Bloomquist A K Maki, Mainprize J G, Mawdsley G E, Yaffe M J
Phys Med Biol. 2014 Nov 7;59(21):6621-35. doi: 10.1088/0031-9155/59/21/6621.
A reader study was conducted to tune the parameters of an observer model used to predict the detectability index (dʹ ) of test objects as a task-based quality control (QC) metric for digital mammography. A simple test phantom was imaged to measure the model parameters, namely, noise power spectrum,modulation transfer function and test-object contrast. These are then used ina non-prewhitening observer model, incorporating an eye-filter and internal noise, to predict dʹ. The model was tuned by measuring dʹ of discs in a four-alternative forced choice reader study. For each disc diameter, dʹ was used to estimate the threshold thicknesses for detectability. Data were obtained for six types of digital mammography systems using varying detector technologies and x-ray spectra. A strong correlation was found between measured and modeled values of dʹ, with Pearson correlation coefficient of 0.96. Repeated measurements from separate images of the test phantom show an average coefficient of variation in dʹ for different systems between 0.07 and 0.10. Standard deviations in the threshold thickness ranged between 0.001 and 0.017 mm. The model is robust and the results are relatively system independent, suggesting that observer model dʹ shows promise as a cross platform QC metric for digital mammography.
开展了一项读者研究，以调整用于预测测试对象可探测性指数（dʹ）的观察者模型参数，该指数作为数字乳腺摄影基于任务的质量控制（QC）指标。对一个简单的测试体模进行成像，以测量模型参数，即噪声功率谱、调制传递函数和测试对象对比度。然后将这些参数用于一个非白化观察者模型，该模型包含一个眼滤波器和内部噪声，以预测dʹ。在一项四选一强制选择读者研究中，通过测量圆盘的dʹ对模型进行调整。对于每个圆盘直径，dʹ用于估计可探测性的阈值厚度。使用不同的探测器技术和X射线光谱，获得了六种数字乳腺摄影系统的数据。dʹ的测量值与模型值之间存在很强的相关性，皮尔逊相关系数为0.96。对测试体模不同图像的重复测量表明，不同系统dʹ的平均变异系数在0.07至0.10之间。阈值厚度的标准差在0.001至0.017毫米之间。该模型具有鲁棒性，结果相对独立于系统，这表明观察者模型dʹ有望作为数字乳腺摄影的跨平台QC指标。
