The following was sent by email from the Commonwealth of Massachusetts:
The licensee reported on April 24, 2019 that it discovered on April 23, 2019 two High Dose-rate Remote Afterloader (HDR) medical events where tissue other than the treatment site received a dose exceeding the reporting requirements 105 CMR 120.594(A)(1)(c). One of the medical events occurred in March of 2019 and the other occurred in October of 2018.
The licensee reported that a 5 cm offset from the target location resulted in dose to unintended tissue during each treatment.
The licensee used a Varian Medical Systems, Inc. Model VariSource iX HDR containing iridium-192 to deliver the doses for both treatments. Each prescribed dose to each patient was 10 gray (1,000 rad) to the vaginal cavity across two fractions.
Both events occurred as a result of an unintended area of each patient's vaginal cavity receiving a portion of the prescribed dose. The licensee reported that the cause of the events is a combination of a change in applicator size and incorrect parameters input into the device console. Some two years ago, the size of the vaginal applicator changed from 120 cm in length to 125 cm in length, but there were no issues until the two aforementioned events. From the administration documentation, the licensee determined that the technician erroneously entered 120 cm into the device console rather than 125 cm, effectively causing a 5 cm offset. As a result the lower 5 cm of each patient's vaginal cavity received more dose than intended. The exact number is yet unknown. The licensee will provide additional information in a written report.
The licensee reported that the referring physician, who is the same for each patient, has been notified and that the referring physician intends to notify each patient.
The Agency [Massachusetts Radiation Control Program] plans to perform a special inspection and considers this event to be open.
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.