Comparison and Repeatability of High Resolution and High Speed Scans from Spectralis Optical Coherence Tomography Angiography

Abstract

The purpose of this study was to evaluate and compare the repeatability of optical coherence tomography angiography (OCTA) derived retinal vascular quantitative metrics using high resolution (HR) versus high speed (HS) acquisition modes. Methods: Macular 4.4 × 2.9-mm OCTA images from normal, healthy volunteers were captured using both HR (768 A-scans × 256 B-scans) and HS (384 A-scans × 256 B-scans) acquisition protocols. Vessel density and vessel length density of the superficial capillary plexus and deep capillary plexus, as well as choriocapillaris flow deficit were computed. In a subset of eyes, the OCTA scans were repeated twice 2 days later and the same metrics were recomputed to assess repeatability, using intraclass correlation coefficients and coefficient of variation (CV). Results: Comparison of measurements between HR and HS acquisitions in 41 healthy eyes showed statistically significant differences for all quantitative metrics (P < 0.01). However, no significant differences were observed among the three repeated scans (one on day 1 and two on day 3) obtained with each of the acquisition modes. The CVs ranged from 0.01 to 0.03 with the HR mode and 0.01 to 0.04 with the HS mode. The intraclass correlation coefficients (ICCs) among measurements were similar and high for both HR and HS modes, ranging from 0.844 to 0.949. Conclusions: HR and HS OCTA acquisition modes both yielded repeatable quantitative metrics for the retinal circulation and the choriocapillaris. However, despite a similar field, the HR and HS derived measurements differed significantly. Translational Relevance: To establish OCTA imaging in clinical and research practice, standardized and repeatability image analysis are necessary.

Optical Coherence Tomography Angiography of the Choriocapillaris in Age-Related Macular Degeneration

“…To mitigate these changes, several devices contain projection removal functions which remove the flow signal cast by overlying retinal vessels from the choriocapillaris slab. Many image processing strategies independent of the OCTA devices have also been adopted to eliminate these potentially confounding residual shadow or projection artifacts [ 9 , 24 , 25 , 26 , 27 , 28 ]. Motion artifacts created by body and eye movement and reduced signal strength of the images can also profoundly reduce the accuracy of quantitative analysis of the choriocapillaris [ 1 , 29 ].…”

“…The limitations of this method include the lack of a globally approved and validated normal database and the use of one standard deviation as a threshold, which is debated. Currently, the most commonly used approach is the Phansalkar local thresholding method [ 1 , 10 , 12 , 26 , 27 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. This method sets a circle with a certain “Phansalkar radius” around each pixel, and creates a threshold based off of the intensity mean and standard deviation inside the circle.…”

Retinal Microvasculopathy with Different Insulin Infusion Therapies in Children with Type 1 Diabetes Mellitus without Clinical Diabetic Retinopathy.

“…These results suggested that reduction in blood flow and impairment of the blood–retinal barrier have occurred because of chronic hyperglycemia before apparent signal of DR in children with T1DM. As a noninvasive and repeatable technique, 18 OCTA is an available technology to detect and closely follow-up the earlier microvascular changes of retina in children with T1DM without clinical DR. In future, VD of retina may be an important indicator to predict and monitor the T1DM DR in clinic.…”

Influence of protocol scan on choroidal vascularity measurements: a spectralis optical coherence tomography study

“…The authors found a moderate agreement between CVIs obtained from scans acquired using a different pupil entry position of the beam and suggested to always use the same direction of the beam to standardize CVI measurements [ 20 ]. Corvi et al, analyzed the repeatability of OCT angiography derived retinal quantitative metrics using HR versus HS acquisition modes, reporting statistically significant different values [ 21 ].…”