Search PubMed⌕ Search

Biomedical subjects

J D Eastwood

Publications and source records attributed to J D Eastwood.

17 recordsLinked to original sources
PubMed2006

Dynamic CT perfusion imaging in subarachnoid hemorrhage-related vasospasm.

BACKGROUND AND PURPOSE: Nimodipine is a therapy that reduces morbidity and mortality in patients with subarachnoid hemorrhage (SAH), though the mechanisms by which it does so are not well understood. In a rabbit model of SAH, we studied the effects of nimodipine by using functional CT imaging. We hypothesized that the nimodipine treatment group would have (1) increased mean basilar artery diameter, (2) less diminished cerebral blood flow (CBF) following vasospasm, and (3) better neurologic outcomes. METHODS: SAH was induced in 26 New Zealand White rabbits randomized to 2 groups: treated (nimodipine) or control (no treatment). CT perfusion and CT angiography were used to measure CBF and basilar artery diameter at baseline, 10, 30, and 60 minutes after SAH, and on days 3, 5, 7, 9, and 16. Neurologic assessments were performed on each day of scanning. RESULTS: Basilar artery diameter in the treated group was greater than in the control group post-SAH (P < .05). When vasospasm was >15%, CBF in the nimodipine group was significantly greater than in the control group in the brain stem, cerebellum, parieto-occipital cerebrum, and deep gray matter (P < .05). Neurologic scores in the nimodipine group were significantly better than in the control group on days 5 and 9 (P < .05). CONCLUSION: Animals treated with nimodipine showed (1) increased mean basilar artery diameter, (2) improved neurologic outcome, and (3) increased mean CBF despite no significant difference in the incidence and severity of delayed vasospasm. These data provide a basis for future studies comparing the efficacy of new treatments for SAH to that of nimodipine.

Angiography↗
PubMed2005

Comparative overview of brain perfusion imaging techniques.

Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are: Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), Xenon-enhanced Computed Tomography (XeCT), Dynamic Perfusion-computed Tomography (PCT), Magnetic Resonance Imaging Dynamic Susceptibility Contrast (DSC), Arterial Spin-Labeling (ASL), and Doppler Ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow (CBF) or volume (CBV). All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview, established by consensus among specialists of the various techniques. For clinicians, this paper should offers a clearer picture of the pros and cons of currently available brain perfusion imaging techniques, and assist them in choosing the proper method in every specific clinical setting.

Cerebrovascular Circulation↗
PubMed2005

Hyperperfusion on perfusion computed tomography following revascularization for acute stroke.

PURPOSE: To describe the findings of hyperperfusion on perfusion computed tomography (CT) in four patients following revascularization for acute stroke. MATERIAL AND METHODS: In 2002-2003, among a series of 6 patients presenting with an acute stroke and treated with intra-arterial thrombolysis, we observed the presence of hyperperfusion in 3 patients on the follow-up CT perfusion. We included an additional patient who was treated with intravenous thrombolysis and who had hyperperfusion on the follow-up CT perfusion. We retrospectively analyzed their CT perfusion maps. Cerebral blood volume (CBV) and cerebral blood flow (CBF) maps were compared between the affected territory and the normal contralateral hemisphere. RESULTS: In the four patients, the mean CBV and CBF were 3.6 +/- 2.0 ml/100 g and 39 +/- 25 ml/100 g/min in the affected territory compared to the normal side (mean CBV = 2.7 +/- 2.1 ml/100 g, mean CBF = 27 +/- 23 ml/100 g/min). There was no intracranial hemorrhage in the hyperperfused territories. At follow-up CT, some hyperperfused brain areas progressed to infarction, while others retained normal white to gray matter differentiation. CONCLUSION: CT perfusion can demonstrate hyperperfusion, which can be seen in an ischemic brain territory following recanalization.

Aged↗
PubMed2001

Practical injection-rate CT perfusion imaging: deconvolution-derived hemodynamics in a case of stroke.

Previously reported methods of dynamic, contrast-enhanced, CT perfusion imaging in acute stroke have been promising but substantially limited by their dependence on very rapid rates of injection (typically 10-20 ml/s in an arm vein). Newly available deconvolution software permits the use of lower rates of injection (e. g., 3-4 ml/s), and rapidly provides maps of cerebral blood flow, cerebral blood volume and mean transit time. We report the potential of CT perfusion imaging performed with an injection rate of 4 ml/s to provide information on the extent of hemodynamic abnormality, and to help distinguish viable from nonviable ischemic tissue. The slower injection rates permitted by deconvolution analysis substantially enhance the practicality of CT perfusion imaging for studying stroke.

Brain↗
PubMed2001

Perception without awareness: perspectives from cognitive psychology.

Four basic approaches that have been used to demonstrate perception without awareness are described. Each approach reflects one of two types of experimental logic and one of two possible methods for controlling awareness. The experimental logic has been either to demonstrate a dissociation between a measure of perception with awareness and a measure that is sensitive to perception without awareness or to demonstrate a qualitative difference between the consequences of perception with and without awareness. Awareness has been controlled either by manipulating the stimulus conditions or by instructing observers on how to distribute their attention. The experimental findings based on all four approaches lead to the same conclusion; namely, stimuli are perceived even when observers are unaware of the stimuli. This conclusion is supported by results of studies in which awareness has been assessed with either objective measures of forced-choice discriminations or measures based on verbalizations of subjective conscious experiences. Given this solid empirical support for the concept of perception without awareness, a direction for future research studies is to assess the functions of information perceived without awareness in determining what is perceived with awareness. The available evidence suggests that information perceived without awareness both biases what stimuli are perceived with awareness and influences how stimuli perceived with awareness are consciously experienced.

Attention↗
PubMed2001

Increased brain apparent diffusion coefficient in children with neurofibromatosis type 1.

PURPOSE: To describe the changes in brain water diffusibility in five anatomic locations in children with neurofibromatosis type 1 (NF 1) compared with these changes in control subjects and to describe the water diffusibility changes associated with hyperintense basal ganglia lesions in children with NF 1. MATERIALS AND METHODS: Twenty highly related pairs of children consisting of one child with NF 1 and one unaffected child were examined. Prospective comparisons of isotropic apparent diffusion coefficient (ADC) values at five anatomic locations were performed, with and without T2-hyperintense lesions included. Retrospective analysis of hyperintense globus pallidus lesions in 16 children and in the paired control subjects also was performed. RESULTS: Significant increases in ADC values were seen in all five anatomic locations in the NF 1 group. The greatest increases were seen in the globus pallidus (14%; P =.002) and brachium pontis (10.8%; P =.003). With exclusion of hyperintense lesions, significant ADC increases were measured in four locations. Significant ADC increases were seen in hyperintense globus pallidus lesions in the NF 1 group compared with ADC values in the normal-appearing contralateral globus pallidus (4.9%; P =.02) and those in the globus pallidus of the paired control subjects (16%; P =.003). CONCLUSION: Significant ADC increases were measured both in the hyperintense lesions and in the normal-appearing areas of the brain in children with NF 1.

Adolescent↗
PubMed2001

Differential attentional guidance by unattended faces expressing positive and negative emotion.

Four experiments were conducted to evaluate whether focal attention can be guided by an analysis of the emotional expression in a face. Participants searched displays of 7, 11, 15, and 19 schematic faces for the location of a unique face expressing either a positive or a negative emotion located among distractor faces expressing a neutral emotion. The slopes of the search functions for locating the negative face were shallower than the slopes of the search functions for locating the positive face (Experiments 1A and 2A). When the faces were inverted to reduce holistic face perception, the slopes of the search functions for locating positive and negative faces were not different (Experiments 1B and 2B). The results suggest that the emotional expression in a face can be perceived outside the focus of attention and can guide focal attention to the location of the face.

Adult↗
PubMed2000

Does unattended information facilitate change detection?

Changes between alternating visual displays are difficult to detect when the successive presentations of the displays are separated by a brief temporal interval. To assess whether unattended changes attract attention, observers searched for the location of a change involving either a large or a small number of features, in pairs of displays consisting of 4, 7, 10, 13, or 16 letters (Experiment 1) or digits (Experiments 2 and 3). Each display in a pair of displays was presented for 200 ms, and either a blank screen (Experiments 1 and 2) or a screen of equal luminance to the letters and digits (Experiment 3) was presented for 80 ms between the alternating displays. In all experiments, the search function for locating the larger change was shallower than the search function for locating the smaller change. These results indicate that unattended changes play a functional role in guiding focal attention.

Adult↗
PubMed2000

An unusual variant of the fronto-orbital artery.

A patient with a rare variation of the fronto-orbital artery is presented. In this case, the fronto-orbital artery arises from the A1 segment of the contralateral anterior cerebral artery. The angiographic findings in this case are illustrated and discussed. The importance of recognizing this variant is related to the planning of surgery or endovascular therapy in the anterior cerebral artery region.

Adult↗
PubMed1998

The folly of effort: ironic effects in the mental control of pain.

During exposure to pain, participants who were engaged in hypnotic analgesia or stress inoculation provided pain reports every 5 s and 45 s, respectively. It was found that the frequency of pain reporting had a significant effect on participants' level of experienced pain. This finding is discussed in the context of important methodological implications for laboratory investigations of analgesia. Furthermore, preliminary evidence was obtained suggesting that high hypnotizables in hypnotic analgesia remained relatively undisrupted by frequent pain reporting. Based on Wegner's (1994) ironic process theory, it is argued that this pattern of results is inconsistent with theories of hypnosis that propose that hypnotized individuals intentionally engender responses while remaining unaware of their sustained, deliberate effort. The obtained pattern of results was, however, predicted from the dissociated control model of hypnosis (Bowers, 1990, 1992).

Adult↗
PubMed1998

New techniques in magnetic resonance imaging.

Technical developments in magnetic resonance imaging of the brain and orbits provide a challenge to radiologists and practicing clinicians alike. Several new trends in brain imaging are reviewed, including fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and perfusion and functional magnetic resonance imaging. These techniques are increasingly used in the clinical environment. Two innovative magnetic resonance techniques for imaging the orbit are also reviewed.

Brain↗
PubMed1998

Retropharyngeal effusion in acute calcific prevertebral tendinitis: diagnosis with CT and MR imaging.

Three patients with the diagnosis of acute calcific prevertebral tendinitis underwent CT or a combination of CT and MR imaging, which showed previously described findings of calcifications within the tendons of the longus colli muscles. In addition, however, we detected a retropharyngeal effusion in all three patients. The importance of this finding lies in the need to differentiate this effusion from retropharyngeal infection.

Acute Disease↗
PubMedDate not supplied

Diffusion-weighted MR imaging of the normal human spinal cord in vivo.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging is a robust technique for evaluation of a variety of neurologic diseases affecting the brain, and might also have applications in the spinal cord. The purpose of this study was to determine the feasibility of obtaining in vivo diffusion-weighted images of the human spinal cord, to calculate normal apparent diffusion coefficient (ADC) values, and to assess cord anisotropy. METHODS: Fifteen healthy volunteers were imaged using a multi-shot, navigator-corrected, spin-echo, echo-planar pulse sequence. Axial images of the cervical spinal cord were obtained with diffusion gradients applied along three orthogonal axes (6 b values each), and ADC values were calculated for white and gray matter. RESULTS: With the diffusion gradients perpendicular to the orientation of the white matter tracts, spinal cord white matter was hyperintense to central gray matter at all b values. This was also the case at low b values with the diffusion gradients parallel to the white matter tracts; however, at higher b values, the relative signal intensity of gray and white matter reversed. With the diffusion gradients perpendicular to spinal cord, mean ADC values ranged from 0.40 to 0.57 x 10(-3) mm2/s for white and gray matter. With the diffusion gradients parallel to the white matter tracts, calculated ADC values were significantly higher. There was a statistically significant difference between the ADCs of white versus gray matter with all three gradient directions. Strong diffusional anisotropy was observed in spinal cord white matter. CONCLUSION: Small field-of-view diffusion-weighted images of the human spinal cord can be acquired in vivo with reasonable scan times. Diffusion within spinal cord white matter is highly anisotropic.

Adult↗