Biomedical subjects

S Heiland

Publications and source records attributed to S Heiland.

At least 37 records · Page 2Linked to original sources

PubMed2001

[MR angiography: technical principles and uses in the diagnosis of neurological diseases].

During the last decade, magnetic resonance angiography (MRA) has been incorporated into the routine evaluation of patients with suspected cerebrovascular disease. Although digital subtraction angiography (DSA) is still the gold standard in diagnostics of intracranial vascular disease, it has been replaced by MRA in numerous clinical applications. In this paper we first provide a review of the various MRA techniques. In the second part, the diagnostic value as well as advantages and disadvantages of the different techniques are assessed for various cerebrovascular diseases, such as vessel occlusion, stenosis, dissection, cerebral aneurysms, and spinal and cerebral arteriovenous malformations.

Adult↗

PubMed2001

Perfusion-weighted magnetic resonance imaging in patients with carotid artery disease before and after carotid endarterectomy.

OBJECTIVE: The purpose of this study was to investigate the potential of perfusion-weighted magnetic resonance imaging for preoperative and postoperative evaluation of cerebral hemodynamics in patients undergoing carotid endarterectomy for carotid artery stenosis. METHODS: We examined 26 patients with angiographically proven stenoses (60%-99%) of the internal carotid artery preoperatively. Perfusion imaging studies were performed by bolus-tracking of a dosage of 0.2 mmol/kg body weight of gadolinium diethylenetriaminepentaacetic acid on a 1.5-T scanner using a T2*-weighted fast low-angle shot sequence. The observed signal intensities were converted pixel by pixel into concentration-time curves. In each patient, the hemispheres were compared and the difference between the normalized first moments (NFMs) and the percentage changes of the regional cerebral blood volume (CBV) were calculated. Three months postoperatively, perfusion-weighted magnetic resonance imaging was performed in 13 patients. RESULTS: In patients with <80% stenosis (n = 10), there was no significant alteration of NFM and regional CBV compared with the contralateral hemisphere (-0.16 +/- 0.7 s, +5.9 +/- 24.6%). In patients with stenoses >or=80% (n = 16), we found an increase in NFM ipsilateral to the stenosis of 1.2 +/- 0.92 s (P < .001) and an increase of CBV of 16.8 +/- 15.2% (P < .005). Three months postoperatively, perfusion parameters were normal in all 13 patients examined. CONCLUSIONS: Perfusion-weighted magnetic resonance imaging is well suited to evaluate the preoperative and postoperative hemodynamic changes in patients with carotid artery stenosis. This noninvasive, semiquantitative magnetic resonance technique could prove to be a valuable adjunct in identification of patients who might benefit from carotid endarterectomy.

Adult↗

PubMed2001

Delayed neuroprotective effect of insulin-like growth factor-i after experimental transient focal cerebral ischemia monitored with mri.

BACKGROUND AND PURPOSE: Insulin-like growth factor (IGF) treatment has been shown to have trophic and neuroprotective effects in vitro and in vivo in different lesion models. IGF-I has potent neuroprotective effects after hypoxic-ischemic injury and global ischemia. The role of IGF-I in focal cerebral ischemia is only partially understood. Therefore, in the present study, we evaluated, by applying MRI monitoring, whether a clinically relevant systemic administration of IGF-I can achieve a long-lasting neuroprotective effect. METHODS: Male Wistar rats underwent transient occlusion of the right middle cerebral artery for 1 hour by using the suture occlusion model. Animals then were intraventricularly treated with 33.33 microg IGF-I/d for 3 days (group A, the IGF-I group [n=13]; group B, the placebo group [n=14]) or subcutaneously treated with 200 microg IGF-I/d for 7 days (group D, the IGF-I group [n=10]; group E, the placebo group [n=10]). Groups C and F served as sham-operated controls (n=5 and n=3, respectively). Treatment was begun 30 minutes after occlusion of the middle cerebral artery. Subcutaneously treated animals underwent MRI studies (diffusion-weighted imaging, perfusion imaging, and T2-weighted imaging) beginning 60 minutes after vessel occlusion at 6 hours and at days 1, 2, 5, and 7 after ischemia. The animals were weighed and neurologically assessed daily (rating scale ranged from 0, indicating no deficit, to 5, indicating death). On the third day (intraventricular trial) and on the seventh day (subcutaneous trial), animals were euthanized, and brain sections were stained with triphenyltetrazolium chloride. RESULTS: The mean infarct volume was 52.9+/-25.2 mm(3) in intraventricularly treated animals versus 146.4+/-62.2 mm(3) in control animals (P<0.01) and 42.2+/-17.9 mm(3) in subcutaneously IGF-I-treated animals versus 73.1+/-38.1 mm(3) in control animals (P<0.05). Apparent diffusion coefficient-derived lesion volume at 60 minutes after occlusion was 40.4+/-23.7 mm(3) versus 38.3+/-19.3 mm(3) (P=NS), increased to 168.3+/-49.55 mm(3) versus 105.5+/-33.8 mm(3) (P<0.05) at 24 hours, and then decreased to 55.8+/-30.3 mm(3) versus 23.3+/-20.2 mm(3) (P<0.05) for control and IGF-I-treated animals, respectively. The T2-weighted-derived ischemic lesion volume at 24 hours after occlusion was 236+/-49.2 mm(3) versus 115.9+/-56.8 mm(3) (P<0.05) and decreased to 115.9+/-26.2 mm(3) versus 75.7+/-35.8 mm(3) (P<0.05) at day 7 for control and IGF-I-treated animals, respectively. The relative regional cerebral blood volume was reduced to 50% before reperfusion in all regions of interest except for region of interest 1 (vessel territory of anterior cerebral artery), recovered during reperfusion, but was not different between the control and the growth factor-treated group at any imaging time point. There was no significant difference in weight loss. There was less neurological deficit after ischemia in intraventricularly and subcutaneously IGF-I-treated animals compared with control animals (P<0.05). CONCLUSIONS: Continuous treatment with intraventricularly and subcutaneously administered IGF-I achieved a long-lasting neuroprotective effect as early as 24 hours after ischemia as measured by MRI. Therefore, IGF-I may represent a new approach to the treatment of focal cerebral ischemia.

Animals↗

PubMed2001

Stroke magnetic resonance imaging within 6 hours after onset of hyperacute cerebral ischemia.

We studied the diagnostic and prognostic value of diffusion- and perfusion-weighted magnetic resonancce imaging (DWI and PWI) for the initial evaluation and follow-up monitoring of patients with stroke that had ensued less than 6 hours previously. Further, we examined the role of vessel patency or occlusion and subsequent recanalization or persistent occlusion for further clinical and morphological stroke progression so as to define categories of patients and facilitate treatment decisions. Fifty-one patients underwent stroke magnetic resonance imaging (DWI, PWI, magnetic resonance angiography, and T2-weighted imaging) within 3.3 +/- 1.29 hours, and, of those, 41 underwent follow-up magnetic resonance imaging on day 2 and 28 on day 5. In addition, we assessed clinical scores (on the National Institutes of Health Stroke Scale, Scandinavian Stroke Scale, Barthel Index, and Modified Rankin Scale) on days 1, 2, 5, 30, and 90 and performed volumetric analysis of lesion volumes. In all, 25 patients had a proximal, 18 a distal, and 8 no vessel occlusion. Furthermore, 15 of 43 patients exhibited recanalization on day 2. Vessel occlusion was associated with a PWI-DWI mismatch on the initial magnetic resonance imaging, vessel patency with a PWI-DWI match (p < 0.0001). Outcome scores and lesion volumes differed significantly between patients experiencing recanalization and those who did not (all p < 0.0001). Acute DWI and PWI lesion volumes correlated poorly with acute clinical scores and only modestly with outcome scores. We have concluded on the basis of this study that early recanalization saves tissue at risk of ischemic infarction and results in significantly smaller infarcts and a significantly better clinical outcome. Patients with proximal vessel occlusions have a larger amount of tissue at risk, a lower recanalization rate, and a worse outcome. Urgent recanalization seems to be of utmost importance for these patients.

Aged↗

PubMed2001

Restricted diffusion within ring enhancement is not pathognomonic for brain abscess.

BACKGROUND AND PURPOSE: Recent experience suggests that diffusion-weighted MR imaging may be decisive in the differential diagnosis of ring-enhancing cerebral lesions. Whether restricted diffusion within a ring-enhancing cerebral mass lesion is pathognomonic for abscess was studied. METHODS: Seventeen patients with ring-enhancing cerebral lesions (three abscesses, six glioblastomas, eight metastases) on conventional contrast-enhanced T1-weighted images were examined with echo-planar diffusion-weighted MR imaging. Apparent diffusion coefficient (ADC) maps and the ADCs were calculated for all lesions. Lesions with signs of intralesional hemorrhage on unenhanced T1-weighted images were excluded. RESULTS: The central portion of all six glioblastomas and seven of eight metastases showed unrestricted diffusion, whereas two of three abscesses showed restricted diffusion (low ADC values) in their cavity. However, restricted diffusion also was found in one metastasis, and one abscess within a postoperative cavity showed unrestricted diffusion within a larger nondependent portion. CONCLUSION: In patients with ring-enhancing cerebral mass lesions, restricted diffusion might be characteristic but is not pathognomonic for abscess, as low ADC values also may be found in brain metastases.

Brain Abscess↗

PubMed2000

Robust localization of the contralateral precentral gyrus in hemiparetic patients using the unimpaired ipsilateral hand: a clinical functional magnetic resonance imaging protocol.

Tumor related contralateral motor deficits complicate preoperative functional magnetic resonance imaging (fMRI). In plegic patients the localization of the sensorimotor cortex is often impossible. In this context we developed a clinical fMRI protocol dedicated to patients with motor deficits using the unaffected ipsilateral hand. Based on the hypothesis that selfpaced finger movements recruit more and larger neuronal populations with rising task complexity, different motor tasks were tested regarding ipsilateral localization in ten right handed volunteers. Complex finger opposition localized the ipsilateral premotor cortex (Brodman area 6) robustly and was introduced to preoperative fMRI in hemiparetic patients as functional landmark to identify the precentral gyrus on the tumors side. Additional contralateral automated tactile stimulation localized the primary somatosensory cortex and completed the protocol.

Adult↗

PubMed2000

Increased cerebral glucose utilization and decreased glucose transporter Glut1 during chronic hyperglycemia in rat brain.

Whereas acute hyperglycemia has been shown to result in an unchanged local cerebral glucose utilization (LCGU) the changes of LCGU during chronic hyperglycemia are a matter of dispute. The present study had three aims: (1) To compare the effects of acute and chronic hyperglycemia on LCGU and to investigate in vivo the lactate level as a potential indicator of glycolytic flux. (2) To investigate local changes in brain Glut1 and/or Glut3 glucose transporter densities during chronic hyperglycemia. (3) To analyze the relationship between LCGU and local Glut densities during chronic hyperglycemia. To induce chronic hyperglycemia in rats steptozotocin was given i.p. and experiments were performed 3 weeks later. LCGU was measured by the 2-[14C]deoxyglucose method and intraparenchymal lactate concentration by MR-spectroscopy. Local densities of the glucose transport proteins were determined by immunoautoradiographic methods. During chronic hyperglycemia weighted average of LCGU increased by 13.9% whereas it remained unchanged during acute hyperglycemia. The cerebral lactate/choline ratio was increased by 143% during chronic hyperglycemia. The average density of glucose transporters Glut1 decreased by 7.5%. Local densities of Glut1 were decreased in 12 of 28 brain structures. Glut3 remained unchanged. Positive correlations were found between LCGU and local Glut densities during control conditions and during chronic hyperglycemia. It was concluded that (1) Chronic, but not acute hyperglycemia is followed by an increased LCGU. (2) The capacity to transport glucose is decreased during chronic hyperglycemia. (3) Increased LCGU and decreased densities of Glut1 are matched on a local level.

Animals↗

PubMed2000

MR contrast agents in acute experimental cerebral ischemia: potential adverse impacts on neurologic outcome and infarction size.

The purpose of the study was to investigate the effects of magnetic resonance (MR) contrast agents on neurologic outcome and infarction size in a rat stroke model. Focal cerebral ischemia was induced in 80 rats using an endovascular occlusion technique of the middle cerebral artery. Four hours after occlusion, 64 animals (4 groups of 16 each) received gadodiamide (Gd-DTPA-BMA) in a single (0.1 mmol/kg) or triple (0.3 mmol/kg) clinical dose or the ultrasmall superparamagnetic iron oxide particles contrast agent NC 100150 in a single (0.03 mmol/kg, 1.5 mg Fe(2+)/kg) or double (0.06 mmol/kg, 3.0 mg Fe(2+)/kg) clinical dose, respectively. Sixteen animals received equivolumetric saline (control group). Neurologic score and body weight were recorded every 8 hours. Twenty-four hours after vessel occlusion, infarction size was measured by 2,3, 5-triphenyl-tetrazolium-chloride (TTC) staining. Neither the normal nor the triple clinical dose of gadodiamide or NC 100150 in the single or double dose had any statistically significant effects on infarction volume, mortality, body weight, or neurologic outcome (P > 0.05). Our results suggest that bolus injection of gadodiamide and the ultrasmall superparamagnetic iron oxide particles NC 100150 in clinically relevant doses does not significantly affect infarction volume and clinical outcome of acute cerebral ischemia.

Animals↗

PubMed2000

Cerebral MR perfusion imaging: first clinical application of a 1 M gadolinium chelate (Gadovist 1.0) in a double-blinded randomized dose-finding study.

The purpose of this study was to evaluate efficacy and safety of the 1 M gadolinium chelate Gadovist 1.0 for assessment of cerebral hemodynamics with dynamic susceptibility contrast-enhanced magnetic resonance (MR) imaging. Eighty-nine patients with carotid artery stenosis or cerebral infarcts were included in this multicenter, double-blinded study using five dose groups from 0.1 to 0.5 mmol/kg. Imaging was performed with 1-T scanners using a T2*-weighted fast low-angle shot (FLASH) sequence. Dose-dependent changes in quantitative and qualitative parameters describing signal-time curves and relative regional cerebral blood volume maps were investigated. For safety evaluation, vital signs, clinical and laboratory tests, and adverse events were assessed. The quantitative measurements revealed an optimal dose of 0.4 mmol/kg. The qualitative evaluation revealed that the required qualitative assessment for clinical purposes was already reached at a dose of 0. 3 mmol/kg. No significant changes in vital signs and laboratory tests were found. No serious adverse events were observed. The combined results revealed the dose of 0.3 mmol/kg as the diagnostically adequate dose given the gradient-echo sequence and field strength used. Gadovist 1.0 has been shown to be a safe and well-tolerated contrast agent. J. Magn. Reson. Imaging 2000;12:371-380.

Adolescent↗

PubMed2000

Reducing motion artefacts in diffusion-weighted MRI of the brain: efficacy of navigator echo correction and pulse triggering.

Diffusion-weighted MRI (DWI) is extremely sensitive to motion of the object being examined. Pulse triggering and navigator echo correction are methods for reducing motion artefacts which can be combined with conventional DWI sequences. Implementation of these methods in imaging sequences with a readout of one, three, or five echoes is presented and imaging results compared in a study of five healthy volunteers. As an objective measure for motion-induced image artefacts, the "artefacticity" of an image is defined. Pulse triggering and navigator echo correction significantly improve image quality and provide a technique for high-quality DWI on standard imagers without improved gradient hardware.

Adult↗

PubMed2000

Magnetisation transfer ratio is low in normal-appearing cerebral white matter in patients with normal pressure hydrocephalus.

We measured the magnetisation transfer ratios (MTR) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, the genu (CG) and the splenium (CS) of the corpus callosum and the thalamus (TH) in 12 patients with normal-pressure hydrocephalus (NPH) and compared them with 16 healthy control subjects. We found a significantly lower MTR in the NPH group than in the normal group for PR, PC, CG, and CS but not for TH. MT measurements give additional information which cannot be gained by conventional MRI, suggesting that NPH is associated with diffuse white matter damage, even in normal-appearing cerebral white matter.

Adult↗

PubMed2000

[Is perfusion MRI feasible in lesions with disrupted blood-brain barrier? Pitfalls and possible solutions].

AIM: When using perfusion-weighted magnetic resonance imaging (MRI) in lesions with blood-brain barrier (BBB) disruption two methods are normally applied to eliminate the influence of contrast material uptake on T2* dynamics: injection of contrast agent before starting perfusion imaging (pre-injection) and simultaneous acquisition of T1- and T2*-dynamics using a dual echo (DE)-FLASH sequence. The purpose of this study was to examine both methods with regard to their reliability. MATERIAL AND METHODS: We performed four perfusion measurements in a patient with a primary cerebral lymphoma located in the corpus callosum: two measurements with a DE-FLASH sequence and two measurements with a gradient-echo echo-planar-imaging (GE-EPI) sequence, respectively. In both cases there was one measurement with and one without pre-injection of contrast material. RESULTS: Pre-injection of contrast material reduced the influence of T1 and allowed us to monitor the transient signal drop when using the GE-EPI sequence. Analysis of the time-course of DE-FLASH, however, showed that there was still a T1 decrease even after pre-injection. After the first pass the T2*-dynamics showed a distinct long-term T2*-decrease. DISCUSSION: Neither pre-injection nor DE-FLASH allow us to eliminate the effects of contrast agent uptake completely. Both methods, however, increase the reliability of perfusion MRI. Their efficacy depends on the extent of the BBB disruption.

Aged↗

PubMed2000

Multiple hexose transporters of Schizosaccharomyces pombe.

We have identified a family of six hexose transporter genes (Ght1 to Ght6) in the fission yeast Schizosaccharomyces pombe. Sequence homology to Saccharomyces cerevisiae and mammalian hexose transporters (Hxtp and GLUTp, respectively) and secondary-structure predictions of 12 transmembrane domains for each of the Ght proteins place them into the sugar porter subfamily within the major facilitator superfamily. Interestingly, among this sugar porter family, the emerging S. pombe hexose transporter family clusters are separate from monosaccharide transporters of other yeasts (S. cerevisiae, Kluyveromyces lactis, and Candida albicans) and of humans, suggesting that these proteins form a distinct structural family of hexose transporters. Expression of the Ght1, Ght2, Ght5, and Ght6 genes in the S. cerevisiae mutant RE700A may functionally complement its D-glucose uptake-deficient phenotype. Northern blot analysis and reverse transcription-PCR showed that among all Ght's of S. pombe, Ght5 is the most prominently expressed hexose transporter. Ght1p, Ght2p, and Ght5p displayed significantly higher specificities for D-glucose than for D-fructose. Analysis of the previously described S. pombe D-glucose transport-deficient mutant YGS-5 revealed that this strain is defective in the Ght1, Ght5, and Ght6 genes. Based on an analysis of three S. pombe strains bearing single or double mutations in Ght3 and Ght4, we conclude that the Ght3p function is required for D-gluconate transport in S. pombe. The function of Ght4p remains to be clarified. Ght6p exhibited a slightly higher affinity to D-fructose than to D-glucose, and among the Ght's it is the transporter with the highest specificity for D-fructose.

Amino Acid Sequence↗

PubMed2000

Monitoring intravenous recombinant tissue plasminogen activator thrombolysis for acute ischemic stroke with diffusion and perfusion MRI.

BACKGROUND AND PURPOSE: Intravenous recombinant tissue plasminogen activator (rtPA) administration is an effective therapy for ischemic stroke when initiated within 3 hours and possibly up to 6 hours after symptom onset. To improve patient selection, a fast diagnostic tool that allows reliable diagnosis of hemorrhage and ischemia, vessel status, and tissue at risk at an early stage may be useful. We studied the feasibility of stroke MRI for the initial evaluation and follow-up monitoring of patients undergoing intravenous thrombolysis. METHODS: Stroke MRI (diffusion- and perfusion-weighted imaging [DWI and PWI, respectively], magnetic resonance angiography, and T2-weighted imaging) was performed before, during, or after thrombolysis and on days 2 and 5. We assessed clinical scores (National Institutes of Health Stroke Scale [NIHSS], Scandinavian Stroke Scale [SSS], Barthel Index, and Rankin scale) at days 1, 2, 5, 30, and 90. Furthermore, we performed volumetric analysis of infarct volumes on days 1, 2, and 5 as shown in PWI, DWI, and T2-weighted imaging. RESULTS: Twenty-four patients received rtPA within a mean time interval after symptom onset of 3.27 hours and stroke MRI of 3.43 hours. Vessel occlusion was present in 20 of 24 patients; 11 vessels recanalized (group 1), and 9 did not (group 2). The baseline PWI lesion volume was significantly larger (P=0.008) than outcome lesion size in group 1, whereas baseline DWI lesion volume was significantly smaller (P=0.008) than final infarct size in group 2. Intergroup outcome differed significantly for all scores at days 30 and 90 (all P<0.01). Intragroup differences were significant in group 1 for change in SSS and NIHSS between day 1 and day 30 (P=0.003) and for SSS only between day 1 and day 90 (P=0.004). CONCLUSIONS: Stroke MRI provides comprehensive prognostically relevant information regarding the brain in hyperacute stroke. Stroke MRI may be used as a single imaging tool in acute stroke to identify and monitor candidates for thrombolysis. It is proposed that stroke MRI is safe, reliable, and cost effective; however, our data do not prove this assumption. Early recanalization achieved by thrombolysis can save tissue at risk if present and may result in significantly smaller infarcts and a significantly better outcome.

Acute Disease↗

PubMed2000

Feasibility and practicality of MR imaging of stroke in the management of hyperacute cerebral ischemia.

BACKGROUND AND PURPOSE: Neuroimaging techniques such as diffusion- and perfusion-weighted MR imaging have been proposed as tools for advanced diagnosis in hyperacute ischemic stroke. There is, however, substantial doubt regarding the feasibility and practicality of applying MR imaging for the diagnosis of stroke on a routine basis, especially with respect to possible delay for specific treatment such as thrombolysis. In this study, we tested whether MR imaging of stroke is safe, fast, and accurate, and whether the gain in additional information can be used in the daily routine without a loss of time and a risk of suboptimal treatment for the patient with stroke. METHODS: Between September 1997 and August 1999, 64 patients with acute ischemic stroke were recruited for MR imaging (ie, diffusion-weighted imaging, perfusion-weighted imaging, MR angiography, T2-weighted imaging) after a baseline CT was performed. We evaluated practicality and feasibility of MR imaging of stroke by analyzing the intervals between symptom onset, arrival, CT, and MR imaging. RESULTS: Sixty-four patients (mean age, 60.9 years) underwent routine CT and MR imaging within 12 hours after stroke onset (n=25, < or =3 hr; n=26, 3-6 hr; n=13, 6-12 hr). Median times to arrival, start of CT, MR imaging, and between CT and MR imaging were 1.625 hours, 2 hours, 3.875 hours, and 1 hour, respectively. Intervals between symptom onset and MR imaging (P<.005), arrival and MR imaging (P<.002), and CT and MR imaging (P=.0007) differed significantly between the early phase of the study and after November 1998, whereas the intervals between symptom onset and arrival, symptom onset and CT, and arrival and CT did not. Hemorrhage could be excluded in all; a perfusion/diffusion match or mismatch could be shown in 63 of 64 patients. CONCLUSION: Practice and experience with MR imaging in a stroke team significantly reduce the time and effort required to perform this technique and thus make 24-hour availability for MR imaging of stroke practical. Assessment of patients with hyperacute stroke is rapid and comprehensive. Image quality can be substantially improved by head immobilization and by mild sedation, if necessary.

Adult↗

PubMed1999

Somatotopic mapping of the human primary somatosensory cortex by fully automated tactile stimulation using functional magnetic resonance imaging.

The clinical application of functional magnetic resonance imaging (fMRI) requires time-saving protocols insensitive to artifacts that provide robust localization and important information on brain function. A fully automated, pneumatically driven tactile stimulation is presented, that reproducibly localizes postcentral lip, finger and toe representations in contralateral primary somatosensory cortex (SI) with mean correlation coefficients (cc) and relative BOLD signal changes (dS) of cc approximately 0.59, dS approximately 1.95% (fingers); cc approximately 0.52, dS approximately 1.35% (lips); cc approximately 0.47, dS approximately 1.42% (toes). Bilateral somatotopic mapping requires 21 min of scanning time and has become a clinical routine fMRI application in patients with perirolandic tumors. Normative data may also be useful in monitoring cerebral plasticity and reorganization, e.g. in sensorimotor recovery after cerebral ischemia or in understanding mechanisms of supraspinal pain processing.

Adult↗

PubMed1999

Brain water content, glucose transporter densities and glucose utilization after 3 days of water deprivation in the rat.

After 3 days of water deprivation, the following parameters were measured in rats: (i) brain water content (apparent diffusion coefficient); (ii) local cerebral glucose utilization (LCGU) ([14C]deoxyglucose method) and (iii) densities of glucose transporters Glut1 and Glut3 (immunoautoradiography). The results show that brain water content is maintained after water deprivation. Densities of glucose transporters Glut1 and Glut3 increased in parallel to increased LCGU in some of the osmoregulatory structures indicating a long-term local adaptation of glucose transporters to LCGU.

Animals↗

PubMed1999

Simultaneous assessment of cerebral hemodynamics and contrast agent uptake in lesions with disrupted blood-brain-barrier.

The purpose of this study was to develop a method that eliminates the influence of the T1 relaxation time upon the signal-time course in perfusion-weighted imaging of cerebral lesions with blood-brain-barrier (BBB) disruption. On a 1.5 T whole body clinical magnetic resonance (MR) imager, we implemented a dual-echo RF-spoiled FLASH sequence (TE=6/23.6 ms). We developed a postprocessing routine that allowed to calculate a signal-time course representing only the change in T2* and another one representing only the change in T1. Using this method, we examined 7 patients with various brain lesions showing evidence of BBB disruption. In the signal-time-curves obtained from the early echo we found a distinct signal drop due to the T2* effect. These effects could be eliminated by the correction algorithm yielding a 67% higher signal increase. Correction of the signal-time curve of the late echo yielded a more pronounced maximum signal drop and a decrease in postcontrast signal intensity. We found that without this correction the relative regional cerebral blood volume and the first moment of the concentration-time curve were underestimated by 72% and 22%, respectively. The dual echo-sequence combined with the postprocessing algorithm separates T1 and T2* effects and thus allows to assess cerebral hemodynamics and contrast agent kinetics simultaneously. This method may be a useful tool for characterizing, staging, and therapy monitoring of brain tumors.

Adult↗