Objective To assess the feasibility of low voltage with CARE dose 4D computed tomography pul-monary angiography(CTPA)by using image quality and radiation dosage.Methods 92 patients with clinically sus-pected pulmonary embolism(BMI:20 ~30kg/m2)were randomly divided into two groups(group A:n =46,80kV;groups B:n =46,100kV),the male and female of group A were equal to the number.Image quality score(given blind-ly by two senior radiologists ranged from 1 to 5 points).The CT value and standard deviation(SD)were measured and recorded in common pulmonary artery trunk,the main right pulmonary arteries,right low lobar arteries,and erector muscle of spine,calculated the SNR of ROI.Average CT value,signal noise ratio(SNR),CTDIvol,DLP were com-pared between the two groups.Used the CT dose index(CTDIvol)to compare radiation dosage between group A female and male.Results The agent average CT value and SD in arteries in group A [(510.27 ±115.45)HU,(50.06 ± 11.67)HU respectively]were higher than those in group B[(413.32 ±100.38)HU,(35.12 ±11.94)HU respective-ly],there were significant differences between the two groups(t =10.367,8.892,all P =0.000),but the SNR of ROI was (12.36 ±3.90),which was lower than (14.03 ±4.46)in group B,there was significant difference between the two groups(t =-5.238,P =0.001 ).Image quality score of transverse ection(1mm)in group A was (4.20 ± 0.29),which was lower than (4.91 ±0.36)in group B,there was significant difference(t =-20.23,P =0.000), but there was no significant difference in coronal section(5mm),coronal maximum intensity project(MIP)image and the capability of displaying the pulmonary artery branches(all P >0.05 ).The CTDIvol in group A was (2.03 ± 0.39)mGy,which was greatly lower than (5.04 ±1.02)mGy in group B,there was significant difference (P <0.05);but there was no significant difference between female and male in group A[male:(2.05 ±0.39)mGy;female:(2.01 ±0.38)mGy,t =-0.300,P >0.05].Conclusion Radiation dose can be decreased greatly(above 50%)in 80kV CTPA compared 100kV without compressing obviously the image quality for patients BMI 20 -30kg/m2 ,and no significant difference between the group A(80kV)different gender radiation dosage.