High performance OCTA enabled by combining features of shape, intensity, and complex decorrelation

Abstract

Motion contrast optical coherence tomography angiography (OCTA) entails a precise identification of dynamic flow signals from the static background, but an intermediate region with voxels exhibiting a mixed distribution of dynamic and static scatterers is almost inevitable in practice, which degrades the vascular contrast and connectivity. In this work, the static-dynamic intermediate region was pre-defined according to the asymptotic relation between inverse signal-to-noise ratio (iSNR) and decorrelation, which was theoretically derived for signals with different flow rates based on a multi-variate time series (MVTS) model. Then the ambiguous voxels in the intermediate region were further differentiated using a shape mask with adaptive threshold. Finally, an improved OCTA classifier was built by combining shape, iSNR, and decorrelation features, termed as SID-OCTA, and the performance of the proposed SID-OCTA was validated experimentally through mouse retinal imaging.

Endoscopic optical coherence tomography angiography using inverse SNR-amplitude decorrelation features and electrothermal micro-electro-mechanical system raster scan

“…Furthermore, in our study, the simulated results agree well with the theoretical calculation, which differed from the variance analysis based on Cramer-Rao lower bound (CRLB), where the variance is not accurate and serious outliers appear in the case of a practical and limited kernel size (52). In addition, by taking the advantage of accurate derivation, there is potential to further enhance the classification accuracy by dividing the IDa space more precisely and combining additional features (49). Although the IDa-OCTA algorithm was demonstrated with the ET MEMS in this study, it does not rely on a specific scanner, and can be readily used along with other scanning modalities (6,(17)(18)(19)(21)(22)(23)(24)(25)(26)(27).…”

“…However, the kernel size is limited in practice, and with the decrease of kernel size, the distribution variance and overlapping region of signals in IDa space increase accordingly (refer to Figure 2), which limits the ability to extract flow signals in the low-SNR regions. Using the knowledge of the exact IDa distribution, the noisy blood flow signals can be further enhanced by combining the tube shape feature of the vessels as reported by Li et al (49). The saturation limit of amplitude decorrelation was compressed to approximately 0.22, which is 1 in complex decorrelation (a decrease of 78%), and most likely due to the loss of the ultra-motion-sensitive phase information, (50).…”

Intraoperative optical coherence tomography angiography for intraocular surgery

“…The cornea was kept moist with a balanced salt solution to obtain good-quality images. We used the OCTA algorithm based on the inverse signal-to-noise ratio and decorrelation to achieve three-dimensional blood perfusion imaging [23][24][25].…”

Dual-beam delay-encoded all fiber Doppler optical coherence tomography for in vivo measurement of retinal blood flow

“…Optical coherence tomography (OCT) [4,5] , a technology offering high-resolution cross-sectional imaging of microstructures in biological tissues, has been widely used in clinical medicine [6][7][8][9] . In addition to morphological images, the functional OCT technology, such as OCT angiography [10,11] and Doppler OCT (DOCT) [12][13][14][15] , has been proposed to calculate the retinal vessel information.…”