Monnin P, Gutierrez D, Bulling S, Lepori D, Verdun F R
Institut universitaire de Radiophysique Appliquée (IRA), CH-1007 Lausanne, Switzerland.
Phys Med Biol. 2005 Oct 7;50(19):4541-52. doi: 10.1088/0031-9155/50/19/008. Epub 2005 Sep 13.
Three standard radiation qualities (RQA 3, RQA 5 and RQA 9) and two screens, Kodak Lanex Regular and Insight Skeletal, were used to compare the imaging performance and dose requirements of the new Kodak Hyper Speed G and the current Kodak T-MAT G/RA medical x-ray films. The noise equivalent quanta (NEQ) and detective quantum efficiencies (DQE) of the four screen-film combinations were measured at three gross optical densities and compared with the characteristics for the Kodak CR 9000 system with GP (general purpose) and HR (high resolution) phosphor plates. The new Hyper Speed G film has double the intrinsic sensitivity of the T-MAT G/RA film and a higher contrast in the high optical density range for comparable exposure latitude. By providing both high sensitivity and high spatial resolution, the new film significantly improves the compromise between dose and image quality. As expected, the new film has a higher noise level and a lower signal-to-noise ratio than the standard film, although in the high frequency range this is compensated for by a better resolution, giving better DQE results--especially at high optical density. Both screen-film systems outperform the phosphor plates in terms of MTF and DQE for standard imaging conditions (Regular screen at RQA 5 and RQA 9 beam qualities). At low energy (RQA 3), the CR system has a comparable low-frequency DQE to screen-film systems when used with a fine screen at low and middle optical densities, and a superior low-frequency DQE at high optical density.
使用三种标准辐射质量(RQA 3、RQA 5和RQA 9)以及两种增感屏,即柯达Lanex Regular和Insight Skeletal,来比较新型柯达超高速G型和当前柯达T-MAT G/RA医用X射线胶片的成像性能和剂量要求。在三种总光学密度下测量了四种增感屏-胶片组合的噪声等效量子(NEQ)和探测量子效率(DQE),并与配备通用(GP)和高分辨率(HR)磷光板的柯达CR 9000系统的特性进行了比较。新型超高速G型胶片的固有灵敏度是T-MAT G/RA胶片的两倍,在可比的曝光宽容度下,在高光学密度范围内具有更高的对比度。通过提供高灵敏度和高空间分辨率,新型胶片显著改善了剂量与图像质量之间的平衡。正如预期的那样,新型胶片比标准胶片具有更高的噪声水平和更低的信噪比,尽管在高频范围内,这一点通过更好的分辨率得到了补偿,从而获得了更好的DQE结果——尤其是在高光学密度下。在标准成像条件下(RQA 5和RQA 9光束质量下的常规增感屏),两种增感屏-胶片系统在调制传递函数(MTF)和DQE方面均优于磷光板。在低能量(RQA 3)下,当在低和中等光学密度下使用精细增感屏时,CR系统与增感屏-胶片系统具有相当的低频DQE,而在高光学密度下具有更高的低频DQE。