A multidisciplinary research project in the field of microfabricated transducers for ultrasound imaging is being established in collaboration at the Department of Health Technology at the Technical University of Denmark.
Responsibilities and tasks
Background: Modern medical ultrasound imaging is made using multi-element piezoelectric transducers. Often the arrays consist of 192 elements with a spacing between elements of one or a half wavelength (?/2). Typically, the frequency in medical ultrasound is between 3 to 15 MHz making the wavelength around 0.5 to 0.1 mm. The pitch is, thus, very small and the kerf between elements is in microns. The introduction of 2D arrays for three-dimensional imaging is increasing the problems. Here the elements are ?/2 square and the sub-dicing of the piezoelectric crystal often results in a very low yield and expensive transducers. Also, the interconnection between the elements and the transducer cables is a challenge. The current 2D arrays houses 32 × 32 elements or 64 × 64 elements. This large element count precludes making connections to all elements and sparse arrays have to be used which impacts image quality in terms of resolution and contrast. New technology is therefore needed for advancing three-dimensional ultrasound imaging.
CMUT technology: Recent years has seen the development of integrated ultrasound transducers based on silicon technology. Using MEMS (Micro Electro Mechanical Systems) technology allows for fabrication of capacitive micromachined ultrasonic transducers (CMUTs). Each of these devices have a thin plate that can be actuated by electrostatic forces thus generating an ultrasound pulse. The CMUT cells have typical lateral dimensions in the 10-40 micron range. The CMUT cells are grouped to form larger elements and the elements are combined into a CMUT array. The technology is still in its early stages and can be further advanced, but the potential capabilities are large. It is here possible to fabricate any number of elements in any kind of configuration including 2D arrays with a very large number of elements.
This project: In this project, there will be special emphasis on row-column addressed CMUT arrays with integrated diverging lenses that will increase the field of view. You will design and fabricate CMUT chips that are suitable for ultrasound imaging using the DTU NanoLab clean room facility in close collaboration with the MEMS group at DTU Healthtech. The design process involves using finite element tools (COMSOL, PZFlex) for CMUT design and Silvaco Athena for process design. Once the chips have been fabricated they will be mounted in an ultrasound probe and using the polymer lab at the MEMS group you will work on developing diverging lenses. The probes will then be used at Center for Fast Ultrasound imaging’s (CFU) for ultrasound imaging. DTU NanoLab has a state of the art cleanroom suited for fabrication of micromachined structures. CFU are experts in synthetic aperture ultrasound imaging and has the SARUS experimental ultrasound scanner, which can acquire and process data from 1024 transducer elements in real time. In synthetic aperture imaging, it is possible to build up the image from several emissions and different elements can be measured from emissions to emissions. Combining all the data will significantly increase the image quality.
The purpose is therefore to make CMUT row-column addressed probes with a large number of elements having integrated diverging lenses. These are then interfaced to the SARUS system and commercial scanners for real-time operation and experimentation.
Candidates should have a two-year master’s degree (120 ECTS points) or a similar degree with an academic level equivalent to a two-year master’s degree.
Approval and Enrolment
The scholarship for the PhD degree is subject to academic approval, and the candidate will be enrolled in one of the general degree programmes at DTU. For information about our enrolment requirements and the general planning of the PhD study programme, please see the DTU PhD Guide.
The assessment of the applicants will be made by Professor Erik V Thomsen.
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Salary and appointment terms
The appointment will be based on the collective agreement with the Danish Confederation of Professional Associations. The allowance will be agreed upon with the relevant union. The period of employment is 3 years.
You can read more about career paths at DTU here.
Additional information may be obtained from Professor Erik V Thomsen heading the MEMS group, phone (+45) 4525 5766, e-mail: ervt@.dtu.dk.
You can read more about DTU Health Tech on www.healthtech.dtu.dk.
Please submit your online application no later than 23 October 2019 (local time). Apply online at www.career.dtu.dk.
Applications must be submitted as one PDF file containing all materials to be given consideration. To apply, please open the link “Apply online”, fill out the online application form, and attach all your materials in English in one PDF file. The file must include:
- A letter motivating the application (cover letter)
- Curriculum vitae
- Grade transcripts and BSc/MSc diploma
- Excel sheet with translation of grades to the Danish grading system (see guidelines and Excel spreadsheet here)
Candidates may apply prior to obtaining their master’s degree but cannot begin before having received it.
Applications and enclosures received after the deadline will not be considered.
All interested candidates irrespective of age, gender, race, disability, religion or ethnic background are encouraged to apply.
DTU Health Tech engages in research, education, and innovation base on technical and natural science for the healthcare sector. The Healthcare sector is a globally expanding market with demands for the most advanced technological solutions. DTU Health Tech creates the foundation for companies to develop new and innovative services and products which benefit people and create value for society. DTU Health Techs expertise spans from imaging and biosensor techniques, across digital health and biological modelling, to biopharma technologies.
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