###### Abstract  
Optical coherence tomography-based angiography (OCTA) has attracted attention in clinical applications as a non-invasive and high-resolution imaging modality. Motion artifacts are the most seen artifact in OCTA. Eigen-decomposition (ED) algorithms are popular choices for OCTA reconstruction, but have limitations in the reduction of motion artifacts. The OCTA data do not meet one of the requirements of ED, which is that the data should be normally distributed. To overcome this drawback, we propose an easy-to-deploy development of ED, windowed-ED (wED). wED applies a moving window to the input data, which can contrast the blood-flow signals with significantly reduced motion artifacts. To evaluate our wED algorithm, pre-acquired dorsal wound healing data in a murine model were used. The ideal window size was optimized by fitting the data distribution with the normal distribution. Lastly, the cross-sectional and en face results were compared among several OCTA reconstruction algorithms, Speckle Variance, A-scan ED (aED), B-scan ED, and wED. wED could reduce the background noise intensity by 18% and improve PSNR by 4.6%, compared to the second best-performed algorithm, aED. This study can serve as a guide for utilizing wED to reconstruct OCTA images with an optimized window size. optical coherence tomography (OCT); optical coherence tomography-based angiography (OCTA); eigen-decomposition (ED); motion artifact +
Footnote †: journal: Applied Sciences  
(CDV) [10] and eigen-decomposition (ED) [11; 12], utilize both intensity and phase changes within acquired data to reconstruct blood vessel signals. With these blood flow reconstruction techniques, among which ED has been a popular choice [4], OCTA can provide high-resolution 3D micro-vessel networks. However, these reconstruction techniques have less capacity to reduce motion artifacts on OCTA signals. Motion artifacts are the most seen artifact in OCTA [13], caused by the device vibration or scanning objects' movements. In recent in vivo studies [14; 15; 16; 17; 18], motion artifacts were often reported. The image quality of OCTA imaging can be affected dramatically by a motion artifact [19]. During the OCTA reconstruction, the algorithms can easily mistake motion effects for blood flow signals. Moreover, the OCTA's scanning protocols utilize repeated scanning at the same position to extract blood flow signals from static tissues. A longer acquisition time (OCTA takes around 2-16 times OCT's acquisition time [12]) would have higher chances to include motion effects. As a result of artifacts, OCTA-derived metrics, such as vessel density, can be impacted and can potentially be invalided [20; 21; 22; 23; 24]. In order to reduce motion artifacts, some adjustments or improvements to the experiment hardware can be introduced. For example, the scanning objects were physically stabilized by using a bite bar or mount [16; 17]. Although physical fixation can reduce motion artifacts, there are several downsides. It is not always an ideal solution for clinical studies due to the availability of the mounts and the potential introduction of discomfort in human or animal participants. In addition, the contact between the fixations and the scanning object can cause pressure on the scanned area, which can reduce or change the blood flow signals. The improvement in the OCTA scanning systems also has the potential to reduce motion artifacts. One straightforward solution is to reduce the scanning time by using a high-speed camera or using a Swept-Source OCT (SSOCT) instead of a Spectral-Domain OCT (SDOCT), which can provide a higher acquisition rate [25]. More advanced scanning mirrors can also improve scanning stability and speed. However, the solutions above can also greatly increase the cost of the system [26].