The absolute activity of tritium was measured by liquid scintillation counting using a simplified efficiency tracing method in which60Co and 14C of known activities were employed as tracers. The activity of a tritium standard solution obtained from the Radiochemical Centre, U.K. was measured by this method within 1% of its original certified value.
Streptococcus faecium A2l, Bacillus sphaericus CIA and spores of a strain classified as Bacillus cereus S6 were chosen as test strains for the control of radiosterilization procedure of disposable medical equipment. The biological indicators from these three microorganisms were used for comparison of the microbiological efficiencies of three cobalt 60 plants (Japanese 2, Danish 1) . Identical doses of ionizing irradiation given at these plants have the same microbiological effect. We recommend a minimum dose of 4.5 Mrad, if the contamination on the medical equipment to be sterilized is not known. If the initial count is known, we can compute a sterilization dose by means of the standard inactivation curves for above three strains.
Pulmonary function of 85 cases was studied by a scintillation camera to visualize as well as to record pulmonary uptake and clearance of133Xe administered either by inhalation or by intravenous injection. To observe ventilation of the lung, xenon gas was administered into spirometer and breathed by the patient in a closed system. By breathing the room air after continuous breathing of xenon-oxygen mixture, the xenon was washed out from the lung of the patient. During these times, several serial scintiphoto grams and counting rate were obtained. Likewise, to observe pulmonary perfusion, serial scintiphotos and measurement of radioactivity were obtained over the lungs, at first during breath holding after intravenous injection of133Xe dissloved in saline, and then during normal breathing, the133Xe being washed out from the alveoli. These serial scintiphoto grams, using133Xe and scinticamera, provided a relatively simple means of measuring regional pulmonary arterial blood flow and ventilation. And these methods proved helpful in detecting regional ventilation and perfusion unbalance, and in observing disturvance of gas movement in obstructive disease of the lung.
We performed the comparison of liver scintigram using radioactive technetium heptasulfide (99mTe) -colloid with that using radioactive gold (198Au) -colloid against the cases where remarkable alteration or variation was observed at the time of operation, biopsy or autopsy. Fifty percent of entire cases reflected well patho-morphism alteration when198Au-colloid was used. While, it was 54%, when99mTc2S7-colloid was employed. On the other hand, the rate of erroneous diagnosis was 8% in the former case, and in the latter, it was 3.8%. Both types of liver scintigrams are more effective in order for observing constitution, shape, splenic shadow and blood clearance (Kv) . And, any significant difference of effects was not marked between these two types of liver scintigrams. However, in the respect of dose, 99mTc2S7-colloid is more advantageous than198Au-colloid, since it produces sharp scintigram with much less radiation dose.
198Au has been widely used for liver scintigraphy till now. However, as for detective capacity of liver tumor, 99mTc is proved to be the better by the simple phantom experiment. As a result of liver scintigraphy with99mTc2S7-colloid for 52 clinical examples, very fine scintigram was obtained without any side effect. The detective capacity of intrahepatic tumor becomes higher. That is, by using scinticamera, very good scintiphoto can be obtained dosing 3-6 mCi of99mTc2S7-colloid under the condition of stopping the breath for only 10-20 sec. Liver scintigraphy of99mTc2S7-colloid shows the remarkable accumulation of99mTc to spleen, so it is meaningless to talk about the existence (or non-existence) of spleen image as a symptom of disease. Nevertheless, 99mTc2S7-colloid will give a useful information for diagnosis of splenomegaly, because it provides a clear spleen figure in liver cirrhosis, in Banti's disease, etc.
Absorption, distribution, excretion and metabolism of3H-l-1- (3, 4, 5-trimethoxybenzyl) -6, 7-dibutyryl-1, 2, 3, 4-tetrahydroisoquinoline (3H-BAQ-509) and3H-l-1- (3, 4, 5-trimethoxybenzyl) -6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline (3H-AQL-208) in the rat were investigated. When these compounds were orally administered in a dose of 12.5μmoles/kg, BAQ-509 was absorbed more easily than AQL-208. The absorption half-life of BAQ-509 was 80 minutes and that of AQL-208 was 190 minutes. Radioactivity (3H) in each tissue was the highest at one hour after administration of both drugs. When BAQ-509 was administered orally, almost all of the radioactivity in each tissue were found to be due to AQL-208 and its metabolites. The concentration of AQL-208 in the blood, liver, kidney at 20 minutes was 2-11 times higher after administration of BAQ-509 than after administration of AQL-208. Sixty seven per cent of the administered radioactivity of3H-BAQ-509 was excreted in 48 hour-urine and 29% in 48 hour-feces. It was found that BAQ-509 was hydrolyzed, then was metabolized by either O-methylation or conjugation with glucuronic acid like AQL-208 was metabolized. Of the radioactivity excreted in the 4 hour-urine of rats given3H-BAQ-509, the largest part (69.3%) was the glucuronide of AQL-208 and 29.3% was the glucuronide of O-methylated AQL-208. In vitro study of esterase activity showed that the maximum velocity (v max) of esterase in the blood, small intestine and liver homogenates were 1 μmole per minute/ml, 80 μmole per minute/g and 110 μmole per minute/g respectively.