I am a PhD student in the Physics Group at FMRIB. My research focuses on MRI methods that can be used to assess cerebrovascular properties.
As part of my project I worked on intracranial vessel-wall imaging to depict the structure of larger cerebral arteries, such as the middle cerebral artery (MCA). Geometrical changes, plaque accumulation and occlusion of the MCA and its early perforators is a common finding in certain types of stroke and small vessel disease. MRI can be used to study the vessel wall non-invasively in humans. Imaging the vessel wall is challenging due to its sub-milimeter size. In addition contrast is reduced by disturbing signal from blood and cerebrospinal fluid in the vicinity of the wall. Using the velocity spoiling effect of a variable flip angle turbo-spin echo sequence (SPACE) and the slow-flow crushing effect of a DANTE preparation, suppression of blood and CSF signal can be achieved while still preserving enough signal from the vessel wall itself. This work is carried out on FMRIB's 7 Tesla human scanner.
In my current work I am acquiring functional MRI (fMRI) data at rest (i.e. the subject is not performing any task, but is awake). I am particularly interested in ultra-fast acquisition techniques that allow to temporally resolve signal fluctuations that are caused by physiological fluctuations, especially the cardiac cycle. My work looks into strategies to use the MRI signal fluctuations to derive properties of the cerebral vasculature, such as vessel stiffness or the lag of the cardiac pulse wave into the surrounding tissue.
Cardiac cycle-induced EPI time series fluctuations in the brain: Their temporal shifts, inflow effects and T2(∗) fluctuations.
Viessmann O. et al, (2017), Neuroimage, 162, 93 - 105
T2-Weighted intracranial vessel wall imaging at 7 Tesla using a DANTE-prepared variable flip angle turbo spin echo readout (DANTE-SPACE).
Viessmann O. et al, (2017), Magn Reson Med, 77, 655 - 663
7 Tesla MRI in cerebral small vessel disease.
Benjamin P. et al, (2015), Int J Stroke, 10, 659 - 664
Acoustic super-resolution with ultrasound and microbubbles.
Viessmann OM. et al, (2013), Phys Med Biol, 58, 6447 - 6458
- Neurovascular Imaging Research Group