| Objective To compare the difference between several levels of iDose iterative reconstruction algorithm and filter back projection((FBP) on image quality of upper abdominal CT scan,to search one iDose level for relatively good image quality.Methods Sixty-two patients who performed upper abdominal CT scan on Philips 256 slice CT scanner with automatic current modulation technique(Z-DOM)from November 2014 to December 2014 in the General Hospital of Ningxia Medical were admitted in our study.Images were reconstructed by filter back projection. After CT scan, CT images of sixty-two patients were reconstructed by iDose1, iDose3, iDose5 respectively.Objective image quality,which is CT value,noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR) were measured on Extended Brilliance Workspace.Two radiologists evaluated subjective image quality,including subjective noise,artifacts,diagnostic confidence,the visibilities of small structures and the display of liver lesions.Comparing the difference of objective and subjective image quality for four diffferent reconstructed groups and the difference of objective and subjective image quality between iDose groups and FBP group respectively.Results(1)There were no significant difference between four groups( FBP, iDose1, iDose3, iDose5) for the CT value of liver/abdominal aorta(F=0.002~0.66, P>0.05).There were significant differences between four groups for the noise,SNR and CNR of liver/abdominal aorta(F=11.878~156.961,P<0.05).The noise increased successively in FBP, iDose1, iDose3, iDose5 groups,on the contrary,the SNR, CNR decreased successively in four groups.(2)There was significant difference between four groups for the subjective noise(H=8.76~9.02,P<0.05),there were significant differences between iDose groups and FBP group for the subjective noise(u=3.96~12.84,P<0.05),images noise were the lowest for iDose5 group.There were no significant differences between four groups for the artifacts,diagnostic confidence,the visibilities of small structures and the display of liver lesions(H=0.078~7.341,P>0.05),and there was no significant difference between iDose groups and FBP group for the artifacts(P>0.05),but there were significant differences between iDose groups and FBP group for the diagnostic confidence,the visibility of small structures(u=2.12~3.06,P<0.05).Conclusion iDose iterative reconstruction algorithm can reduce the image noise and improve the quality of images when compared to FBP,which does not mean that image quality becomes better and better with the increase of iDose level.Images were relatively better for iDose 3 group when considering the overall image quality.Objective To compare the difference of image quality for upper abdominal CT between routine dose scan reconstructed by filter back projection and low dose scan reconstructed by i Dose iterative reconstruction, so as to explore weather low dose CT scan combine with i Dose iterative reconstruction can satisfy the image quality and reduce radiation dose.Methods One hundred eighty six patients who performed upper abdominal CT scan on Philips 256 slices CT scanner with automatic current modulation(Z-DOM)from November 2014 to July 2015 in General Hospital of Ningxia Medical were admitted in our study.Patients were categorized into three groups(group A,group B,group C) according to their treatment order, group A performed routine dose CT scan and were reconstructed by FBP, the reference value of m As was 250, group B, C underwent low dose CT scan respectively,the reference value of m As decreased 20%(200),40%(150) respectively when compared to group A,images of group B were reconstructed by i Dose1 and group C were reconstructed by i Dose3.Objective image quality,which is CT value,noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR) were measured on Extended Brilliance Workspace,two radiologists evaluated subjective image quality,including subjective noise,artifacts,diagnostic confidence,the visibilities of small structures and the display of liver lesions.Comparing the difference of objective and subjective image quality between three groups(A, B, C) respectively.The volume CT dose index(CTDIvol) and dose length product(DLP) were recorded,effective dose(ED) and size-specific dose estimates were calculated(SSDE),comparing the difference of CTDIvol, DLP, ED and SSDE between three groups.In order to compare the difference of decreased magnitude of radiation dose for different body mass index(BMI), A, B and C group were dividied into three groups recpectively:BMI<20kg/m2;20-24.9kg/m2;BMI>24.9kg/m2.Results(1)There were significant differences between three groups for CT values and signal to noise of liver/abdominal aorta(F=3.331~5.125, P=0.007~0.038). There was significant difference between three groups for contrast-to-noise ratio of abdominal aorta(F=5.118,P=0.007),there were no significant differences between three groups for other objective quality(F=1.228~2.990,P=0.053~0.295).(2)There was significant difference between three groups for subjective noise(H=7.102~9.96,P<0.05),there was no significant difference between three groups for other subjective image quality(H=0.139 ~ 4.761, P>0.05).(3)There were significant differences between three groups for the CTDIvol, DLP, ED, SSDE(H=70.154~115.897,P=0.000).The radiation dose of different BMI groups scanned with 40% dose reduction decreased differently compared to routine dose scan,the decreased magnitude is the largest for patients whose BMI less than 20kg/m2,CTDIvol, DLP, ED and SSDE decreased 50.76%, 49.36%,49.36%,58.78% respectively,the decreased magnitude is the smallest for patients whose BMI more than 24.9kg/m2,CTDIvol, DLP, ED and SSDE decreased 41.91%, 39.66%, 39.66%, 35.00% respectively.Conclusion(1)Low dose CT scan reconstructed by iDose iterative reconstruction algorithm can satisfy the image quality and reduce the radiation dose of patients compared to routine dose CT scan reconstructed by FBP.(2)When the scanning parameter decreased, the lower the BMI,the more the decreased magnitude of radiation compared to routine dose CT scan. |
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