Zhu Q, Steinberg B D, Arenson R
Valley Force Research Center, Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia 19104, USA.
J Acoust Soc Am. 1995 Aug;98(2 Pt 1):694-705. doi: 10.1121/1.413563.
Ultrasonic waves propagating through soft tissue experience wavefront distortion. Adaptive wavefront compensation algorithms attempt to correct such distortion. A valuable design parameter is the isoplanatic patch size of the imaging medium. Its lateral extent is the FWHM of the correlation function. The range extent is defined similarly. The significance of the isoplanatic patch is that a new wavefront correction vector must be obtained whenever the ultrasound beam is moved a patch length. This paper reports measurements of wavefront correlation functions as well as statistics of the lateral correlation distance rho d (half the FWHM) within the female breast obtained from a population of 22 women (44 breasts) and measured at 3 and 4 MHz with a large acoustic aperture (9.6 cm). A set of complex wavefronts radiated from single pointlike sources was measured from the opposing side of the breast. The propagation distance was 12 cm. rho d is the distance between two sources at which the correlation between their wavefronts drops to 0.5. The mean value at 3 MHz was found to be less than 1.5 mm for the premenopausal dense breast, 2.5 mm for the premenopausal fatty breast, and 2.0 mm for the postmenopausal breast. The mean value dropped by a factor of 2 at 4 MHz for a group consisting of premenopausal fatty and postmenopausal breasts.
在软组织中传播的超声波会经历波前畸变。自适应波前补偿算法试图校正这种畸变。一个重要的设计参数是成像介质的等晕区尺寸。其横向范围是相关函数的半高宽。范围范围的定义类似。等晕区的重要性在于，每当超声束移动一个区长度时，就必须获得一个新的波前校正向量。本文报告了从22名女性（44个乳房）群体中获得的女性乳房内波前相关函数的测量结果以及横向相关距离ρd（半高宽的一半）的统计数据，并在3和4MHz频率下使用大孔径（9.6cm）进行测量。从乳房的另一侧测量了从单个点状源辐射出的一组复波前。传播距离为12cm。ρd是两个源之间的距离，在该距离处它们的波前之间的相关性降至0.5。发现绝经前致密乳房在3MHz时的平均值小于1.5mm，绝经前脂肪乳房为2.5mm，绝经后乳房为2.0mm。对于绝经前脂肪和绝经后乳房组成的组，在4MHz时平均值下降了2倍。
