| Objective 1.Analysis the clinical use of 256MSCT Lower extremity arteries CTA which based on a knowledge-based Iterative Model(IMR).2.Analysis the difference between the IMR low dose scan and normal dose scan in image quality of 256MSCT Lower extremity arteries CTA.3.Analysis the significance in IMR 256MSCT lower extremity arteries CTA of low dose scan and the“ gold standard” DSA in lower extremity arterial stenosis rate.Methods 1.Case material We collect and analysis 31 cases of lower extremity limb patients in the second hospital of Dalian Medical university which included 26 males and 5 females in September 2015-January 2016.All the patients aged between 56-89 years old,and the average age was 69,at the same time the BMI index is around the normal range.All the cases were randomly divided into two groups which are 80 KV and 100 KV scan group,the group of 80 KV contained 17 cases and the group of 100 KV contained 14 cases.At the same time all the patients appear pale,cold,pain,edema and intermittent claudication,and the clinical suspected these cases as arteriosclerosis obliterans.2.Scanners and Methods We use the Philips 256 row X-ray computed tomography equipment(Brilliancei CT)to scan.The 80 KV group selected tube voltage of 80 KV,the m As set as automatic adjustment,and the Reduce dose of Dose Right Index is 14.While the 100 KV group selected the tube voltage of 100 KV,the m As set as automatic adjustment,and the Reduce dose of Dose Right Index is 20.Both groups should be scan from the renal artery level to the dorsal level.3.Image evaluation methods(1)Objective assessment of image quality: Take the measurement of each group’s interest areas of the lower extremity vascular about the vascular CT value,SD value,and the soft tissue CT.When we take the measurement,we take the mean value of both sides of the lower extremity.(If one side of the artery was occlusion take the other side to calculate,if both sides were occlusion we abandon this data)(2)Subjective evaluation of image: On this study we invited two experienced physicians in the diagnosis of cardiovascular diseases to give the subjective image quality scores of IMR,IDose3 and FBP.During the measurement we take the mean value of both sides of the lower extremity.(If one side of the artery was occlusion take the other side to calculate,if both sides were occlusion we abandon this data)4.Dose calculated Calculate the CTDIvol(m Gy),DLP(m Gy ? cm)and m As values.4.The stenosis rate assessment of the lower extremity arteries On this study we use double blind methods and invite two CTA and DSA experienced physicians in the diagnosis of cardiovascular diseases to evaluate the stenosis rates of 374 segments of the lower extremity arteries in the CTA IMR images and the DSA images of the 80 KV group respectively.And the two doctors’ results were summarized to compare this two kinds of DSA and CTA imaging methods.At the same time we calculate the sensibility and specificity of CTA.6.Statistical Methods We use SPSS statistical software(20.0)to analyze the data.We chose one-way ANOVA to analysis the difference between IMR,IDose3 and FBP statistics within the 80 KV and 100 KV groups on objective and subjective image quality.And the difference between the two groups 80 KV and 100 KV and dose difference betweenthese two groups we use t-test analysis.For the evaluation of lower extremity arterial stenosis we use Kappa test for analysis.Results 1.On the objective analysis of image Under 80 KV scanning conditions,the SNR,CNR and FOM values of IMR algorithm were higher than that of IDose3 and FBP algorithm,and the difference was statistically significant.Under 80 KV scanning conditions,the SD value of IMR algorithm were lower than that of IDose3 and FBP algorithm,and the difference was statistically significant.Since SNR,CNR and FOM is an index which reflect the excellent image quality,and the higher the value is,the better quality the image shows.At the same time the lower the SD value is the better the image quality is.So we can see that the IMR algorithm for image quality is superior to IDose3 and FBP algorithm.On the comparison of SNR,CNR,FOM,CT value and SD value between 80 KV and 100 KV groups: The SNR and CNR value of the two groups have no significant statistical difference.But the CT value and the FOM value have significant statistical difference.In conclusion the image quality between low-dose scanning and the normal dose scanning not only have no disadvantage,but also have advantages on some respects: because of the increased CT value and FOM value the image quality in 80 KV group is better than the 100 KV group.2.On the subjective analysis of image The results of this study also showed that the IMR subjective rates of both groups were higher than that of IDose3 and FBP.And the IMR subjective rates between the two groups have no significant statistical difference.We can conclude that on subjective image quality there is no difference between low dose(80KV)scan and normal dose(100KV)scan.3.The scanning dosages This study shows that the CTDIvol,DLP and ED value in 80 KV group reduced obviously than the 100 KV group and can reduced about 50%.4.The diagnosis of vascular Comparing the lower extremity arteries stenosis rate results in IMR images of80KV group with the gold standard DSA,the Kappa value of them is 82.2%,indicating that the 80 KV IMR low-dose group and“ gold standard ”DSA for the stenosis rate of lower extremity arteries have a consistency of 82.2%.We can say we have reached a very satisfactory degree of consistency.Also the sensibility and specificity of low dose IMR are 97.3% and 90.4%.Conclusions 1.Low-dose(80KV)lower extremity arteries CTA IMR technology in the diagnosis of lower extremity arterial stenosis rate and the “gold standard ”DSA technique has a good consistency and high sensitivity and specificity at the same time.Also it is a noninvasive diagnostic method.2.The lower extremity arterial CTA IMR technology is more advanced in low dose scan than traditional methods like HIR,FBP and has significantly improved the image quality. |
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