Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Jan;57(1):214-28. doi: 10.1109/TUFFC.2010.1400.
Correction of aberration in ultrasound imaging uses the response of a point reflector or its equivalent to characterize the aberration. Because a point reflector is usually unavailable, its equivalent is obtained using statistical methods, such as processing reflections from multiple focal regions in a random medium. However, the validity of methods that use reflections from multiple points is limited to isoplanatic patches for which the aberration is essentially the same. In this study, aberration is modeled by an offset phase screen to relax the isoplanatic restriction. Methods are developed to determine the depth and phase of the screen and to use the model for compensation of aberration as the beam is steered. Use of the model to enhance the performance of the noted statistical estimation procedure is also described. Experimental results obtained with tissue-mimicking phantoms that implement different models and produce different amounts of aberration are presented to show the efficacy of these methods. The improvement in b-scan resolution realized with the model is illustrated. The results show that the isoplanatic patch assumption for estimation of aberration can be relaxed and that propagation-path characteristics and aberration estimation are closely related.
超声成象中的象差校正采用点反射器或其等效物的响应来描述象差。由于通常不存在点反射器，所以采用统计方法获得其等效物，例如对随机介质中多个焦点的反射进行处理。然而，利用多点反射的方法的有效性仅限于等晕区，在等晕区内象差基本上是相同的。在本研究中，采用偏移相位屏来模拟象差，以放宽等晕限制。提出了确定相位屏的深度和相位的方法，并在波束转向时利用该模型进行象差补偿。还描述了利用该模型来增强所提到的统计估计过程的性能的方法。为了表明这些方法的有效性，给出了使用不同模型和产生不同量象差的组织模拟体模获得的实验结果。说明了用该模型实现的 B 扫描分辨率的提高。结果表明，可以放宽对估计象差的等晕区假设，并且传播路径特性和象差估计密切相关。
