Fabrication and performance of a 10 MHz annular array based on PMN-PT single crystal for medical imaging

In this paper, a novel 7 mm diameter, 8-elements, 10MHz electrical focusing 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO₃ (PMN-PT) single crystal annular array using equal area elements, has been designed and evaluated. Separation of elements was achieved using 355 nm ultraviolet laser ablation techniques. A novel electrical interconnection strategy for high frequency array elements was implemented. After the transducer was attached to the electric connection board and packaged, the annual array was tested in a pulse/echo arrangement, whereby the center frequency, bandwidth and two-way insertion loss were measured for each annulus. The annular array produced pulses with a centre frequency of 10 MHz and nearly 78 % bandwidth at -6dB. The average insertion loss was -27 dB at centre frequency. The improved lateral resolution and depth of field from the 50^μm aluminum wire phantom image were observed, in which the axial and lateral resolutions at 12 mm depth are found to be 650 ^μm and 188 ^μm, respectively. Ultrasonic images of cattle eyes also were obtained with the 10-MHz annual array transducer. In the anterior portion of cattle eye it can be seen that the cornea and iris are well distinguishable. For the clinical ophthalmologic application, the B/D scan is not desirable because the transducer is moved in the axial direction, increasing the possibility of damaging the surface of the cornea. This eight element annular transducer is promising for ophthalmology and dermatology ultrasonic imaging and other high frequency ultrasonic diagnostics applications.