Wear K A, Wagner R F, Insana M F, Hall T J
FDA, Rockville, MD.
IEEE Trans Ultrason Ferroelectr Freq Control. 1993;40(1):50-8. doi: 10.1109/58.184998.
The problem of estimation of mean scatterer spacing in an object containing regularly spaced structures is addressed. An autoregressive (AR) spectral estimation method is compared with a conventional fast Fourier transform (FFT)-based approach for this task. Regularly spaced structures produce a periodicity in the power spectrum of ultrasonic backscatter. This periodicity is manifested as a peak in the cepstrum. A phantom was constructed for comparison of the two methods. It contained regularly spaced nylon filaments. It also contained randomly positioned glass spheres that produced incoherent backscatter. In an experiment in which this target was interrogated using broadband ultrasound, the AR spectral estimate offered considerable improvement over the FFT when the analysis gate length was on the order of the structural dimension. Advantages included improved resolution, reduction in bias and variance of scatterer spacing estimates, and greater resistance to ringing artifacts. Data were also acquired from human liver in vivo. AR spectral estimates on human data exhibited a decreased dependence on gate length. These results offer promise for enhanced spatial resolution and accuracy in ultrasonic tissue characterization and nondestructive evaluation of materials.
本文探讨了在包含规则间隔结构的物体中估计平均散射体间距的问题。针对此任务，将自回归（AR）谱估计方法与传统的基于快速傅里叶变换（FFT）的方法进行了比较。规则间隔结构在超声背散射功率谱中产生周期性。这种周期性在倒谱中表现为一个峰值。构建了一个体模用于比较这两种方法。它包含规则间隔的尼龙丝。还包含随机放置的产生非相干背散射的玻璃球。在使用宽带超声对该目标进行探测的实验中，当分析门长度约为结构尺寸时，AR谱估计相对于FFT有显著改进。优点包括分辨率提高、散射体间距估计的偏差和方差减小以及对振铃伪像的更强抗性。还从人体肝脏体内获取了数据。人体数据的AR谱估计对门长度的依赖性降低。这些结果为提高超声组织表征和材料无损评估中的空间分辨率和准确性带来了希望。
