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KMID : 1131320140160020173
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Journal of Korean Society of Computed Tomographic Technology
2014 Volume.16 No. 2 p.173 ~ p.179
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The dose assessment due to a change in the helical scan and scout tube voltage on chest CT examination
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Kang Tae-Wook
Sin Sang-Wook
Kim Kyu-Ha
Seo Jeong-Jun
Jeong Jong-Sung
Kim Myeong-Gu
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Abstract
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Purpose : If you apply the automatic tube current modulation technique (ATCM) in chest CT examination,it has tried to request the change of dose through the CTDIvol when changing the size of the helical scan tube voltage and scout tube voltage.
Materials and methods : CT device is Discovery CT 750HD model GE Co., Using the Rando Chest Phantom consistsequivalent material - tissue for applying ATCM.
Was varied in 80, 100, 120, 140 kV tube voltage, one of the exposure conditions of scout, the tube current was applied ATCM to be fixed to 10 mA.Chest CT scan at the time the actual contact pressure tube for 80, 100, 120, 140 kV was changed by, the tube current is fixed tube current 200 mA(group A) and AutomA + SmartmA 10 ~ 700 mA(group B), AutomA + SmartmA 100 ~ 300 mA(group C) are repeated five times by dividing the measured value was evaluated CTDIvol.
Results : CTDIvol is not affected by changes in the scout tube voltage from Group A, helical scan study tube voltage increases to 140 kV at 80kV, was increased by a factor of four or more(r = 0.997, p <0.05).
In certain cases, was reduced up to 19% is CTDIvolhelicalscan tube voltage increases is scout in Group B(r=-0.475, p<0.05), same case, helicalscan tube voltage is decreased up to 17% is CTDIvol with the increase of tube voltage scout(r=-0.677, p<0.05).
In certain cases, an increase of 74% up to CTDIvolhelical scan tube voltage increases is scout in Group C(r=0.878, p<0.05), same case, helicalscan tube voltage is decreased up to 8% is CTDIvol with the increase of tube voltage scout(r=-0.223, p<0.05).
Conclusion : If not applied ATCM, change of scout tube voltage does not affect the CTDIvol, CTDIvol a tube voltage helicalstudy showed a proportional relationship. If you do not have a limit (10 ~ 700mA) mA range by applying the ATCM, CTDIvol decreased as tube voltage helicalscan and scout is increased. If you have limited (100 ~ 300 mA) mA range, CTDIvol was decreased as the scout tube voltage is increased, helicalscan tube voltage is reduced.
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KEYWORD
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scout , helical, automatic tube current modulation(ATCM), tube voltage , CTDIvol
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