European Ultrahigh-Field Imaging Network for Neurodegenerative Diseases (EUFIND)

Introduction

The goal of European Ultrahigh-Field Imaging Network in Neurodegenerative Diseases (EUFIND) is to identify opportunities and challenges of 7 Tesla (7T) MRI for clinical and research applications in neurodegeneration. EUFIND comprises 22 European and one US site, including over 50 MRI and dementia experts as well as neuroscientists.

Methods

EUFIND combined consensus workshops and data sharing for multisite analysis, focusing on 7 core topics: clinical applications/clinical research, highest resolution anatomy, functional imaging, vascular systems/vascular pathology, iron mapping and neuropathology detection, spectroscopy, and quality assurance. Across these topics, EUFIND considered standard operating procedures, safety, and multivendor harmonization.

Results

The clinical and research opportunities and challenges of 7T MRI in each subtopic are set out as a roadmap. Specific MRI sequences for each subtopic were implemented in a pilot study presented in this report. Results show that a large multisite 7T imaging network with highly advanced and harmonized imaging sequences is feasible and may enable future multicentre ultrahigh-field MRI studies and clinical trials.

Discussion

The EUFIND network can be a major driver for advancing clinical neuroimaging research using 7T and for identifying use-cases for clinical applications in neurodegeneration.

Comparison of accelerated T1-weighted whole-brain structural-imaging protocols

Imaging in neuroscience, clinical research and pharmaceutical trials often employs the 3D magnetisation-prepared rapid gradient-echo (MPRAGE) sequence to obtain structural T1-weighted images with high spatial resolution of the human brain. Typical research and clinical routine MPRAGE protocols with ~1mm isotropic resolution require data acquisition time in the range of 5-10min and often use only moderate two-fold acceleration factor for parallel imaging. Recent advances in MRI hardware and acquisition methodology promise improved leverage of the MR signal and more benign artefact properties in particular when employing increased acceleration factors in clinical routine and research. In this study, we examined four variants of a four-fold-accelerated MPRAGE protocol (2D-GRAPPA, CAIPIRINHA, CAIPIRINHA elliptical, and segmented MPRAGE) and compared clinical readings, basic image quality metrics (SNR, CNR), and automated brain tissue segmentation for morphological assessments of brain structures. The results were benchmarked against a widely-used two-fold-accelerated 3T ADNI MPRAGE protocol that served as reference in this study. 22 healthy subjects (age=20-44yrs.) were imaged with all MPRAGE variants in a single session. An experienced reader rated all images of clinically useful image quality. CAIPIRINHA MPRAGE scans were perceived on average to be of identical value for reading as the reference ADNI-2 protocol. SNR and CNR measurements exhibited the theoretically expected performance at the four-fold acceleration. The results of this study demonstrate that the four-fold accelerated protocols introduce systematic biases in the segmentation results of some brain structures compared to the reference ADNI-2 protocol. Furthermore, results suggest that the increased noise levels in the accelerated protocols play an important role in introducing these biases, at least under the present study conditions.

Nicotine effects on brain function during a visual oddball task: a comparison between conventional and EEG-informed fMRI analysis

In a previous oddball task study, it was shown that the inclusion of electrophysiology (EEG), that is, single-trial P3 ERP parameters, in the analysis of fMRI responses can detect activation that is not apparent with conventional fMRI data modeling strategies [Warbrick, T., Mobascher, A., Brinkmeyer, J., Musso, F., Richter, N., Stoecker, T., et al. Single-trial P3 amplitude and latency informed event-related fMRI models yield different BOLD response patterns to a target detection task. Neuroimage, 47, 1532-1544, 2009]. Given that P3 is modulated by nicotine, including P3 parameters in the fMRI analysis might provide additional information about nicotine effects on brain function. A 1-mg nasal nicotine spray (0.5 mg each nostril) or placebo (pepper) spray was administered in a double-blind, placebo-controlled, within-subject, randomized, cross-over design. Simultaneous EEG-fMRI and behavioral data were recorded from 19 current smokers in response to an oddball-type visual choice RT task. Conventional general linear model analysis and single-trial P3 amplitude informed general linear model analysis of the fMRI data were performed. Comparing the nicotine with the placebo condition, reduced RTs in the nicotine condition were related to decreased BOLD responses in the conventional analysis encompassing the superior parietal lobule, the precuneus, and the lateral occipital cortex. On the other hand, reduced RTs were related to increased BOLD responses in the precentral and postcentral gyri, and ACC in the EEG-informed fMRI analysis. Our results show how integrated analyses of simultaneous EEG-fMRI data can be used to detect nicotine effects that would not have been revealed through conventional analysis of either measure in isolation. This emphasizes the significance of applying multimodal imaging methods to pharmacoimaging.

Single-trial P3 amplitude and latency informed event-related fMRI models yield different BOLD response patterns to a target detection task

Using single-trial parameters as a regressor in the General Linear Model (GLM) is becoming an increasingly popular method for informing fMRI analysis. However, the parameter used to characterise or to differentiate brain regions involved in the response to a particular task varies across studies (e.g. ERP amplitude, ERP latency, reaction time). Furthermore, the way in which the single-trial information is used in the fMRI analysis is also important. For example, the single-trial parameters can be used as regressors in the GLM or to modify the duration of the events modelled in the GLM. The aim of this study was to investigate the BOLD response to a target detection task when including P3 amplitude, P3 latency and reaction time parameters in the GLM. Simultaneous EEG-fMRI was recorded from fifteen subjects in response to a visual choice reaction time task. Including P3 amplitude as a regressor in the GLM yielded activation in left central opercular cortex, left postcentral gyrus, left insula, left middle frontal gyrus, left insula and left parietal operculum. Using P3 latency and reaction time as an additional regressor yielded no additional activation in comparison with the conventional fMRI analysis. However, when P3 latency or reaction time was used to determine the duration of events at a single-trial level, additional activation was observed in the left postcentral gyrus, left precentral gyrus, anterior cingulate cortex and supramarginal gyrus. Our findings suggest that ERP amplitudes and latencies can yield different activation patterns when used to modify relevant aspects of the GLM.

Emotional processing in male adolescents with childhood-onset conduct disorder

BACKGROUND

Boys with early onset of conduct disorder (CD), most of whom also meet diagnostic criteria of a comorbid attention deficit hyperactivity disorder (ADHD), tend to exhibit high levels of aggression throughout development. While a number of functional neuroimaging studies on emotional processing have been performed in antisocial adults, little is known about how CD children process emotional information.

METHOD

Functional magnetic resonance imaging data were analyzed in 22 male adolescents aged 12 to 17 years with childhood-onset CD (16 of them with comorbid ADHD) compared to 22 age-matched male healthy controls. In order to consider the likely confounding of results through ADHD comorbidity, we performed a supplementary study including 13 adolescent subjects with pure ADHD who were compared with healthy controls. To challenge emotional processing of stimuli, a passive viewing task was applied, presenting pictures of negative, positive or neutral valence.

RESULTS

When comparing CD/combined disorder patients with healthy controls, we found enhanced left-sided amygdala activation in response to negative pictures as compared to neutral pictures in the patient group. In addition, these boys exhibited no reduced activation in the orbitofrontal, anterior cingulate and insular cortices. By contrast, children with pure ADHD did not show any abnormalities in amygdala activation but showed decreased neural activity in the insula only in response to negative pictures.

CONCLUSIONS

Increased rather than reduced amygdala activation found in our study may indicate an enhanced response to environmental cues in adolescents with early-onset CD (most of whom also met the condition of ADHD), and is not consistent with the assumption of a reduced capacity to take note of affective information in the social environment. Further studies with an emphasis on developmental aspects of affect regulation are needed to clarify the relationship between CD and adult personality pathology associated with different modes of persistent antisocial behavior.

Development and implementation of an MR-compatible whole body video system

In conventional fMRI, the possibilities for remote visual monitoring of a volunteer or patient during scanning are very limited. However, performance during motor paradigms, monitoring of ventilated patients, or patients with movement disorders is often of particular interest. In order to facilitate remote visual monitoring during MRI examinations, an MR-compatible video system was developed and implemented to allow monitoring of the face and the body, separately, with two cameras. The system reliably allows the recording of video data during MRI scanning without affecting MR image quality. The applicability of the system for the online recording of tics during an fMRI study with Tourette patients is demonstrated. Monitoring of a motor task in healthy controls and Tourette patients was possible with exact synchronisation to the fMRI paradigm. Details of system set up and example control measurements are presented. Further, electronic and mechanical components are described in detail enabling easy reproduction of the system.