The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.
The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.
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换能器几何形状对传统医学超声诊断骨成像常见伪影的影响。
DOI：
10.1109/tuffc.2012.2301
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Hossack,JohnA
中科院分区：
文献类型：
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作者：
MauldinJr,FWilliam;Owen,Kevin;Tiouririne,Mohamed;Hossack,JohnA
医用超声的便携性、低成本和非电离辐射表明，它具有替代X射线进行骨成像的潜力。然而，当传统的超声成像系统用于骨成像时，临床可接受性往往受到远离声束主轴的反射产生的伪影的限制。本文从仿真和实验两方面研究了离轴伪影的物理来源以及换能器几何形状对离轴伪影的影响。与绕射理论一致，采样的线阵几何结构与单元件活塞几何结构相比，具有更高的离轴能量，因此显示出更高水平的伪影信号。仿真和实验结果表明，随着中心频率的增加，离轴到主声束(即栅瓣)的能量垂直入射到离轴表面，以及离轴表面为镜面反射而不是漫射时，线阵几何形状显示出更多的伪影信号。对用于模拟镜面反射的模拟模型进行了实验验证，实验结果与模拟峰值反射对比度的相关系数为0.97。在体外实验中，与线性阵列相比，活塞几何结构在成像动物脊柱的棘突和椎板间隙时，平均对比度分别提高了4d B和6.2d B。这项工作表明，离轴反射是超声图像伪影的主要来源，特别是在包含镜面反射(即骨骼或类骨)对象的环境中。对离轴表面反射敏感度降低的换能器几何结构，例如活塞换能器几何结构，图像伪影显著减少。
The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the lineararray geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bonelike) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.