Influence of Motor Deficiency and Spatial Neglect on the Contralesional Posterior Parietal Cortex Functional and Structural Connectivity in Stroke Patients.

The posterior parietal cortex (PPC) is a key structure for visual attention and upper limb function, two features that could be impaired after stroke, and could be implied in their recovery. If it is well established that stroke is responsible for intra- and interhemispheric connectivity troubles, little is known about those existing for the contralesional PPC. In this study, we aimed at mapping the functional (using resting state fMRI) and structural (using diffusion tensor imagery) networks from 3 subparts of the PPC of the contralesional hemisphere (the anterior intraparietal sulcus), the posterior intraparietal sulcus and the superior parieto-occipital cortex to bilateral frontal areas and ipsilesional homologous PPC parts in 11 chronic stroke patients compared to 13 healthy controls. We also aimed at assessing the relationship between connectivity and the severity of visuospatial and motor deficiencies. We showed that interhemispheric functional and structural connectivity between PPCs was altered in stroke patients compared to controls, without any specificity among seeds. Alterations of parieto-frontal intra- and interhemispheric connectivity were less observed. Neglect severity was associated with several alterations in intra- and interhemispheric connectivity, whereas we did not find any behavioral/connectivity correlations for motor deficiency. The results of this exploratory study shed a new light on the influence of the contralesional PPC in post-stroke patients, they have to be confirmed and refined in further larger studies.

Determination of the lesion size in Laser-induced Interstitial Thermal Therapy (LITT) using a low-field MRI.

This study aimed to compare MR thermal mapping during Laser-induced Interstitial Thermal Therapy (LITT) to thermal lesions observed macroscopically, in order to estimate the 3D size of the coagulative necrosis. Laser irradiation was performed ex-vivo with a 980 nm laser in pig liver in a open low-magnetic field (0.2T) scanner. The laser light was transmitted through a 1040/600 microm (outer/core diameter) bare-tip silica fiber. The laser energy was applied on a pulsed mode (10 s laser-on, 10 s laser-off) for 12 minutes, power: 6W, energy: 2160 J. MR thermal mapping used T1 method for its simplicity and its efficiency at low magnetic field.