Title :
A study of second harmonic generation by focused medical transducer pulses
Author :
Wojcik, Greg ; Mould, John ; Ayter, Sevig ; Carcione, Laura
Author_Institution :
Weidlinger Associates, Los Altos, CA, USA
Abstract :
Second harmonic imaging systems transmit relatively low frequency pulses, e.g., 2.5 MHz, and image the frequency-doubled second harmonic generated by acoustic nonlinearity. Imaging the second rather than the first harmonic eliminates significant wavefront aberration and attenuation on the forward path, narrows the beam, and suppresses sidelobes. This technique is used successfully in commercial medical imaging systems and may become dominant in the near future. However, system optimization requires a better understanding of second harmonic generation by focused ultrasound pulses in tissue. Data and simulations are presented quantifying aberration and second harmonic generation by two-dimensional ultrasound beams in realistic tissue models. A pseudo-spectral solver is used to achieve very high accuracy over long paths through lossy, nonlinear abdominal wall and liver
Keywords :
Runge-Kutta methods; acoustic signal processing; biological tissues; biomedical ultrasonics; finite difference methods; harmonic generation; image resolution; least squares approximations; medical image processing; nonlinear acoustics; optimisation; physiological models; spectral analysis; ultrasonic focusing; Runge-Kutta integrator; acoustic nonlinearity; beam narrowing; bioacoustic equation; finite difference models; focused medical transducer pulses; forward path; frequency-doubled second harmonic; image quality; least squares fitting; liver; lossy nonlinear abdominal wall; medical US imaging; pseudo-spectral solver; realistic tissue models; second harmonic generation; second harmonic imaging systems; sidelobe suppression; system optimization; two-dimensional ultrasound beams; very high accuracy; wave solver; wavefront aberration; wavefront attenuation; Acoustic beams; Acoustic imaging; Acoustic pulses; Acoustic transducers; Biomedical imaging; Biomedical transducers; Focusing; Frequency conversion; Pulse generation; Ultrasonic imaging;
Conference_Titel :
Ultrasonics Symposium, 1998. Proceedings., 1998 IEEE
Conference_Location :
Sendai
Print_ISBN :
0-7803-4095-7
DOI :
10.1109/ULTSYM.1998.765247