Objective The purpose of this study was to evaluate the effect of patient’s body mass index on applications of auto-matic tube voltage selection (ATVS)for contrast-enhanced abdominal CT.Methods 1 60 patients underwent contrast-enhanced ab-dominal CT scan were assigned into the study group (ATVS technique)and the control group (120 kVp)with equal size (both n =80)according to the scanning mode.The two groups were both divided into four subgroups according to BMI (A:BMI <18.5 kg/m2 ;B:BMI 18.5~23.9 kg/m2 ;C:BMI 24~28.9 kg/m2 ;D:BMI ≥29 kg/m2 ).Image quality were assessed and compared with Rank-sum test.Analysis of variance was used to compare differences in mean contrast-to-noise ratio (CNR)and image noise a-mong the two groups.Two sample t tests were used to compare the radiation dose.Results In the study group,tube voltage of 100 kVp were selected highest(78.75%)and distributed from subgroups A to D,accounting for 60%,80%,90% and 60% respectively, with average BMI of (23.71±3.1 9)kg/m2 .Compared to control group,the effective dose of study group from subgroups A to C re-duced by 35.09%,27.61% and 1 9.08% respectively(t=3.829,4.389,2.238,P =0.005,<0.001,0.025).Despite the higher image noise in study group,the overall image quality was acceptable.Conclusion The contrast-enhanced abdominal CT with AVTS technique can reduce radiation dose in patients with BMI smaller than 28.9 kg/m2 .

Objective To investigate the value of automatic spectral imaging mode selection and adaptive statistical iterative reconstruction(ASIR) in upper abdominal enhanced CT with low contrast agent dose, and to optimize the combination of monochromatic energy level and ASIR percentage.Methods 100 patients underwent upper abdominal enhancement CT were randomly assigned into control group (n=50) and study group (n=50).In the control group, tube voltage of 120 kVp and contrast medium of 450 mg I/kg were used with the images reconstructed using 40% ASIR.In the study group, CT spectral imaging with automatic spectral imaging mode selection and contrast medium of 300 mg I/kg were used,and monochromatic images (40-65 keV,intervals of 5 keV) were reconstructed using 40%-60% ASIR (intervals of 10%), respectively.CT value, image noise and contrast-to-noise ratio of the liver, pancreas, aorta and portal vein and radiation dose were compared using two independent samples t test.Overall image quality was assessed by Mann-Whitney U test.Results All image quality indexes in 60 keV with 40% ASIR, 55-60 keV with 50% ASIR in the study group were equal to or better than the control group.There was no significant difference in radiation dose between control group and study group.Conclusion Combined automatic spectral imaging mode selection with ASIR, upper abdominal enhanced CT with low contrast agent dose could improve image quality compared to 120 kVp with 40% ASIR, without increasing radiation dose.

Objective Toexplorethevalueofmonochromaticenergyimaginggeneratedfrom RevolutionCTindetectingcoronary plaquesindifferentconcentrationsofcontrastagent.Methods Sixtesttubesnumbered3,4,5,6,8and9inthephantom wereselectedand filledupwithdifferentconcentrationsofiodinesolutions(20,10,5,2.5,0,13mgI/mL,respectively),fishbonesimulatingcalcified plaqueandstreakyporksimulatinglipid/fibrousplaque.EachtubeunderwentspectralCTscan(studygroup,70keV monochromatic energyimaging)and120kVpCTscan (controlgroup)respectivelyinRevolutionCT.Theabilityofplaquedetectionwasevaluated subjectively,andfurtheranalysis was madeontheimages withascoregreaterthanorequaltothreepoints.One-way ANOVA and Bonferroni m ethod w ere used to co m pare the C T values and C N R in different tubes in the intra-group co m parison ,w hile paired t test and M ann-W hitney U testwereusedfortheinter-groupcomparison.Results TheoverallimagequalityofNo.4,5and9testtubes inbothgroupsmettheclinicaldiagnosticlevel.Intheintra-groupcomparison,No.5testtubeshowedhigherCNRofcalcifiedplaque andNo.9testtubeshowedhigherCNRoflipidplaqueandfibrousplaquethantheothers(t=4.105-29.214,allP<0.001).Whilein theinter-groupcomparison,thestudygroupshowedsimilarCNRofcalcifiedplaqueinNo.9testtube(t=-1.576,P=0.130)tothecontrol group,andhigherCNRintheothersthanthecontrolgroup(Z=-4.074--3.815,t=-14.782--3.520,allP<0.05).Conclusion Comparedwith120kVpCTimages,monochromaticenergyimagingat70keVfrom RevolutionCTshowedbetteroverallimagequality andcoulddisplaycoronaryplaquesbetterwiththecontrastagent concentrationfrom5mgI/mLto13mgI/mL.