增感屏-胶片组合的噪声等价量子数和量子检出效率的测试  

The research on noise equivalent quanta and detective quantum efficiency of screen-film system

作　　者：谢晋东[1] 王昌元[1] 袁聿德[1] 张梦龙[1] 王健[1] 郑浩[1] 孙勇[1] 

机构地区：[1]山东泰山医学院放射系,泰安271000

出　　处：《中华放射学杂志》2002年第11期1041-1045,共5页Chinese Journal of Radiology

摘　　要：目的　测试增感屏 胶片组合的噪声等价量子数 (noiseequivalentquanta ,NEQ)和量子检出效率 (detectivequantumefficiency,DQE)。方法　用距离法测试T颗粒技术 (Green 40 0增感屏 /Kodakmgx 1胶片组合 )和MSCaWO4 增感屏 /FujiSuperRX胶片的特性曲线 ;矩形波法测试增感屏 胶片体系的调制传递函数 (modulationtransferfunction ,MTF) ;对 2种增感屏 胶片体系均匀曝光 ,用显微密度计扫描 ,通过快速傅立叶分析计算威纳频谱 (Wienerspectrum ,WS) ;由特性曲线的γ值、MTF、WS的测量计算NEQ ,并用入射量子数求DQE。结果　 (1)在空间频率为 0 6cycles/mm时 ,Green 40 0增感屏 /KodakMGX 1胶片组合的NEQ值为 1 148× 10 6 mm-2 ,是MSCaWO4 增感屏 /FujiSuperRX胶片组合的 0 65倍 ;在空间频率为 4 0cycles/mm时 ,Green 40 0增感屏 /KodakMGX 1胶片组合NEQ值为 0 3 2 9× 10 4mm-2 ,是MSCaWO4 增感屏 /FujiSuperRX胶片组合的 1 5 5倍。 (2 )在空间频率为 0 6cycles/mm时 ,Green 40 0增感屏 /KodakMGX 1胶片组合的DQE值为 0 2 2 4,是MSCaWO4 增感屏 /FujiSuperRX胶片组合的 1 6倍 ;在空间频率为 4 0cycles/mm时 ,Green 40 0增感屏 /KodakMGX 1胶片组合的DQE值为0 0 5 2 ,是MSCaWO4 增感屏Objective To examine the noise equivalent quanta (NEQ) and detective quantum efficiency (DQE) of screen-film system. Methods Green 400 screen-Kodak film and CaWO 4 screen-Fuji film were used in the study. The characteristic curves were obtained by distance method. The square wave technique was employed to determine the modulation transfer function (MTF). The Wiener spectrum (WS) was determined by Fourier analysis on uniformly exposed films. The NEQ and DQE were calculated from the characteristic curve slope, MTF, and WS measurements. Results (1) The NEQ value of Green 400 screen-Kodak film system was 1.148×10 6 mm -2 when the spatial frequency was 0.6 cycles/mm, and it was 0.65 times larger than that of CaWO 4 screen-Fuji film system; The NEQ value of Green 400 screen-Kodak film system was 0.329×10 4 mm -2 when the spatial frequency was 4.0 cycles/mm, and it was 1.55 times larger than that of CaWO 4 screen-Fuji film system. (2) The DQE value of Green 400 screen-Kodak film system was 0.224 when the spatial frequency was 0.6 cycles/mm, and it was 1.6 times larger than that of CaWO 4 screen-Fuji film system; The DQE value of Green 400 screen-Kodak film system was 0.052 when the spatial frequency was 4.0 cycles/mm, and it was 3.7 times larger than that of CaWO 4 screen-Fuji film system. Conclusion The Green 400 screen-Kodak film system has superior NEQ when the spatial frequency was more than 3.0 cycles/mm and has superior DQE among the total spatial frequency in comparison with CaWO 4 screen-Fuji film system.

关 键 词：增感屏-胶片组合 噪声 等价量子数 量子检出效率 测试 X线增感屏 

分 类 号：TH774[机械工程—仪器科学与技术]