Effect on image quality and radiation dose in a phantom study for PET/CT

Objective To investigate the effect on image quality and radiation dose of PET/CT with Anthropomorphic phantom to provide data basis for decreasing the radiation dose. Methods PET/CT system of GE Discovery ST-16 was used to scan the anthropomorphic phantom (Model RS-550). CT acquisition conditions were as follows: tube voltage 120 kV, tube current 30-250 mA, pitch 0.938, 1.375 and 1.75. Scan range was divided into body scan and head-neck scan to simulate clinical PET/CT. The noise (SD) was recorded and the signal-to-noise ratio and the figure of merit were calculated. Results The noise decreased with increasing effective dose. The noise decreased rapidly with the effective dose less than 15 mSv, while the decrease of noise was not significant with the effective dose more than 15 mSv. The signal-to noise ratio increased with increasing effective dose. However, the figure of merit was fixed, when the radiation dose increased under the different acquisition condition. All indicators of ATCM were superior to the fixed tube current mode. Conclusions The image quality of CT in PET/CT could not significantly improve by increasing effective dose when it reaches to certain level. It shows that the radiation dose of PET/CT could be effectively reduced by appropriate acquisition conditions according to different clinical requirements. Key words: PET/CT; Image quality; Effective radiation dose; Anthropomorphic phantom