An electrostatic potential meter on the basis of α-ray ionic current measurement was experimentally investigated, especially to have high position resolving power at the measurement. A rod-shaped probe of the potential meter, following a picoammeter, was topped with a thin cylindrical ion collector where a small241Am α-ray source of 0.93 MBq was mounted. The a-rays are emitted towards a charged material to be examined, and ionize air in a restricted region near the collector head. A movable shade electrode was also attached to the probe so as to surround the ion collector to extend and adjust measurable potential range. To design the probe of the potential meter, potential distribution inside the shade electrode was precisely examined in advance by the finite element method with a computer calculation. The sensitivity of the potential meter is adjusted by changing slightly the position of the shade electrode, since the electric field strength of the ionized region is strongly affected by the electrode position. The experiments employing charged plates of comb-shape showed that the potential meter with the shade electrode of 25 mm outside diameter has a resolving power of about 30 mm and is applicable for measuring potential up to 7 kV with relative error less than 5 %.
A new type of charged-particle imaging video monitor system was constructed for video imaging of the distributions of alpha-emitting and low-energy beta-emitting nuclides. The system can display not only the scintillation image due to radiation on the video monitor but also the integrated video image becoming gradually clearer on another video monitor. The distortion of the image is about 5 % and the spatial resolution is about 2 line pairs (lp) mm-1. The integrated image is transferred to a personal computer and image processing is performed qualitatively and quantitatively.
1-Acetoxyethyl 2- (2 fluoro-4-biphenylyl) [14C-methyl] propionate (14C-Me-FP 83) (1), a novel nonsteroidal antiinflammatory agent for injection, was synthesized in order to investigate the metabolic fate. 14C-Me-FP83 was obtained by the condensation of 2- (2fuoro-4-biphenylyl) [14C-methyl] pro-pionic acid with 1-chloroethyl acetate. The chemical yield of 1 was 62% after purification. The specific activity was 258 kBq/mg (6.99, uCi/ mg) and its radiochemical purity was 99% in thin layer chromatographic method.
The radiation absorbed dose was estimated for131I therapy of metastatic lesions of thyroid cancer, by the quantitative gamma-camera imaging. Uptake for eleven lesions in five cases (out of four patients) was measured for two times after131I administration. Activities were calculated from opposed images with corrections for distance and depth using empirical formulae. An activity time curve was assumed as a reminder of two exponentials and fitted to measured values. The sizes of lesions were evaluated using the multi-slice CT images. An increase of frequency of activity measurement, particularly within a few days after131I administration is desirable, for the purpose of an improvement of accuracy of dosimetry.
The adsorption behavior of60Coon sand has been studied under various conditions. The amount of adsorption obeyed the Henry adsorption isotherm in concentration range of 10-14-10-10mmol/ml and the Freundlich adsorption isotherm in concentration range of 10-9-10-2mmol/ml. The distribution coefficient became to a maximum value under neutral region, but fell to a value less than 1- 2 order under acidic and alkaline region. The distribution coefficient measured under aerobic condition was larger than that under anaerobic condition in acidic region, but was smaller than that under anaerobic condition in alkaline region. The distribution coefficient measured at temperature of 10-50 °C was proportional to reciprocal temperature. Influence of co-existent ion was not observed in co-existent ion concentration less than 10-4mmol/ml, but was confirmed in coexistent ion concentration more than 10-3mmol/ ml.