J.M. Peters

A Positron Emission Tomography Study of Voluntarily and Electrically Contracted Human Quadriceps

Keywords: muscular blood flow; positron emission tomography; nuclear magnetic resonance

Production of oxygen-15, nitrogen-13 and carbon-11 and of their low molecular weight derivatives for biomedical applications

Abstract The production and the medical use of the short-lived radioisotopes of the 3 major elements of the biosphere, 13N, 11C and 15O, require the vicinity of a cyclotron, of radiochemistry laboratories and of a suitably equipped medical unit. The authors describe and discuss the methodological and practical aspects of the routine, high efficiency, production of these gases, with the specifications that result from their medical use.

Automated preparation of carbon-11 ethanol and carbon-11 butanol for human studies using positron emission tomography

An automated continuous flow process has been developed for the synthesis of11C-ethanol and11C-butanol. These alcohols were synthesized via the same route. The reaction of11CO2 with methylmagnesium bromide or with n-propylmagnesium chloride, followed by a lithium aluminum hydride reduction and hydrolysis produced respectively11C-ethanol and11C-butanol. Preparation can be completed in 25 min. In each case the radiochemical purity, as determined by high pressure liquid chromatography /HPLC/ was greater than 98%. Biological quality control shows that the products are suitable for human use. The process has been completely automated to limit radiation exposure to personnel, reduce preparation time, and increase reproducibility.

Precise determination of uranium in rocks and minerals by neutron activation analysis using 133I fission product

Abstract A radiochemical neutron activation technique for uranium determination in rock and mineral samples is presented. The method is based on an alkaline fusion, a selective oxidation of iodine by a sodium-nitrite solution, followed by an iodine distillation technique for the isolation of the 133 I produced in fission. The outlined scheme is rapid, sensitive and reliable. Determination of uranium in U.S. Geological Survey standard rocks (G-1, W-1, G-2, BCR-1, AGV-1, GSP-1), C.R.P.G. Nancy geochemical standards (GA, GH, BR, Mica-Fe, Mica-Mg), C.A.A.S. reference syenite rocks (SY-1, SY-2, SY-3) and other analysed rock samples are reported. These results are compared with those obtained by other methods.

Determination du debit optimum pour la production par cyclotron de gaz radioactifs a partir de cibles gazeuses

Abstract When short-lived radioactive gases are produced by cyclotron-irradiated gaseous targets, the yield of activity at the site of delivery depends on the flow rate in the gas-carrying line. The authors present a single model which allows to compute the flow rate D giving a maximum yield of production. The following formula is used: D = 1 2 [λV r +√(λ 2 V r 2 +4λ 2 V r V c )] , where λ is the decay constant of the produced radionuclide, Vc the volume of gas in the target, and Vr the inner volume of the gas-carrying line. The only unknown parameter, Vr, can be derived from a single curve of growing of the activity at a trial flow rate. The method is concretely applied to the production of 15O, 13N and 11C.

Myocardial blood flow and glucose uptake after myocardial infarction

Position emission tomography can picture the distribution of flow tracers as well as of metabolic substrates or analogs. Studies of the distribution of these tracers allow to infer information about regional myocardial clearance (flow x extraction) and substrate utilization. In a study of 32 patients after myocardial infarction, we have contrasted flow and substrate utilization to demonstrate ischemic but viable myocardium in the arterial territory of the infarct in a number of patients also specially after fibrinolytic reperfusion. Restoration of blood flow to the ischemic but viable myocardium through coronary bypass or dilatation improves flow from 56.3% to 84.2% of control and restores substrate utilization. In another group of 32 patients studied with the Strontium-82/Rubidium-82 generator, we have demonstrated perfusion changes both in the myocardial infarct area and at a distance. These changes predominate in patients with multiple vessel disease. Combined PET studies of flow and substrate utilization are new tools to study early intervention after myocardial infarction and to document the benefits of revascularization.

Production par cyclotron de gaz radioactifs à partir de cibles gazeuses: Inhomogénéité de l'activité dans la cible - débit optimum du gaz vecteur - sections efficaces

Abstract When short-lived radioactive gases are produced by cyclotron-irradiated gaseous targets, the yield of activity, at the site of delivery, depends on the flow rate in the gas-carrying line. The authors improve a preliminarily published previous single model by the introduction of a supplementary hypothesis which takes into account the inhomogeneity of the activity in the gaseous target. By substituting the NTP volume of the gas in the irradiation cell Vc by a visible volume Va depending on the flow rate and expressed by Va = V∞+(V0−V∞) exp(−kDp), they derive the following general expression for the optimum flow rate D which gives a maximum yield of production. D2−bD−bc−D2ak exp(−kD)−ab exp(−kD)=0, a = λ(V0−V∞), b = λVr, c = λV∞, λ = the decay constant of the radionuclide produced, Vr the inner volume of the gas-carrying line. The unknown parameters Vr, Va, V0, V∞, and k can be determined experimentally. The authors also suggest a new method for the determination of experimental cross sections with their gaseous target with the help of the following expression: σ =A(λV a +D) exp (λT p )/λFnR , where A is the saturation activity at the site of delivery; F, the intensity of charged particles; n, the atoms target concentration; R, the range of the particles; Tp, the transit time in the carrying line. The method is concretely applied to the production of 15-oxygen, 13-nitrogen and 11-carbon and the average cross sections are determined in precise energy ranges for the nuclear reactions 14N(d, n)15O, 12C(d, n)13N and 14N(p, α)11C.

Essai d'une cible de polyphenyle deutere sous faisceau de deutons

Resume A deuterated target of novel design has been developed. It is composed of a high polymer, the polyphenyl, in which deuterium forms an integral part of the molecule. As a first step before testing the target of tritiated polyphenylm this paper examines the behaviour of deuterated polyphenyl targets in a beam of deuterons for the production of 3 MeV neutrons according to the D(d, n) 3 He reaction.

A system for the disposal of large volumes of air containing oxygen-15

Abstract A method is described which permits large volumes of air containing the radionuclide 15 O to be vented into the atmosphere. The short half-life of this isotope (124 s) enables use to be made of a large number of small vessels connected in series. Such a device has the effect of increasing the mean transit time. The system as installed results in a reduction of the radioactive concentration in the vented air to levels below the maximum permitted values.

Determination of Regional Cerebral Glucose Transport and Utilization Rates in Man with 11C-Glucose: Preliminary Results

This paper describes the methodology and the first results of a method of measurement of the cerebral metabolic rate of glucose, using 11C-glucose and regional detection by probes. The pres