First experience of 192Ir source stuck event during high-dose-rate brachytherapy in Japan

Purpose
To share the experience of an iridium-192 (¹⁹²Ir) source stuck event during high-dose-rate (HDR) brachytherapy for cervical cancer.

Material and methods
In 2014, we experienced the first source stuck event in Japan when treating cervical cancer with HDR brachytherapy. The cause of the event was a loose screw in the treatment device that interfered with the gear reeling the source. This event had minimal clinical effects on the patient and staff; however, after the event, we created a normal treatment process and an emergency process. In the emergency processes, each staff member is given an appropriate role. The dose rate distribution calculated by the new Monte Carlo simulation system was used as a reference to create the process.

Results
According to the calculated dose rate distribution, the dose rates inside the maze, near the treatment room door, and near the console room were  10^-2 [cGy · h^-1], 10^-3 [cGy · h^-1], and << 10^-3 [cGy · h-1], respectively. Based on these findings, in the emergency process, the recorder was evacuated to the console room, and the rescuer waited inside the maze until the radiation source was recovered. This emergency response manual is currently a critical workflow once a year with vendors.

Conclusions
We reported our experience of the source stuck event. Details of the event and proposed emergency process will be helpful in managing a patient safety program for other HDR brachytherapy users.