Unraveling the multiscale structural organization and connectivity of the human brain: the role of diffusion MRI

The structural architecture and the anatomical connectivity of the human brain show different organizational principles at distinct spatial scales. Histological staining and light microscopy techniques have been widely used in classical neuroanatomical studies to unravel brain organization. Using such techniques is a laborious task performed on 2-dimensional histological sections by skilled anatomists possibly aided by semi-automated algorithms. With the recent advent of modern magnetic resonance imaging (MRI) contrast mechanisms, cortical layers and columns can now be reliably identified and their structural properties quantified post-mortem. These developments are allowing the investigation of neuroanatomical features of the brain at a spatial resolution that could be interfaced with that of histology. Diffusion MRI and tractography techniques, in particular, have been used to probe the architecture of both white and gray matter in three dimensions. Combined with mathematical network analysis, these techniques are increasingly influential in the investigation of the macro-, meso-, and microscopic organization of brain connectivity and anatomy, both in vivo and ex vivo. Diffusion MRI-based techniques in combination with histology approaches can therefore support the endeavor of creating multimodal atlases that take into account the different spatial scales or levels on which the brain is organized. The aim of this review is to illustrate and discuss the structural architecture and the anatomical connectivity of the human brain at different spatial scales and how recently developed diffusion MRI techniques can help investigate these

The association between inadequate sleep and accelerated brain ageing

Numerous studies indicate large heterogeneity in brain ageing, which can be attributed to modifiable lifestyle factors, including sleep. Inadequate sleep has been previously linked to gray (GM) and white (WM) matter changes. However, the reported findings are highly inconsistent. By contrast to previous research independently characterizing patterns of either GM or WM changes, we used here linked independent component analysis (FLICA) to examine covariation in GM, and WM in a group of older adults (n = 50). Next, we employed a novel technique to estimate the brain age delta (difference between chronological and brain age assessed using neuroimaging data) and study its associations with sleep quality and sleep fragmentation, hypothesizing that inadequate sleep accelerates brain ageing. FLICA revealed a number of multimodal components, associated with age, sleep quality, and sleep fragmentation. Subsequently, we show significant associations between brain age delta and inadequate sleep, suggesting 2 years deviation above the chronological age. Our findings indicate sensitivity of multimodal approaches and brain age delta in detecting link between inadequate sleep and accelerated brain ageing

White matter microstructural changes in adolescent anorexia nervosa including an exploratory longitudinal study

AbstractBackgroundAnorexia nervosa (AN) often begins in adolescence, however, the understanding of the underlying pathophysiology at this developmentally important age is scarce, impeding early interventions. We used diffusion tensor imaging (DTI) to investigate microstructural white matter (WM) brain changes including an experimental longitudinal follow-up.MethodsWe acquired whole brain diffusion-weighted brain scans of 22 adolescent female hospitalized patients with AN at admission and nine patients longitudinally at discharge after weight rehabilitation. Patients (10–18years) were compared to 21 typically developing controls (TD). Tract-based spatial statistics (TBSS) were applied to compare fractional anisotropy (FA) across groups and time points. Associations between average FA values of the global WM skeleton and weight as well as illness duration parameters were analyzed by multiple linear regression.ResultsWe observed increased FA in bilateral frontal, parietal and temporal areas in AN patients at admission compared to TD. Higher FA of the global WM skeleton at admission was associated with faster weight loss prior to admission. Exploratory longitudinal analysis showed this FA increase to be partially normalized after weight rehabilitation.ConclusionsOur findings reveal a markedly different pattern of WM microstructural changes in adolescent AN compared to most previous results in adult AN. This could signify a different susceptibility and reaction to semi-starvation in the still developing brain of adolescents or a time-dependent pathomechanism differing with extend of chronicity. Higher FA at admission in adolescents with AN could point to WM fibers being packed together more closely

What's new and what's next in diffusion MRI preprocessing

Diffusion MRI (dMRI) provides invaluable information for the study of tissue microstructure and brain connectivity, but suffers from a range of imaging artifacts that greatly challenge the analysis of results and their interpretability if not appropriately accounted for. This review will cover dMRI artifacts and preprocessing steps, some of which have not typically been considered in existing pipelines or reviews, or have only gained attention in recent years: brain/skull extraction, B-matrix incompatibilities w.r.t the imaging data, signal drift, Gibbs ringing, noise distribution bias, denoising, between- and within-volumes motion, eddy currents, outliers, susceptibility distortions, EPI Nyquist ghosts, gradient deviations, bias fields, and spatial normalization. The focus will be on “what’s new” since the notable advances prior to and brought by the Human Connectome Project (HCP), as presented in the predecessing issue on “Mapping the Connectome” in 2013. In addition to the development of novel strategies for dMRI preprocessing, exciting progress has been made in the availability of open source tools and reproducible pipelines, databases and simulation tools for the evaluation of preprocessing steps, and automated quality control frameworks, amongst others. Finally, this review will consider practical considerations and our view on “what’s next” in dMRI preprocessing

Confound modelling in UK Biobank brain imaging

© 2020 Dealing with confounds is an essential step in large cohort studies to address problems such as unexplained variance and spurious correlations. UK Biobank is a powerful resource for studying associations between imaging and non-imaging measures such as lifestyle factors and health outcomes, in part because of the large subject numbers. However, the resulting high statistical power also raises the sensitivity to confound effects, which therefore have to be carefully considered. In this work we describe a set of possible confounds (including non-linear effects and interactions that researchers may wish to consider for their studies using such data). We include descriptions of how we can estimate the confounds, and study the extent to which each of these confounds affects the data, and the spurious correlations that may arise if they are not controlled. Finally, we discuss several issues that future studies should consider when dealing with confounds

A Case-Control Comparison of Surgical and Functional Outcomes of Robotic-Assisted Spleen-Preserving Left Side Pancreatectomy versus Pure Laparoscopy

Aim During left-sided spleen-preserving pancreatectomy (SPLP), limitations of laparoscopy may require spleen sacrifice or conversion to maintain patient safety. The objective of our study is to compare surgical and functional outcomes of robot-assisted and pure laparoscopic SPLP in patients with benign or borderline lesions of the body/tail of the pancreas. Patients and methods This was a case-matched study: fifteen patients who had robotic SPLP (R-SPLP) were matched with 15 comparable patients who had pure laparoscopic SPLP (L-SPLP). The peri-operative variables (conversion rate, amount of bleeding, operation time, length of hospital stay, complications, mortality and readmission) as well as the spleen preservation rate were compared between the two groups, The European Organisation for Research and Treatment of Cancer QLQ-C30 (EORTC QLQ-C30) specific questionnaires were used in each arm after at least 1 year of follow up in order to evaluate quality of life (QoL). Results No R-SPLP was converted to conventional laparoscopy, hand-assisted laparoscopy, or open surgery whereas L-SPLP had a conversion rate of 13.3% (p=n.s.); also fistula formation (20% vs. 46%; p=n.s.) was higher in the laparoscopic group although not statistically significant. Mean operative time (220 vs. 279 min; p=0.027) was shorter and the spleen-preserving rate (fail/ success, 0/15 vs. 4/11; p=0.03) of R-SPLP was significantly better compared to L-SPLP. Moreover, length of hospital stay was significantly shorter in the R-SPLP group compared to the L-SPLP group (6.5 vs. 8.8 days; p=0.04). Post-operative high grade surgical complications occurred only in one L-SPLP patient (0% vs. 6.6%; p=n.s.). Quality of life scores were not significantly different between the two groups. Conclusions R-SPLP could provide an increased chance for spleen preservation and faster surgical procedure. Furthermore, fistula formation and conversion rate seem to be lower, reducing the length of the hospital stay. Our case matched study confirmed the potential peri-operative benefits of robotic assistance in this setting, however these benefits did not translate into a better quality of life at least one year post-operatively

Assessing microstructural substrates of white matter abnormalities: a comparative study using DTI and NODDI

Neurite orientation dispersion and density imaging (NODDI) enables more specific characterization of tissue microstructure by estimating neurite density (NDI) and orientation dispersion (ODI), two key contributors to fractional anisotropy (FA). The present work compared NODDI- with diffusion tensor imaging (DTI)-derived indices for investigating white matter abnormalities in a clinical sample. We assessed the added value of NODDI parameters over FA, by contrasting group differences identified by both models. Diffusion-weighted images with multiple shells were acquired in a group of 8 healthy controls and 8 patients with an inherited metabolic disease. Both standard DTI and NODDI analyses were performed. Tract based spatial statistics (TBSS) was used for group inferences, after which overlap and unique contributions across different parameters were evaluated. Results showed that group differences in NDI and ODI were complementary, and together could explain much of the FA results. Further, compared to FA analysis, NDI and ODI gave a pattern of results that was more regionally specific and were able to capture additional discriminative voxels that FA failed to identify. Finally, ODI from single-shell NODDI analysis, but not NDI, was found to reproduce the group differences from the multi-shell analysis. To conclude, by using a clinically feasible acquisition and analysis protocol, we demonstrated that NODDI is of added value to standard DTI, by revealing specific microstructural substrates to white matter changes detected with FA. As the (simpler) DTI model was more sensitive in identifying group differences, NODDI is recommended to be used complementary to DTI, thereby adding greater specificity regarding microstructural underpinnings of the differences. The finding that ODI abnormalities can be identified reliably using single-shell data may allow the retrospective analysis of standard DTI with NODDI

A prospective, single-arm study on the use of the da Vinci® Table Motion with the Trumpf TS7000dV operating table

BACKGROUND: The da Vinci® Table Motion (dVTM) comprises a combination of a unique operating table (Trumpf Medical™ TruSystem® 7000dV) capable of isocenter motion connected wirelessly with the da Vinci Xi® robotic platform, thereby enabling patients to be repositioned without removal of instruments and or undocking the robot. MATERIALS AND METHODS: Between May 2015 to October 2015, the first human use of dVTM was carried out in this prospective, single-arm, post-market study in the EU, for which 40 patients from general surgery (GS), urology (U), or gynecology (G) were enrolled prospectively. Primary endpoints of the study were dVTM feasibility, efficacy, and safety. RESULTS:Surgeons from the three specialties obtained targeting success and the required table positioning in all cases. Table movement/repositioning was necessary to gain exposure of the operating field in 106/116 table moves (91.3%), change target in 2/116 table moves (1.7%), achieve hemodynamic relief in 4/116 table moves (3.5%), and improve external access for tumor removal in 4/116 table moves (3.5%). There was a significantly higher use of tilt and tilt plus Trendelenburg in GS group (GS vs. U p = 0.055 and GS vs. G p = 0.054). There were no dVTM safety-related or adverse events. CONCLUSIONS: The dVTM with TruSystem 7000dV operating table in wireless communication with the da Vinci Xi is a perfectly safe and effective synergistic combination, which allows repositioning of the patient whenever needed without imposing any delay in the execution of the operation. Moreover, it is helpful in avoiding extreme positions and enables the anesthesiologist to provide immediate and effective hemodynamic relief to the patient when needed

Non-invasive assessment of gastric secretory function in centenarians

Gastric acid secretion is believed to decrease in the aging stomach, but the number of elderly patients on proton pump inhibitor (PPI) therapy is increasing. The aim was to assess gastric function by means of serology (PGI, PGII, G17 and IgG antibodies against Helicobacter pylori) in centenarians. Twenty-five centenarians (2 males, 23 females, mean age 101.3 years, range 100- 106 years) underwent to serological gastric markers assessment by means of Gastropanel®. Patients with laboratory signs of severe oxyntic gastric atrophy (OGA) underwent gastroscopy with biopsy samples. Twelve patients (48.0%) had serological values according to normal gastric secretion; 3 patients (12%) had serological values according to severe OGA, confirmed by histology; 21 patients (84.0%) had serological values according to H. pylori infection. Acid secretion seems to be preserved in a large part of centenarians. Serological markers may be helpful to identify patients affected by OGA, in whom the administration of PPI is inappropriate