Flynn M J, Samei E
Department of Diagnostic Radiology, Henry Ford Health System, Detroit, Michigan 48202, USA.
Med Phys. 1999 Aug;26(8):1612-23. doi: 10.1118/1.598656.
The purpose of this study was to compare the image quality for a digital storage phosphor system using 1760 x 2140 (2k) and 3520 x 4280 (4k) image arrays. Measurements were made on a chest radiography system (Fuji FCR-9501) with special provisions to be operated in both 2k (standard) and 4k (HQ) modes. Presampled modulation transfer functions (MTF) were measured using an edge method. Noise power spectra (NPS) were determined for different input exposures by two-dimensional Fourier analysis. These measures along with exposure measurements and an x-ray spectral model were used to determine the frequency-dependent detective quantum efficiency DQE (f) of the system for the 4k and the 2k modes. The magnitude of the NPS for the 4k mode was about 1/2 that of the 2k mode. A MTF value of 0.5 was found at 1.25 cycles/mm for the 4k system and 1.50 cycles/mm for the 2k system. The 4k images had an extended MTF of 0.1 at 4.5 cycles/mm in the plate-scan direction. Overall, the DQE (f) of the 4k mode was slightly better than that for the 2k mode by about 0.02 due primarily to its better noise characteristics.
本研究的目的是比较使用1760×2140（2k）和3520×4280（4k）图像阵列的数字存储磷光体系统的图像质量。在一台胸部射线照相系统（富士FCR - 9501）上进行测量，该系统有特殊设置，可在2k（标准）和4k（高画质）模式下运行。使用边缘法测量预采样调制传递函数（MTF）。通过二维傅里叶分析确定不同输入曝光下的噪声功率谱（NPS）。这些测量结果连同曝光测量和X射线光谱模型一起用于确定该系统在4k和2k模式下与频率相关的探测量子效率DQE（f）。4k模式下NPS的幅度约为2k模式的1/2。对于4k系统，在1.25周期/毫米处发现MTF值为0.5，对于2k系统，在1.50周期/毫米处发现MTF值为0.5。4k图像在平板扫描方向上4.5周期/毫米处的扩展MTF为0.1。总体而言，4k模式的DQE（f）比2k模式略好，约高0.02，这主要归因于其更好的噪声特性。
