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Background Occupational health risk assessment of dust-exposed operations is an important part of occupational health work. However, there is a lack of objective and effective methods for validating the risk assessment results. Objective To explore the application value of chest imaging changes in validating occupational health risk assessment results of dust-exposed operations. Methods Alumina dust-exposed workers in an abrasive manufacturing company were selected as study subjects. The Australian Occupational Health and Safety Risk Assessment model (Australian model), and the Singapore semi-quantitative risk assessment model of occupational exposure to chemical substances (Singaporean model) were used to conduct occupational health risk assessment for the target group. Consistency of the assessment results was compared. The cumulative risk value and cumulative risk level of the subjects were calculated. The subjects were examined and diagnosed by chest radiographs, and the differences in the positive rates of aluminum dust shadows of workers at different job risk levels and different cumulative risk levels were compared. Results The average risk ratios (RR) of selected alumina dust-exposed workers estimated by the Australian model and the Singapore model were both 0.49±0.10, indicating generally medium occupational health risk level. The evaluation results of the two models were obviously consistent (kappa test, k = 0.823, P < 0.001). Among the 192 subjects, 62 (32.3%) were found to have aluminum dust shadows on their chest radiographs, and there were no case of pneumoconiosis. The aluminum dust shadows were mainly classified by shape and size as “s” (30.7%); the profusion of small opacities was mainly "less than 0/1" (31.3%); they were mostly distributed in 2 pulmonary zones (18.8%), and mostly in the right lower lung (18.8%), and none was seen in the two upper lung zones. The positive rate of aluminum dust shadows in the high-risk workplaces (41.7%) assessed by the Australian model was significantly higher than that in the medium-risk workplaces (22.9%) (P < 0.01). The positive rate of aluminum dust shadows in the medium-risk workplaces (42.7%) assessed by the Singapore model was significantly higher than that in the low-risk workplaces (23.3%) (P < 0.01). The cumulative risk levels evaluated by the two models were all atⅠ- Ⅲ levels. With the increase of cumulative risk level by the two models, the positive rates of aluminum dust shadows in the subjects both showed an obvious increase trend (P < 0.05). Conclusion The risk assessment results of the Australian model and the Singapore model are obviously consistent for the target group. They can be jointly applied to the risk assessment of dust-exposed operations. The application of chest imaging changes is of certain value to validate the results of occupational health risk assessment for dust-exposed operations.
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OBJECTIVE: To analyze the radiosurgical results of intracranial meningiomas after Gamma Knife radiosurgery (GKS) and to assess the possible factors related to the outcome and complications in treating meningiomas. PATIENTS AND METHODS: We retrospectively reviewed the clinical and radiological data in 179 patients(194 lesions) treated with GKS for intracranial meningiomas between May 1992 and October 2000. Radiosurgical responses were categorized as shrinkage, stasis and enlargement, and we defined the shrunken and static group as a radiological control. A Cox proportional hazards model was used to evaluate the correlation between the radiosurgical outcomes and various factors such as location and size of tumor, age and gender of patients, relation to venous sinus, pre-GKS degree of edema, treatment modality, radiosurgical parameters, and pathologic findings. RESULTS: Patients were grouped into skull base meningiomas(57.7%), non-skull base tumor including convexity, parasagittal, and falx meningiomas(37.1%), and others(5.2%) according to the location of tumors. The mean maximum dose and the margin dose of tumor was 30.0Gy(19-45Gy) and 15.1Gy(9.5-24.5Gy), respectively. The mean volume of the tumors was 9.4cc(0.003-45.0cc). The radiologic control rate was 97.1%. The radiation induced imaging change with or without neurologic deficit was the most common complication(23.6%). There were seen mostly in convexity, parasagittal, and falx meningiomas which were deeply embedded in cortex. CONCLUSION: GKS for intracranial meningioma seems to be safe and effective treatments. However, GKS should be considered very cautiously in non-skull base tumor such as convexity, parasagittal, or falx meningiomas with regards to patient's age and general condition, size and location of tumor, pattern of embedding into cortex, presenting symptoms and patient's preference.