Andreas Havreland

PhD defence by Andreas Havreland

On Tuesday 18 February 2020, Andreas Havreland will defend his PhD thesis "Micromachined Integrated 2D Transducers for Ultrasound
Imaging"

Time: 13:00

Place: Bldg. 208, aud. 54

Supervisor: Professor Erik V. Thomsen
Co-supervisor: Professor Jørgen Arendt Jensen

Assessment committee:
Professor Henrik Bruus, DTU Physics
Associate Professor Dominique Certon, Graduate school of engineering University Francois-Rabelais
Senior Specialist Carsten, Grundfos Holding A/S

Chairperson at
defence:
Associate Professor Marie Traberg

Abstract:
Ultrasound imaging is a widely used imaging technique for diagnostics. For the last 30 years 3-D ultrasound imaging has received increasing interest, as it offers several advantages compared to conventional 2-D imaging. Two-dimensional images are dependent on both position and scan angle, making some imaging planes inaccessible due to the anatomy of the human body. Volumetric imaging does not have the same drawback, as any plane is available from the volume data. It also offers accurate estimation of the size of organs, cysts, and tumors without relying on assumptions and the operator skills needed when using 2-D imaging estimations. However, 3-D ultrasound probes are far more complex than conventional probes, resulting in expensive equipment that impairs the low-cost advantage of ultrasound, and thus limits it more widespread use.

The objective of this thesis is to develop and demonstrate a transducer technology that can produce real-time volumetric images, but without the complexity and cost of available 3-D ultrasound systems. Focus has been on row-column-addressed arrays, offering volumetric imaging with a greatly reduced amount of electrical connections. This reduces data processing requirements and manufacturing cost. To manufacture such arrays, capacitive micromachined ultrasonic transducer (CMUT) technology was chosen as a platform because it offers a high degree of flexibility and interesting properties such as a large bandwidth. 

A theoretical treatment of CMUTs is presented, including investigations using non-linear static and dynamic models of a single CMUT cell. Four different micro fabrication processes were investigated to produce stable and reliable transducers. Two 92+92-element row­column-addressed arrays were fabricated and assembled into fully functioning hand-held probes. The imaging performance of the transducers were evaluated and attenuation along the electrode yielded a non-uniform transmit pressure. A mathematical criterion was developed to predict the degree of attenuation which was verified by experimental measurements. 

The results show that the row-column technology is a realistic alternative to matrix probes for volumetric imaging, and especially as a low cost alternative. This can contribute to a more widespread use of volumetric ultrasound imaging and to the development of new clinical applications benefiting both patients and the society. 

Tidspunkt

tir 18 feb 20
13:00 - 16:00

Arrangør

DTU Sundhedsteknologi

Hvor

Bldg. 208, aud. 54