Lizzi F L, Astor M, Feleppa E J, Shao M, Kalisz A
Riverside Research Institute, New York, NY 10036, USA.
Ultrasound Med Biol. 1997;23(9):1371-82. doi: 10.1016/s0301-5629(97)00200-7.
This study examines the statistics of ultrasonic spectral parameter images that are being used to evaluate tissue microstructure in several organs. The parameters are derived from sliding-window spectrum analysis of radiofrequency echo signals. Calibrated spectra are expressed in dB and analyzed with linear regression procedures to compute spectral slope, intercept and midband fit, which is directly related to integrated backscatter. Local values of each parameter are quantitatively depicted in gray-scale cross-sectional images to determine tissue type, response to therapy and physical scatterer properties. In this report, we treat the statistics of each type of parameter image for statistically homogeneous scatterers. Probability density functions are derived for each parameter, and theoretical results are compared with corresponding histograms clinically measured in homogeneous tissue segments in the liver and prostate. Excellent agreement was found between theoretical density functions and data histograms for homogeneous tissue segments. Departures from theory are observed in heterogeneous tissue segments. The results demonstrate how the statistics of each spectral parameter and integrated backscatter are related to system and analysis parameters. These results are now being used to guide the design of system and analysis parameters, to improve assays of tissue heterogeneity and to evaluate the precision of estimating features associated with effective scatterer sizes and concentrations.
本研究考察了用于评估多个器官组织微观结构的超声频谱参数图像的统计数据。这些参数源自射频回波信号的滑动窗口频谱分析。校准后的频谱以分贝表示，并采用线性回归程序进行分析，以计算频谱斜率、截距和中频拟合，后者与积分背向散射直接相关。每个参数的局部值以灰度横截面图像进行定量描绘，以确定组织类型、对治疗的反应以及物理散射体特性。在本报告中，我们针对统计上均匀的散射体处理每种参数图像的统计数据。为每个参数推导概率密度函数，并将理论结果与在肝脏和前列腺的均匀组织段中临床测量的相应直方图进行比较。在均匀组织段的理论密度函数和数据直方图之间发现了极好的一致性。在异质组织段中观察到与理论的偏差。结果表明了每个频谱参数和积分背向散射的统计数据如何与系统和分析参数相关。这些结果目前正用于指导系统和分析参数的设计，以改进组织异质性的检测，并评估与有效散射体大小和浓度相关的特征估计的精度。
