The world market for medical ultrasound transducers exceeds one billion dollars annually, with an average cost to the physician exceeding $5,000 for each transducer. Transducers are made almost exclusively from lead zirconate titanate (PZT), a ceramic which has undesirable narrow bandwidth characteristics that limit the image's axial resolution. A challenge by Capacitive Micromachined Ultrasonic Transducers (CMUT) over the last ten years has not made any impact on PZT's exclusivity in this large market. This application, to make transducers from Polyvinylidene (PVDF), is grounded in a proven model and formal analysis which finds that multiple layers of low cost PVDF when stacked in a unique pattern (Switched Barker Code Transducer (SBCT)), preserves the material's extremely wide bandwidth and overcomes the PVDF's low dielectric characteristics in an innovative electronic coupling method. The SBCT modeling further predicts the pulse-echo sensitivity of an eleven layer SBCT to be equal or better than PZT. The lithographically produced multi-element transducer's layers will be bonded by newly developed "nanoglue" which provides a nanometer layer separation and will facilitate the simple low cost assembly of thousands of transducers per hour by commercially available pick and place equipment. Transducers manufactured by the proposed method can replace PZT transducers in all 25 of the applications where transducers are in production today, from OB/GYN to disposable intra cardiac transducers. This method also yields improvements in resolution, sensitivity, and cost. Simple lithographic methods will define the transducer's characteristics of size, number of elements, shape and use. This will allow many custom transducers to be constructed at very low cost for frequencies from 100 KHz through to 40 MHz. The speckle that is a characteristic of today's ultrasound images will become more detailed due to the much higher bandwidth, but simultaneous frequency compounding will also become much more effective rendering clearer images of overall higher resolution and deeper penetration. Modalities such as elastography will benefit greatly in diagnostic specificity from this bandwidth improvement. A thirteen layer 15 MHz SBCT PVDF transducer will be constructed in this project which can be compared with the company's production 15 MHz PZT transducer (60% bandwidth) that is primarily used in preclinical elastography and photoacoustics, where bandwidth of transmission and reception can be quantitatively and separately evaluated. This proposed method will allow transducers to be constructed for tens of dollars which greatly reduces the projected physician's cost, and this, plus the projected gains in resolution, can be expected to have a major effect on the quality and cost of health care.
In this project medical ultrasound transducers will be constructed by a multilayer plastic (PVDF) using Barker Coded arrangement that provides equivalent sensitivity to today's state of the art ceramic (PZT) transducers at less than 1/10 of the cost and provides extremely high bandwidth for superior axial resolution that wil find application in the new fields of elastography and photoacoustics. The method can be applied to all transducers of all applications by low cost lithography and production an be accommodated in thousands per hour by commercial electronic pick and place machines. The current $ 1 billion spent on medical transducers per year will be greatly reduced while providing clearer, higher resolution ultrasound images with higher diagnostic use.