基于照射侧采样技术的数字化 X 射线临床单元特性描述。

Characterization of a clinical unit for digital radiography based on irradiation side sampling technology.

机构信息

Fisica Medica, Ospedale di Sassuolo S.p.A., 41049 Sassuolo, Italy.

出版信息

Med Phys. 2013 Oct;40(10):101902. doi: 10.1118/1.4820364.

DOI:10.1118/1.4820364

PMID:24089904

Abstract

PURPOSE

A characterization of a clinical unit for digital radiography (FUJIFILM FDR D-EVO) is presented. This system is based on the irradiation side sampling (ISS) technology and can be equipped with two different scintillators: one traditional gadolinium-oxysulphide phosphor (GOS) and a needle structured cesium iodide (CsI) phosphor panel.

METHODS

The characterization was achieved in terms of response curve, modulation transfer function (MTF), noise power spectra (NPS), detective quantum efficiency (DQE), and psychophysical parameters (contrast-detail analysis with an automatic reading of CDRAD images). For both scintillation screens the authors accomplished the measurements with four standard beam conditions: RAQ3, RQA5, RQA7, and RQA9.

RESULTS

At the Nyquist frequency (3.33 lp/mm) the MTF is about 35% and 25% for CsI and GOS detectors, respectively. The CsI scintillator has better noise properties than the GOS screen in almost all the conditions. This is particularly true for low-energy beams, where the noise for the GOS system can go up to a factor 2 greater than that found for CsI. The DQE of the CsI detector reaches a peak of 60%, 60%, 58%, and 50% for the RQA3, RQA5, RQA7, and RQA9 beams, respectively, whereas for the GOS screen the maximum DQE is 40%, 44%, 44%, and 35%. The contrast-detail analysis confirms that in the majority of cases the CsI scintillator is able to provide improved outcomes to those obtained with the GOS screen.

CONCLUSIONS

The limited diffusion of light produced by the ISS reading makes possible the achievement of very good spatial resolution. In fact, the MTF of the unit with the CsI panel is only slightly lower to that achieved with direct conversion detectors. The combination of very good spatial resolution, together with the good noise properties reached with the CsI screen, allows achieving DQE on average about 1.5 times greater than that obtained with GOS. In fact, the DQE of unit equipped with CsI is comparable to the best alternative methods available which are based on the same technology, and similar to others based on an a-Se direct conversion detectors.

摘要

目的

介绍一种基于照射侧采样（ISS）技术的数字射线摄影临床单元（FUJIFILM FDR D-EVO）的特性。该系统可配备两种不同的闪烁体：传统的镥酸钇（GOS）和针状结构碘化铯（CsI）闪烁体板。

方法

通过响应曲线、调制传递函数（MTF）、噪声功率谱（NPS）、探测量子效率（DQE）和心理物理参数（使用 CDRAD 图像的自动读取进行对比度-细节分析）对特性进行了描述。对于两种闪烁屏，作者使用四种标准光束条件（RAQ3、RQA5、RQA7 和 RQA9）完成了测量。

结果

在奈奎斯特频率（3.33 lp/mm）下，CsI 和 GOS 探测器的 MTF 分别约为 35%和 25%。在几乎所有条件下，CsI 闪烁体的噪声特性均优于 GOS 屏。对于低能光束，GOS 系统的噪声可以增加到比 CsI 高 2 倍，这一点尤其明显。CsI 探测器的 DQE 在 RQA3、RQA5、RQA7 和 RQA9 光束下分别达到 60%、60%、58%和 50%的峰值，而 GOS 屏幕的最大 DQE 为 40%、44%、44%和 35%。对比度-细节分析证实，在大多数情况下，CsI 闪烁体能够提供比 GOS 屏幕更好的结果。

结论

ISS 读取产生的光的有限扩散使得实现非常好的空间分辨率成为可能。实际上，该单元使用 CsI 面板的 MTF 仅略低于直接转换探测器的 MTF。非常好的空间分辨率与 CsI 屏幕达到的良好噪声特性相结合，使得 DQE 平均提高约 1.5 倍，而 GOS 则实现了 DQE。实际上，该单元配备 CsI 的 DQE 可与基于相同技术的最佳替代方法相媲美，并且与基于硒直接转换探测器的其他方法相似。