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NANO2021-Nanoteknologi og nye materiale

Frontend and transducer technology for next generation cardiovascular ultrasound probes

Alternative title: Frontend og transducer teknologi for neste generasjon kardiovaskulære ultralyd prober

Awarded: NOK 7.3 mill.

Project Number:


Project Period:

2021 - 2025


The purpose of this project is to save human lives by improving the ultrasound image quality used for heart disease diagnosis and interventional guidance. This shall be obtained by integration of new transducer technology into existing ultrasound imaging platforms. The successful implementation of the CFRON project will improve image quality for patients with cardiovascular disease. Furthermore, it will provide the project partners with cutting-edge technology and knowledge to maintain an international leading position in cardiovascular ultrasound. Harmonic imaging (HI) has become default mode for cardiac ultrasound imaging due to its superior image quality, especially its ability to suppress reverberation noise. HI receives at twice the transmit frequency, utilizing nonlinear acoustic distortion as the pulse propagates in tissue. When using a conventional ultrasound probe for HI, the limited available bandwidth must be divided into two sub-bandwidths to support both the transmit and receive signals. Hence, the full transducer bandwidth cannot be used neither for transmit nor receive, making the existing solution sub-optimal. CMUT is an emerging technology that has been shown to provide a solution to this by offering a larger total bandwidth. The main technical challenges to be solved (and achievements during 2021) are: 1) Assembly and integration of piezoelectric and CMUT transducers in a single footprint. The first test-structures for the low frequency part of the hybrid transducer were made during 2021. Dummy versions of acoustic stacks were assembled and separated into array elements by using the dicing saw, to adapt and optimize the dicing process. In addition, FEM models have been developed to understand the results, in particular the influence from different kerf materials. 2) Efficient bonding between electronic (ASIC) and acoustic (CMUT/piezoelectric) modules. Here, dummy dies are designed and in fabrication, similarly to the configuration of the real devices but allowing for characterization of bonding quality such as electrical resistance and stray capacitance of interconnects. Such information is crucial to evaluate bonding technologies that can ensure the functionality of the real CMUT-ASIC assemblies. The specifications and design layouts of dummy ASIC and CMUT were in place. In parallel with the fabrication of these dummy devices, bonding materials and necessary equipment for bonding characterization are prepared. 3) Electro-acoustic modelling and characterization of hybrid piezoelectric-CMUT and CMUT transducers integrated to CMOS electronics, including backing and bonding layers. During 2021 initial feasibility, modelling and simulations have been performed to be able to accurately model the basic electronic properties of the combined acoustic stack.

The vision for this project is to save human lives by improving the ultrasound image quality used for heart disease diagnosis and interventional guidance. Such improvements are obtained by integration of new transducer technology with existing ultrasound imaging platforms. In brief, the main approaches of the project will i) bridge a conventional ultrasound transducer based on piezoelectric material (e.g. SC) with a new technique for transducer production, known as Piezoelectric Polyvinylidene Fluoride (PVDF), into a hybrid solution; and ii) integrate pure PVDF directly to specially designed ASIC. This will improve bandwidth and sensitivity of the transducers. The image quality will therefore be increased , increasing diagnostic confidence. The high integration level in 3D ultrasound medical probes makes it necessary to develop the in-probe necessary electronics to transmit and receive ultrasound pulses suitable for cardiac imaging. To enhance real time imaging, compact and reliable integration of the acoustic and electronic elements is crucial. For high quality imaging and cost-effective production processes, the ultrasound array is traditionally made with conventional single crystal (SC) material. The new technique for transducer production known as PVDF is highly cost effective. Direct connections between the acoustic elements and the ASICs with low signal parasitic capacitance are required using the new PVDF technology. This means 3D stacking of ASICs and transducers. Therefore, assembly technology for electro acoustic modules (EAM) in which the PVDF array is attached directly to the active electronics for transmit and receive contained in an ASIC is an innovative approach that will be studied in this project.

Publications from Cristin

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Funding scheme:

NANO2021-Nanoteknologi og nye materiale