Objective To evaluate the diagnostic value of CT target scanning combining with changing position for pulmonary nodules in special location .Methods CT target scanning combining with changing position was performed in 22 patients with pulmo‐nary nodules adjacent to heart or in posterior costophrenic angle ,which were found with routine spiral CT scanning .For objective analysis , the signal‐noise‐ratio (SNR) and contrast‐noise‐ratio (CNR) of lung were calculated .In terms of subjective assessment ,the image quality was rated on a 3‐point scale (0-2) for pulmonary inflation ,gravity‐dependent pulmonary perfusion and severity of artifacts , respectively .The CT features of pulmonary nodules were compared between different scanning techniques .Moreover ,the diagnostic confidence for pulmonary nodules was evaluated .The paired t test ,Wilcoxon signed‐rank test and Kappa test were used for statisti‐cal analysis .Results In comparison with conventional spiral CT scanning ,CT target scanning combining with changing position im‐proved the subjective image quality scores (P<0 .01) ,increased the signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) , showed more detailed CT features (P<0 .05) ,and improved the confidence of diagnosis (P<0 .01) .Conclusion CT target scanning combining with changing position technique can show detailed features ,which should be recommended as the optimal scanning tech‐nique for pulmonary nodules adjacent to heart or in posterior costophrenic angle .

Objective To evaluate multi-slice CT (MSCT) features and pathological basis of lung cancer containing thin-walled airspace. Methods Thirty?five cases of pathologically confirmed lung cancer containing thin-walled airspace were retrospectively analysed with regard to clinical data, pathological types and MSCT features between 2012 and 2015.There were 35 cases(25 adenocarcinoma, 9 squamous carcinoma, 1 spindle cell tumor) in total. MSCT features were compared between the lesions with or without solid component .Fisher exact test was used for the statistical analysis. For dynamic follow-up CT scans, the lesion dynamic change was evaluated .Correlations between the pathological section and CT images of the 11 cases were analysed. Results These features accounted for more than 60% of all MSCT signs in 35 cases, including round shape in 28 cases(80.0%),lobulation in 32 cases(91.4%),multiple cysts in 27 cases(77.1%), irregular inner wall in 33 cases(94.3%)and septum in airspace in 31 cases(88.6%). Shape, spiculation, bronchus cut-off, blood vessel and bronchus passing through the airspace, and ground-glass opacity were significantly different between the lesions with or without solid component(P<0.05).The frequency of spiculation(11 cases) and bronchus cut-off(12 cases) in mixed solid lesions was higher than that in lesions without solid component(1 case, respectively).The frequency of irregular shape(6 cases),blood vessel passing through the airspace(12 cases),ground-glass opacity(13 cases)and bronchus passing through the airspace(7 cases) in lesions without solid were higher than that in solid mixed lesions(1, 1, 5, 3 cases respectively).The pathological basis of the formation of thin-walled airspace was obvious central necrosis in solid lesions and emphysematous change due to the tumor cells diffused along the inner airspace wall and the alveolar wall destruction.Five lesions were with progressive wall thickening and increased size of the airspace,and two lesions were with decreased size of the airspace and enlarged nodules in followed CT.One case of lung cancer with thin-walled airspace evolved from ground glass nodule. Conclusions The CT manifestation of lung cancer containing thin-walled airspace was characteristic.The pathological basis of the thin-walled airspace was various.

Objective To evaluate the impact of different reconstruction parameter setting of knowledge-based iterative model reconstruction (IMR) technique on image quality of low-dose hepatic contrast-enhanced CT.Methods Forty patients underwent hepatic contrast-enhanced CT scanning were enrolled.Plain CT and triphasic contrast-enhanced CT scans,including hepatic arterial phase,portal-venous phase and delayed phase were performed.Low-dose scan was used in delayed phase,with tube voltage of 80 kV and tube current of 150 mAs.Images of delayed phase were reconstructed with both filtered back projection (FBP) and IMR techniques.Parameter setting applied in IMR reconstructions consisted of body routine and body soft tissue modes with three levels (Level 1-3),so 6 subgroups (R1,R2,R3,S1,S2,S3) were included.Subjective and objective evaluations of image quality were compared among those groups.Subjective evaluations included the scores of low contrast detectability (LCD),image distortion (ID) and diagnostic confidence (DC).Objective evaluations included image noise,signal to noise ratio (SNR) and contrast to noise ratio (CNR).Results There were statistical differences of scores in LCD,ID and DC among all the reconstruction parameter setting groups (all P＜0.01).The noise,SNR and CNR among different parameter setting groups had statistically significant differences (all P＜0.01).Except for subgroup S1 and subgroup R2,subgroup S2 and subgroup R3 (all P＞0.05),the other multiple comparisons showed significant differences (all P＜0.01).Conclusion IMR can improve image quality of low-dose hepatic contrast-enhanced CT.IMR reconstruction parameter setting of S1 and R2 are optimal for low-dose hepatic contrast-enhanced CT protocal.

Objective To investigate the impact of quantitative measurement for lung volume using iterative model reconstruction (IMR),hybrid iterative reconstruction (iDose4 )and filtered back projection (FBP),and to compare the image noise between different reconstruction methods.Methods 70 subjects were performed with low-dose chest CT scan (Philips Brilliance 256 iCT),and the original data were reconstructed with IMR (algorithm:Routine,SharpPlus,Soft Tissue,level:1 - 3 ),iDose4 and FBP respectively.We set less than -950 HU as emphysema threshold,calculated the total lung volume (TLV),total emphysema volume (TEV),emphysema index (EI)and objective image noise (OIN),and then compared the quantitative parameters and OIN between different groups.Results All parameters showed a significantly statistical difference (P =0.000)except TLV (P =1.000).The TEV and EI are significant higher in IMR-S group than in other groups.The OIN in IMR-S-L1 group was the highest,and the FBP group was the second-highest.OIN in iDose4 group was lower than that in IMR-S groups but higher than that in IMR-R and IMR-ST group.Conclusion SharpPlus algorithm of IMR will affect the quantitative measurement of lung volume under low-radiation-dose condition,and the OIN in IMR-S groups is obvious.Therefore SharpPlus 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 compared with idose4 and FBP.