Low-dose temporal bone CT in children: feasibility and image quality / 中华放射学杂志

ABSTRACT

Objective To analyze the feasibility of low dose temporal bone CT scans in children.Methods We obtained an optimized low-dose protocol in pre-experiment.The optimized protocol was used to examine 27 consecutive children.And then we retrospectively analyzed 27 examinations underwent a standard temporal bone CT scan acquired with 120 kV and 250 mAs.The interobserveragreement (Kappa value) for the 2 reviewers was calculated.The children were then divided into 4 subgroups according to age-specific effective dose conversion coefficient.The effective dose and image quality between the two protocols at the same age were compared by t test.Results The result of pre-experiment showed that radiation dose was significantly reduced when the parameters were 100 kV and 70 mAs.The interobserver agreement(Kappa value)was high (0.784).The interobserver agreement for both low-dose (0.641) and high-dose (0.815) groups were high.The effective doses of low-dose group were (0.707 5±0.029 1)(0,1.0 year old),(0.431 6±0.051 3)(1.1 to 5.0 years old); (0.309 5±0.138 4) mSv (5.1 to 10.0 years old) respectively.The effective doses of high-dose group were (3.166 2±0.462 5),(2.048 6±0.224 7),(1.492 0±0.422 1) mSv respectively.The difference between low and high dose groupswas significant in all of the subgroups (t=-10.612,-26.22,-79.84,P＜0.05).The image quality of low-dose group was75.5±0.6,75.6±3.5,75.4± 2.4 respectively.The image quality of high-dose group was78.8± 1.0,79.8± 2.2,79.5± 1.0 respectively.The effective dose for the forth subgroup (10.1 to 18.0 years old) wasl.194 9 and 0.228 1 mSv respectively.Though the image quality of low-dose group was significantly lower than that of high-dose group (t=-3.667,-26.220,-6.315,P＜0.05).All the images of low-dose scan were diagnostic.The image quality of both groups was 80.The radiation dose was 5 to 6 times lower thanstandard protocol used in daily work.The effective dose for infants is higher than the older children underwent the same protocol.Conclusion Low-dose temporal bone CT scan allows an accurate evaluation of middle and inner ear structures and is feasible in children.