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My research interest is in the field of Magnetic Resonance Imaging (MRI), particularly in imaging the human vasculature and the heart. These noninvasive diagnostic procedures are challenging because one tries to acquire large data sets (dynamic 3D volumes of good spatial resolution) at a fast rate (e.g. passage of a contrast agent) in the presence of complex motion (e.g. cardiac and respiratory motion).
Most of my work focusses on the development of novel imaging strategies that aim at acquiring images of better quality and/or at a faster rate and/or with improved information for an added value in diagnosis. This research includes the analsysis and simulation of signal behaviour in magnetic spin systems, the implementation of new acquisition schemes (pulse sequence programming and development of reconstruction software for MR scanners), and the evaluation of techniques in phantoms, volunteers, and patient studies.
At some point I hope to have the time to present my projects in a web-friendly format with more pictures and movies. As for now, you might want to check out my list of publications for further details on my projects of the past and presence. Some of my smaller projects you can find es technical reports on that very same site.
Current projects
- Validating the effects of Arteriogenesis Therapy
The research group for experimental and clinical arteriogenesis at the University in Freiburg is investigating the use of GM-CSF to support arteriogenesis (rapid growth of preexisting collateral arteries) in patients with peripheral vascular disease. The subcutaneous injection of the drug might offer advantages over common therapies such as vascular surgery. We are investigating the use of MR flow measurements as a modality to quantify the changes in peripheral blood flow and vascular resistance during the therapy.
- Flow compensated 3D SSFP sequences with radial acquisitions (VIPR)
Steady state free precession (SSFP) sequences such as trueFISP (Siemens), FIESTA (GE), and balanced FFE (Phillips) are typically not flow compensated in all three directions. Therefore, certain flow profiles in the image can lead to signal voids. In this project we are investigating the use of a true 3D radial acquisition called VIPR (Vastly undersampled isotropic projection rconstruction) which potnetially can be flow compensated in all directions.
- Motion Correction with a 3D radial acquisition (VIPR)
It has been shown for the 2D case, that radial acquisitions offer advantages over the standard spin-warp encoding in terms of robustness towards motion artifacts. In addition, the projections contain information to allow for motion correction without any penalties in imaging time as needed e.g. for navigator techniques. This work extends the properties to a true 3D radial acquisition (VIPR) for in-plane and through plane motion correction.
- Imaging of cardiac function with isotropic resolution
Volume measurements in the heart, e.g. for the calculation of ejection fraction, require the acquisition of dynamic 3D data sets. Typically, these data are acquired in form of 2D slices over several breathholds. We investigate a method to acquire a 3D data set with isotropic resolution so that there are misregistration artifacts and an improved spatial through-plane resolution.
Past projects
- Trajectory correction for 3D radial acquisitions
The effects of eddy currents and gradient anisotropies can cause severe image degradation in radial MR acquisitions. In this study I developed a correction scheme to overcome these errors either with a post-processing correction of the acquired data or with a corrected acquisition that does play out the desired trajectory.
- Realtime system for dynamic 3D contrast-enhanced MR Angiography of the abdomen
[Contrast-enhanced MR Angiography of the abdomen is fairly challenging because of a short window of opportunity for the acquisition of signal form the arteries without interfering signal from the veins. In addition to the short turnaroudn time of the contrast agnet in the kidneys, the acquisition has to be timed with the arrival of the bolus and a breathhold to minimize motion artifacts. Therefore, the typical imaging strategy aims at the acquisition of a single volume with peak arterial signal. We developed a novel realtime system and modified the dynamic acquisition scheme TRICKS for dynamic 3D imaging of the abdomen.
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