The following report was received via e-mail from the State of Minnesota:
Event description: The Minnesota Department of Health was notified on June 15, 2010 at 3:40 p.m. [CDT] of a medical event involving a gamma knife treatment at the University of Minnesota Medical Center - Fairview, University Hospital, Minneapolis. The total treatment consisted of 10 exposures, and was scheduled between 11:30 a.m. and 1:30 p.m. on Tuesday, June 15th.
Five automatic positioning system (APS) shots were completed successfully, and then the treatment called for 5 additional trunnion exposures. The first trunnion exposure called for a setting of 76.3, 86.5, 148.1 in the X, Y, and Z directions, respectively. Instead, the settings of 76.3, 86.5, 76.3 were used. In effect, the X setting was inadvertently used for the Z setting. The error was noticed when the coordinates for the second trunnion exposure were being set up. The Z coordinate value used for the first shot was very different from the Z coordinate for next exposure.
A new treatment plan was run to determine the dose and the location of the unintended exposure delivery. This plan showed a dose of 3.2 Gy (320 rad) to be delivered to a volume of 0.62 cubic cm at the unintended location. The original plan was re-exported to the GK treatment unit, so the exposure at X, Y, Z setting 76.3, 86.5, 148.1 could be given. Thus, the originally prescribed dose for the treatment region was given. The neurosurgeon and radiation oncologist explained the situation to the patient.
Device Manufacturer: Leksell Gamma System
Model: 24001 Type C
Source Manufacturer: General Electric Company
Model: 43047
Event Report ID: MN100002
A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.