No abstract available

No abstract available

[en] A method of measuring cerebral blood flow during neurosurgery is described. It is an adaptation of the standard 133Xe intravenous injection method, with computation restricted to data collected over the first 3 min. In addition to a theoretical presentation of a method and an analysis of the effect of residual 133Xe activity when sequential runs are performed in close approximation, the technique is validated experimentally by comparison with intracarotid 133Xe injection in baboons

[en] Many systems for measuring cerebral blood flow employ scintillation counters which are positioned laterally and therefore detect gamma rays from the contralateral as well as the ipselateral hemisphere. In this paper the source and magnitude of the errors introduced by this are discussed and a method of compensating for these errors is presented. (author)

[en] Sources of error in the estimation of ventricular volume from CAT scans are discussed and the accuracy of the measurement assessed. Two methods of calculating ventricular volume from an intraventricular injection of radioisotope are described and compared. Finally, the CAT scan and isotope methods are compared and contrasted. The error associated with single measurement of volume by any of these techniques is between 20% and 30%. In patients with no ventricular catheter there is no choice other than to use CAT scanning, but if intraventricular injection is possible this method offers a potentially more accurate volume determination because of its higher signal-to-noise ratio. (author)

[en] A loss of acetylcholine is one of the most consistent neurochemical findings in Alzheimer's disease (AD) post-mortem, but the debate concerning receptor abnormalities is unresolved. The aim of this investigation was to measure the density of acetylcholine muscarinic receptors in AD patients at various stages in the disease (N=8) by synthesising a radio-iodinated version of quinuclidinyl benzilate QNB, a potent muscarinic antagonist. Deficits were identified by comparison with a control data set obtained from four elderly volunteers and then compared to the deficit in total functional activity in the same brain regions measured using the cerebral perfusion tracer technetium-99m hexamethylpropylene amine oxime. Iodine-123 (R, R)quinuclidinyl benzilate (QNB) was synthesised using a CuI assisted nucleophilic aromatic exchange reaction. 160 MBq of the radioligand (specific activity 400 Ci/mmol: Dose 90 ng/kg) was administered to each subject. Diagnosis of AD was made using the CAMDEX and DSMIIIR criteria with a physical examination, full blood screen, CT and chest X-ray. All subjects were scanned at 21 h post injection on an SME810 emission tomograph. ¹²³I(R, R)QNB activity in the controls was found to be consistent with the known distribution of muscarinic receptors with no activity in the cerebellum and low activity in the thalamus. In the AD patients deficits in ¹²³I-QNB binding which exceeded the corresponding total functional regional perfusion deficit were not found in six of the patients and were observed only in the two most severely affected patients, both of whom were untestable on the cognitive battery. This adds weight to the evidence that a major reduction in postsynaptic receptor density takes place only at a very late stage of AD. (orig.)