Objective:To investigate the effect of wide-body detector CT and spiral CT on image quality and radiation dose in thyroid examination.Methods:Ninety patients were randomly divided into three groups,Group A,B and C,with 30 patients in each group.Group A and B underwent the axial scan,and Group C underwent the spiral scan.For the enhancement scans,Group A and C were scanned after 3 s of threshold trigger,Group B was scanned after 4 s of threshold trigger,and the rest of the scan parameters were the same.The CT value,SD and air noise value of the normal thyroid tissue,common carotid artery,internal jugular vein and sternocleidomastoid muscle of the images in the arterial and venous phases of the three groups were finally measured.The exposure time,CT volume dose index(CTDIvol),dose length product(DLP),effective dose(ED),SNR and CNR were analyzed,and the overall image quality and artifacts of the images were evaluated.Results:Compared with the spiral scan,the exposure time,CTDI,DLP,ED were significantly lower in the axial scan(all P<0.001).CT values in the arterial phase in Group A were lower than those in Group C(P'<0.017),and the differences between Group B and C were not statistically significant(P'>0.017).SD,SNR,CNR of thyroid in the three groups were not statistically significant(all P'>0.017).The overall image quality score in the arterial phase in Group A was lower than that in Group C(P=0.045),and the difference between Group B and C was not statistically significant,and the differences in the overall image quality in venous phase and artifacts scores in the arterial and venous phases of the three groups were not statistically significant(all P>0.05).Conclusions:Compared with the spiral scan,the exposure time and radiation dose are lower in the wide-body detector CT.If the starting time of the arterial phase can be delayed properly,the effect of tissue enhancement and the image quality will be improved.
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