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S Ekholm

Publications and source records attributed to S Ekholm.

At least 37 records · Page 2Linked to original sources
PubMed1998

Signal profile measurements of single- and double-volume acquisitions with image-selected in vivo spectroscopy for 31P magnetic resonance spectroscopy.

The volume-selection performance was studied for single- and double-volume-of-interest (VOI) acquisition with the volume-selection method image-selected in vivo spectroscopy for 31P magnetic resonance spectroscopy. High-resolution signal profiles were measured using a phantom simulating a brain. Inside the phantom there was a small, remotely controlled, movable signal source filled with ortho-phosphoric acid. Signal profiles of the VOI were measured in three perpendicular directions for 1VOI (single VOI) and 2VOI (double VOI) acquisition. The measured signal profiles for both acquisitions were very similar, but they showed a discrepancy with regard to the intended VOI (iVOI). The transition regions were on average 3.8 mm and the average full width at half maximum of the signal profile was 30 mm for an iVOI size of 30*30*30 (mm3). No displacement was observed in the signal profiles. To avoid overlapping signal profiles, the minimum separation between two iVOIs was found to be 10 mm in our magnetic resonance (MR) system. A substantial negative signal contribution from regions outside the iVOI was measured in the y-direction for 1VOI acquisition and one of the two VOIs in 2VOI acquisition. The other VOI in 2VOI acquisition exhibited only minor contamination. The measurements presented underline the importance of detailed knowledge on the volume selection performance in in vivo magnetic resonance spectroscopy.

Brain↗
PubMed1998

Localization of the brain lesion affects the lateralization of T-lymphocyte dependent cutaneous inflammation. Evidence for an immunoregulatory role of the right frontal cortex-putamen region.

We have previously demonstrated that brain lesions caused by stroke led to the lateralization of T-cell dependent inflammation. The purpose of this study was to assess the impact of localization of the brain lesion on lateralization of immune responsiveness. The delayed-type hypersensitivity (DTH) reaction was used as an in vivo measure of antigen specific T-lymphocyte reactivity. All stroke patients were examined with computed scan tomography (CT) of the brain to ascertain the localization and extent of the brain lesion. Patients with right-sided brain lesions displayed significantly larger (P = 0.008) DTH responses on the paretic side compared to the contralateral side. Detailed analysis of the localization of the brain lesion revealed that infarcts encompassing frontal lobe-putamen led to significantly larger (P = 0.007) DTH responses on the paretic side compared to the contralateral side. Localization of the brain lesion affects the lateralization of DTH, supporting an asymmetrical modulation of the immune response. In addition, our study points to the frontal cortex-putamen as a putative brain centre regulating the magnitude of immune responses.

Adult↗
PubMed1998

Nonlateralized attentional deficits: an important component behind persisting visuospatial neglect?

Simple reaction time was examined in a consecutive series of 60 right hemisphere stroke patients at the postacute stage and at 6 to 7 months poststroke. Reaction times to auditory stimuli were measured within the ipsilesional side of space. Patients showing contralateral neglect in conventional tests of neglect showed significantly increased reaction times at the postacute stage and at the follow-up compared to those not showing neglect and to those in a group of normal controls. The results suggest that a lowered general attentional capacity may constitute a central component behind persistent neglect. An additional analysis of the CT scans of the patients showed that a large lesion including the paraventricular white matter in the temporal lobe was the most important anatomical correlate of persisting slow reactions.

Adult↗
PubMed1998

Radiation dose reduction in CT: application to tissue area and volume determination.

PURPOSE: To study the potential for radiation dose reduction in computed tomographic (CT) determination of adipose and muscle tissue area and volume, which is an application in which lower spatial resolution or higher image noise can be accepted. MATERIALS AND METHODS: Measurements in vivo (in a healthy man aged 52 years; weight, 80 kg) and in phantoms were performed with two standard clinical CT scanners. Tissue areas were determined, and measurement uncertainties were analyzed. Comparisons were made with simulated and theoretic data. RESULTS: A 25-fold reduction in radiation dose was achieved and resulted in an effective dose of 13 microSv per section; an accuracy of greater than 5% in area measurements was maintained. The dose savings achieved in this study were close to those that are theoretically possible. CONCLUSION: Further dose reduction to about 1 microSv may be possible for this application. Large dose reductions are possible in CT determinations of tissue area and volume, which makes this application available also in large randomized studies in which high-performance clinical standard scanners are used. This work demonstrates that modern CT technology may have a large potential for dose reduction in specific applications.

Adipose Tissue↗
PubMed1997

Anatomical and neurological correlates of acute and chronic visuospatial neglect following right hemisphere stroke.

Anatomical and neurological correlates of visuospatial neglect were studied in 53 patients with a CT-documented right hemisphere stroke. Evidence of neglect at the acute stage poststroke was strongly related to large lesions involving the middle temporal gyrus and/or the temporo-parietal paraventricular white matter. Thus, out of 18 patients with evidence of visuospatial neglect at the acute stage, 12 showed a lesion in the middle temporal gyrus and/or the deep temporo-parietal white matter. Among the 35 patients that failed to show visuospatial neglect, only one patient had a lesion within these areas. Comparing those patients who recovered from neglect with those that did not, a high correlation was found between persisting neglect and a lesion involving the paraventricular white matter in the temporal lobe. On the basis of above findings, it was suggested that a simultaneous damage to the cortico-thalamic system for regulation of arousal and to the neural systems mediating visual orienting, is likely to be followed by persisting neglect symptoms.

Adult↗
PubMed1997

Intrathecal release of pro- and anti-inflammatory cytokines during stroke.

A growing body of evidence points out the potential role of inflammatory mechanisms in the pathophysiology of ischaemic brain damage. We have recently demonstrated that stroke patients display an intrathecal production of proinflammatory cytokines, such as IL-1beta and IL-6 already within the first 24 h after the beginning of symptoms (Tarkowski et al., 1995). The aim of the present study was to investigate patterns of local inflammatory responses as a consequence of acute stroke. Thirty stroke patients were studied prospectively on days 0-3, 7-9, 21-26 and after day 90 with clinical evaluations, radiological assessments and analysis of cerebrospinal fluid (CSF) cytokine levels. In addition, 15 healthy control CSF samples were used. Significantly increased CSF levels of IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-10 were observed early during the stroke with a peak on day 2 for the proinflammatory cytokines IL-8 and GM-CSF, and on day 3 for the immunoregulatory cytokine IL-10. Patients with a brain infarct predominantly located in the white matter showed significantly higher levels of IL-8 in CSF than patients with an infarct mainly located in the grey matter. Also, high levels of intrathecal tumour necrosis factor-alpha (TNF-alpha) were associated with the presence of white matter disease. Our study demonstrates an intrathecal production of proinflammatory and immunoregulatory cytokines in patients with stroke, supporting the notion of localized immune response to the acute brain lesion. A better understanding of the inflammatory response in stroke may lead to new treatment strategies.

Adult↗
PubMed1997

Diagnostic efficacy of MnDPDP in MR imaging of the liver. A phase III multicentre study.

PURPOSE: To assess the diagnostic efficacy, safety and tolerability of mangafodipir trisodium (MnDPDP, Teslascan) in MR imaging of the liver. MATERIAL AND METHODS: Eighty-two patients from 4 centres underwent MR imaging with pre-contrast sequences including T1-weighted SE and GRE, and T2-weighted turbo SE sequences. MnDPDP at a dose of 5 mumol/kg b.w. was administered by slow i.v. infusion, and 20-60 min after infusion the T1-weighted SE and GRE sequences were repeated. Diagnostic efficacy was evaluated by counting the number of lesions and by evaluating whether more information for lesion characterisation was available in post-contrast images. Safety and tolerability were assessed by recording adverse events and infusion-related discomfort. RESULTS: Significantly more lesions were found in MnDPDP-enhanced T1-weighted SE and GRE images than in unenhanced images of the same sequences. More lesions were also found in these images compared with T2-weighted images at a level of marginal significance. More information was obtained from MnDPDP-enhanced images in 40 cases. Mild to moderate adverse events were experienced by 17% of the patients. CONCLUSION: MnDPDP-enhanced images can improve lesion detection in the liver and are helpful for lesion characterisation. To obtain optimal diagnostic information of liver lesions T2-weighted images are also valuable. MnDPDP is a safe contrast agent for MR imaging of liver lesions.

Adult↗
PubMed1997

A new set of fiducial markers for MRI, CT and SPET alignment.

A set of fiducial markers for use in the alignment of MR, CT and SPET images is presented. The marker system consists of individually produced imprints of the external auditory meatus, a pair of plastic spectacle frames and three fiducial markers. The markers are filled with a suitable contrast agent, fixed into the imprints and screwed onto the spectacle frame just before examination. The reproducibility in positioning the marker system on the patient was evaluated by repeated MRI examinations of a volunteer. The fiducial markers could be repositioned with an accuracy of less than +/- 1.6 mm in the left-right and anterio-posterior directions and +/- 1.9 mm in the cranio-caudal direction (95% confidence interval). The marker system is inexpensive and easy to produce, taking less than 20 min to produce on the ward. Only a few minutes are required to fix the system prior to examination. It is comfortable for the patient, even during long examinations. In cases lacking visible intrinsic structures and external contours, fiducial markers provide a good means of alignment for image fusion. The marker system described here for the alignment of SPET, CT and MR images can be used on a routine basis without the invasive fixation of fiducial markers.

Brain↗
PubMed1996

Disorders of the cerebral white matter in children. The spectrum of lesions.

The use of magnetic resonance imaging (MRI) has resulted in the detection of an increasing number of children with an apparently leukodystrophic white matter. Laboratory tests and the clinical presentation, however, often do not correspond to any known entity and the course is sometimes not progressively deteriorating. Such children with white-matter changes and no known diagnosis were the subject of this Swedish multicentre study, in which MRI findings and clinical data from 100 children considered to have white-matter abnormalities were assessed during the period 1992-1995. At re-evaluation of MR images by an established "white-matter group" of neuroradiologists, paediatric neurologists, neurologists and neurochemists, the MRI signal of the white matter was considered normal in eleven children and eleven had mainly a grey matter affection. Of the remaining 78 children with white matter abnormalities, a diagnosis was found in 32, but in 46 children no diagnosis could be established. A progressive downhill course characterised 17, probably representing hitherto undefined types of leukodystrophies. Five children had a relapsing-remitting course, and in 11 it was difficult to establish whether the course was progressive or stationary. The disease was non-progressive in 13. This group of non-leukodystrophic white-matter changes obviously represents maldevelopments of myelin formation, thus dys- or hypomyelination rather than demyelination.

Adolescent↗
PubMed1996

Analysis of interobserver disagreement in the assessment of subarachnoid blood and acute hydrocephalus on CT scans.

The purpose of this study was to analyse factors for interobserver disagreements in two scales used for the assessments of the amount of blood in subarachnoid space (Fisher grading) and of acute hydrocephalus on computerized tomographic (CT) scans. The assessments made by four neuroradiologists on 59 CT scans obtained in the acute stage after subarachnoid hemorrhage were analysed by a statistical method by Svensson and Holm. This method permits the separation of the inter-observer disagreements in their random and systematic components. The overall consistency of the assessments was significant (p < 0.0005) but the neuroradiologists disagreed on half of the CT-scans. The kappa values were 0.50-0.63. The analysis showed that the main reason for disagreements was systematic inter-observer differences in their use of the clinically most important parts of staging, i.e. subarachnoid clot or intraventricular blood (Fisher grading) and too low categories (hydrocephalus). The main conclusion from this study is that the proper remedy for Fisher grading and for grading of hydrocephalus is a sharpening of the criteria of specific category levels and given this improvement both grading systems will show a high level of reliability.

Data Interpretation, Statistical↗
PubMed1996

Tolerance and efficacy of Omniscan (gadodiamide injection) in MR imaging of the central nervous system.

PURPOSE: This Swedish multicenter trial was performed on patients with known or suspected lesions of the CNS for which an MR examination using a contrast medium was indicated. A total of 8 MR centers participated in the study to establish the safety and efficacy of Omniscan (gadodiamide injection) in clinical routine using a standard dose of 0.1 mmol Gd/kg b.w. MATERIAL AND METHODS: Seven hundred adult patients who had been referred for MR investigation of suspected CNS lesions were included in the study. Since most patients were examined on an outpatient basis, it was decided to use an explicit questionnaire regarding adverse events that developed within 24 h after examination. The efficacy evaluation involved comparisons of detectability, delineation, and number of lesions before and after injection of Omniscan. RESULTS: No serious or unexpected adverse event was found. There were a total of 70 (10.2%) patients with adverse events, excluding those judged not to be contrast media-related. However, only 15 patients (2.2%) had adverse events that possibly or probably were related to the contrast medium. Usually, the symptoms were headache, dizziness, abnormal taste, and nausea. Two patients complained of itching, but only one developed urticaria. The efficacy was similar to that of other currently used Gd-based MR agents. Lesions were more often seen on T2-weighted images, but the contrast medium improved lesion delineation, contributing to higher certainty in diagnosis, and provided more confidence in excluding suspected abnormality. CONCLUSION: Omniscan was found to be a safe and clinically valuable contrast medium for MR imaging of the CNS.

Adolescent↗
PubMed1996

Phosphorus-31 MR spectroscopy in the preoperative evaluation of symptomatic unilateral carotid artery stenosis.

PURPOSE: The purpose of this study was to examine the potential of 31P-MRS (MR spectroscopy) in the pre- and postoperative evaluation of patients referred for endarterectomy. MATERIAL AND METHODS: Nine patients with unilateral, hemodynamically significant stenosis in the region of the common carotid bifurcation were examined pre- and post-operatively with CT, SPECT (regional cerebral blood flow), transcranial Doppler, and duplex sonography, and they also underwent neuropsychologic investigation. Phosphorus-31 MRS of each hemisphere was performed before and 27-148 days after surgery. The relative concentrations of phosphomono- and -diesters, inorganic phosphate, phosphocreatine, and ATP were estimated. RESULTS: No definite changes in concentrations could be detected for any of the metabolites. CONCLUSION: The lack of changes was probably due to well-functioning collaterals and to the partial volume effect, whereby changes in a focal region are hidden when larger volumes are studied.

Aged↗
PubMed1996

Linomide reduces the rate of active lesions in relapsing-remitting multiple sclerosis.

The synthetic immunomodulator Linomide, a quinoline-3-carboxamide, has a profound inhibitory influence in several experimental autoimmune diseases, including acute and chronic experimental allergic encephalomyelitis. In a double-blind trial, 31 patients with relapsing-remitting multiple sclerosis were randomized to oral doses of 2.5 mg Linomide or placebo once a day for six months. Fourteen patients receiving Linomide and 14 receiving placebo completed the trial, and the results were based on this population. The mean number of active (new and enlarged T2 weighted) lesions per monthly MRI scan was 1.37 in the patients receiving Linomide and 4.22 in the patients receiving placebo (p = 0.043). The percentage of scans with active MRI lesions was lower in the Linomide-treated group (p = 0.0064). When neurologic deficit was assessed by the Regional Functional Scoring System (RFSS), the Linomide group showed an improvement of 1% of the maximal RFSS range and the placebo group a deterioration of 0.2% (p = 0.14). There were three patients with relapses in the Linomide-treated group and six in the placebo group (p = 0.22). A slightly decreased proportion of natural killer cells in cerebrospinal fluid and peripheral blood was noted in the Linomide group. A severe adverse event of pleuropericarditis occurred in one of the Linomide-treated patients. The most frequent adverse event was musculoskeletal pain, of mild to severe degree, which tended to diminish after three months on Linomide therapy.

Adjuvants, Immunologic↗
PubMed1995

Signal profile measurements for evaluation of the volume-selection performance of ISIS.

High-resolution signal profiles obtained with a test phantom were used in this study to evaluate the volume-selection performance of an implementation of ISIS (Image Selected In vivo Spectroscopy). The phantom simulated the brain with regard to volume and loading of coil. A remotely controlled, movable signal source inside the phantom was filled with orthophosphoric acid. Signal profiles of the volume of interest (VOI) were measured in three perpendicular directions. Special interest was focused on the transition zones, the position of the profiles, and the effects of off-resonance and T1 smearing. The transition zones were on average 5.6 mm wide and the full width at half maximum (FWHM) was 35 mm for a VOI of 40 x 40 x 40 mm3. The positions of the centre of the signal profiles were x = 3.2, y = -0.7 and z = 3.3 mm off-centre. The deviation of the volume position could be explained by off-resonance effects during imaging and spectroscopy. These data illustrate the importance of detailed knowledge of the volume-selection performance when attempting precision measurements using image-guided in vivo MRS.

Brain↗
PubMed1995

Autonomic and thermal sensory symptoms and dysfunction after stroke.

BACKGROUND AND PURPOSE: Symptoms interpreted as unilateral disturbances of autonomic function, such as coldness, dryness, sweating, and trophic changes, are well known but incompletely understood clinical problems after stroke. The present study provides data related to the incidence and mechanisms behind such symptoms. METHODS: Temperature perception thresholds, skin temperatures, evaporation rates, and skin blood flow responses were measured bilaterally in 37 stroke patients aged 58 +/- 13 years (mean +/- SD) and in a control group of 15 patients aged 64 +/- 15 years with a single transient ischemic attack. RESULTS: Of the 37 stroke patients, 43% reported a sensation of coldness in the contralesional side of the body. Basal skin blood flow and temperature were relatively lower in the contralesional side. There was an excess of evaporation in the contralesional side after brain stem lesions and in the ipsilesional side after hemispheric lesions. Vasomotor reflex asymmetries occurred in 34% of the patients and were due to weak vasodilator or vasoconstrictor reflexes in the ipsilesional side. These abnormalities correlated significantly to sensations of unilateral coldness, hypalgesia, and thermohypesthesia in the contralesional side and anatomically to lesions in spinothalamo-cortical pathways. CONCLUSIONS: Focal central nervous system lesions due to stroke may result in symptoms and measurable evidence of unilateral disturbance of skin sympathetic function. Vasomotor asymmetries are probably due to lesions of vasomotor pathways descending uncrossed. Subjective coldness may be due to disturbed central processing.

Aged↗
PubMed1995

Early intrathecal production of interleukin-6 predicts the size of brain lesion in stroke.

BACKGROUND AND PURPOSE: We have previously demonstrated that stroke influences systemic immune responses. The aim of the present study was to investigate patterns of local inflammatory response as a consequence of acute stroke. METHODS: Thirty stroke patients were studied prospectively on days 0 to 3, 7 to 9, 21 to 26, and after day 90 with clinical evaluations, radiological assessments, and analysis of serum and cerebrospinal fluid cytokine levels. RESULTS: Significantly increased levels of interleukin-6 (IL-6) in cerebrospinal fluid (P < .001) were observed in virtually all patients studied compared with healthy control subjects. This increase was observed during the whole observation period but was significantly more pronounced within the first days after stroke onset, with a peak level on days 2 and 3. This initial increase was significantly correlated (r = .65, P = .002) with the volume of infarct measured by MRI 2 to 3 months later. Serum levels of IL-6 in stroke patients were significantly lower than cerebrospinal fluid levels of IL-6 (P = .013) and did not display any significant correlation to the size of the brain lesion. Also, increase in intrathecal but not systemic production of IL-1 beta was observed early during the stroke. Only minor increases of cerebrospinal fluid interferon-gamma levels were observed in two patients. CONCLUSIONS: Our study demonstrates an intrathecal production of IL-6 and IL-1 beta in patients with stroke, supporting the notion of localized inflammatory response to acute brain lesion. In addition, the significant correlation between early intrathecal production of IL-6 and the subsequent size of the brain lesion can be used as a prognostic tool, predicting the size of the brain damage before it is possible to accurately visualize it with radiological methods.

Adult↗
PubMed1995

Evaluation of volume selection methods in in vivo MRS. Design of a new test phantom.

In vivo MR spectroscopy (MRS) requires some kind of volume selection method to be able to measure the signal from a selected part of the body. To be able to interpret the spectra correctly, the quality of the volume selection must be investigated for each new MRS application using phantom measurements. A new phantom, especially suitable for precision measurements of the volume selection performance, is presented. It contains a small, remotely controlled signal source placed inside a larger vessel. This principle can be applied to various body regions, coil types and nuclei. The measurement conditions are close to the clinical situation. The phantom does not have to be repositioned during a signal profile measurement and the signal contribution from each point along the profile is determined regarding sign and amplitude.

Brain↗