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Development of single-fiber piezocomposite transducers for 3D ultrasound computer tomography

: Zapf, Michael; Hohlfeld, Kai; Ruiter, Nicole V.; Pfistner, Patrick; Dongen, Koen W.A. van; Gemmeke, Hartmut; Michaelis, Alexander; Gebhardt, Sylvia


Advanced engineering materials 20 (2018), No.12, Art. 1800423
ISSN: 1438-1656
ISSN: 1615-7508
Deutsche Forschungsgemeinschaft DFG
Sonderforschungsbereich/Transregio 39 "Großserienfähige Produktionstechnologien für leichtmetall- und faserverbundbasierte Komponenten mit integrierten Piezosensoren und -aktoren; TRR 39/3, subproject K04
Entwicklung integrierter einzelfaserbasierter Ultraschallwandler für die 3D-Ultraschall-Computertomographie (3D-USCT)
Journal Article
Fraunhofer IKTS ()
ultrasound computer tomography; piezocomposite; ultrasonic transducer; piezoelectric fiber

Ultrasound Computer Tomography (USCT) medical imaging is a promising approach for early detection of breast cancer. At Karlsruhe Institute of Technology (KIT) a 3D USCT system is developed. The system operates 2041 ultrasound transducers in a semi-ellipsoidal aperture surrounding a region of interest (ROI) of 10 cm x 10 cm x 10 cm. Results from a first patient study reveal the requirement of a significantly increased ROI to cover bodily variations. Design considerations and simulations show a demand for circular transducers of approximately 500 μm diameter, increasing the opening angle of the transducers to approximately 60°. Piezofiber composite technology is predestinated to simply provide circular transducers of the required dimensions. Moreover, piezocomposites based on single PZT (lead zirconate titanate Pb[ZrxTi1-x]O3) fibers enable a cost-effective and series-production alternative to currently used dice-and-fill composites. A transducer design is presented which utilizes individually arranged single piezoceramic fibers with 460 µm in diameter within piezocomposite discs. As result fibers are independently addressable as single transducer elements allowing for the desired transducer arrangement. The electrical performance of each piezoceramic fiber is determined proofing a strong dependence of coupling coefficient and resonance frequency from transducer thickness. In further processing, the piezocomposite discs are connected to printed circuits, integrated into a cylindrical housing and backfilled with polyurethane. Ultrasound characteristics such as sound pressure and opening angle are evaluated quantitatively. The transducer opening angles are in the expected range, desired center frequency is achieved and bandwidth preserved compared to former dice-and-fill transducers.