[Measurement of linear exposure nominal pose used in curietherapy]

The idea, and subsequent construction, of a dose rate meter for measuring linear exposure dose originated in those pilot centres of Curietherapie which wished to replace radium by the artificial radionucleides, Irdium-192, Caesium-137 etc. The aparatus makes it possible to measure, directly and quickly, the activity of a specified length of a linear source, a measurement which has only been possible until now by dividing the exposure dose by the length whose activity it is desired to know. If the dose-rate obtained by these two methods agrees, this apparatus shortens the time for which the sources need to be handled, thereby reducing the danger of irradiation to staff and technicians. The apparatus is thus able to reveal heterogeneity of activity along the length of a line-source. In the specific case of Iridium, our experience shows that wires which have been used in several applications may develop mechanical bends and constrictions, which can lead to fluctuation in dose rate along their length. The apparatus was first constructed in 1967, after preliminary experiments in 1965. As Curietherapy has become more widely used, the apparatus has undergone many modifications which is more precise and specific than it was initially. At the present time it can only be used with Iridium as wire, and with Caesium in the form of trains of seeds (corresponding to the AGS sources) or needles. Nevertheless, a third scale is under consideration, for use with newer radioelements, which may be used in future.

Recombination of carbon monoxide with hemoglobin after flash photolysis of the carboxyderivative in mixed solvents at subzero temperature

The kinetics of recombination of carbon monoxide to hemoglobin produced by total flash photolysis of its carboxyderivative are studied at low temperatures (down to --55 degrees C) in mixed hydroalcoholic solvents. The rates are found to be different in two solvents used, namely ethylene glycol/buffer and methanol/buffer; for the former, the rates at subzero temperatures are simply explained by cooling and are consistent with the activation energy as measured in aqueous solution, while those in methanol/buffer show evidence of a specific solvent effect. Values are reported for the rate constants and activation energies in the two solvents.