Fang Jui, Zhou Zhuhuang, Chang Ning-Fang, Wan Yung-Liang, Tsui Po-Hsiang
Ph. D. Program in Biomedical Engineering, College of Engineering, Chang Gung University, Taoyuan, Taiwan.
College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China; Faculty of Information Technology, Beijing University of Technology, Beijing, China.
Ultrasonics. 2018 Jul;87:91-102. doi: 10.1016/j.ultras.2018.02.015. Epub 2018 Feb 15.
Hepatic steatosis is an abnormal state where excess lipid mass is accumulated in hepatocyte vesicles. Backscattered ultrasound signals received from the liver contain useful information regarding the degree of steatosis in the liver. The homodyned-K (HK) distribution has been demonstrated as a general model for ultrasound backscattering. The estimator based on the first three integer moments (denoted as "FTM") of the intensity has potential for practical applications because of its simplicity and low computational complexity. This study explored the diagnostic performance of HK parametric imaging based on the FTM method in the assessment of hepatic steatosis. Phantom experiments were initially conducted using the sliding window technique to determine an appropriate window size length (WSL) for HK parametric imaging. Subsequently, hepatic steatosis was induced in male Wistar rats fed a methionine- and choline-deficient (MCD) diet for 0 (i.e., normal control), 1, 2, 4, 6, and 8 weeks (n = 36; six rats in each group). After completing the scheduled MCD diet, ultrasound B-mode and HK imaging of the rat livers were performed in vivo and histopathological examinations were conducted to score the degree of hepatic steatosis. HK parameters μ (related to scatterer number density) and k (related to scatterer periodicity) were expressed as functions of the steatosis stage in terms of the median and interquartile range (IQR). Receiver operating characteristic (ROC) curve analysis was conducted to assess the diagnostic performance levels of the μ and k parameters. The results showed that an appropriate WSL for HK parametric imaging is seven times the pulse length of the transducer. The median value of the μ parameter increased monotonically from 0.194 (IQR: 0.18-0.23) to 0.893 (IQR: 0.64-1.04) as the steatosis stage increased. Concurrently, the median value of the k parameter increased from 0.279 (IQR: 0.26-0.31) to 0.5 (IQR: 0.41-0.54) in the early stages (normal to mild) and decreased to 0.39 (IQR: 0.29-0.45) in the advanced stages (moderate to severe). The areas under the ROC curves obtained using (μ, k) were (0.947, 0.804), (0.914, 0.575), and (0.813, 0.604) for the steatosis stages of ≥mild, ≥moderate, and ≥severe, respectively. The current findings suggest that ultrasound HK parametric imaging based on FTM estimation has great potential for future clinical diagnoses of hepatic steatosis.
肝脂肪变性是一种异常状态，即肝细胞囊泡中积累了过量的脂质。从肝脏接收到的后向散射超声信号包含有关肝脏脂肪变性程度的有用信息。同相检波-K（HK）分布已被证明是超声后向散射的通用模型。基于强度的前三个整数矩（表示为“FTM”）的估计器因其简单性和低计算复杂度而具有实际应用潜力。本研究探讨了基于FTM方法的HK参数成像在评估肝脂肪变性中的诊断性能。最初使用滑动窗口技术进行体模实验，以确定HK参数成像的合适窗口大小长度（WSL）。随后，给雄性Wistar大鼠喂食蛋氨酸和胆碱缺乏（MCD）饮食0（即正常对照）、1、2、4、6和8周（n = 36；每组6只大鼠），诱导肝脂肪变性。在完成预定的MCD饮食后，对大鼠肝脏进行体内超声B模式和HK成像，并进行组织病理学检查以对肝脂肪变性程度进行评分。HK参数μ（与散射体数量密度有关）和k（与散射体周期性有关）根据中位数和四分位数间距（IQR）表示为脂肪变性阶段的函数。进行受试者操作特征（ROC）曲线分析以评估μ和k参数的诊断性能水平。结果表明，HK参数成像的合适WSL是换能器脉冲长度的7倍。随着脂肪变性阶段的增加，μ参数的中位数从0.194（IQR：0.18 - 0.23）单调增加到0.893（IQR：0.64 - 1.04）。同时，k参数的中位数在早期阶段（正常至轻度）从0.279（IQR：0.26 - 0.31）增加到0.5（IQR：0.41 - 0.54），在晚期阶段（中度至重度）降至0.39（IQR：0.29 - 0.45）。对于≥轻度、≥中度和≥重度脂肪变性阶段，使用（μ，k）获得的ROC曲线下面积分别为（0.947，0.804）、（0.914，0.575）和（0.813，0.604）。目前的研究结果表明，基于FTM估计的超声HK参数成像在未来肝脂肪变性的临床诊断中具有很大潜力。
