Nuclear medicine tests do expose patients to radiation, which can be dangerous, the radiotracers use such small amounts of radioactive materials that the potential benefits typically far outweigh the potential risks.

The amount of radiation that a patient is exposed to is similar to those of other diagnostic scans, and even in a patient's day to day, they are always exposed to certain small amounts of radiation. 
Nuclear medicine risk are small, and the benefits are invaluable. These tests provide functional and anatomic information that is unattainable in other procedures. Oftentimes, nuclear medicine tests provide doctors with the most useful diagnostic information, and the most helpful information to determine a course of treatment. PET scans can tell whether tumors are malignant or benign and can prevent a patient from getting a more dangerous or more costly surgery. 

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