Research On Coherent Plane Wave Compounding Imaging Algorithm Based On Adaptive Weighting Factors

Ultrasound imaging has become an important tool in medical imaging examination for its safety and real-time capabilities.Conventional ultrasound line-by-line scanning mode requires multiple emission focusing to sweep the imaging region,which leads to a low frame rate and it is not suitable for high speed imaging applications such as transient Elastography and brain functional imaging.Ultrasound plane wave imaging(PWI)has proven itself a reliable way for realizing ultra-fast ultrasound imaging.However,PWI usually has poor imaging quality because of the lack of focusing in the process of pulse emission.Coherent plane wave compounding(CPWC)was proposed to improve the imaging quality of PWI by superimposing the imaging results of plane waves at different angles.Traditional CPWC simply sums the echo data of plane waves with different transmitting angles to get the image output,however,the data correlation information of different emissions is not considered.Therefore,some adaptive techniques used in conventional ultrasound imaging scheme has been introduced into the compounding procedure to further improve the performance of CPWC.In this paper,two new adaptive factors are proposed to improve CPWC imaging quality by weighting the coherent sum output of CPWC.The first one is called Short-lag Coherent Factor(SLCF).SLCF uses the angular difference parameter to ascertain the order of the coherence factor and calculates the coherence factor based on the plane-waves with small angular difference.The second one is called Zero-crossing Factor(ZF).ZF is calculated based on the sign change of imaging results of two adjacent plane waves with different transmitting angles,which can reflect the coherence of background organization more accurately.The SLCF and ZF is tested by public data set.Simulated and experimental results show that SLCF algorithm can improve the imaging quality in terms of lateral resolution and contrast ratio(CR),compared with CPWC.In addition,in comparison with coherence factor(CF),SLCF can achieve better background speckle quality and it has lower computational complexity.To evaluate the performance of ZF,experiments are conducted on both phantom and in-vivo artery data,and results show that ZF can provide higher image contrast and resolution than the conventional CPWC.Compared with CF weighting method,ZF weighting can reduce background noise and preserve the speckle pattern,which leads to a better image quality of background tissue.The two adaptive weighting factors proposed in this paper use less computation and improve the imaging quality of CPWC,which is meaningful for clinical diagnosis of ultrasound.