Adaptive ultrasonic measurement of blood vessel diameter and wallthickness: theory and experimental results

摘要

An adaptive ultrasonic technique for measuring blood vesselndiameter and wall thickness is presented. This technique allows one tonuse a target-specific transmitted waveform/receiver filter to obtain anlarger signal-to-noise ratio (SNR) in the received signal thannconventional techniques. Generally, SNR of a received wave increases asnthe intensity of the transmit wave increases; however, because of thenFDA limitations placed on the amount of transmit energy, it is importantnto be able to make the most efficient use of the energy that isnavailable to obtain the best possible SNR in the received signal.nAdaptive ultrasonic measurement makes the most efficient use of thenenergy that is available by placing the maximum amount of energy in thenlargest target scattering mode. This results in more energy backscatternfrom a given target, which leads to a higher SNR in the receivednwaveform. Computer simulations of adaptive ultrasonic measurement ofnblood vessel diameter show that for a SNR of 0 dB in the transmittednwaveform, the standard deviation of the diameter measurements for ancustom-designed transmitted waveform is about two orders of magnitudenless than the standard deviation of the diameter measurements using morenconventional waveforms. Diameter and wall thickness measurementnexperiments were performed on a latex tube and a bovine blood vesselnusing both custom-made and conventionally used transmitted waveforms.nResults show that the adaptively designed waveform gives a smallernuncertainty in the measurements. The adaptive ultrasonic blood vesselndiameter and wall thickness measuring technique has potentialnapplications in examining vessels which are either too deep inside thenbody or too small for conventional techniques to be used, because of thenlow SNR in the received signal