Chen Lingling, McGinty James, Taylor Harriet B, Bugeon Laurence, Lamb Jonathan R, Dallman Margaret J, French Paul M W
Photonics Group, Department of Physics, Imperial College London, SW7 2AZ, UK.
Opt Express. 2012 Mar 26;20(7):7323-37. doi: 10.1364/OE.20.007323.
We demonstrate two techniques to improve the quality of reconstructed optical projection tomography (OPT) images using the modulation transfer function (MTF) as a function of defocus experimentally determined from tilted knife-edge measurements. The first employs a 2-D binary filter based on the MTF frequency cut-off as an additional filter during back-projection reconstruction that restricts the high frequency information to the region around the focal plane and progressively decreases the spatial frequency bandwidth with defocus. This helps to suppress "streak" artifacts in OPT data acquired at reduced angular sampling, thereby facilitating faster OPT acquisitions. This method is shown to reduce the average background by approximately 72% for an NA of 0.09 and by approximately 38% for an NA of 0.07 compared to standard filtered back-projection. As a biological illustration, a Fli:GFP transgenic zebrafish embryo (3 days post-fertilisation) was imaged to demonstrate the improved imaging speed (a quarter of the acquisition time). The second method uses the MTF to produce an appropriate deconvolution filter that can be used to correct for the spatial frequency modulation applied by the imaging system.
我们展示了两种技术，以利用调制传递函数（MTF）来提高重建光学投影断层扫描（OPT）图像的质量，该MTF是通过倾斜刀口测量实验确定的散焦函数。第一种方法是在反投影重建过程中，采用基于MTF频率截止的二维二进制滤波器作为附加滤波器，将高频信息限制在焦平面周围区域，并随着散焦逐渐减小空间频率带宽。这有助于抑制在减少角度采样下获取的OPT数据中的“条纹”伪影，从而加快OPT采集速度。与标准滤波反投影相比，该方法在数值孔径为0.09时可将平均背景降低约72%，在数值孔径为0.0７时可降低约38%。作为生物学示例，对一个Fli:GFP转基因斑马鱼胚胎（受精后3天）进行成像，以展示提高的成像速度（采集时间缩短为四分之一）。第二种方法使用MTF来生成合适的去卷积滤波器，该滤波器可用于校正成像系统施加的空间频率调制。
