For diagnostic procedures, the nuclear medicine specialist, in cooperation with the medical physicist, must determine the optimum activity to administer for a given examination. This decision should take into account the relevant Diagnostic Reference Levels (DRL) as well as the following factors:
The diagnostic value of the information obtained from an examination will vary with the amount of administered activity. There is a threshold of activity below which no useful diagnostic information can be obtained. Above this threshold, the diagnostic quality improves significantly with increasing activity. However, once the acceptable image quality is achieved, further increases in administered activity will only result in a higher absorbed dose without improving diagnostic quality.
Limiting the administered activity below the optimum level may lead to poor quality results and potentially serious diagnostic errors. It is crucial to avoid insufficient activity that may result in unnecessary irradiation and the need to repeat the test.
If multiple radiopharmaceuticals are available for a procedure, factors such as the following should be considered to minimize the absorbed dose and other risks while providing the desired diagnostic information:
It is also important to ensure that the radiopharmaceuticals used are from approved manufacturers and distributors and produced according to national and international standards. This applies even to in-house production of radiopharmaceuticals for PET studies.
The administered activity to a patient should always be determined and recorded. This information is essential for estimating the absorbed dose to various organs and calculating the effective dose to the patient.
Simple measures can significantly reduce the absorbed dose from radiopharmaceuticals, such as: