A new method to increase the signal-to-noise ratio (SNR) of synthetic transmit aperture imaging is investigated. The approach utilizes multiple elements to emulate a spherical wave, and the conventional short excitation pulse is replaced by a linear frequency-modulated (FM) signal. The approach is evaluated in terms of image quality parameters in comparison to linear array imaging. Field II simulations using an 8.5-MHz linear array transducer with 128 elements show an improvement in lateral resolution of up to 30% and up to 10.75% improvement in contrast resolution for the new approach. Measurements are performed using our experimental multichannel ultrasound scanning system, RASMUS. The designed linear FM signal obtains temporal sidelobes below -55 dB, and SNR investigations show improvements of 4-12 dB. A 30 turn (approximate to45%) increase in penetration depth is obtained on a multitarget phantom with 0.5 dB/[cm MHz] attenuation. Furthermore, in vivo images of the abdomen are presented, which demonstrate the clinical application of the new approach.
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- synthetic transmit aperture ultrasound imaging
- multielement defocusing
- linear FM signals
- Experimental ultrasound scanning system
- Field II
Gammelmark, K., & Jensen, J. A. (2003). Multielement Synthetic Transmit Aperture Imaging Using Temporal Encoding. I E E E Transactions on Medical Imaging, 22(4), 552-563. https://doi.org/10.1109/TMI.2003.809088