Age-related changes in CT attenuation of the thymus in children

Background. The CT appearance of the normal and abnormal thymus and its age -related changes have been described. However, there is no information rega rding the change in thymus CT attenuation values in children. Objective. The aim of the present study was to evaluate the normal CT atten uation of the thymus in infants and children and discover when the decline begins. Materials and methods. CT attenuation values of the thymus were retrospecti vely evaluated in 152 children between ages of 1 day and up to 14 years. Fo r each patient the mean value of the CT thymus attenuation was calculated a nd compared to CT attenuation of the chest wall and cardiac muscles. We als o examined the correlation between thymic attenuation, gender, and disease. The statistical analysis used was multivariate linear regression. Results. C-T attenuation of the thymus declines with age, beginning only after the Ist year of life. The thymus is more hyperdense than the chest wall and car diac muscles in infants less than 1 year. The thymus is denser in males tha n females, In malignant conditions, in infants less than 1 year, thymus CT attenuation is decreased. In older children thymus attenuation was similar to that for the chest wall and cardiac muscles. Conclusion. The decline in thymic CT attenuation with age is consistent wit h fatty infiltration of the gland. The measurements given in this report ca n serve as a basis for comparison to determine whether the thymus of a youn g child is normal or pathological.