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Section: New Results
Vascular Imaging and Arterial Spin Labeling
Peripheral angiography and neurovascular imaging
Participants : Hélène Raoult, Jean-Yves Gauvrit, Elise Bannier, Pierre Maurel, Christian Barillot, Jean-Christophe Ferré.
Work-in-progress Non contrast enhanced MR angiography sequences were optimized on phantom as well as healthy volunteers and evaluated on patients presenting arterio venous malformations (AVM). High temporal resolution (70ms) images were obtained and compared to the gold standard Digital Subtraction Angiography. Results showed that Time-resolved SL MR angiographic imaging over two cardiac cycles is a reliable clinical tool for cerebral AVM characterization, yielding very good to excellent agreement with DSA. This work was published in Radioloy late 2013. This data was also post processed to obtain hemodynamics maps (time to peak, wash-in, wash out and mean transit time) and discriminate among different AVM components to relate hemodynamic patterns with rupture risk. This work was published in Stroke [23] .
Robust perfusion maps in Arterial Spin Labeling by means of M-estimators
Participants : Pierre Maurel, Jean-Christophe Ferré, Christian Barillot.
Non-invasive measurement of Cerebral Blood Flow (CBF) is now feasible thanks to the introduction of Arterial Spin Labeling (ASL) Magnetic Resonance Imaging (MRI) techniques. To date, due to the low signal-to-noise ratio of ASL, a single acquisition (pair of control/label scans) is not sufficient to estimate perfusion reliably. Instead, the acquisition is usually repeated several times and the perfusion information is calculated by averaging across the repetitions. However, due to its zero breakdown point, the sample mean is very sensitive to outliers. We have proposed [18] to compute ASL CBF maps using Huber’s M-estimator, a robust statistical function that is not overly impacted by outlier. This work was part of the PhD thesis of Camille Maumet.
Brain perfusion gender difference study using MRI in young adults
Participants : Léa Itmi, Pierre Maurel, Christian Barillot.
The usage of population models is becoming increasingly important in cerebral imaging, particularly in ASL. Therefore, it is important to check the limits of the models before applying them, to guarantee the reliability of the results. It is now well-known that brain perfusion changes with the age, and this effect is taken into account when evaluating brain perfusion images. But gender differences have not been well studied yet. It is known for a long time that female brain perfusion is higher than male brain perfusion, but few studies have investigated whether some regional perfusion differences exist or not. We evaluate whether, as for the age, gender differences should be taken into account when analyzing brain perfusion images. We focus on young adults subjects and studied, at the region level and the voxel level if gender differences exist and how it differs. The overall and regional differences were analyzed and then we also investigated the perfusion asymmetries in the brain (left hemisphere versus right hemisphere).