High precision carbon-interspaced antiscatter grids: Performance testing and moiré pattern analysis

Recently, we have developed high precision carbon-interspaced antiscatter grids to be suitable for digital radiography (DR) by adopting a precise sawing process. For systematic evaluation of the grid performance, we prepared several sample grids having different grid frequencies (4.0 to 8.5 lines/mm) and grid ratios (5:1 to 10:1) and established a well-controlled test condition based upon the IEC standard. In this paper, we presented the performance characteristics of the carboninterspaced grids in terms of the transmission of primary radiation (Tp), the transmission of scattered radiation (Ts), the transmission of total radiation (Tt), contrast improvement factor (Cif), Bucky factor (B), and signal-to-noise improvement factor (SNRif). We also described the grid line artifact, known as a moiré pattern, which may be the most critical problem to be solved for the successful grid use in DR. We examined the factors that affect the moiré pattern, particularly the grid frequency and the grid rotation angle, by integrating the sample grids with an a-Se based flat panel detector having a 139 μm × 139 μm pixel size.