Preliminary Evaluation Of Dose Reduction And Image Quality In HRCT Temporal Bone By Iterative Reconstruction

Part I The impact of iterative reconstruction on the image quality of routine dose temporal bone high resolution CT scanPurpose:To evaluate the impact of iterative algorithm on the image quality of routine dose temporal bone high resolution CT (HRCT) scan, to investigate the feasibility of iterative algorithm combined with low-dose technique in temporal bone HRCT.Methods:30 adult patients (body weight 50-90 kg) underwent the temporal bone HRCT with routine dose,3 groups of images were reconstructed with FBP algorithm and IR algorithm (iDose4 and IMR). The values [CT value, noise (SD, denoted as standard deviation of CT number), contrast-to-noise ratio (CNR) and signal to noise ratio (SNR)] of three groups were measured and compared. The image quality was evaluated subjectively by radiologists at double blinded.Result:There was no statistically significant difference in CT values among the 3 algorithms (P>0.05), the differences of SD value, CNR, SNR and subjective scores were statistically significant (P<0.05). The differences of the others (CT value, SD value, CNR, SNR and subjective scores) were statistically significant except CT values by pair wise-comparison (P<0.05). Compared with the FBP algorithm, the SD values of iDose4 and IMR decreased 20.31% and 43.84% respectively, the CNR increased 26.90% and 84.06% respectively, while SNR increased 26.74% and 84.76% respectively, the subjective scores improved 0.26 and 0.6 points separately. Compared to iDose4 algorithm, the SD value of IMR algorithm decreased by 29.52%, and SNR, CNR increased by 45.04%,45.77% respectively, and the subjective score was 0.34 points higher.Conclusion:The image quality was effectively improved by the combination of IR algorithm with routine dose in temporal bone HRCT, among which IMR algorithm was superior to iDose4.The study provided the basis for the feasibility of the combination of iterative algorithm with low-dose in temporal bone HRCT.Part II Preliminary evaluation of image quality and dose reduction in temporal bone HRCT by IR with low-dosePurpose:To discuss the image quality and dose reduction in temporal bone HRCT scanning with iterative algorithm and low-dose.Methods:60 adult patients (body weight 50-90 kg) supposed to undergo temporal bone HRCT were selected and randomly divided into 3 groups:A (120kV,200mAs),the images were reconstructed with FBP; B (100kV,200mAs) was done with iDose4; C (100kV, 100mAs) was done with IMR. The values [CT value noise (SD), contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR)] of three groups were measured and compared. The image quality was evaluated subjectively by radiologists at double blinded.Result:The CT value, SD value, CNR, SNR and subjective score of three groups were statistically significant (P<0.05). The CT values, SD values, CNR and SNR from the Group B were higher than the Group A and the subjective scores was lower; Excepting the CT value, the other items were no statistically significant (P>0.05). The CT value, CNR, SNR and the subjective score from Group C were higher than A and B, and the SD value was lower; All the five parameters (CT value, SD value, CNR, SNR and the subjective score)from the group C were statistically significant (P<0.05) to the rest groups. The effective radiation dose(ED) of three groups was 7.2,4.4 and 2.2mSv respectively; Compared with Group A, the ED from B and C were 38.89% and 69.44% lower respectively. Compared with Group B, the ED of C was 50.00% lower.Conclusion:The image quality was still ensured in the temporal bone HRCT scanning with IR algorithm(iDose4 and IMR) and low-dose, while the ED was dramatically reduced. The IMR algorithm is better than iDose4.