J.C. Depresseux

Spatial Distribution of Blood Flow in Electrically Stimulated Human Muscle: A Positron Emission Tomography Study

Neuromuscular electrical stimulation (NMES) was studied with positron emission tomography (PET) and H215O in the quadriceps muscle of 11 men. The subjects were submitted to simultaneous bilateral isometric contraction (5 s)–rest (5 s) cycles for 12 min, with a workload corresponding to 5% of quadriceps maximal isometric voluntary torque (QMIVT) for one thigh (5%T) and 10% of QMIVT for the other (10%T). Scans were centered at the electrodes and tissue blood flow (TBF) was evaluated in square regions of interest (ROIs) (3.5 cm2) in the transverse section (TS) of both thighs. The mean TBF reached 8.9 mL min−1 100 g−1 in the TS of the 5%T and 11.5 mL min−1 100 g−1 in the TS of the 10%T (P > 0.05). A negative linear relationship was found for both thighs between the ROI–electrode distance and the TBF (P ≤ 0.009). The mean percentage of activated ROIs (TBF > 5 mL min−1 100 g−1) was lower in the 5%T than in the 10%T (50.6% vs. 62.2%; P = 0.017). With NMES, the pattern of spatial recruitment appears linked to electrode proximity and is spatially extended. These results confirm the utility of combining NMES with voluntary exercise in the treatment of atrophied muscle.

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.

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.

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.

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

Preparation of iodine-123 from gaseous tellurium hexafluoride targets

Abstract The reactions 122 Te ( 3 He , 2n) 123 Xe and 123 Te ( 3 He , 3n) 123 Xe 123 I are very attractive provided one can separate the xenon-123 from the matrix. In principle, this would lead to very pure iodine-123 by the use of enriched tellurium with the 122- or 123-isotope. So far only methods relying on the diffusion phenomena to extract the xenon from enriched tellurium solid targets have been used. To avoid the drawbacks of such targets we tried using a gaseous target. Telllurium hexafluoride behaves perfectly well under the helium-3 beam. The yields of 123-iodine are of the same order as the best ones obtained from the so-called “cyclic method”, typically 20 μCi/μAH starting from natural tellurium including less than 1% of contaminating 121-iodine. This will be improved by refining the separation with the adjustment of a tested technique.