眼组织超声回波频谱特性

眼组织回波频谱是设计眼科超声接收滤波器的基本参数。眼是一个不均匀的器官，所以无法用软组织平均声衰减系数对其回波频谱作出准确的估计。从声学的角度研究了人眼结构，用10 MHz单元超声换能器对人眼在体扫描，观察了回波频谱的变化规律，并在此基础上讨论了眼组织特性的影响。结果表明，球内回波的中心频率的变化很小，但是从眼底开始3~5 mm后的回波中心频率随着深度快速下降，平均斜率约为-0.16 MHz/mm。在探头通带范围内消除探头和电路的影响后观察组织的频谱特性，发现晶状体后囊频谱比较平坦而眼底组织的频谱有随频率升高的趋势。前者特性接近于高反射率的平面靶，而后者接近于瑞利散射子的特性。

The Spectrum of Ultrasound Echo Signal from Ocular Tissue

The spectral parameters of echo signals from eyes are critical for designing the receiving filter of the ophthalmological ultrasound device.It is inappropriate to estimate the echo spectra of the eyes with the averaged acoustic attenuation coefficient derived from soft tissues,because the ocular tissues are far from uniform.This paper studies the echo spectrum from human eyes in vivo.A 10 MHz ultrasonic transducer is used to scan the human eye and the result shows that the center frequencies of echo signal from eyeball are almost unchanged from the lens till retina,but decline rapidly with the depth about 3~5 mm behind the fundus from retina with the average slope about-0.16 MHz/mm.When the contributions of the probe and electronic elements are eliminated,the remaining spectrum of the posterior lens capsule is relatively flat which is similar to the feature of a plane reflector with high reflectivity,while the remaining spectrum of fundus present an ascending trend with the frequency,which is close to the characteristic expected for Rayleigh scatters.