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Biomedical subjects

S L Waters

Publications and source records attributed to S L Waters.

15 recordsLinked to original sources
PubMed1991

Asymmetric synthesis of a precursor for the automated radiosynthesis of S-(3'-t-butylamino-2'-hydroxypropoxy)-benzimidazol-2-[11C]one (S-[11C]CGP 12177) as a preferred radioligand for beta-adrenergic receptors.

S-[1-(2,3-Diaminophenoxy)]-3'-(N-t-butylamino)propan-2'-ol has been synthesized in three steps from 2,3-dinitro-phenol and the chiral auxiliary, S-glycidyl-3-nitrobenzenesulphonate, to provide a precursor for labelling S-(3'-t-butylamino-2'-hydroxypropoxy)-benzimidazol-2-one (S-CGP 12177) with the short-lived positron-emitting radionuclide, carbon-11 (t 1/2 = 20.4 min; beta+ = 99.8%). Reaction of the diamine with [11C]phosgene, itself derived from no-carrier-added cyclotron-produced [11C]methane, provides radiochemically and chemically pure S-[carbonyl-11C]CGP 12177 in greater than 95% enantiomeric excess after HPLC. Automated apparatus is described for safely producing up to 5.9 GBq (160 mCi) of S-[11C]CGP 12177 with high sp. act. (20-40 GBq/mu mol or 0.54-1.08 Ci/mu mol) in a form suitable for human intravenous injection at only 30 min from the end of radionuclide production. S-[11C]CGP 12177 is preferred to the formerly described racemate as a radioligand for the study of beta-adrenergic receptors in vivo by positron emission tomography.

Adrenergic beta-Antagonists↗
PubMed1990

Labelled agents for PET studies of the dopaminergic system--some quality assurance methods, experience and issues.

Practical methods are described for the quality assurance of three labelled agents (L-6-[18F]fluoro-DOPA, S-[N-methyl-11C]nomifensine and [O-methyl-11C]raclopride) now produced regularly for PET studies of the dopaminergic system in man. These include indirect methods for the initial determination of label position (e.g. 13C-NMR spectroscopy) and also direct methods for the assessment of chiral purity (TLC and HPLC) and the routine determination of radiochemical purity, chemical purity and specific activity (HPLC). Mass spectrometry has been used to identify some impurities. L-6-hydroxy-DOPA (a precursor in vivo of the neurotoxin, L-6-hydroxydopamine) has been detected by HPLC in some preparations of L-6-[18F]fluoro-DOPA. Formulated S-[N-methyl-11C]nomifensine has been found to decrease in radiochemical purity with storage, whereas formulated [O-methyl-11C]raclopride has been found to be stable. Some quality assurance issues are discussed in relation to experience in the application of the described methods and the obtained results.

Carbon Radioisotopes↗
PubMed1987

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↗
PubMed1977

The measurement of spleen perfusion in man: a non-invasive method using the ratio between Rubidium-81 and its decay product Krypton-81m.

A non-invasive method has been developed for measuring spleen perfusion in man. This involves recording the gamma-ray energy spectra over the spleen following the localisation of Rubidium-81 within the organ by injecting intravenously labelled heat denatured red cells. The spectra are analysed to provide the ratio of Rubidium-81 to its radioactive decay product Krypton-81 m. This ratio is dependent on the rate of perfusion through the organ. The difficulties encountered in applying this steady state method for monitoring tissue perfusion are illustrated and practical means for their solution presented. The results of applying this method to patients with various splenic disorders are presented and compared with those obtained by other workers using different monitoring techniques.

Humans↗
PubMed1977

Investigations into the use of 77Br labelled 5alpha-dihydrotestosterone for scanning the prostate.

The potential use of a potent androgen labelled with a gamma emitting radionuclide for scanning the prostate was investigated. 2alphabromo 5alpha-dihydrotestosterone was synthesized and subsequently labelled with 77Br. The distribution of this compound was studied in rat and human tissues. The maximum concentration of radioactivity in the rat prostate at 1-4 h following the injection was found to be between 0.5-0.8% of the injected dose per gram of the tissue. In the human however, that value was 0.002-0.003%. Considering the overall results it was concluded that this compound is not appropriate for scanning the prostate.

Animals↗
PubMed1976

The use of 123I labelled oestradiol in detecting the human prostate using a gamma camera.

123I labelled oestradiol was administered into patients with either benign hypertrophy or malignancy of the prostate, in order to detect the prostate. Using a gamma camera the results showed considerable radioactivity in the bladder-prostate region. The exact anatomical position of the prostate was determined by emptying the bladder and introducing 123I labelled sodium iodide into the balloon of the catheter already inserted in the bladder. The results demonstrated that the detected radioactivity in this region was in the bladder rather than the prostate. This conclusion was later confirmed by the presence of high level of the radioactivity in the urine and the extremely low concentration of the radioactivity in the prostate after the removal of the gland.

Estradiol↗
PubMed1976

The assay of iodine-123.

Compounds labeled with 123I are becoming more common in scintillation imaging due to the convenient combination of the 13.3-hr half-life and the 159-keV gamma radiation. Here attention is drawn to the particularly large summing effects observed when 123I is counted in a well counter. These could lead to errors in the assay of doses if the analyzer windows used are too narrow.

Iodine Radioisotopes↗