Presentation Patient Data-Based In-beam OpenPET Simulation

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

The OpenPET is our original idea to provide an open space through which the treatment beam can pass during positron emission tomography (PET) measurement. Because the particle therapy beams such as the carbon ion beam produces positron emitters by fragmentation reactions, we can confirm, by means of PET, whether or not the irradiation is successful. In this study, we conducted numerical simulation of in-beam OpenPET imaging based on clinical patient data for scanned 12C ion beam irradiation to investigate the effectiveness of the OpenPET geometry compared with offline PET measurement. Production rates of the positron emitters were calculated based on the patient CT image and physical dose information in the treatment plan by the FLUKA Monte Carlo code. The radioactivity distributions averaged over the measurement time were calculated using analytical model incorporating biological washout and physical decay effects. Coincidence detection of annihilation gamma-rays from the radioactivity distribution was simulated by the Geant4 Monte Carlo toolkit, and simulation data for online OpenPET and offline PET were generated as list-mode data. The list-mode maximum a posteriori ordered subset expectation maximization method with a smoothing prior was employed to reconstruct radioactivity distribution images. As a result, we found 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 analysis of the reconstructed images compared with the original radioactivity distributions showed the OpenPET could achieve better accuracy than the offline PET even when the measurement time was short.
4th SNU-NIRS Workshop on Nuclear Medicine Imaging Science and Technology

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