Ultrasound-based imaging in medical technology and industrial metrology#
Applications for medicine and health
In medical technology and industrial measurement technology, sonography is an established field of analysis. The use of ultrasonic transducers in the form of ultrasonic arrays is of decisive importance for these imaging techniques. The majority of ultrasound arrays manufactured in medical technology today use piezoelectric ceramic lead zirconate titanate (PZT), exploiting the reverse piezoelectric effect, to generate sound. However, high-frequency, high-resolution or contactless air-coupled arrays based on PZT are expensive and complex to manufacture. In addition, the toxic materials used are only sustainable to a limited extent (RoHS conformity).
Capacitive micromechanically manufactured ultrasonic transducers (CMUT) open up new possibilities here. Micromechanical manufacturing processes enable the economic production of corresponding ultrasound arrays for the first time. Furthermore, the high miniaturisation enables the use of CMUTs in invasive applications (e.g. intravascular ultrasound, IVUS). The results of the developments to date indicate a good property profile for CMUTs for the production of high-frequency arrays. The CMUT devices offer:
- very high acoustic bandwidth
- extremely low mechanical coupling between the elements
- good adaptability to water and air
- integration together with electronic components (ASIC)
- no toxic materials (RoHS conformity)
High bandwidth and low coupling between channels are fundamental condition for imaging that can match the standards of conventional ultrasound imaging. Fraunhofer IPMS' highly integrated MEMS technology makes it possible for the first time to connect the signals of an array on site with readout electronics to achieve a simple and compact contacting of the elements. By using the monolithic connection technology between sensor and electronics, highly planar surfaces can be realised as a contact to the medium.