Ultra-high spatial resolution BOLD fMRI in humans using combined segmented-accelerated VFA-FLEET with a recursive RF pulse design

Purpose To alleviate the spatial encoding limitations of single-shot EPI by developing multi-shot segmented EPI for ultra-high-resolution fMRI with reduced ghosting artifacts from subject motion and respiration. Methods Segmented EPI can reduce readout duration and reduce acceleration factors, however, the time elapsed between segment acquisitions (on the order of seconds) can result in intermittent ghosting, limiting its use for fMRI. Here, "FLEET" segment ordering--where segments are looped over before slices--was combined with a variable flip angle progression (VFA-FLEET) to improve inter-segment fidelity and maximize signal for fMRI. Scaling a sinc pulse's flip angle for each segment (VFA-FLEET-Sinc) produced inconsistent slice profiles and ghosting, therefore, a recursive Shinnar-Le Roux (SLR) RF pulse design was developed (VFA-FLEET-SLR) to generate unique pulses for every segment that together produce consistent slice profiles and signals. Results The temporal stability of VFA-FLEET-SLR was compared against conventional-segmented EPI and VFA-FLEET-Sinc at 3 T and 7 T. VFA-FLEET-SLR showed reductions in both intermittent and stable ghosting compared to conventional-segmented and VFA-FLEET-Sinc, resulting in improved image quality with a minor trade-off in temporal SNR. Combining VFA-FLEET-SLR with acceleration, we achieved a 0.6-mm isotropic acquisition at 7 T--without zoomed imaging or partial Fourier--demonstrating reliable detection of BOLD responses to a visual stimulus. To counteract the increased repetition time from segmentation, simultaneous multi-slice VFA-FLEET-SLR was demonstrated using RF-encoded controlled aliasing. Conclusions VFA-FLEET with a recursive RF pulse design supports acquisitions with low levels of artifact and spatial blur, enabling fMRI at previously inaccessible spatial resolutions with a "full-brain" field of view.Comment: 51 pages (including supplement), 8 main figures, 6 supporting figures. For supporting videos (8), please visit https://github.com/aveberman/vfa-fleet. Note: this work has been accepted for publication at Magnetic Resonance in Medicin

L’accordo per la definizione della “vertenza fasce” degli anni 2010-2016: dal blocco delle relazioni sindacali al rilancio della progettazione dell’innovazione organizzativa nella Azienda Sanitaria di Matera

Riassunto: L’obiettivo del presente lavoro è di ripercorrere il percorso strategico-amministrativo che ha portato alla risoluzione della annosa problematica della “vertenza fasce” 2010-2016 nell’Azienda Sanitaria di Matera (ASM), conseguente all’ispezione MEF-RGS del 2018, con la quale veniva contestato un irregolare trasferimento permanente di risorse dal Fondo “Produttività” al Fondo “Posizione”. Inquadrato nell’ambito teorico del Management Strategico e della Public Service Motivation, il lavoro intende evidenziare: i) i passaggi necessari al raggiungimento dell’accordo (poi approvato dal MEFRGS nel 2020) con le organizzazioni sindacali; ii) come tale accordo abbia contribuito a sbloccare la paralisi dei processi produttivi, gestionali e d’innovazione organizzativa della ASM; iii) gli attuali risultati operativi dell’ASM dopo la positiva risoluzione della vertenzaThis work aims to retrace the strategic-managerial path that led to the resolution of the 2010-2016 “dispute on roles” in the Matera Health Authority (ASM). This controversy was consequent to the 2018 inspection from the Italian Ministry of Economy and Finance (MEF-RGS), which notified an irregular transfer of financial resources from the “Productivity” Fund to the “Position” one. Based on the theoretical background of Strategic Management and Public Service Motivation, the work highlights: i) the steps required to reach an agreement (MEF-RGS approved in 2020) with trade Unions; ii) how this agreement contributed to unjamming the paralysis of ASM management, operational and organizational innovation processes; iii) the current ASM results and outcomes, after the positive resolution of the dispute

Reliable 3D mapping of ocular dominance columns in humans using GE-EPI fMRI at 7 T

Since the discovery of the BOLD effect, detection of ocular dominance columns (ODCs) in primary visual cortex (V1) served as a benchmark for high-precision functional magnetic resonance imaging (fMRI) (Menon et al., 1997; Dechent and Frahm 2000; Cheng et al., 2001; Yacoub et al., 2007). Although gradient-echo (GE) echo-planar imaging (EPI) is often used at lower field strengths, the applicability for high-resolution fMRI at higher field strengths is still under debate because of its inherent sensitivity to large draining veins (Polimeni et al., 2010). To counteract the loss of specificity, it was recently suggested to only sample far away from the pial surface when using GE-EPI (Nasr et al., 2016; Polimeni et al., 2017). Here, we assessed whether differential ocular dominance responses can be resolved using GE-EPI with different isotropic resolutions (0.8 mm and 1.0 mm) and how the corresponding BOLD signal is distributed across the cortex

High resolution quantitative and functional MRI indicate lower myelination of thin and thick stripes in human secondary visual cortex

The characterization of cortical myelination is essential for the study of structure-function relationships in the human brain. However, knowledge about cortical myelination is largely based on post mortem histology, which generally renders direct comparison to function impossible. The repeating pattern of pale-thin-pale-thick stripes of cytochrome oxidase (CO) activity in the primate secondary visual cortex (V2) is a prominent columnar system which is known to be differentiable by myelin content as well. However, depending on the applied histological method, higher myelination in both thin/thick and pale stripes were found, respectively. We used quantitative magnetic resonance imaging (qMRI) in conjunction with functional magnetic resonance imaging (fMRI) at ultra-high field strength (7T) to localize and study myelination of stripes in several humans at sub-millimeter resolution in vivo. Thin and thick stripes were functionally localized by exploiting their sensitivity to color and binocular disparity, respectively. Resulting functional activation maps showed robust stripe patterns in V2 which enabled further comparison of quantitative relaxation parameters between stripe types. Thereby, we found lower longitudinal relaxation rates (R1) of thin and thick stripes compared to surrounding gray matter in the order of 1-2%, indicating higher myelination of pale stripes. No differences for effective transverse relaxation rates (R2*) were found. The study demonstrates the feasibility to investigate structure-function relationships in living humans within one cortical area at the level of columnar systems using qMRI

Formation and stability of self-assembled coherent islands in highly mismatched heteroepitaxy

We study the energetics of island formation in Stranski-Krastanow growth within a parameter-free approach. It is shown that an optimum island size exists for a given coverage and island density if changes in the wetting layer morphology after the 3D transition are properly taken into account. Our approach reproduces well the experimental island size dependence on coverage, and indicates that the critical layer thickness depends on growth conditions. The present study provides a new explanation for the (frequently found) rather narrow size distribution of self-assembled coherent islands.Comment: 4 pages, 5 figures, In print, Phys. Rev. Lett. Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Knowledge of emergency management of avulsed teeth among Italian dentists-questionnaire study and next future perspectives

(1) Background: In Italy, about one fourth of all schoolchildren experience a trauma to the permanent dentition. Management of avulsion trauma is challenging and requires adherence to clinical protocols. The aim of this study was to investigate the management knowledge of avulsed teeth among Italian dentists and to promote the guidelines’ dissemination through the use of new social media. (2) Methods: The survey was carried out during the COVID-19 lockdown in Italy (March–May 2020). The questionnaire was sent anonymously to a total of 600 dentists. The questionnaire consisted of two parts. Part A—demographic and professional data and Part B—management of traumatic avulsion. (3) Results: The response rate was 50.6% and the mean fraction of correct responses was 0.524. Issues related to the therapeutic management of avulsed teeth were shown to be not well understood by the respondents. Professionals with qualifications in dentistry and those who declared to know the guidelines responded better, while other demographic and professional factors were insignificant. (4) Conclusions: Italian dentists’ knowledge of the management of avulsion trauma should be improved. Educational programs and campaigns must be undertaken to improve their awareness and adherence to the Italian and international guidelines

Self-assembly of quantum dots: effect of neighbor islands on the wetting in coherent Stranski-Krastanov growth

The wetting of the homogeneously strained wetting layer by dislocation-free three-dimensional islands belonging to an array has been studied. The array has been simulated as a chain of islands in 1+1 dimensions. It is found that the wetting depends on the density of the array, the size distribution and the shape of the neighbor islands. Implications for the self-assembly of quantum dots grown in the coherent Stranski-Krastanov mode are discussed.Comment: 4 pages, 6 figures, accepted version, minor change

Single and vertically coupled type II quantum dots in a perpendicular magnetic field: exciton groundstate properties

The properties of an exciton in a type II quantum dot are studied under the influence of a perpendicular applied magnetic field. The dot is modelled by a quantum disk with radius $R$, thickness $d$ and the electron is confined in the disk, whereas the hole is located in the barrier. The exciton energy and wavefunctions are calculated using a Hartree-Fock mesh method. We distinguish two different regimes, namely $d<<2R$ (the hole is located at the radial boundary of the disk) and $d>>2R$ (the hole is located above and below the disk), for which angular momentum $(l)$ transitions are predicted with increasing magnetic field. We also considered a system of two vertically coupled dots where now an extra parameter is introduced, namely the interdot distance $d_{z}$. For each $l_{h}$ and for a sufficient large magnetic field, the ground state becomes spontaneous symmetry broken in which the electron and the hole move towards one of the dots. This transition is induced by the Coulomb interaction and leads to a magnetic field induced dipole moment. No such symmetry broken ground states are found for a single dot (and for three vertically coupled symmetric quantum disks). For a system of two vertically coupled truncated cones, which is asymmetric from the start, we still find angular momentum transitions. For a symmetric system of three vertically coupled quantum disks, the system resembles for small $d_{z}$ the pillar-like regime of a single dot, where the hole tends to stay at the radial boundary, which induces angular momentum transitions with increasing magnetic field. For larger $d_{z}$ the hole can sit between the disks and the $l_{h}=0$ state remains the groundstate for the whole $B$-region.Comment: 11 pages, 16 figure