The following information was received from the State of
California via email:
The licensee reported a patient undergoing a gamma knife stereotactic radiosurgery (Elekta Instruments AB, Gamma Knife Perfexion, serial number 6021) on March 20, 2009 received a significant dose to an untargeted area due to an error in the imaging process used for treatment planning. The fiducial marker box (coordinate markers) used to register the CT images was misaligned (the CT locator box had not been firmly seated on the targeting frame as it should have been) which resulted in a target shift of approximately 2.0 mm. Due to the small size of the target (7mm x 4mm x 3mm) and the small size of the radiation shots (4 mm collimators), this shift of the 2.0 mm resulted in only about 52% of the target receiving the prescribed dose of 11 Gy. Therefore, a significant portion of this dose (48%) was shifted to normal tissue (temporal bone) outside of the intended treatment volume. This was a single fraction treatment. The patient is not expected to have any adverse consequences from this event. The physician did not feel additional treatment was advisable. The physician counseled the patient regarding this misadministration. Corrective actions taken by the licensee include: 1) additional training for the CT technologists on the correct placement of the fiducial box; 2) for all ongoing similar treatments, the medical physicist will double check the box placement; and 3) the policies and procedures were updated.
On June 22, 2009, RHB-Brea RAM received a written report from Hoag Hospital that was dated April 1, 2009, and was faxed to RHB-Sacto on April 3, 2009 at 4 PM. The report was mailed from RHB-Sacto on June 12, 2009 to the RHB-Brea X-ray office and date stamped by that office on June 15, 2009 at 12:45 PM. The report stated they were reporting a misadministration which occurred on March 20, 2009 and that this event was previously reported on the evening of March 20, 2009 by telephone. Per the licensee, they had left a voice message on the answer phone at RHB-Sacto on the night of the incident instead of reporting the incident to the 24/7 radiological emergency assistance center.
CA 5010 Number: 032009
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.