Objective High levels of radioactivity inside a facemask cause scatter correction (SC) errors that appear as photopenic artifacts on quantitative oxygen-15 (15 O) gas-inhalation positron emission tomography (PET) images. The present study aimed to validate the ability of scatter limitation correction (SLC) to eliminate SC errors in 15 O gas-inhalation PET images acquired from patients and a phantom. Materials and methods We analyzed the SC errors in phantom images and calculated parametric images of the cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2). Phantoms comprised a cylinder and paper with radioactivity to simulate a facemask during (15 O)O 2 gas inhalation. Parametric images were calculated from 15 O gas-inhalation PET images of ten participants. All PET data were reconstructed using conventional SC as model-based SC and SLC. Images acquired from the phantoms and parametric images were assessed visually and quantitatively in the presence and absence of SC error. Results SC error was evident in images derived from the paper phantom and at the slice level of the cerebellum in CBF, OEF, and CMRO 2 images. The radioactivity concentration in the cylindrical phantom with the paper phantom significantly improved with SLC. The SLC also increased the quantitative indices of CBF, OEF, and CMRO 2 by 23.8, 42.2, and 44.4%, respectively. Conclusion SLC visually eliminated the SC error and increased the quantitative parameters on 15 O gas-inhalation images derived from a phantom and from patients.
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