Grant Roberts, PhD

Grant Roberts, PhD

Specializing in clinical applications of phase-contrast MRI

Oral Presentations

Advancing Functional Assessment with Flow Sensitive Magnetic Resonance Imaging

March 10, 2023

Thesis Defense, Department of Medical Physics, Madison, WI

Description

Phase-contrast magnetic resonance imaging (PC-MRI) is a non-invasive imaging method capable of quantifying time-resolved hemodynamics. This dissertation aims to develop novel acquisition methods and post-processing tools for the robust assessment of intracranial and aortic hemodynamics using PC-MRI and to study their relationship with aging and neurodegeneration.

Advancing Functional Assessment for Cerebrovascular 4D Flow MRI

January 30, 2023

Seminar Presentation, Medical Physics Seminar Series, Madison, WI

Description

4D flow MRI (time-resolved, volumetric, three-directional velocity-encoded MRI) is a powerful imaging method that can capture blood flow, vascular anatomy, and complex flow patterns in a single acquisition.

Defining Normative Cerebral Hemodynamics in Cognitively Healthy Older Adults with 4D Flow MRI

May 09, 2022

Conference Oral Presentation, 2022 Joint Annual ISMRM-ESMRMB & ISMRT 31st Annual Meeting, London, United Kingdom

Description

This was our first oral presentation on the work that Anthony Peret and I have done on the normative 4D flow study. This talk focused on methodology and basic statistics, specifically our custom cranial 4D flow analysis tool, intra/interobserver repeatability, normal intracranial blood flow ranges in older adults, and how blood flow and pulsatility change as we age. It was presented at ISMRM and was my first in-person oral presentation since COVID. Anthony is currently preparing a similar talk for late August 2022 at ASFNR on the relationship between vascular risk factors and measured intracranial flow and pulsatility.

Free-Breathing Radial 2D Phase Contrast MRI for Aortic Pulse Wave Velocity Measurements in Healthy Older Adults

September 11, 2020

Conference Oral Presentation, SMRA 32nd Annual International Conference, Virtual

Description

In this oral presentation given at SMRA, I discuss our findings from our free-breathing pulse wave velocity (PWV) study in collaboration with the Okonkwo lab. Here, we assessed the feasibility of using radial 2D phase contrast MRI to measure aortic PWV, which is directly related to aortic stiffness. Because respiratory motion during a scan can result in bad image quality, PWV MRI scans are often performed under breath-hold conditions which can be sometimes be challenging. For this project, we allowed subjects to breath freely during the scan and used respiratory gating to retrospectively create images only in stationary respiratory phases, improving image quality. We also used regularized (local low rank) reconstructions to greatly improve image quality. We demonstrated no significant differences between our free-breathing technique and the standard breath-hold technique.

Venous Mapping of Vascular Malformations using Cranial 4D Flow MRI with Improved ‘Virtual Injections’

August 08, 2020

Conference Oral Presentation, 2020 ISMRM & SMRT Virtual Conference & Exhibition, Virtual

Description

I presented an abstract as a second author (originally submitted by my advisor Laura Eisenmenger) on the use of 4D flow-generated virtual injections for use in venous mapping of arteriovenous malformations (AVM). AVMs range from benign to very high risk, depending on the size, location, number of feeding vessels, etc. Because of this, they can difficult to manage and treat. Transvenous embolization has recently emerged as a promising surgical approach to treat AVMs. In this presentation, we discuss the promise of our virtual injection technique (using forward/reverse injections) in an AVM case at our institution.

Cranial Hemodynamics Assessed with MRI: An Introduction with Relevance to AD – Part 2

August 03, 2020

Talk, University of Wisconsin - School of Medicine and Public Health, Madison, WI, USA

Description

This was the second talk of our 2-part ADRC vascular imaging series. In the previous lecture, we discussed principles of flow imaging and results from recent studies. In this lecture, we focus on more advanced imaging methods to obtain non-conventional measures of: vessel stiffness, brain tissue stiffness (MRE), perfusion (ASL), and ways to assess glymphatics and the integrity of the blood brain barrier.

Cranial Hemodynamics Assessed with MRI: An Introduction with Relevance to AD – Part 1

June 15, 2020

Talk, University of Wisconsin - School of Medicine and Public Health, Madison, WI, USA

Description

This talk was the first of a 2 part series, intended for members of the Wisconsin Alzheimer’s Disease Research Center (ADRC) to demonstrate our state-of-the-art vascular imaging techniques that our research groups have developed for studying cerebrovascular contributions to dementia and Alzheimer’s disease. Specifically, we focus on basic principles of flow MR imaging, what can be measured and how we measure it, and some results of recent studies.

Brain MR Elastography: Acquisition and Reconstruction Strategies

March 05, 2020

Internal Presentation, UW MRI Group Meeting, Madison, WI, USA

Description

Annual UW-Madison MRI Group meeting to share findings or discuss relevant MRI topics. For this talk, I reviewed brain MR elastography (MRE), a technique that allows one to measure brain stiffness using MRI (crazy!). We recently collaborated with GE Healthcare and the Mayo Clinic to implement brain MRE at our institution. This talk was designed to provide background on our recently-implemented MRE technique for our MRI colleagues.

Automating Background Phase Correction in Cranial 4D Flow MRI

August 27, 2019

Conference Power Pitch, SMRA 31st Annual International Conference, Nantes, France

Description

My first in-person presentation was a powerpitch at SMRA in 2019. Powerpitches are typically short (~3 minute) elevator pitches designed to quickly grab the interest of the audience. For this work, I discuss the findings from our study on the effects of automating background phase correction in our reconstruction pipeline. When we were initially developing our cranial 4D flow analysis tool, we were constantly looking for ways to decrease manual interaction and the time needed to load 4D flow data for post-processing. One of the manual steps in our processing pipeline was background phase correction, which corrects eddy-current phase errors created by the flow-encoding gradients. In this presentation, I showed that an automatic phase correction implementation in the reconstruction actually outperforms manual background phase correction. This justified the use of skipping the manual correction step if background phase correction was done in the reconstruction, streamlining our tool.

Hemodynamics of Chronic Mesenteric Ischemia using 4D Flow MRI

April 25, 2019

Internal Presentation, UW MRI Group Meeting, Madison, WI, USA

Description

Annual UW-Madison MRI Group meeting to share findings or discuss relevant MRI topics. In this talk, I discuss the findings from our chronic mesenteric ischemia study. After eating a meal, blood flow to the gut normally increases. In patients with chronic mesenteric ischemia (CMI), this blood flow response is stunted, which can be caused by atherosclerotic narrowing, arteritis, or other pathologies that restrict blood flow. In this work, we use 4D flow MRI to measure mesenteric blood flow before and after a meal and show that blood flow is stunted in patients with CMI relative to controls, making 4D flow MRI a potential diagnostic tool.