Question

With what energy must the radiation be given to image a bone of thickness 5 cm which has covering of skin of thickness of 2 cm on the both sides and the emerging intensity of the X – Ray is 200MeV. (impedance for bone = b  for skin = s )

(a) 2000e^9

(b) 200e^(4s + 5b)

(c) 20/e

(d) 2e

The question was posed to me during an interview.

Question is taken from Diathermy, Measurement of Radiation, Dose and its Calculations topic in chapter Radiation Therapy of Clinical Science

Answer 1

Correct choice is (b) 200e^(4s + 5b)

The explanation is: The formula goes like : I = I0e^(-μt) where I is the final radiation, I0 is the initial radiation, μ is the impedance and t is the thickness. Since we know the emerging radiation, by using back processing formula, we get 200e^(4s+5b).