SU‐C‐209‐03: Anti‐Scatter Grid‐Line Artifact Minimization for Removing the Grid Lines for Three Different Grids Used with a High Resolution CMOS Detector

摘要

Purpose: Demonstrate the effectiveness of an anti‐scatter grid artifact minimization method by removing the grid‐line artifacts for three different grids when used with a high resolution CMOS detector. Method: Three different stationary x‐ray grids were used with a high resolution CMOS x‐ray detector (Dexela 1207, 75 μm pixels, sensitivity area 11.5cm × 6.5cm) to image a simulated artery block phantom (Nuclear Associates, Stenosis/Aneurysm Artery Block 76–705) combined with a frontal head phantom used as the scattering source. The x‐ray parameters were 98kVp, 200mA, and 16ms for all grids. With all the three grids, two images were acquired: the first for a scatter‐less flat field including the grid and the second of the object with the grid which may still have some scatter transmission. Because scatter has a low spatial frequency distribution, it was represented by an estimated constant value as an initial approximation and subtracted from the image of the object with grid before dividing by an average frame of the grid flat‐field with no scatter. The constant value was iteratively changed to minimize residual grid‐line artifact. This artifact minimization process was used for all the three grids. Results: Anti‐scatter grid lines artifacts were successfully eliminated in all the three final images taken with the three different grids. The image contrast and CNR were also compared before and after the correction, and also compared with those from the image of the object when no grid was used. The corrected images showed an increase in CNR of approximately 28%, 33% and 25% for the three grids, as compared to the images when no grid at all was used. Conclusion: Anti‐scatter grid‐artifact minimization works effectively irrespective of the specifications of the grid when it is used with a high spatial resolution detector. Partial support from NIH Grant R01‐EB002873 and Toshiba Medical Systems Corp.