Radiation doses in computed tomography

Computed tomography has made dramatic advances, both in its breadth of application and in its technological improvements. The advances are such that it is possible with the spiral technique to carry out an entire examination of the chest within a single breathhold as against a few minutes in earlier systems. Yet these advances have brought with them the potential for greatly increased doses of radiation to the patient. Until a few years ago computed tomography constituted about 2-3% of all radiological examinations but contributed about 20-30% of the total radiation load from medical use of ionising radiation.1 2 A recent report from the Royal College of Radiologists in the United Kingdom states, “CT now probably contributes almost half of the collective dose from all x ray examinations.”3 Although magnetic resonance imaging was expected to reduce the frequency of computed tomography, this has not happened. Indeed, the use of computed tomography has grown. It is now often used as an adjunct to radiotherapy or chemotherapy; interventional procedures use computed tomography …