Abstract
In the past decade, phase-contrast imaging (PCI) has become a hot research with an increased improvement of the image contrast with respect to conventional absorption radiography. In this paper, effects of tube voltage (kVp) on propagation-based phase-contrast imaging have been investigated with two types of microfocus x-ray tubes, a conventional sealed x-ray tube with the focal spot size of 13 - 20 μm and an open x-ray tube with minimum focal spot size less than 2 μm. A cooled x-ray CCD detector with the pixel size of 24 μm was used to acquire digital images. Two thin plastic sheets with different thickness were used as radiography phantoms. Two different phenomena were observed for the two x-ray tubes. For the open tube, phase-contrast effect has a slight drop with the increasing of tube voltage, however, it is opposite for the sealed tube. A further investigation indicates that the variation of focal spot size causes the abnormal result for the sealed tube. It also shows that phase-contrast effect is more sensitive to focal spot size than tube voltage.
Highlights
Conventional x-ray imaging is based on the attenuation properties of an object, for some weak absorption objects, such as biological tissue, polymers, and fiber composites, the use of conventional x-ray imaging is limited due to poor image contrast
Two different phenomena were observed for the two x-ray tubes
Phase-contrast effect has a slight drop with the increasing of tube voltage, it is opposite for the sealed tube
Summary
Conventional x-ray imaging is based on the attenuation properties of an object, for some weak absorption objects, such as biological tissue, polymers, and fiber composites, the use of conventional x-ray imaging is limited due to poor image contrast. While the application of x-ray phase-contrast imaging can provide a way to generate the images with better image-contrast because the interaction cross-section of x-ray phase-shift is about a thousand times larger than that of absorption for soft tissues [1]. Wilkins and his colleague firstly developed a classical theory formula (PGW theory) [2] on propagation-based phase-contrast imaging (PB-PCI) in 1997. This PGW theory is based on the paraxial Fresnel–Kirchhoff diffraction for spatially coherent x-ray sources. According to the PGW theory, for a weak absorption and weak phase-shift object, I (x)
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