Quantification of Network Perfusion in ASL Cerebral Blood Flow Data with Seed Based and ICA Approaches

Independent component analysis (ICA) or seed based approaches (SBA) in functional magnetic resonance imaging blood oxygenation level dependent (BOLD) data became widely applied tools to identify functionally connected, large scale brain networks. Differences between task conditions as well as specific alterations of the networks in patients as compared to healthy controls were reported. However, BOLD lacks the possibility of quantifying absolute network metabolic activity, which is of particular interest in the case of pathological alterations. In contrast, arterial spin labeling (ASL) techniques allow quantifying absolute cerebral blood flow (CBF) in rest and in task-related conditions. In this study, we explored the ability of identifying networks in ASL data using ICA and to quantify network activity in terms of absolute CBF values. Moreover, we compared the results to SBA and performed a test-retest analysis. Twelve healthy young subjects performed a fingertapping block-design experiment. During the task pseudo-continuous ASL was measured. After CBF quantification the individual datasets were concatenated and subjected to the ICA algorithm. ICA proved capable to identify the somato-motor and the default mode network. Moreover, absolute network CBF within the separate networks during either condition could be quantified. We could demonstrate that using ICA and SBA functional connectivity analysis is feasible and robust in ASL-CBF data. CBF functional connectivity is a novel approach that opens a new strategy to evaluate differences of network activity in terms of absolute network CBF and thus allows quantifying inter-individual differences in the resting state and task-related activations and deactivation

A k-space sharing 3D GRASE pseudocontinuous ASL method for whole-brain resting-state functional connectivity

Magnetic resonance imaging (MRI) investigations of resting‐state functional connectivity (RSFC) typically use blood oxygen level‐dependent (BOLD)‐weighted imaging because of its ability to provide whole‐brain coverage and high temporal resolution. Single‐shot 3D gradient‐ and spin‐echo (GRASE) arterial spin labeling (ASL) offers a number of potential advantages for RSFC measurements, such as a more direct quantitative correlate of neural activity and lower variability across subjects; however, current sequences are usually not suitable for whole‐brain acquisitions because of T2 decay during the long echo train. In this study, we proposed a k‐space sharing 3D GRASE ASL sequence to achieve whole‐brain coverage, applied it to measure RSFC on a group of healthy subjects, and compared it with BOLD data. Similar RSFC networks were estimated using both techniques, providing corroboration of the capability of our method for RSFC analysis. Furthermore, ASL data enable calculation of mean cerebral blood flow (CBF) values within the RSFC networks, thus assigning them biologically meaningful values. The inherently quantitative nature of CBF measurements should provide a more stable and interpretable biomarker in comparison to BOLD and may, therefore, be particularly useful for applications such as longitudinal studies of RSFC. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 37–43, 201

Preclinical MRI of the kidney : methods and protocols

This Open Access volume provides readers with an open access protocol collection and wide-ranging recommendations for preclinical renal MRI used in translational research. The chapters in this book are interdisciplinary in nature and bridge the gaps between physics, physiology, and medicine. They are designed to enhance training in renal MRI sciences and improve the reproducibility of renal imaging research. Chapters provide guidance for exploring, using and developing small animal renal MRI in your laboratory as a unique tool for advanced in vivo phenotyping, diagnostic imaging, and research into potential new therapies. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Cutting-edge and thorough, Preclinical MRI of the Kidney: Methods and Protocols is a valuable resource and will be of importance to anyone interested in the preclinical aspect of renal and cardiorenal diseases in the fields of physiology, nephrology, radiology, and cardiology. This publication is based upon work from COST Action PARENCHIMA, supported by European Cooperation in Science and Technology (COST). COST (www.cost.eu) is a funding agency for research and innovation networks. COST Actions help connect research initiatives across Europe and enable scientists to grow their ideas by sharing them with their peers. This boosts their research, career and innovation. PARENCHIMA (renalmri.org) is a community-driven Action in the COST program of the European Union, which unites more than 200 experts in renal MRI from 30 countries with the aim to improve the reproducibility and standardization of renal MRI biomarkers