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Therapy Medical Events

The Radiation Safety Section (RSS) is providing the following summary information of therapy medical events in Michigan. Medical event information involving the use of radioactive materials is maintained by the U.S. Nuclear Regulatory Commission (NRC). A NRC Information Notice regarding medical events related to gamma stereotactic radiosurgery can be found on their website.

The conditions requiring a report of a "therapy medical event" are:

Except for an event that results from patient intervention, the registrant shall report in writing within 30 days to the Department any event from the administration of therapeutic radiation that:

  • Results in the total dose delivered differing from the prescribed dose by 20% or more; or
  • Results in any single delivered fraction of a fractionated treatment exceeding the prescribed dose by 50% or more; or
  • Involves the wrong patient, wrong treatment modality, or wrong treatment site.

The following table shows the number of reported misadministrations/therapy medical events for the last 10 years that met the criteria above. A summary of each event can be observed by clicking on the year in the following table. The RSS is providing this information in an easily accessible form for interested citizens of the state. The RSS believes that operators of therapy radiation machines may also benefit from this information. No patient or facility information is provided. The RSS does not track the total number of therapy treatments or patients. 


Total Number of Medical Events























Therapy Medical Events Q&A and Definitions


Patient intervention means any action by the patient, whether intentional or unintentional, during the administration of radiation therapy which causes interference.

Prescribed dose means any dose, including the dose per fraction and the total dose, as documented in the written directive.

Treatment site means the anatomical description of the tissue intended to receive a radiation dose, as described in a written directive.

Treatment modality means the type of radiation beam used such as photons, electrons, or particles.

Written directive means a written order for the administration of therapeutic radiation to a specific patient or human research subject. Patient means an individual subjected to machine produced radiation for the purposes of medical therapy.


Even if none of the dose criteria are exceeded, must an event be reported if the wrong patient is irradiated?

Yes. If the wrong patient is irradiated, the facility must report the event.

What defines a "wrong treatment site"?

Any site other than the site as described in the written directive. If a "geometric miss" occurs (Prescribed tumor volume is not irradiated), it must be reported. It is recognized that body parts that are adjacent to the treatment volume will be exposed to radiation, but this is not a reportable event.

If the treatment course terminates prior to the completion of 80% of the dose, is this a reportable event?

A reportable medical event is meant to be an event that occurred due to treatment errors. If treatment is terminated due to patient death, patient choice, patient transfer to a different institution, or because of a medical decision by the physician, it is not a reportable event but the facility should note the reason in the patient's record.

How should the facility notify LARA of a therapeutic medical event?

The facility must report the event in writing to the department within 30 days. The report may be sent by mail, e-mail, or fax. The report should include the information as outlined in form MIOSHA-RSS-115, Reporting Guideline: Example Format for Therapeutic Machine Medical Events. Other formats are also possible and acceptable.

Last Update: 11/19/2018