Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive so

Question

Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive source is placed inside a patient's body to treat cancer. Brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. Iridium-192 is often used in the head or breast. Answer the following three questions (a, b, and c) based on the radioactive decay curve of iridium-192, shown below. Click on the graph and move the mouse over a point to get values for that point.

Explanation / Answer

1) after 150 days 25% is remaining(from the graph)

100% means----------------------------3.50 grams

25% menas---------------------------------------------?

=25*3.50/100

=0.875 grams

2) 0.693/t1/2= (2.303/t) log(a/(a-x)

   0.693/t1/2= (2.303/24*150*60*60)log(3.50/0.875)

t1/2= 6524584.03seconds=1812.38hours=75.5 days

3)      to complete 3/4th decay =3/4*t1/2=3/4*6524584.03=4893438.0225 secods

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