PET monitoring of cancer therapy with 3He and 12C beams: a study with the GEANT4 toolkit.
We study the spatial distributions of beta(+)-activity produced by therapeutic beams of (3)He and (12)C ions in various tissue-like materials. The calculations were performed within a Monte Carlo model for heavy-ion therapy (MCHIT) based on the GEANT4 toolkit. The contributions from positron-emitting nuclei with T(1/2) > 10 s, namely (10,11)C, (13)N, (14,15)O, (17,18)F and (30)P, were calculated and compared with experimental data obtained during and after irradiation, where available. Positron-emitting nuclei are created by a (12)C beam in fragmentation reactions of projectile and target nuclei. This leads to a beta(+)-activity profile characterized by a noticeable peak located close to the Bragg peak in the corresponding depth-dose distribution. This can be used for dose monitoring in carbon-ion therapy of cancer. In contrast, as most of the positron-emitting nuclei are produced by a (3)He beam in target fragmentation reactions, the calculated total beta(+)-activity during or soon after the irradiation period is evenly distributed within the projectile range. However, we predict also the presence of (13)N, (14)O, (17,18)F created in charge-transfer reactions by low-energy (3)He ions close to the end of their range in several tissue-like media. The time evolution of beta(+)-activity profiles was investigated for both kinds of beams. We found that due to the production of (18)F nuclides the beta(+)-activity profile measured 2 or 3 h after irradiation with (3)He ions will have a distinct peak correlated with the maximum of depth-dose distribution. We also found certain advantages of low-energy (3)He beams over low-energy proton beams for reliable PET monitoring during particle therapy of shallow-located tumours. In this case the distal edge of beta(+)-activity distribution from (17)F nuclei clearly marks the range of (3)He in tissues.
Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, 60438 Frankfurt am Main, Germany. pshenich@fias.uni-frankfurt.de
Igor
I
Pshenichnov
Alexei
A
Larionov
Igor
I
Mishustin
Walter
W
Greiner
D001842:Bone and Bones; D002244:Carbon / Q000627:therapeutic use; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D004735:Energy Transfer; D020450:Heavy Ions; D006371:Helium / Q000627:therapeutic use; D006801:Humans; D008954:Models, Biological; D008956:Models, Chemical; D009010:Monte Carlo Method; D009132:Muscles; D009369:Neoplasms / Q000175:diagnosis* / Q000628:therapy; D019047:Phantoms, Imaging; D019904:Polymethyl Methacrylate; D049268:Positron-Emission Tomography / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D011882:Radiotherapy, High-Energy / Q000379:methods; D012062:Relative Biological Effectiveness; D012984:Software; D014867:Water
D014867:Water; D006371:Helium; D002244:Carbon; D019904:Polymethyl Methacrylate