Fetterly Kenneth A, Schueler Beth A
Mayo Clinic, Radiology, 201 1st Street SW Rochester, Minnesota 55905, USA.
Med Phys. 2003 Jul;30(7):1843-54. doi: 10.1118/1.1584045.
The image quality of a dedicated mammography computed radiography (CR) system was characterized. A unique feature of this system is that it collects image signals from both sides of the storage phosphor. Measurements of the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) were made. This work included improvements in our measurement methods to specifically account for the detrimental effects of system glare on the MTF and to accurately characterize the low-frequency NPS components. Image quality measurements were performed using a 25 kVp beam filtered with 2 mm Al and an exposure range of 1 to 100 mR (87 to 870 microGy). The DQE was found to decrease with increasing exposure due to an increased contribution of storage phosphor structure noise. The DQE of this system was compared to similar measurements made using a standard CR system. The dual-side read system demonstrated superior DQE compared to the standard system. The decrease in DQE with increasing exposure was more severe for the standard system than the dual-side read system. This finding suggests that the CR system noise was reduced for the dual-side read system compared to the standard system.
对专用乳腺钼靶计算机X线摄影（CR）系统的图像质量进行了表征。该系统的一个独特特点是它从存储磷光体的两侧收集图像信号。进行了调制传递函数（MTF）、噪声功率谱（NPS）和探测量子效率（DQE）的测量。这项工作包括改进我们的测量方法，以特别考虑系统眩光对MTF的不利影响，并准确表征低频NPS分量。使用用2毫米铝过滤的25 kVp光束和1至100 mR（87至870微戈瑞）的曝光范围进行图像质量测量。由于存储磷光体结构噪声的贡献增加，发现DQE随着曝光增加而降低。将该系统的DQE与使用标准CR系统进行的类似测量进行了比较。与标准系统相比，双侧读取系统表现出更高的DQE。对于标准系统，DQE随曝光增加的下降比双侧读取系统更严重。这一发现表明，与标准系统相比，双侧读取系统的CR系统噪声有所降低。
