Keywords:
Education and training, Dosimetric comparison, Physics, Dosimetry, Computer Applications-3D, CT-Angiography, CT, Cone beam CT, Radiation physics, Lung, Cardiac
Authors:
K. Sakata1, D. Kawai1, A. Matuda1, K. Mitumoto1, T. Takakura1, K. Matsubara2, K. Koizumi1, K. Higashimura1; 1Kyoto/JP, 2Kanazawa/JP
DOI:
10.1594/ecr2013/C-1265
Results
[Results]
:The relationship between tube current and CTDIvol was shown by the following equation (See Slide No.8).
Large focus : CTDIvol = 0.0756 × tube current + 0.7424
Small focus : CTDIvol = 0.0774 × tube current + 0.1189
(In the measurement of CTDI100 , the coefficient of variation was within 5 %.)
:The relationship between tube current and DLP0 was also shown by the following equation (See Slide No.9).
DLP0 = 0.459 × tube current (average current value of first and last images for each scan) − 2.321
:The calculated and displayed DLP were in good agreement,
and the maximum relative error of the calculated and displayed DLP was 1.1% (See Slide No.10).In consideration of measurement error,
both DLP were in good agreement.
:In theory,
the calculated DLP values are higher than displayed DLP values because the DLP values displayed on CT console do not take account of over-scanning.
But the displayed DLP values for 3 patients were higher than the calculated DLP values contrary to our expectation.
:We think this was because the tube current for many slices reached the upper limit value which was 500 mA in these cases,
which increased the displayed DLP values which were determined based on the mean CTDIvol in scan length.