Early career researchers want Open Science : Comment

Creative Commons Attribution License (CC BY 4.0)Open Science is encouraged by the European Union and many other political and scientific institutions.However, scientific practice is proving slow to change.We propose, as early career researchers, that it is our task to change scientific research into open scientific research and commit to Open Science principles.Non peer reviewe

Magnetic resonance imaging of cerebrovascular anatomy and physiology at 7 Tesla

Magnetic Resonance Imaging (MRI) can study the cerebrovasculature non-invasively in humans. It can image the vascular anatomy, as well as functional attributes such as flow and perfusion. This multi-modal capability renders MRI one of the most favourable imaging techniques to study the cerebrovasculature in research and in clinical settings. The advent of human 7 Tesla (7T) MRI offers further benefits to existing methods. Most evidently, the higher signal-to-noise ratio (SNR) can be used to improve resolution. However concomitant changes in contrast mechanisms, an increase in the specific absorption rate (SAR) and transmit B1-field inhomogeneity need to be addressed when transitioning to higher field. Vessel wall imaging (VWI) is an exemplar application that benefits from higher resolution but is based on SAR intense methods. In the first part of this thesis the implementation of a VWI method, DANTE-SPACE, is described. The readout scheme was specifically optimised for high resolution wall depiction and enhanced suppression of cerebrospinal fluid to produce vessel wall contrast in the major intracranial arteries at 7T. Besides refining spatial scales, recent technical developments have accelerated information content in the temporal domain. In-slice acceleration and simultaneous excitation of multiple slices substantially reduced acquisition times for many applications. In particular, multiband techniques have pushed sampling speeds in functional MRI (fMRI) to sub-second regimes. Traditionally, fMRI is used to study low frequency neuro-vascular signals below 0.1Hz. Aliases of cardio-respiratory-induced signals have been regarded as "physiological noise". Sufficiently fast sampling resolves the spectrum beyond the cardiac frequency, thus transforming noise into valuable signal. In the second part of this thesis strategies to map and quantify signal fluctuations at the cardiac frequency are described using echo-planar imaging (EPI). Potential age-related difference in the cardiac EPI signal power were studied. Also, an investigation was made into the underlying MR-mechanisms that form these fluctuations by decomposing the EPI-signal over the cardiac cycle into S0 and T2&amp;ast; waveforms. Ultimately this research aims to foster the understanding of the vascular origins of cardiac-induced EPI signals. This will hopefully serve future research into how EPI data can be exploited to study cerebrovascular properties in healthy and diseased states.</p

Magnetic resonance imaging of cerebrovascular anatomy and physiology at 7 Tesla

Magnetic Resonance Imaging (MRI) can study the cerebrovasculature non-invasively in humans. It can image the vascular anatomy, as well as functional attributes such as flow and perfusion. This multi-modal capability renders MRI one of the most favourable imaging techniques to study the cerebrovasculature in research and in clinical settings. The advent of human 7 Tesla (7T) MRI offers further benefits to existing methods. Most evidently, the higher signal-to-noise ratio (SNR) can be used to improve resolution. However concomitant changes in contrast mechanisms, an increase in the specific absorption rate (SAR) and transmit B1-field inhomogeneity need to be addressed when transitioning to higher field. Vessel wall imaging (VWI) is an exemplar application that benefits from higher resolution but is based on SAR intense methods. In the first part of this thesis the implementation of a VWI method, DANTE-SPACE, is described. The readout scheme was specifically optimised for high resolution wall depiction and enhanced suppression of cerebrospinal fluid to produce vessel wall contrast in the major intracranial arteries at 7T. Besides refining spatial scales, recent technical developments have accelerated information content in the temporal domain. In-slice acceleration and simultaneous excitation of multiple slices substantially reduced acquisition times for many applications. In particular, multiband techniques have pushed sampling speeds in functional MRI (fMRI) to sub-second regimes. Traditionally, fMRI is used to study low frequency neuro-vascular signals below 0.1Hz. Aliases of cardio-respiratory-induced signals have been regarded as "physiological noise". Sufficiently fast sampling resolves the spectrum beyond the cardiac frequency, thus transforming noise into valuable signal. In the second part of this thesis strategies to map and quantify signal fluctuations at the cardiac frequency are described using echo-planar imaging (EPI). Potential age-related difference in the cardiac EPI signal power were studied. Also, an investigation was made into the underlying MR-mechanisms that form these fluctuations by decomposing the EPI-signal over the cardiac cycle into S0 and T2&ast; waveforms. Ultimately this research aims to foster the understanding of the vascular origins of cardiac-induced EPI signals. This will hopefully serve future research into how EPI data can be exploited to study cerebrovascular properties in healthy and diseased states.</p

Double delay alternating with nutation for tailored excitation facilitates banding-free isotropic high-resolution intracranial vessel wall imaging

The purpose of this study was to evaluate the use of a double delay alternating with nutation for tailored excitation (D-DANTE)-prepared sequence for banding-free isotropic high-resolution intracranial vessel wall imaging (IC-VWI) and to compare its performance with regular DANTE in terms of signal-to-noise ratio (SNR) as well as cerebrospinal fluid (CSF) and blood suppression efficiency. To this end, a D-DANTE–prepared 3D turbo spin echo sequence was implemented by interleaving two separate DANTE pulse trains with different RF phase-cycling schemes, but keeping all other DANTE parameters unchanged, including the total number of pulses and total preparation time. This achieved a reduction of the banding distance compared with regular DANTE enabling banding-free imaging up to higher resolutions. Bloch simulations assuming static vessel wall and flowing CSF spins were performed to compare DANTE and D-DANTE in terms of SNR and vessel wall/CSF contrast. Similar image quality measures were assessed from measurements on 13 healthy middle-aged volunteers. Both simulation and in vivo results showed that D-DANTE had only slightly lower vessel wall/CSF and vessel wall/blood contrast-to-noise ratio values compared with regular DANTE, which originated from a 10%–15% reduction in vessel wall SNR but not from reduced CSF or blood suppression efficiency. As anticipated, IC-VWI acquisitions showed that D-DANTE can successfully remove banding artifacts compared with regular DANTE with equal scan time or DANTE preparation length. Moreover, application was demonstrated in a patient with an intracranial aneurysm, indicating improved robustness to slow flow artifacts compared with clinically available 3D turbo spin echo scans. In conclusion, D-DANTE provides banding artifact-free IC-VWI up to higher isotropic resolutions compared with regular DANTE. This allows for a more flexible choice of DANTE preparation parameters in high-resolution IC-VWI protocols