Ultrahigh Field Magnetic Resonance Imaging – Technical Development and Translational Applications

Magnetic resonance imaging (MRI) may be used to provide detailed images of the human body with excellent soft tissue contrast. Alongside its current widespread clinical applications for diagnosis and treatment, MRI allows researchers to measure structure and function of different tissue types in order to advance our understanding of human biology and enable new medical applications of MRI. In particular, diseases affecting nerves and vessels, such as trigeminal neuralgia, with uncertain etiology can be studied using multiple MRI modalities so that treatment planning can we more effective and patient outcomes can be improved. Ultrahigh field MRI scanners, such as those operating at 7-­‐tesla (7T), provide increased signal-­‐to-­‐noise ratio, which can be translated to higher spatial resolution. Additional advantages of high magnetic field MRI include enhanced vascular contrast as well as improved spectral separation and quantification for MR spectroscopy. These benefits over MRI at lower field strengths make ultrahigh field MRI a powerful new tool for performing quantitative image analysis with increased accuracy. One quantitative application of MRI is the detection and visualization of cells labeled with magnetic nanoparticles. This unconventional use of the imaging modality enables very effective imaging of cells or lesions tagged with these particles. The projects explored herein consist of such quantitative image analysis using advanced imaging techniques, including ultrahigh field MRI

Ultra-high Field MRI Methods for Precise Anatomical and Spectroscopic Measurements in the Brain and Application to Neurological and Neuropsychiatric Diseases

Neurological and neuropsychiatric diseases and disorders are a major burden on society, impairing the health and functioning of millions of people every year. There is a need to define the biological bases of these diseases and identify potential biomarkers to improve diagnosis, monitoring, and treatment efficacy across multiple diseases. Magnetic resonance imaging (MRI) is a noninvasive imaging technique which facilitates detection of brain lesions and visualization of the brain overall. However, limitations in contrast and resolution at clinical field strengths may hinder investigation of the underlying biological mechanisms of these diseases. Ultra-high field MRI scanners, such as those at 7-Tesla, can enhance biomarker detection because they provide superior contrast, resolution, and signal-to-noise-ratio (SNR) in feasible scan times. Since ultra-high field systems come with their own unique set of technical challenges, especially as applied to brain imaging, technique optimization and development is often required. To address these concerns while leveraging the advantages of 7-Tesla MRI, we have designed and conducted studies to provide high-resolution imaging of small structures and high spectral resolution of metabolite concentrations in clinically feasible scan times. As a group, these studies provide support for the usefulness of ultra-high field MRI for revealing disease pathophysiology through the detection of biomarkers, which may be unclear or below the threshold of detectability at clinical field strengths. The purpose of this work was to investigate anatomical and spectroscopic biomarkers in the brain. Specifically, we analyzed limbic structure subfield volumes, including subfields of the hippocampus, amygdala, and thalamus, for diseases including major depressive disorder (MDD) and trigeminal neuralgia (TN). We found a significant reduction in the right CA2/3 subfield volume of the hippocampus in MDD patients compared to healthy controls. In TN, we found significant differences in subfield volumes between patients and controls, specifically in the nerve cross-sectional-area, in the basal and paralaminar subnuclei of the amygdala, and in the central lateral subnucleus and the inferior and lateral pulvinar subnuclei of the thalamus. We also developed a method for detecting gamma-Aminobutyric acid (GABA) with spectroscopic editing, with potential application to MDD. In summary, we have presented significant findings in biomarker detection and a novel method for spectroscopic signal editing of GABA at ultra-high field MRI

Leveraging high-resolution 7-tesla MRI to derive quantitative metrics for the trigeminal nerve and subnuclei of limbic structures in trigeminal neuralgia

Background: Trigeminal Neuralgia (TN) is a chronic neurological disease that is strongly associated with neurovascular compression (NVC) of the trigeminal nerve near its root entry zone. The trigeminal nerve at the site of NVC has been extensively studied but limbic structures that are potentially involved in TN have not been adequately characterized. Specifically, the hippocampus is a stress-sensitive region which may be structurally impacted by chronic TN pain. As the center of the emotion-related network, the amygdala is closely related to stress regulation and may be associated with TN pain as well. The thalamus, which is involved in the trigeminal sensory pathway and nociception, may play a role in pain processing of TN. The objective of this study was to assess structural alterations in the trigeminal nerve and subregions of the hippocampus, amygdala, and thalamus in TN patients using ultra-high field MRI and examine quantitative differences in these structures compared with healthy controls. Methods: Thirteen TN patients and 13 matched controls were scanned at 7-Tesla MRI with high resolution, T1- weighted imaging. Nerve cross sectional area (CSA) was measured and an automated algorithm was used to segment hippocampal, amygdaloid, and thalamic subregions. Nerve CSA and limbic structure subnuclei volumes were compared between TN patients and controls. Results: CSA of the posterior cisternal nerve on the symptomatic side was smaller in patients (3.75mm2) compared with side-matched controls (5.77mm2, p = 0.006). In TN patients, basal subnucleus amygdala volume (0.347mm3) was reduced on the symptomatic side compared with controls (0.401mm3, p = 0.025) and the paralaminar subnucleus volume (0.04mm3) was also reduced on the symptomatic side compared with controls (0.05mm3, p = 0.009). The central lateral thalamic subnucleus was larger in TN patients on both the symptomatic side (0.033mm3) and asymptomatic side (0.035mm3), compared with the corresponding sides in controls (0.025mm3 on both sides, p = 0.048 and p = 0.003 respectively). The inferior and lateral pulvinar thalamic subnuclei were both reduced in TN patients on the symptomatic side (0.2mm3 and 0.17mm3 respectively) compared to controls (0.23mm3, p = 0.04 and 0.18 mm3, p = 0.04 respectively). No significant findings were found in the hippocampal subfields analyzed. Conclusions: These findings, generated through a highly sensitive 7 T MRI protocol, provide compelling support for the theory that TN neurobiology is a complex amalgamation of local structural changes within the trigeminal nerve and structural alterations in subnuclei of limbic structures directly and indirectly involved in nociception and pain processing

Boston/Montréal

Falk outlines the premises which guided his choices for the Montreal representation, while Shlien discusses the differences and similitudes between the 14 participants from Boston and Montreal. Text by or on each of the artists. Biographical notes. Texts not translated

A multinational Delphi consensus to end the COVID-19 public health threat

Abstract Despite notable scientific and medical advances, broader political, socioeconomic and behavioural factors continue to undercut the response to the COVID-19 pandemic 1,2 . Here we convened, as part of this Delphi study, a diverse, multidisciplinary panel of 386 academic, health, non-governmental organization, government and other experts in COVID-19 response from 112 countries and territories to recommend specific actions to end this persistent global threat to public health. The panel developed a set of 41 consensus statements and 57 recommendations to governments, health systems, industry and other key stakeholders across six domains: communication; health systems; vaccination; prevention; treatment and care; and inequities. In the wake of nearly three years of fragmented global and national responses, it is instructive to note that three of the highest-ranked recommendations call for the adoption of whole-of-society and whole-of-government approaches 1 , while maintaining proven prevention measures using a vaccines-plus approach 2 that employs a range of public health and financial support measures to complement vaccination. Other recommendations with at least 99% combined agreement advise governments and other stakeholders to improve communication, rebuild public trust and engage communities 3 in the management of pandemic responses. The findings of the study, which have been further endorsed by 184 organizations globally, include points of unanimous agreement, as well as six recommendations with >5% disagreement, that provide health and social policy actions to address inadequacies in the pandemic response and help to bring this public health threat to an end