Physical evaluation of prototype high-performance anti-scatter grids: potential for improved digital radiographic image quality

Grid evaluation for a screen-film x-ray system has typically included independent measurement of the opposing contrast improvement factor and Bucky factor. Neither of these metrics, however, is appropriate when assessing grid performance in a digital imaging environment. For digital radiographic systems, the benefit of an anti-scatter grid is well characterized by the quantum signal-to-noise ratio improvement factor (KSNR) provided by the grid. The purpose of this work was to measure KSNR of prototype grids designed for use with digital radiographic systems. The prototype grids had 5 mm tall lead septa, fiber interspace material, line rate N = 25 and 36 cm-1 and ratio r = 15 and 21, respectively. The primary and scatter transmission properties of the grids were measured, and KSNR was evaluated over a phantom thickness range of 10-50 cm. To provide a comparison, the KSNR of similarly constructed N44r15 and N80r15 grids is also reported. KSNR of the prototype grids ranged from 1.4 for the 10 cm phantom to 2.4 for the 50 cm phantom. For the thickest phantom, the SNR improvement factor of the prototype grids was 18-83% higher than that of the N44r15 and N80r15 grids, respectively. (note)