United States Nuclear Regulatory Commission - Protecting People and the Environment
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Backgrounder on Risks Associated with Medical Events

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Yttrium-90 microspheres deliver radiation directly to tumors
Yttrium-90 microspheres deliver radiation directly to tumors

The term "medical event" may sound alarming when it applies to nuclear medicine and radiation therapy.  But it does not always mean a patient has been harmed.  Rather, it refers to a potential problem with how a medical facility uses radioactive materials.

Nuclear Regulatory Commission regulations aim to assure radioactive materials are used properly in medical diagnosis, treatment and research. The rules are also meant to assure the safety of patients, medical workers and the public, and protect the environment.

Radioactive materials can be helpful to diagnose and treat illnesses or for medical research. Small amounts are used in creating images of certain organs. These images help physicians find, identify and measure tumors, or view problems in an organ's structure or function. Radioactive materials can also kill cancerous tissue, shrink a tumor or reduce pain.

For all medical uses of NRC-licensed radioactive materials, a "medical event" occurs if BOTH: 

  1. The dose administered differs from what was prescribed, and the difference meets the NRC's reporting requirements, AND

  2. One or more of the following representative incidents occur:

  • the dose given is off by at least 20 percent from the prescribed dose, either too high or too low,
  • the wrong radioactive drug is used,
  • the radioactive drug is administered by the wrong route,
  • the wrong individual receives the dose,
  • a dose is administered to the wrong part of the body and exceeds by 50 percent or more the dose that area should have received, or
  • a sealed source used in the treatment leaks.

Gamma Knife Focuses Tiny Beams of Radiation on a Tumor
Gamma Knife ® focuses tiny beams
of radiation on a tumor

The NRC requires reporting because a medical event shows the licensee had problems in administering the doctor's prescription. Dose errors may be a sign there are problems in the medical facility's operations that need correcting. The NRC analyzes each event to see if further action is needed. If there is a violation, the NRC might take enforcement action. We also look for trends to see if something in NRC's regulations or guidance may need to be clarified.

The doctor must also do an analysis to see if a patient is actually harmed, whether from too high a dose or inadequate treatment when a dose is too low. In severe events (for example, rare dose errors that are well over 20 percent too high or too low), an independent medical consultant will assess the patient's risk of harm. In all cases, a "medical event" indicates potential problems in a facility's use of radioactive materials. It does not necessarily result in harm to a patient.



Shielding and syringe holder used to protect medical workers as they load a syringe from a bulk vial of a radiopharmaceutical containing fluorine-18   Lead-shielded syringes, model PSV Courtesy of COMECER S.P.A.
Shielding and syringe holder used to protect medical
workers as they load a syringe from a bulk vial of a
radiopharmaceutical containing fluorine-18
 
    Lead-shielded syringes, model PSV
Courtesy of COMECER S.P.A.

April 2014

Page Last Reviewed/Updated Friday, May 16, 2014