Shankar A, Russ M, Vijayan S, Bednarek D R, Rudin S
Toshiba Stroke and Vascular Research Center, University at Buffalo, SUNY.
Proc SPIE Int Soc Opt Eng. 2017 Feb 11;10132. doi: 10.1117/12.2254402. Epub 2017 Mar 9.
Apodized Aperture Pixel (AAP) design, proposed by Ismailova et. al, is an alternative to the conventional pixel design. The advantages of AAP processing with a sinc filter in comparison with using other filters include non-degradation of MTF values and elimination of signal and noise aliasing, resulting in an increased performance at higher frequencies, approaching the Nyquist frequency. If high resolution small field-of-view (FOV) detectors with small pixels used during critical stages of Endovascular Image Guided Interventions (EIGIs) could also be extended to cover a full field-of-view typical of flat panel detectors (FPDs) and made to have larger effective pixels, then methods must be used to preserve the MTF over the frequency range up to the Nyquist frequency of the FPD while minimizing aliasing. In this work, we convolve the experimentally measured MTFs of an Microangiographic Fluoroscope (MAF) detector, (the MAF-CCD with 35μm pixels) and a High Resolution Fluoroscope (HRF) detector (HRF-CMOS50 with 49.5μm pixels) with the AAP filter and show the superiority of the results compared to MTFs resulting from moving average pixel binning and to the MTF of a standard FPD. The effect of using AAP is also shown in the spatial domain, when used to image an infinitely small point object. For detectors in neurovascular interventions, where high resolution is the priority during critical parts of the intervention, but full FOV with larger pixels are needed during less critical parts, AAP design provides an alternative to simple pixel binning while effectively eliminating signal and noise aliasing yet allowing the small FOV high resolution imaging to be maintained during critical parts of the EIGI.
伊斯梅洛娃等人提出的变迹孔径像素（AAP）设计是传统像素设计的一种替代方案。与使用其他滤波器相比，采用 sinc 滤波器进行 AAP 处理的优势包括调制传递函数（MTF）值不退化以及消除信号和噪声混叠，从而在更高频率下提高性能，接近奈奎斯特频率。如果在血管内图像引导介入（EIGI）的关键阶段使用的具有小像素的高分辨率小视野（FOV）探测器也能够扩展以覆盖平板探测器（FPD）典型的全视野，并使其具有更大的有效像素，那么必须采用方法在高达 FPD 奈奎斯特频率的频率范围内保持 MTF，同时尽量减少混叠。在这项工作中，我们将微血管造影荧光镜（MAF）探测器（像素为 35μm 的 MAF - CCD）和高分辨率荧光镜（HRF）探测器（像素为 49.5μm 的 HRF - CMOS50）的实验测量 MTF 与 AAP 滤波器进行卷积，并展示结果相对于移动平均像素合并产生的 MTF 和标准 FPD 的 MTF 的优越性。当用于对无限小的点物体成像时，AAP 的效果在空间域中也得到了体现。对于神经血管介入中的探测器，在介入的关键部分高分辨率是首要任务，但在不太关键的部分需要全视野和更大像素，AAP 设计提供了一种替代简单像素合并的方法，同时有效消除信号和噪声混叠，并且在 EIGI 的关键部分能够保持小视野高分辨率成像。
