We recently reported the successful use of the early-negative BOLD fMRI signal to map orientation columns in the cat visual cortex. However, the early-negative BOLD response can not be readily used for routine mapping of brain functions because of its low signal-to-noise combined with the need for high spatio-temporal resolution. In this study, we evaluated the feasibility of using perfusion-based fMRI to resolve columnar layouts in the same cat model and compared its spatial specificity with that of the conventional BOLD. The MRI perfusion-based signal is devoid of large draining venous vessels and is derived from a single physiological parameter without the convoluted susceptibility effect present in the BOLD signal. We hypothesized that perfusion-based fMRI is better suited to resolve columnar layouts as it is more spatially localized relative to the conventional BOLD signal. Perfusion-based and BOLD fMRI were performed on 6 cats. The visual stimulus consisted of drifting gratings of 4 orientations (ide...

Speculations about the role of free radicals generated in biological systems (so called bioradicals) are commonplace in many recent publications dealing with oxidative stress, inflammation and hypoxia reperfusion. Electron Paramagnetic Resonance Imaging (EPRI) technique has been developed to obtain the spatial distribution of the paramagnetic materials, particularly on a microscopic scale. A large number of biological studies were successfully carried out, especially for the visualization of bioradicals generated in vivo system. Typical example is the detection and visualization of nitric oxide (NO) in septic-shocked animals. The strength of EPRI is that only free radicals are visible in its image. On the contrary, weakness of EPRI is that nothing can be visible except paramagnetic materials on its image. Therefore, it seems imposible to predict in which organs the bioradicals were generated most from the results with EPRI. In order to overcome this problem, in this study, we have started developing EPR/MR...

Albinism causes foveal hypoplasia and an abnormally large number of fibres from temporal retina to cross the chiasmatic midline. Previous MRI work (Schmitz et al 2003 IOVS, 44 16-21) has indicated that the dimensions of the optic chiasm are abnormal in human subjects with albinism. The same subjects also showed a narrowing of the optic nerves and tracts and an increased angle between the nerves and tracts. Thus, abnormal crossing of visual fibres and reduced foveal cell numbers appear to have an effect on the gross anatomy of the optic chiasm. We have made a series of anatomical measurements of the optic chiasm, optic nerves and tracts based on T1-weighted (1x0.98x0.98mm) structural MRI scans of 20 control subjects (mean age, 34±11) and 19 subjects with albinism (mean age, 33±11). Similar to the previous study, we found that the dimensions of the chiasm were different for the two groups (albino width=9.3±1.0mm, control width=11.5±1.9mm , albino height=3.7±0.9mm, control height=3.4±0.7mm), but this only rea...

The corpus callosum (CC) is the principal white matter fiber bundle connecting neocortical areas of the two hemispheres. Although an object of extensive research, important details about the anatomical and functional organization of the human CC are still largely unknown. Here we focused on the callosal motor fibers (CMFs) that connect the primary motor cortices (M1) of the two hemispheres. Topography and somatotopy of CMFs were explored by using a combined functional magnetic resonance imaging/diffusion tensor imaging fiber-tracking procedure. CMF microstructure was assessed by fractional anisotropy (FA), and CMF functional connectivity between the hand areas of M1 was measured by interhemispheric inhibition using paired-pulse transcranial magnetic stimulation. CMFs mapped onto the posterior body and isthmus of the CC, with hand CMFs running significantly more anteriorly and ventrally than foot CMFs. FA of the hand CMFs but not FA of the foot CMFs correlated linearly with interhemispheric inhibition betwe...

Introduction Acute lymphocytic leukemia (ALL) is the most common form of childhood cancer. Advances in modern medicine have allowed a survival rate of up to 90%. However, children are often left with late effects, which impair cognitive ability, cause c...

Introduction: The beneficial effects of intravenous human umbilical cord blood cells (HUCBC) administration after stroke have recently been demonstrated in rodents. In addition, there is evidence for an extended time window for this experimental treatme...

Deep brain stimulation (DBS) is used increasingly in the field of movement disorders. The implanted electrodes create not only a priori risk to patient safety during MR imaging, but also a unique opportunity in the collection of functional MRI (fMRI) data conditioned by direct neural stimulation. We performed safety tests of commercially available bilateral neurostimulation systems (Soletra® 7482, Medtronic), extensions, and leads in a clinical 1.5 T MR system (Siemens, Germany) across a range of MR acquisitions of typical and worst case scenarios. The primary safety risk arises from RF induction of current through the electrode leads. It depends on the RF energy deposited during specific imaging sequences, on physical properties of the electrodes, and on the low impedance and/or resonant paths within the lead geometry. In vitro testing was performed using a phantom filled with a semisolid gel simulating the thermal convection and dielectric properties of human tissues. Each DBS electrode was positioned wi...

Comparisons of alterations in the anatomy of the entorhinal cortex (EC) and hippocampal formation (HF) in elderly individuals are of great interest, since these regions are pathologically involved in the very early stages of Alzheimer's disease (AD) and could, potentially, identify those at risk for developing AD. In the present study, 27 patients diagnosed with mild cognitive impairment (MCI-memory) received a high-resolution MRI scan at baseline and were followed with yearly clinical evaluations. Ten of the 27 converted to AD during a 36 month-period following the baseline clinical evaluation. EC and HF volumes were derived separately for each hemisphere from T1-weighted coronal images reformatted to be perpendicular to the long axis of the HF. To control for individual differences in brain size, regions of interest were divided by total intracranial volume (normalized). Logistic regression models showed that although both normalized entorhinal and hippocampal volumes were independent predictors of conve...

Language function was studied in 17 patients with infarctions apparently confined to unilateral basal ganglia and surrounding white matter [10 left hemisphere (LH), 7 right hemisphere (RH)]. Mean age at injury was 7yrs and 4yrs, and mean age at study was 12yrs and 9yrs, for the LH and RH groups respectively. We have previously shown that long-term receptive and expressive language outcome did not differ significantly between the LH and RH groups. The variance in the LH group was, however, much greater than in the RH group. Voxel-based morphometric analyses of structural MRI 3D datasets and MR diffusion tensor imaging data identified regions of grey and white matter density and diffusion anisotropy, outside the site of the infarction and including Broca’s area, that correlated with language performance in the LH group but not in the RH group. Furthermore, the only 3 patients with haemodynamic abnormalities involving left cortical language areas on MR perfusion imaging were the 3 LH patients with poorest lan...

OBJECTIVE: During EEG acquisition inside a magnet the generation of induced currents causes several technical and human safety issues. We designed an MRI compatible high resistive-lead EEG cap (InkCap) to reduce Specific Absorption Rate (SAR), improve EEG signal, preserve MRI image quality and enhance subject’s convenience. METHODS: The InkCap consists of 3 flexible circuit boards with conductive ink microstrips of 2 kΩ/m resistivity. The sensors have half-rings shape to reduce Eddy currents. Evaluation: 1) SAR simulations were performed on a high-resolution human head model for a wide range of microstip resistivity. 2) Temperature measurements on a human head-shaped agarose gel phantom were conducted with Luxtron equipment. High power TSE sequences at 7T were used comparing the InkCap with standard electrodes. 3) EEG acquisition was performed using a custom-made MRI-compatible EEG system with piezoelectric motion sensors. 4) MR imaging was done at 7T. RESULTS: Simulated SAR values and temperature increase...