Development of a Whole-Body Dual Ring OpenPET for in-Beam PET

For in-beam positron emission tomography (PET), which is an in situ monitoring method for charged particle therapy, we developed the world's first open-type PET system "OpenPET." Following our previous studies for small prototypes, in this paper, we finally developed a whole-body dual ring OpenPET (WBDROP). This scanner has two separated rings. Each ring has two detector rings of 40 detector blocks, each of which has the capability of 4-layer depth-of-interaction identification. The ring diameter is 66 cm, and the adjustable open gap is fixed as 9 cm. We found that the system sensitivity was 4.4%. The average spatial resolution, which was measured through filtered back projection, was about 3.5 mm. For in-beam PET, imaging performance was confirmed through phantom experiments. Phantom study results with ¹¹ C beam and ¹⁰ C beam irradiations of about 3 Gy showed that the beam stopping position in the target could be measured with a precision of better than 2 mm. The developed WBDROP promises high performance for in-beam PET imaging.