Radiological protection of patients in nuclear medicine

The key factor in medical exposure is justification, that is ensuring that the benefit exceeds the risk. Nuclear medicine studies are comparable in cost to more sophisticated radiological tests such as ultrasound, computed tomography or magnetic resonance. Radiation doses are similar from X ray and nuclear medicine procedures. Having justified exposures the next step is optimization, namely using a radiation dose as low as is reasonably practicable. Diagnostic reference levels may be set nationally or locally such that the balance of diagnostic quality and radiation burden is optimized. In therapy the aim is to achieve a therapeutic dose while keeping the dose to non-target tissues as low as reasonably practicable. Variations in activities may be required for overweight patients, those in severe pain, those with certain conditions and in the case of tomography. Any woman who has missed a period should be assumed to be pregnant; there should be notices to patients emphasizing this. Following the administration of longer lived pharmaceuticals it is important to avoid pregnancy for a time such that the dose to a foetus will not exceed 1 mGy. A similar situation applies to a child who is being breastfed when a mother receives a radiopharmaceutical. In the case of children undergoing investigations the activity needs to be reduced to maintain the same count density as in adults. With the administration of an incorrect pharmaceutical an attempt should be made to enhance excretion, and the referring doctor and the patient should be informed. Extravasation usually requires no action. Positron emission tomography results in higher doses both to staff and patients. Research should use subjects over the age of 50, and avoid anyone who is pregnant or is a child. Nuclear medicine procedures result in a very small loss in life expectancy compared with other common risks. (author)