Objective To determine the fitting parameters for the Archer equation (using shielding transmission factor as variables and shielding material thickness as functions) and quadratic equation with one unknown (using lead equivalent as variables and shielding material thickness as functions) for common radiation protection shielding materials, enabling calculation of lead equivalent or required shielding material thickness. Methods The shielding transmission factor of red brick, lime-sand brick, barium sulfate protective coating, lead glass, and standard lead sheets was measured under narrow-beam X-ray exposure, with tube voltages ranging from 70 to 150 kV. The data of standard lead sheet was used as the reference for lead equivalent. Related parameters were fitted according to the Archer equation recommended by the National Council on Radiation Protection and Measurements Report No. 147 and quadratic equation with one unknown relating lead equivalence to shielding materials thickness. Results The coefficients of determination for the quadratic equation with one unknown of red brick, lime-sand brick, barium sulfate coating, lead glass exceeded 0.999 3. Under 120 kV X-rays, 1 and 2 mmPb were equivalent to 101.02 and 171.09 mm red brick, 121.21 and 204.43 mm lime-sand brick, 10.63 and 24.27 mm barium sulfate coating, and 4.21 and 9.39 mm lead glass. Conclusion The Archer equation and quadratic equation with one unknown from 120 kV or higher tube voltage conditions derived in this study can be applied to calculate lead equivalent or required thickness of shielding materials under both primary and scattered radiation, without linear extrapolation. They provide a basis for radiation shielding design in radiation diagnosis and treatment facilities and for occupational radiation hazard assessments.

Objective:To explore the effect of atlantoaxial fusion on the growth and development of children′s cervical spine.Methods:The clinical data of 12 children with atlantoaxial dislocation who underwent posterior atlantoaxial fusion at Department of Orthopaedics,the 909th Hospital of Joint Logistics Support Force of Chinese People's Liberation Army from June 2002 to September 2013 were retrospective analyzed. There were 7 males and 5 females,with age of (8.1±3.1)years (range:3 to 13 years).Nine cases were traumatic and 3 cases were congenital malformations,1 of the children had Down syndrome. All children underwent posterior atlantoaxial fusion. Furthermore,the information of the height and anteroposterior width of the cervical vertebral bodies and vertical growth rate of the fusion mass were collected from all patients immediately postoperatively and during the follow-up.The range of motion in cervical spine were collected preoperatively and during follow-up period. Data were compared using independent sample t test, paired sample t test and repeated-measurement. Results:All 12 children had regular follow-up within (122.4±25.3)months(range:65 to 163 months). The height and anteroposterior width of the cervical vertebral bodies were similar to these results with those in published reports of growth in normal children of the same age(all P<0.01). At the last follow-up,atlantoaxial fusion of 11 cases had substantial growth (vertical growth rate of the fusion mass:11 cases ≥10%, 1 case <10%);the range of motion in cervical spine was close to the normal level (flexion(55.2±5.0)°,extension (65.3±4.9)°,left bending (41.7±4.5)°,right bending (42.4±4.4)°,left rotation (66.4±5.6)°,right rotation (68.5±5.8)°). Conclusions:Atlantoaxial fusion surgery is satisfactory in the treatment of pediatric atlantoaxial dislocation.During the follow-up,the growth and development of the cervical spine is close to that of normal children of the same age.In long-term observation,it has been found that the operation has no negative effect on the growth and development of the children′s cervical spine.

Objective:To explore the effect of atlantoaxial fusion on the growth and development of children′s cervical spine.Methods:The clinical data of 12 children with atlantoaxial dislocation who underwent posterior atlantoaxial fusion at Department of Orthopaedics,the 909th Hospital of Joint Logistics Support Force of Chinese People's Liberation Army from June 2002 to September 2013 were retrospective analyzed. There were 7 males and 5 females,with age of (8.1±3.1)years (range:3 to 13 years).Nine cases were traumatic and 3 cases were congenital malformations,1 of the children had Down syndrome. All children underwent posterior atlantoaxial fusion. Furthermore,the information of the height and anteroposterior width of the cervical vertebral bodies and vertical growth rate of the fusion mass were collected from all patients immediately postoperatively and during the follow-up.The range of motion in cervical spine were collected preoperatively and during follow-up period. Data were compared using independent sample t test, paired sample t test and repeated-measurement. Results:All 12 children had regular follow-up within (122.4±25.3)months(range:65 to 163 months). The height and anteroposterior width of the cervical vertebral bodies were similar to these results with those in published reports of growth in normal children of the same age(all P<0.01). At the last follow-up,atlantoaxial fusion of 11 cases had substantial growth (vertical growth rate of the fusion mass:11 cases ≥10%, 1 case <10%);the range of motion in cervical spine was close to the normal level (flexion(55.2±5.0)°,extension (65.3±4.9)°,left bending (41.7±4.5)°,right bending (42.4±4.4)°,left rotation (66.4±5.6)°,right rotation (68.5±5.8)°). Conclusions:Atlantoaxial fusion surgery is satisfactory in the treatment of pediatric atlantoaxial dislocation.During the follow-up,the growth and development of the cervical spine is close to that of normal children of the same age.In long-term observation,it has been found that the operation has no negative effect on the growth and development of the children′s cervical spine.