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19 March 2014An experimental study on the noise correlation properties of CBCT projection data
In this study, we systematically investigated the noise correlation properties among detector bins of CBCT projection
data by analyzing repeated projection measurements. The measurements were performed on a TrueBeam on-board
CBCT imaging system with a 4030CB flat panel detector. An anthropomorphic male pelvis phantom was used to acquire
500 repeated projection data at six different dose levels from 0.1 mAs to 1.6 mAs per projection at three fixed angles. To
minimize the influence of the lag effect, lag correction was performed on the consecutively acquired projection data. The
noise correlation coefficient between detector bin pairs was calculated from the corrected projection data. The noise
correlation among CBCT projection data was then incorporated into the covariance matrix of the penalized weighted
least-squares (PWLS) criterion for noise reduction of low-dose CBCT. The analyses of the repeated measurements show
that noise correlation coefficients are non-zero between the nearest neighboring bins of CBCT projection data. The
average noise correlation coefficients for the first- and second- order neighbors are 0.20 and 0.06, respectively. The noise
correlation coefficients are independent of the dose level. Reconstruction of the pelvis phantom shows that the PWLS
criterion with consideration of noise correlation results in a lower noise level as compared to the PWLS criterion without
considering the noise correlation at the matched resolution.
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Hua Zhang, Luo Ouyang, Jianhua Ma, Jing Huang, Wufan Chen, Jing Wang, "An experimental study on the noise correlation properties of CBCT projection data," Proc. SPIE 9033, Medical Imaging 2014: Physics of Medical Imaging, 90332R (19 March 2014); https://doi.org/10.1117/12.2043151