Automated Quantitation of Choroidal Neovascularization: A Comparison Study Between Spectral-Domain and Swept-Source OCT Angiograms

Abstract

PurposeTo compare the lesion sizes of choroidal neovascularization (CNV) imaged with spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) and measured using an automated detection algorithm.MethodsPatients diagnosed with CNV were imaged by SD-OCTA and SS-OCTA systems using 3 × 3-mm and 6 × 6-mm scans. The complex optical microangiography (OMAGC) algorithm was used to generate the OCTA images. Optical coherence tomography A datasets for imaging CNV were derived by segmenting from the outer retina to 8 μm below Bruch's membrane. An artifact removal algorithm was used to generate angiograms free of retinal vessel projection artifacts. An automated detection algorithm was developed to quantify the size of the CNV. Automated measurements were compared with manual measurements. Measurements from SD-OCTA and SS-OCTA instruments were compared as well.ResultsTwenty-seven eyes from 23 subjects diagnosed with CNV were analyzed. No significant differences were detected between manual and automatic measurements: SD-OCTA 3 × 3-mm (P = 0.61, paired t-test) and 6 × 6-mm (P = 0.09, paired t-test) scans and the SS-OCTA 3 × 3-mm (P = 0.41, paired t-test) and 6 × 6-mm (P = 0.16, paired t-test) scans. Bland-Altman analyses were performed to confirm the agreement between automatic and manual measurements. Mean lesion sizes were significantly larger for the SS-OCTA images compared with the SD-OCTA images: 3 × 3-mm scans (P = 0.011, paired sample t-test) and the 6 × 6-mm scans (P = 0.021, paired t-test).ConclusionsThe automated algorithm measurements of CNV were in agreement with the hand-drawn measurements. On average, automated SS-OCTA measurements were larger than SD-OCTA measurements and consistent with the results from using hand-drawn measurements.

Comparison of SD-Optical Coherence Tomography Angiography and Indocyanine Green Angiography in Type 1 and 2 Neovascular Age-related Macular Degeneration

“…Previous studies have reported statistically significantly larger CNV demarcation areas for different SS-OCTA than for commercially available SD-OCTA systems. 33,34 Further, an evaluation algorithm (e.g., variable interscan time analysis) as described by Choi et al, allows the interscan time to be increased from 1.5 to 3 ms, which decreases the limits for the lowest detectable and fastest distinguishable flow and consequently reveals microvascular structures previously not seen. 35 However, these OCTA systems are not yet commercially available.…”

“…Analyses of various SS-OCTA prototypes have already shown their superior ability regarding CNV detection compared with SD-OCTA. 33,34,36 Certain areas of the CNV lesion may not be detectable in SD-OCTA because of very slow or fast blood flow. This is not the case in ICGA, as the dye will eventually stain the whole CNV lesion during the 30 minutes of examination, independent of blood flow velocity.…”

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

“…SD-OCT typically uses an 800 to 900-nm wavelength source, and its scan speed ranges from 40 to 100-kHz. SD-OCT has increased sensitivity roll-off with depth as compared to SS-OCT (Miller, Roisman et al 2017, Zhang, Chen et al 2017). Also, shorter wavelengths are more prone to scattering and attenuation; thus, they penetrate into tissue less than the longer wavelengths used in the SS-OCT devices.…”

Quantification of Macular Microvascular Changes in Patients With Retinitis Pigmentosa Using Optical Coherence Tomography Angiography

“…We used SD-OCTA systems operating at 840 nm even though light at this wavelength is greatly scattered and absorbed by the RPE complex, which can affect the ability to examine the choriocapillaris vessels. 15,16 We did not analyze the choriocapillaris vessels in this study. In addition, the clarity of the images of the choroidal vascular layer was dependent on the status of the RPE, which was affected by the stage of RP.…”