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Objective@#To understand the differences in the application of three distant vision examination methods in children, so as to provide a reference for developing a unified distant vision examination for this population.@*Methods@#The study involved 98 children aged 4 to 16 years who visited the ophthalmology department of a children s hospital in Anhui Province between August 15 and 25, 2022. Vision was measured using the distant vision test method specified in the 2014 National Student Physical Fitness and Health Survey (V1), the 2019 National Student Physical Fitness and Health Survey (V2), and Specification for Screening of Refractive Error in Primary and Secondary School Students (WS/T 663-2020) (V3). The paired samples McNemar s test and Wilcoxon test were performed to compare the detection rate of poor vision and the difference between the visual acuity test results of the three methods.@*Results@#The results of the 98 children examined according to V1, V2, and V3 showed that the M (P25, P 75 ) of the right eye were 4.8（4.6，5.0），4.8（4.7，5.0），and 4.8（4.7，5.0）while the left eye visual acuity M ( P 25 , P 75 ) were 4.8 （4.6，5.0），4.9（ 4.7 ，5.0），and 4.9（4.7，5.0），respectively. The rates of poor visual acuity detection for the right eye were 63.3%, 58.2% and 58.2 % for V1, V2, and V3, respectively, while for the left eye, they were 58.2%, 54.1% and 53.1%, respectively. McNemar test results showed that there were no statistically significant differences in the rates of poor visual acuity detection between the right and left eyes for V1 vs. V2, V1 vs. V3, and V2 vs. V3 (left eyes： χ 2=2.25，2.29，0.00，right eyes： χ 2=3.20，3.20，0.00， P >0.05).Wilcoxon test results indicated that there were statistically significant differences between the right and left eye visual acuity groups for V1 vs. V2 and V1 vs. V3 (left eyes： Z =-4.15，-4.60, right eyes： Z = -4.70，-4.99, P <0.01).@*Conclusion@#Irrespective of whether the starting visual standard starts at row 4.0 or 5.0, different standards of visual standard passage have an impact on the visual acuity results. It is recommended that existing methods of screening for distance vision are standardized.
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Medical whole-body positron emission tomography (PET), one of the most successful molecular imaging technologies, has been widely used in the fields of cancer diagnosis, cardiovascular disease diagnosis and cranial nerve study. But, on the other hand, the sensitivity, spatial resolution and signal-noise-ratio of the commercial medical whole-body PET systems still have some shortcomings and a great room for improvement. The sensitivity, spatial resolution and signal-noise-ratio of PET system are largely affected by the performances of the scintillators and the photo detectors. The design of a PET system is usually a trade-off in cost and performance. A better image quality can be achieved by optimizing and balancing the key components which affect the system performance the most without dramatically increases in cost. With the development of the scintillator, photo-detector and high speed electronic system, the performance of medical whole-body PET system would be dramatically improved. In this paper, we report current progresses and discuss future directions of the developments of technologies in medical whole-body PET system.