Cine and tagged cardiovascular magnetic resonance imaging in normal rat at 1.5 T: a rest and stress study

BACKGROUND: The purpose of this study was to measure regional contractile function in the normal rat using cardiac cine and tagged cardiovascular magnetic resonance (CMR) during incremental low doses of dobutamine and at rest. METHODS: Five rats were investigated for invasive left ventricle pressure measurements and five additional rats were imaged on a clinical 1.5 T MR system using a cine sequence (11-20 phases per cycle, 0.28/0.28/2 mm) and a C-SPAMM tag sequence (18-25 phases per cycle, 0.63/1.79/3 mm, tag spacing 1.25 mm). For each slice, wall thickening (WT) and circumferential strains (CS) were calculated at rest and at stress (2.5, 5 and 10 microg/min/kg of dobutamine). RESULTS: Good cine and tagged images were obtained in all the rats even at higher heart rate (300-440 bpm). Ejection fraction and left ventricular (LV) end-systolic volume showed significant changes after each dobutamine perfusion dose (p < 0.001). Tagged CMR had the capacity to resolve the CS transmural gradient and showed a significant increase of both WT and CS at stress compared to rest. Intra and interobserver study showed less variability for the tagged technique. In rats in which a LV catheter was placed, dobutamine produced a significant increase of heart rate, LV dP/dtmax and LV pressure significantly already at the lowest infusion dose. CONCLUSION: Robust cardiac cine and tagging CMR measurements can be obtained in the rat under incremental dobutamine stress using a clinical 1.5 T MR scanner

Myocardial perfusion assessment by use of system identification method in a one-compartment model

Cardiovascular magnetic resonance has been shown to provide high data quality for myocardial perfusion assessment. However, to analyze the perfusion data, some signal processing and modeling is needed to correct for motion related artifacts and limited spatial resolution. This study describes a method based on system identification, allowing, after a first step of image registration, to integrate and correct the partial volume effect in the myocardium perfusion quantification. This method is then applied to patients with coronary artery disease or hypertrophic obstructive cardiomyopathy

In vivo labelling of resting monocytes in the reticuloendothelial system with fluorescent iron oxide nanoparticles prior to injury reveals that they are mobilized to infarcted myocardium

Aims To evaluate the feasibility of loading resting monocytes/macrophages by intravenous (i.v.) injection of fluorescent iron oxide nanoparticles prior to injury and tracking of these cells in the very same animal to myocardial infarction (MI) by magnetic resonance imaging (MRI) and optical imaging. Methods and results Rats were injected with fluorescent iron oxide nanoparticles (10 mg/kg) (n = 15) prior to injury. After disappearance of the nanoparticles from the blood, MI was induced. Monocytes/macrophages were then tracked in the very same animal by MRI and optical imaging. Control groups were (i) non-injected animals (n = 15), (ii) injected animals associated with a sham operation (n = 8), and (iii) animals treated with an anti-inflammatory agent (n = 6). The presence of iron-loaded cells can be detected by MRI in vivo in the infarcted myocardium. Here, we showed that the detection of inflammatory cells in vivo correlated well with ex vivo imaging (MRI and reflectance fluorescence) and histology. We also showed that the method is robust enough to depict changes in the inflammatory response. Conclusion This study demonstrates that resting monocytes/macrophages can be loaded in vivo by a simple i.v. injection of fluorescent superparamagnetic iron oxide nanoparticles prior to injury and then tracked, in the same animal, in a model of ischaemia-reperfusion leading to myocardial infarct. Although previous studies of macrophages infiltration following MI have labelled the macrophages after injury, this study, for the first time, has pre-load the resting monocytes with fluorescent iron oxide nanoparticle

Analyse et optimisation de la perfusion et diffusion tissulaire en imagerie par résonance magnétique (IRM) périnatale et abdominale

Dans la pathologie cérébrale du prématuré, l'implémentation de séquences de diffusion en imagerie par résonance magnétique (IRM) à 1,5T a permis in vivo : une discrimination des zones saines et pathologiques dans des modèles hypoxiques et excitotoxiques de leucomalacie chez des souriceaux et ratons nouveaux-né (<10gr) ; la caractérisation de ramollissement inflammatoire et de l'évolution biphasique de leucomalacie kystique; une quantification in utero de la maturation cérébrale par le coefficient de diffusion apparent et la fraction d'anisotropie. L'étude de la perfusion hépatique par IRM a conduit à l'optimisation d'un protocole d'acquisition T1 avec injection d'un bolus de gadolinium, associé à une analyse compartimentale. L'application aux pathologies chroniques telles que la fibrose et la cirrhose montre une excellente discrimination sain-fibrose-cirrhose. Cette sensibilité IRM au degré d'atteinte parenchymateuse offre une nouvelle caractérisation non invasive de ces pathologies.ln newborn brain pathology, MR diffusion weighted sequences at 1,5T allowed in vivo : a discrimination between heathly and pathologic areas in hypoxic and excitotoxic models ofleucomalacia in newborn mouse and rat (<10gr) ; caracterisation of local inflammatory response and biphasic time course of cystic leucomalacia; in utero quantification of brain development with apparent diffusion coefficient and anisotropy fraction. MR quantification of hepatic perfusion parameters was described and validated with a optimized protocol consisting of a T1 dynamic sequence after intravenous bolus administration of gadolinium and a dual input one-compartmental model. Applied to chronic liver diseases, this technique allowed to differentiate healthy liver, fibrosis and cirrhosis with a good correlation between MR and hemodynamic data. Our results demonstrate a high sensitivity to degree of fibrosis and validate the use of dynamic MRI for the non invasive assessment of hepatic perfusion parameters.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Computing rotation centers of the heart from tagged MRI

Pages: 67-6

Les anciens pièges à poissons de l'archipel de Bréhat (Côtes d'Armor)

National audienceUn ancien mode de pêche, pratiquement tombé dans l'oubli, a laissé des traces sur les côtes de Bretagne. Il s'agit de pièges à poissons ou pêcheries. Un programme de recherche intitulé «Les Pêcheries d'estran de Bretagne» a été lancé en 2006 dans le cadre de l'A.M.A.R.A.I (Association Manche Atlantique pour la Recherche Archéologique dans les Îles) et du thème de recherche «Littoral» de l'Unité Mixte de Recherche (UMR 6566) «CReAAH» (Centre de Recherche en Archéologie, Archéosciences, Histoire). Actuellement, plus de 620 anciens pièges à poissons sur estran ont été repérés sur les côtes comprises entre le Mont-Saint-Michel et l'embouchure de la Loire