Fig. 5

PET respiratory gating in the presence of small motion artifacts. a A Derenzo phantom (Phantech Medical) was filled with ~ 3.7 MBq (100 µCi) of fluorine-18, attached to a lever, and placed in the axial center of the PET insert inside the MRI scanner. A 15 min PET/MRI scan was performed with no phantom motion. b The phantom was artificially moved up and down about 3–4 mm inside the PET insert continuously throughout a 15 min PET/MRI scan to mimic the spatial scale of mouse respiratory motion. PET image reconstruction without respiratory gating produced very slight blurring. c PET image reconstruction with respiratory gating led to minimal PET image quality improvement. d The phantom with ~ 3.7 MBq (100 µCi) of gallium-68 was attached to a lever and placed in the axial center of the PET insert inside the MRI scanner. A 15 min PET/MR scan was performed with no phantom motion. e The phantom was artificially moved up and down about 3–4 mm inside the PET insert continuously throughout a 15 min PET/MR scan. PET image reconstruction without respiratory gating produced intense image blurring. f PET image reconstruction with respiratory gating led to sharpening of image resolution (yellow arrows)