Jago J R, Whittingham T A
Regional Medical Physics Department, Newcastle General Hospital, UK.
Phys Med Biol. 1991 Nov;36(11):1515-27. doi: 10.1088/0031-9155/36/11/011.
The reconstruction of the speed-of-sound distribution within a target can be achieved by CT techniques from measurements on transmitted ultrasonic pulses. The mathematical relationship between speed-of-sound imaging and the conventional CT situation is explained. An experimental system, which has been developed to investigate speed-of-imaging and other forms of in-vivo ultrasound CT, is described, along with the techniques used for data acquisition and image reconstruction. These include measurement of pulse time-of-flight by the threshold or cross-correlation methods. Techniques for reducing artifacts in speed-of-sound images are also described, such as median filtering and modified Shepp-Logan filtering. These techniques have been used to obtain high quality speed-of-sound images of various phantoms. Images of tissue in-vitro have been less satisfactory, because of refraction and attenuation effects. Ways of overcoming these difficulties in an improved system are proposed.
通过对透射超声脉冲进行测量，利用CT技术可以实现目标体内声速分布的重建。文中解释了声速成像与传统CT情况之间的数学关系。描述了一个用于研究声速成像和其他形式的体内超声CT的实验系统，以及用于数据采集和图像重建的技术。这些技术包括通过阈值法或互相关法测量脉冲飞行时间。还介绍了减少声速图像伪影的技术，如中值滤波和改进的Shepp-Logan滤波。这些技术已被用于获取各种体模的高质量声速图像。由于折射和衰减效应，体外组织图像的效果不太理想。文中提出了在改进系统中克服这些困难的方法。
