Departments of Biomedical Engineering, 351 Engineering Terrace, mail code 8904, 1210 Amsterdam Avenue, New York, NY 10027, USA.
Ultrason Imaging. 2010 Jul;32(3):154-76. doi: 10.1177/016173461003200304.
The objective of this study is to show that Harmonic Motion Imaging (HMI) can be used as a reliable tumor-mapping technique based on the tumor's distinct stiffness at the early onset of disease. HMI is a radiation-force-based imaging method that generates a localized vibration deep inside the tissue to estimate the relative tissue stiffness based on the resulting displacement amplitude. In this paper, a finite-element model (FEM) study is presented, followed by an experimental validation in tissue-mimicking polyacrylamide gels and excised human breast tumors ex vivo. This study compares the resulting tissue motion in simulations and experiments at four different gel stiffnesses and three distinct spherical inclusion diameters. The elastic moduli of the gels were separately measured using mechanical testing. Identical transducer parameters were used in both the FEM and experimental studies, i.e., a 4.5-MHz single-element focused ultrasound (FUS) and a 7.5-MHz diagnostic (pulse-echo) transducer. In the simulation, an acoustic pressure field was used as the input stimulus to generate a localized vibration inside the target. Radiofrequency (rf) signals were then simulated using a 2D convolution model. A one-dimensional cross-correlation technique was performed on the simulated and experimental rf signals to estimate the axial displacement resulting from the harmonic radiation force. In order to measure the reliability of the displacement profiles in estimating the tissue stiffness distribution, the contrast-transfer efficiency (CTE) was calculated. For tumor mapping ex vivo, a harmonic radiation force was applied using a 2D raster-scan technique. The 2D HMI images of the breast tumor ex vivo could detect a malignant tumor (20 x 10 mm2) surrounded by glandular and fat tissues. The FEM and experimental results from both gels and breast tumors ex vivo demonstrated that HMI was capable of detecting and mapping the tumor or stiff inclusion with various diameters or stiffnesses. HMI may thus constitute a promising technique in tumor detection (>3 mm in diameter) and mapping based on its distinct stiffness.
本研究旨在证明谐波运动成像（HMI）可作为一种可靠的肿瘤绘图技术，基于疾病早期肿瘤的明显硬度。HMI 是一种基于辐射力的成像方法，它在组织深处产生局部振动，根据产生的位移幅度估计组织的相对硬度。本文提出了有限元模型（FEM）研究，随后在组织模拟聚丙烯酰胺凝胶和离体人乳腺癌肿瘤中进行了实验验证。本研究比较了在四种不同凝胶硬度和三个不同球形包含物直径下模拟和实验中产生的组织运动。凝胶的弹性模量分别使用机械测试进行单独测量。在 FEM 和实验研究中使用了相同的换能器参数，即 4.5MHz 单元件聚焦超声（FUS）和 7.5MHz 诊断（脉冲回波）换能器。在模拟中，声压场被用作输入刺激，在目标内部产生局部振动。然后使用二维卷积模型模拟射频（rf）信号。在模拟和实验 rf 信号上执行一维互相关技术，以估计由谐波辐射力产生的轴向位移。为了测量位移轮廓估计组织硬度分布的可靠性，计算了对比度传递效率（CTE）。为了进行离体肿瘤的映射，使用二维光栅扫描技术施加谐波辐射力。离体乳腺癌的 2DHMI 图像可以检测到恶性肿瘤（20x10mm2），周围是腺体和脂肪组织。凝胶和离体乳腺癌的 FEM 和实验结果均表明，HMI 能够检测和绘制具有各种直径或硬度的肿瘤或硬包含物。因此，HMI 可能构成一种基于其独特硬度的肿瘤检测（直径>3mm）和绘图的有前途的技术。
