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 +1.06%. 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. (author)