Analysis of contrast in images generated with transient acoustic radiation force
Analysis of contrast in images generated with transient acoustic radiation force
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DOI：
10.1016/j.ultrasmedbio.2005.08.008
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发表时间：
2006-01-01
影响因子：
2.9
通讯作者：
Trahey, G
中科院分区：
文献类型：
--
作者：
Nightingale, K;Palmeri, M;Trahey, G
几种机械成像方法正在研究中，使用聚焦超声（US）作为机械激励源。然后生成组织对该局部激励的响应的图像。一种这样的方法，声辐射力脉冲（ARFI）成像，利用商业US系统上的单个US换能器来发射简短的、高能量的聚焦声脉冲以在组织中产生辐射力，并且利用基于相关性的US方法来检测所产生的组织位移。局部位移反映了组织的相对力学性质。这些图像的分辨率与传统B模式成像的分辨率相当。组织对聚焦辐射力激励的响应是复杂的并且取决于组织几何形状、强制函数几何形状（即，激励区域或ROE）以及组织机械和声学特性。已使用不同的系统、系统配置和组织模拟体模进行了使用实验验证模型和体模实验的有限元法（FEM）模拟，以确定其对图像质量的影响。通过病变对比度评估图像质量。由于ARFI激发的动态性质，病变对比度是时间依赖性的。对比度的球形夹杂物是最高的力停止后，随着时间的推移postforce，然后反转，由于剪切波与内部边界的相互作用，病变和背景和惯性效应之间的剪切模量的差异。在力停止后立即生成的图像中，对比度不随施加的力而变化，随病变硬度而增加，并随ROE尺寸相对于成像结构尺寸的减小而增加。这些研究表明，随着ROE尺寸的减小，辐射力生成图像的对比度将得到改善;然而，帧速率和热考虑因素与小ROE尺寸存在权衡。
Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force in tissue and correlation-based US methods to detect the resulting tissue displacements. Local displacements reflect relative mechanical properties of tissue. The resolution of these images is comparable with that of conventional B-mode imaging. The response of tissue to focused radiation force excitation is complex and depends upon tissue geometry, forcing function geometry (i.e., region of excitation, or ROE) and tissue mechanical and acoustic properties. Finite element method (FEM) simulations using an experimentally validated model and phantom experiments have been performed using varying systems, system configurations and tissue-mimicking phantoms to determine their impact on image quality. Image quality is assessed by lesion contrast. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally-dependent. Contrast of spherical inclusions is highest immediately after force cessation, decreases with time postforce and then reverses, due to shear wave interaction with internal boundaries, differences in shear modulus between lesions and background and inertial effects. In images generated immediately after force cessation, contrast does not vary with applied force, increases with lesion stiffness and increases as the ROE size decreases relative to the size of the structure being imaged. These studies indicate that improved contrast in radiation force-generated images will be achieved as ROE size decreases; however, frame rate and thermal considerations present trade-offs with small ROE size.