Tonotopy in human auditory cortex examined with functional magnetic resonance imaging.

Tonotopic organization within the human auditory cortex was investigated with functional magnetic resonance imaging (fMRI) using the blood oxygenation level-dependent (BOLD) contrast mechanism. Single-frequency pulsed tones were alternated with no-tone conditions to elicit stimulus-specific functional activity. Differential frequency-specific activity was imaged within the auditory cortex Activations for high-frequency tones were located more posteriorly and medially than those for low-frequency tones.

Isoflurane anesthesia blunts cerebral responses to noxious and innocuous stimuli: a fMRI study.

We used functional magnetic resonance imaging to determine how isoflurane affected cerebral neuronal activation resulting from noxious and innocuous stimuli. Five male volunteers were subjected to mild electrical shock and tactile stimuli applied to the hand. During low (0.

Lack of sympathetic involvement in dermatitis confined to the median nerve territory. A case report.

Both decreased and increased sympathetic nerve activity has been suggested as a possible underlying mechanism in inflammatory skin lesions. Modulation of sympathetic function has been proposed in the treatment of dermatitis. This case report describes the investigation strategy and normal findings in a case of dermatitis strictly confined to the median nerve territory, illustrating the need for specific tests of sympathetic function when pharmacological as well as physical sympatho-modulatory therapies are considered.

Reduction of spastic hypertonia in patients with spinal cord injury: a double-blind comparison of intravenous orphenadrine citrate and placebo.

Spasticity is one of the major problems affecting the outcome of rehabilitation in paraplegic patients. Orphenadrine citrate possesses an effective muscle relaxant action in many pathologies. Nevertheless, despite a recognized central site of action, no controlled data are available on its use in the treatment of spastic hypertonia in patients with spinal cord injuries.

A molecular receptor-binding contrast agent for magnetic resonance imaging of the liver.

Rationale And Objectives: A gadolinium complex of polydiethylenetriamine pentaacetic acid polyneogalactosyl polylysine (Gd-DTPA-gal-PL) was developed and tested as a paramagnetic contrast agent for magnetic resonance (MR) imaging of the liver. The agent was designed for receptor-mediated uptake by the asialoglycoprotein receptor (ASGP-R), which is unique to hepatocytes and exhibits high specificity for galactose-terminated glycoconjugates.

Methods: Polylysine was alkylated with a mixed anhydride of diethylenetriamine pentaacetic acid.

Functional magnetic resonance imaging depicts the brain in action.

In summary, FMRI is a new technique for discovering the organization and function of the brain. The ability rapidly and non-invasively to image regional cerebral blood flow, blood volume, and blood oxygenation may strengthen diagnoses in neurology, neurosurgery, and trauma medicine. The ability to localize specific functions in an individual's brain will have a large impact on the planning of therapeutic interventions, and in predicting outcomes after disease and injury.

Estimation of total coronary artery flow using measurements of flow in the ascending aorta.

This paper describes a technique for estimation of total (right+left) coronary artery flow using MRI flow measurements in the ascending aorta. The technique is based on the principle that the flow in a vessel branch is equal to the difference of the net flow measured above and below the branch ostia. Aortic net flow is measured at four or more axial oblique slices from below the aortic valve to above the highest location of the coronary vessel ostia in late diastole.

Electromyographic signal frequency analysis in evaluating muscle fatigue of patients with peripheral arterial disease.

Peripheral arterial disease (PAD) patients are commonly classified on the basis of subjective evaluations of pain and fatigue. Surface electromyography (EMG) is an objective method for studying peripheral muscle fatigue. Fifteen patients with PAD and 15 healthy volunteers matched for age and sex were studied.

Noninvasive measurement of renal hemodynamic functions using gadolinium enhanced magnetic resonance imaging.

A technique for the assessment of single kidney hemodynamic functions utilizing a novel MR pulse sequence in conjunction with MR contrast material administration is described. Renal extraction fraction (EF) is derived by measuring the concentration of the incoming contrast agent in the renal artery and the outgoing concentration in the renal vein. The glomerular filtration rate (GFR) can then be determined by the product of EF and renal plasma flow.

The effect of position on magnetic resonance evaluation of cerebrospinal fluid shunt function.

Since cerebrospinal fluid shunt malfunction is common and its diagnosis often requires invasive testing, we have evaluated magnetic resonance imaging (MRI) as a noninvasive test for shunt function. In prior experiments, MRI has been shown to be capable of detecting flows as low as 0.4 cc h-1 in shunt systems.

Experimental study of the effects of "fractional" gating on flow measurements.

Velocity encoded phase imaging is subject to errors from phase and amplitude variations of the k-space data caused by beat-to-beat variations of the flow. Fractional cardiac gating is defined as asynchronous gating with each phase encode step occupying a fixed fraction of the RR interval. The gating fraction is the inverse of the number of phase encode steps taken per RR interval.

Blood flow measurements in the aorta and major arteries with MR velocity mapping.

The purpose of this study was to measure antegrade and retrograde flow in the aorta and the major arterial pathways in the body noninvasively with cine magnetic resonance (MR) velocity mapping, to determine the hemodynamic significance of retrograde flow in arteries. Two hundred forty cine velocity maps for blood flow measurements were obtained at 29 sites in the aorta and the major arteries in 31 healthy human subjects of varying age at rest. Synchronous or isolated antegrade and retrograde flow was found in the entire aorta and in arteries supplying muscles.

Carotid and vertebral artery blood flow in left- and right-handed healthy subjects measured with MR velocity mapping.

The goal of the study was to establish normal carotid artery flow rates in left-handed and right-handed individuals as a standard against which patients with carotid artery disease could be compared. Antegrade and retrograde flow were measured in the ascending aorta, in the right and left common, internal, and external carotid arteries, and in the vertebral arteries of 12 healthy subjects. Five subjects were right-handed, five left-handed, and two ambidextrous.

Algorithms for improving calculated streamlines in 3-D phase contrast angiography.

Streamline display is a unique alternative to cross-sectional slice or projection display, because streamlines more clearly show the patterns of blood flow within the vessel. Flow patterns associated with atherosclerosis, such as streamline separation and recirculation, can be quickly identified with this display. Streamlines can be calculated using velocity data obtained from 3-D phase contrast angiographic pulse sequences.

Measurement of coronary artery flow reserve by magnetic resonance velocity mapping in the aorta.

Coronary artery flow occurs predominantly in diastole via retrograde flow in the ascending aorta, some of which supplies the coronary arteries while the remainder recirculates in the ascending aorta. We used magnetic resonance velocity mapping to measure global coronary artery diastolic flow in the ascending aorta. In eight normal subjects and in four patients with possible ischaemic heart disease but with normal perfusion scans, the mean coronary flow reserve (CFR) was 269 ml/min.

Blood flow measurement using variable velocity encoding in the RR interval.

Velocity-encoded phase imaging using asynchronous gating requires input of a velocity encoding value to set the velocity sensitivity of the pulse sequence. The raw data interpolation and reconstruction scheme that the pulse sequence uses forces the encoding value to be constant throughout the RR interval. The sequence and the raw data interpolation scheme were modified to allow two velocity encodings during the RR interval.

RF pulse design using the inverse scattering transform.

The inverse scattering transform (IST) is a mathematical transformation that can be used to derive RF pulses from functions called continuous spectra describing the final state of the spin system. This paper reviews three seemingly unrelated numerical algorithms that have appeared in the literature, and shows that they are all derivable from the IST. When the continuous spectra are rational, the finite rank kernel method is used to convert the IST to a matrix equation that is easily solved.

[Chronic progressive obliterating arteriopathy and muscle fatigue: the role of frequency analysis of the electromyographic signal].

Clinical evaluation of patients with peripheral arterial disease (PAD) is mainly based on Fontaine's classification, in which pain is the most important element. The use of objective techniques can allow a more precise evaluation, since pain is always subjective. In PAD patients, pain is frequently associated with early fatigue.

Cardiovascular effects of TENS: heart rate variability and plethysmographic wave evaluation in a group of normal subjects.

Transcutaneous electrical nerve stimulation (TENS) is generally used in controlling pain. Side effects are not frequent, but sometimes do happen. Among these, automatic disturbances have been described.

The role of ischaemia in the analgesia which follows Bier's block technique.

The effect of 30-min tourniquet ischaemia (Bier's block) on the antidromic homolateral left median nerve sensory potential (SP) and on the bilateral sympathetic skin response (SSR) was studied in 6 healthy volunteers. The SSR was provoked both acoustically and by electrical stimulation of the median nerve; the latter stimulus was also used to provoke the SP. After 28 min of tourniquet ischaemia, the electrical stimulus failed to provoke the SP and bilateral SSR, indicating blockade of the afferent limb of the reflex.

Factors influencing the accuracy and precision of velocity-encoded phase imaging.

Velocity-encoded phase contrast imaging is being used increasingly in clinical imaging for quantization of blood flow. In this study, the accuracy and precision of ascending aorta flow measurements were found to depend on several subtle aspects of the scan prescription and image analysis. While the usual scan parameters such as TR, TE, and flip angle gave incremental changes in the flow measurements, four additional factors that had a much greater effect on the measurements were identified.

A case of Miller Fisher syndrome: atypical findings and therapeutic considerations.

The Miller Fisher syndrome (MFS) is generally considered to be a disease of the peripheral nervous system. In some cases contemporary involvement of the central nervous system has been described (CNS). We report a case in which it was possible to prove involvement of cranial nerves VII, VIII, IX and X and to exclude CNS involvement.

The analytic theory, optimization, and performance of transparent pulses.

Transparent pulses are defined by the property of having no net effect on stationary spins, while selectively nutating and dephasing flowing spins. They are derived from the inverse scattering transform, a nonlinear extension of the inverse Fourier transform. They can be used as presaturation pulses to suppress selectively the signal from flowing spins.

Magnetic resonance imaging analysis of extremely slow flow in a model shunt system.

Shunt malfunction is common and its diagnosis may require invasive testing that may be inaccurate or result in complications. Magnetic resonance imaging (MRI) may prove to be a useful noninvasive test of shunt function as it has been shown that MRI is capable of measuring cerebrospinal fluid (CSF) flows from 2 ml/h to 40 ml/h in model systems. Since flows in functioning shunt systems can be less than 2 ml/h, MRI must be sensitive enough to detect flow in this range in order to be a valid test for shunt function.