A new method to increase the signal-to-noise-ratio (SNR) of synthetic transmit aperture (STA) imaging is investigated. The new approach is called temporally Encoded Multi-Element STA imaging (EMESTA). It utilizes mult...
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ISBN:
(纸本)0819444324
A new method to increase the signal-to-noise-ratio (SNR) of synthetic transmit aperture (STA) imaging is investigated. The new approach is called temporally Encoded Multi-Element STA imaging (EMESTA). It utilizes multiple elements to emulate a single transmit element, and the conventional short excitation pulses are replaced by linear FM signals. Simulations using Field II and measurements are compared to linear array imaging. A theoretical analysis shows a possible improvement in SNR of 17 dB. Simulations are done using an 8.5 MHz lineararray transducer with 128 elements. Spatial resolution results show better performance for EMESTA imaging after the lineararray focus. Both methods have similar contrast performance. Measurements are performed using our experimental multi-channel ultrasound scanning system, RASMUS. The designed linear FM signal obtains temporal sidelobes below -55 dB, and SNR investigations show improvements of 4-12 dB. The depth performance is investigated using a multi-target phantom. Results show a 30 mm increase in penetration depth with improved spatial resolution. In conclusion, EMESTA imaging significantly increases the SNR of STA imaging, exceeding that of linear array imaging.
This paper describes a method for adding thermal and amplifier noise to a KLM model for a transducer element. The model is used to compare the magnitudes of various noise sources in a 5 MHz array element typical of th...
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This paper describes a method for adding thermal and amplifier noise to a KLM model for a transducer element. The model is used to compare the magnitudes of various noise sources in a 5 MHz array element typical of those used for linear array imaging with and without an amplifier. Fundamental signal-to-noise ratio (SNR) issues of importance to array and amplifier designers are explored, including the effect on SNR of effective dielectric constant of the piezoelectric material, individual element size, changing the number of elements, and adding an amplifier to an element before and after a cable. SNR is considered both for the case in which the acoustic output is limited by the maximum rarefactive pressure which is considered safe for a particular application (Mechanical Index limitation) and the case in which acoustic output is limited by the maximum transmit voltage than can be delivered by the imaging system or tolerated by the transducer, It is shown that the SNR performance depends on many controllable parameters and that significant improvements in SNR can be achieved through proper design, The implications for 1.5-D and 2-D array elements are discussed.
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