^99mTC has a half-life of 6.02 hours. It decays into ^99Tc by emitting a gamma r
ID: 2021317 • Letter: #
Question
^99mTC has a half-life of 6.02 hours. It decays into ^99Tc by emitting a gamma ray, with energy 140keV for this problem, assume that ^99mTc is present in the body for 2 hours after being injected and then is immediately removed.Already calculated:
total energy E released by decays in the 2 hours: 0.081J
if that amount was given to an 80kg man, and it stayed in his system for 2 hours, absorbed dose would be : 0.10 rad
1- Equivalent dose correlates strongly with the biological effects of radiation. Calculate the equivalent dose, keeping in mind that ^99mTc emits gamma rays. (answer in rems)
2- How would the equivalent dose change if emitted a beta ray of the same energy?
3- How would the equivalent dose change if this quantity of ^99mTc had been administered to a small dog of mass 2kg ?
Thank You!
Explanation / Answer
1. rads = rems so =0.1 2. The equivalent dose slightly increase. Equivalent dose correlates very strongly with the amount of damage done. The relative biological effectiveness (RBE), which is 1 for gamma rays and a bit more than 1 for electrons, is multiplied by the absorbed dose to account for the fact that some types of radiation do more damage to tissue than others at the same energy. Alpha particles have an RBE of 20 because they tend to deposit all of their energy in a small area, thereby causing substantial damage to a few cells. 3. The equivalent dose would increase by a factor of 40. Government regulations suggest that it is mildly unhealthy to receive an annual equivalent dose of , though workers with occupational exposure to radiation are allowed up to per year. Clearly, it would be quite safe for a person to have several of the scans described in this problem during a year, though a lower dose of would be advisable for small dogs.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.