Impact of iterative reconstruction technique and radiation dose on low-dose chest CT image quality

Objective To evaluate the impact of iterative reconstruction technique(iDOSE4)and radiation dose on image noise and contrast to noise ratio(CNR)of low-dose chest CT using a chest phantom.Methods A 64-detector spiral CT was used to scan a chest phantom with different tube current(30mAs,50mAs,70mAs)and tube voltage(80kV,100kV).CT original images were reconstructed with filtered back projection(FBP),iDOSE4 L3and L6algorithm,respectively.Then two radiologists measured CT value of ROI on reconstruction images,and average noise and CNR were calculated.Repeated measure analysis of variance was used to compare CT values and image quality among different radiation doses and reconstruction algorithm.Results There was no statistical difference of CT value of air and thorax lung field homogeneous among different radiation doses and reconstruction algorithms(all P0.05).With the increase of radiation dose,the average noise decreased and CNR increased gradually in the same reconstruction algorithm.In the same radiation dose,the average noise of images with FBP,iDOSE4 L3and L6reconstruction algorithm decreased and CNR increased gradually.Conclusion Changes of radiation dose and(or)reconstruction algorithm can not affect measurement accuracy of CT value.iDOSE4 algorithm can reduce average noise and improve image quality of low-dose CT image.