Imaging of cerebral perfusion by tracking the first passage of an exogenous paramagnetic contrast agent (termed dynamic susceptibility contrast, MRI) has been used in the clinical practice for about a decade. However, the primary goal of dynamic susceptibility contrast MRI to directly quantify the local cerebral blood flow remains elusive. The major challenge of dynamic susceptibility contrast MRI is to measure the contrast inflow to the brain, i.e., the arterial input function. The measurement is complicated by the limited dynamic range of MRI pulse sequences that are optimized for a good contrast in brain tissue but are suboptimal for a much higher tracer concentration in arterial blood. In this work, we suggest a novel method for direct arterial input function quantification. The arterial input function is measured in the carotid arteries with a dedicated plug-in to the conventional pulse sequence to enable resolution of T(2) on the order of a millisecond. The new technique is compatible with the clinical measurement protocols. Applied to the pig model (N = 13), the method demonstrates robustness of the arterial input function measurement. The cardiac output and cerebral blood volume, obtained without adjustable parameters, agree well with positron emission tomography measurements and values found in the literature.
Movement artifacts and other sources of noise are a matter of concern particularly in
the neuroimaging research of movement disorders such as Huntington’s disease (HD).
Using diffusion weighted imaging (DWI) and fractional anisotropy (FA) as a compound
marker of white matter integrity, we investigated the effect of movement on HD
specific changes in magnetic resonance imaging (MRI) data and how post hoc
compensation for it affects the MRI results. To this end, we studied by 3T MRI: 18
early affected, 22 premanifest gene-positive subjects, 23 healthy controls (50
slices of 2.3 mm thickness per volume, 64 diffusion-weighted directions (b = 1000
s/mm2), 8 minimal diffusion-weighting (b = 100 s/mm2)); and by 1.5 T imaging: 29
premanifest HD, 30 controls (40 axial slices of 2.3 mm thickness per volume, 61
diffusion-weighted directions (b = 1000 s/mm2), minimal diffusion-weighting (b = 100
s/mm2)). An outlier based method was developed to identify movement and other
sources of noise by comparing the index DWI direction against a weighted average
computed from all other directions of the same subject. No significant differences
were observed when separately comparing each group of patients with and without
removal of DWI volumes that contained artifacts. In line with previous DWI-based
studies, decreased FA in the corpus callosum and increased FA around the basal
ganglia were observed when premanifest mutation carriers and early affected patients
were compared with healthy controls. These findings demonstrate the robustness of
the FA value in the presence of movement and thus encourage multi-center imaging
studies in HD.
State-of-the-art cardiopulmonary resuscitation (CPR) restores circulation with inconsistent blood-flow and pressure. Extracorporeal life support (ECLS) following CPR opens the opportunity for "controlled reperfusion". In animal experiments investigating CPR with ECLS, systemic anticoagulation before induced cardiac arrest is normal, but a major point of dispute, since preliminary heparinization in patients undergoing unwitnessed cardiac arrest is impossible. In this study, we investigated options for ECLS after an experimental 15 minutes normothermic cardiac arrest, without preceding anticoagulation, in pigs. Neurological recovery was assessed by a scoring system, electroencephalography and brain magnetic resonance imaging. Additionally, brain histology was performed on day seven after cardiac arrest. We demonstrated that preliminary heparin administration was not necessary for survival or neurological recovery in this setting. Heparin flushing of the cannulae seemed sufficient to avoid thrombus formation. These findings may ease the way to using ECLS in patients with sudden cardiac arrest.
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