Biomedical subjects

Qingyu Ma

Publications and source records attributed to Qingyu Ma.

3 recordsLinked to original sources

PubMed2006

Third order harmonic imaging for biological tissues using three phase-coded pulses.

Compared to the fundamental and the second harmonic imaging, the third harmonic imaging shows significant improvements in image quality due to the better resolution, but it is degraded by the lower sound pressure and signal-to-noise ratio (SNR). In this study, a phase-coded pulse technique is proposed to selectively enhance the sound pressure of the third harmonic by 9.5 dB whereas the fundamental and the second harmonic components are efficiently suppressed and SNR is also increased by 4.7 dB. Based on the solution of the KZK nonlinear equation, the axial and lateral beam profiles of harmonics radiated from a planar piston transducer were theoretically simulated and experimentally examined. Finally, the third harmonic images using this technique were performed for several biological tissues and compared with the images obtained by the fundamental and the second harmonic imaging. Results demonstrate that the phase-coded pulse technique yields a dramatically cleaner and sharper contrast image.

Algorithms↗

PubMed2006

Investigation of superharmonic sound propagation and imaging in biological tissues in vitro.

This article presents both theoretical and experimental studies on the superharmonic generation and its imaging in biological tissues. A superharmonic component is defined as a summation of the third-, fourth-, and fifth-order harmonics. A superharmonic signal is produced using an 8-mm-diam, 2.5-MHz planar piston source that is excited by eight-cycle, 2.5-MHz tone bursts. Axial and lateral field distributions of the superharmonic component and the second harmonic are first calculated based on the nonlinear KZK model and then compared with those experimentally determined at two different source pressures of 0.5 and 1 MPa. Results indicate that the amplitude of the superharmonic component can exceed that of the second harmonic, depending on the axial distance and the fundamental pressure amplitude. Also, the 3-dB beamwidth of the superharmonic component is about 23% narrower than that of the second harmonic. Additional experiments are performed in vitro using liver and fatty tissues in transmission mode and produced two-dimensional images using the fundamental, the second harmonic, and the superharmonic signals. Although the clinical applicability of this work still needs to be assessed, these results indicate that the superharmonic image quality is better than that of the other two images.

Acoustics↗

PubMed2005

Improvement of tissue harmonic imaging using the pulse-inversion technique.

Harmonic imaging has brought about significant improvements in image quality by taking advantage of the second harmonic component, but it still has one shortcoming, namely, a low signal-to-noise ratio. In this paper, a pulse-inversion technique is used in second harmonic imaging for biologic tissues to increase the signal-to-noise ratio. Enhancement of the second harmonic component is theoretically analyzed based on the theory of the finite amplitude sound wave and confirmed by the measurement. Second harmonic imaging for biologic tissues is constructed with the pulse-inversion technique and compared with the traditional fundamental frequency and also with second harmonic imaging before the use of this technique. Results demonstrate that this technique yields a dramatically cleaner and sharper contrast between the different structures of biologic tissues in ultrasonic images.

Acoustics↗