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Measurement of organ dose in chest CT examination using Monte Carlo simulation
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E.M.T. Harki   , A.T. Al-Kinani |
| , drathabalkinani@yahoo.com |
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Abstract: (15039 Views) |
Background: Exposure conditions in CT
examinations are quite different from conventional Xray.
In CT examination higher dose is given to patient
in comparison with the dose in other diagnostic
examinations. In order to calculate organ effective
dose in chest CT, Monte Carlo simulation has been
used in this study. Materials and Methods: The
Impact survey data were used to determine the
parameters related to patient dose. This was done by
correlating the measurements from the NRPB
scanners with the effective dose calculated, using the
CTDOSE software. Patient dose index in air (CTDIair)
was measured as function of tube exposure ranged
from 90 to 225mAs at constant kVp and slice
thickness, using a stack of TLD chips which was long
enough to fully encompass the dose profile that could
have been used. Results: Dose profile of each
exposure was measured with approximately Gaussian
distribution shape. The full width at half maximum
(FWHM) of these profiles was nearly equal, and on
average it was equal to 8 cm. Also the maximum
CTDIair for these profiles, as expected increased with
mAs ranging from 29.2 to 50.606 mGy. CTDIair was
measured by two methods using conversion
coefficient established by using software, based on
Monte Carlo simulations (CTDOSE) and the other was
measured in the area under the dose profile
distribution. Conclusion: The slice thickness
measured from FWHM and those thicknesses set by
the operator were nearly equal proving that the
measurements using TLD were accurate. The effective
dose for chest increased with increasing mAs. By
these measurements, it was also noted that the
maximum equivalent dose and sharpest slope
variation were for lungs, heart and breast respectively,
whereas the minimum equivalent dose with lowest
slope variation was related to thyroid, liver, spleen,
stomach wall and kidneys respectively.
Iran. J. Radiat.
Res., 2007 4 (4): 205-209 |
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| Keywords: CT X-ray, organ dose, Monte Carlo simulation. |
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Full-Text [PDF 557 kb]
(3453 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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