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Query: UMLS:C0149958 (complex partial seizures)
 2,563 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A digital model study has been developed for quantitative assessment of experimental errors in the analysis of 133Xe clearance curve from the brain. A small computer synthesized a model of the clearance curve, varying combinations of fast and slow components. The curves were convoluted with Poisson random digits to simulate statistical fluctuations. Identical curves were overlapped with varying intervals to study the influence of remaining activity. The height over area method to ten minutes was confirmed to overestimate CBF by 10% to 15% with a slow component of 20 ml/100 gm per minute, and the overstimation was increased with a lower slow flow component. The initial slope value was shown to have a close relationship with the fast flow component when the latter was less than 100 ml/100 gm per minute. Errors due to statistical fluctuations were determined only by the initial height (Ho cps), as the percent standard deviation was deltaHo/Ho in the height over area method and 2 deltaHo/HologHo in the initial slope method, where deltaHo equals square rootHo. Remaining activity caused errors of 1% to 3% in the initial slope method with an injection interval of 15 minutes. The influence of remaining activity can be eliminated with an injection interval of more than 25 to 30 minutes in the initial slope method and more than 40 minutes in the height over area method.
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PMID:Some experimental errors in calculating regional cerebral blood flow from the intracarotid 133Xe clearance curve. A quantitative evaluation employing a digital model. 115 73

We compared the relative sensitivity of two interictal PET techniques, bolus injection of [15O] labeled water for estimation of cerebral blood flow (H2(15)O CBF-PET), and 18F 2-deoxyglucose (18FDG-PET) for cerebral glucose metabolism (CMRglc), and T2-weighted magnetic resonance imaging, in 28 patients with medically intractable complex partial seizures undergoing evaluation for surgery. There were statistically significant associations between lateralization by 18FDG-PET, and MRI, but not H2(15)O CBF-PET, and lateralization of the epileptic focus as defined by scalp-sphenoidal ictal EEG. Fifteen patients had surgery or subdural electrodes. 18FDG-PET was more closely associated with a good outcome than H2(15)O CBF-PET, which, in addition, showed hypoperfusion contralateral to the epileptic temporal lobe in several cases. H2(15)O sensitivity may have been reduced by technical factors, but 18FDG-PET appears to be more specific for localization of epileptic zones.
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PMID:Comparison of PET measurements of cerebral blood flow and glucose metabolism for the localization of human epileptic foci. 146

The effect of the initiation of carbamazepine (CBZ) treatment on regional cerebral blood flow (rCBF) was studied using the intravenous Xenon technique in a group of epileptic patients suffering from complex partial seizures. A slight increase in mean rCBF (10.8 +/- 8.8%, P less than 0.01) was observed in 12 patients after the first month of CBZ treatment, while no rCBF change was found after 6 months of CBZ treatment. Regional analysis showed that the rCBF increase following 1 month of CBZ treatment involved all cortical regions with the exception of the right occipital region, irrespective of the initial value. Repeated rCBF measurements performed in normal volunteers (N = 6) and in epileptic patients (N = 10), chronically treated and not subjected to therapeutic modification, showed no significant change. The initial effect of CBZ on CBF found at the onset of the treatment but not after 4-6 months may be related to the improvement in epilepsy and in cerebral function (as suggested by cognitive findings).
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PMID:Initiation of carbamazepine therapy in partial epilepsy: a regional cerebral blood flow study. 211 63

Intracarotid injection of 133-Xenon and recording of wash out of radioactivity by 254 external stationary detectors was used to measure rCBF. Initial slope values were calculated by a computer, translated into color code and displayed on a TV-screen. rCBF in patients with epilepsy has been the object of former studies. Those who had a cortical focus showed corresponding high blood flow values during attack and during EEG paroxysms without clinical attacks. On the contrary, all other patients with a cortical focus were normal. Patients with complex partial seizures displayed no abnormalities interictally. During generalized epileptic seizures rCBF and metabolism doubled. Distinction must be made between patients with aura (classic migraine) and patients without aura (common migraine). In the latter CBF was normal or slightly elevated. In the former the aura symptoms are associated with reduced CBF. The reduction usually starts posteriorly and spreads gradually anteriorly. rCBF remains depressed for up to several hours into the headache phase. After 8-12 hours a reactive hyperemia may ensue. In common migraine rCBF remains normal throughout the attack. During classic migraine attacks rCBF is depressed whereas it is increased during epileptic attacks. Thus rCBF studies further strengthen the differences between epilepsy and migraine.
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PMID:Regional cerebral blood flow (rCBF) studies in migraine and epilepsy. 360 67

Repeated CBF-measurements can be performed after inhalation or intravenous injection of 133Xe. After the development of a bicompartmental model by Obrist et al. in 1975 atraumatic CBF-measurements became widely used but there were still some difficulties concerning the sensitivity of different flow-indices towards CBF changes in normals under test conditions or ischemia in stroke patients. Due to the "slippage phenomenon" mostly noncompartmental flow-indices are used for the detection of ischemic brain areas. In this study a scintillation camera, that is usually available in every nuclear medicine department, was used for atraumatic CBF-studies. A collimator consisting of hexagonal lead tubes (septa 0.2 mm thick; FWHM 1.7 cm in 10 cm) was constructed for this purpose. The obtained counting rate varied between 2432 and 9081 cps over the whole hemisphere and 116-1094 cps in regions of approximately 2.5 X 2.5 cm. In 31 patients with CVD CBF was measured with the intracarotid (i.c.) technique and 1 hour later after i.v. 133Xe-injection. Intravenous flow values were comparable to those obtained after i.c. 133Xe injection (fB X MFr = 0.904; p less than 0.001). In 12 of the used 13 regions also significant correlation coefficients were found. In order to estimate the reproducibility of the intravenous injection method CBF-measurements were performed in both hemispheres of 10 patients on two consecutive days. Highly significant correlation coefficients were found for hemispheric blood flow (r = 0.933; p less than 0.001) and temporal, frontotemporal, temporoparietal and praecentral regions, while in the high parietal, frontal and occipital region lower reporducibility was found. Normal CBF-values were obtained from 12 healthy volunteers (MF right hemisphere: 50.7 +/- 4.6 ml/100 g/min; MF left hemisphere: 50.6 +/- 4.6 ml/100 g/min). MF did not show any hyperfrontality, while F1 and the ISI gave highest flow values in frontal regions. The clinical status of 76 patients suffering from cerebral ischemia (68 with flow disturbances in one hemisphere, 8 with vertebrobasilar insufficiency) was estimated by a semiquantitative scorescale at time of admission and after an observation period lasting from 6 to 35 months. In each case CBF was measured twice: once in the subacute stage after onset of symptoms and once after the observation period. The duration of neurologic symptoms (TIA, RIND, CS) was compared to the obtained flow values. A significant relationship was found between the duration of symptoms and impairment of CBF, thus showing the prognostic value of intravenous CBF measurements.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Noninvasive measurement of cerebrovascular circulation with the scintillation camera. A neurologic nuclear medicine study]. 659 71

The inhalation of C15O2 can be used for determining local cerebral blood flow (LCBF) using a quantitative model. The determination of LCBF in three dimensions using positron emission tomography (PET) involves errors due to counting statistics, data manipulation, and the estimation of parameters in the mathematical model. This work examines error propagation and its relation to the radiation dose to the subject's lungs. An expression has been derived for the root mean square uncertainty in LCBF as a function of LCBF, the spatial resolution and the sensitivity of PET instrument, the normal variability in the brain-blood partition coefficient for water, and absorbed radiation dose to the subject's lungs. The error in LCBF increases as CBF increases. At a normal cortical LCBF of 80 ml/100 g-m and a PET instrument with a 1.65 cm FWHM resolution, and a 46,000 cps per microCi/g sensitivity per slice, an error (coefficient of variation) of 5% results from an inhaled activity of 250 mCi, resulting in a lung dose of 5 rads, the maximum permissible dose allowed. For a more acceptable dose of 1.2 rads, the error is 7%. At a higher resolution (0.8 cm FWHM) and lower sensitivity (15,000 cps per microCi/g per slice), errors become on the order of 28% for a lung dose of 1.2 rads. Errors due to other factors such as blood sample counting, and instrument cross calibration can be virtually eliminated by proper technical strategies. This consideration of error and its relation to radiation dose is important for the application of this inhalation technique for the quantification of LCBF.
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PMID:Error analysis for the determination of cerebral blood flow with the continuous inhalation of 15O-labeled carbon dioxide and positron emission tomography. 680 87

To study quantitative alterations in regional cerebral blood flow (rCBF) accompanying seizures, and to assess the utility of ictal activation PET scanning as a noninvasive clinical tool for localization of epileptogenic foci, we used pentylenetetrazole (PTZ) to induce seizures during 15O-water positron emission tomography (PET) CBF measurement in 15 patients with uncontrolled complex partial seizures (CPS) who had been referred for surgical evaluation. Continuous EEG monitoring was performed during the PET scans. After baseline scans were obtained, each patient was injected with 150-300 mg PTZ. Two patients had generalized tonic-clonic seizures (GTCs). CBF increases were asymmetrical. Two patients (in 1 the seizure occurred spontaneously, without PTZ injection) who had CPS had bitemporal 70-80% increases in CBF. Thalamic CBF increased during both CPS and GTCS. Five patients had an increase in focal EEG interictal abnormality, accompanied by focal flow decreases in 3. PTZ injection not accompanied by clinical seizures did not increase CBF. Partial seizures may be associated with bilateral increases in CBF, and subcortical gray regions are involved in ictal activation.
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PMID:Effect of seizures on cerebral blood flow measured with 15O-H2O and positron emission tomography. 876 21

A beta microprobe was successfully applied to monitor arterial input function for quantification of regional cerebral blood flow (rCBF) in the monkey brain with (15)O-water and positron emission tomography (PET). The sensitivity of the probe was approximately 0.83 to 1.67 cps/kBq/ml depending on the studies. A preliminary study was performed to find a suitable use and to evaluate the performance of the system and data analysis procedure. The results showed that dispersion correction of measured input function was unnecessary if microprobes were connected directly to the arterial catheter. Then multiple CBF measurements were done in three monkeys under anesthesia. Identical regions of interest were placed with the aid of magnetic resonance imaging (MRI) of each monkey and rCBF values were estimated. Estimated rCBFs were reproducible for several measurements. The mean CBF value for a pentobarbital anesthetized monkey was 46.0 ml/min/100 g (PaCO2 = 46.3 mmHg). This shows that the use of the beta microprobe for quantification of rCBF with PET was validated. The lack of a need for dispersion correction of observed input function is an advantage with the beta microprobe system because the probes are small enough to be placed near the arterial sampling site.
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PMID:Application of a beta microprobe for quantification of regional cerebral blood flow with (15)O-water and PET in rhesus monkeys. 955 56