  Carbon ion therapy have the ability to overcome the limitation of
convertional radiotherapy due to its most energy deposition in selective depth,
usually called Bragg peak, which results in increased biological effectiness.
During carbon ion therapy, lots positron emitters such as $^{11}$C, $^{15}$O,
$^{10}$C are generated in irradiated tissues by nuclear reactions. Immediately
after patient irradiation, PET scanners can be used to measure the spatial
distribution of positron emitters, which can track the carbon beam to the
tissue. In this study, we designed and evaluated an dual-plate in-room PET
scanner to monitor patient dose in carbon ion therapy, which is based on GATE
simulation platform. A dual-plate PET is designed to avoid interference with
the carbon beam line and with patient positioning. Its performance was compared
with that of four-head and full-ring PET scanners. The dual-plate, four-head
and full-ring PET scanners consisted of 30, 60, 60 detector modules,
respectively, with a 36 cm distance between directly opposite detector modules
for dose deposition measurements. Each detector module was consisted of a
24$\times$24 array of 2$\times2\times$18 mm$^{3}$ LYSO pixels coupled to a
Hamamatsu H8500 PMT. To esitmate the production yield of positron emitters, a
10$\times15\times$15 cm$^{3}$ cuboid PMMA phantom was irradiated with 172, 200,
250 AMeV $^{12}$C beams. 3D images of the activity distribution of the three
type scanners are produced by an iterative reconstruction algorithm. By
comparing the longitudinal profile of positron emitters, measured along the
carbon beam path, we concluded that the development of a dual-plate PET scanner
is feasible to monitor the dose distribution for carbon ion therapy.
