme. The present approach is not limited to forward propagation or parabolic approximation. One- and two-dimensional problems are investigated to verify the method by comparing results to analytic solutions and finite-difference time-domain (FDTD) method. It is found that to obtain accurate results in homogeneous media, the grid size can be as little as two points per wavelength, and for a moderately nonlinear problem, the Courant–Friedrichs–Lewy number can be as large as 0.4. Through comparisons with the conventional FDTD method, the k-space method for nonlinear wave propagation is shown here to be computationally more efficient and accurate. The k-space method is then employed to study three-dimensional nonlinear wave propagation through the skull, which shows that a relatively accurate focusing can be achieved in the brain at a high frequency by sending a low frequency from the transducer. Finally, implementations of the k-space method using a single graphics processing unit shows that it required about one-seventh the computation time of a single-core CPU calculation.}, number={8}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Jing, Yun and Wang, Tianren and Clement, Greg T.}, year={2012}, month={Aug}, pages={1664–1673} }