Combined Segmentation and Hemodynamic Analysis of Cerebrovascular Structures using Spatiotemporal Arterial Spin Labeling MRI

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Magnetic resonance imaging (MRI) has become an indispensable diagnostic and research tool. It is capable of visualizing the anatomy and function of organs. Time-resolved three-dimensional (i.e. 4D) MRI blood flow measurements, e.g. arterial spin labeling (ASL) MR angiography (MRA), of the brain is of increasing recent interest due to MRI technology advancements. 4D ASL MRA sequences are now capable of imaging cerebrovascular structures and blood flow with a spatial resolution better than 1 mm3 and a temporal resolution below 100 ms. Since this imaging technique utilizes blood as an intrinsic contrast agent, no exogenous contrast media is required, making it inexpensive and safe. However, the vast data volume obtained with 4D ASL MRA limits the utility of the technique, particularly if the only 2D images are only visually inspected. The broad goal of this research is to develop novel image analysis algorithms and visualization techniques for large time-resolved datasets to achieve blood flow analysis, vessel segmentation, and hemodynamic visualization techniques tailored to 4D ASL MRA datasets to enable fast, accurate, and quantitative interpretation.******We will design, optimize, and evaluate various implicit and explicit models for the hemodynamic analysis of blood flow dynamics based on the ASL time-intensity curves for each voxel in a first step. A segmentation of the cerebrovascular system is required to investigate the vessel anatomy quantitatively and to visualize the results. Therefore, we will develop new advanced vessel segmentation methods for extraction of the vessels from 4D ASL MRA datasets of the brain. More specifically, we will combine the hemodynamic analysis and cerebrovascular segmentation into an integrated analysis approach. It is expected that such a coupled vessel segmentation and blood flow analysis will lead to both improved segmentation and hemodynamic analysis results. Finally, advanced visualization methods for the combined representation of the cerebrovascular system and its blood flow will be developed and evaluated. For example, it is planned to design a glyph-based visualization of the 4D blood flow as well as dynamic surface-based visualization techniques. ******All methods will be integrated within a novel software tool that will be made available for applied imaging researchers, thereby enhancing the practical value of 4D ASL MRA. Collectively, this work will enable a fast, accurate, and quantitative interpretation of 4D ASL MRA datasets while creating new image analysis and visualization methods with broad applications for other image processing problems.