Department of Biomedical Engineering, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
IEEE Trans Biomed Eng. 2013 Feb;60(2):259-67. doi: 10.1109/TBME.2011.2171038. Epub 2011 Oct 10.
Focal liver lesions (FLLs) are usually quantitatively assessed by time-intensity curves (TICs) extracted from contrast-enhanced ultrasound (CEUS) image sequences. To overcome the subjectivity of manual region of interest (ROI) selection and automatically extract TICs, a novel factor analysis method called replace approximation (RA) was proposed. Assuming that the two factors are the arterial and portal vein phases, respectively, the high-dimensional time-series data are mapped into 1-D space, where the TIC at each pixel in the image becomes a point along a one-dimensional axis. The RA method aims to seek two apexes corresponding to the factor curves (the targeted TICs) in the subspace. This method was tested on 18 free-breathing datasets with respiratory motion correction. The experimental results showed that the RA method extracted physiological factor curves and the corresponding factor images efficiently. The mean correlation coefficient between the factor curves and the corresponding ROI measurements was 0.95 ± 0.02. Furthermore, the wash-in time ratio indexes of FLLs derived from the factor curves were used to perform parametric imaging, which could represent the characteristics of different types of FLLs. These results indicate that two-factor analysis has the potential to perform quantitative analysis of hepatic perfusion, which would be helpful to the differential diagnosis of FLLs.
肝脏局灶性病变（FLL）通常通过从超声造影（CEUS）图像序列中提取的时间强度曲线（TIC）进行定量评估。为了克服手动感兴趣区域（ROI）选择的主观性并自动提取 TIC，提出了一种称为替换逼近（RA）的新的因子分析方法。假设两个因素分别是动脉相和门静脉相，高维时间序列数据被映射到一维空间，其中图像中每个像素的 TIC 成为沿一维轴的一个点。RA 方法旨在寻找子空间中对应于因子曲线（目标 TIC）的两个顶点。该方法在 18 个具有呼吸运动校正的自由呼吸数据集上进行了测试。实验结果表明，RA 方法有效地提取了生理因子曲线和相应的因子图像。因子曲线与相应 ROI 测量值之间的平均相关系数为 0.95±0.02。此外，从因子曲线得出的 FLL 的流入时间比指数用于执行参数成像，其可以代表不同类型 FLL 的特征。这些结果表明，两因素分析具有进行肝灌注定量分析的潜力，这将有助于 FLL 的鉴别诊断。
