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Biomedical subjects

I Lemahieu

Publications and source records attributed to I Lemahieu.

7 recordsLinked to original sources
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↗
PubMed1992

Measurement of short-term 11C-thymidine activity in human head and neck tumours using positron emission tomography (PET).

Tumour uptake of 11C-thymidine labeled in the methyl position was assessed after intravenous injection in 13 patients with head and neck tumours. This activity was compared to other tracers such as C15O, 13NH3 and C15O2. In every single case a 'positive' tumour image after injection of 11C-thymidine was obtained. Time-activity curves showed the initial activity to be followed by a rapid decrease over the first 10-15 min with an apparent plateau thereafter. A similar level of uptake was found in normal salivary gland regions and myocardium, while higher activities were noted in liver and kidney parenchyma. It is suggested that both blood flow and cellular metabolism can influence 11C-thymidine imaging in this class of human tumours.

Adult↗
PubMed1991

Measured attenuation correction using the Maximum Likelihood algorithm.

Quantitative determination of local radioactivity concentration in positron emission tomography (PET) requires a good attenuation correction procedure to reconstruct the emission image. Using a similar Maximum Likelihood (ML) algorithm as for the reconstruction of the emission image, a method is proposed to reconstruct a transmission image, i.e. a map of absorption coefficients. This reconstructed transmission image is then used to calculate the attenuation correction factors needed for the ML reconstruction of the emission image. This approach takes automatically into account the convolution step in the acquisition process (caused by various smoothing factors, e.g. the detector width). This results in appreciable noise suppression without loss of resolution due to filtering, thus making the reconstructed images easier to interpret. A comparison is made with other estimates for the measured attenuation correction using phantom studies.

Algorithms↗
PubMed1990

Production of carrier-free 66Ga and labeling of antimyosin antibody for positron imaging of acute myocardial infarction.

A method for labeling monoclonal antimyosin antibodies with 66Ga is described. The radionuclide is a positron emitter (t1/2: 9.4h) produced by means of the 63Cu (4He, n) 66Ga reaction. Purification of the 66Ga from the copper target is described in detail. Monoclonal antimyosin antibodies are labeled with 66Ga at a high yield (99%) by transcomplexation from an acetate buffer with the diethylenetriamine pentaacetic acid (DTPA)-labeled antibody and preliminary evaluated in two dogs for imaging of myocardial necrosis by positron emission tomography.

Animals↗