BackgroundT1 mapping and extracellular volume (ECV) have the potential to guide patient care and serve as surrogate end-points in clinical trials, but measurements differ between cardiovascular magnetic resonance (CMR) scanners and pulse sequences. To help deliver T1 mapping to global clinical care, we developed a phantom-based quality assurance (QA) system for verification of measurement stability over time at individual sites, with further aims of generalization of results across sites, vendor systems, software versions and imaging sequences. We thus created T1MES: The T1 Mapping and ECV Standardization Program.MethodsA design collaboration consisting of a specialist MRI small-medium enterprise, clinicians, physicists and national metrology institutes was formed. A phantom was designed covering clinically relevant ranges of T1 and T2 in blood and myocardium, pre and post-contrast, for 1.5 T and 3 T. Reproducible mass manufacture was established. The device received regulatory clearance by the Food and Drug Administration (FDA) and Conformité Européene (CE) marking.ResultsThe T1MES phantom is an agarose gel-based phantom using nickel chloride as the paramagnetic relaxation modifier. It was reproducibly specified and mass-produced with a rigorously repeatable process. Each phantom contains nine differently-doped agarose gel tubes embedded in a gel/beads matrix. Phantoms were free of air bubbles and susceptibility artifacts at both field strengths and T1 maps were free from off-resonance artifacts. The incorporation of high-density polyethylene beads in the main gel fill was effective at flattening the B1 field. T1 and T2 values measured in T1MES showed coefficients of variation of 1 % or less between repeat scans indicating good short-term reproducibility. Temperature dependency experiments confirmed that over the range 15–30 °C the short-T1 tubes were more stable with temperature than the long-T1 tubes. A batch of 69 phantoms was mass-produced with random sampling of ten of these showing coefficients of variations for T1 of 0.64 ± 0.45 % and 0.49 ± 0.34 % at 1.5 T and 3 T respectively.ConclusionThe T1MES program has developed a T1 mapping phantom to CE/FDA manufacturing standards. An initial 69 phantoms with a multi-vendor user manual are now being scanned fortnightly in centers worldwide. Future results will explore T1 mapping sequences, platform performance, stability and the potential for standardization.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-016-0280-z) contains supplementary material, which is available to authorized users.

assisted with recruitment and testing of the participants, technical assistance, and coordination of the imaging project in the ALSPAC.

Novelty-seeking tendencies in adolescents may promote innovation as well as problematic impulsive behaviour, including drug abuse. Previous research has not clarified whether neural hyper- or hypo-responsiveness to anticipated rewards promotes vulnerability in these individuals. Here we use a longitudinal design to track 144 novelty-seeking adolescents at age 14 and 16 to determine whether neural activity in response to anticipated rewards predicts problematic drug use. We find that diminished BOLD activity in mesolimbic (ventral striatal and midbrain) and prefrontal cortical (dorsolateral prefrontal cortex) regions during reward anticipation at age 14 predicts problematic drug use at age 16. Lower psychometric conscientiousness and steeper discounting of future rewards at age 14 also predicts problematic drug use at age 16, but the neural responses independently predict more variance than psychometric measures. Together, these findings suggest that diminished neural responses to anticipated rewards in novelty-seeking adolescents may increase vulnerability to future problematic drug use.

Highly polarizable metastable He* (2 3 S) and Ne* (2 3 P) atoms have been diffracted from a 100 nm period silicon nitride transmission grating and the van der Waals coefficients C3 for the interaction of the excited atoms with the silicon nitride surface have been determined from the diffraction intensities out to the 10th order. The results agree with calculations based on the non-retarded Lifshitz formula.PACS numbers: 34.50.Dy, 03.75.BeThe van der Waals (vdW) force between atoms, molecules and solid surfaces is of far reaching importance in many branches of physics, chemistry, and biology [1]. For larger distances, retardation due to the exchange of virtual photons has to be included, while for distances much smaller than the smallest wavelength a non-retarded approach can be used. The theoretical foundations for atom-surface interactions were laid in the pioneering work of Lifshitz [2]. In this case the non-retarded vdW potential has the form −C 3 /l 3 in leading order, where l is the atom-surface separation and C 3 depends on the atom, its electronic state, and on the electronic states of the solid.For groundstate rare gas atoms the C 3 coefficients have recently been measured with good accuracy [3]. Less is known about the van der Waals interactions of electronically excited metastable and Rydberg atoms, in particular the C 3 coefficient is not accurately known. Some time ago, transmission through narrow channels [4] and level shifts in closed or semi-infinite cavities [5,6] have been studied. Recently, inelastic electronic transitions on passage over a metal edge [7] and reflection from surfaces and (reflection) gratings [8] have been measured. Currently there is great interest in these potentials, in particular for metastable helium which is widely used in atom optics [9] as well as in surface physics [10] and for which Bose-Einstein condensation has recently been achieved [11]. The atom-surface van der Waals potentials could soon become relevant in guiding slow metastable rare gas atoms along microstructures [12] or in studying collective effects of Bose-Einstein condensed metastable He* atoms in contact with a surface.From a theoretical point of view atoms in excited states are of particular interest. Their polarizability α is expected to increase as n 7 , with correspondingly much stronger interactions [13]. Therefore it is not obvious whether approximate formulae for the groundstate atom-surface vdW potential are still applicable for excited atoms. Moreover, with the much stronger vdW interaction new effects such as higher multipole coefficients [14] can be expected.In this article, an effective but simple experimental method is used to determine the atom-surface vdW coefficient C 3 for metastable rare gas atoms. It is based on diffraction of an atomic beam from a nanostructured transmission grating with a period of only 100 nm. Modifications in the hierarchy of the intensities of the higher order maxima in the diffraction pattern have been shown to be directly related to the strength C 3 of the atom...

Large-scale magnetic resonance (MR) studies of the human brain offer unique opportunities for identifying genetic and environmental factors shaping the human brain. Here, we describe a dataset collected in the context of a multi-centre study of the adolescent brain, namely the IMAGEN Study. We focus on one of the functional paradigms included in the project to probe the brain network underlying processing of ambiguous and angry faces. Using functional MR (fMRI) data collected in 1,110 adolescents, we constructed probabilistic maps of the neural network engaged consistently while viewing the ambiguous or angry faces; 21 brain regions responding to faces with high probability were identified. We were also able to address several methodological issues, including the minimal sample size yielding a stable location of a test region, namely the fusiform face area (FFA), as well as the effect of acquisition site (eight sites) and scanner (four manufacturers) on the location and magnitude of the fMRI response to faces in the FFA. Finally, we provided a comparison between male and female adolescents in terms of the effect sizes of sex differences in brain response to the ambiguous and angry faces in the 21 regions of interest. Overall, we found a stronger neural response to the ambiguous faces in several cortical regions, including the fusiform face area, in female (vs. male) adolescents, and a slightly stronger response to the angry faces in the amygdala of male (vs. female) adolescents.