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James D Eastwood

Publications and source records attributed to James D Eastwood.

16 recordsLinked to original sources
PubMed2005

Comparative overview of brain perfusion imaging techniques.

BACKGROUND AND PURPOSE: Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. SUMMARY OF REVIEW: 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. CONCLUSIONS: For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting.

Aged↗
PubMed2005

Assessment of apparent diffusion coefficient in normal and degenerated intervertebral lumbar disks: initial experience.

PURPOSE: To determine prospectively the diffusibility of water in normal lumbar disks in adults by using the mean apparent diffusion coefficient (ADC) and to determine if a relationship exists between disk ADC and magnetic resonance (MR) findings of disk degeneration. MATERIALS AND METHODS: The study was approved by the Institutional Review Board, and all participants gave written informed consent prior to enrollment. Diffusion-weighted MR imaging of the lumbar spine was performed in 39 patients (all men; mean age, 53 years) and five volunteers (all men; mean age, 31 years). ADC values were recorded for each disk. All disks were visually graded by two independent observers as being normal or as showing at least one of three MR findings of degeneration on sagittal T2-weighted images. Mean ADC values of normal disks were compared with those of degenerated disks and were correlated with age and anatomic location. Data were analyzed by using Kendall correlation statistics, Mantel-Haenszel statistics, and a paired two-tailed Student t test. RESULTS: The mean ADC value was 2.27 x 10(-3) mm(2)/sec +/- 0.58 (+/- standard deviation) in normal disks and 2.06 x 10(-3) mm(2)/sec +/- 0.47 in abnormal disks (9% reduction, P = .006). A statistically significant dependence of lumbar disk ADC on anatomic location was reported (analysis of variance, P < .001), with lower ADC values seen in more caudal disks. There was no association between age and mean disk ADC. CONCLUSION: A statistically significant decrease was seen in the ADC values of degenerated lumbar disks when compared with ADC values of normal disks. More caudal disks, even when normal, showed lower ADC values than more cephalic disks.

Adult↗
PubMed2005

Brain morphometry, T2-weighted hyperintensities, and IQ in children with neurofibromatosis type 1.

BACKGROUND: Larger gray matter (GM) volume in healthy children is correlated with higher IQ. Children with neurofibromatosis type 1 (NF1) have larger brains, their magnetic resonance images frequently show T2-weighted hyperintensities, and their IQs are lower. OBJECTIVES: To confirm the hypotheses that (1) children with NF1 have larger GM and white matter volumes, (2) the greatest volume differences are in the frontal and parietal regions and in children with NF1 with hyperintensities, and (3) GM volume is inversely related to IQ in children with NF1. DESIGN: Wechsler Intelligence Scale for Children-Third Edition IQ testing and measurement of cerebral volumes and hyperintensities in brain magnetic resonance images were performed on 36 children with NF1 and on 36 matched relatives who served as control subjects. RESULTS: Gray matter and white matter volumes were significantly larger in children with NF1. The greatest difference was observed in cerebral white matter volume, predominantly in the frontal lobes, whereas the greatest difference in GM volume was in the temporal, parietal, and occipital regions. In controls, IQ was significantly related to GM volume, but in children with NF1, IQ was not inversely associated with GM volume, although IQs of children with NF1 were significantly lower. CONCLUSIONS: Children with NF1 do not have the normal relationship between GM volume and IQ. Larger GM volume in the posterior brain regions and larger white matter volumes in the frontal brain regions contribute to the larger brain volume in children with NF1.

Brain↗
PubMed2004

Subcutaneous administration of nimodipine improves bioavailability in rabbits.

We compared subcutaneous and oral methods of nimodipine administration to determine a method of nimodipine administration that maintained serum levels at or above the optimal therapeutic concentration (7 ng/ml). Plasma concentrations of nimodipine were measured in New Zealand White rabbits (2.6-3.9 kg). First, peak plasma concentration (C(max)), time to reach peak plasma concentration (T(max)), and area under the curve (AUC) parameters were calculated and compared between animals receiving oral or subcutaneous nimodipine (5-15 mg/kg). Next, plasma concentrations were measured 24 h after subcutaneous administration of 2.5 mg/kg of nimodipine in healthy animals and animals with experimentally induced SAH. C(max), T(max) and AUC parameters were significantly greater for subcutaneous compared to oral nimodipine administration, irrespective of dose. Mean nimodipine concentrations at 24 h were >7 ng/ml in both healthy animals (12.9 +/- 10.0 ng/ml) and in animals with SAH (11.8 +/- 4.6 ng/ml) that received 2.5 mg/kg of subcutaneous nimodipine. In this model, the subcutaneous method of nimodipine administration consistently maintains plasma levels at or above the optimal therapeutic concentration, whereas oral administration fails to do so.

Animals↗
PubMed2004

User-defined vascular input function curves: influence on mean perfusion parameter values and signal-to-noise ratio.

The authors reviewed 40 computed tomographic (CT) perfusion studies to determine the effect of arterial and venous input function properties on perfusion parameter values and tissue signal-to-noise ratio (SNR). A 10-subject subset was analyzed to evaluate the effect of varying venous region of interest (ROI) locations. Venous peak enhancement correlated significantly with mean tissue cerebral blood flow (CBF) and cerebral blood volume (CBV); venous and arterial peak enhancement correlated significantly with SNR of perfusion maps. Different ROI locations within the same vein resulted in significantly different CBV and CBF values. Perfusion map parameters are related to peak enhancement within user-selected ROIs. Optimal ROI selection should limit variability and increase quality of CT perfusion images.

Adult↗
PubMed2004

The effect of varying user-selected input parameters on quantitative values in CT perfusion maps.

RATIONALE AND OBJECTIVES: Deconvolution-based software can be used to calculate quantitative maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) from first-pass computed tomography perfusion (CTP) datasets. The application of this software requires the user to select multiple input variables. The purpose of this study was to investigate the degree to which both major and minor variations of these user-defined inputs would affect the final quantitative values of CBF, CBV, and MTT. MATERIALS AND METHODS: A neuroradiologist constructed CBF, CBV, and MTT maps using standard methodology with commercially available software (GE Functool Version 1.9s) from CTP datasets of three acute stroke patients. Each map was reconstructed multiple times by systematically and independently varying the following parameters: postenhancement and preenhancement cutoff values, arterial and venous region-of-interest (ROI) placement, and arterial and venous ROI size. The resulting quantitative CTP values were compared using identical ROIs placed at the infarct core. RESULTS: Major variations of either arterial ROI placement or arterial and venous ROI size had no significant effect on the mean CBF, CBV, and MTT values at the infarct core (p > .05). Even minor variations, however, in the choice of venous ROI placement or in pre- and postenhancement cutoff values significantly altered the quantitative values for each of the CTP maps, by as much as threefold. CONCLUSION: Even minor variations of user-defined inputs can significantly influence the quantitative, deconvolution-based CTP map values of acute stroke patients. Although quantitation was robust to the choice of arterial ROI placement and arterial or venous ROI size, it was strongly dependent on the choice of venous ROI location and pre- and postenhancement cut-off values. Awareness of these results by clinicians may be important in the creation of quantitatively accurate CTP maps.

Adult↗
PubMed2004

Sacral tuberculosis: a case report and review of the literature.

BACKGROUND: We present a patient with a heterogeneously enhancing lesion within the body of the sacrum and the sacral canal. Sacral tuberculosis (TB) was suspected because of a history of familial exposure. Few cases isolated to the sacrum have been reported in the literature. The characteristic histopathologic and magnetic resonance imaging (MRI) findings are also presented. CASE DESCRIPTION: A 31-year-old African-American male presented with an 8-month history of lower back pain radiating into his legs as well as numbness and weakness of the right foot. His history revealed PPD conversion following an exposure to active pulmonary TB 3 years prior for which he received 6 months of isoniazid prophylaxis. An MRI scan revealed a large heterogeneously enhancing lesion involving the sacrum with extension into the sacral canal. The patient underwent computed tomography (CT)- guided needle biopsy of the sacral lesion. Cytopathologic examination revealed caseating granulomas. Acid-fast bacilli cultures were positive for Mycobacterium tuberculosis. He was placed on a 6-month course of isoniazid, rifampin, pyrazinamide, and ethambutol. At 3-month follow-up, his examination and symptoms had improved. CONCLUSIONS: Sacral TB is an extremely rare cause of lower back pain with radiation into the lower extremities. TB should always be considered in the differential diagnosis of isolated sacral masses, especially in light of today's increasing multidrug resistance and immunosuppressed population.

Adult↗
PubMed2004

CT perfusion parameter values in regions of diffusion abnormalities.

BACKGROUND AND PURPOSE: Dynamic CT perfusion imaging is a rapid and widely available method for assessing cerebral hemodynamics in the setting of ischemia. Nevertheless, little is known about perfusion parameters within regions of diffusion abnormality. Since MR diffusion-weighted (DW) imaging is widely considered the most sensitive and specific technique to examine the ischemic core, new knowledge about CT perfusion findings in areas of abnormal diffusion would likely provide valuable information. The purpose of our study was to measure the CT-derived perfusion values within acute ischemic lesions characterized by 1) increased signal intensity on DW images and 2) decreased apparent diffusion coefficient (ADC) and compare these values with those measured in contralateral, normal brain tissue. METHODS: Analysis was performed in 10 patients with acute middle cerebral artery territory stroke of symptom onset less than 8 hours before imaging who had undergone both CT perfusion and DW imaging within 2 hours. After registration of CT perfusion and DW images, measurements were made on a pixel-by-pixel basis in regions of abnormal hyperintensity on DW images and in areas of decreased ADC. RESULTS: Significant decreases in cerebral blood flow and cerebral blood volume with elevated mean transit times were observed in regions of infarct as defined by increased signal intensity on DW images and decreased ADC. Comparison of perfusion parameters in regions of core infarct differed significantly from those measured in contralateral normal brain. CONCLUSION: CT perfusion findings of decreased cerebral blood flow, mean transit time, and cerebrovascular volume correlate with areas of abnormal hyperintensity on DW images and regions of decreased ADC. These findings provide important information about perfusion changes in acute ischemia in areas of diffusion abnormality.

Acute Disease↗
PubMed2003

Quantitative assessment of the time course of infarct signal intensity on diffusion-weighted images.

BACKGROUND AND PURPOSE: Diffusion-weighted (DW) MR imaging is important in evaluating acute stroke, and knowledge of the signal intensity changes associated with acute stroke is valuable. Our purpose was to model the time course of the signal intensity of infarcts and to characterize the apparent diffusion coefficient (ADC) and T2 effects on total signal intensity. METHODS: Ninety-two patients were included in this prospective cross-sectional study. Signal intensity in infarcts (4 hours to 417 days) and control regions were recorded on DW images (b = 0 and 1000 s/mm(2)), ADC maps, and ratio images (image with b = 1000 s/mm(2) divided by image with b = 0 s/mm(2)). Cubic spline functions were used for polynomial fitting. The time courses of log signal intensity with log time were modeled. The independent contributions of T2 and ADC to the total signal intensity were retrospectively compared at 0-63 hours, 3-10 days, 11-57 days, and 57 days onward. RESULTS: Mean signal intensity on DW images was maximal at 40 hours after infarction and normalized at 57 days. At 0-63 hours, the positive effect of ADC on signal intensity was greater than that of T2 (log value,13 +/- 0.04 vs 0.11 +/- 0.05; P =.04). At days 3-10, the positive T2 effect predominated (0.13 +/- 0.08 vs 0.08 +/- 0.04; P =.12). At 10-57 days, the positive T2 effect was greater than the negative ADC effect. After day 57, the negative ADC effect predominated. CONCLUSION: The signal intensity of infarcts on DW images normalizes at 57 days, which is substantially later than previously suggested. T2 (shine-through) effect contributes largely to the total infarct signal intensity.

Acute Disease↗
PubMed2003

Correlation of early dynamic CT perfusion imaging with whole-brain MR diffusion and perfusion imaging in acute hemispheric stroke.

BACKGROUND AND PURPOSE: Compared with MR imaging, dynamic CT perfusion imaging covers only a fraction of the whole brain. An important assumption is that CT perfusion abnormalities correlate with total ischemic volume. The purpose of our study was to measure the degree of correlation between abnormalities seen on CT perfusion scans and the volumes of abnormality seen on MR diffusion and perfusion images in patients with acute large-vessel stroke. METHODS: Fourteen patients with acute hemispheric stroke symptoms less than 12 hours in duration were studied with single-slice CT perfusion imaging and multislice MR diffusion and perfusion imaging. CT and MR perfusion studies were completed within 2.5 hours of one another (mean, 77 minutes) and were reviewed independently by two neuroradiologists. Hemodynamic parameters included cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Extents of abnormality on images were compared by using Kendall correlation. RESULTS: Statistically significant correlation was found between CT-CBF and MR-CBF abnormalities (tau = 0.60, P =.003) and CT-MTT and MR-MTT abnormalities (tau = 0.65, P =.001). Correlation of CT-CBV with MR-CBV approached significance (tau = 0.39, P =.06). Extent of initial hyperintensity on diffusion-weighted images correlated best with extent of MR-CBV abnormality (tau = 0.69, P =.001), extent of MR-MTT abnormality (tau = 0.67, P =.002), and extent of CT-CBV abnormality (tau = 0.47, P =.02). CONCLUSION: Good correlation was seen between CT and MR for CBF and MTT abnormalities. It remains uncertain whether CT perfusion CBV abnormalities correspond well to whole-brain abnormalities.

Acute Disease↗
PubMed2002

Magnetic resonance imaging with lateralized arterial spin labeling.

We report the development of a new MRI technique which allows spins from right-sided arteries to be labeled separately from spins from left-sided arteries. This method uses two spatially-selective adiabatic inversion pulses to alternate the labeling of the right carotid and vertebral artery separate from the left carotid and vertebral artery. Normal volunteers were scanned on a clinical 1.5 T system and the resultant brain images correlated with the T2 anatomic images. Arterial anatomy was depicted using the new sequence and corresponded to the labeling scheme employed by the sequence. It was demonstrated that spatially selective inversion pulses permit the encoding of the spins within specific vascular origins and the observation of their run-off territory.

Brain↗
PubMed2002

CT perfusion scanning with deconvolution analysis: pilot study in patients with acute middle cerebral artery stroke.

PURPOSE: To measure mean cerebral blood flow (CBF) in ischemic and nonischemic territories and in low-attenuation regions in patients with acute stroke by using deconvolution-derived hemodynamic imaging. MATERIALS AND METHODS: Twelve patients with acute middle cerebral artery stroke and 12 control patients were examined by using single-section computed tomography (CT) perfusion scanning. Analysis was performed with a deconvolution-based algorithm. Comparisons of mean CBF, cerebral blood volume (CBV), and mean transit time (MTT) were determined between hemispheres in all patients and between low- and normal-attenuation regions in patients with acute stroke. Two independent readers examined the images for extent of visually apparent regional perfusion abnormalities. The data were compared with extent of final infarct in seven patients with acute stroke who underwent follow-up CT or magnetic resonance imaging. RESULTS: Significant decreases in CBF (-50%, P =.001) were found in the affected hemispheres of patients with acute stroke. Significant changes in CBV (-26%, P =.03) and MTT (+111%, P =.004) were also seen. Significant alterations in perfusion were also seen in low- compared with normal-attenuation areas. Pearson correlation between readers for extent of CBF abnormality was 0.94 (P =.001). Intraobserver variation was 8.9% for CBF abnormalities. CONCLUSION: Deconvolution analysis of CT perfusion data is a promising method for evaluation of cerebral hemodynamics in patients with acute stroke.

Adult↗
PubMed2002

Contrast-enhanced magnetic resonance angiography of carotid arteries: utility in routine clinical practice.

BACKGROUND AND PURPOSE: Contrast-enhanced magnetic resonance angiography (CEMRA) is among the newer noninvasive tests used for the evaluation of patients with carotid artery disease. Evidence supporting its utility in routine clinical practice is lacking. METHODS: The results of CEMRA were compared with those of catheter angiography in 50 consecutive patients being evaluated for carotid endarterectomy (CEA) at a community hospital. Using indications for CEA based on published guidelines, we determined the rate of misclassification for surgery, sensitivity, specificity, and positive and negative predictive values. In addition, the interrater agreement (kappa score) of CEMRA was compared with that of catheter angiography in the studied population and with interpretations provided by 2 blinded radiologists. RESULTS: Compared with catheter angiography, 24% (95% CI, 12% to 36%) of patients would have been misclassified for CEA on the basis of CEMRA results alone. CEMRA was associated with sensitivity of 92%, specificity of 62%, positive predictive value of 78%, and negative predictive value of 89%. When both CEMRA and duplex Doppler ultrasound were performed and the results were concordant, the misclassification rate decreased to 17% (95% CI, 2% to 32%). kappa scores were similar for CEMRA and catheter angiography (0.72 and 0.75, respectively). CONCLUSIONS: CEMRA was found to be highly sensitive for detection of surgically amenable carotid stenosis. kappa scores for the interpretation of CEMRA and catheter angiography were similar. However, clinicians should be cautious when using CEMRA alone for surgical decision making in CEA candidates because a significant number of patients may be misclassified. The rate of misclassification is reduced when the results of CEMRA and duplex Doppler ultrasound are concordant.

Adult↗
PubMed2002

Dynamic CT perfusion imaging with acetazolamide challenge for the preprocedural evaluation of a patient with symptomatic middle cerebral artery occlusive disease.

We describe the use of a CT-based method of cerebral perfusion imaging, dynamic CT perfusion imaging, for the pre- and postprocedural assessment of cerebral blood flow in a patient with symptomatic middle cerebral artery occlusive disease who underwent balloon angioplasty with stent placement in the affected artery. Dynamic CT perfusion imaging represents a widely available and minimally invasive alternative to other available methods of cerebral perfusion imaging.

Acetazolamide↗
PubMed2002

Diffusion-weighted imaging in a patient with vertebral and epidural abscesses.

In this report, we describe the appearance of the spinal vertebral body and epidural abscesses in a patient who underwent diffusion-weighted imaging of the spine and CT-guided aspiration of one of the abscesses. The abscesses were hyperintense relative to the surrounding tissues on diffusion-weighted images, and they appeared dark on apparent diffusion coefficient maps; these findings were consistent with those of published reports of the brain and liver.

Aged↗