The licensee administered a 66% under dose during one of a series of
brachytherapy doses to a patient. On June 6, 2006, during the second fractional dose in the series, the licensee noted that the administration of the dose took a longer time period than the dose administered to the patient on June 5, 2006. This was unexpected so the licensee performed a preliminary investigation. The licensee discovered that the computer used to time the dose incorrectly recorded the time taken for a quality control (
QC) check and the dose time to the patient as one period of time. This was a first time use of this equipment by the licensee. The licensee determined that the patient received a dose of 116 centigray instead of 360 centigray during the administration of the first dose on June 5, 2006. A sealed 6 curie
Ir-192 brachytherapy source manufactured by Varian was used. The licensee has informed the patient of the dose discrepancy. Additional controls have been implemented by the licensee to ensure that the computer will not record the time taken for the
QC check as dose time to the patient in the future.
The State of Oklahoma is following up on the report by sending an inspector to the site.
- UPDATE FROM STATE TO KNOKE AT 10:34 EDT ON 06/07/06 ***
The State provided the following information via facsimile:
This was the first use of a new HDR modality mammosite treatment. The QC on this instrument was done prior to patient treatment. The treatment plan was sent from dosimetry computer to HDR control computer. Computer (or possibly human, not clear at this writing) chose the plan used from QC. Computer interpreted this to mean that a particular amount of dose had already been given. The computer delivered the remainder of dose, 116 centigrays, out of the prescribed 360 centigrays. Time was noted to be shorter than expected, but no alarm raised at the time. A second fraction was given later that day, and it was noticed that the time to deliver the dose was longer than in first dose. Inspection of computer records showed the dose had been stopped during treatment on the first fraction. It was then realized for sure that there was a problem.
Corrective Action: QC ACTIVITY WILL BE DONE IN A WAY THAT IT CANT BE CONFUSED WITH THERAPY.
Notified
NMSS (Wastler ) and R4DO (Runyan).