Department of Micro- and Nanotechnology, DTU Nanotech, Technical University of Denmark, Building 345C, DK-2800 Kgs. Lyngby, Denmark.
Sound Technology Inc., Analogic Ultrasound Group, State College, PA 16803, USA.
Ultrasonics. 2018 Aug;88:97-105. doi: 10.1016/j.ultras.2018.02.001. Epub 2018 Mar 24.
The purpose of this work is to investigate compound lenses for row-column-addressed (RCA) ultrasound transducers for increasing the field-of-view (FOV) to a curvilinear volume region, while retaining a flat sole to avoid trapping air between the transducer sole and the patient, which would otherwise lead to unwanted reflections. The primary motivation behind this research is to develop a RCA ultrasound transducer for abdominal or cardiac imaging, where a curvilinear volume region is a necessity. RCA transducers provide 3-D ultrasound imaging with fewer channels than fully-addressed 2-D arrays (2N instead of N), but they have inherently limited FOV. By increasing the RCA FOV, these transducers can be used for the same applications as fully-addressed transducers while retaining the same price range as conventional 2-D imaging due to the lower channel count. Analytical and finite element method (FEM) models were employed to evaluate design options. Composite materials were developed by loading polymers with inorganic powders to satisfy the corresponding speed of sound and specific acoustical impedance requirements. A BiO powder with a density of 8.9g/cm was used to decrease the speed of sound of a room temperature vulcanizing (RTV) silicone, RTV615, from 1.03mm/μs to 0.792mm/μs. Using micro-balloons in RTV615 and a urethane, Hapflex 541, their speeds of sound were increased from 1.03mm/μs to 1.50mm/μs and from 1.52mm/μs to 1.93mm/μs, respectively. A diverging add-on lens was fabricated of a BiO loaded RTV615 and an unloaded Hapflex 541. The lens was tested using a RCA probe, and a FOV of 32.2° was measured from water tank tests, while the FEM model yielded 33.4°. A wire phantom with 0.15mm diameter wires was imaged at 3MHz down to a depth of 14cm using a synthetic aperture imaging sequence with single element transmissions. The beamformed image showed that wires outside the array footprint were visible, demonstrating the increased FOV.
这项工作的目的是研究用于行-列寻址（RCA）超声换能器的复合透镜，以将视场（FOV）扩展到弯曲体积区域，同时保持平面鞋底，以避免换能器鞋底和患者之间夹住空气，否则会导致不必要的反射。这项研究的主要动机是开发一种用于腹部或心脏成像的 RCA 超声换能器，其中弯曲体积区域是必需的。RCA 换能器提供的 3-D 超声成像所需的通道数比完全寻址的 2-D 阵列少（2N 而不是 N），但它们的固有 FOV 有限。通过增加 RCA 的 FOV，这些换能器可以用于与完全寻址换能器相同的应用，同时由于通道数较低，其价格范围与传统的 2-D 成像保持一致。采用分析和有限元方法（FEM）模型来评估设计方案。通过在聚合物中加载无机粉末来开发复合材料，以满足相应的声速和特定声阻抗要求。使用密度为 8.9g/cm 的 BiO 粉末将室温硫化（RTV）硅酮 RTV615 的声速从 1.03mm/μs 降低到 0.792mm/μs。在 RTV615 和聚氨酯 Hapflex 541 中使用微球，它们的声速分别从 1.03mm/μs 增加到 1.50mm/μs 和从 1.52mm/μs 增加到 1.93mm/μs。使用 BiO 负载的 RTV615 和未加载的 Hapflex 541 制造了发散附加透镜。使用 RCA 探头对透镜进行了测试，从水箱测试中测量到 32.2°的 FOV，而 FEM 模型产生了 33.4°。使用合成孔径成像序列和单个元件传输，在 3MHz 下对直径为 0.15mm 的金属丝线进行了成像，深度可达 14cm。波束形成的图像显示，阵列足迹之外的金属丝是可见的，这表明 FOV 增加了。
