Dose optimization in cardiac x-ray imaging
Gislason-Lee, Amber J. McMillan, C. Cowen, A.R. Davies, A.G.
Gislason-Lee, Amber J.
McMillan, C.
Cowen, A.R.
Davies, A.G.
Publication Date
2013-09
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2013-07-25
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Abstract
The aim of this research was to optimize x-ray image quality to dose ratios in the cardiac
catheterization laboratory. This study examined independently the effects of peak x-ray tube voltage
(kVp), copper (Cu), and gadolinium (Gd) x-ray beam filtration on the image quality to radiation dose
balance for adult patient sizes.
Methods: Image sequences of polymethyl methacrylate (PMMA) phantoms representing two adult
patient sizes were captured using a modern flat panel detector based x-ray imaging system. Tin and
copper test details were used to simulate iodine-based contrast medium and stents/guide wires respectively,
which are used in clinical procedures. Noise measurement for a flat field image and test
detail contrast were used to calculate the contrast to noise ratio (CNR). Entrance surface dose (ESD)
and effective dose measurements were obtained to calculate the figure of merit (FOM), CNR2/dose.
This FOM determined the dose efficiency of x-ray spectra investigated. Images were captured with
0.0, 0.1, 0.25, 0.4, and 0.9 mm Cu filtration and with a range of gadolinium oxysulphide (Gd2O2S)
filtration.
Results: Optimum x-ray spectra were the same for the tin and copper test details. Lower peak tube
voltages were generally favored. For the 20 cm phantom, using 2 Lanex Fast Back Gd2O2S screens as
x-ray filtration at 65 kVp provided the highest FOM considering ESD and effective dose. Considering
ESD, this FOM was only marginally larger than that from using 0.4 mm Cu at 65 kVp. For the 30 cm
phantom, using 0.25 mm copper filtration at 80 kVp was most optimal; considering effective dose the
FOM was highest with no filtration at 65 kVp.
Conclusions: These settings, adjusted for x-ray tube loading limits and clinically acceptable image
quality, should provide a useful option for optimizing patient dose to image quality in cardiac
x-ray imaging. The same optimal x-ray beam spectra were found for both the tin and copper details,
suggesting that iodine contrast based imaging and visualization of interventional devices could potentially
be optimized for dose using similar x-ray beam spectra.
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Citation
Gislason-Lee AJ, McMillan C, Cowen AR et al (2013) Dose optimization in cardiac x-ray imaging. Medical Physics. 40(9): 091911.
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