声速误差对平面波成像质量的影响

在医学超声成像系统中,大多都采用假定声速进行成像。假定声速和真实声速的误差会造成超声图像的空间相位偏移和散焦,降低图像质量。定量分析了声速误差对平面波成像质量的影响。通过Matlab里的k-wave仿真工具箱,获取仿真数据,假定不同声速,通过延迟累加波束形成技术来获得二维超声图像。通过对比度(Contrast Ratio,CR)、对比噪声比(Contrast-to-Noise Ratio,CNR)和点扩散函数(Point Spread Function,PSF)来评价平面波成像质量。在均一介质中,假定了21组不同的声速,其误差范围为±100 m/s;在复杂介质中,选择6种不同的乳腺模型,假定声速为1540 m/s,通过CR、CNR、PSF分别定量分析成像质量。在均一介质中,随着声速误差的增大,成像质量变差。在复杂介质中,成像质量比均一介质中使用正确声速的成像质量差。

Influence of Sound Velocity Error on Plane Wave Imaging Quality

In medical ultrasound imaging systems,the assumed sound speed is generally used for imaging.The error between assumed velocity and real sound velocity will cause the spatial phase shift and defocus of the ultrasound image,which will reduce the quality of the image.The influence of sound velocity error on plane wave imaging quality is quantitatively analyzed.The simulation data is obtained through the k-wave simulation toolbox in Matlab,and the 2D ultrasound images are obtained by delay-and-sum with different assumed sound speed.Contrast ratio(CR),contrast-to-noise(CNR) and point spread function(PSF) are used to evaluate the quality of plane wave imaging.In a homogeneous medium,21 groups of different sound speeds are assumed,and the error range is ±100 m/s.In a complex medium,6 groups of different mammary gland models are selected,and the sound velocity is assumed to be 1540 m/s,the plane wave imaging is quantitatively analyzed by CR,CNR,PSF.In a homogeneous medium,the imaging quality deteriorates as the sound velocity error increases.In a complex medium,its imaging quality is worse than that of using the correct sound speed in homogeneous media.