Talman J R, Lockwood G R
Department of Biomedical Engineering ND-20, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(1):117-24. doi: 10.1109/58.818754.
Developing transducer arrays for high frequency medical imaging is complicated because of the extremely small size and spacing of the array elements. For example, a 50 MHz linear phased array requires a center-to-center spacing of only 15 microm (one-half wavelength in water) to avoid the formation of grating lobes in the radiation pattern of the array. Fabricating an array with these dimensions is difficult using conventional technology. A split aperture design that permits much larger element spacing (3 to 4 times) while avoiding the formation of grating lobes is described. The 3-D radiation pattern of a 1.9x1.4 mm, 50-MHz split aperture linear phased array with 33 transmit elements and 33 receive elements has been evaluated theoretically. The azimuthal beam width is 90 microm at a distance of 4.0 mm. Grating lobes are suppressed by at least 60 dB at distances >4.0 mm (~f/2). The elevation beam width is 220 microm at 4.0 mm, and a useful depth of field over the axial range from 4 to 10 mm is obtained.
由于阵列元件的尺寸和间距极小，开发用于高频医学成像的换能器阵列十分复杂。例如，一个50兆赫的线性相控阵要求中心间距仅为15微米（水中的半个波长），以避免在阵列辐射方向图中形成栅瓣。使用传统技术制造具有这些尺寸的阵列很困难。本文描述了一种允许更大元件间距（3至4倍）同时避免形成栅瓣的裂孔设计。对一个具有33个发射元件和33个接收元件、尺寸为1.9×1.4毫米、频率为50兆赫的裂孔线性相控阵的三维辐射方向图进行了理论评估。在4.0毫米的距离处，方位波束宽度为90微米。在距离大于4.0毫米（约f/2）时，栅瓣被抑制至少60分贝。在4.0毫米处，仰角波束宽度为220微米，并且在4至10毫米的轴向范围内获得了有用的景深。
