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Level Set Methods in Segmentation of SDOCT Retinal Images
Published in Ayman El-Baz, Jasjit S. Suri, Level Set Method in Medical Imaging Segmentation, 2019
N Padmasini, R Umamaheswari, Yacin Sikkandar Mohamed, Manavi D Sindal
As shown in Figure 5.2, the retina is a ten layered structure, viz., Nerve fiber layer (NFL), Ganglion cell layer (GCL), Inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), External limiting membrane (ELM), Ellipsoid zone (previously referred to as the IS/OS junction), Interdigitation zone, and Retinal pigment epithelium (RPE). Automatic detection of diabetic maculopathy from SDOCT retinal images is extremely important in analyzing the stage of diabetic retinopathy. Diabetic maculopathy is the condition of fluid being accumulated in between the retinal layers. As shown in Figure 5.3, SDOCT images provide more details about the intraretinal fluid and subretinal fluid present in the macula scan images.
Recent advances in imaging technologies for assessment of retinal diseases
Published in Expert Review of Medical Devices, 2020
Taha Soomro, Neil Shah, Magdalena Niestrata-Ortiz, Timothy Yap, Eduardo M. Normando, M. Francesca Cordeiro
Swept-source OCT (SS-OCT) provides a different method for generating OCT images. A laser sweeps across a range of wavelengths. The interference pattern created from the reference and the sample arm can be recorded in almost real-time by a photodiode [79]. Therefore, SS-OCT technology enables the fastest scanning speeds with greater than 100 000 A scans per second. SS-OCT uses longer wavelengths of light, with superluminescent diodes at 800–870nm [79]. With longer wavelengths used there is less signal strength decay (i.e. less sensitivity roll-off) versus depth which results in larger imaging ranges, allowing imaging of the vitreous, retina, and choroid concurrently. So there can be enhanced imaging of the deep layers without reducing the resolution of the anterior structures, making it optimal for examination of the deeper layers of the choroid and sclera [79,80,83]. It also has better penetration through media opacities [83,84]. It has been shown to be superior to SD-OCT in imaging the posterior sclera [85], choroid, and important layers of the retina (inner segment (IS)/outer segment (OS) line, and external limiting membrane (ELM)) [86]. This includes a better visualization of the choroidoscleral interface, which is necessary to get a reliable measure of choroidal thickness [83,87,88].