Effect of changing mAs on radiation dose in CT for children skull

Objective To investigate the effect of changing mAs on radiation dose in the CT scanning for children skull and its clinic application value. Methods During CT scanning of children skull the scanning parameters were divided into 3 age groups according to the arrangement of CT scanner: ①0-1.5 year group, 150 mAs; ②1.5-6.0 year group, 200 mAs; ③6.0 - 16.0 year group, 250 mAs. For each group 40 cases were enrolled; in each group the unchanged scanning parameters were 120 kV, 6 mm × 3 mm collimator, 6 mm slice thickness. The dose parameters, CT dose index, weighted CTDIw and dose-length product DLP in each patients were recorded. Results ①The CTDIw in 3 groups was(21.296 ± 0.586) mGy, (27.990 ± 0.723) mGy and (35.665 ± 0.766) mGy, respectively(F = 4 264.944, P 0.001); ②The DLP value in 3 groups were (242.617 ± 24.277) mGy·cm, (356.262 ± 34.147) mGy·cm and (458.743 ± 20.993) mGy·cm, respectively (F = 638.654, P 0.001); ③When the scanning parameter reduced 50 mAs, the CTDIw decreased about 22.72 % and DLP decreased 27.12 %; when the scanning parameter reduced 100 mAs, the CTDIw decreased about 40.29 % and DLP decreased about 47.11 %. Conclusion As reducing the mAs value CT radiation dose can decrease obviously; during the CT examination for children skull, the mAs value can be reasonably reduce according to the age of children patients, thus this rule can be used as a basic method by the CT technologist for protection of children against radiation.