Assessing the Effectiveness of Risk Communication for Maintenance Workers Who Deal With Induced Radioactivity Management of Medical Linear Accelerators.

In Japan, an amended law that mandates levels of unintended induced radioactivity has been in effect since 1 April 2012. According to the new regulation, if the concentration of induced radioactivity in affected parts is above the clearance level, the parts must be regarded as radioactive even if they weigh less than 1 kg. This regulation reform raises several new issues concerning medical linear accelerators, including how to determine the decay period for induced radioactivity before maintenance can be performed and how to identify what parts should be considered radioactive waste. The authors performed several risk communication (RC) activities aimed at improving the understanding of maintenance workers at medical accelerator manufacturers and establishing good guidelines by involving stakeholders. For this purpose, a working group was established and conducted RC activities, such as holding opinion exchange meetings between medical staff and maintenance workers and creating a booklet to answer questions from maintenance workers. To evaluate these activities, three questionnaire surveys were conducted between 2011 and 2014. According to the results of this study, the ratio of maintenance workers who accepted "The decay period is within one week" was approximately 60% at the third survey and significantly increased (P < 0.0001) during the survey period. Approximately 25% of the maintenance workers felt that not enough information was provided about the decay period, and approximately 63% thought that the information provided on the health effects of radiation was sufficient. These results suggest that the present RC was successful.

[Field Survey Results on Output for X-ray Therapeutic Accelerators in Radiotherapy Institutions of Saitama and Tochigi Prefectures.].

Field survey on output for X-ray therapeutic accelerators took place three times in Saitama Prefecture. The result of the field survey in 1997 showed the different rate from the designated dose at peak depth of 35 beams in 18 institutions. As different rate within +/-5% stood 91.4% in all beams, so different rate within +/-3% stood 85.7% in the same beams. The average different rate from the designated dose at peak depth was 11.06%. The standard deviation of the same condition was 3.72.The result of the field survey in 2005 showed the different rate from the designated dose at correction depth of 36 beams in 18 institutions. As different rate within +/-5% stood 100% in all beams, so different rate within +/-3% stood 91.6% in the same beams. The average different rate from the designated dose at correction depth was +0.80%. The standard deviation of the same condition was 1.46.We understood that the different rate from the designated dose at radiotherapeutic institutions decreased and even the value of the standard deviation was decreasing, by receiving 3 times of field surveys that was held in Saitama Pref. Also we understood that the beam numbers of different rate within +/-5% and the beam numbers of different rate within +/-3% were going up. We recognized that the good result of accurate dose is obtained more, by doing a continual field survey. The field survey was carried out in 2006 in Tochigi Prefecture and was the insufficient result in 10% of institutions.