Question 30.CA.3: Absorbing radiation Suppose a person who has one hand in a w...
Absorbing radiation
Suppose a person who has one hand in a wide beam of x rays receives an equivalent dose of 90 millirem in 30 s. If the person puts both hands in this beam, side by side, for 30 s, then the equivalent dose the person will receive is
A. 180 millirem, because twice the number of ions will be created.
B. 90 millirem, because the number of ions created per gram is unchanged.
C. 45 millirem, because the radiation is spread over twice as much of the body.
The millirem is related to the number of molecules ionized by radiation in 1 gram of tissue. So, whether your body receives an equivalent dose of 90 millirem to the tip of your finger or 90 millirem to the whole body, the dose is the same. The correct answer is B. However, the number of ions created in the body and the possible destructive effects, and the potential for cancer, are vastly different for the two cases.
Any time you receive ionizing radiation (such as that from diagnostic x rays), the area exposed should be kept as small as possible.