Real‐time motion and retrospective coil sensitivity correction for CEST using volumetric navigators (vNavs) at 7T

PURPOSE: To explore the impact of temporal motion-induced coil sensitivity changes on CEST-MRI at 7T and its correction using interleaved volumetric EPI navigators, which are applied for real-time motion correction. METHODS: Five healthy volunteers were scanned via CEST. A 4-fold correction pipeline allowed the mitigation of (1) motion, (2) motion-induced coil sensitivity variations, Δ B 1 - , (3) motion-induced static magnetic field inhomogeneities, ΔB0 , and (4) spatially varying transmit RF field fluctuations, ΔB 1 + . Four CEST measurements were performed per session. For the first 2, motion correction was turned OFF and then ON in absence of voluntary motion, whereas in the other 2 controlled head rotations were performed. During post-processing Δ B 1 - was removed additionally for the motion-corrected cases, resulting in a total of 6 scenarios to be compared. In all cases, retrospective ∆B0 and - ΔB 1 + corrections were performed to compute artifact-free magnetization transfer ratio maps with asymmetric analysis (MTRasym ). RESULTS: Dynamic Δ B 1 - correction successfully mitigated signal deviations caused by head motion. In 2 frontal lobe regions of volunteer 4, induced relative signal errors of 10.9% and 3.9% were reduced to 1.1% and 1.0% after correction. In the right frontal lobe, the motion-corrected MTRasym contrast deviated 0.92%, 1.21%, and 2.97% relative to the static case for Δω = 1, 2, 3 ± 0.25 ppm. The additional application of Δ B 1 - correction reduced these deviations to 0.10%, 0.14%, and 0.42%. The fully corrected MTRasym values were highly consistent between measurements with and without intended head rotations. CONCLUSION: Temporal Δ B 1 - cause significant CEST quantification bias. The presented correction pipeline including the proposed retrospective Δ B 1 - correction significantly reduced motion-related artifacts on CEST-MRI

Real-time motion and retrospective coil sensitivity correction for CEST using volumetric navigators (vNavs) at 7T

Purpose To explore the impact of temporal motion-induced coil sensitivity changes on CEST-MRI at 7T and its correction using interleaved volumetric EPI navigators, which are applied for real-time motion correction. Methods Five healthy volunteers were scanned via CEST. A 4-fold correction pipeline allowed the mitigation of (1) motion, (2) motion-induced coil sensitivity variations, Delta B1-, (3) motion-induced static magnetic field inhomogeneities, Delta B-0, and (4) spatially varying transmit RF field fluctuations, Delta B1+. Four CEST measurements were performed per session. For the first 2, motion correction was turned OFF and then ON in absence of voluntary motion, whereas in the other 2 controlled head rotations were performed. During post-processing Delta B1- was removed additionally for the motion-corrected cases, resulting in a total of 6 scenarios to be compared. In all cases, retrospective increment B-0 and -Delta B1+ corrections were performed to compute artifact-free magnetization transfer ratio maps with asymmetric analysis (MTRasym). Results Dynamic Delta B1- correction successfully mitigated signal deviations caused by head motion. In 2 frontal lobe regions of volunteer 4, induced relative signal errors of 10.9% and 3.9% were reduced to 1.1% and 1.0% after correction. In the right frontal lobe, the motion-corrected MTRasym contrast deviated 0.92%, 1.21%, and 2.97% relative to the static case for Delta omega = 1, 2, 3 +/- 0.25 ppm. The additional application of Delta B1- correction reduced these deviations to 0.10%, 0.14%, and 0.42%. The fully corrected MTRasym values were highly consistent between measurements with and without intended head rotations. Conclusion Temporal Delta B1- cause significant CEST quantification bias. The presented correction pipeline including the proposed retrospective Delta B1- correction significantly reduced motion-related artifacts on CEST-MRI.Peer reviewe

High field brain proton magnetic resonance spectroscopy and volumetry in children with chronic, compensated liver disease - A pilot study.

There is increasing evidence that children or young adults having acquired liver disease in childhood display neurocognitive impairment which may become more apparent as they grow older. The molecular, cellular and morphological underpinnings of this clinical problem are incompletely understood. Therefore, we used the advantages of highly-resolved proton magnetic resonance spectroscopy at ultra-high magnetic field to analyze the neurometabolic profile and brain morphometry of children with chronic, compensated liver disease, hypothesizing that with high field spectroscopy we would identify early evidence of rising brain glutamine and decreased myoinositol, such as has been described both in animals and humans with more significant liver disease. Patients (n = 5) and age-matched controls (n = 19) underwent 7T MR scans and short echo time <sup>1</sup> H MR spectra were acquired using the semi-adiabatic SPECIAL sequence in two voxels located in gray and white matter dominated prefrontal cortex, respectively. A 3D MP2RAGE sequence was also acquired for brain volumetry and T <sub>1</sub> mapping. Liver disease had to have developed at least 6 months before entering the study. Subjects underwent routine blood analysis and neurocognitive testing using validated methods within 3 months of MRI and MRS. Five children aged 8-16 years with liver disease acquired in childhood were included. Baseline biological characteristics were similar among patients. There were no statistically significant differences between subjects and controls in brain metabolite levels or brain volumetry. Finally, there were minor neurocognitive fluctuations including attention deficit in one child, but none fell in the statistically significant range. Children with chronic, compensated liver disease did not display an abnormal neurometabolic profile, neurocognitive abnormalities, or signal intensity changes in the globus pallidus. Despite the absence of neurometabolic changes, it is an opportunity to emphasize that it is only by developing the use of <sup>1</sup> H MRS at high field in the clinical arena that we will understand the significance and generalizability of these findings in children with CLD. Healthy children displayed neurometabolic regional differences as previously reported in adult subjects

Behavioural disinhibition in the syndromes associated with frontotemporal lobar degeneration

The different clinical syndromes caused by frontotemporal lobar degeneration (FTLD) have highly heterogenous and overlapping features which complicate clinical and research practice. Behavioural impairments are associated with all FTLD syndromes, cause high morbidity and lack proven symptomatic treatments. Treatments for cognitive and behavioural impairment in other neurodegenerative diseases include restoration of neurotransmitter deficits. Deficits in the neurotransmitters glutamate and GABA occur in FTLD syndromes and are associated with behavioural disinhibition in other diseases. I propose that these neurotransmitter deficits contribute to behavioural change in FTLD syndromes. This thesis has two main aims. First, to develop a transdiagnostic approach to FTLD syndromes to facilitate a better understanding of aetiology, pathophysiology and in due course their symptomatic treatment. Second, to use this approach to test the hypothesis that glutamate and GABA deficits are associated with behavioural disinhibition in FTLD syndromes. In a cross-sectional epidemiological study, I examined 310 of 365 regional patients with a FTLD-associated syndrome, including behavioural variant frontotemporal dementia, the nonfluent and semantic variants of primary progressive aphasia, progressive supranuclear palsy and corticobasal syndrome. Multivariate analyses of clinical features and brain morphometry identified components that showed considerable overlap across the diagnostic groups. The transdiagnostic components of clinical features predicted neuropathology better than the current FTLD diagnostic labels. Behavioural disturbance, including disinhibition, was associated with reduced functionally independent survival, irrespective of diagnosis. Next, I investigated the role of glutamate and GABA in behavioural disinhibition. Ultrahigh-field magnetic resonance spectroscopy was used to measure glutamate and GABA in the frontal cortex of 44 patients with a FTLD syndrome and 20 healthy controls. Bayesian modelling of a response inhibition task was used to quantify behavioural disinhibition. Both neurotransmitters were reduced in the frontal cortex, but not occipital cortex, of patients compared to controls. Glutamate and GABA concentrations in the frontal cortex were inversely associated with behavioural disinhibition. In summary, the transdiagnostic approach provided new insights into the phenotypic heterogeneity in FTLD syndromes. Behavioural disinhibition, which can occur to a variable degree in all FTLD syndromes, was associated with reduced functionally independent survival. GABA and glutamate deficits in the frontal cortex are associated with behavioural disinhibition and are a potential target for future treatments.Holt Fellowshi

The 2nd International Electronic Conference on Applied Sciences

This book is focused on the works presented at the 2nd International Electronic Conference on Applied Sciences, organized by Applied Sciences from 15 to 31 October 2021 on the MDPI Sciforum platform. Two decades have passed since the start of the 21st century. The development of sciences and technologies is growing ever faster today than in the previous century. The field of science is expanding, and the structure of science is becoming ever richer. Because of this expansion and fine structure growth, researchers may lose themselves in the deep forest of the ever-increasing frontiers and sub-fields being created. This international conference on the Applied Sciences was started to help scientists conduct their own research into the growth of these frontiers by breaking down barriers and connecting the many sub-fields to cut through this vast forest. These functions will allow researchers to see these frontiers and their surrounding (or quite distant) fields and sub-fields, and give them the opportunity to incubate and develop their knowledge even further with the aid of this multi-dimensional network