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Results for “Nitrogen Radioisotopes”

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At least 19 recordsLinked to original sources
PubMed1990

Direct determination of nitrification in marine waters by using the short-lived radioisotope of nitrogen, N.

Biological oxidation of radiolabeled NH(4) (half-life = 10 min) was observed within minutes in assays of an estuarine ammonium oxidizer and in natural populations of nitrifiers in coastal waters. Our estimates of turnover of the ammonium pool and rates of nitrification based on experiments using N are consistent with previous values in the literature based on longer-term N tracer experiments or on indirect methods and thus provide corroboration for the estimates by other researchers.

Journal Article↗
PubMed1992

Detection and quantitation of 17F formation during the cyclotron production of 13N.

The positron emitter 17F has been identified for the first time as a radioactive contaminant formed during 13N production. It was determined that 17F made up 18% of the short-lived radioactivity previously thought to be exclusively 15O. Mathematical deconvolution of decay curve data was employed as a complement to radioanalytical techniques. The nuclidic composition of the effluents from the proton bombardment of (a) water, (b) dilute ethanol and (c) 13C powder/water slurry was determined and compared with previous literature values.

Fluorine Radioisotopes↗
PubMed1995

Characteristics of the chemical forms of 11C, 13N, and 15O induced in air by the operation of a 100 MeV electron linear accelerator.

To characterize airborne radioactivity induced by the operation of high-energy accelerators, the fractions of aerosol and gaseous components, and the chemical forms of 11C, 13N, and 15O produced in the air of a target room of a 100 MeV electron linear accelerator were studied. Measurements of radioactivity using a particulate air sampling filter and a gas flow-through ionization chamber showed that more than 98% of 11C, 13N, and 15O were present as gaseous forms. Their chemical forms, detected by means of radio-gas chromatography, were 11C as CO2; 13N as N2 and NO; and 15O as O2 and NO. Machine operating conditions, which affect the compositions of the induced radionuclides and of their chemical forms, and the resulting effect on the estimation of internal doses are discussed.

Aerosols↗
PubMedDate not supplied

Absorbed dose comparison: positron emitters 11C, 13N, and 15O versus gamma-ray emitters.

Absorbed doses were calculated or taken from the literature for various compounds of 11C, 13N, and 15O, and compared to those of presently gamma-ray-emitting nuclear medicine radiopharmaceuticals. As a rule of thumb, the doses per millicurie of the injectable positron-emitting compounds are of the same order of magnitude as the dose per millicurie of 99mTc compounds. The absorbed doses from the injectable positron emitters are nearly one or more orders of magnitude lower on a per millicurie basis than those from the other injectable gamma emitters that were investigated.

Carbon Radioisotopes↗
PubMed1977

[Remote system for the mass production of short-lived radioisotopes in a cyclotron. Development of the system and radioisotope production].

A system was developed for producing short-lived radioactive substances (11CO, 11CO2, 13NN, 13NH3, 18F-, 62Zn2+, 123I-, etc.) on a scale enough for clinical use, which could also be used for analyzing them rapidly and for investigating their production methods, with less received dose by workers. The system enabled us to produce remotely several tens mCi of of short-lived radioactive susbtances readily usable for clinical diagnosis, continuosly for radioactive gases, 11CO, 11CO2 and 13NN, or repeatedly at short intervals for radioactive aqueous solutions of 13NH3, 18F-, etc. Employing this system, the average received dose per month was reduced considerably.

Carbon Radioisotopes↗
PubMed1999

[Use of a cyclotron in the production of positron emitting radionuclides].

The experience acquired by our center during the first two years of using cyclotron 18/9 (IBA) dedicated to the production of clinical positron emission radionuclides is described. The cyclotron performance characteristics, production yields, quality control and synthesized radiotracers are analyzed. Cyclotron makes it possible to produce up to 3,300 mCi of 18F-, 270 mCi of 18F2, 3,100 mCi of 11C, 502 mCi of 13N (in 120, 60, 35 and 20 minutes respectively) and 540 mCi/min of 15O. In our center, about 85% of the PET studies are performed with 18F-FDG, whereas the remaining are done with 15O-water, 11C-bicarbonate, 11C-methionine, 13N-ammonia or 18F-. Cyclotron is included in the Radiopharmacy Unit of our PET facility and is subjected to a global quality control program. Follow-up of the bombardment parameters and periodic verifications of the cyclotron performance have made it possible to prevent equipment functioning problems, increase mean time between stoppage and decrease downtime. We conclude that cyclotron has high production capabilities and allows enough flexibility for a clinical and research positron emission tomography center; furthermore, it can also be used for regional distribution of 18F-FDG to satellite PET centers.

Carbon Radioisotopes↗
PubMed1979

A selected bibliography of biomedical and environmental applications of stable isotopes. V-2H, 13C, 15N, 18O and 34 S, 1977-1978.

The first biennial updated compilation, for the period 1977-1978, of selected references to the use of 2H, 13C, 15N, 18 O and 34S in biochemical, pharmacological, clinical and environmental applications is presented. Author and subject indices for this information are compiled to enable the reader to make further use of these references.

Bibliographies as Topic↗
PubMed1989

A diagnostic study of proton-beam irradiated water targets.

A non-destructive method was developed for assessing the average density of a small-volume water target during particle beam irradiation. Due to local boiling of the target water the particle beam penetrates through the target and further through the thin back wall of the target unit. The charged particle beam excites water molecules both in the target water and in the cooling water. A light guide was inserted into the target cooling water to transfer the light emitted during de-excitation to a photodiode which produced a voltage signal when the beam entered the cooling water. Beam current and target-water temperature were recorded simultaneously with the diode voltage signal. The light emitted in the target during irradiation was photographed through a glass window on the target. Photographic views of the target medium during irradiation are presented. Formation of voids in the beam path of the target was verified with the photographic technique.

Fluorine Radioisotopes↗
PubMedDate not supplied

The isochronous cyclotron: principles and recent developments.

The principals of a cyclotron are described. A magnetic field guides the ions in circular paths, while an electric field accelerates them. The main problem in any accelerator is not to accelerate ions, but to focus them. An isochronous cyclotron overrules the problems related to relativistic mass increase during acceleration. Harmonic operation and negative (vs positive) ion acceleration (and extraction) are explained, as they make dedicated PET cyclotrons a simple, reliable, and suitable tool. The characteristics of such PET cyclotrons are described, as well as their technical implementation. The IBA 18/9 PET cyclotron is given as an example.

Carbon Radioisotopes↗
PubMedDate not supplied

Measurement of activity yields for 12C(gamma, n)11C, 14N(gamma, n)13N, and 16O(gamma, n)15O reactions as a function of electron beam energy and angle from the electron beam using thick target produced bremsstrahlung.

The calculation of activity yields from practical photonuclear target systems designed to produce short-lived positron emitting radionuclides for nuclear medicine purposes requires certain basic information. These include a knowledge of the photon source (bremsstrahlung energy spectrum and intensity as a function of angle from the electron beam) and the gamma, n activation cross section of the secondary target element. A lack of adequate information concerning these parameters motivated the present study in which activity yields for the reactions 12C(gamma, n)11C, 14N(gamma, n)13N, and 16O(gamma, n)15O were measured as a function of energy of and angle from the electron beam between 16 and 30 MeV and 0 degree and 30.5 degrees, respectively. The data indicate highly complex relationships between the activity yield and the experimental variables. Also indicated are possible applications of the data to indicate the energy of an electron beam producing a given bremsstrahlung field in which activation measurements are made.

Carbon Radioisotopes↗