In September, 2003, a patient at Lancaster General Hospital's Health Campus was undergoing
Co-60 gamma knife treatment. In preparation for the treatment, the patient was immobilized to ensure that the gamma knife was accurately aimed at the treatment site. During the treatment, the patient became uncomfortable and asked to move. He was told to move only his legs, but he shifted his body. As a result, the patient shifted 7cm away from the gamma knife. Licensee was unable to calculate dose to unintended site. There were no adverse effects to the patient.
- * * UPDATE FROM LICENSEE (MONTAGNES) TO NRC (HUFFMAN) AT 1048 EDT ON 4/07/05 * * *
The following additional details were provided on the event. The licensee also is reporting this as a 10 CRF Part 21 report.
The Licensee reported and incident involving component of a Leksell Model 23004 Type B Gamma Knife unit (Elekta AB, Stockholm, Sweden). The specific components involved are the "z-bars". During the treatment with this device, a patient's head is secured into a head frame in preparation for irradiation treatment of deep head disease. This head frame is then also secured to a helmet and couch assembly to ensure immobilization during treatment. In, order to localize the therapeutic radiation beam to a precise location, the frame is able to be adjusted in the X, Y, or Z directions. In the "Z" direction, there are metal bars that are adjusted to a desired position, then locked into place by the treatment staff with a number of screens.
During the case which lead to the incident, a large patient is believed to have made an exaggerated movement during treatment, against staff instructions, as a means of alleviating some discomfort. At the conclusion of the treatment, the staff noted that the patient's position - as indicated by the z-bars - had slipped caudally by approximately 7 cm.
The incident occurred on September 30, 2003 in the Lancaster General Gamma Knife Center, 2102 Harrisburg Pike, Lancaster, Pennsylvania, 17603. Although this original incident occurred on September 30, 2003, this report is only being filed now as a result of an investigation by the NRC that concluded on April 5, 2005.
R1DO (Noggle) and
NMSS (Essig) notified.