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C R Jack

Publications and source records attributed to C R Jack.

At least 55 records · Page 3Linked to original sources
PubMed1998

Mapping of the central sulcus with functional MR: active versus passive activation tasks.

PURPOSE: Our purpose was to assess the pattern of functional MR activation obtained with a passive sensory versus an active sensorimotor hand stimulus paradigm. METHODS: Eight functional MR runs, four with an active sensorimotor (sponge-squeezing) task and four with a passive sensory (palm-finger brushing) reception, were acquired for each of 10 healthy volunteers. Activation maps were generated by thresholding cross-correlation maps. Regions of interests (ROIs) were drawn around the precentral and postcentral gyri on T1-weighted images according to established anatomic criteria, and the number of activated pixels inside the ROIs was ascertained. Displacement of the sensorimotor and sensory activation centroids within the ROIs from the central sulcus as well as from each other was measured. RESULTS: Active sensorimotor stimulation produced a significantly greater number of activation pixels than did passive sensory stimulation. Run-to-run variability was equivalent between sensorimotor and sensory activation tasks. On average, the sensorimotor and sensory activation centroids were located in the postcentral gyrus, and their spatial locations were not significantly different. CONCLUSION: Active and passive activation tasks produce largely equivalent results. Presurgical mapping of the sensorimotor area can be performed with functional MR imaging using a passive palm-finger brushing task in patients who are physically unable to perform active finger-tapping or hand-squeezing sensorimotor activation tasks.

Adult↗
PubMed1998

Real-time reconstruction and high-speed processing in functional MR imaging.

Access to fully processed activation maps in near real time during a functional MR examination enables run-to-run assessment of results. This is particularly useful in clinical studies, since the results of the functional MR examination can be ascertained before the patient leaves the MR suite, permitting interactive tailoring of the functional MR study. We describe how a real-time MR system can be customized to complete the following tasks in less than 3 minutes: obtain an 81-second acquisition of a multisection functional MR imaging time series using single-shot echo-planar imaging, perform image reconstruction, extract functional MR activation maps using cross-correlation and thresholding, and superimpose activation maps on previously acquired T1-weighted anatomic images.

Algorithms↗
PubMed1997

Volumetric magnetic resonance imaging. Clinical applications and contributions to the understanding of temporal lobe epilepsy.

In recent years, magnetic resonance imaging-based volumetric measurements of the amygdala and hippocampus have proved useful in the diagnosis and treatment of patients with temporal lobe epilepsy. This imaging modality allows amygdaloid and hippocampal volumes to be correlated with neurophysiological, neuropathological, and neuropsychological findings, surgical outcome, and clinical findings. We evaluated the technical and anatomical aspects underlying the successful use of the modality that were reported in previous studies. We also evaluated issues such as the sensitivity and specificity of volumetric magnetic resonance imaging, its use in bilateral temporal lobe epilepsy, and the debate concerning the sensitivity of qualitative visual analysis vs quantitative volumetric analysis of magnetic resonance images. Volumetric magnetic resonance imaging, when used in conjunction with video electroencephalographic monitoring, neuropsychological studies, and other neuroimaging studies, will enable patients with temporal lobe epilepsy to be treated in an appropriate, efficient, and cost-effective manner.

Amygdala↗
PubMed1997

Hippocampal transverse relaxation times in patients with Alzheimer disease.

PURPOSE: To determine whether hippocampal relaxation times in magnetic resonance (MR) imaging differ between patients with probable Alzheimer disease and elderly control subjects with normal cognition. MATERIALS AND METHODS: MR imaging relaxation times were measured in the head and body of the right and left hippocampi in 123 subjects: 62 patients with Alzheimer disease (44 women, 18 men; age range, 65-89 years) and 61 elderly control subjects without cognitive impairment (39 women, 22 men; age range, 65-89 years). Hippocampal relaxation times were correlated with clinical status (patient vs control subject), age, sex, laterality (right vs left), and location within the hippocampus (body vs head). The hippocampal T2 value was correlated with the severity of disease in the patients. RESULTS: No statistically significant difference in the relaxation times was found between the two clinical groups for the analysis of the right versus left hippocampi and the hippocampal head versus body. In both patients and control subjects, no correlation was found between T2 measurements and age or sex. Twenty-seven patients had a clinical dementia rating (CDR) score of 0.5 (very mild dementia), 21 patients had a CDR score of 1.0 (mild dementia), and eight patients had a CDR score of 2.0 (moderate dementia). The CDR score was not available in six patients. No statistically significant association between T2 values and severity of disease was observed. CONCLUSION: MR relaxation time measurements in the hippocampus are not useful for the detection of Alzheimer disease.

Aged↗
PubMed1997

Medial temporal atrophy on MRI in normal aging and very mild Alzheimer's disease.

Magnetic resonance imaging (MRI)-based volumetric measurements of medial temporal lobe (MTL) structures can discriminate between normal elderly control subjects and patients with Alzheimer's disease (AD) of moderate to advanced severity. In terms of clinical utility, however, a more important issue concerns the ability of the technique to differentiate between normal elderly control subjects and AD patients with the very mildest form of the disease. We performed MRI-based volumetric measurements of the hippocampus, parahippocampal gyrus, and amygdala in 126 cognitively normal elderly control subjects and 94 patients with probable AD. The diagnosis of AD was made according to NINDS/ADRDA criteria, and disease severity was categorized by Clinical Dementia Rating (CDR) scores. Patients with CDR 0.5 were classified as very mild, CDR 1 as mild, and CDR 2 as moderate disease severity. Volumes of each structure declined with increasing age in control subjects and did so in parallel for men and women. The volume of each measured MTL structure also declined with age in patients with AD. The volume of each MTL structure was significantly smaller in AD patients than control subjects (p < 0.001). Of the several MTL measures, the total hippocampal volumetric measurements were best at discriminating control subjects from AD patients. The mean hippocampal volumes for AD patients relative to control subjects by severity of disease were as follows: very mild AD (CDR 0.5) -1.75 SD below the control mean, mild AD (CDR 1) -1.99 SD, and moderate AD (CDR 2) -2.22 SD. Age- and gender-adjusted, normalized MRI-based hippocampal volumetric measurements provide a sensitive marker of the MTL neuroanatomic degeneration in AD early in the disease process.

Aging↗
PubMed1996

Real-time adaptive motion correction in functional MRI.

Functional magnetic resonance imaging (fMRI) of the brain is often degraded by bulk head motion. Algorithms that address this by retrospective re-registration of images in an fMRI time series are all fundamentally limited by any motion that occurs through-plane. Here, a technique is described that can account for such motion by prospective correction in real time. A navigator echo is used before every image acquisition to detect superior/inferior displacements of the head. The displacement information is then used to adjust the plane of excitation of the ensuing single-shot echo-planar fMRI axial image. These correction updates can be completed in 100 mm with motion sensitivity at least as small as 0.5 mm. The efficacy of this method is documented in phantom and human studies.

Brain↗
PubMed1996

Dynamic MR digital subtraction angiography using contrast enhancement, fast data acquisition, and complex subtraction.

A dynamic MR angiography technique, MR digital subtraction angiography (MR DSA), is proposed using fast acquisition, contrast enhancement, and complex subtraction. When a bolus of contrast is injected into a patient, data acquisition begins, dynamically acquiring a thick slab using a fast gradient echo sequence for 10-100 s. Similar to x-ray DSA, a mask is selected from the images without contrast enhancement, and later images are subtracted from the mask to generate angiograms. Complex subtraction is used to overcome the partial volume effects related to the phase difference between the flowing and stationary magnetization in a voxel. Vessel signal is the enhancement of flow magnetization resulting from the contrast bolus. MR DSA was performed in 28 patients, including vessels in the lungs, brains, legs, abdomen, and pelvis. All targeted vessels were well depicted with MR DSA. Corresponding dynamic information (contrast arrival time ta and duration of the arterial phase tav) was measured: ta/tav = 3.4/4.7 s for the lung, 10.3/4.9 s for the brain, 12.8/19.3 for the aorta, 15.2/12.6 s for the leg. MR DSA can provide dynamic angiographic images using a very short acquisition time.

Abdomen↗
PubMed1996

Magnetic resonance imaging in epilepsy.

The magnetic resonance imaging (MRI) appearance of the various histologic substrates of epilepsy and the clinical role of MRI in symptomatic epilepsy are reviewed. MRI is used clinically to identify potential surgical candidates among patients with epilepsy, assist in surgical planning, and help to determine the prognosis of patients with epileptic seizures. MRI can clearly characterize the morphologic substrates that underlie the electroclinical abnormalities noted in patients with epilepsy. The histologic substrates of symptomatic epilepsy can be divided into five major categories: tumors, disorders of neuronal migration and cortical organization, vascular malformations, mesial temporal sclerosis, and neocortical sclerosis attributable to brain injury (trauma, infection, inflammation, or infarction). Because of its ability to disclose subtle alterations in cortical architecture or changes in signal intensity, MRI is the most sensitive and specific imaging technique for the noninvasive identification of each of these substrates. Introduction of MRI into clinical practice during the past 10 years has substantially changed the management of patients with epilepsy.

Brain↗
PubMed1996

Bilateral magnetic resonance imaging-determined hippocampal atrophy and verbal memory before and after temporal lobectomy.

We investigated pre- and postoperative verbal memory in temporal lobectomy patients who had volumetrically symmetric hippocampi. Pre- and postoperative verbal memory data based on the Logical Memory subtest of the Wechsler Memory Scale-Revised (WMS-R) were obtained from 15 left and 18 right temporal lobectomy patients. The difference between hippocampal volumes (R/L) was between -0.1 and 0.3 cm3, which is indeterminate for lateralizing hippocampal atrophy. Patients were divided into four groups based on side of operation and combined hippocampal volume expressed as a function of total intracranial volume (R + L volume/total intracranial volume). Patients with a combined hippocampal volume that was smaller than any combined hippocampal value of a normal control group were defined as bilaterally atrophic. Left temporal lobectomy patients demonstrated the expected decrease in verbal memory postoperatively regardless of whether the volumetrically symmetric hippocampi were nonatrophic or atrophic. Left temporal lobectomy patients with bilaterally atrophic hippocampi, however, had the poorest verbal memory before and after operation. Right temporal lobectomy patients tended to have improved verbal memory after operation whether or not the volumetrically symmetric hippocampi were atrophic. We conclude that side of operation is a more potent predictor of verbal memory outcome than is hippocampal atrophy when hippocampi are bilaterally symmetric and that left temporal lobectomy patients with bilateral atrophy may be at risk for greater functional deficits after operation.

Adult↗
PubMed1996

Routine EEG and temporal lobe epilepsy: relation to long-term EEG monitoring, quantitative MRI, and operative outcome.

PURPOSE: To investigate the relation among routine EEG, long-term EEG monitoring (LTM), quantitative magnetic resonance imaging (MRI), and surgical outcome in temporal lobe epilepsy (TLE). METHODS: We evaluated 159 patients with intractable TLE who underwent an anterior temporal lobectomy between 1988 and 1993. The epileptogenic temporal lobe was determined by ictal LTM. A single awake-sleep outpatient EEG with standard activating procedures was performed before LTM. EEGs were analyzed by a blinded investigator. RESULTS: MRI scans showed unilateral medial temporal atrophy (109 patients) or symmetrical hippocampal volumes (50 patients). The surgically excised epileptogenic brain tissue revealed mesial temporal sclerosis, gliosis, or no histopathologic alteration. Routine EEG revealed temporal lobe epileptiform discharges in 123 patients. Routine EEG findings correlated with the temporal lobe of seizure origin (p < 0.0001) and the results of MRI volumetric studies (p < 0.0001). Interictal epileptiform discharges were seen only during LTM in 24 patients. Routine EEG was disconcordant with interictal LTM in another 20 patients. MRI-identified unilateral medial temporal lobe atrophy was a strong predictor of operative success (p < 0.0001). There was no significant relation between the routine EEG findings and operative outcome (p > 0.20). CONCLUSIONS: Results of this study modified our approach in patients with TLE. Interictal epileptiform discharges localized to one temporal lobe on serial routine EEGs or during LTM may be adequate to identify the epileptogenic zone in patients with MRI-identified unilateral medial temporal lobe atrophy.

Adolescent↗
PubMed1996

Coronary artery bypass grafting-associated ischemic stroke. A clinical and neuroradiological study.

Ischemic stroke occurring after coronary artery bypass grafting (CABG) has been attributed to various factors. Little is known about the perioperative course and radiological topography of CABG-associated strokes. In this study the clinical and computed tomography features of 25 patients with ischemic stroke following coronary artery bypass grafting were evaluated. Four patients awakened with focal signs, and 21 developed an ischemic stroke 1 to 22 days after surgery. All 4 patients with early stroke had prolonged episodes of operative hypotension. Three of these patients had multiple subcortical and cortical infarcts. Of the 21 patients with late-onset ischemic stroke, 19 had single-territory infarcts (middle cerebral artery territory, N = 12; posterior cerebral artery territory, N = 4; anterior cerebral artery territory, N = 3). Two patients had multiple territory infarcts in the anterior and posterior circulation. No watershed infarcts were found in any of the 25 patients. New-onset atrial fibrillation and location of ischemic stroke in a single vascular territory were more common in patients who had an ischemic stroke after an asymptomatic interval. Duplex sonographic findings of the carotid arteries and oculoplethysmography (OPG) were available for 13 patients. Only 1 patient had an ipsilateral carotid stenosis. Of 21 patients who underwent postoperative two-dimensional echocardiography (with additional transesophageal echocardiography in 4), 2 had a left ventricular thrombus. These findings support the concept that post-CABG stroke is likely embolic.

Aged↗
PubMed1996

Mesial temporal sclerosis: diagnosis with fluid-attenuated inversion-recovery versus spin-echo MR imaging.

PURPOSE: To compare the accuracy of a fluid-attenuated inversion-recovery (FLAIR) sequence with that of a conventional double spin-echo (SE) sequence in the identification of increased signal intensity of the hippocampus in mesial temporal sclerosis (MTS). MATERIALS AND METHODS: Three blinded reviewers independently graded the FLAIR and SE images in 36 patients with intractable complex partial seizures. Reproducibility was tested. At histopathologic examination, the criterion standard, 32 patients had MTS. RESULTS: The accuracy of FLAIR images was 97% versus 91% for SE images (P<.02). The radiologists preferred the contrast properties of FLAIR to those of SE images by a significant margin (P<.0001). Surgical to nonsurgical hippocampal contrast-to-noise ratio (C/N) measurements were better for the second echo of the SE sequence than for FLAIR (P<.002). Hippocampus-to-background tissue C/N was superior with FLAIR (P<.0001). CONCLUSION: FLAIR provides images with T2-weighted contrast and complete suppression of high signal intensity of CSF. Incorporation of a FLAIR sequence into the routine MR evaluation of patients with epilepsy is recommended.

Adult↗
PubMed1996

Traumatic occlusion of one limb of an intracranial arterial fenestration: an uncommon cause of stroke.

Three weeks after an automobile accident, a 35-year-old man experienced left throat and neck pain, numbness of the left face and tongue, dysphagia, left arm pain and weakness, and left miosis. At age 27, he had suffered an aneurysmal subarachnoid hemorrhage. Angiography at that time had also demonstrated a fenestration of the left intracranial vertebral artery. At the time of the second presentation, angiography showed that one of the limbs of the fenestration had become occluded. Although the vast majority of intracranial arterial fenestrations are asymptomatic, occlusion of one of the limbs of a fenestration may be the cause of stroke.

Adult↗
PubMed1996

Use of functional magnetic resonance imaging.

It has been the goal of this article to provide the reader with a brief background of fMRI, a basic understanding of the techniques of fMRI, and, more importantly, the potential for clinical and experimental studies using fMRI. In contrast to the limited number of installed PET and MEG units, the large installed base of MR imaging scanners (over 1000 installed at least at 1.5 T in the United States) makes fMRI potentially widely available. Initial studies (both clinical and experimental) have been validated and are reproducible in mapping the sensorimotor and visual cortices. The areas of language lateralization and memory are still preliminary at best. As methods to reduce the effects of head motion (due to both bulk head motion and physiologically induced motion) arise, the reliability of fMRI should improve, allowing for more definitive identification of task activation.

Brain Diseases↗
PubMed1995

Dual-echo interleaved echo-planar imaging of the brain.

An interleaved echo-planar imaging (EPI) technique is described that provides images from 20 sections of the brain at two echo times (27 and 84 ms) in 1:05. Six echoes per image per repetition are collected in 24 repetitions of the pulse sequence. MR images of the brain obtained from five volunteers using the dual-echo EPI sequence, fast spin-echo (FSE), and conventional dual-echo spin-echo were evaluated qualitatively for diagnostic use and quantitatively for relative signal-to-noise ratio (SNR), contrast, and contrast-to-noise ratios (CNR).

Adipose Tissue↗