PhD Candidate, Department of Clinical Neurosciences, Oxford University
This talk presents two aspects of vascular imaging: vessel-wall imaging (VWI) of the large intracranial vessels and cardiac frequency fluctuations in EPI time series.
The SNR increase at 7T benefits VWI in terms of higher resolution but VWI is based on SAR-intense methods. We present the implementation of DANTE-SPACE, a sequence optimised for high resolution wall depiction and enhanced CSF suppression to produce wall contrast. Besides refining spatial scales, recent technical developments, such as multi-band acquisitions, have accelerated information content in the temporal domain. Sufficiently fast sampling in functional MRI resolves the spectrum beyond the cardiac frequency, thus transforming “physiological noise” into valuable signal. We describe strategies to map and quantify cardiac frequency fluctuation in EPI. The cardiac-induced EPI-signal shows tissue-specific characteristics. To investigate the origins that form these fluctuations we decomposed the EPI-signal over the cardiac cycle into S0 and T2 waveforms. We discuss potential mechanisms involved, such as fluctuations in partial volumes and oxygenation.