Radiation safety in PET

Abstract

Positron emission tomography (PET) is an integral part of nuclear medicine diagnostics. In the future an increase in the application of this method in general health care can be expected. Compared with conventional nuclear medicine, a number of factors relating to radiation safety in PET have to be taken into account:

• The energy of the annihilation photons of 511 keV is much higher than the photon energy of radionuclides used in conventional nuclear medicine, especially 99mTc. As a result of the higher photon energy the attenuation is lower, and this must be considered in the calculation of necessary radiation shielding.

• Due to the short half-life of certain radionuclides commonly used in PET, it is necessary to produce and carry out the radiochemical preparation of these radionuclides at the location of their use. The radiochemical preparation, and also the application of the radionuclides involves working with relatively high levels of activity.

• During production of radionuclides with a cyclotron, fast neutrons can be produced in nuclear reactions as well as components of the equipment used can be activated. High-energy primary and secondary gamma radiation can be released in nuclear reactions.

• During procedures associated with the preparation of radioisotopes, volatile radioactive substances are produced, which lead to contamination of the air exhausted from the cyclotron room and also from the corresponding synthesis units of the radiochemical laboratory.

• Quantitative PET studies involve temporal blood sampling. This entails an additional radiation exposure to personnel.