Objective:To explore the feasibility and accuracy of three-dimensional (3D) modeling methods based on ultrasound imaging data for normal and abnormal fetal cardiac structures, and to construct a methodology system for 3D printing of fetal heart based on ultrasound.Methods:A total of 93 fetuses examined in Tangdu Hospital of Air Force Military Medical University from January to December 2019 were selected. Fetal echocardiography was obtained using spatio-temporal image correlation (STIC). Ninety-three hearts were 3D modeled by blood flow modeling, blood pool modeling and cavity modeling, and printed by stereolithography technique. The data measured on the 3D digital models and 3D printed solid models were compared with the corresponding fetal echocardiographic images respectively in order to evaluate the accuracy of the modeling methods.Results:The fetal cardiac blood flow models based on Doppler flow image data showed the malformation and trend of small blood vessels. The fetal cardiac structure models printed based on blood pool modeling displayed the malformation of heart and large blood vessels. Models printed based on cavity modeling method accurately displayed valve and structural defects.For 83 normal fetal hearts, the long diameters of left and right ventricles measured on echocardiography [(15.3±1.9)mm, (13.2±1.9)mm] were compared with those measured on digital models [(15.1±1.9)mm, (12.9±1.9)mm] and 3D printed models[(15.1±1.9)mm, (13.0±1.9)mm], respectively, and there were no significant differences between any two groups of them ( P>0.05). Bland-Altman showed good consistency for all measurements within and between operators. Conclusions:The three modeling methods, including blood flow modeling, blood pool modeling and cavity modeling, have their own advantages in displaying different types of fetal heart malformations. Appropriate modeling methods should be selected for 3D modeling and printing to make up for the limitations of single modeling method. The consistency between measurements on 3D models and those on echocardiography is high, and the repeatability between operators is good.

Background A large number of power supply workers are involved in live working and are exposed to multiple risk factors for long periods of time during outdoor work, which in turn causes occupational health problems. Objective To identify potential ergonomic factors related to work-related musculoskeletal disorders (WMSDs) and estimate the ergonomic risk of electricians. Methods A total of 31 workers were randomly selected from a training base under a power supply enterprise in Guangxi, and their operation processes were recorded by video. Using the Rapid Upper Limb Assessment (RULA) method, the workers were scored by the posture of their arms, neck, and torso during operation, and the final scores were summarized to assess their risk level. Two independent samples t-tests were used to compare the differences in RULA scores. Results A total of 31 videos for mounting/dismounting insulation mask and 29 videos for breaking/connecting contact terminal were collected. The RULA score for mounting/dismounting insulation mask was 6.6 ± 0.7 (left side) and 7.0 ± 0.2 (right side), most of the workers had a score of 7 (71.0% on the left side and 96.8% on the right side), and the upper limb and overall scores on the right side were higher than those on the left side (P < 0.05). The RULA score for breaking/connecting contact terminal was 6.9 ± 0.4 (both right and left sides), most of workers had a score of 7 (89.7% on the left side and 93.1% on the right side), and the difference of the overall scores between the right and left side for this operation were not statistically significant (P > 0.05). The ergonomic risk levels for both operations were level 3 or higher. Conclusion Mounting/dismounting insulation mask and breaking/connecting contact terminal are typical upper limb operations, and have a high level of ergonomics risk, requiring effective preventive and protective measures.