This opens for exciting new imaging possibilities as f.ex. noise suppression for imaging of soft plaque (1st image), and enhanced contrast agent imaging for cancer detection (2nd image).

Image 2: Enhanced contrast agent imaging for cancer detection.

Several topics are available, also in collaboration with departments in cybernetics, signal processing, computer science, acoustics, electronics, and mathematics at NTNU.  Example topics are related to nonlinear ultrasound propagation and signal processing, mathematical topics on simulation of nonlinear wave propagation and scattering, GPU parallel programming for real time processing, and multiband transducer designs.

Why does the manipulation pulse make a difference?

Both the scattering and the sound propagation speed is pressure dependent. So applying a manipulation pressure will alter these properties and an imaging pulse travelling in a compression phase of the manipulation wave will be slightly different from a pulse travelling in the rarefaction phase. This difference can be used to extract more information about the tissue and thus enables more advanced processing schemes. For more information on the method take a look at the SURF imaging page.

A group of researchers works at the department with SURF imaging and we are looking forward to offer you a project or thesis in one of the most exciting fields of medical ultrasound imaging! 

Skills

In general students will gain knowledge in the following areas:

• Wave propagation (Ultrasound theory)
• Programming (Matlab, C, C++, Python)
• Signal processing
• Medicine
• Literature study and writing of articles
• team work
• research and development

Tailoring of topics

Below you'll find a list with available topics. They are all relevant both for master thesis as well as project work. The descriptions are kept quite general and since they anyway will be individually tailord to your interest f.ex. a focus on lab-work, programming, simulations, theoretical and algorithm development ...
Please get in contact with the corresponding supervisors! They'll help you finding the perfect topic for and with you.

Topic: Improved detection of ultrasound contrast agents

The ultrasound echo from blood is very weak compared to the echoes generated by tissue. In many situations it is desired to detect and image blood in the smallest blood vessels. To detect blood in these capillaries often an ultrasound contrast agent is injected into the blood circulation of a patient. These contrast agents are gas-bubbles with a typical diameter of 3µm which give en enhanced ultrasound echo and are transported with the blood. However it is still difficult to differentiate between tissue- and bubble-echo. This is especially important in the diagnosis and treatment of cancer where good imaging of the vessels and their structure is curcial. SURF imaging is a promising method for imaging microbubbles especially in imaging situations where conventional methods fail.

The topic will contain optimalizing, testing and verification of the method and the algorithms behind. Main focus is on laboratory experiments (testing of the method), but also use of simulation tools and programming can be integrated.

Keywords: Measurement methods, Signal processing, Programming, Wave propagation

Topic: Reverberation suppression

Image quality in ultrasound is very patient dependent. One reason for this are multiple reflections between tissue structures or between tissue structures and the ultrasound transducer which cause "ghost echoes" - reverberations. In the best case reverberations become visible as a discernable distinct copy of a tissue structure in shallow depths but more often and more serious a haze of noise is spread over the image.
This noise in the image causes problems in diagnosis in nearly all applications where ultrasound images are used for diagnostics.

The topic contains work on beamforming, simulations and phantom design (design test bodies) for better noise suppression. This comprises in most cases work with software tools and can also comprise experimental work in the ultrasound lab.

Topic: Estimation of non-linear scattering

Calcium particles are building up in the tissue in a number of medical conditions. In for example the diagnosis of breast cancer the physician is interested in calcium particles as they may indicate malignancy. Calcium is visualized very good in X-ray imaging, but not that good in ultrasound.
Improved imaging of calcium particles would directly give better diagnostics and guidance of tissue biopsies.

The topic contains experimental work in the lab, simulations, signal processing and estimation.

Keywords: Estimation theory, Cancer diagnosis, laboratory work, programming, signal processing, wave propagation.

Topic: Transducer for SURF Imaging

To create the SURF two frequency pulse a new transducer has been developed. The transducer consist of a stack of at least two piezoelectric layers, one for the low frequency pulse and one for the high frequency pulse, and layers inbetween the two for mechanical isolation and matching between the two layers. A couple of prototypes transducer arrays have been manufactured, and are succesfully used for imaging. However there are several issues to be investigated for the transducer design, amongst others; bandwidth of the passbands, internal reverberations, mechanical cross coupling, electrical matching to the scanner, non linear behaviour of the transducer.
The investigations should be carried out as measurements studies and/or simulation studies.

Supervision

The students have Bjørn Angelsen as their main or co-supervisor.

Main supervisor

• Bjørn Angelsen

Co - supervisors

• Rune Hansen
• Tonni F. Johansen