Etude de la fonction cardiaque 4D à partir de ciné cardiaque 3D via une synchronisation sur la respiration et rythme cardiaque: travail de Bachelor

Objectifs : Dans le cadre de l’exploration cardiaque en IRM, nous expérimentons une séquence 4D à partir d’une séquence 4D Flow. L’objectif est de calculer la fraction d’éjection et de la comparer avec la séquence 2D ciné (gold standard actuel) utilisée cliniquement. Grâce à des outils statistiques, nous évaluons la reproductibilité intra- et inter-opérateurs de la séquence 4D. Nous regardons également la précision de cette séquence en comparant les résultats des segmentations 4D aux segmentations de la séquence 2D ciné. Méthodologie : Dans un premier temps, nous avons optimisé la séquence 4D en modifiant certains paramètres comme la vitesse d’encodage retenue à 30cm/s et le tracking factor (tf) de 0.6 × mouvement mesuré (au niveau du diaphragme). Les séquences ont été réalisées, à quatre temps différents, sur trois individus sains. Dans un second temps, nous avons calculé la fraction d’éjection du ventricule gauche (FEVG) en le segmentant en diastole et en systole selon la méthode Simpson. Cela a été fait sur la séquence 4D et sur la 2D ciné, deux fois, afin d’obtenir des données plus conséquentes pour mesurer la corrélation entre les deux techniques et la variabilité entre chaque opérateur. Enfin, chaque valeur obtenue est introduite dans un tableau Excel, puis convertie sous forme d’équation ICC et Bland-Altman. A partir de ça, nous calculons la variabilité intra- et inter-opérateur, ce qui nous permet de visualiser la concordance de nos résultats et de comparer les valeurs obtenues pour le 4D avec celles obtenues pour le 2D ciné. Résultats : Les calculs ICC donnent des valeurs entre 0.71 et 0.96 pour les différents temps d'acquisitions. Ces données traduisent de bonnes corrélation et reproductibilité intra-opérateur, par rapport à ce que dit la littérature (> 0.75). Quant à la variabilité inter-opérateur, elle est, dans l'ensemble, en dessous de la valeur de référence (< 0.4) synonyme d'une faible corrélation entre opérateur. Suite à ces résultats peu encourageants, nous voulions trouver la source d’erreur. En étudiant les volumes systoliques et diastoliques séparément (et non la FEVG), nous constatons un résultat élevé en diastole (0.78), mais en dessous de nos moyennes en systole (0.4). Conclusion : Suite à l'analyse de nos résultats, nous constatons que le travail de segmentation de chacun d'entre nous subit une amélioration avec le temps et nous permet de diminuer la variabilité entre 2D ciné et 4D. La reproductibilité est observée en intra- mais est à réévaluer de façon plus approfondie en inter-opérateur

J/ψJ/\psi normal and anomalous suppressions in a hadron and string cascade model

A mechanism for the effective dissociation of a $c\bar{c}$ pair in the colour electric field of strings is introduced into a hadron and string cascade model, i.e. JPCIAE, which is based on the LUND model, simulating ultra-relativistic nucleus - nucleus collisions. This new mechanism together with the known mechanism of nuclear absorption (both baryons and mesons) could reproduce fairly the data of the normal and anomalous $J/\psi$ suppressions in minimum bias pA, AB (with light projectile), and Pb + Pb collisions at 200 A GeV/c. However the impact parameter (E_T) dependence of the $J/\psi$ suppression factor, both, in S + U and Pb + Pb reactions at 200 A GeV/c and 158 A GeV/c, respectively, is not well reproduced. We also tested the additional mechanism of the energy degradation of leading particles, with which both, the normal and anomalous $J/\psi$ suppressions in minimum bias pA, AB, and Pb + Pb collisions and the E_T dependence of the $J/\psi$ suppression factor are better reproduced.Comment: 16 pages (RevTex), 6 ps-figures, to be published in J. Phys.

Gyrate atrophy of the choroid and retina with hyper-ornithinemia responsive to vitamin B6: a case report

<p>Abstract</p> <p>Background</p> <p>Gyrate atrophy of the retina and choroid is a rare autosomal recessive inherited disease, characterized by progressive chorioretinal atrophy that results in progressive deterioration of peripheral and night vision and leading to blindness.</p> <p>Case presentation</p> <p>This report presents a case of a 28-year-old man consulting for a progressive fall of visual acuity with hemeralopia. Eye fundoscopy showed regions of confluent rounded chorioretinal atrophy. The visual field and retinal angiography were altered. A high level of plasma ornithine (629 nmol/mL) was detected and a diagnosis of gyrate atrophy of the retina and choroid was made. The patient was treated with high dose Pyridoxine supplement (300 mg/d for 6 months) and the ornithine level of his serum was successfully reduced.</p> <p>Conclusion</p> <p>The exact mechanism of chorioretinal atrophy in hyper-ornithinemia is not known and a small percentage of the affected people respond to Vitamin B6 supplementation.</p

Mid-infrared plasmons in scaled graphene nanostructures

Plasmonics takes advantage of the collective response of electrons to electromagnetic waves, enabling dramatic scaling of optical devices beyond the diffraction limit. Here, we demonstrate the mid-infrared (4 to 15 microns) plasmons in deeply scaled graphene nanostructures down to 50 nm, more than 100 times smaller than the on-resonance light wavelength in free space. We reveal, for the first time, the crucial damping channels of graphene plasmons via its intrinsic optical phonons and scattering from the edges. A plasmon lifetime of 20 femto-seconds and smaller is observed, when damping through the emission of an optical phonon is allowed. Furthermore, the surface polar phonons in SiO2 substrate underneath the graphene nanostructures lead to a significantly modified plasmon dispersion and damping, in contrast to a non-polar diamond-like-carbon (DLC) substrate. Much reduced damping is realized when the plasmon resonance frequencies are close to the polar phonon frequencies. Our study paves the way for applications of graphene in plasmonic waveguides, modulators and detectors in an unprecedentedly broad wavelength range from sub-terahertz to mid-infrared.Comment: submitte

Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10 998 vegetarians and non-vegetarians in the United Kingdom

In a cohort of 10998 men and women, 95 incident cases of colorectal cancer were recorded after 17 years. Risk increased in association with smoking, alcohol, and white bread consumption, and decreased with frequent consumption of fruit. The relative risk in vegetarians compared with nonvegetarians was 0.85 (95% CI: 0.55-1.32)

Appendiceal Mucocele in an Elderly Patient: How Much Surgery?

Appendiceal mucoceles are rare cystic lesions with an incidence of 0.3–0.7% of all appendectomies. They are divided into four subgroups according to their histology. Even though the symptoms may vary – depending on the level of complication – from right lower quadrant pain, signs of intussusception, gastrointestinal bleeding to an acute abdomen with sepsis, most mucoceles are asymptomatic and found incidentally. We present the case of a 70-year-old patient with an incidentally found appendiceal mucocele. He was seen at the hospital for backache. The CT scan showed a vertebral fracture and a 7-cm appendiceal mass. A preoperative colonoscopy displayed several synchronous adenomas in the transverse and left colon with high-grade dysplasia. In order to lower the cancer risk of this patient, we performed a subtotal colectomy. The appendiceal mass showed no histopathological evidence of malignancy and no sign of perforation. The follow-up was therefore limited to 2 months. In this case, appendectomy would have been sufficient to treat the mucocele alone. The synchronous high-grade dysplastic adenomas were detected in the preoperative colonoscopy and determined the therapeutic approach. Generally, in the presence of positive lymph nodes, a right colectomy is the treatment of choice. In the histological presence of mucinous peritoneal carcinomatosis, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy is indicated. In conclusion, mucoceles of the appendix are detected with high sensitivity by CT scan. If there is no evidence of synchronous tumor preoperatively and no peritoneal spillage, invasion or positive sentinel lymph nodes during surgery, a mucocele is adequately treated by appendectomy