Results and analysis of examination doses for paediatric CT procedures based on a nationwide survey in China.

OBJECTIVE: To report the results of a dose survey conducted across 31 provinces in mainland China from 2017 to 2018 and to analyse the dose level to determine the national diagnostic reference levels (DRLs) for paediatric CT procedures. METHODS: At least ten patients for each age group (0- < 1, 1- < 5, 5- < 10, 10- < 15 years) and each procedure (head, chest and abdomen) for each CT scanner were selected from four to eight hospitals in each province. The dose information (CTDIvol and DLP) was collected from the HIS or RIS-PACS systems. The median values in each CT scanner were considered the representative dose values for the paediatric patients in CT scanning. The national DRLs were estimated based on the 75th percentile distribution of the median values. RESULTS: A total of 24,395 patients and 319 CT scanners were investigated across 262 hospitals. For paediatric CT scanning in 4 different age groups, the median (P50) and the 75th percentile (P75) of CTDIvol and DLP for each scanning procedure were calculated and reported. National DRLs were then proposed for each procedure and age group. CONCLUSION: The dose level of CT scanning for children in mainland China was reported for the first time. The DRLs for paediatric CT in the present study are similar to those in some Asian countries but higher than those in European countries. CLINICAL RELEVANCE STATEMENT: The paediatric CT is an extensively used tool in diagnosing paediatric disease; however, children are more sensitive to radiation. Establishing the diagnostic reference level of paediatric CT examination is necessary to reduce the dose of CT in children and promote the optimisation of medical exposure. KEY POINTS: • The DRLs for 3 paediatric CT procedures (head, chest and abdomen) and 4 age groups (0- < 1, 1- < 5, 5- < 10, 10- < 15 years) were proposed in mainland China first time. • The examination parameter and dose for children need to be further optimised in China, especially to lower the tube voltage in paediatric CT.

[CT evaluation of bone remodeling in rabbit models with rhinosinusitis].

OBJECTIVE: To evaluate the findings of computed tomography (CT) as objective markers of bone remodeling in rabbit models with chronic rhinosinusitis. METHODS: Forty-eight rabbit models were established by vaccination of staphylococcus aureus. The rabbits were divided into 3 groups according to the time of infection: group A, B and C (4, 8, 12 weeks after infection), 16 rabbits in each group. Each group was subdivided into the medication administration team and the control team, 8 rabbits in each team. All the rabbits were examined by CT before vaccination to rule out the disease of nasal cavity and sinuses, and the CT images were used as the negative control. No interference was given to the control teams which were only examined again by CT when reached the end week. Dexamethasone sodium phosphate were administered to the medication administration teams 2 weeks before the end of experiment, and were examined by CT at the end. The images of both horizontal position and coronal position by reconstruction were obtained. The Hounsfield unit (Hu) of the bone which was the thickest position in each image were measured. The data was analyzed by SPSS 16.0 software. The Hu was analyzed statistically to compare the situation of the bone remodeling in different periods and administration in the rabbit models with CRS. RESULTS: Average Hu (x±s) of normal rabbits was 810.0±99.7, average Hu at the end time: control team in group A was 964.0±84.6, medication administration team in group A was 833.0±92.5; control team in group B was 987.0±91.5, medication administration team in group B was 886.0±91.6; control team in group C was 1086.0±74.0, medication administration team in group C was 899.8±76.5. The Hu in all groups were higher than normal (t value were 2.747, 4.513 and 7.350 respectively, all P<0.05). No statistical difference was found between control teams of group A and B (t=0.423, P=0.667). The Hu in control team of group C was higher than group B (t=3.905, P=0.001); There was no statistical difference between medication administration teams of group A and B (t=0.892, P=0.384), and group B and C (t=0.886, P=0.385). The Hu of all medication administration teams in 3 groups were lower than all the control teams (t value were 2.717, 3.687, 8.379 respectively, all P<0.05). CONCLUSIONS: Bone remodeling was found in rabbit models with rhinosinusitis, and the phenomenon was more obvious if the period was lengthened. The Hu could reflect the degree of bone remodelling. Glucocorticoids could depress the bone remodeling in the rabbit models with rhinosinusitis.