Abstract
Frame rate in ultrasound imaging can he increased by simultaneous transmission of multiple beams using coded
waveforms. However, the achievable degree of orthogonality among coded waveforms is limited in ultrasound,
and the image quality degrades unacceptably due to interbeam interference. In this paper, an alternative
combined time-space coding approach is undertaken. In the new method all transducer elements are excited
with short pulses and the high time-bandwidth (TB) product waveforms are generated acoustically. Each
element transmits a short pulse spherical wave with a constant transmit delay from element to element, long
enough to assure no pulse overlapping for all depths in the image. Frequency shift keying is used for "per
element" coding. The received signals from a point scatterer are staggered pulse trains which are beamformed
for all beam directions and further processed with a bank of matched filters (one for each beam direction).
Filtering compresses the pulse train to a single pulse at the scatterer position with a number of spike axial
sidelobes. Cancellation of the ambiguity spikes is done by applying additional phase modulation from one
emission to the next and summing every two successive images. Simulation results presented for QLFM and
Costas spatial encoding schemes show that the proposed method can yield images with range sidelobes down
to -45 dB using only two emissions.
Original language | English |
---|---|
Title of host publication | Proc.SPIE - Progress in biomedical optics and imaging |
Publisher | SPIE - International Society for Optical Engineering |
Publication date | 2002 |
Pages | 68-78 |
DOIs | |
Publication status | Published - 2002 |