This paper presents Dobbin's method to estimate the noise power spectrum using a screen film ... more This paper presents Dobbin's method to estimate the noise power spectrum using a screen film system. The one-dimensional spectral estimate was obtained by extracting thick and thin slices from two-dimensional noise power. The slices were made parallel to the primary axis of ROI, but did not include the axis. We measured NPS using one slice, two slices, four slices, eight slices,upper eight slices (a) and eight slices (b) of data in the 128×128 two-dimensional NPS space which were extracted to generate the one-dimensional NPS curves in horizontal and vertical directions and they were compared with Dobbin's method. Very little was found in the NPS shape with regards to the two-dimensional space only and the slice which contained one row and one column was sufficient to study NPS in the two-dimensional space Keywords—X-ray, Noise power spectrum, screen film system, fast Fourier transform
ABSTRACT Noise in medical images is recognized as an important factor that determines the image q... more ABSTRACT Noise in medical images is recognized as an important factor that determines the image quality. Image noise is characterized by noise power spectrum (NPS). We compared two methods of NPS determination namely the methods of Wagner and Dobbins on Lanex Regular TMG screen-film system and Hologic Lorad Selenia full field digital mammography system, with the aim of choosing the better method to use. The methods differ in terms of various parametric choices and algorithm implementations. These parameters include the low pass filtering, low frequency filtering, windowing, smoothing, aperture correction, overlapping of region of interest (ROI), length of fast Fourier transform, ROI size, method of ROI normalization, and slice selection of the NPS. Overall, the two methods agreed to the practical value of noise power spectrum between 10-3-10-6 mm2 over spatial frequency range 0-10 mm-1.
This paper presents Dobbin's method to estimate the noise power spectrum using a screen film ... more This paper presents Dobbin's method to estimate the noise power spectrum using a screen film system. The one-dimensional spectral estimate was obtained by extracting thick and thin slices from two-dimensional noise power. The slices were made parallel to the primary axis of ROI, but did not include the axis. We measured NPS using one slice, two slices, four slices, eight slices,upper eight slices (a) and eight slices (b) of data in the 128×128 two-dimensional NPS space which were extracted to generate the one-dimensional NPS curves in horizontal and vertical directions and they were compared with Dobbin's method. Very little was found in the NPS shape with regards to the two-dimensional space only and the slice which contained one row and one column was sufficient to study NPS in the two-dimensional space Keywords—X-ray, Noise power spectrum, screen film system, fast Fourier transform
ABSTRACT Noise in medical images is recognized as an important factor that determines the image q... more ABSTRACT Noise in medical images is recognized as an important factor that determines the image quality. Image noise is characterized by noise power spectrum (NPS). We compared two methods of NPS determination namely the methods of Wagner and Dobbins on Lanex Regular TMG screen-film system and Hologic Lorad Selenia full field digital mammography system, with the aim of choosing the better method to use. The methods differ in terms of various parametric choices and algorithm implementations. These parameters include the low pass filtering, low frequency filtering, windowing, smoothing, aperture correction, overlapping of region of interest (ROI), length of fast Fourier transform, ROI size, method of ROI normalization, and slice selection of the NPS. Overall, the two methods agreed to the practical value of noise power spectrum between 10-3-10-6 mm2 over spatial frequency range 0-10 mm-1.
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Papers by Zeki Darwish