Reducing peripheral nerve stimulation due to gradient switching using an additional uniform field coil.

This study shows that larger rates of change of gradient with time (dG/dt) can be achieved at the threshold for peripheral nerve stimulation by applying a uniform concomitant field varying synchronously with a transverse field gradient and that this increase may be achieved without significant reduction of the spatial extent of the region over which imaging can be carried out. Realization of similar benefits through application of a uniform, z-directed field varying synchronously with an axial gradient is also demonstrated. The design and construction of transverse and axial coil arrangements is described, along with the results of volunteer studies that were carried out on 20 subjects, with the subjects positioned with four different regions (head, heart, hips, and knees) centered in the coils. These experiments were carried out at zero-field on a prototype system in which the coils were not actively shielded. The uniform concomitant field coil was not torque balanced. The increase in the rate of change of gradient at the threshold for peripheral nerve stimulation that could be achieved by the addition of the uniform field depends on body position and was larger for the transverse coils (head = × 1.9 ± 0.6; heart = × 0.9 ± 0.3; hips = × 1.4 ± 0.4; knees = × 1.5 ± 0.4) than for the axial coils (head = × 1.5 ± 0.6; heart = × 0.8 ± 0.3; hips = × 1.3 ± 0.4; knees = × 1.1 ± 0.3).

Hemodynamic Assessment in Bicuspid Aortic Valve Disease and Aortic Dilation: New Insights From Voxel-By-Voxel Analysis of Reverse Flow, Stasis, and Energetics.

Objectives: Clinical management decisions surrounding ascending aorta (AAo) dilation in bicuspid aortic valve (BAV) disease benefit from personalized predictive tools. 4D-flow MRI may provide patient-specific markers reflective of BAV-associated aortopathy. This study aims to explore novel 4D-flow MRI parametric voxel-by-voxel forward flow, reverse flow, kinetic energy and stasis in BAV disease. We hypothesize that novel parametric voxel-by-voxel markers will be associated with aortic dilation and referral for surgery and can enhance our understanding of BAV hemodynamics beyond standard metrics. Methods: A total of 96 subjects (73 BAV patients, 23 healthy controls) underwent MRI scan. Healthy controls had no known cardiovascular disease. Patients were clinically referred for AAo dilation assessment. Indexed diameters were obtained by dividing the aortic diameter by the patient's body surface area. Patients were followed for the occurrence of aortic surgery. 4D-flow analysis was performed by a single observer in five regions: left ventricular outflow tract (LVOT), AAo, arch, proximal descending aorta (PDAo), and distal descending aorta (DDAo). In each region peak velocity, kinetic energy (KE), forward flow (FF), reverse flow (RF), and stasis were measured on a voxel-by-voxel basis. T-tests (or non-parametric equivalent) compared flow parameters between cohorts. Univariate and multivariate analyses explored associations between diameter and parametric voxel-by-voxel parameters. Results: Compared to controls, BAV patients showed reduced stasis (p < 0.01) and increased RF and FF (p < 0.01) throughout the aorta, and KE remained similar. In the AAo, indexed diameter correlated with age (R = 0.326, p = 0.01), FF (R = -0.648, p < 0.001), RF (R = -0.441, p < 0.001), and stasis (R = -0.288, p < 0.05). In multivariate analysis, FF showed a significant inverse association with AAo indexed diameter, independent of age. During a median 179 ± 180 days of follow-up, 23 patients (32%) required aortic surgery. Compared to patients not requiring surgery, they showed increased KE and peak velocity in the proximal aorta (p < 0.01), accompanied by increased RF and reduced stasis throughout the entire aorta (p < 0.01). Conclusion: Novel voxel-by-voxel reverse flow and stasis were altered in BAV patients and are associated with aortic dilation and surgical treatment.

Different Food Odors Control Brain Connectivity in Impulsive Children.

BACKGROUND: Impulsivity is a complex multi-dimensional combination of behaviors which include: ineffective impulse control, premature decision-making and inability to delay gratification. OBJECTIVE: The aim of this work was to explore how food odor perception and its emotional value is affected in impulsive children. METHODS: Here we compared two cohorts of impulsive and control children with ages between 10 and 16 years. Both groups underwent a functional magnetic resonance imaging experiment, in which foodrelated odor-cues were presented to all of them. RESULTS: Differences in regions of blood oxygen level dependent activation, as well as connectivity, were calculated. Activations were significant for all odors in the impulsive group in the temporal lobe, cerebellum, supplementary motor area, frontal cortex, medial cingulate cortex, insula, precuneus, precentral, para-hippocampal and calcarine cortices. CONCLUSION: Connectivity results showed that the expected emotional reward, based on odor perceived and processed in temporal lobes, was the main cue driving responses of impulsive children. This was followed by self-consciousness, the sensation of interaction with the surroundings and feelings of comfort and happiness, modulated by the precuneus together with somatosensory cortex and cingulum. Furthermore, reduced connectivity to frontal areas as well as to other sensory integration areas (piriform cortex), combined to show different sensory processing strategies for olfactory emotional cues in impulsive children. Finally, we hypothesize that the cerebellum plays a pivotal role in modulating decision-making for impulsive children.

Strategies for tonal and atonal musical interpretation in blind and normally sighted children: an fMRI study.

INTRODUCTION: Early childhood is known to be a period when cortical plasticity phenomena are at a maximum. Music is a stimulus known to modulate these mechanisms. On the other hand, neurological impairments like blindness are also known to affect cortical plasticity. Here, we address how tonal and atonal musical stimuli are processed in control and blind young children. We aimed to understand the differences between the two groups when processing this physiological information. RESULTS: Atonal stimuli produced larger activations in cerebellum, fusiform, and temporal lobe structures than tonal. In contrast, tonal stimuli induced larger frontal lobe representations than atonal. Control participants presented large activations in cerebellum, fusiform, and temporal lobe. A correlation/connectivity study showed that the blind group incorporated larger amounts of perceptual information (somatosensory and motor) into tonal processing through the function of the anterior prefrontal cortex (APC). They also used the visual cortex in conjunction with the Wernicke's area to process this information. In contrast, controls processed sound with perceptual stimuli from auditory cortex structures (including Wernicke's area). In this case, information was processed through the dorsal posterior cingulate cortex and not the APC. The orbitofrontal cortex also played a key role for atonal interpretation in this group. DISCUSSION: Wernicke's area, known to be involved in speech, was heavily involved for both groups and all stimuli. The two groups presented clear differences in strategies for music processing, with very different recruitment of brain regions.

Magnetic Resonance Techniques Applied to the Diagnosis and Treatment of Parkinson's Disease.

Parkinson's disease (PD) affects at least 10 million people worldwide. It is a neurodegenerative disease, which is currently diagnosed by neurological examination. No neuroimaging investigation or blood biomarker is available to aid diagnosis and prognosis. Most effort toward diagnosis using magnetic resonance (MR) has been focused on the use of structural/anatomical neuroimaging and diffusion tensor imaging (DTI). However, deep brain stimulation, a current strategy for treating PD, is guided by MR imaging (MRI). For clinical prognosis, diagnosis, and follow-up investigations, blood oxygen level-dependent MRI, DTI, spectroscopy, and transcranial magnetic stimulation have been used. These techniques represent the state of the art in the last 5 years. Here, we focus on MR techniques for the diagnosis and treatment of Parkinson's disease.