Relationship Between Safire Algorirhm And Quqlity And Radiation Dose In Dual-source Chest CT

PART1： Impact of SAFIRE algorithm on image quality andradiation dose of chest CTPurpose: To investigate the differences of image quality and radiationdose of chest CT between sinogram affirmed iterative reconstruction（SAFIRE）algorithm and filtered back projection（FBP）algorithm.Methods: Three sets of tube voltage values of80,100,120kV weredefaulted. Using automatic mAs care dose4D technology, a phantom wasscanned with dual-source CT（Somatom definition flash）. Data sets werereconstructed with FBP and SAFIRE（level1-5），and the noise and CTvalues of different structures of chest were compared. Two radiologistsevaluated the image quality independently. After each scanning, the doseweighted index （CTDIvol）anddose-lengthproduct（DLP）wererecorded,then effective dose was calculated and compared.Results: With the same scan condition, image noise of SAFIRE ofchest CT was significantly lower than that of FBP（P<0.05）. Among different scan conditions, regardless of FBP algorithm or SAFIRE algorithm,image noise of chest CT went lower when tube voltage increased. Imagenoise of different structures of chest changed with different reconstructionalgorithm and tube voltage. Both subjective and objective image qualityindicators of100kV/SAFIRE （level3）were better than those of120kV/FBP, and radiation dose reduced by37.61%.Conclusion: SAFIRE reconstruction algorithm can effectivelyimprove image quality and reduce radiation dose in chest CT. PART2： Evaluation of SAFIRE algorithm for lung noduledetection rate and accuracy in low-dose chest CTPurpose: To investigate the differences of pulmonary nodulesdetection rate between iterative reconstruction algorithm（sinogram affirmediterative reconstruction，SAFIRE）and filtered back projection algorithm（FBP）in chest CT, and to evaluate the detection accuracy.Methods: Three groups tube voltage values of80，100，120kV weredefaulted on dual-source CT，with automatic mAs care dose4D technology,chest phantom with simulated pulmonary nodules in was scanned，then images were reconstructed of FBP and SAFIRE （grade1-5） respectively.Third，chest CT images reconstructed of SAFIRE （grade1-5） and FBPwere compared in the detection rate of simulated pulmonary nodules，andtheir diameters and CT values were measured.Results: With the same tube voltage, no significant difference wasfound in the detection rate of simulated pulmonary nodules betweenSAFIRE（grade1-5）and FBP（P＞0.05），diameter deviation of simulatednodules of SAFIRE（grade3）was less than FBP，and the differences in theaverage CT value of the simulated nodules between SAFIRE （grade3）and FBP were not statistically significant (P＞0.05)；simulated nodulesdetection rate of100kV was equivalent to120kV，simulation nodules（-800HU and3mm）detection rate of80kV was less than120kV；astube voltage reduced，or simulated nodule diameter decreased，or thedensity of simulated nodules reduced， nodule’s diameter deviationincreased.Conclusion: SAFIRE compared with FBP, the capability of pulmonarynodules detection in different densities and different sizes is same，andSAFIRE algorithm is helpful for pulmonary nodules accurately display，canbe used for low-dose CT lung cancer screening program. PART3：Comparative study of SAFIRE and FBP algorithmfor clinical applications in Chest CT scans Purpose: To evaluate the image quality and radiation dose of sinogramaffirmed iterative reconstruction (SAFIRE) algorithm in chest CT.Methods:40outpatients undergoing chest CT examination with caredose4D technology were randomly divided into two groups, theconventional dose group (tube voltage120kV) reconstructed with FBPalgorithm, the low-dose group (tube voltage100kV) were reconstructedwith FBP and SAFIRE (level3) algorithm, chest CT image noise and imagequality was compared by two radiologists in a double-blind subjectiveevaluation. After each set of scanning, CT dose weighted index (CTDIvol)and dose-length product (DLP) was recorded, then effective dose wascalculated and compared.Results:100kV compared to120kV, mean effective dose of chest CTscans reduced by41.13%. In100kV chest CT,the image noise of SAFIRE(level3) algorithm was significantly reduced than that of FBP algorithm (P<0.05), the differences of CT values of organizational structures were notstatistically significant (P>0.05);the noise of lung tissue and subcutaneousfat of100kV/SAFIRE (level3) was lower than120kV/FBP (P <0.05), thedifferences of image noise of aortic and spinal soft tissue were notstatistically significant (P>0.05), the subjective image quality score of100 kV/SAFIRE (level3) and120kV/FBP was not significantly different.Conclusion: SAFIRE algorithm can effectively improve image qualityand reduce radiation dose in chest CT when meeting the clinical diagnosis.