Objective:To analyze the clinical features and imaging findings of chest computed tomography (CT) of patients with corona virus disease 2019 (COVID-19), and to provide imaging guidance for early diagnosis and clinical treatment.Methods:A total of 74 patients diagnosed with positive nucleic acid test of nasopharyngeal swab were retrospectively collected from January 23 to February 22, 2020 in the inpatient department of Rui′an People′s Hospital. Their clinical features were analyzed in combination with CT image characteristics.Results:Of the 74 patients, 62 (83.8%) had fever, 59 had abnormalities in CT examinations and 15 patients had no imaging abnormalities. The average interval from onset to CT examination was 4.6 days. Among 59 patients, 58 cases (98.3%) were mainly peripherally distributed, 53 cases (91.4%) had multiple lesions and five cases (8.6%) had single nodules. The main manifestation was ground glass opacities (45 cases, 76.3%). The lesions were mainly distributed in the middle and lower lobe of the lungs, accounting for 76.3% (45 cases). Air bronchogram was shown in 21 cases (35.6%), and reversed halo sign was shown in 10 cases (16.9%). Other rare abnormalities were small cavities in three cases (5.1%), tree-in-bud pattern in one case (1.7%). Intrathoracic lymph node enlargement was found in two cases (3.4%) by re-examination.Conclusion:The CT examination characteristics of COVID-19 patients could play an important role for early diagnosis and follow-up.

Objective Magnetic resonance simulator(MR Sim)is a novel type of simulation equipment utilized in radiotherapy.Acceptance testing is an essential quality assurance procedure prior to the clinical use of the MR Sim.The report provides the detailed procedures and result analysis of acceptance testing for an MR Sim.Methods The acceptance testing scheme was developed following the recently published AAPM TG284 report and the NCC/T-RT 002-2023 guidelines.Quality control equipments such as ACR(American College of Radiology)large phantom and geometric distortion measurement phantom were used for evaluating various aspects of the MR Sim,including the effectiveness of shielding,the functionality of imaging system,the image quality,the performance of radio frequency coils,the geometric accuracy of large field imaging,the precision of external laser markings,the couch movement accuracy,and the image transmission accuracy.Results The shielding effectiveness at a frequency of 150 MHz exhibited an average value of 105 dB.All of 8 image quality indices,namely geometric accuracy,slice position accuracy,slice thickness accuracy,image uniformity,artifact ratio,signal-to-noise ratio,high-contrast spatial resolution,and low-contrast resolution,fell within recommended tolerances.The maximum geometric distortion observed across a 25 cm field of view was less than 2 mm.The errors in external laser markings and couch movement accuracy were both less than 1 mm.The couch levelness was less than 1°.Both radio frequency coils and image transmission passed the required tests.Conclusion MR Sim is high-precision and complex.To ensure its precise application in radiotherapy,the acceptance testing for an MR Sim should be meticulously designed and executed following the established guidelines and accounting for its unique performance characteristics.