非线性时空调制滤波器的定量图像质量分析。

Quantitative image quality analysis of a nonlinear spatio-temporal filter.

机构信息

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.

出版信息

IEEE Trans Image Process. 2001;10(2):288-95. doi: 10.1109/83.902293.

Abstract

Digital temporal and spatial filtering of fluoroscopic image sequences can be used to improve the quality of images acquired at low X-ray exposure. In this study, we characterized a nonlinear edge preserving, spatio-temporal noise reduction filter, the bidirectional multistage (BMS) median filter of Arce (1991). To assess image quality, signal detection and discrimination experiments were performed on stationary targets using a four-alternative forced-choice paradigm. A measure of detectability, d', was obtained for filtered and unfiltered noisy image sequences at different signal amplitudes. Filtering gave statistically significant, average d' improvements of 20% (detection) and 31% (discrimination). A nonprewhitening detection model modified to include the human spatio-temporal visual system contrast-sensitivity underestimated enhancement, predicting an improvement of 6%. Pixel noise standard deviation, a commonly applied image quality measure, greatly overestimated effectiveness giving 67% improvement in d'. We conclude that human testing is required to evaluate the filter effectiveness and that human perception models must be improved to account for the spatio-temporal filtering of image sequences.

摘要

数字时空间滤波技术可用于改善低 X 射线照射条件下获取的图像质量。本研究中，我们对非线性边缘保持、时空降噪滤波器，即 Arce（1991）提出的双向多阶段（BMS）中值滤波器进行了特征描述。为了评估图像质量，我们使用四择一强迫选择范式对静止目标进行了信号检测和辨别实验。对于不同幅度的信号，我们获得了经滤波和未经滤波的噪声图像序列的可检测性度量 d'。滤波处理在检测和辨别方面平均分别带来了 20%和 31%的显著性能提升。为了包含人类时空视觉系统对比敏感度，我们对未预白化的检测模型进行了修改，该模型低估了增强效果，预测可提升 6%。作为常用的图像质量度量标准，像素噪声标准差极大地高估了滤波器的有效性，使得 d'提升了 67%。我们的结论是，需要进行人类测试来评估滤波器的有效性，并且必须改进人类感知模型以考虑到图像序列的时空滤波。