Question

# Below are data from the research study done on 28 individuals. Each individual was injected with...

Below are data from the research study done on 28 individuals. Each individual was injected with a dose of iodine-131 with an initial count rate of 18 000 cpm. The averaged daily count data for all 28 individuals appears in the table. Make a graph of the data and answer the following questions:

a) What is the effective half-life of I-131?

b) What is the biological half-life of I-131?

[NOTE: Day 0 is pre-injection count rate (i.e background).]

 Day Avg. CPM 0 50 1 10610 2 8040 3 6093 4 4618 5 3500 6 2653 7 2010 8 1523 9 1154 10 875 11 663 12 502 13 380 14 289 15 219 16 166 17 127 18 95 19 72 20 55

Graph Shows the daily average count of iodine along the y axis, plotted against the number of days in the x axis

Half Lives:-

Physical Half Life is the time for a quantity of radioisotope to decay by half.

Physical Half Life of IODINE – 131 is 8.1 days

Biological Half Life is the time for half of the amount of radionuclide to be expelled from the body.

Biological Half Life of IODINE – 131 is 138 days

Effective half life takes into account both physical and biological half.

Effective Half Life of Iodine – 131 is 7.60 days