Vincent Denolin

Structural asymmetries in motor and language networks in a population of healthy preterm neonates at term equivalent age: A diffusion tensor imaging and probabilistic tractography study

In this MRI study, we aimed to provide new in vivo structural markers of asymmetry in motor and language networks in a population of healthy preterm neonates scanned at term equivalent age. Using diffusion tensor imaging and probabilistic tractography, we showed that, besides volume and microstructural asymmetries in the parieto-temporal part of the superior longitudinal fasciculus (SLF) and a trend towards microstructural asymmetry in the corticospinal tract (CST), volume asymmetry in the motor part of the superior thalamic radiations (STR) and a trend towards volume asymmetry in the CST are already present in the neonatal period. No asymmetry was found in the sensory part of the STR, the anterior thalamic radiations (ATR), and posterior thalamic radiations (PTR) neither in the fronto-parietal part of the SLF. These results suggest that structural asymmetries in the motor and language networks are present in healthy preterm neonates at term equivalent age, well before the development of speech and hand preference.

Mapping of oxygen by imaging lipids relaxation enhancement: A potential sensitive endogenous MRI contrast to map variations in tissue oxygenation

Because of its paramagnetic properties, oxygen may act as an endogenous magnetic resonance imaging contrast agent by changing proton relaxation rates. Changes in tissue oxygen concentrations have been shown to produce changes in relaxation rate R1 of water. The aim of the study was to improve the sensitivity of oxygen enhanced R1 imaging by exploiting the higher solubility of oxygen in lipids (as compared with water) to sensitively monitor changes in tissue oxygen levels by selectively measuring the R1 of lipids.

Perfusion maps of the whole liver based on high temporal and spatial resolution contrast-enhanced MRI (4D THRIVE): Feasibility and initial results in focal liver lesions

PURPOSEnTo prospectively evaluate a new imaging sequence (4D THRIVE) for whole liver perfusion in high temporal and spatial resolution. Feasibility of parametric mapping and its potential for characterizing focal liver lesions (FLLs) are investigated.nnnMATERIALS AND METHODSnFifteen patients suspected for colorectal liver metastases (LMs) were included. Parametric maps were evaluated qualitatively (ring-enhancement and lesion heterogeneity) and compared to three-phased contrast-enhanced MRI. Quantitative analysis was based on average perfusion values of entire FLLs. Reference standard comprised surgery with histopathology or follow-up imaging. Fishers exact test was used for qualitative and Kruskal-Wallis test for quantitative analysis.nnnRESULTSnIn total 29 LMs, 17 hemangiomas and 4 focal nodular hyperplasias were evaluated. FLLs could be differentiated by qualitative assessment of parametric maps respectively three-phased contrast-enhanced MRI (Fishers p<0.001 for comparisons between LMs and hemangiomas and LMs and FNHs for both ring-enhancement and lesion heterogeneity) rather than by quantitative analysis of parametric maps (Chi-square for Kep=0.33 (p=0.847) and Chi-square for Kel=1.35 (p=0.509)).nnnCONCLUSIONnThis preliminary study shows potential of 4D THRIVE for whole liver imaging enabling calculation of parametric maps. Qualitative rather than quantitative analysis was accurate for differentiating malignant and benign FLLs.

Fat attenuation using a dual steady-state balanced-SSFP sequence with periodically variable flip angles.

A refocused‐SSFP sequence based on balanced‐FFE (TrueFisp, Fiesta) that attenuates fat signal is presented. The sequence uses periodically variable flip angles and produces a dual steady state of the signal, which is obtained after a dual transient phase if an appropriate preparation is used. The off‐resonance profile of the steady‐state signal exhibits large stopbands that can be employed for fat suppression. Numerical simulations were performed to investigate the signal behavior and the off‐resonance properties of the sequence. Experimental results obtained with a Philips Gyroscan Intera 1.5T MR scanner demonstrated fat attenuation in phantoms and abdominal images in volunteers. Magn Reson Med, 2006.

Clinical evaluation of automated scan prescription of knee MR images.

To compare an automated scan planning method to manual scan positioning in routine knee magnetic resonance imaging (MRI) studies.

Liver apparent diffusion coefficient repeatability with individually predetermined optimal cardiac timing and artifact elimination by signal filtering.

To prospectively assess liver ADC (apparent diffusion coefficient) repeatability from cardiac‐triggered diffusion‐weighted images obtained with an individually predetermined optimal cardiac time window minimizing cardiac‐related effects and to evaluate a signal filtering method aimed at artifact elimination.

Prescription automatisee des plans de coupe d’examens IRM du genou : premiere evaluation clinique

Objectifs La qualite du positionnement des sequences d’IRM depend de l’experience du technologue. Un interet croissant est porte aux programmes de positionnement automatique des coupes (PPAC). Cette etude compare la performance d’un PPAC a la methode traditionnelle de positionnement manuel des sequences d’examens IRM des genoux. Materiels et methodes Le software de PPAC est base sur la reconnaissance de structures anatomiques sur une sequence 3D T1, et est adaptatif, reposant sur l’« apprentissage » des plans souhaites lors d’examens du genou obtenus par positionnement manuel des coupes par un technologue experimente. Cinquante examens IRM du genou comportant trois sequences (coronal oblique, sagittal oblique, transverse) positionnees de facon automatisee ont ete compares a 50 examens IRM obtenus par positionnement manuel (groupe controle) : cotation qualitative « aveugle » par un radiologue experimente de chaque sequence en termes de couverture anatomique et angulation (score 0-3, U-test, Pxa0 Resultats Aucune difference qualitative significative (Pxa0>xa00,05) (couverture anatomique et angulation) n’est notee entre les sequences positionnees en mode manuel et automatique. Quatre sequences realisees « automatiquement » sont qualitativement « insuffisantes » (score 0-1) contre 13 sequences « manuelles ». Conclusion Le positionnement automatise des sequences d’IRM du genou est cliniquement realisable, de qualite equivalente a celle obtenue par positionnement manuel.