Gadolinium-153
Gadolinium-153 is a low-energy gamma-emitter with an 8-month half-life. It is used in many quality assurance applications, such as line sources and calibration phantoms, to ensure that nuclear medicine imaging systems operate correctly and produce useful images of radioisotope distribution inside the patient. Gadolinium-153 is produced in a nuclear reactor from elemental europium or enriched gadolinium targets.

Gadolinium-153 helps calibrate positron emission tomography (PET) systems that are used in nuclear medicine for functional imaging. This PET image of the human brain shows the difference between a normal brain and the clinically depressed patient. The blue color indicates less glucose metabolism in the brain characteristic of a matched normal control. The green, yellow, and red colors indicate areas of higher glucose metabolism characteristic of a clinically depressed patient.