Feasibility study ofautomatic tube current modulation in low-dose thoracic imaging for young children with64-slice spiral CT

Abstract

：Objective To assess thefeasibility of using an automatic tube current modulation (ATCM)method to obtmn consistentimage quality with reduced radiation dose for young children undergoing chest scans with aset of 64-slice spiral CT.Methods Fifry young children underwent chest scans on a GE64-slice VCT with automatic tube current modulation.The noise index(NI)for this studygroup was set to 8 or 9 based on the proposed reference for pediatric chest imaging in ourhospital.We compared image quality and radiation dose for the study group with theage-matched control group of 50 young children acquired with standard protocol offixed-mAs(120 and 150 mAs for under 1 and above 1 year old,respectively).The volume CTdose index(CTDIvol)values were recorded for beth groups.Two experienced pediatricradiologists assessed image quality on a 5-point scale with 5 being the best.Scoresgreater than or equal to 3 were considered clinically acceptable.The degree ofinterobserver concordance was determined by Kappa statistics.Results The average objectiveimage noise and CTDIvol for control group was(4.78±0.58)and(6.68±0.62)mGy,respectively.Forthe study group the mean value of objective mAs wag(41.6±11.6)(20-79 mAs)with meanCTDIvol of(2.34 4±0.71)mGy,and the use of ATCM produced mean noise of(7.84±0.66).Theaverage CTDIvol with the use of NI of 8-9 was about 65% lower than that with the fixed mAssetting.The mean image quality score for the study group and control group was(3.46±0.40)and(4.65±0.46)respectively.Allstudies had acceptable image quality,and there was good inter-observer agreement indiagnostic acceptability(Kappa=0.474 and 0.536).Conclusion The automatic tube currentmodulation method could be used to obtain consistent image qualityfor young childrenundergoing 64-slice MSCT chest scans.With proper noise level setting(NI=8 or 9),one mayobtmn clinically acceptable images with much reduced radiation dose.