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KMID : 1131320150170020037
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 2 p.37 ~ p.45
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A study on surface absorbed dose reduction by using contrast media and normal saline solution mixture
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Ko Ju-Seong
Im Sang-Muk
Gang Hwa-Won
Kim Dae-Hyeon
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Abstract
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Purpose : The purpose of this study lies in examining the screening effect of surface absorbed dose based on concentration of contrast media by manufacturing a screen with different contrast media concentration by mixing contrast media and physiological saline solution.
Materials & Methods : SOMATOM Definition (Siemens, Germany) was used for CT device and Atom Phantom (CIRS) and fluorescent glass element (GD-352M;Chiyoda Technol Japan) were used for measurement of dose. Also, dosimeter (FDG-1000;AGC, Techno Glass, Shizuoka, Japan) was used to measure absorbed dose and AAPM Phantom(Model 76-410, Nuclear Associates LTD) was used for image quality assessment. The comparison was conducted with mixture of previous screen BISMUTH (F&L Medical Products co, 0.060mmpb equivalent, USA) and contrast media 200 cc + normal saline solution 200 cc, contrast media 100 cc + normal saline solution 300cc. contrast media 50 cc + normal saline solution 350 cc. contrast media 25 cc + normal saline solution 375 cc, and contrast media 10 cc + normal saline solution 390 cc manufactured with mixture of contrast media and normal saline solution. The absorbed dose was measured by fluorescent glass dosimeter after placing contrast media mixed screen to the thorax of atom phantom and fluorescent glass dosimeter to the location of both nipples and lung field. Comparative measurement was conducted in order to compare the dose with the use of BISMUTH and without use of screen. The changes in doses accordingly with distance were measured by changing distance between the subject and screen into 0cm. 0.7cm, 1.4cm, and 2.1 cm and noise and uniformity were measured with same method as above experiment using AAPM Phantom for the measurement of image quality.
Result : Although reduction effect of surface absorbed dose was greatest with the use of contrast media 200 cc + normal saline solution 200 cc presenting 4.2 mGy, it has exceeded allowable range when measuring the uniformity. Although there was two-fold increase in surface absorbed dose for screen manufactured with made of contrast media 25cc + normal saline solution 375 cc in comparison with contrast media 200 cc+ normal saline solution 200 cc, the uniformity was measured within allowable range presenting the surface absorbed dose of 8.1 mGy. Also, there was surface absorbed dose reduction of 27% compared to surface absorbed dose 11.0 mGy scanned without screen. There were little changes in surface absorbed doses based on changes in distance between contrast media mixed screen and subject. In regards to noise assessment, it was measured to be the lowest presenting 11.7 without screen and the highest presenting 29.3 with the use of contrast media 200 cc+ normal saline solution 200 cc. With the screen, it was measured to be the lowest presenting 14.7 for contrast media 10 cc + normal saline solution 390 cc.
Conclusion : Surface absorbed dose reduction effect of 27% could be acquired compared to previous screen BISMUTH and uniform CT number could be obtained with the use of contrast media mixed screen 25 cc + 375 cc. It is believed that contrast media mixed screen will be of great assistance to surface absorbed dose reduction in case there is no previous screen.
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KEYWORD
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temporal bone CT, algorithm, FBP, ASIR
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