ABSTRACT
Purpose:The image information and technique of positron emitter nuclei generated by high energy X-ray photonuclear reactions with body tissues from MM50 is studied.It is explored to verify for dose delivery and location monitoring in tumor target after high energy photon radiation therapy with the image information.Materials and Methods:The technique is based on the photonuclear reactio-as in body tissues elemental composition ~(12)C,~(16)O and ~(14)N with high energy X-Ray,energies well above 20 MeV,resulting primarily in ~(11)C and ~(15)O but also ~(13)N.The induced positron activity distributions were scanned off-line in a PET/CT after irradiation.The activity distributions and position may be used to verify for dose delivery and location in tumor target.These radiations are similar to RT in three fields with some different dose delivery from TPS.The phantom began to be scanned off-line in a PET/CT a couple of minutes after irradiation.The scanning time is respectively 20 minutes and(2～5)mniutes for ~(12)C and ~(16)O.The levels of the beam energy are 10MV,25MV,50 MV.The extent of dose is 1.0 Gy～10.0 Gy.Since measured PET images change with time post irradiation,as a result of the different decay tim-es of the radionuclides,the signals from activated ~(12)C,~(16)O within the irradiated volume could be separated from each other.Most informationis obrained from the carbon and oxygen radionuclide's which the most abundant elements are in soft tissue.A brain phantom Rlade oneself was irradiated with high energy X-ray beams from IBA MM50.The 3D radiation treatment planning system,Nucletron-TPP 3.2,was used to calculate the delivered dose distributions.The phantom was directly simulated in the Nucletron-TPP after CT scan.PET/CT is fro-m GE Discovery LS Ⅱ.Resuits:It was confirmed that no activity was detected at 10 Mv X-ray energy,which was far below the energy threshold for photonuclear reactions.Totally 25 MV X-ray beams can produce photonuclear reactions and get to activity distributions images in PET/CT.It need to greater dose in order to good images information.For 50 MV X-ray beams,2 Gy-3 Gy dose,a normal RT dose,can get to activity distributions images.Conclusions:It was concluded that the PET-CT image acquired from the activity of the ~(15)O and ~(11)C positron emitter nuclei might provide the area and dose distribution information of 50 MV X-ray irradiation in a phantom.It can verify the in vivo dose delivery and location in tumor target after high energy X-ray RT.