Title: What’s so exciting about RF pulses?
Abstract: Radiofrequency (RF) pulses are a fundamental part of every MRI pulse sequence, but their potential for encoding MR signals and prospectively mitigating image artifacts is often overlooked. In this talk I will present recent progress in RF spatial encoding using frequency-swept pulses and RF field gradients, which could enable low-cost and silent MRI scanners, as well as multiband pulses and the gSlider method (in collaboration with Kawin Setsompop at the Martinos Center), which enable high-resolution diffusion imaging. I will then show how array-compressed RF pulse design can be leveraged to optimize parallel transmission using a small number of transmit channels, and maybe even to numerically optimize transmit coil arrays for high-field MRI based on their performance in specific imaging sequences. In all, I hope to convince you that the development of RF pulses for uses beyond slice selection is a rich area of study, with the potential for impact across field strengths and applications.
Bio: William A Grissom is an Assistant Professor of Biomedical Engineering at the Vanderbilt University Institute of Imaging Science in Nashville. He directs a research group working on RF pulses and hardware for low- and high-field MRI, and also on MR-guided interventions and high-intensity focused ultrasound technologies for applications including non-invasive neurosurgery and neurostimulation.
Title: Individual variability and stability of functional brain organization
Abstract: Measurement of correlations in Blood Oxygen Level Dependent (BOLD) signal during resting state functional magnetic resonance imaging (fMRI) has enabled description of functional brain organization at multiple spatial and temporal scales. However, the cross-subject averaging that is frequently employed to generate such descriptions obscures patterns of brain organization specific to each individual. In this talk, I will present work extending the study of functional brain organization to highly sampled individuals. While substantial data acquisitions are required to generate convergent estimates of systems organization, this approach has revealedidiosyncratic areal and systems-level organization specific to individuals relative to standard group-average descriptions. These observations raise the intriguing possibility that, when compared to one another, individuals may have topological distinctions in functional organization relative to cortical anatomy and suggest thatunderstanding individual differences will require approaches that respect the specific anatomic and functional contours of each individual’s brain. This approach also allows for the study of intra-individual variability and I will discuss whether BOLD correlations meaningfully vary over the course of single resting-state scans.
Bio: Timothy Laumann is an MD/PhD candidate at Washington University in St. Louis. After graduating with high honors in Neuroscience from Dartmouth College, he worked for two years as a post-baccalaureate IRTA fellow at the National Institute of Mental Health in the Neuroimaging Core and Unit for Systems Neuroscience in Psychiatry. In 2008, he moved to St. Louis to pursue an MD/PhD at Washington University. His PhD work was in the labs of Steve Petersen and Bradley Schlaggar and focused on approaches for measuring the brain’s functional organization using resting state fMRI. During this time, he was also involved in the early development of the Human Connectome Project and has served as a member of several of its operational teams. His current research interests include using individualized functional neuroimaging approaches to understand the variability, stability, and adaptability of the brain's functional organization.