Grid artifact reduction in radiography with arctan(1/2)-degree rotated grid

Abstract

In order to reduce the grid artifacts in the digital radiography with stationary antiscatter grids, artifact frequency detection schemes should be adopted and appropriate band-rejection filters should be applied. However, by rotating the grid angle for certain grid densities and sampling frequencies, the artifact frequencies can be placed near the boundary of the frequency domain, and then the grid artifacts can be easily alleviated by applying a simple low-pass filter without any estimates of the artifact frequencies. In this paper, we propose a grid artifact reduction algorithm, which is based on rotating the grid and applying a low-pass filter. For the sampling frequency 7.194 lines/mm, an optimal rotate angle is arctan(1/2) ≈ 26.57 • and the grid density is 102.2 lines/inch. Better performances are obtained for real x-ray images.

Removing grid artifacts from a two-dimensional crisscrossed grid in cone-beam computed tomography to enhance image quality

“…Additionally, the primary challenge in using X-ray grids in digital radiography is the presence of grid artifacts, such as shadows of the grid strips and moiré, which can reduce image quality [1][2][3]. Grid shadow artifacts frequently appear in X-ray images when the detector resolution is comparable to or greater than the grid strip spacing.…”

Patch Based Grid Artifact Suppressing in Digital Mammography

“…This method is easy to implement, but it was only tested on the infrared image. In order to minimize the damage from grid artifact reduction, Kim and Lee first analyzed grid artifacts with multiplicative model and rotated stationary grids and then removed grid artifacts by constructing the homomorphic filtering consisting of band-stop filters and one-dimensional low-pass filters for searching the optimal grid frequencies and angles [ 25 – 28 ]. Tang et al decomposed the image into several subimages using a multiscale two-dimensional discrete wavelet transform and the remove gridline signals by an automatic Gaussian band-stop filter [ 29 ].…”

Grid artifact reduction for direct digital radiography detectors based on rotated stationary grids with homomorphic filtering

“…Furthermore, for specific grid frequencies and angles, we can separably apply the homomorphic 1D LPFs in each axis of the spatial domain, and thus alleviate the grid artifacts with very low implementation complexity without using any frequency detection scheme. 29 This paper is organized in the following way. In Sec.…”