Readily adaptable process control system for 11C methylations.
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Benzazepines↗
Biomedical subjects
P L Horlock
Publications and source records attributed to P L Horlock.
Experience with a 82Sr/82Rb generator for clinical use.
A 82Sr/82Rb generator system is described which is shown to be suitable for continuous intravenous infusion in man. The breakthrough of the 82Sr parent has been closely monitored and remained less than 18.5 Bq mL-1 of infusate. A method using a 0.05% solution of sodium hypochlorite to disinfect the generator resulted in a sterile and pyrogen free eluate. Recommendations are made for the setting up of the generator to ensure the maintenance of its pharmaceutical integrity.
Humans↗
Preparation of [11C]buprenorphine--a potential radioligand for the study of the opiate receptor system in vivo.
A method is described for the preparation of [11C]buprenorphine in high specific activity, based on the reaction of N-(de-cyclopropylmethyl)buprenorphine with "no carrier added" [1-11C]cyclopropanecarbonyl chloride followed by reduction with lithium aluminium hydride. The [1-11C]cyclopropanecarbonyl chloride is itself prepared from cyclotron-produced [11C]carbon dioxide. The overall preparation time is 57 min from the end of radionuclide production, and the radiochemical yield is ca 20%, (decay-corrected from [11C]-carbon dioxide). [11C]Buprenorphine has potential as a radioligand for the study of the opiate receptor system in vivo by means of position emission tomography.
Animals↗
Semi-automated preparation of a 11C-labelled antibiotic--[N-methyl-11C]erythromycin A lactobionate.
A fast semi-automated method is described for labeling the antibiotic, erythromycin A (1), with the short-lived positron-emitting radionuclide, 11C (t 1/2 = 20.4 min), in order to permit the non-invasive study of its tissue uptake in vivo. Labelling was achieved by the fast reductive methylation of N-demethylerythromycin A (2) with [11C]formaldehyde, itself prepared from cyclotron-produced [11C]-carbon dioxide. Rapid chemical and radiochemical purification of the [N-methyl-11C]erythromycin A (3) were achieved by HPLC and verified by TLC with autoradiography. The purified material was formulated for human i.v. injection as a sterile apyrogenic solution of the lactobionate salt. The preparation takes 42 min from the end of radionuclide production and from [11C]carbon dioxide produces [N-methyl-C11]erythromycin A lactobionate in 1-12% radiochemical yield, corrected for radioactive decay.
Carbon Radioisotopes↗
Preparation of carbon-11 labelled albumin microspheres for human clinical use.
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Carbon Radioisotopes↗
Quantitative measurement of blood-brain barrier permeability using rubidium-82 and positron emission tomography.
In normal brain, the blood-brain barrier (BBB) is highly impermeable to K+ cations, their transport being controlled by ATPases situated in the endothelial cell membranes. 82Rb+ is a positron-emitting analogue of K+ with a half-life of 75 s. Using a steady-state model and positron emission tomography, quantitative extraction data for 82Rb+ transport across the BBB have been obtained both in normal human subjects and in a variety of conditions of cerebral pathology. A mean cerebral Rb extraction of 2.1% was found for normal subjects, corresponding to a mean value of 1.1 x 10(-6) cm s-1 for 82Rb+ cation permeability across the BBB. No increase in cerebral Rb extraction was observed for patients with diffusely raised intracranial pressure secondary to obstructive hydrocephalus and benign intracranial hypertension, or for patients with multiple sclerosis or cerebral systemic lupus erythematosus. Cerebral tumours that were enhanced on computed tomography scanning showed a significant increase in local Rb uptake. No correlation between tumour size, or grade of glioma, and tumour Rb extraction was found. Nonenhancing tumours showed no increase in local Rb extraction, and regions of perifocal tumour oedema also had Rb extraction values in the normal range. It is concluded that increased Rb extraction occurs only where tight junction integrity in the BBB breaks down locally, that is, in the microcirculation of enhancing tumours but not in that of perifocal regions of tumour oedema or nonenhancing tumours.
Adult↗
Radioassay problems associated with the clinical use of a 82Rb radionuclide generator.
The short-lived positron emitting radionuclide 82Rb (t1/2 1.27 min) is conveniently available from a 82Sr/82Rb generator system. The parent nuclide (t1/2 25.5d) produced from the spallation of molybdenum, has associated with it varying quantities of other long-lived strontium radionuclides, namely 85Sr, 89Sr and 90Sr. It is important therefore in the clinical use of such material that the levels of strontium radionuclides being administered to patients is carefully assayed and controlled. The problems associated with these measurements are discussed with special reference to the radiation dose received by the patient and the problems in resolving overlapping peaks with different FWHMs.
Humans↗