The Feasibility Of The Application Of The Optimizing Pre-and Post-ASIR-V In Plain Chest CT Scanning

Objective:To investigate the effect of different weighted pre-and post-ASIR-V on imaging quality and radiation dose in the chest CT scanning.Methods:GE revolution CT has been used to scan the chest verisimilar model with spaced 10%interval pre-ASIR-V located in 0-100%consecutively.After the scanning,images were reconstructed with spaced 10%interval post-ASIR-V located in 0-100%at every different level of pre-ASIR-V.A total of 11×11 sets of images were obtained by scanning and reconstructing the phantom.Patients were divided into 2 groups according to the weight of the pre-ASIR-V of patients.Patient in group A was set as 30%,followed by 30%,40%,50%,60%,70%,80%,90%and 100%post-ASIR-V reconstruction after the scanning,which were denoted respectively as A3 group(pre-ASIR-V 30%,post-ASIR-V 30%),A4 group(pre-ASIR-V 30%,post-ASIR-V 40%),A5 group(pre-ASIR-V 30%,post-ASIR-V50%),A6 group(pre-ASIR-V 30%,post-ASIR-V 60%),A7 group(pre-ASIR-V 30%,post-ASIR-V 70%),A8 group(pre-ASIR-V 30%,post-ASIR-V 80%),A9 group(pre-ASIR-V 30%,post-ASIR-V 90%),A10 group(pre-ASIR-V 30%,post-ASIR-V100%).The pre-ASIR-V of patients in group B was set as 60%,followed by 60%,70%,80%,90%and 100%post-ASIR-V reconstruction after the scanning,which were denoted respectively as B6 group(pre-ASIR-V 60%,post-ASIR-V 60%),B7 group(pre-ASIR-V 60%,post-ASIR-V 70%),B8 group(pre-ASIR-V 60%,post-ASIR-V80%),B9 group(pre-ASIR-V 60%,post-ASIR-V 90%),B10 group(pre-ASIR-V 60%,post-ASIR-V 100%).Other parameters been set with 120 Kv tube voltage,automatic milliampere(10-600 m A),500ms rotation time,0.992:1 pitch,512×512 matrix in the same way,and the scanning layer is 5mm thick with 5mm interval.The DLP of the phantom and patients were recorded and used to calculate the effective dose.the age,gender,height,weight and BMI of patients were also recorded and used to calculate the BMI.All of reconstructed images were measured and recorded at the ADW4.6workstation in terms of Standard Deviation(SD)of CT value,Contrast-noise(SNR),and Signal-noise-ratio(CNR),and the subjective scores of the mediastinal and pulmonary windows were evaluated by two observers.Linear or curve fitting was performed for phantom's dose change followed by the pre-ASIR-V.And a multiple linear regression analysis was performed for the values change of SD,SNR and CNR followed by the fractional variation of pre-and post-ASIR-V.One-way Anova and Kruskal-Wallis rank sum test were used to compare the differences of images in SD,SNR,CNR and subjective scores from A3 to A10 groups and from B6 to B10 groups.Significant level of all statistical analyses is P<0.05.Results:The phantom's effective dose demonstrated a quadratic curvilinear decrease with the increase of pre-ASIR-V,Y=4.168X~2-9.491X+5.622(R2=0.999,P<0.001).The regression equations of SD,SNR and CNR followed with the pre-and post-ASIR-V are as follows:The value of SD=23.920+0.206X-0.277Y,(R~2=0.948,P<0.001);The valueCNR=0.0176-0.002X+0.003Y,(R~2=0.649,P<0.001).Where,X represents the weight of pre-ASIR-V,and Y represents the weight of post-ASIR-V.Within A3-A10 groups and B6-B10 groups,the value of SD decreased according to the increase of post-ASIR-V,While the value of SNR and CNR showed an increasing tendency.And the subjective scores of mediastinal windows increased at first and then decreased.Pairwise comparisons of SD within A3-A10 groups were significant different(P<0.05).Mutual comparisons of SNR were significant different except for adjacent groups(P<0.05).There were differences within A3-A10 groups in terms of CNR(P<0.05).And pairwise significant contrast happened in A3 and A8,A9,A10 respectively,in A4 and A8,A9,A10 respectively,in A5 and A8,A9,A10 respectively,in A6 and A9,A10 respectively,in A7 and A10,and in A8 and A10(P<0.05).On the subjective scores,there was only a significant difference in mediastinal window scores between A5,A6 and A10 group respectively(P<0.05),while there was no significant difference in pulmonary window scores(P=0.79).Pairwise comparisons of SD within B6-B10 groups were significant different(P<0.05).And mutual comparisons of SNR were significant different except for adjacent groups(P<0.05).There were differences within B6-B10 groups in terms of CNR(p<0.05).And pairwise significant contrast happened in B6 and B9,B10respectively,in B7 and B9,B10 respectively,and in B8 and B10(P<0.05).On the subjective scores,there was only a significant difference in mediastinal window scores between B6,B7 groups and A10 group respectively(P<0.05).While there was no significant difference in pulmonary window scores(P=0.30).Conclusions: The pre-ASIR-V can effectively reduce the scaning radiation dose.Excessive high pre-or post-ASIR-V weight will both lead to the degradation of image quality.In the case of plain chest CT scan,the image quality can be optimized by appropriately improving the the weight of post-ASIR-V in the base of low-intermediate pre-ASIR-V scanning.