A Two-Pulse Technique for Extracting 3(rd) Harmonic from Ulasound Contrast Agent Echo Signal
ABSTRACT Multi-pulse techniques like CPS (contrast pulse sequence) and TPS (triplet pulse sequence) are the most popular methods for separating the 3rd harmonic signals from received signal. Those two methods, however, transmit a pulse at least three times along each scanline with different phase and amplitude, which results in the frame rate reduction. In this paper, we propose a technique using two pulses whose phase difference is 90 degrees and a simple digital filter. The second harmonic signal is eliminated by summing two received signals as their phase difference becomes 180 degrees and then the fundamental signals are eliminated by using a digital filter. Computer simulations are performed for different values of signal bandwidths and filter specifications. The results show the maximum error is -35.5 dB compared to TPS.
Conference Paper: Triplet pulse sequence for superior microbubble/tissue contrast[Show abstract] [Hide abstract]
ABSTRACT: A triplet pulse sequence is proposed for imaging with superior microbubble/tissue selectivity. This sequence utilizes the difference in nonlinearity between the nonlinear propagation in tissue and the nonlinear scattering by microbubbles. Three-time transmit/receive are performed with transmit pulses having the same envelope and a phase shift by 120°, and the received echo signals are summed. Numerical analysis of the microbubble scattering and the propagation in tissue predicted the selectivity superior to the conventional pulse inversion sequence by more than 20 dB in an ideal case. An experiment using a prototype scanner with a Doppler flow phantom and a contrast agent demonstrated an improvement in the selectivity by 15 dB at a typical acoustic amplitude in B-mode imaging at 2 MHz.Ultrasonics, 2003 IEEE Symposium on; 11/2003
Conference Paper: A new imaging technique based on the nonlinear properties of tissues[Show abstract] [Hide abstract]
ABSTRACT: Finite amplitude sound propagating in a medium undergoes distortion due to the nonlinear properties of the medium. The nonlinear distortion produces harmonic (and subharmonic) energy in the propagating signal. The amplitudes used by commercial medical scanners during routine diagnostic scanning are in most cases finite and thus within the range that produces nonlinear distortion. Thermoviscous absorption of tissue which is frequency dependent rapidly dissipates this harmonic energy. This has led to the widely held assumption that nonlinear distortion was not a significant factor in medical diagnostic imaging. However, the wide dynamic range, digital architecture, and the signal processing capabilities of modern diagnostic ultrasound systems make it possible to utilize this tissue generated harmonic energy for image formation. These images often demonstrate reduced nearfield artifacts and improved tissue structure visualization. Previously, those images were believed to be the result of transmitted second harmonic energy. It is shown that the nonlinear properties of tissue are the major contribution of harmonic imagesUltrasonics Symposium, 1997. Proceedings., 1997 IEEE; 11/1997
- The Journal of the Acoustical Society of America 01/1998; 103(5). DOI:10.1121/1.422973 · 1.56 Impact Factor