Kunitomo Hiroshi, Ichikawa Katsuhiro, Higashide Ryo, Ohashi Kazuya
Department of Central Radiological Technology, Nagoya City University Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2012;68(8):961-9. doi: 10.6009/jjrt.2012_jsrt_68.8.961.
We measured physical image properties of a flat panel detector (FPD) system and a computed radiography (CR) system, targeting to a low dose range (reference dose: 2.58×10(-7) C/kg: to 1/20 dose). Input-output properties, pre-sampled modulation transfer functions (pre-sampled MTFs), and normalized noise power spectra for an FPD system equipped with a CsI scintillator (FPDcsi) and a CR system with an imaging plate coated with storage phosphor (CR) were measured at the low dose range for radiation quality of RQA3 (≍50 skV) and RQA5 (≍70 kV), and detective quantum efficiencies (DQEs) were calculated. In addition, in order to validate the DQE results, component fractions of Poisson and multiplicative and additive noise were analyzed using relative standard deviation analysis. The DQE values of FPDcsi were decreased with dose decrease, and contrarily to these, those of CR were increased. At the 1/10 and 1/20 doses for RQA3, the DQEs of FPDcsi and CR became almost the same. From the results of RSD analysis, it was proved that the main cause of DQE deterioration on FPDcsi are non-negligible additive (electronic) noise, and the DQE improvement on CR was caused by both of significant multiplicative (structure) noise and very low electronic noise. The DQE results were validated by comparing burger phantom images of each dose and radiation quality.
我们测量了平板探测器（FPD）系统和计算机X线摄影（CR）系统的物理图像特性，目标是低剂量范围（参考剂量：2.58×10⁻⁷ C/kg：至1/20剂量）。在RQA3（≍50 kV）和RQA5（≍70 kV）的辐射质量下，在低剂量范围内测量了配备碘化铯闪烁体的FPD系统（FPDcsi）和涂有存储磷光体成像板的CR系统的输入输出特性、预采样调制传递函数（预采样MTF）和归一化噪声功率谱，并计算了探测量子效率（DQE）。此外，为了验证DQE结果，使用相对标准偏差分析对泊松噪声、乘性噪声和加性噪声的成分分数进行了分析。FPDcsi的DQE值随剂量降低而降低，与此相反，CR的DQE值则升高。在RQA3的1/10和1/20剂量下，FPDcsi和CR的DQE几乎相同。从相对标准偏差分析结果证明，FPDcsi上DQE恶化的主要原因是不可忽略的加性（电子）噪声，而CR上DQE的提高是由显著的乘性（结构）噪声和极低的电子噪声共同导致的。通过比较各剂量和辐射质量下的汉堡体模图像，验证了DQE结果。
