Magnetic Resonance Imaging technology — bridging the gap between noninvasive human imaging and optical microscopy

Polimeni, Jon̈athan R.; Wald, Lawrence L.

doi:10.1016/j.conb.2018.04.026

Cited by 21 publications

(10 citation statements)

References 115 publications

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“…Therefore, most of the current concepts that support the existence of a hypothalamic abnormal function in obesity were obtained in experimental studies, particularly in rodents. However, this obstacle has been partially overcome by the rapid advance in the development of methods employed in neuroimaging [20][21][22]. A wide variety of neuroimaging approaches have been utilized to query hypothalamic function and structure in obesity (Supplemental Table 2).…”

Section: Discussionmentioning

confidence: 99%

Radiologic evidence that hypothalamic gliosis is improved after bariatric surgery in obese women with type 2 diabetes

et al. 2019

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Background/Objectives-Hypothalamic neurons play a major role in the control of body mass. Obese subjects present radiologic signs of gliosis in the hypothalamus, which may reflect the damage or loss of neurons involved in whole-body energy homeostasis. It is currently unknown if hypothalamic gliosis (1) differs between obese nondiabetic (ND) and obese diabetic subjects (T2D) or (2) is modified by extensive body mass reduction via Roux-n-Y gastric bypass (RYGB). Subjects/Methods-Fifty-five subjects (all female) including lean controls (CT; n = 13), ND (n = 28), and T2D (n = 14) completed at least one study visit. Subjects underwent anthropometrics and a multi-echo MRI sequence to measure mean bilateral T2 relaxation time in the mediobasal hypothalamus (MBH) and two reference regions (amygdala and putamen). The obese groups underwent RYGB and were re-evaluated 9 months later. Analyses were by linear mixed models. Results-Analyses of T2 relaxation time at baseline showed a group by region interaction only in the MBH (P < 0.0001). T2D had longer T2 relaxation times compared to either CT or ND groups. To examine the effects of RYGB on hypothalamic gliosis a three-way (group by region by time) mixed effects model adjusted for age was executed. Group by region (P < 0.0001) and region Licio A. Velloso,

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Section: Discussionmentioning

confidence: 99%

Radiologic evidence that hypothalamic gliosis is improved after bariatric surgery in obese women with type 2 diabetes

et al. 2019

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“…Technical limitations include the engineering challenges of achieving a spatially linear magnetic gradient field, removal of heat from the gradient coil, and efficiency and power requirements of the coil. While these technical challenges have largely been addressed in the modern era, including advances in gradient and shim technology [ 113 – 115 ], the main limiting factor on gradient coil performance is the biological effect of rapidly switching, large magnetic fields on the human body. Peripheral nerve stimulation (PNS) can be induced if the product of the gradient switching rate and strength generate electric fields large enough to trigger nerve firing, which can be uncomfortable and potentially painful.…”

Section: Ultra-high and Ultrafast Gradient Technologymentioning

confidence: 99%

MRI with ultrahigh field strength and high-performance gradients: challenges and opportunities for clinical neuroimaging at 7 T and beyond

Vachha

Huang

2021

Eur Radiol Exp

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Research in ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient technology has provided enormous gains in sensitivity, resolution, and contrast for neuroimaging. This article provides an overview of the technical advantages and challenges of performing clinical neuroimaging studies at ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient technology. Emerging clinical applications of 7-T MRI and state-of-the-art gradient systems equipped with up to 300 mT/m gradient strength are reviewed, and the impact and benefits of such advances to anatomical, structural and functional MRI are discussed in a variety of neurological conditions. Finally, an outlook and future directions for ultrahigh field MRI combined with ultrahigh and ultrafast gradient technology in neuroimaging are examined.

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“…Dramatic improvements in functional Magnetic Resonance Imaging (fMRI) technology in recent years, including significant advances in hardware and image reconstruction (Polimeni & Wald 2018, Ugurbil 2018, Wald 2012, Yu et al 2014, have enabled resolution of cortical layers bringing us one step closer to the spatial scale of local neuronal circuits (Dumoulin et al 2018, Goense et al 2016, Polimeni et al 2010, Turner 2016. Indeed, neuronal circuits in cerebral cortex are organized in layers that differ in their cellular density, composition and wiring (Helmstaedter et al 2007, Woolsey & Van der Loos 1970, as well as the density of mitochondrial cytochrome oxidase, a marker of O 2 metabolism (Wong-Riley 1989).…”

Section: Introductionmentioning

confidence: 99%

Microscopic Quantification of Oxygen Consumption across Cortical Layers

Mächler

Fomin-Thunemann²,

Thunemann³

et al. 2021

Preprint

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The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily revealed by staining for cytochrome oxidase – the last enzyme in the respiratory electron transport chain located in the inner mitochondrial membrane. It has been hypothesized that a high-density band of cytochrome oxidase in cortical layer IV reflects higher oxygen consumption under baseline (unstimulated) conditions. Here, we tested the above hypothesis using direct measurements of the partial pressure of O 2 (pO 2 ) in cortical tissue by means of 2-photon phosphorescence lifetime microscopy (2PLM). We revisited our previously developed method for extraction of the cerebral metabolic rate of O 2 (CMRO 2 ) based on 2-photon pO 2 measurements around diving arterioles and applied this method to estimate baseline CMRO 2 in awake mice across cortical layers. To our surprise, our results revealed a decrease in baseline CMRO 2 from layer I to layer IV . This decrease of CMRO 2 with cortical depth was paralleled by an increase in tissue oxygenation. Higher baseline oxygenation and cytochrome density in layer IV may serve as an O 2 reserve during surges of neuronal activity or certain metabolically active brain states rather than baseline energy needs. Our study provides the first quantification of microscopically resolved CMRO 2 across cortical layers as a step towards informed interpretation and modeling of cortical-layer-specific Blood Oxygen Level Dependent (BOLD) fMRI signals.

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Magnetic Resonance Imaging technology — bridging the gap between noninvasive human imaging and optical microscopy

Cited by 21 publications

References 115 publications

Radiologic evidence that hypothalamic gliosis is improved after bariatric surgery in obese women with type 2 diabetes

Radiologic evidence that hypothalamic gliosis is improved after bariatric surgery in obese women with type 2 diabetes

MRI with ultrahigh field strength and high-performance gradients: challenges and opportunities for clinical neuroimaging at 7 T and beyond

Microscopic Quantification of Oxygen Consumption across Cortical Layers

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