xtr32.19 - Therapeutic Uses of lonizing Radiation A cancer patient is exposed to

Question

xtr32.19 - Therapeutic Uses of lonizing Radiation A cancer patient is exposed to y rays from a 5200-Ci 60Co transillumination unit for 47.0 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 1.80 kg. What is the dose in Sv to the tumor, if the average y energy per decay is 1.37 MeV? None of the B s from the decay reach the patient. Is the dose consistent with stated therapeutic doses? Yes No Submit Answer Tries 0/10

Explanation / Answer

Solution:

a) 5200 Ci = 5200 * 3.7 * 10^10 decays / s              ( 1 Ci = 3.7 * 10^10 decays / s)

=> for 47 seconds decays,

=> 5200 * 3.7 * 10^10 * 47

=> 9.04280 * 10^15 decays

Now total energy for the decays

=> Energy = 1.37 * 1.6 * 10^-13 * 9.0428 * 10^15

=> Energy = 1.982 * 10^3

Now 1 % of 25 % of the energy will get absorbed in the tumor

=> Energy absorbed = 1.982 * 10^3 * 25 * 10^-4

=> Energy absorbed = 4.9554 J

dose in rem = 4.9554 /1.80 * 100 = 275.3 rem

now 1 rem = 0.01 Sv

Hence dose = 2.753 Sv ( answer)

b) No as dose is more than 100 rem

please rate thanks.

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