One-pass method with a piecewise cubic polynomial was used as a smoothing technique in gamma ray spectrum analysis. By this method, smoothed results of spectrum region is represented to several divided intervals each of which are fitted with a cubic polynomial calculated by least square technique, respectively. From the smoothing procedure of simulated photoelectric peaks and actual gamma ray spectra, following results were obtained. Photoelectric peaks which had more than 10 channels of FWHM (full width at half maximum) were fitted correctly and low count spectra of about 100 counts per channel could also be fitted smoothly. These smooth results can not easily be obtained by Savitzky's convolution technique. In conclu-sion, this one-pass method was found to be effective for gamma ray spectra, especially for photoelectric peaks of large FWHM and Compton region.
In order to eliminate some drawbacks of thin detector with suitable window for measuring radiations of low penetrating power, the thermoluminescent LiF disc dosimeter was fabricated from phosphor of LiF with activators of magnesium and copper and inorganic binder of silica and alumina. The energy response of the LiF disc dosimeters to betarays was investigated by comparing with theoretical calculations and measurements with a parallel-plate ionization chamber. From the results obtained, the LiF disc dosimeter significantly underestimated the doses for low beta-ray energy (below 0.3 Me V), while its reading agreed well with the calculated ones for high energy (above 0.8 Me V) . Nevertheless, it is suggested that the fabricated LiF disc dosimeter is useful to evaluate the skin dose from the practical point of view, since beta-ray less than 0.6 MeV is completely absorbed before reaching the skin covered with clothing.
Instead of using the Medical Internal Radiation Dose Committee (MIRD) concept to calculate the gonadal dose during diagnostic examination using radiopharmaceuticals, measurements of gonadal doses using thermoluminescent dosimeters were studied. The results obtained are comparable with that calculated using the MIRD concept. Five frequently used examinations were investigated, viz., liver, brain, thyroid, bone scintigraphy and cholescintigraphy. The calibration of thermoluminescent dosimeters are fully described, and the experimental techniques are also fully presented.
A technique for the blood volume measurement of newborns was established in which non radioactive 50Cr was used in patients for whom radioactive labels were not advisable. The red blood cells (RBC) in the newborn's blood withdrawn from umbilical cord after birth were tagged with enriched stable isotope 50Cr (96%, normal abundance 4.3%) and reinjected into the newborn. Blood samples (0.5 ml) were withdrawn at 30 min and thereafter at 6, 12, 24, 48, 72 and 120 hours old. Samples were centrifugalized and portion of RBC was then freeze-dried, weighed and sealed into polyethylene sheet bag together with 50Cr standard. Neutron irradiation was per-formed in the reactors of the JAERI with thermal neutron flux 5×1013, 2×1013, 8×1013cm-2s-1at JRR - 2, - 3 and -4 respectively for 20 min and samples were left for about two weeks after irradiation. Induced radioactivity (51Cr, 59Fe) of the sample was measured with a Ge (Li) gamma-ray detector system and 4096 channels pulse height analyzer. Analysis of activity data was carried out by BOB - 76 code. The RBC and total blood volume of the newborn was calculated using an isotopic dilution technique. We have investigated on tagging efficiency of 50Cr to RBC, washing effect and dilution rate by 50Cr content or 51Cr/59Fe ratio. Significant difference was observed in the total blood volume of newborns depending on the delivery style and in addition, it changed dynamically along the time elapsed after birth.
In studies using 60Co gamma-ray irradiation, an extremely high dose rate is often required and samples must be placed very near a 60Co source. The dose rate in the vicinity of the source depends on the inner structure of the source. Therefore, it is necessary to examine the distribution of source activity. As a method of the examination an auto-radiographic technique using several coloring materials for irradiation was tried. The materials used were “Radcolor film” developed by our center, besides a glass, polymethylmethacrylate (PMMA) and a blue cellophane. Results showed that the autoradiography with Radcolor film is very useful to examine the position, the size and the activity difference of 60Co pieces by the change of color.