Efficiency of antiscatter grids for flat-detector CT
Efficiency of antiscatter grids for flat-detector CT
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DOI：
10.1088/0031-9155/52/20/013
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发表时间：
2007-10-21
影响因子：
3.5
通讯作者：
Kalender, Willi
中科院分区：
文献类型：
--
作者：
Kyriakou, Yiannis;Kalender, Willi
平板探测器CT（FD-CT）扫描仪提供大体积覆盖范围，但因此比锥角较小的标准临床CT扫描仪更容易受到散射伪影的影响。FD-CT扫描仪可以采用防散射滤线栅作为散射抑制技术。我们评价了两种不同射野尺寸的三种标准荧光透视防散射滤线栅的散射抑制效率和图像质量改善。评估包括模拟和测量。关于模拟的混合模型相结合的确定性和蒙特卡罗（MC）计算与电网传输的分析计算相结合。为了验证我们的模拟，使用一个适应的准直器技术测量的散射-初级比（SPR）。通过模拟和测量获得的SPR与防散射网格和不防散射网格的一致性通常在10%以内。网格的使用通常不提供信噪比（SNR）的显著改善。在所有情况下，防散射网格导致杯状伪影显著减少。在SNR和由信噪比改善因子（SNRif）描述的散射强度的降低之间存在折衷。对于低散射或中等散射条件，必须通过更高的曝光量来补偿由通过滤线栅的初级透射减少引起的噪声增加。对于高散射条件，SNRif显著大于1;即可以达到高达50%的剂量降低。
Flat-panel detector CT ( FD-CT) scanners offer large volume coverage, but as a consequence are more susceptible to scatter artifacts than standard clinical CT scanners with smaller cone angles. FD-CT scanners can employ antiscatter grids as a scatter rejection technique. We evaluated three standard fluoroscopic antiscatter grids for two different field sizes with respect to scatter suppression efficiency and image quality improvement. The evaluations included simulations and measurements. Regarding the simulation a hybrid model combining deterministic and Monte Carlo ( MC) calculations was used combined with an analytical calculation of grid transmission. The scatter-to-primary ratio ( SPR) was measured using an adapted collimator technique in order to validate our simulations. The SPR obtained by simulations and measurements with and without antiscatter grids were in agreement typically within 10%. The employment of a grid does not generally provide a significant improvement of the signal-to-noise ratio ( SNR). Antiscatter grids led to a significant reduction of cupping artifacts in all cases. There is a trade-off between the SNR and the reduction of the scatter intensity described by the signal-to-noise improvement factor ( SNRif). For low- or medium-scatter conditions the increase in noise caused by the reduced primary transmission through the grid has to be compensated by a higher exposure. For high scatter conditions SNRif is significantly greater than 1; i.e. a decrease of dose of up to 50% can be reached.