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. 2010 Nov;37(11):6047-54.
doi: 10.1118/1.3501311.

A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging

Eric E Bennett  1 , Rael Kopace, Ashley F Stein, Han Wen
Affiliations

A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging

Eric E Bennett et al. Med Phys. 2010 Nov.

Abstract

Purpose: The purpose of this study is to develop a single-shot version of the grating-based phase contrast x-ray imaging method and demonstrate its capability of in vivo animal imaging. Here, the authors describe the principle and experimental results. They show the source of artifacts in the phase contrast signal and optimal designs that minimize them. They also discuss its current limitations and ways to overcome them.

Methods: A single lead grid was inserted midway between an x-ray tube and an x-ray camera in the planar radiography setting. The grid acted as a transmission grating and cast periodic dark fringes on the camera. The camera had sufficient spatial resolution to resolve the fringes. Refraction and diffraction in the imaged object manifested as position shifts and amplitude attenuation of the fringes, respectively. In order to quantify these changes precisely without imposing a fixed geometric relationship between the camera pixel array and the fringes, a spatial harmonic method in the Fourier domain was developed. The level of the differential phase (refraction) contrast as a function of hardware specifications and device geometry was derived and used to guide the optimal placement of the grid and object. Both ex vivo and in vivo images of rodent extremities were collected to demonstrate the capability of the method. The exposure time using a 50 W tube was 28 s.

Results: Differential phase contrast images of glass beads acquired at various grid and object positions confirmed theoretical predictions of how phase contrast and extraneous artifacts vary with the device geometry. In anesthetized rats, a single exposure yielded artifact-free images of absorption, differential phase contrast, and diffraction. Differential phase contrast was strongest at bone-soft tissue interfaces, while diffraction was strongest in bone.

Conclusions: The spatial harmonic method allowed us to obtain absorption, differential phase contrast, and diffraction images, all from a single raw image and is feasible in live animals. Because the sensitivity of the method scales with the density of the gratings, custom microfabricated gratings should be superior to off-the-shelf lead grids.

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Figures

Figure 1
Figure 1
Layout of the imaging device. From left to right: The x-ray tube, a set of glass beads (object), lead grid, and camera’s image plane.
Figure 2
Figure 2
Retrieval of harmonic images and differential phase contrast in the spatial frequency domain. (a) Raw image. The Moiré pattern in this image is due to subsampling to reduce the size of the figure for publication. (b) 2D spatial spectrum of raw image, (c) first-order harmonic image, and (d) zeroth-order (absorption) image.
Figure 3
Figure 3
Glass beads at different distances from the x-ray source. Top row: Absorption images for Ro=50 and 12 cm. Bottom row: Differential phase contrast images for Ro=50 and 12 cm.
Figure 4
Figure 4
Differential phase contrast images of glass beads acquired at the last three system geometry settings listed in Table 1. Top row: Images without camera correction with the grid set at three different distances from the camera. Bottom row: Images at the same distances but with correction for the camera’s point spread function.
Figure 5
Figure 5
The differential phase contrast signal at the top and bottom edges of the glass beads as a function of the grid-to-camera distance D, with and without camera’s PSF correction. The extraneous phase at low D values was an effect of the camera’s point spread function. The error bars indicate 1 standard deviation.
Figure 6
Figure 6
Mouse snout taken ex vivo with correction for camera PSF; (a) absorption image, (b) diffraction image, and (c) DPC image.
Figure 7
Figure 7
Images of rat paws taken in vivo, with camera’s PSF correction. (a) Back paw, absorption image; (b) back paw, diffraction image; (c) back paw, DPC image; (d) front paw, absorption image; (e) front paw, diffraction image; and (f) front paw, DPC image.
Figure 8
Figure 8
X-ray absorption vs. diffraction in the bone sections of the rat foot images. Error bars show one standard deviation.
See this image and copyright information in PMC

References

    1. Wernick M. N., Wirjadi O., Chapman D., Zhong Z., Galatsanos N. P., Yang Y. Y., Brankov J. G., Oltulu O., Anastasio M. A., and Muehleman C., “Multiple-image radiography,” Phys. Med. Biol. PHMBA7 48, 3875–3895 (2003).10.1088/0031-9155/48/23/006 - DOI - PubMed
    1. Kao T., Connor D., Dilmanian F. A., Faulconer L., Liu T., Parham C., Pisano E. D., and Zhong Z., “Characterization of diffraction-enhanced imaging contrast in breast cancer,” Phys. Med. Biol. PHMBA7 54, 3247–3256 (2009).10.1088/0031-9155/54/10/019 - DOI - PubMed
    1. Yokozeki S. and Suzuki T., “Shearing interferometer using grating as beam splitter,” Appl. Opt. APOPAI 10, 1575–1580 (1971).10.1364/AO.10.001575 - DOI - PubMed
    1. Clauser J. F., US Patent No. 5,812,629 (22 September 1998).
    1. Momose A., Kawamoto S., Koyama I., Hamaishi Y., Takai K., and Suzuki Y., “Demonstration of x-ray Talbot interferometry,” Jpn. J. Appl. Phys., Part 2 JAPLD8 42, L866–L868 (2003).10.1143/JJAP.42.L866 - DOI