Cahn R N, Cederström B, Danielsson M, Hall A, Lundqvist M, Nygren D
Lawrence Berkeley National Laboratory, Berkeley, California 94707, USA.
Med Phys. 1999 Dec;26(12):2680-3. doi: 10.1118/1.598807.
An evaluation of the dependence of detective quantum efficiency (DQE) on the incident energy spectrum has been made for mammography. The DQE dependence on the energy spectrum has been evaluated for energy-integrating detectors, photon-counting detectors, and detectors that measure the energy of each photon. To isolate the effect of the x-ray energy spectrum the detector has been assumed to be ideal, i.e., all noise sources are assumed to be zero except for quantum fluctuations. The result shows that the improvement in DQE, if the energy-integrating detector is compared to a single-photon counting detector, is of the order of 10%. Comparing the energy-integrating detector and the detector measuring the energy for each photon the improvement is around 30% using a molybdenum anode spectrum typical in mammography. It is shown that the optimal weight factors to combine the data in the case the energy is measured are very well approximated if the weight factors are proportional to E(-3). Another conclusion is that in calculating the DQE, a detector should be compared to one that uses ideal energy weighting for each photon since this provides the best signal-to-noise ratio. This has generally been neglected in the literature.
针对乳腺摄影，已对探测量子效率（DQE）对入射能谱的依赖性进行了评估。已针对能量积分探测器、光子计数探测器以及测量每个光子能量的探测器，评估了DQE对能谱的依赖性。为了分离X射线能谱的影响，探测器被假定为理想的，即除了量子涨落之外，所有噪声源都被假定为零。结果表明，如果将能量积分探测器与单光子计数探测器相比较，DQE的提升幅度约为10%。使用乳腺摄影中典型的钼靶阳极能谱，将能量积分探测器与测量每个光子能量的探测器相比较，提升幅度约为30%。结果表明，如果权重因子与E(-3)成比例，那么在测量能量的情况下，用于组合数据的最优权重因子能得到很好的近似。另一个结论是，在计算DQE时，应将一个探测器与对每个光子使用理想能量加权的探测器进行比较，因为这样能提供最佳的信噪比。这一点在文献中通常被忽略了。
