[Improvement of Cold Artifacts in Body Trunk 18F-FDG PET/CT by Absolute-single scatter simulation: Validation in an Out-of-body High-accumulation Phantom].

PURPOSE: This study aimed to verify whether cold artifacts caused by the gap state between attenuation correction computed tomography (ACCT) and positron emission tomography (PET) data (so-called hot-in-air (HIA) state) in body trunk PET/computer tomography (CT) examinations can be improved by the Absolute-single scatter simulation (SSS), which is a scatter correction method in a phantom experiment using the high-accumulation syringe of out-of-body phantom. METHOD: PET imaging profile curves in the HIA state were evaluated using a high-accumulation syringe that simulated a urinary tract pouch encapsulated with 18F-FDG solution. The hot syringe-to-background ratio (HBR) of the syringe was changed to 5, 7, and 10. Moreover, PET image quality evaluation of the HIA state was performed with a syringe placed on the top of a NEMA IEC body phantom. Six spheres (10-37 mm in diameter) were placed inside the phantom and filled with 18F-FDG solution with a sphere-to-background ratio of 4. The evaluation items of image quality were N10 mm, QH, 10 mm / N10 mm, and recovery coefficient (RC). RESULT: The image quality tended to deteriorate as the HBR of the syringe increased in the relative-SSS, while the effect was small in the Absolute-SSS and the lowest at HBR 10. The RC10 mm of HBR 5 was 0.33 for the Relative-SSS, which was below the criterion for the Relative-SSS, but was 0.5 for the Absolute-SSS, which met the criterion. CONCLUSION: Absolute-SSS significantly improved cold artifacts caused by HIA states on body trunk PET/CT examinations, suggesting that it is highly useful both visually and quantitatively.