The Quantitative Evaluation Of The CCA Wall With The Three-Membrane Structure By Using Coherent Plane-Wave Compounding Ultrasonography

As one of the most precise predictors for assessment of potential atherosclerosis to prevent future cardiovascular and cerebrovascular diseases in the medical diagnosis,changes in three-membrane structure of common carotid artery(CCA)wall and related dynamic features have a high clinical relevance.A common technique to measure the thicknesses of the membranes of CCA walls and related dynamic parameters is standard ultrasonography(SU),which scans objects by focused beam transmissions line-per-line.Because of the limited number of focus,vessel walls imaging by SU are discontinuous and fuzzy in the regions outside the focus,and thus the measurement accuracy and reliability for diagnosis indices based on the images are degraded.Plane-wave ultrasonography is conducted by transmitting plane(or unfocused)waves scanning over the whole region of interest by a single transmit event that is greatly increasing the frame-rate imaging.The coherent plane-wave compounding ultrasonography(CPCU)transmits plane waves with different angle deflection and adjusts the radio frequency echo signal for compounding to obtain the final radio frequency echo signal of the imaging area.Focus distribution of the interest regions is forming during the compounding process that is similar to the focusing effect of the SU.At the meantime the CPCU can maintain the high frame-rate imaging,obtain the high quality of B-image.It could be helpful to detect fine motion characteristics of 3MS of CCA wall and blood flow within vessels during the pulsation cycle.Thus,we propose to use the CPCU for scanning the CCA wall with three-membrane structure in present study.The focus points could be formed in the direction of the beam and its lateral after the superposition of the images during the coherent plane-wave compounding that can improve the detection performance.For quantitative evaluation and comparison of the scanning results,we establish a 3D scatterer model of CCA with three-membrane structure,and use Field II software to simulate radio frequency echo signals,and then B mode images were generated by using the SU and the CPCU,respectively.The thicknesses of intima,media and adventitia of the CCA wall are segmented from B mode images by using the threshold method,respectively.SonixTouch ultrasound system was used in clinical experiment to detect carotid artery vessels in 10 healthy subjects by using SU and CPCU.The thicknesses of intima,media and adventitia from corresponding B-mode ultrasound images are segmented by using the threshold method,and then results were statistically analyzed separately.The results based on 30 simulations show that the measurement accuracies for the thicknesses of three membranes based on the CPCU and the SU are not significantly different,but the successful rates of segmentation from images based on the CPCU are 11% and 12% higher than those based on the SU with center frequencies of 5 MHz and 10 MHz,respectively.Results of clinical experiments based on the CPCU and the SU also validate the simulation ones.It could be concluded based on experimental results that the images based on CPCU is more reliable and accurate to describe the three-membrane structure of the CCA wall.It could be helpful to exactly extract the axial and radial displacements of the three-membrane structure of the CCA wall during a cardiac cycle,and to improve the understanding of the physiology and the pathophysiology of the cardiovascular and cerebrovascular systems.