Singh V, Jain A, Bednarek D R, Rudin S
Toshiba Stoke and Vascular Research Center, University at Buffalo (SUNY), Clinical Translational Research Center, 8 floor, 875 Ellicott Street, Buffalo, NY 14203.
Proc SPIE Int Soc Opt Eng. 2014 Mar 19;9033:903362. doi: 10.1117/12.2043063.
Anti-scatter grids are used in fluoroscopic systems to improve image quality by absorbing scattered radiation. A stationary Smit Rontgen X-ray grid (line density: 70 lines/cm, grid ratio: 13:1) was used with a flat panel detector (FPD) of pixel size 194 micron and a high-resolution CMOS detector, the Dexela 1207 with pixel size of 75 microns. To investigate the effectiveness of the grid, a simulated artery block was placed in a modified uniform frontal head phantom and imaged with both the FPD and the Dexela for an approximately 15 × 15 cm field of view (FOV). The contrast improved for both detectors with the grid. The contrast-to-noise ratio (CNR) does not increase as much in the case of the Dexela as it improves in the case of the FPD. Since the total noise in a single frame increases substantially for the Dexela compared to the FPD when the grid is used, the CNR is degraded. The increase in the quantum noise per frame would be similar for both detectors when the grid is used due to the attenuation of radiation, but the fixed pattern noise caused by the grid was substantially higher for the Dexela compared to the FPD and hence caused a severe reduction of CNR. Without further corrective methods this grid should not be used with high-resolution fluoroscopic detectors because the CNR does not improve significantly and the visibility of low contrast details may be reduced. Either an anti-scatter grid of different design or an additional image processing step when using a similar grid would be required to deal with the problem of scatter for high resolution detectors and the structured noise of the grid pattern.
防散射格栅用于荧光透视系统，通过吸收散射辐射来提高图像质量。使用了一个固定的斯密特伦琴X射线格栅（线密度：70线/厘米，格栅比：13:1），搭配像素尺寸为194微米的平板探测器（FPD）和高分辨率CMOS探测器Dexela 1207，其像素尺寸为75微米。为了研究格栅的有效性，在一个改良的均匀头部模型中放置一个模拟动脉阻塞物，并使用FPD和Dexela对大约15×15厘米的视野（FOV）进行成像。使用格栅时，两个探测器的对比度都有所提高。Dexela的对比度噪声比（CNR）增加的幅度不如FPD提高的幅度大。因为使用格栅时，与FPD相比，Dexela单帧中的总噪声大幅增加，所以CNR降低。使用格栅时，由于辐射衰减，两个探测器每帧的量子噪声增加量会相似，但与FPD相比，Dexela由格栅引起的固定模式噪声要高得多，因此导致CNR严重降低。如果没有进一步的校正方法，这种格栅不应与高分辨率荧光透视探测器一起使用，因为CNR没有显著提高，低对比度细节的可见性可能会降低。对于高分辨率探测器的散射问题和格栅图案的结构化噪声，需要使用不同设计的防散射格栅或在使用类似格栅时进行额外的图像处理步骤来解决。
