Biomedical subjects

K Strijckmans

Publications and source records attributed to K Strijckmans.

At least 37 records · Page 2Linked to original sources

PubMed1997

Crossed cerebellar diaschisis after middle cerebral artery infarction.

It is unclear whether crossed cerebellar diaschisis (CCD) is merely an epiphenomenon, as its clinical significance remains uncertain. We retrospectively analysed the positron emission tomographic (PET) findings in 28 patients with a chronic, stable middle cerebral artery (MCA) infarct and in 22 controls, using the steady state technique and 15O. Also, the Orgogozo scores on admission and at the time of the PET examination were compared in the patients with MCA infarction. Based on the asymmetry index and the 95% confidence limits for regional cerebellar blood flow (rCBF) and oxygen consumption (rCMRO2) in the control group, the stroke patients were subdivided in a group with (n = 8) and a group without (n = 20) CCD. The CCD group had lower values of rCMRO2 in the infarct and border areas compared to those of the non-CCD patients. The infarct location within the MCA territory was similar but the size was somewhat larger in the CCC group. The degree of neurological improvement was better in the non-CCD group. Although persistence of CCD has no real clinical significance it appears to be correlated to more severe and widespread ischaemia in the affected MCA territory and to the lack of significant clinical improvement.

Adult↗

PubMed1997

Cerebral oxygen metabolism in patients with progressive supranuclear palsy: a positron emission tomography study.

To investigate cerebral oxygen metabolism in progressive supranuclear palsy (PSP), 5 patients with a clinical diagnosis of PSP and a variable degree of cognitive deficit were selected for positron emission tomography (PET) of the brain. In 4 of them, a significant decrease in oxygen metabolism was found in all cortical regions, without frontal accentuation. In the group as a whole, this decrease was even slightly more marked in parietal and temporal regions. These findings are not consistent with earlier PET studies that demonstrated frontal targeting of hypometabolism in PSP patients. Part of this discrepancy can be explained by differences in methodology, although the use of different clinical criteria and overlap of PSP with other neurodegenerative diseases must be taken into account. It is concluded that the absence of frontal hypometabolism on PET examination does not exclude the diagnosis of PSP.

Aged↗

PubMed1997

55Co-PET in stroke: relation to bloodflow, oxygen metabolism and gadolinium-MRI.

BACKGROUND: Several studies have shown the feasibility of Co-isotopes (55Co and 57Co) in imaging of neuronal damage in stroke, multiple sclerosis, cerebral tumors and trauma. These studies indicate that Co-isotopes allow visualization of brain pathology related to inflammatory processes, reactive gliosis and cell death. Until now, it is not clear if 55Co accumulation occurs in the core of infarction or in the penumbra. Therefore, in the present study, we compared 55Co-PET with functional parameters such as cerebral bloodflow (rCBF) using C15O2, oxygen metabolism (rCMRO2) using 15O2 and cerebral bloodvolume (CBV) using C15O in PET and with the anatomical parameter Gd-MRI. PATIENTS AND METHODS: Seventeen patients (11 male; 6 female) age 43 to 84 (mean 69) with middle cerebral artery (mca) stroke, as proven by CT or MRI, were examined with 55Co-PET (0.5-1.0 mCi 55CoCl2), C15O2-, 15O2- and C15O-PET in one session 0-30 days after stroke-onset. Regions of infarction were defined by rCMRO2 being smaller than 65% or rCBF below 45% of the contralateral value and were subsequently superimposed on the cobalt scan. To compare the Cobalt uptake with the Gd-MRI, a realignment program was used that matches the MRI with the bloodflow images. Clinical status was established using the Orgogozo stroke scale at admission and at discharge (at least 6 weeks after admission) and the Barthel index. RESULTS: Eight patients showed a positive Co-PET scan and were used for further analysis. It appeared that Co accumulates in areas with a diminished oxygen metabolism and with a preserved bloodflow. We found Co-uptake in only a part of the Gd enhanced brain tissue with a tendency to be located peripherally or outside the Gd demarcated brain tissue. CONCLUSION: The results of the present study suggest that Co accumulates into infarcted brain tissue with a rather preserved flow independently of blood-brain barrier breakdown.

Adult↗

PubMed1996

Late-onset epileptic seizures in patients with leukoaraiosis: a positron emission tomographic study.

Leukoaraiosis, found on computed tomographic scans of the brain, is suspected to be of ischemic origin and is frequently associated with progressive decline of cognitive functions in elderly persons. Some of them also develop late-onset epilepsy. The present positron emission tomographic study investigates if these seizures in mentally nonaffected patients with leukoaraiosis are related to an underlying ischemic process. Patients with leukoaraiosis and late-onset seizures have a more important decline of regional blood flow and oxygen consumption in the cortical areas, compared to normal age-matched controls, to patients with cryptogenic symptomatic late-onset epilepsy and to patients with a similar degree of leukoaraiosis but without epilepsy. The present study suggests that both the late-onset seizures and the leukoaraiosis in patients with, at that time, no obvious mental deterioration are premonitory signs of an encephalopathy of unknown origin, possibly leading to cognitive decline.

Adult↗

PubMed1996

Kinetics of [methyl-11C]thymidine in patients with squamous cell carcinoma of the head and neck.

Thymidine labelled with a position emitter and imaging by positron emission tomography has been suggested to measure tumour proliferation in vivo non-invasively. The present study presents a compartmental model which describes the behavior of [methyl-11C]thymidine in tumour tissue and allows quantification of the data using a proliferation parameter (PP). In nine patients with squamous cell carcinoma of the head and neck, 11C-activity over the tumour and the adjacent blood vessels was measured. The median PP without correction for blood pool activity was found to be 8.61 10(-4) min(-1). With correction this parameter changed from -14% to +40%. We found no correlation between either sex or tumour differentiation and PP. The described model can be used to quantitate [methyl-11C]thymidine uptake in human tumours. Indivdual correction for tumour blood volume is mandatory.

Aged↗

PubMed1995

Ipsilateral thalamic diaschisis after middle cerebral artery infarction.

The significance of ipsilateral thalamic diaschisis (ITD) among patients with chronic, stable middle cerebral artery (MCA) infarcts was investigated. Twenty eight subjects with chronic MCA infarction and twenty two normal controls were studied with positron emission tomography (PET), using the steady state technique with 15O. Stroke patients were subdivided into a group with ITD (n = 12) and a group without ITD (n = 16). Patients with ITD had greater decreases of regional blood flow (rCBF) and oxygen consumption (rCMRO2) in the infarcted MCA territory, compared to MCA infarction without ITD. The neurological deficits at the time of PET scanning were similar between both groups. Extent of infarction by CT brain scan appeared more predominant in peri-insular regions of patients with ITD, while in non diaschisis patients infarcts were more widely distributed throughout the MCA territories. Occurrence of ITD and of crossed cerebellar diaschisis (CCD) did not correlate. Occurrence of ITD seems to be linked to diffuse reductions of blood flow and oxygen metabolism in cortical territories of the MCA. Mechanisms of ITD were different from those of CCD.

Adult↗

PubMed1995

Positron emission tomography in spastic diplegia.

In this study, three patients with spastic diplegia were examined with magnetic resonance imaging (MRI) and positron emission tomography (PET), using the steady state technique with 15O. Two of them had untractable seizures and mental retardation. On MRI the cortical structures were normal; increased T2 signals in the periventricular white matter in the second patient were the main findings. PET scan showed in the two patients with a seizure disorder and mental retardation a large left cortical area of decreased regional blood flow and oxygen consumption during the interictal phase. The third patient without epileptic spells had a normal PET scan examination. It is concluded that the epileptic disorder in two of our cases is due to an additional cortical lesion, while the spastic diplegia is caused by subcortical white matter destruction.

Adolescent↗

PubMed1995

Positron emission tomographic study of late-onset cryptogenic symptomatic seizures.

Ten patients with epilepsy of unknown origin, starting after the age of 50 years, and without clear evidence of cognitive decline were studied with positron emission tomography, using the steady state technique with 15O. Cerebral blood flow and oxygen metabolism were significantly decreased in all cortical areas. No focal areas of hypometabolism were detected. Treatment with phenytoin did not influence the results. It is suggested that late-onset seizures could be the premonitory signs of a progressive encephalopathy of unknown origin.

Aged↗

PubMed1994

Use of 191Pt radiotracer for the development of enrichment procedures to detect natural levels of platinum in biological and environmental materials.

The 191Pt-radiotracer is a powerful tool to develop separation and preconcentration methods for Pt. The radiotracer was produced either through 190Pt (n, gamma) 191Pt reaction on Pt enriched in 190Pt, or through 191Ir (p,n) 191Pt reaction on natural Ir, followed by Pt/Ir separation. The solvent extraction behavior of 191Pt(IV) from HCl with tributylphosphate, rubeanic acid in tributylphosphate and thenoyltrifluoroacetone in n-butylalcohol/acetophenone, followed by back-extraction with 2 mol/L NH4OH was studied. The overall recovery from a biological matrix is up to 80%. Trace amounts of 191Pt were also preconcentrated as bis-(carboxymethyl) dithiocarbamate chelates on an XAD-4 microcolumn and eluted with EtOH/1 mol/L HNO3. More than 80% is recovered in 2 mL or about 70% in 300 microL.

Chromatography, Ion Exchange↗

PubMed1994

Comparison of cerebral haemodynamic and oxygen metabolic changes due to cavernous angiomas and arteriovenous malformations of the brain. A positron emission tomography study.

The cerebral haemodynamic and metabolic changes due to cavernous angiomas in three patients and to arteriovenous malformations in four patients were compared by positron emission tomography, using the steady state technique with 15O. In the brains with a cavernous angioma no important changes in blood flow were observed. Only a decreased oxygen consumption was present in the cortex supplied by the arterial branches of the angioma, most probably related to neuronal deafferentation. In the four cases of arteriovenous malformation cerebral blood flow was significantly increased in the territory of the feeding vessels of the angioma. In the two huge ones the oxygen extraction rate was increased in the other vascular areas remote from the supply territory of the angioma, indicating chronic ischaemia. The present study confirms that chronic vascular steal phenomena can occur in large arteriovenous malformations, while cavernous angiomas do not induce important haemodynamic changes.

Adult↗

PubMed1993

A positron emission tomography study of patients with acute carbon monoxide poisoning treated by hyperbaric oxygen.

Seven patients with an acute and severe carbon monoxide intoxication were treated with hyperbaric oxygen and underwent a positron emission tomographic examination 2-5 days after the acute event. Although the final clinical outcome was good in all patients, ischaemic changes were observed. Three patients with temporary sequelae after hyperbaric oxygen treatment showed the most severe changes, mainly in striatum and thalamus. Although positron emission tomographic examination cannot predict the final outcome, it can show the regions at risk for development of late complications following carbon monoxide poisoning.

Adult↗

PubMed1993

Hemodynamic and metabolic effects of flunarizine in experimental subarachnoid hemorrhage in dogs.

BACKGROUND AND PURPOSE: Cerebral blood flow and oxygen metabolism were measured and a cerebral angiography was performed in dogs with experimental subarachnoid hemorrhage to assess the relation between arterial narrowing (vasospasm) and the fall of blood flow. Cerebral blood volume and the cerebrovascular CO2 reactivity were also measured to estimate the cerebrovascular reserve. Several groups of dogs were treated with flunarizine in different regimens to assess its possible therapeutic effect. METHODS: The experiments were performed in the three-hemorrhage canine model for subarachnoid hemorrhage. Cerebral blood flow and cerebral oxygen metabolism were measured in anesthetized (nitrous oxide) dogs using positron emission tomography in combination with the 15O steady-state method. Basilar artery diameter was evaluated by digital subtraction angiography. RESULTS: In normal dogs, cerebral blood flow, oxygen consumption, and oxygen extraction ratio were 46.4 +/- 9.0 ml/100 ml per minute, 3.65 +/- 0.76 ml/100 ml per minute, and 39.9 +/- 3.4%, respectively; basilar artery diameter was 1.33 +/- 0.25 mm. Repeated subarachnoid blood injection (3 x 5 ml) reduced basilar artery diameter to < 20% of normal (p < 0.01). Cerebral blood flow was reduced by only 25% (p < 0.001); oxygen consumption was preserved at a low normal level by a 29% compensatory increase of the oxygen extraction (p < 0.001). Cerebral blood volume and cerebrovascular CO2 reactivity remained nearly normal. Early (after the first blood injection) peroral treatment with flunarizine (0.5 mg/kg daily) resulted in less severe basilar artery narrowing (56% of normal; p < 0.05 versus untreated). However, this treatment had no effect on cerebral blood flow, blood volume, oxygen consumption, and extraction. CONCLUSIONS: The observed fall of cerebral blood flow in experimental subarachnoid hemorrhage is not related to arterial narrowing but to an increased cerebrovascular resistance at the level of the small parenchymal vessels, and the latter, in contrast to arterial narrowing, is unaffected by flunarizine.

Animals↗

PubMed1992

Positron emission tomography study of the human hypothalamus during normal ageing and in ischemic and degenerative disorders.

Regional blood flow and oxygen metabolism were determined by positron emission tomography, using the steady state technique with 15O, in the hypothalamus and in the whole brain of fifty two normal persons and patients suffering from cerebral ischemia and degenerative dementia. During normal ageing regional blood flow and oxygen consumption appeared to increase slightly in the hypothalamus and to decrease in the whole brain in 24 persons. In the young age group the hypothalamus was more protected against ischemia than in the elderly group. In the aged group with cerebral ischemia and degenerative dementia regional blood flow and oxygen consumption were decreased in the hypothalamus to the same extent as in the whole brain.

Adult↗

PubMed1992

Does the severity of leukoaraiosis contribute to senile dementia? A comparative computerized and positron emission tomographic study.

The present study evaluates the origin, severity and location of leukoaraiosis in senile dementia and in normal ageing. The regional white-matter lucency scores, determined on computed-tomographic scan of the brain, are compared to the regional blood flow, oxygen extraction rate and oxygen consumption, determined by the [15O] steady-state technique with positron emission tomography. Thirty patients, classified according to the presence or absence of leukoaraiosis and their mental status, are examined. The occurrence and severity of dementia appear to be mainly correlated to decreased blood flow and oxygen metabolism in the frontal, temporal and parietal cerebral cortex. Leukoaraiosis in demented and nondemented patients is associated with lowered blood flow in the frontal and parietal white matter. The regional lucency score is increased, and blood flow and oxygen consumption decreased in the frontal white matter of severely demented patients. Frontal leukoaraiosis contributes to dementia and is probably of ischemic origin, while parietal and occipital leukoaraiosis is due to wallerian degeneration.

Aged↗

PubMed1992

Significance of white matter lucencies in posthypoxic-ischemic encephalopathy: comparison of clinical status and of computed and positron emission tomographic findings.

The clinical status and the computed and positron tomographic findings were compared in 10 patients with sequelae of hypoxic-ischemic encephalopathy after cardiopulmonary arrest and successful resuscitation. Conscious patients with moderate neuropsychiatric deficits had no significant computed tomography (CT) scan changes and normal values of regional cerebral blood flow and oxygen consumption, while patients in vegetative state had definite cerebral atrophy on CT scan and a severe and widespread decrease of regional cerebral blood flow and oxygen consumption. This decrease was even more pronounced in vegetative patients with the worst neurological score and with CT scans demonstrating additional diffuse white matter lucencies and hypodensities in the basal ganglia. In this group of patients increased regional oxygen extraction rates mainly in the white matter indicated the occurrence of delayed ischemic changes. The positron emission tomography and CT findings correlated well with the degree of posthypoxic-ischemic damage and the clinical status of the studied subjects.

Adult↗

PubMed1987

Current methodology for oxygen-15 production for clinical use.

The radionuclide oxygen-15, half-life 2.05 min, is used in simple chemical forms to study oxygen metabolism, blood flow and blood volume in man, using the technique of positron emission tomography (PET). The production of 15O and the preparation of [15O]O2, [15O]CO2, [15O]CO and [15O]H2O is now well established in several PET centres in Europe, North America and Japan. In order to provide a practical design and operational data base for others intending to make use of these techniques an EEC task group representing four European laboratories routinely using 15O in PET studies was set up to review the current practice of 15O production purification and quality control of the clinically useful products.

Carbon Dioxide↗

PubMed1985

Production and quality control of 15O2 and C15O2 for medical use.

The remotely controlled on-line production with a cyclotron of 15O2 and C15O2 for routine medical use is described. The radiochemical purities have been determined and compared with literature data. The impurities formed during irradiation can be removed with appropriate traps. The toxic gases ozone, nitrogen dioxide and carbon monoxide are formed in the target at concentration levels above the "Threshold Limit Value". Therefore a chemical quality control procedure has been developed. A copper oxide-iron oxide trap was found to improve the radiochemical and chemical purity of the C15O2.

Carbon Dioxide↗

PubMed1985

Kinetics of 13N-ammonia incorporation in human tumours.

After intravenous injection of 13N-labelled ammonia time-activity curves were obtained in a series of malignant neoplasms in man from serial cross-sectional scans through the tumour, using positron emission tomography. Low noise images with virtually no artefacts were obtained using a maximum likelihood reconstruction technique. Tracer concentration was expressed as a fraction of the injected dose ml-1 of tumour tissue. In a first group (eight observations) maximum activity [0.9 to 5.2 (mean: 3.3) X 10(-5) of administered dose ml-1 of tumour tissue] was attained approximately 1 to 3 min post injection. This peak was followed by a clearance phase with a half-time varying between 28.3 and 112 (mean: 73.1) min. In a second group (of six cases) after an initial rapid rise of the activity, no clearance was detectable during the time of observation, tracer concentration remaining in plateau or even continuing to rise slightly. Maximum activity in this group ranged from 1.1 to 5.3 (mean: 2.6) X 10(-5) of the administered dose ml-1 of tissue. So far no relation has been established between the height and/or shape of the 13NH3 time-activity curve and a particular tumour type.

Adult↗