Effects of Anti-Scatter Grid on Noise Power Spectrum at Different Dose Levels in Digital Mammography
Öz
Aim: The noise power spectrum (NPS) is an important quality
control parameter used to characterize the noise in a digital image in the frequency domain. The NPS is divided by the square
of the mean value of the pixels in the region of interest (ROI),
and this ratio is referred to as the normalized noise power spectrum (NNPS) and is used for noise analysis. This study aims to
determine the effect of using an anti-scatter grid on the NNPS
measurement.
Methods: The NNPS measurements are performed on five
Fujifilm Amulet Innovality full-field digital mammography
(FFDM) systems with and without a scatter reduction grid for
different dose levels ranging from 8 µGy to 400 µGy. The set of
three images of the uniform detector is acquired with and without a grid at each dose level for evaluation. All the preprocessed
(raw) images are analyzed using the ImageJ software-COQ
plug-in. The relative difference is preferred to determine the
changes in the NNPS.
Results: The maximum relative difference between the grid
and non-grid images is found to be 2.63 at 0.5 mm-1 spatial
frequency for a 20.31 µGy dose level.
Conclusion: The results show that NNPS fell with rising doses, whereas NNPS increased due to the decrease in the average
number of x-ray photons reaching the detector when the grid
is used.
Anahtar Kelimeler
: digital mammography, noise power spectrum, anti-scatter grid, noise.
Kaynakça
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