Question

(a) A cancer patient is exposed to y rays from a 5200 Ci 60 Сo transillumination unit for 31.0 s. The y rays are collimated in such a manner that only 1.00% of them strike the patient. Of those, 20.0% are absorbed in a tumor having a mass of 1.45 kg. What is the dose in rem to the tumor, if the average y energy per decay is 1.25 MeV? None of the B s from the decay reach the patient. rem

Answer 1

Given,

The activity of the cobalt element source A=5200 co

t= 31 sec

E = 1.25 MeV

Amount of gamma ray strike g= 0.01

Amount of Ray's absorbed is r = 0.2

Mass of tumor = 1.45 kg

Expression for the dose

D = (A×t×E)/m

= 5200× 3.7 × 10¹⁰×31sec× 0.2× 0.01×1.25 x 10⁶ev ×1.6 × 10^-19

= 1.645 sv

= 164.5 rem. (Ans).