The quantity of a radioactive material is often measured by its activity (measur

Question

The quantity of a radioactive material is often measured by its activity (measured in caries or kilocuries) rather than by its mass. In a brain scan procedure, a 64.0-kg patient Is injected with 10.0 mCi of^99m Tc, which decays by emitting gamma-ray photons with a half-life of 6.01 h. Given that the RBF. of these photons is 0.98 and exactly two thirds of the photons are absorbed by the body, calculate the rein dose received by the patient. Assume all the^99m Tc nuclei decay while in the body. The energy of a gamma-ray photon is2.29 times 10^-14 J.

Explanation / Answer

1 mCi = 3.7E7 disintegrations/s

10 mCi = 3.7E8 disintegrations/s

6.01 h (3600 s / 1 h) = 21636 s

Energy radiation absorbed: (3.7E8 disintegrations/s * 21636 s)(2.29E-14 J)(2/3)

= 0.122214552 J

radiation dope = radiation absobed per Kg = > (0.122214552)/(64) = 0.001909602375 gray = 0.1909602375 rad

effective radiation dosage (rem) = 0.1909602375 * 0.98 =0.187 rem

Answer:  0.187 rem

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