Quantitative Analysis Of Lung Volume By Low Dose Multi-slice Spiral Computed Tomography

Part Ⅰ Quantitative analysis of emphysema based by low dose CT1.1 Preliminary application of computed tomography quantitative assessment in emphysema to normal people in subjective evaluation【Objective】 To explore the application value of CT quantitative assessment with emphysema to people who showed negative result in subjective evaluation in CT examination,and compare with the quantitative parameters of different groups.【Materials and Methods】 1231 cases who showed a negative result in subjective assessment in LDCT examination were collected,set lower than-950 HU in the end of inspiration as emphysema threshold,then calculated the total lung volume(TLV),total emphysema volume(TEV),emphysema index(EI)and 15 th percentile lung density(PD15).Equal or higher than 5% of EI was defined as emphysema,then divided into different groups by gender and age,calculated the detectable rate for different groups and compared with the quantitative parameters among them.【Results】 102 cases of emphysema had been detected in 1231 cases,which the ratio is 8.29%,76 cases in men,and 26 in women,which ratios are 9.93% and 5.58%,respectively.For gender,TLV,TEV,EI were significantly higher and PD15 was significant lower in men(P all<0.001).For age,all groups had no significant differences in TLV and PD15(P>0.05).TEV in group D(≥60y)was significantly higher than group B(40-49y)and C(50-59y),(P<0.05),but was no significant difference with group A(P>0.05).EI in group D was significantly higher than other 3 groups(P all<0.05).The proportion of men,smokers,second-hand smokers and the history of pack-years in emphysema group are higher than the contrast group.【Conclusion】 Computed tomography quantitative assessment in emphysema is valuable for clinical to those who is normal in subjective evaluation in CT examination.The degree of emphysema is more severious in males and elderly(≥60y),so wesuggested that taking quantitative analysis for emphysema routinely in elderly(≥60y),especially males.1.2 The logistic regression analysis of risk factors for emphysema based CT quantitative assessment【Objective】 To explore the incidence of the emphysema based CT quantitative assessment,so as to provide evidences for evaluating emphysema trend and taking corresponding prevention measures.【Materials and Methods】 1175 cases of volunteers who participated in the LDCT lung cancer screening and completed the questionnaire were collected and taken the quantitative assessment of emphysema,then the risk factors for emphysema were analyzed with the non-conditional logistic regression.【Results】 Logistic regression analysis results showed that heavy smoking(≥30 pack years),secondhand smoke exposure and history of chronic bronchitis are the main risk factors of emphysema in our study,and the factor of gender and age(≥60y)also affect the pulmonary emphysema in a certain extent.【Conclusion】 According to the results of the analysis on risk factor for emphysema,we could make some effective measures against emphysema in the high risk population,so as to reduce the incidence and perniciousness of emphysema.Part Ⅱ The lung volume quantitative research using iterative model reconstruction2.1 Low-Radiation-Dose CT: Quantitative research for lung volume using iterative model reconstruction【Objective】 To investigate the impact of quantitative measurement for lung volume using iterative model reconstruction(IMR),i Dose4 and FBP,and compare the image noise between different reconstruction methods.【Materials and Methods】 70 subjects were performed with low-dose chest CT scan(Philips Brilliance 256 i CT),the original data were reconstructed with IMR(algorithm:Routine,Sharp Plus,Soft Tissue.level: 1~3),hybrid iterative reconstruction(i Dose4)and filtered back projection(FBP)respectively.Set lower than-950 HU in the end of inspiration as emphysema threshold,and calculated the total lung volume(TLV),total emphysema volume(TEV),emphysema index(EI)and objective image noise(OIN),then compared the quantitative parameters and OIN between different groups.【Results】 All parameters showed a significantly statistical difference(P<0.001)except TLV(P=1.000).The TEV and EI are significant higher in IMR-S group than other groups.The OIN in IMR-S-L1 group was the highest,and the FBP group was the second-highest.OIN in i Dose4 group was lower than IMR-S groups but higher than IMR-R and IMR-ST group.【Conclusion】 Sharp Plus algorithm(IMR)will affect the quantitative measurement of lung volume under low-radiation-dose condition,and the OIN in IMR-S groups is obvious,therefore Sharp Plus algorithm is not recommended for quantitative analysis of lung volume.The Routine and Soft Tissue algorithm will not affect the quantitative measurement,and can distinctly reduce the OIN compare with idose4 and FBP.2.2 Ultralow Dose Chest CT: The influence of quantitative assessment in lung volume and image quality using iterative model reconstruction(IMR)【Objective】 To investigate the influence of quantitative assessment in lung volume and image quality under ultralow radiation dose condition by using iterative modelreconstruction(IMR).【Materials and Methods】 31 patients were prospectively enrolled and underwent scanning twice with low-dose CT(reference parameters,120 k Vp,50 m As)and ultralow-dose CT(reference parameters,120 k Vp,10 m As).The original data of low-dose group were reconstructed by FBP(contrast group),and the ultralow-dose group were reconstructed by FBP,i Dose4 and IMR(algorithm:Routine,Soft Tissue.level: 1)respectively.Calculated the lung volume quantitative parameters and objective image noise(OIN)for each group,and assessed the image quality using 5 point scale(poor to excellent),then compared the quantitative and qualitative parameters among all groups.【Results】 Compare with the contrast group,the accuracy of quantitative assessment were influenced in FBP and Soft Tissue group under ultralow-dose condition,while the i Dose4 and Routine group could keep the accuracy.The OIN in FBP-ULD group was the highest.Compared with FBP-ULD group,OIN reduced by 29.3%,55.4%,70.1% in i Dose4-ULD,IMR-R1-ULD,IMR-ST1-ULD groups,respectively.Compared with the i Dose4-ULD group,OIN reduced by 36.9%,57.7% in IMR-R1-ULD,IMR-ST1-ULD groups,respectively.The subjective image quality score in contrast group(FBP-LD)was the highest,but there was no significant difference among contrast group,IMR-R1-ULD and IMR-ST1-ULD(P all=1.000).And compared with other groups,the FBP-ULD group got the lowest scores(P all<0.001).The i Dose4–ULD group was higher than FBP-ULD group but lower than FBP-LD,IMR-R1-ULD(P all<0.01),but there was no significant difference between i Dose4–ULD group and IMR-ST1-ULD group(P=0.220).The blotchy appearance only existed in IMR groups,which more obvious in Routine group than Soft group(P<0.001).Blotchy appearance did not affected the overall image quality obviously.【Conclusion】 It is recommend using Routine algorithm(IMR)for lung volume quantitative analysis,which could not only keep the accuracy but also distinctly reduce image noise and improve image quality under ultralow dose condition.