High Performance Single Crystal Ultrasound Device for Medical Imaging

DESCRIPTION (provided by applicant): Ultrasonic imaging offers an important tool for clinical diagnosis. Compared to other imaging modalities, it is more cost-effective, non-invasive, capable of real-time operation, and portable while providing images of comparable quality and resolution. Low frequency (lt20 MHz) ultrasonic transducers have been widely used in areas including cardiac, pediatrics, abdomen, vascular and urology. On the other hand, high frequency (gt20 MHz) ultrasonic transducers produce images of high resolution in both axial and lateral directions, providing improved diagnosis for many diseases and better monitoring of medical treatments. It is gaining acceptance as a clinical tool for the examination of the anterior segment of the eye, skin and intravascular imaging. For an ultrasonic transducer the most critical component is the piezoelectric element, whose performance is largely determined by the electrical properties of the piezoelectric material. Piezoelectric single crystals such as lead magnesium niobate - lead titanate (PMN-PT) have superior dielectric and piezoelectric properties suitable for medical ultrasound with notable advantages of broad bandwidth and high sensitivity. PMN-PT crystal based transducers have demonstrated improved performance characteristics in both low and high frequency medical ultrasound applications. However, the thermal and electrical reliability of PMN-PT remains a concern. To improve the robustness and performance of crystal based transducers, we have recently developed a new piezoelectric single crystal in the ternary system lead indium niobate - lead magnesium niobate - lead titanate (PIN-PMN- PT). In addition to the excellent dielectric and piezoelectric properties, the ternary PIN-PMN-PT crystal exhibits improved thermal (TR/T up to 117 0C) and electrical (EC gt 5 kV/cm) stability compared to the binary PMN-PT crystal (TR/T ~ 85 0C, EC ~ 2.5 kV/cm). The ternary PIN-PMN-PT crystal system is promising for further property improvements of piezoelectric single crystals and crystal based transducers. In the Phase I project, we propose to grow ternary PIN-PMN-PT crystals of refined compositions with further improved thermal and electrical reliability while maintaining the advantages of piezoelectric single crystals. In addition, we will attempt to grow the new crystals along the [001] crystallographic direction and in large sizes, both of which are prerequisites for the future commercialization of the new crystals of improved properties. The dielectric, piezoelectric and elastic properties of the new crystal will be systematically characterized to provide key material parameters for its application. Low frequency (5-20 MHz) PIN-PMN-PT crystal transducer and high frequency composite PIN-PMN-PT transducer with 40-60 MHz will be fabricated in the phase I. The acoustic matching layers, backing layers and dicing pattern will be investigated in detail. Related characterizations of transducer will be carried out at the Resource Centre on Medical Ultrasonic Transducer Technology at the University of Southern California, the subcontract of this proposed Phase I research. The accomplishment of the proposed work will significantly improve the thermal stability and robustness for crystal based transducers of high performance. Success of this research and development will impact the diagnostic ultrasound imaging of low and high frequencies by improving bandwidth and sensitivity for transducers based on the traditional PZT ceramics or PVDF polymers while providing enhanced thermal and electrical robustness over PMN-PT based transducers. High frequency ultrasound can be used in the diagnosis and differentiation of ophthalmologic conditions such as intraocular tumors and orbital tumors. This diagnostic capability would benefit substantially from improved spatial resolution in three-dimensional C-mode images that would become available. This SBIR project will significantly improve the thermal and electrical reliability, and performance characteristics for low and high frequency medical ultrasonic transducers, and create a new avenue for eye imaging to the giant marketing of diagnostic ultrasound by MEMs technology. PUBLIC HEALTH RELEVANCE: This project focuses on the development of new ternary PIN-PMN-PT piezoelectric single crystals for biomedical ultrasound imaging applications. Broadband ultrasound transducers of lower frequency (e.g., 5-20 MHz) and high frequency (e.g., 40-60 MHz) using the new single crystal will be fabricated.