title: Large improvement of the electrical impedance of imaging and high-intensity focused ultrasound (HIFU) phased arrays using multilayer piezoelectric ceramics coupled in lateral mode.
abstract: With a change in phased-array configuration from one dimension to two, the electrical impedance of the array elements is substantially increased because of their decreased width (w)-to-thickness (t) ratio. The most common way to compensate for this impedance increase is to employ electrical matching circuits at a high cost of fabrication complexity and effort. In this paper, we introduce a multilayer lateral-mode coupling method for phased-array construction. The direct comparison showed that the electrical impedance of a single-layer transducer driven in thickness mode is 1/(n²(1/(w/t))²) times that of an n-layer lateral mode transducer. A large reduction of the electrical impedance showed the impact and benefit of the lateral-mode coupling method. A one-dimensional linear 32-element 770-kHz imaging array and a 42-element 1.45-MHz high-intensity focused ultrasound (HIFU) phased array were fabricated. The averaged electrical impedances of each element were measured to be 58 Ω at the maximum phase angle of -1.2° for the imaging array and 105 Ω at 0° for the HIFU array. The imaging array had a center frequency of 770 kHz with an averaged -6-dB bandwidth of approximately 52%. For the HIFU array, the averaged maximum surface acoustic intensity was measured to be 32.8 W/cm² before failure.
authors: Sunnybrook Health Science Centre, Universityof Toronto, Medical Biophysics, Toronto, ON, Canada. sjh4841@gmail.com
authors: Junho
authors: J
authors: Song
authors: Benjamin
authors: B
authors: Lucht
authors: Kullervo
authors: K
authors: Hynynen
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D017097:Electric Impedance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation*; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*