Abstract
We characterized image quality in optical coherence angiography (OCA) en face planes of mouse cortical capillary network in terms of signal-to-noise ratio (SNR) and Weber contrast (Wc) through a novel mask-based segmentation method. The method was used to compare two adjacent B-scan processing algorithms, (1) average absolute difference (AAD) and (2) standard deviation (SD), while varying the number of lateral cross-sections acquired (also known as the gate length, N). AAD and SD are identical at N = 2 and exhibited similar image quality for N<10. However, AAD is relatively less susceptible to bulk tissue motion artifact than SD. SNR and Wc were 15% and 35% higher for AAD from N = 25 to 100. In addition data sets were acquired with two objective lenses with different magnifications to quantify the effect of lateral resolution on fine capillary detection. The lower power objective yielded a significant mean broadening of 17% in Full Width Half Maximum (FWHM) diameter. These results may guide study and device designs for OCA capillary and blood flow quantification.
Highlights
Optical coherence tomography (OCT) is a high resolution imaging modality capable of capturing volumetric data sets of highly scattering biological tissue
We imaged with a 5 × objective (ThorLabs Inc, LSM03), which is often used in angiography for the reasons stated above [7, 9, 12]
For average absolute difference (AAD) a pronounced increase takes place for 5 × and 10 × lenses up to N = 10 (16% signal-to-noise ratio (SNR) increase and 35% contrast increase for N = 10 with respect to N = 2)
Summary
Optical coherence tomography (OCT) is a high resolution imaging modality capable of capturing volumetric data sets of highly scattering biological tissue. In the last decade an imaging technique called speckle variance optical coherence angiography (SV-OCA) was developed to detect microvasculature and blood flow in biological tissue. Understanding morphological and dynamic changes in capillaries is essential to the study of diseases and pathological conditions. Ocular diseases such as diabetic retinopathy and agerelated macular degeneration impact the morphology of vessels and the formation of capillary networks, and are often accompanied by abnormal blood flow. The tight correlation between cerebral blood perfusion and brain metabolism allows for the treatment and diagnosis of neural vascular diseases. In our recent study we demonstrated that OCA is able to characterize the tissue response from neuroprosthetic electrode insertion in mouse motor cortex [9]
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