Micheal D. Phillips

Correlations in low-frequency BOLD fluctuations reflect cortico-cortical connections.

Cross-correlation of low-frequency temporal fluctuations (<0.08 Hz) was used to correlate widely separated anatomic regions during continuous performance of a spatial working memory task. The regions of highest correlation to right-hemisphere dorsolateral prefrontal cortex correspond to the regions of largest baseline signal change in a conventional block-style functional MRI paradigm. Additionally, it is shown that the correlations between elements of the functional network increase during performance of a task that activates the network when compared to a task that does not directly stimulate the functionally connected network.

It is not about the bike, it is about the pedaling: forced exercise and Parkinson's disease.

Forced exercise has resulted in neuroprotective effects and improved motor function in animal studies. These promising results have not yet been translated fully to humans with Parkinsons disease (PD), as traditional exercise interventions have not yielded global improvements in function. A novel forced exercise intervention is described that has resulted in improved motor function and central nervous system function in PD patients.

Improving clinical histories on radiology requisitions

PURPOSE The Health Care Financing Administration (HCFA) regards billing for radiologic examinations without an appropriate indication as unlawful, and both the referring physician and the radiologist are liable. HCFA regulations are interpreted as requiring that all requisitions for radiologic examinations include a current diagnosis and appropriate indication for the study. The purpose of this investigation was to determine the rates at which requisitions currently meet these criteria and to assess the effectiveness of a simple intervention designed to improve them. MATERIALS AND METHODS One hundred fifty consecutive chest radiography requisitions were examined to determine the rate at which current diagnoses and appropriate indications were present. An intervention was then implemented that included a month-long effort to inform referring physicians and radiologists of HCFA regulations, followed by a 1-week period during which requested examinations were not performed unless accompanied by a clinical diagnosis and appropriate indication. Another 150 consecutive chest radiography requisitions were then assessed to determine the effect of the intervention. A 3-month follow-up sample of a third set of 150 consecutive requisitions was then obtained. RESULTS The intervention produced a 69% decrease in the rate at which current diagnoses were missing from requisitions, and a 61% decrease in the corresponding rate for appropriate indications. Both results are significant with chi2 analysis at the P = .001 level. After 3 months with no additional intervention, rates decayed back toward baseline, with only a 35% remaining decrease for current diagnosis and an 18% decrease for appropriate indication. CONCLUSION The intervention performed in this study significantly reduces the rate of noncompliance with HCFA regulations. However, this improvement decays over time if it is not reinforced.

Quantitative comparison of functional contrast from BOLD-weighted spin-echo and gradient-echo echoplanar imaging at 1.5 Tesla and H215O PET in the whole brain

Spin-echo and gradient-echo echoplanar functional magnetic resonance imaging (fMRI) studies at 1.5 Tesla (T) were used to obtain blood oxygenation level-dependent (BOLD) contrast images of the whole brain in seven strongly right-handed women during execution of a complex motor task. Five subjects underwent subsequent H215O positron emission tomography (PET) studies while performing the same task. Group-averaged results for changes in the MRI relaxation rates R2* and R2 at 1.5T in response to neuronal activation in nine cortical, subcortical, and cerebellar motor regions are reported. Results for each method are grouped according to tissue type—cerebral cortex (precentral gyrus and supplementary motor area), subcortical regions (thalamus and putamen), and cerebellar cortex (superior lobule). The observed changes in R2* from activation-induced oxygenation changes were more variable across brain regions with different tissue characteristics than observed changes in R2. The ratio of ΔR2* to ΔR2 was 3.3 ± 0.9 for cerebral cortex and 2.0 ± 0.6 for subcortical tissue. ΔR2*, ΔR2, and relative blood flow changes were ΔR2* = −0.201 ± 0.040 s−1, ΔR2 = −0.064 ± 0.011 s−1, and Δf/f = 16.7 ± 0.8% in the cerebral cortex; ΔR2* = −0.100 ± 0.026 s−1, ΔR2 = −0.049 ± 0.009 s−1, and Δf/f = 9.4 ± 0.7% in the subcortical regions; and ΔR2* = −0.215 ± 0.093 s−1, ΔR2 = −0.069 ± 0.012 s−1, and Δf/f = 16.2 ± 1.2% in the cerebellar cortex.

Iron deposition in pain-regulatory nuclei in episodic migraine and chronic daily headache by MRI.

Background.— Progression of migraine toward a more disabling chronic form of at least 15 days/month is linked with frequency of attacks. Magnetic resonance imaging (MRI) findings of iron accumulation in the brain, especially in periaqueductal gray and red nucleus, have been correlated with both duration of illness and frequency of attacks.

Comparison of hemispheric lateralization using four language tasks

Introduction The determination of hemispheric language dominance in individuals is important in many clinical contexts, particularly for the pre-operative assessment of patients undergoing neoplasm resection or temporal lobectomy for medically intractable epilepsy. The Wada test has been the clinical standard for this determination for many years. Recently, functional magnetic resonance imaging (FMRI) has been used to assess hemispheric language dominance, and shows good correspondence to Wada test results in individual patients. However, it is unclear which FMRI behavioral paradigms best demonstrate hemispheric language dominance. The purpose of this study was to compare in healthy subjects the hemispheric asymmetry of activation maps from four different language paradigms.

Resting state BOLD fluctuations reflect impaired functional connectivity in multiple sclerosis

Introduction It has been shown there are correlations in low-frequency temporal BOLD fluctuations between functionally related brain regions in normal humans( 1,2). MS is a common demyelinating neurologic disorder. Progressive forms of MS often result in extensive destruction of the white matter within the spinal cord and brain. MS lesions can impair neuronal transmission through the affected white matter. Our hypothesis is that, if the observed correlations in low-frequency BOLD fluctuations are a reflection of functional connectivity, then MS patients with a large lesion volume should show abnormally low correlations between anatomic regions which are highly correlated in normal subjects.

Temporal correlations in low frequency BOLD fluctuations reveal functional networks

Introduction It has been demonstrated that very low frequency temporal fluctuations in rapidly sampled blood oxygenation level dependent (BOLD) weighted echoplanar imaging data are phase-locked between many right and left-hemisphere symmetric functional cortices such as precentral gyrus (i.e. motor cortex) in human subjects at rest (1, 2). It has been postulated by the authors that these correlations in lowfrequency fluctuations are a reflection of functional connectivity. It has also been shown that Resting-state acquisitions are, in fact, timeseries acquisitions in which the subject is asked to refrain from overt activity. The “state” of the brain is otherwise uncontrolled. A recent experiment by Franson et al showed residual effects of BOLD signal lasting several tens of seconds after very brief neuronal stimulation(3). Thus, a possible explanation of the a posterion’ observations of low-frequency temporal correlation between functionally connected anatomic regions is that uncontrolled brain activity excites these connected regions and subsequent filtering isolates the long-term effects from higher frequency noise fluctuations, which are non-specific to function (e.g. cardiac and respiratory-related BOLD fluctuations). As a further test of this, we designed an experiment in which subjects continuously performed a cognitive task, which excites a network of brain regions. The task is performed at a rate of 0.4Hz. The data are then filtered to remove fluctuations above 0.08Hz (corresponding to a period of 12.5 seconds). If low frequency fluctuations are a measure of functional connectivity, then the correlations between brain regions in the filtered data should reflect the network of brain regions involved in the task.

Functional Discrimination of Thalamic Nuclei Using BOLD Contrast fMRI at 1.5 T

Functional magnetic resonance imaging (fMRI) techniques have been extensively used in investigating functionality of various cortical areas. However, these techniques can also be applied to the studies of neuronal activation in small gray matter structures of the thaiamus, basal ganglia, and brainstem. The thalamus is located superior to the brainstem and is composed of numerous nuclei differentiated by their fibrous connections to different brain regions. Some of the thalamic nuclei have spatial dimensions approaching 10 mm. Chen et ai reported that that the lateral geniculate nucleus (LGN) of the thalamus and pulvinar of the thalamus could be discriminated using fMRI techniques at 4 tesla (T) [1]. Guimares et al successfully used functional magnetic resonance imaging at l .5 T to detect subcortical auditory activation in the medial geniculate nucleus (MGN) [2]. In this work we demonstrate that adjacent thalamic nuclei can be clearly discriminated using bloodoxygenation level dependent (BOLD) fMRI at 1.5 T. Six normal subjects were studied in a protocol designed to detect thalamic activation in simple auditory and visual tasks. The hypothesis is that the medial geniculate nucleus of the thalamus will be activated in the auditory task while the lateral geniculate nucleus of the thalamus will be detected in the visual task. The physical dimensions of these two adjacent thalamic nuclei are approximately equal to the spatial resolution of the acquired functional images (3.5 mm) thus illustrating the spatial specificity of the BOLD fMRI technique in subcortical structures. In addition, the LGNMGN Separation distance is comparable to the in-plane spatial resolution of the acquired data, which constitutes a test of the spatial resolving power for BOLD fMRImethodat 1.5 T

Tc-99m HMPAO brain SPECT imaging for the diagnosis of gray matter heterotopia.

A 36-year-old right-handed woman with a 24-year history of medically refractory complex-partial seizures described as spells of staring and lip licking was referred for brain SPECT imaging. Tomographic imaging after intravenous administration of Tc-99m HMPAO and acetazolamide revealed abnormal focal areas of increased radiopharmaceutical accumulation in the white matter of the occipital region located at and above the level of the right lateral ventricle posteriorly. A magnetic resonance imaging (MRI) study performed for comparison showed multiple corresponding foci of ectopic gray matter. This report reveals the utility of SPECT imaging in the localization of double cortex in patients with longstanding seizure disorders.