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Keywords:
Radioprotection / Radiation dose, Lung, CT, CT-Quantitative, Experimental investigations, Comparative studies, Technology assessment
Authors:
J. H. Kim, K. B. Lee; Seoul/KR
DOI:
10.1594/ecr2015/C-0891
Methods and materials
128 MDCT scanners that used in this study are Somatom Definition AS+(Siemens,
Erlangen,
Germany) and Optima 660(GE healthcare,
US),
Ingenuity(Philips,
Netherlands).
A Lung/Chest Phantom of model RS-330(Fluke Biomedical,
USA) was used.
Scan parameters of the chest examination protocol on each scanner are recommended.
All scan data are obtained with each automatic exposure control mode(Caredose4D in Somatom Definition AS+,
Auto mA in Optima 660,
iDose in Ingenuity).
Scan parameters of Siemens scanner are 120kV,
200mAs of reference image quality and that of GE scanner is 120kV,
10-400mA and 11.57 Noise index.
That of Philips scanner is 120kV,
142mAs,
21 dose right index.
The position of phantom was fixed on isocenter of scanner using positioning laser beam.
First,
we got normal topogram at first scan.
And then we scanned a chest range in two ways(cranio-caudal and caudo-cranial direction).
Slice thicknesses of each scan are 5mm and no gap.
In same way,
we got data from poor topogram.
Types of poor topogram are two.
Second scan was done by setting the shoulder level cut.
As a results,
this type can’t include the information while scanning was progressing from high density area(shoulder) to low density area(neck).
At third scan,
topogram was got by setting the Liver level cut instead of that of neck level.
this type of topogram had been cut while scanning was progressing from low density area(lung field) to high density area(liver).
After CT scan using three types of topogram,
we measured changes of mAs between cranio-caudal scan data and caudo-cranial scan data of each CT scan.
Then,
we compared changes of mAs in a chest scan using a normal topogram with those using an abnormal topogram.
Scan range of each CT scan is 30cm.
Figure 2,3 are example for Siemens scanner.