Chen Baiyu, Yu Lifeng, Leng Shuai, Kofler James, Favazza Christopher, Vrieze Thomas, McCollough Cynthia
Department of Radiology, Mayo Clinic, Rochester, MN 55905.
Proc SPIE Int Soc Opt Eng. 2016 Feb 27;9783. doi: 10.1117/12.2216962. Epub 2016 Mar 30.
The use of Fourier domain model observer is challenged by iterative reconstruction (IR), because IR algorithms are nonlinear and IR images have noise texture different from that of FBP. A modified Fourier domain model observer, which incorporates nonlinear noise and resolution properties, has been proposed for IR and needs to be validated with human detection performance. On the other hand, the spatial domain model observer is theoretically applicable to IR, but more computationally intensive than the Fourier domain method. The purpose of this study is to compare the modified Fourier domain model observer to the spatial domain model observer with both FBP and IR images, using human detection performance as the gold standard. A phantom with inserts of various low contrast levels and sizes was repeatedly scanned 100 times on a third-generation, dual-source CT scanner at 5 dose levels and reconstructed using FBP and IR algorithms. The human detection performance of the inserts was measured via a 2-alternative-forced-choice (2AFC) test. In addition, two model observer performances were calculated, including a Fourier domain non-prewhitening model observer and a spatial domain channelized Hotelling observer. The performance of these two mode observers was compared in terms of how well they correlated with human observer performance. Our results demonstrated that the spatial domain model observer correlated well with human observers across various dose levels, object contrast levels, and object sizes. The Fourier domain observer correlated well with human observers using FBP images, but overestimated the detection performance using IR images.
傅里叶域模型观察者的应用受到迭代重建（IR）的挑战，因为IR算法是非线性的，且IR图像具有与滤波反投影（FBP）不同的噪声纹理。已提出一种结合非线性噪声和分辨率特性的改进傅里叶域模型观察者用于IR，且需要通过人体检测性能进行验证。另一方面，空间域模型观察者理论上适用于IR，但比傅里叶域方法计算量更大。本研究的目的是使用人体检测性能作为金标准，将改进的傅里叶域模型观察者与空间域模型观察者在FBP和IR图像上进行比较。在第三代双源CT扫描仪上，对具有各种低对比度水平和尺寸插入物的模体在5个剂量水平下重复扫描100次，并使用FBP和IR算法进行重建。通过二选一强制选择（2AFC）测试测量插入物的人体检测性能。此外，计算了两种模型观察者的性能，包括傅里叶域非预白化模型观察者和空间域通道化霍特林观察者。根据这两种模型观察者与人体观察者性能的相关程度对其性能进行比较。我们的结果表明，空间域模型观察者在各种剂量水平、物体对比度水平和物体尺寸下与人体观察者相关性良好。傅里叶域观察者使用FBP图像时与人体观察者相关性良好，但使用IR图像时高估了检测性能。
