While obtaining high quality images of static objects is feasible with many tomography modalities nowadays, imaging fast dynamic processes with both high spatial and temporal resolution remains very challenging but is of high interest in various clinical and scientific applications. Often, a high temporal resolution is achieved by a sub-sampled data acquisition (compressed sensing) and images reconstructed from the noisy, incomplete data by conventional algorithms are heavily impaired by artifacts and noise. Novel reconstruction approaches that incorporate mathematical models of the image dynamics demonstrated great potential to improve upon this in proof-of-concept studies but their formulation and implementation for high resolution 3D applications with complex dynamics pose severe mathematical and computational challenges.

The PhD candidate will start from a recently proposed generic mathematical and computational framework for dynamic inverse problems and tailor it towards a challenging, concrete application with X-ray computed tomography (CT). Depending on the interests and background of the PhD candidate, the focus can be on the mathematical modeling of the specific spatio-temporal image dynamics, improving the numerical optimization algorithms used to compute the image or incorporating machine learning approaches to replace the hand-crafted mathematical image models by learned ones. Furthermore, the developed methods should be evaluated with data measured in our FleX-ray imaging lab (see below). As such, the PhD candidate needs to carry out experimental work, such as designing and building appropriate phantoms and extending FleX-ray’s capabilities to perform dynamic experiments. The research of this PhD position will be performed within the Computational Imaging group at CWI, the national research center for Mathematics and Computer Science in The Netherlands (see below).

Keywords
Dynamic tomography, compressed sensing, image reconstruction, computational inverse problems, variational modeling, numerical optimization, machine learning.

Candidates are required to have a Master’s degree in Mathematics, Physics, Computer Science or Electrical Engineering. Good programming skills are essential. Experience with tomographic reconstruction, image processing, and volumetric reconstruction is desirable. Preferable qualifications for candidates include proven research talent, an excellent command of English, and good academic writing and presentation skills.

Fixed-term contract: 18 months.

The terms of employment are in accordance with the Dutch Collective Labour Agreement for Research Centres ("CAO-onderzoeksinstellingen"). The initial labour agreement will be for a period of 18 months. After a positive evaluation, the agreement will extended by 30 months. The gross monthly salary, for a PhD student on a full time basis, is €2,246 during the first year and increases to €2,879 over the four year period.
Employees are also entitled to a holiday allowance of 8% of the gross annual salary and a year-end bonus of 8.33%. CWI offers attractive working conditions, including flexible scheduling and help with housing for expat employees.

Please visit our website for more information about our terms of employment: www.cwi.nl/terms-of-employment

Centrum Wiskunde & Informatica (CWI)

Centrum Wiskunde & Informatica (CWI) is the Dutch national research institute for mathematics and computer science and is part of the Institutes Organisation of NWO. The mission of CWI is to conduct pioneering research in mathematics and computer science, generating new knowledge in these fields and conveying it to trade, industry, and society at large.

CWI is an internationally oriented institute, with 160 scientists from approximately 27 countries. The facilities are first-rate and include excellent IT support, career planning, training, and courses. CWI is located at Science Park Amsterdam that is presently developing into a major location of research in the natural sciences in The Netherlands, housing the sciences of the University of Amsterdam and of the Vrije Universiteit as well as several other national research institutes next to CWI.

http://www.cwi.nl

Computational Imaging Group

The Computational Imaging Group is headed by Joost Batenburg and currently has 16 members. It is specialized in the development of advanced computational techniques for the full 3D imaging pipeline, involving adaptive image acquisition, image reconstruction, and analysis/visualization of the resulting 3D datasets. The group follows an interdisciplinary approach and has expertise in Physics, Mathematics and Computer Science. It is one of the two main developer groups of the ASTRA Toolbox, which is a MATLAB and Python platform providing scalable, high-performance GPU primitives for 2D and 3D tomography, including building blocks for advanced reconstruction algorithms. One of its main design goals is geometric flexibility, allowing the toolbox to be used with many types of experimental set-ups, in particular for academic studies. In May 2017, the group established the FleX-ray imaging lab: A custom-made, fully-automated CT scanner linked to large-scale computing hardware designed for developing a real-time 3D imaging system where the acquisition can be adapted to the observations on the fly and for dynamic (4D) imaging.

https://www.cwi.nl/research/groups/computational-imaging