Comparison Of Image Quality In Chest Scan Using Different Noise Index Combined With Adaptive Statistical Iterative Reconstructions(ASIR And ASIR-V)

Objective To explore the application value and advantages of adaptive statistical iterative reconstructions.Methods 180 patients who were scheduled to undergo chest CT scan in the First Affiliated Hospital of Anhui Medical University were divided into three groups according to different noise index?NI?:12,15 and 18.They were labeled as A,B and C groups respectively.Each group was further divided into six groups according to ASIR and ASIR-V reconstructions,which were 30%,40%and 50%respectively.There were18 groups with each group contains 15 sets of images.All subjects were scanned from the neck to the lower and upper abdomen of the diaphragm,including the whole lung tissue.When using GE Discovery 750HD CT,the images is scanned according to the selected noise index,and then reconstructed according to the selected ASIR weight ratio,recording as A1?NI:12,ASIR30%??A2?NI:12,ASIR40%??A3?NI:12,ASIR50%??B1?NI:15,ASIR30%??B2?NI:15,ASIR40%??B3?NI:15,ASIR50%??C1?NI:18,ASIR30%??C2?NI:18,ASIR40%??C3?NI:18,ASIR50%?.When using Revoluition CT,the images is scanned according to the selected noise index and the ASIR-V weight ratio,recording as A4?NI:12,ASIR-V30%??A5?NI:12,ASIR-V40%??A6?NI:12,ASIR-V50%??B4?NI:15,ASIR-V30%??B5?NI:15,ASIR-V40%??B6?NI:15,ASIR-V50%??C4?NI:18,ASIR-V30%??C5?NI:18,ASIR-V40%??C6?NI:18,ASIR-V50%?.The following parameters are set to be consistent:the tube voltage is 120 kV,the tube current is automatic milliampere?10-500 mA?,the rotation speed of X-ray tube is 0.5 s,the pitch is 1.375:1,the matrix is 512×512,DFOV is 40.0cm.The scanning layer was 5 mm thick with 5 mm interval.The gender,age,height and weight of the scanned persons were recorded,and the corresponding BMI index was calculated.The formula was BMI=body weight/height ²?kg/m²?.The BMI of all subjects was controlled at 18.5?BMI?24.The dose length product?DLP?of each scanned person was recorded after scanning,and the value of ED was calculated according to the effective dose formula ED?mSv?=k(mSv·mGy^-1·cm^-1)×DLP?mGy·cm?.Statistical analysis of all the data after collation showed that there was statistical significance in defining P<0.05,whereas there was no statistical significance in defining P>0.05.Results 1)With the increase of noise index or weight ratio of adaptive statistical iterative reconstructions,the effective radiation dose received by the examinee gradually decreased,and there were statistical differences among the radiation dose groups.The maximum effective radiation dose was 3.86±1.03msV,i.e.group A1 ?NI:12,ASIR30%?.The lowest effective dose was about 0.97±0.76msV,i.e.group C6?NI:18,ASIR-V50%?.The results showed that the ASIR-V reconstructions could better reduce the effective radiation dose of the examinee.When the noise index is fixed,SD decreases with the increase of the weighting ratio of ASIR or ASIR-V reconstructions.The corresponding minimum SD values are 8.79±1.42 i.e.groupA3?NI 12,ASIR50%?and 8.51±1.48 i.e.groupA6?NI12,ASIR-50%?.The values of SNR and CNR increase continuously,which are respectively 3.93±0.75,8.23±0.53 and 4.16±0.56,8.45±0.91.3)When using the same iterative reconstructions?ASIR or ASIR-V?,the SD will increase with the increase of noise index,and the maximum values are 12.53±1.73 i.e.groupC4?NI 18,ASIR30%?and 11.42+1.47 i.e.groupC4?NI 18,ASIR-V30%?, respectively.At this time,the SNR and CNR are the smallest.The two physicians scored the images in all groups.It was found that the image quality under the ASIR-V technique was better than that under the ASIR technique.Conclusion Using two adaptive statistical iterative reconstructions combined with different noise indices for chest CT scanning can effectively reduce the radiation dose of the examinee,and the quality and clarity of the image can meet the needs of diagnosis.Whether ASIR or ASIR-V reconstructions,when the noise index is increased,the image noise will increase and the image quality will be reduced to a certain extent.Comparing with ASIR reconstruction,the new generation of iterative reconstruction ASIR-V,can significantly reduce the radiation dose of the examinee,and the quality of the image after scanning can be improved,still able to meet the requirements of clinical diagnosis.When using NI as 18,50%ASIR-V parameters in chest CT scan,the image quality and radiation dose can be optimized in this sudy.