CHAIR OF MEDICAL

SYSTEMS TECHNOLOGY

Computed tomography (CT) is one of the most important and widely applied diagnostic tools in clinical practice today. CT based on conventional x-ray absorption imaging, however, lacks functional information on the molecular level. Therefore it is quite interesting to develop new high-resolution techniques for functional CT.
One promising approach is to use functionalized gold nanoparticles conjugated to bio-molecules for which it has already been shown that specific tumor imaging can, at least in principle, be achieved using conventional CT, although at a concentration and radiation dose far too high for clinical imaging.
Our approach on the other hand is based on detection the x-ray fluorescence emission of these functionalized gold nanoparticles. This enables the detection of a concentration of the gold nanoparticle based tracer down to the nanomolar range.
This would ultimately allow for molecular imaging applications that have previously only been possible in nuclear medical imaging. Because the functionalization of these nanoparticles is very flexible this would also open up the opportunity to develop molecular imaging methods for a wide variety of applications with all the advantages of CT like high resolution and simultaneous imaging of the anatomy.

There are several sub-projects for students:

1. Development of a laboratory benchtop cone-beam x-ray fluorescence CT: Based on proof-of-principle experiments an extended imaging setup will be constructed capable of 3D imaging of x-ray fluorescence emissions from gold-nanoparticle tracers. This provides a large opportunity for creative work, as all parts of the system (detector, source, mechanics, reconstruction) have to be developed specifically for this new imaging method.
2. Optimized reconstruction: As XFCT differs from conventional absorption CT the naive application of standard reconstruction algorithms results in artifacts, especially for imaging the K-beta emission. There are a number of approaches a student could work on to solve this. One would be to implement an attenuation correction in analytic reconstruction algorithms. Another would be to implement an iterative reconstruction algorithm specifically for XFCT with a compressed sensing approach.
3. Monte Carlo simulation of a cone beam x-ray fluorescence CT and system characterization: Extension of an existing simulation of the imaging setup. The goal there is to analyse the advantages and disadvantages of the K-alpha and K-beta measurement methods. The student work would be focused on the further development of the Monte Carlo simulation and the analysis of the attained data.
4. Implementation of a rotating collimator in a simulation of an electron beam scanning CT system: Electronic scanning of an electron beam on a ring anode would provide a very fast CT imaging setup and has been implemented in a prototype in our laboratory. In order to use this for XFCT a rotating collimator could be implemented for fast scanning. The student work would be focused on testing the feasibility of this method and to analyse the imaging time and sensitivity.

If you are interested, please contact Dr.-Ing. Melanie Fachet by e-mail and provide: short CV, transcript of academic records, areas of interest and desired starting date.