RESUMO
BACKGROUND: Though the dosimetric criteria for the gastrointestinal tract were met, late gastrointestinal toxicity was seen in several cases. Therefore, we thought that it was caused by the positional variation of gastrointestine surrounding pancreatic cancer because of peristalsis. METHOD: They were confirmed by CT image regularly. And we evaluated that how much the difference of matching methods for correcting the positional variation influenced dose distribution. RESULT: The fiducial markers could follow the position of pancreatic cancer and the duodenum. But it could reproduce the dose distribution to pancreatic cancer and the duodenum. DISCUSSION: In proton therapy, the reproducible improvement of the duodenum position did not make the dose of the duodenum same as planning dose because the matching of fiducial markers made the positional relations between beam compensator and the duodenum change. CONCLUSION: The fiducial markers are useful for correcting the position of pancreatic cancer and the duodenum. But in proton therapy, it could not reproduce the dose distribution to pancreatic cancer and the duodenum.