Objective To explore the bio-effects of high single-dose irradiation on MDA-MB-231 xenografts under the same radiation dose.Method Female BALB/c-nu mice bearing 8-9 mm MDA-MB-231 xenografts were randomized into 5 groups:0Gy group (blank control group),high single-dose 8Gy group (8Gy/one fraction/day),high single-dose 10Gy group (10Gy/one fraction/ day),conventional radiation 2Gy × 4 group (8Gy/4 fraction/4d),conventional radiation 2Gy × 5 group (10Gy/5 fraction/5d).The volumes of gross tumors on nude mice were observed every three days.The tumor growth curve of transplanted tumor were also drawn.The 18F -FDG PET/CT imaging of mice bearing MDA-MB-231 xenografts from all radiation groups were performed with detecting the Ki-67 expressions of tumor ceils by immunohistochemistry at 7days and 14days after final irradiation.Results Compared to control group,the tumor growth of all radiation groups were delayed after radiation,especially single high-dose 10Gy groups (P ＜ 0.05).At 7days and 14days after final radiation,the SUVmax (the maximal standardized uptake value) of xenografts in high single-dose groups was lower than that in conventional fractional groups (P ＜ 0.05) under the same radiation dose.And the percent of Ki-67 positive cells after high single-dose irradiation were less than fractioned irradiation at 7,14days after final radiation (P ＜ 0.05).Conclusion At the same dose,high single-dose irradiation inhibits the growth of MDA-MB-231 xenografts more than conventional fraction irradiation.PET/CT also could evaluated the early changes of proliferation activities of MDA-MB-231 breast cancer cells after irradiation.

Charged particle radiation is one of the most precise approaches for external radiation right now. With a characteristic inverted depth?dose profile and a high?dose Bragg peak at the end of the range, charged particle radiation therapy can deliver a high dose of radiation to tumor without damages in tissue around the tumor. However, a shift of Bragg peak would result in severe consequences. Therefore, it is extremely important to monitor the radiation beam. Application of position emission tomography ( PET) in proton and heavy?ion radiation therapy makes it possible to get accurate radiation range and position of the particle beam, which improves the treatment accuracy of charged particle therapy. This paper introduces the current application of PET in position verification of charge particle range radiation therapy.