Abstract: Low-dose imaging represents a significant research focus within the field of PET, with delayed PET imaging also encountering situations with lower imaging doses. The feasibility of low-dose imaging is typically validated by resampling patient list mode data to obtain shorter acquisition duration sequences. This method is relatively straightforward to implement and more closely resembles real clinical scenarios. However, it may fail to account for the variations in PET count rate characteristics under different dosage conditions. In this study, phantom experiments were conducted with the objective of achieving real low-dose PET imaging by radionuclide decay. Specifically, the background radioactivity of the phantom was achieved at 3/2, 1/2, 1, 1/4, 1/6, and 1/8 of 5.24 kBq/mL, which is the commonly used imaging dose in clinical practice (e.g., 370 MBq of ¹⁸F-FDG for a 70 kg individual). All PET raw data were reconstructed using identical reconstruction parameters. Subsequently, the recovery coefficient (RC), contrast recovery coefficient (CRC), contrast-to-noise ratio (CNR), percent background variability (PBV), background coefficient of variation (BCV), and residual error (RE) of the lung insert at different image planes were calculated within the phantom. Additionally, the influence of different acquisition durations on scatter fraction was evaluated, with a fixed imaging dose, and vice versa. The results demonstrate that reducing the imaging dose to half of the clinically common dose results in acceptable PET quantitative accuracy and image quality. When the background radioactivity of the phantom is at least half of 5.24 kBq/mL, minimal changes are observed in the RC and CRC of the 10 mm sphere with different acquisition conditions as a function of injected dose. However, when the dose is decreased from 1/4 to 1/8, both RC and CRC of the 10 mm sphere exhibit abnormally high values. The PBV and BCV exhibit an increase with a reduction in the injected dose, while the CNR of the spheres exhibits a decrease. When the background radioactivity is at least 1/4 of 5.24 kBq/mL, the average RE of the lung insert exhibits a decrease with a reduction in the injected dose. The PBV, BCV, CRC, and CNR obtained through acquisition with equal counts are relatively consistent across different injected dose conditions. This suggests that this method may be a viable approach for delayed PET imaging. With the same acquisition duration, the scatter fraction increases with decreasing radioactivity within the phantom. When the injection dose remains constant, alterations in acquisition duration have a negligible impact on scatter fractions. The most pronounced change occurs when the acquisition time is reduced from 2.5 minutes to 1.5 minutes, resulting in a mere 0.09% increase. This indicates that simulating low-dose imaging by shortening the acquisition duration has certain limitations.