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KMID : 1131320140160020165
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Journal of Korean Society of Computed Tomographic Technology
2014 Volume.16 No. 2 p.165 ~ p.172
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A study on the evaluation of appropriate shield distance of gonad shield each pitch in chest CT applied AEC
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Hong Seok-Ho
Lee Jun-Hyub
Kang Seon-Young
Lee Yong-Jae
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Abstract
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Purpose : There is a dose reduction effect by gonad shield when scanning chest CT. But, dose can be increased by influence of overscanning length when applying AEC in topogram included in gonad shield. So, We investigated appropriate shield distance of gonad shield each pitch.
Materials and methods : 128 slice CT equipment (Somatom Definition flash, Siemens, Germany) was used and experimental subject was Lung-Man phantom. For the accuracy of shield distance 115 cm X-ray Ruler was taken. Blanket shield(0.5 mm Pb, Bar Ray, USA) was used for gonad shield. When applying AEC in topogram not included in gonad shield, and if there is no shield and there is shield in scan range or outside, we compared to dose difference. AEC was applied in topogram included in gonad shield and we investigated dose rate of change in CTDIvol and DLP value by 0.5, 0.75, 1, 1.25 and 1.5 pitch scanned and 1 cm by moving in the direction of the foot from the last post of scan range.
Results : We sustained that there was no change of dose when applying AEC in topogram not included in gonad shield, and if there is no shield and there is shield in scan range or outside. The more pitch was, the more overscanning length range was when applying AEC in topogram included in gonad shield and 0.5, 0.75, 1, 1.25, and 1.5 pitch scanned and 1cm by moving in the direction of foot from the last post of scan range. So, CTDIvol and DLP value also was increased. Appropriate shield distance of gonad shield was needed each pitch.
Conclusions : Dose was increased by influence of overscanning length in topogram included in gonad shield in chest CT applied AEC. So, shielding of appropriate shield distance was proposed each pitch.
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KEYWORD
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AEC , overscanning length , pitch , gonad shield
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