Question

In Chinese hamster cell colonies it was found that the inactivation constant in the MTSH model is approximately 3.125 Gy-1 if 250 kVp X-ray is used. If Co-60 gammas are used to produce the same biological end point, the required dose is 160 cGy. It is further known that the biological effectiveness of neutrons at this endpoint is 4.0. What is the biological effectiveness of the Co irradiation with respect to the neutron irradiation

Answer 1

Answer: A. 20

Step-by-step explanation:

Radiation dose = 160 cG, or

Radiation dose = 160 x 10-2 G

Radiation dose = 1.6 G

The relative biological effectiveness (RBE) on neutron irradiation is then calculated with the formula:

RBE of Co-60 = inactivation constant x dose x neutron irradiation

getting:

Co-60 RBE = 3,125 x 1.6 x 4

Outcome:

RBE of Co-60 = 20

which shows that option A is correct