Information Notice 2001-08, Supplement 2: Update on Radiation Therapy Overexposures in Panama

WASHINGTON, D.C. 20555-0001

November 20, 2001

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All medical licensees.


The U.S. Nuclear Regulatory Commission (NRC) is issuing this supplement to information notice (IN) 2001-08, to provide additional information related to the radiation therapy overexposures that recently occurred in Panama. All persons in your institution who are involved with radiation therapy should review this notice. It is expected that recipients will review this information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this IN are not new NRC requirements; therefore, no specific action nor written response is required.

Description of Circumstances

Panama, involving radiation overexposures of 28 teletherapy patients, resulting in multiple deaths. The International Atomic Energy Agency (IAEA) recently published its report entitled "Investigation of an Accidental Exposure of Radiotherapy Patients in Panama," which concluded that the cause of the radiation overexposures was the way the shielding block data were entered into the computerized treatment planning system. The report is available from IAEA, and can be ordered from its web site at:

The company that supplied the treatment planning software, Multidata Systems International Corporation (Multidata), in St. Louis, Missouri, issued a "Medical Device Safety Alert" on June 22, 2001 (Attachment 1), and an "Urgent Notice" on August 10, 2001 (Attachment 2). The "Urgent Notice" explains that certain improper data entries will be accepted by the software, but will result in incorrect dose calculations. Multidata is developing a "filter program" to address this problem.

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According to the IAEA report, one method the Panamanian hospital staff used for the data entry of shielding blocks caused the treatment planning system to calculate incorrect treatment times.

Specifically, the staff modified its procedures and entered data for multiple shielding blocks together ("digitized" the blocks), as if they were a single block. The data were accepted by the treatment planning system, but the software calculated incorrect treatment times. Using incorrect treatment times resulted in significant radiation overexposures to patients. The hospital staff did not perform independent verification of the computer-calculated treatment times, so the errors were not identified before treatment. The IAEA report states that there were several characteristics of the computerized treatment planning system that made it relatively easy for the error to occur. These were:

  1. Several different ways of digitizing blocks were accepted by the computer treatment planning system;

  2. There was no warning on the computer screen when blocks were digitized in an unacceptable way (i.e., any way that is different from the one prescribed in the manual); and

  3. When blocks were digitized incorrectly, the treatment planning system produced a diagram that was the same as that produced when the data were entered correctly, thereby giving the impression that the calculated results were correct.

The "Multidata Medical Device Safety Alert," dated June 22, 2001, urges customers to follow the instructions in the user manual, and emphasizes that users should not attempt to operate the system outside the limitations stated in the user manual.

All persons involved in radiation therapy are encouraged to review both the information related to this incident, and your treatment planning procedures, to ensure that both your procedures and written quality management program, required by 10 CFR 35.32, are adequate to avoid similar radiation therapy errors. The event in Panama demonstrates that licensees should always be alert to the possibility of introducing unintended errors into the treatment planning process. In particular, note the importance of independent verification of computer-generated patient treatment plans.

In addition, if you are a Multidata customer, you should have received notices from the firm about this incident. If you have not received the attached communications from Multidata, you should contact its Helpdesk at 1-800-225-1130 or

The U.S. Food and Drug Administration (FDA) is investigating this incident, and NRC is cooperating with its investigation. Often device users are the first to discover problems with marketed medical devices. If you encounter device malfunctions or product problems involving radiation therapy devices or radiation therapy treatment planning systems, particularly those that may be software related, you are strongly encouraged to report such events to MedWatch, the FDA's voluntary reporting program. You may submit voluntary reports to MedWatch through:

  • Phone at 1-800-FDA-1088;
  • FAX at 1-800-FDA-0178
  • The Internet at ; or,
  • Mailing your report to MedWatch, Food and Drug Administration, 5600 Fishers Lane (HF-2), Rockville, MD 20857.

Also note that under the Safe Medical Devices Act of 1990, user facilities must comply with specific, mandatory reporting time frames and requirements, when they become aware that a medical device may have caused, or contributed to, a patient death or serious injury/illness.

Questions concerning FDA's mandatory user facility reporting requirements can be directed to FDA's Center for Devices and Radiological Health, Office of Surveillance and Biometrics, through telephone at (301) 594-2735.

This IN requires no specific action nor written response. If you have any questions about the information in this notice, please contact one of the technical contacts listed below, or the appropriate NRC regional office.

  Donald A. Cool, Director
Division of Industrial and
     Medical Nuclear Safety
Office of Nuclear Material Safety
     and Safeguards
Technical Contacts: Robert Ayres, NMSS
Donna-Beth Howe, NMSS
(301) 415-7848
  Roberto J. Torres, NMSS
  1. Medical Device Safety Alert, June 22, 2001
  2. Urgent Notice, August 10, 2001 (Page 1 | Page 2)
  3. List of Recently Issued NMSS Information Notices
  4. List of Recently Issued NRC Information Notices

(ADAMS Accession Number ML012390161)

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