Radioactive tracers are used in imaging tests that help find
problems inside the body. These tracers give off particles that can be detected
and turned into a picture to help find problems in organs or other
The tracer is usually given through an intravenous (IV) line
placed in a vein. But the tracer also may be given by mouth or by inhaling it into the lungs. The tracer then travels through the body and may collect in a
certain organ or area.
The PDQ editorial boards use a ranking system of levels of evidence to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. For any given therapy, results of prevention and treatment studies can be ranked on each of the following two scales:
Strength of the study design.
Strength of the endpoints.
Together, the two rankings provide a measure of the overall level of evidence. Screening studies are ranked on strength of study design alone...