Bioenergetic basis for the increased fatigability with ageing.

Key Points: The mechanisms for the age-related increase in fatigability during dynamic exercise remain elusive. We tested whether age-related impairments in muscle oxidative capacity would result in a greater accumulation of fatigue causing metabolites, inorganic phosphate (P ), hydrogen (H ) and diprotonated phosphate (H PO ), in the muscle of old compared to young adults during a dynamic knee extension exercise. The age-related increase in fatigability (reduction in mechanical power) of the knee extensors was closely associated with a greater accumulation of metabolites within the working muscle but could not be explained by age-related differences in muscle oxidative capacity.

Understanding the importance of natural neuromotor strategy in upper extremity neuroprosthetic control.

A key challenge in upper extremity neuroprosthetics is variable levels of skill and inconsistent functional recovery. We examine the feasibility and benefits of using natural neuromotor strategies through the design and development of a proof-of-concept model for a feed-forward upper extremity neuroprosthetic controller. Developed using Artificial Neural Networks, the model is able to extract and classify neural correlates of movement intention from multiple brain regions that correspond to functional movements.

High-resolution reduced field of view diffusion tensor imaging using spatially selective RF pulses.

Purpose: Diffusion tensor imaging (DTI) plays a vital role in identifying white matter fiber bundles. Achievable imaging resolution and imaging time demands remain the major challenges in detecting small fiber bundles with current clinical DTI sequences.

Methods: A novel reduced field of view ultra-high-resolution DTI technique named eZOOM (elliptically refocused zonally oblique multislice) was developed.

Investigating the neural correlates of goal-oriented upper extremity movements.

Objective: To understand neural correlates of upper extremity task performance (functional vs. non-functional) and to understand their influence on neuromotor control strategies.

Design: Cross-sectional descriptive study, with repeated measures.

Understanding neuromotor strategy during functional upper extremity tasks using symbolic dynamics.

The ability to model and quantify brain activation patterns that pertain to natural neuromotor strategy of the upper extremities during functional task performance is critical to the development of therapeutic interventions such as neuroprosthetic devices. The mechanisms of information flow, activation sequence and patterns, and the interaction between anatomical regions of the brain that are specific to movement planning, intention and execution of voluntary upper extremity motor tasks were investigated here. This paper presents a novel method using symbolic dynamics (orbital decomposition) and nonlinear dynamic tools of entropy, self-organization and chaos to describe the underlying structure of activation shifts in regions of the brain that are involved with the cognitive aspects of functional upper extremity task performance.

Spatially quantifying microscopic tumor invasion and proliferation using a voxel-wise solution to a glioma growth model and serial diffusion MRI.

The purpose of this study was to develop a voxel-wise analytical solution to a glioma growth model using serial diffusion MRI. These cell invasion, motility, and proliferation level estimates (CIMPLE maps) provide quantitative estimates of microscopic tumor growth dynamics. After an analytical solution was found, noise simulations were performed to predict the effects that perturbations in apparent diffusion coefficient values and the time between apparent diffusion coefficient map acquisitions would have on the accuracy of CIMPLE maps.

Motor homunculus: passive mapping in healthy volunteers by using functional MR imaging--initial results.

Purpose: To determine the concurrence of activation in the primary motor cortex, induced by paradigms of active and passive movement of extremities, by using blood oxygen level-dependent functional magnetic resonance (MR) imaging.

Materials And Methods: The HIPAA-compliant study was approved by the institutional review board, and written informed consent was obtained from the participating volunteers. Functional MR imaging data were collected from 11 healthy volunteers (four women, seven men; age range, 24-42 years) during active and passive movements of hand, elbow, shoulder, ankle, knee, and hip.

Magnetic resonance spectroscopy.

The nuclear magnetic resonance phenomenon has given rise to both magnetic resonance imaging, which yields morphologic data, and magnetic resonance spectroscopy (MRS), which yields chemical data. In humans these data are derived principally from the resonances of the hydrogen nucleus in the low molecular weight compounds in the body. Hydrogen MRS has become a routinely used clinical tool in the brain, prostate, and breast.

MR-spectroscopic findings in juvenile-onset Huntington's disease.

Seven HD gene positive individuals under the age of 21 years are described with clinical examination and proton-MR-spectroscopy ((1)H-MRS) profiles of the putamen. Despite clinical variability, the predominate (1)H-MRS abnormality is elevated glutamate, expressed well beyond the confines of the basal ganglia, and low striatal creatine.

Morphology and morphometry in chronic spinal cord injury assessed using diffusion tensor imaging and fuzzy logic.

Diffusion tensor imaging (DTI) using a combination of direct anisotropy measurements provided a more anatomically accurate morphological representation of the human spinal cord than traditional anisotropy indices. Furthermore, the use of a fuzzy logic algorithm to segment regions of gray and white matter within the spinal cord based on these anisotropy measurements allowed for morphometric analyses. Results indicated a significant decrease in overall spinal cord cross-sectional area, dorsal funiculus cross-sectional area, and lateral funiculi cross-sectional area in subjects with injury compared to the neurologically intact control subjects.

Proton magnetic resonance spectroscopy of the hippocampus in patients with mild cognitive impairment: a pilot study.

Objective: To assess the brain metabolites in the hippocampus of patients with mild cognitive impairment (MCI) using proton magnetic resonance spectroscopy at 0.5 T.

Methods: Absolute concentrations and ratios to creatine of N-acetyl aspartate, myoinositol, glutamate + glutamine, and choline were measured in the right and left hippocampus of 5 MCI patients and 5 control subjects.

Opacification of the genitourinary collecting system during MDCT urography with enhanced CT digital radiography: nonsaline versus saline bolus.

Objective: The purpose of this study was to determine whether a saline bolus during CT urography improves urinary collecting system opacification and whether the addition of enhanced CT digital radiography (CTDR) improves urinary collecting system visualization with or without a saline bolus.

Materials And Methods: One hundred eight CT urography and enhanced CTDR examinations were reviewed. Fifty-four patients were given a saline bolus during CT urography, and 54 patients underwent CT urography without a saline bolus.

A volumetric analysis of soft-tissue changes in the aging midface using high-resolution MRI: implications for facial rejuvenation.

Background: The present study evaluated volumetric changes in the aging midface. Both young and old living subjects were studied using high-resolution magnetic resonance imaging (MRI) to investigate the distribution and volume of the muscle and subcutaneous components of the midface.

Methods: MRI with a customized radiofrequency coil was performed in 20 healthy Caucasian female volunteers equally divided between young (16 to 30 years) and old (>59 years) age groups.

Reduction of artifacts by optimization of the sensitivity map in sensitivity-encoded spectroscopic imaging.

Sensitivity-encoded spectroscopic imaging (SENSE-SI) reduces scanning time by using multiple coils for parallel signal acquisition. Significant artifacts could be induced by SENSE-SI, mainly due to the low-resolution nature of spectroscopic imaging. The present study introduces a novel method to reduce the artifacts.

Heterogeneity in 1H-MRS profiles of presymptomatic and early manifest Huntington's disease.

Objective: To evaluate (1)H-MRS profiles of the putamen in presymptomatic and manifest Huntington's disease (HD) patients for spectroscopic markers that are reliable, consistent signs of early pathology and to look for hemispheric differences as signs of use activation in an accelerated degradative process of the dominant hemisphere.

Methods: A short echo time Point RESolved Spectroscopy (PRESS) spectroscopic imaging study was performed at low field (0.5 Tesla, T) on 27 right-handed patients (17 presymptomatic gene carriers and 10 manifest patients of less than 3 years from clinical onset) and 10 right-handed normal volunteers.

The role of diffusion tensor imaging in establishing the proximity of tumor borders to functional brain systems: implications for preoperative risk assessments and postoperative outcomes.

Diffusion Tensor Imaging (DTI) is a new MRI imaging technique sensitive to directional movements of water molecules, induced by tissue barriers. This provides a new form of contrast that allows the identification of functional white matter tracts within the brain, and has been proposed as a technique suitable for presurgical planning in brain tumor patients. Resection of primary brain tumors improves survival, functional performance, and the effectiveness of adjuvant therapies, provided that surgically-induced neurological deficits can be avoided.

Lesion-induced pseudo-dominance at functional magnetic resonance imaging: implications for preoperative assessments.

Objective: To illustrate how lesion-induced neurovascular uncoupling at functional magnetic resonance imaging (fMRI) can mimic hemispheric dominance opposite the side of a lesion preoperatively.

Methods: We retrospectively reviewed preoperative fMRI mapping data from 50 patients with focal brain abnormalities to establish patterns of hemispheric dominance of language, speech, visual, or motor system functions. Abnormalities included gliomas (31 patients), arteriovenous malformations (AVMs) (11 patients), other congenital lesions (4 patients), encephalomalacia (3 patients), and tumefactive encephalitis (1 patient).

Effect of magnetic resonance imaging on internal magnet strength in Med-El Combi 40+ cochlear implants.

Objective: Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med-El Combi 40+ cochlear implant internal magnets after MRI studies.

Study Design/methods: Two fresh cadavers were used to study demagnetization using a repeated measures design and a magnetometer.

Visual object agnosia and pure word alexia: correlation of functional magnetic resonance imaging and lesion localization.

We present a case of a 64-year-old, right-handed female with a metastatic breast cancer lesion involving the left posterior inferior temporal lobe causing complete loss of the ability to recognize visually common objects and words. After her symptoms resolved on corticosteroid therapy, functional magnetic resonance imaging (fMRI) mapping demonstrated strong left-hemispheric dominance for word recognition and right-hemispheric dominance for object recognition. The case illustrates the relationships among ventral occipito-temporal cortical activation, lesion localization, and lesion-induced deficits of higher visual function.

Two-dimensional excitation short echo time chemical shift imaging at 0.5 tesla.

Detection of short T2 metabolites such as glutamate and glutamine (glx) in the brain can be improved by minimizing the echo time (TE) of the pulse sequence. By combining two dimensions of localization during a single radiofrequency (RF) pulse, an elliptic excitation chemical shift imaging sequence (EECSI) that further reduces TE by a factor of 2 relative to a TE-optimized point resolved spectroscopy sequence chemical shift imaging sequence was developed. An additional set of outer volume saturation pulses is included to minimize the contamination from scalp and marrow space lipids.

Intensity-dependent activation of the primary auditory cortex in functional magnetic resonance imaging.

Purpose: The purpose of this study was to investigate the activation patterns of the primary auditory cortex in response to varying intensities of pure tone stimuli.

Method: A 1,000-Hz pure tone stimulus was delivered monaurally to the right ear of 12 normal-hearing right-handed volunteers in 20-second on-off cycles. Stimuli were applied at 20 and 50 dB hearing level (HL) above threshold in 12 subjects and at 0, 20, 40, and 50 dB HL above threshold in 6 subjects.

Biophysics of cochlear implant/MRI interactions emphasizing bone biomechanical properties.

Objective/hypothesis: The forces exerted during a 1.5-Tesla MRI evaluation on the internal magnet of a cochlear implant (CI) raise concern about the safety for CI recipients. This study determines the magnitude of force required to fracture the floor of a CI receiver bed.