| Objective : To investigate the scanning project of low-dose spiral CT scanning in stomach ,initially.Materials and Methods:1. Object and equipment40 cases of gastric cancer subject,who were confirmed by gastroscope before CT scanning,SomatomEmotion single spiral CT。2. Examination method(1) Preparation and technique:40 cases of gastric cancer subject were divided randomly into four group(80mAs in group one,50mAs in group two,30mAs in group three,24mAs in group four,every group had 10 cases).The same realm was scanned by regular dose CT(120mAs) scanning in all cases as control.Every subject was insisted to use oral water 800-1000ml.Scanning parameter:tube tension,130kV;layer thickness,8mm;bed speed,12.5mm;pitch,1.5mm; scanning time13~16s.Four different tube current (80 mAs,50 mAs,30 mAs,24 mAs) was respectively used to scan stomach.(2)Image observation and evaluation The reconstructed axial view image were observed under the suitable WW and WL. We would assess the image quality of every low dose taking the 120mAs groups as standard,The all image was observed blindly by 3 senior image doctor by oneself. They did not draw a conclusion until before coming a common result.(3) Measurement of radiation dose CT dose index ( CTDIw value ) was automatically displayed on CT screen, radiation dose unit:mGy.3. Statistical analysis2 Related Samples of Nonparametric Tests was adopted to compare the image quality of different intragroup (ie routine dose and different low dose). Mann-Whitney Test was adopted to compare the image quality of different low dose interclass.Results1.Taking the 120mAs groups as standard,80mAs,50mAs scan had no influence on the image structure definition of the stomach wall,the thicked stomach wall and stomach tumor,the space outside the cavity and clearness of tissue interface.Their variability of image quality had no statistically significant differences(P>0.05);accordingly,though 24mAs scan had statistically significant differences in the image quality(P<0.05),the pratical figure showed that the image quality had not influencded doctor to view and made diagnosis;Their variability of image quality had no statistically significant differences on the image structure definition of the stomach wall,the thicked stomach wall and stomach tumor with 30mAs(P>0.05);though 30mAs scan had statistically significant differences in the image quality of the space outside the cavity and clearness of tissue interface.(P<0.05),the pratical figure showed that the image quality had not influencded doctor to view and made diagnosis;All the low dose had statistically significant differences in the image quality each othe(rP<0.01),24mAs scan had statistically significant differences in the image quality comparing to other low dose groups(80mAs,50mAs,30mAs)(P<0.01),low dose groups had no statistically significant differences each other exclusive of 24mAs on the image structure definition of the stomach wall and the thicked stomach wall and stomach tumo(rP>0.01);24mAs scan had statistically significant differences in the image quality comparing to 80mAs on the image structure definition of the space outside the cavity and clearness of tissue interface,Accordingly the other low dose had not statistically significant differences in the image quality(P<0.01).2. Taking the 120mAs groups as standard,80mAs scan had no influence on the image structure definition of the liver and spleen,there was no statistical difference in intragroup;by 50mAs,30mAs,24mAs scan,the image quality was decreased,However,the pratical figure of 50mAs,30mAs scan showed that the image quality had not influencded doctor to view and made diagnosis in spite of poorer image quality;Accordingly ,24mAs scan had statistically significant differences in the image quality, And its poorer image quality had influencded doctor to view and made diagnosis; the other low dose had statistically significant differences in the image quality each other except that 50mAs and 30mAs had no statistically significant differences(P>0.01)。3.Comparing to 120mAs as the standard,the CTDIw(mGy)of 80mAs,50mAs,50mAs,24mAs was decreased by33%,58%,75%,80%。ConclusionDuring the screeing of gastric cancer subject,low-dose 30mAs spiral CT scanning in stomach obtained the same image quality and image message as the standard. And its CTDIw was decreased by 75%,so it can be a method of reducing radiaton dose to utmost gained by patients. And,decreasing tube current may be an effective means of reducing radiation dose.
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