无线数字探测器的 DQE：不同滤波方案的性能比较。

DQE of wireless digital detectors: comparative performance with differing filtration schemes.

机构信息

Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705, USA.

出版信息

Med Phys. 2013 Aug;40(8):081910. doi: 10.1118/1.4813298.

DOI:10.1118/1.4813298

PMID:23927324

Abstract

PURPOSE

Wireless flat panel detectors are gaining increased usage in portable medical imaging. Two such detectors were evaluated and compared with a conventional flat-panel detector using the formalism of the International Electrotechnical Commission (IEC 62220-1) for measuring modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) using two different filtration schemes.

METHODS

Raw images were acquired for three image receptors (DRX-1C and DRX-1, Carestream Health; Inc., Pixium 4600, Trixell) using a radiographic system with a well-characterized output (Philips Super80 CP, Philips Healthcare). Free in-air exposures were measured using a calibrated radiation meter (Unfors Mult-O-Meter Type 407, Unfors Instruments AB). Additional aluminum filtration and a new alternative combined copper-aluminum filtration were used to conform the x ray output to IEC-specified beam quality definitions RQA5 and RQA9. Using the IEC 62220-1 formalism, each detector was evaluated at XN∕2, XN, and 2XN, where the normal exposure level to the detector surface (XN) was set to 8.73 μGy (1.0 mR). The prescribed edge test device was used to evaluate the MTF, while the NNPS was measured using uniform images. The DQE was then calculated from the MTF and NNPS and compared across detectors, exposures, and filtration schemes.

RESULTS

The three DR systems had largely comparable MTFs with DRX-1 demonstrating lower values above 1.0 cycles∕mm. At each exposure, DRX-1C and Pixium detectors demonstrated better noise performance than that of DRX-1. Zero-frequency DQEs for DRX-1C, Pixium, and DRX-1 detectors were approximately 74%, 63%, and 38% for RQA5 and 50%, 42%, and 28% for RQA9, respectively.

CONCLUSIONS

DRX-1C detector exhibited superior DQE performance compared to Pixium and DRX-1. In terms of filtration, the alternative filtration was found to provide comparable performance in terms of rank ordering of different detectors with the added convenience of being less bulky for in-the-field measurements.

摘要

目的

无线平板探测器在便携式医疗成像中得到了越来越多的应用。本研究使用国际电工委员会（IEC）62220-1 规定的形式，评估了两种平板探测器并将其与传统的平板探测器进行了比较，使用两种不同的滤波方案测量调制传递函数（MTF）、归一化噪声功率谱（NNPS）和探测量子效率（DQE）。

方法

使用具有良好特征输出的放射系统（飞利浦 Super80 CP，飞利浦医疗保健）获取三个图像接收器（DRX-1C 和 DRX-1，Carestream Health；Pixium 4600，Trixell）的原始图像。使用校准辐射计（Unfors Mult-O-Meter Type 407，Unfors Instruments AB）测量自由空气曝光。额外的铝过滤和新的替代铜-铝组合过滤用于使 X 射线输出符合 IEC 规定的光束质量定义 RQA5 和 RQA9。使用 IEC 62220-1 形式，在 XN∕2、XN 和 2XN 处评估每个探测器，探测器表面的正常曝光水平（XN）设置为 8.73 μGy（1.0 mR）。使用规定的边缘测试装置评估 MTF，同时使用均匀图像测量 NNPS。然后从 MTF 和 NNPS 计算 DQE，并在探测器、曝光和过滤方案之间进行比较。

结果

三个 DR 系统的 MTF 基本相当，DRX-1 的值在 1.0 个周期∕mm 以上较低。在每个曝光度下，DRX-1C 和 Pixium 探测器的噪声性能均优于 DRX-1。对于 RQA5，DRX-1C、Pixium 和 DRX-1 探测器的零频率 DQE 分别约为 74%、63%和 38%，对于 RQA9，分别为 50%、42%和 28%。