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Scatter correction method for x-ray CT using primary modulation: Phantom studies
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10.1118/1.3298014
/content/aapm/journal/medphys/37/2/10.1118/1.3298014
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/2/10.1118/1.3298014

Figures

Image of FIG. 1.
FIG. 1.

The spatial form (left) and the Fourier form (right, semilog coordinates) of primary, scatter, primary plus scatter, and primary with a modulator plus scatter for a cylindrical object. Scatter alone has less high-frequency content than does primary alone (as shown in the first two rows). However, these two signals are overlapped in the Fourier domain (as shown in the third row). With a primary modulator, a significant signal increase (enclosed by the ellipses in the last row) is seen around , which is the contribution from the modulated primary.

Image of FIG. 2.
FIG. 2.

Geometric configuration of the x-ray system with the insertion of the primary modulator.

Image of FIG. 3.
FIG. 3.

Two modulators used in the phantom studies: (a) An aluminum modulator with a large blocker spacing and (b) a copper modulator with a small blocker spacing.

Image of FIG. 4.
FIG. 4.

The 1D horizontal profiles of the measured and estimated scatter signals on the CatPhan©600 phantom: (a) Using the aluminum modulator and (b) using the copper modulator with and without frequency downgrading. The SPR error is obtained by calculating the absolute difference between the measured SPR and the estimated SPR.

Image of FIG. 5.
FIG. 5.

Image reconstructions of the CatPhan©600 phantom from cone-beam scans with and without scatter correction. Reconstruction size: with for a pixel. Display window: [−300,630] HU: (a) The cone-beam image without scatter correction; (b) the fan-beam image (reference); (c) the cone-beam image with scatter corrected using the aluminum modulator; (d) the cone-beam image with scatter corrected using the copper modulator; (e) the cone-beam image with scatter corrected using the downsampled copper modulator (its modulation frequency is reduced to the same as that of the aluminum), and (f) the six contrast rods selected as ROIs for the quantitative analysis shown in Table II.

Image of FIG. 6.
FIG. 6.

Profiles of the reconstructed images in Fig. 5. The circular profiles are for a circle passing the centers of the rods shown in Fig. 5(f): (a) Circular profiles and (b) central vertical profiles.

Image of FIG. 7.
FIG. 7.

The whole chest phantom and the reconstructed size (circled area) in this study.

Image of FIG. 8.
FIG. 8.

Image reconstructions of the chest phantom in the plane. Reconstruction size: with for a pixel. Display window: [−770,630] HU: (a) The cone-beam image without scatter correction; (b) the fan-beam image (reference); (c) the cone-beam image with scatter corrected using a constant; and (d) the cone-beam image with scatter corrected using the proposed method with the copper modulator. The horizontal and vertical lines indicate the positions of the profiles in Fig. 10, which are also the positions of the slice and slice in Fig. 9. The mean values of the CT number in the rectangle area [shown in image (a)] are −230 HU for (a), 97 HU for (b), −113 HU for (c), and 78 HU for (d). The corresponding standard deviations are 33, 31, 36, and 47 HU, respectively.

Image of FIG. 9.
FIG. 9.

Image reconstructions of the chest phantom in the plane (left column) and the plane (right column), taken at the positions shown in Fig. 8(a). Reconstruction size: with for a pixel. Display window: [−770, 630] HU. (a) and (b) are the images without scatter correction; (c) and (d) are the images with scatter corrected using a constant; and (e) and (f) are the images with scatter corrected using the proposed method with the copper modulator.

Image of FIG. 10.
FIG. 10.

Profiles of reconstructed images in Fig. 8, taken at the lines shown in Fig. 8(a): (a) Horizontal profiles at row 345 and (b) vertical profiles at column 292.

Image of FIG. 11.
FIG. 11.

The 1D horizontal profiles of the measured and estimated scatter signals for the CatPhan©600 phantom with and without an annulus: (a) Without an annulus, (b) with the elliptical annulus, and (c) with the circular annulus.

Image of FIG. 12.
FIG. 12.

Image reconstructions of the Catphan©600 phantom with and without annulus. Reconstruction size: , with for a pixel. Display window: [−700,300] HU. The first column is for the Catphan©600 phantom without annulus; the second column is for the phantom with the elliptical annulus; and the third column is for the phantom with the circular annuls. (a)–(c) are the cone-beam images without scatter correction; (d)–(f) are the fan-beam images; and (g)–(i) are the cone-beam image with scatter corrected using the copper modulator.

Image of FIG. 13.
FIG. 13.

Profiles of reconstructed images in Fig. 12: (a) Without annulus, (b) with the elliptical annulus, and (c) with the circular annulus.

Tables

Generic image for table
TABLE I.

Imaging parameters of the physical experiments.

Generic image for table
TABLE II.

Mean, STD, and CNR in the selected ROIs of the CatPhan©600 phantom.

Generic image for table
TABLE III.

The RMSE, averaged CNR, and noise in the rods in Fig. 12.

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/content/aapm/journal/medphys/37/2/10.1118/1.3298014
2010-01-28
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Scatter correction method for x-ray CT using primary modulation: Phantom studies
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/2/10.1118/1.3298014
10.1118/1.3298014
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