Implementation of Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy (HERMES) for quantification of ɣ-aminobutyric acid (GABA) and glutathione (GSH)

The present study aimed to accelerate and improve accuracy of ɣ-aminobutyric acid (GABA) and glutathione (GSH) quantification. These metabolites, present at low concentrations in the brain, are challenging to detect using MR spectroscopy due to the fact that their resonance frequencies overlap with those of other more abundant metabolites. The advanced spectral editing techniques involving J-difference editing that are required to resolve the overlapping signals of these low concentration metabolites are not routinely available on clinical MRI scanners. In this work we implemented on a 3T Siemens Skyra MRI a novel MRS technique called Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy (HERMES) to simultaneously detect GABA and GSH, developed a novel postprocessing technique that simultaneously models the sum and various difference spectra, and evaluated the performance of the sequence and processing method both in phantoms and in vivo. HERMES was implemented by modifying the Siemens GABA-edited MEGA-PRESS WIP sequence to include two additional sub-experiments – one editing GSH with a single lobe pulse and one editing both GABA and GSH using a dual lobe pulse, and replacing the Siemens pulses with ‘universal' pulses similar to those used in a previous implementation of HERMES on a Philips platform. Performance was assessed in a phantom and 22 healthy adults, 15 of whom provided usable data (7 male, mean age 25.6 ± 2.7 yr). Three of the subjects were scanned 3 times to assess reproducibility. Data were processed and compared using a set of custom scripts in MATLAB. Following frequency and phase correction of individual averages with GANNET, we applied our custom simultaneous linear combination model that iteratively fit the concatenated sum and difference spectra using a least squares routine. SPM was used for tissue segmentation of structural images and FID-A to simulate high-resolution basis sets. The simultaneous modelling technique provided absolute quantification results for 15 metabolite moieties using internal unsuppressed water as a reference. The performance of the simultaneous fitting approach was compared to multiple independent fittings for HERCULES (Hadamard Editing Resolves Chemicals Using Linear-combination Estimation of Spectra) data that had been previously acquired on a 3T Philips Achieva MRI. Although the HERMES sequence implemented on the Siemens platform as part of this project was able to successfully edit both GABA and GSH, and generate line shapes consistent with the work by Saleh et al. (2016), quantification accuracy was disappointing. In the phantom data, GSH and GABA concentrations were both roughly 50% of known levels. Since the actual concentrations in vivo were not known, we were not able to establish accuracy, but quantification agreement between the MEGA-PRESS and HERMES sequences was poor for most metabolites. Specifically, GABA levels were two to three times higher than expected values using both HERMES and GABA-edited MEGA-PRESS. Despite poor absolute agreement, concentrations from HERMES and MEGA-PRESS data were moderately correlated, and HERMES data showed lower coefficients of variation across subjects, suggesting that it may be more reliable. HERMES was also more reproducible across scanning sessions and participants for more metabolites than GABA- or GSH-edited MEGA-PRESS. Our findings also showed that simultaneous fitting using the sum and difference spectra produces lower coefficients of variation for most metabolites than fittings to sum and difference spectra separately

Fast Luminosity Monitoring using Diamond Sensors for Super Flavour Factories

MOPME004 - ISBN 978-3-95450-122-9International audienceSuper flavour factories aim to reach very high luminosities thanks to a new concept whereby the ultra-low emittance beams collide with a large crossing angle. Fast luminosity measurements are needed as input to luminosity optimization and feedback in the presence of dynamic imperfections. The required small relative precision can be reached exploiting the very large cross section of the radiative Bhabha process at zero photon scattering angle. The instrumental technique selected to sustain the large particle fluxes is based on diamond sensors to be positioned viamoveable stages immediately outside the beam pipe, at locations chosen to minimize the contamination from other particle loss mechanisms

Happy Land

[Verse]Happy land! happy land!Whate\u27er my fate in life may be,Still again! still again!My thought will cling to theeLand of love and sunny skies,Rich in joy and beauty;Still make affection duty, Oh! [Chorus]Happy land! happy land!Ne\u27er from thee my heart can stray,I would fain! hear again!Thy merry mountain lay;Li ri la la, li ri la la ,li ri la li ri la li ri la li ri la la,Li ri la la li ri la la,Thy merry Switzer\u27s mountain lay

Tests de photo-identification appliqués à la reconnaissance des cépages : résultats préliminaires. Rapport de la mission CPE - GRTM du 24 octobre 1972

L'étude de l'information apportée par les quatre types de photographies aériennes : photographies panchromatique, infra-rouge, couleur et fausse-couleur a été abordée en milieu viticole en vue de la différenciation et de l'identification des cépages. Pour ce faire, nous avons estimé les valeurs informatives des documents obtenus, puis nous avons essayé de préciser les améliorations technologiques et méthodologiques susceptibles d'augmenter l'efficacité du systèm

Study of incoherent pair generation in the beam-beam interaction simulation program Guinea-Pig

Talk given at 2005 ALCPG & ILC Workshops - Snowmass, U.S.A., Aug. 14-27, 2005. Pulbished in the proceedings : www.slac.stanford.edu/econf/C0508141/proc/papers/ALCPG0933.PDFInternational audienceThis paper deals with two topics: the generation of incoherent pairs in two-beam-beam simulation programs, Guinea-Pig and CAIN, and the influence of the ILC beam parameter choices on the background in the micro-vertex detector (VD) induced by direct hits. One of the processes involved in incoherent pair creation (IPC) is equivalent to a four fermions interaction and its cross section can be calculated exactly with a dedicaded generator, BDK. A comparison of Guinea-Pig and CAIN results with BDK allows to identify and quantify the uncertainties on IPC background predictoins and to benchmark the Guinea-Pig calculation. Based on this simulation and different VD designs, the five currently suggested ILC beam parameter sets have been compared regarding IPC background induced in the VD by direct IPC hits. We emphasize that the high luminosity set, as it is currently defined, would constrain both the choices of magnetic field and VD inner layer radius

Fast Luminosity Monitoring using Diamond Sensors for the Super Flavor Factory SuperKEKB

ISBN 978-3-95450-132-8 - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/thpme090.pdfInternational audienceSuper luminous flavor factories, as SuperKEKB in Japan, aim to achieve very high luminosity thanks to a newly employed concept, the nano-beam scheme, where ultra-low emittance beams collide at very large crossing angle. Luminosity optimisation and dynamic imperfections require fast luminosity measurements. The aimed precision, 10−3 in 10 ms, can be achieved thanks to the very large cross-section of the radiative Bhabha process at zero-photon scattering angle. As a result of huge particle fluxes, diamond sensors are chosen to be placed just outside the beam-pipe, downstream of the interaction point, at locations with event rates consistent with the aimed precision and small enough contamination by backgrounds from single-beam particle losses. We will present the results concerning the investigation of the optimal positioning of our diamond sensors, taking into account the rate of Bhabha particles as well as their interactions with the beam pipe material

Les Scientifiques Marvel

Les histoires de super héros telles qu’elles sont relatées dans les films abondent de figures de scientifiques, profession qui n’est pas sans rapport avec leur metamorphose prochaines : leurs capacités (super pouvoirs), destins, quêtes leur sont souvent confiés par la science. Il est à noter cependant que si ces personnages utilisent leurs pouvoirs pouer effectuer des actes plus ou moins louables, ils ne sont pas les seuls à qui le succès doit revenir pleinement, ainsi des personnages secondaires sont tout aussi présents et aident les personnages principaux dans ce qu’ils doivent accomplir. Si les premiers sont vêtus de costumes reconnaissables et uniques, les seconds ne sont pas en reste ; il est difficile de ne pas voir ce que recouvre ces personnages secondaires en tant que porteurs de significations dans le paysage scientifique et leur place dans l’histoire. C’est en analysant les personnages et leurs costumes que nous tenterons d’en dégager les propriétés dans les films

Home, Sweet Home

Illustration of a cabin and a tree on the bank of a river.https://scholarsjunction.msstate.edu/cht-sheet-music/1455/thumbnail.jp