Objective To assess the effects of different level iterative reconstructions (IR) on image quality of obese patients of 80 kV CT pulmonary angiography (CTPA).Methods Forty obese patients with clinically suspected pulmonary embolism were examined with CTPA,filtered back projection method (FBP) and three IR levels (iDose1,20％ IR/80％ FBP;iDose3,40％ IR/60％ FBP;iDose5,60％ IR/40％ FBP) to reconstruct images were used.The CT value of pulmonary artery trunk,upper lobe artery and lower lobe basal segment artery of right pulmonary were measured,and the image noise,SNR and CNR of four groups were calculated and compared.Results The image noise,SNR and CNR had significant difference in 4 groups (all P＜0.05),and the image noise had significant difference between each two groups (all P＜0.05),the SNR and CNR had statistical difference between FBP and iDose3,between FBP and iDose5 (P＜0.01).Conclusion Compared with FBP,80 kV combined with different level IR technologies can significantly decrease image noise and improve objective image quality in CTPA,the radiation dose that obese patients received can be reduced.

Objective To analyze the CT pulmonary angiography(CTPA) image quality and radiation dose of obesity patients with high and low tube voltage iterative reconstruction(IR) and the filtered back projection(FBP) reconstruct algorithm,and to explore the feasibility of low tube voltage IR algorithms in CTPA of obese patients.Methods Obese patients with suspected pulmonary embolism were randomly assigned into 80 kV or 120 kV group, and the images were treated with IR and FBP reconstructions.CT value of the basal segment of the right pulmonary artery, right upper lobe and main pulmonary artery were measured, and the average CT value of the pulmonary artery was further calculated, and the independent sample t test analysis was used.Results Comparing the CT value of the IR and FBP subgroup of two tube voltage groups, the differences were not significant (P>0.05), the differences of noise, signal noise ratio(SNR) and contrast noise ratio (CNR) were statistically significant (P<0.05), respectively.The CT value,noise,SNR and CNR of 80 kV group were significantly higher than those of the 120 kV group, and the differences were statistically significant (P<0.05), while the radiation dose were significantly lower than those of 120 kV group (P=0.000).Conclusion The CTPA image quality of 80 kV IR algorithm is significantly improved compared with the 120 kV FBP algorithm, and the radiation dose is significantly reduced, which could be used for CT pulmonary angiography in obese patients.

Objective To evaluate the correlation between CT perfusion blood volume (Lung PBV)and the degree of pulmonary embolism by CT pulmonary angiography (CTPA).Methods 1 65 patients with suspected pulmonary embolism underwent dual-ener-gy CT angiography,then the Lung PBV iodine distribution was analyzed by using a software algorithm.Consistent CTPA results evaluated by two experienced radiologists were taken as standard reference.After two months,the CTPA images were assessed by other two radiologists at random.The position and the number of perfusion defects,and (or)hypoperfusion were recorded.Results Of all 1 65 suspected patients,41 were diagnosed as pulmonary embolism with involved 1 64 segment arteries including part occlusion in 56 and complete occlusion in 108.Lung PBV showed perfusion defect in 141 pulmonary segment including 42 in patients with part occlusion and 99 in ones with complete occlusion.1 7 pulmonary segments were misdiagnosed with part occlusion in 9 and complete ones in 8.23 segments were misdiagnosed including part occlusion in 14 and complete ones in 9.The perfusion defect of Lung PBV was correlated to CTPA moderately or well (to part occlusion with r =0.508 and P =0.022;to complete ones with r =0.905 and P =0.000).Conclusion Dual-energy lung perfusion imaging is helpful for accurate assessment of abnormal blood flow distribution caused by pulmonary embolism,and improve the diagnosis.

Objective To explore value of CT features in diagnosis of traumatic diaphragmatic rupture.Methods A retrospective analysis was performed on totally 256 patients with suspected traumatic diaphragmatic rupture,among them 128 were confirmed after surgery.All patients underwent CT scan before surgery.The prevalence of CT findings were recorded,including diaphragm discontinuity or segmental non-recognition of diaphragm," collar" sign," intrathoracic herniation of abdominal contents" sign," dependent viscera" sign," dangling diaphragm" sign and " thickness of the diaphragm" sign.The sensitivity and specificity of each sign were calculated.Results The sensitivity of diaphragm discontinuity or segmental non-recognition of diaphragm,"collar" sign,"intrathoracic herniation of abdominal contents" sign,"dependent viscera" sign,"dangling diaphragm" sign and "thickness of the diaphragm" sign of diaphragmatic rupture was 75.00％ (96/128),84.37％ (108/128),78.13％ (100/128),76.56％ (98/128),54.68％ (70/128) and 46.87％ (60/128),respectively.The specificity was 93.75％ (120/128),98.43％ (126/128),98.43％ (126/128),99.21％ (127/128),93.75％ (120/128) and 84.38％ (108/128),respectively.The sensitivity and specificity of overall MSCT signs was 92.18％ and 100％,respectively.Conclusion CT features have high value in diagnosis of traumatic diaphragmatic rupture.

Objective To analyze CT imaging findings and pathological features of the thymic cyst.Methods The CT findings of 20 cases with thymic cyst confirmed by pathology were analyzed retrospectively.The analysis included the location,shape ,size ,density ,contour, unilocular or multilocular,with or without walls,enhancement and lesion periphery.The pathology results were compared to CT findings.Results All lesions were located in the anterior mediastinum,in which the location of left side in 12 cases,right side in 6 cases,median mediastinum in 2 cases.All lesions had clear border and unilocular,including round shape in 4 cases,oval shape in 8 cases,and irregular shape in 8 cases with triangular shape in 1 case,the size range was 2-6 cm.4 cases had obvious cyst wall.The CT value of the cyst had range of 4-53 HU,with 10 cases less than 10 HU and 10 cases greater than 10 HU.There was no enhancement within the cysts of 20 cases and the cyst wall had enhancement in 4 cases.All cases of pathological findings were confirmed as thymus cyst.Gross sample showed gray red or isabeling.The lesion was cystic in 18 cases,soft stereocyst in 2 cases,bright yellow liquid within the capsule in 10 cases,butter fat in 5 cases,chylomicrons in 3 cases,unilocular in 19 cases and multilocular in 1 case (butter fat).Microscope showed the fibrous capsule wall in all cases,lined with squamous epithelium,ciliated columnar epithelium,monolayer columnar epithelium,in which could be seen normal thymus tissue.The thickness of the wall was no more than 0.5 cm,and multilocular wall smooth,no obvious inflammatory response in the surrounding.Conclusion CT image findings can clearly show the thymic cyst site,shape,size,density and boundaries,unilocular or multilocular,with or without walls.The CT image can reflect pathological features of the thymic cyst,and can provide accurate and reliable information for the clinic.

Objective To establish cardiac magnetic resonance imaging (MRI) derived left ventricular (LV) global and region function parameters in normal adults.Methods Twenty normal adults were examined with fast imaging employing steady-state (Fiesta) acquisition sequence of cardiac MRI,LV global function and LV region function were measured at basal,middle,apical level and at 16 LV segments.The regional function parameters among different levels and different segments of the same level were analyzed.Results (1) LV global function: end-diastolic volume (109.17 ± 19.52) ml ; end-systolic volume (37.76 ± 14.16) ml ; ejection fraction (65.93 ± 7.79) ％ ; wall thickening (83.24 ± 40.82) ％ ; longitudinal shortening (15.51 ± 3.78)％ ; fractional shortening (31.78 ± 9.55)％ ; end-diastolic mass (95.20 ± 19.95) g.(2) LV regional function: In each LV level,there was no significant difference in end-systolic wall thickness (P ＞ 0.05).End-diastolic wall thickness and wall thickening were similar between the middle and apical levels,but there were significant differences between middle and apical levels with the basal level (both P ＜0.05).End-systolic wall thickness of the middle and the apical level was similar,but there were significant differences between middle and apical levels with the basal level (both P ＜ 0.05).At the segments of the same level,end-diastolic wall thickness and the relevant regional function parameters between the segments of anteroseptal and inferoseptal at base and middle level were similar (P ＞ 0.05) ; the end-diastolic wall thickness was the largest and the WT was the minimal at the septal segments of three levels,and the difference were significant between the septal and other segments in the same level (P ＜0.05).Conclusions Fractional shortening and longitudinal shortening provide new indicators for assessing LV global function by cardiac MRI.There is obvious heterogeneity on LV regional function in normal adults,systolic function is the strongest in apical level and the weakest in spetal segments of LV.

Objective To evaluate the left ventricular (LV) radial and longitudinal systolic function in hypertrophic cardiomyopathy (HCM) patients by 3.0 T MR.Methods Sixteen HCM (HCM group) and twenty normal adults (normal group) were examined with fast imaging employing steady-state (FIESTA) acquisition sequence of cardiac MRI.LV ejection fraction (LVEF),longitudinal shortening (LS)and fractional shortening (FS)in three standard levels were measured to analyze LV radial and longitudinal systolic function.Results Asymmetric hypertrophy was detected in all HCM patients.The LVEF and FS were significantly higher while LS was significantly lower in HCM group than those in normal group(P ＜ 0.05or 0.01).FS at basal and middle levels were significantly higher in HCM group than in normal group (both P ＜0.01).FS in apex level was similar in the two groups(P =0.057).Pearson correlation analysis showed that LS was negatively related with the number of hypertrophy segments in HCM patients (r =-0.537,P =0.032).But there was no correlation between FS and the number of hypertrophy segments as well as FS and LS in HCM patients (r =-0.090,P =0.739 ; r =0.049,P =0.856).Conclusion The LV longitudinal systolic function was reduced but the LV radial systolic function remained unchanged in HCM patients,thus,LS changes could better reflect myocardial systolic function in HCM patients.

Objective To observe the value of CT radiomics nomogram for predicting Ki-67 expression of thymus epithelial tumors.Methods Totally 163 patients with thymus epithelial tumor,including 114 patients in training set and 49 patients in validation set were retrospectively enrolled.The patients were further divided into low expression(＜50％)and high expression(≥50％)subgroups according to Ki-67 index.Multivariate logistic regression analysis was performed to screen independent predicting factors of Ki-67 expression in thymus epithelial tumors,and clinical-CT model was constructed.The optimal radiomics features were extracted and screened based on chest plain and venous phase enhanced CT images,respectively.Then radiomics modelplain and radiomics modelenhanced were constructed,and Radscoreplain and Radscoreenhanced were calculated,respectively.The nomogram model was constructed based on clinical-CT model,Radscoreplain and Radscoreenhanced.Receiver operating characteristic curves were drawn,and the area under the curves(AUC)were calculated to evaluate the efficacy of each model for predicting Ki-67 expression of thymus epithelial tumors.Results Patient's gender and enhanced CT value of lesion were both independent predicting factors of Ki-67 expression in thymus epithelial tumors(both P＜0.05).The AUC of clinical-CT model,radiomics modelplain,radiomics modelenhanced and nomogram model for predicting Ki-67 expression was 0.736,0.814,0.836 and 0.857 in training set,which was 0.746,0.746,0.750 and 0.799 in validation set,respectively.Conclusion CT radiomics nomogram could be used to predict Ki-6 7 expression of thymus epithelial tumors.