ABSTRACT
The use of ionizing radiation for diagnostic imaging requires careful thought and handling so that maximum benefit can be obtained for minimum risk. Its use has increased dramatically over the last decade; more and more people are being exposed to medical X-and gamma radiation. Figure 21.1 shows the rapid increase in their use over the past 100 years. Increased machine sensitivity has lowered the dose in diagnostic imaging but exposure even from low levels of radiation is still an unknown risk especially when applied to larger and larger numbers in the population. Although a great deal of knowledge exists about the risks of high radiation levels, extrapolation to low doses is fraught with complications.
