Presentation In-beam OpenPET imaging simulation based on patient data

田島, 英朗  ,  Kurz, Christopher  ,  吉田, 英治  ,  Chen, Wenjing  ,  Bauer, Julia  ,  Jürgen, Debus  ,  Parodi, Katia  ,  山谷, 泰賀

[Purpose] The OpenPET is our original idea to provide an open space through which the treatment beam can pass. Because particle therapy beams such as the carbon ion beam produces positron emitters by fragmentation reactions, it can be confirmed, by means of PET, whether the dose distribution in the treatment plan and that in the actual irradiation are matched. In this study, we conducted numerical simulation of in-beam OpenPET imaging based on clinical patient data for scanned <sup>12</sup>C ion beam irradiation to investigate the effectiveness of the OpenPET geometry compared with offline PET measurements.[Methods] Production rates of positron emitters were calculated based on patient CT image and physical dose information in the treatment plan by using FLUKA Monte Carlo code. The activity distributions averaged over the measurement time were calculated using analytical model incorporating biological washout and physical activity decay effects. Coincidence detection of annihilation gamma-rays from the activity distribution was simulated by the Geant4 Monte Carlo toolkit, and simulation data for online OpenPET and offline PET were generated. The list-mode MAP-OSEM algorithm with a smoothing prior was employed to reconstruct activity distribution images.[Results] The online OpenPET with a measurement time of 10 minutes could detect a similar number of list-mode data events as the offline PET with a measurement time of 30 minutes. Range shift analysis showed that the online OpenPET could suppress uncertainty in beam shift detection better than the offline PET.[Discussion] The online OpenPET had better performance than the offline PET because the activity produced by fragmentation reaction consisted mainly of isotopes with short half-lives and decreased not only physical decay but also by biological effect during patient movement for offline PET.[Conclusion] The simulation results showed that the online OpenPET could achieve good quality of images with a short measurement time.
The 111th Meeting of Jqapan Society Medical Physics

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