Jack L. Coffey

Calculating dose from remaining body activity: a comparison of two methods.

Two methods for calculating the radiation dose from remaining body activity have been suggested. One requires correction of the cumulated activities so that they reflect the activity uniformly distributed in the total body. The other method requires correction of the S values so that a value of S for the target organ from the remainder of the body is obtained. These two methods give the same answer. We have examined these methods and the number of steps required to calculate the radiation dose in each case. Our results show that the method of correcting the cumulated activities is preferred, especially if the number of source and target organs is large and a computer equipped with the necessary software is not available.

Some factors affecting the cerebral and extracerebral accumulation of N-isopropyl-p-iodo-Amphetamine (IAMP)

The whole body distribution of IAMP was studied in mice, rats, rabbits, dogs and marmosets by tissue counting, scintigraphy and quantitative macroautoradiography. Identical distribution patterns of IAMP were observed in these species showing high concentration in the brain, lungs, eyes, liver and kidneys. Following the initial distribution, IAMP was released from the lungs and accumulated in the blood and liver. In the cerebrum the activity decreased with time whereas it progressively increased in the eyes and juxtamedullary region of kidneys. The effect of ACTH, propranolol and metopyrone (metyrapone, USP) on the distribution of IAMP was studied in normal mice. The distribution of IAMP in Dahl salt-sensitive hypertensive rats was compared to Dahl salt-sensitive normotensive rats. Blocking doses of potassium iodide (KI) in marmosets and rats did not affect the distribution pattern of IAMP. Carrier amphetamine in doses of up to 1.5 mg/kg also did not significantly alter the biodistribution of IAMP. When higher doses (up to 8.0 mg/kg) were given, the activity in the gut, lungs, and liver decreased but there was no effect on the uptake in the brain, kidneys, eyes, adrenals, muscle and spleen. This suggests a higher ratio of saturable to nonsaturable binding sites in the latter organs.