ABSTRACT
References ............................................................................................................ 261
Better outcomes in health care rely on better diagnosis. Both radiology and nuclear medicine at present play an integral role in standard diagnostic procedures. There have been successes in the development of imaging modalities that do not use ionizing radiation: ultrasound and magnetic resonance imaging (MRI) are excellent examples. However, these imaging modalities typically complement those based on radiation: x-ray contrast is based on electron density and atomic number, while MRI shows proton density and the physical and chemical environment of these protons. Having more than one imaging modality available allows for differential diagnoses. It is therefore not surprising that the number of computed tomography (CT) scans per head of population has increased dramatically over recent years.1,2 Other aspects that contribute to the increase in medical exposure from diagnostic use of x-rays are developments such as four-dimensional (4D) CT scanning3 and increasingly the use of interventional radiography.
