Optical Coherence Elastography for imaging retina mechanical properties

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Phase-resolved optical coherence elastography: an insight into tissue displacement estimation

Publication . Batista, Ana; Serranho, Pedro; Santos, Mário; Correia, Carlos; Domingues, José P.; Loureiro, Custódio; Cardoso, João; Barbeiro, Sílvia; Morgado, António Miguel; Bernardes, Rui

Robust methods to compute tissue displacements in optical coherence elastography (OCE) data are paramount, as they play a significant role in the accuracy of tissue elastic properties estimation. In this study, the accuracy of different phase estimators was evaluated on simulated OCE data, where the displacements can be accurately set, and on real data. Displacement (∆𝑑) estimates were computed from (i) the original interferogram data (Δ𝜑𝑜𝑟𝑖) and two phase-invariant mathematical manipulations of the interferogram: (ii) its first-order derivative (Δ𝜑𝑑) and (iii) its integral (Δ𝜑𝑖𝑛𝑡). We observed a dependence of the phase difference estimation accuracy on the initial depth location of the scatterer and the magnitude of the tissue displacement. However, by combining the three phase-difference estimates (Δ𝑑𝑎𝑣), the error in phase difference estimation could be minimized. By using Δ𝑑𝑎𝑣, the median root-mean-square error associated with displacement prediction in simulated OCE data was reduced by 85% and 70% in data with and without noise, respectively, in relation to the traditional estimate. Furthermore, a modest improvement in the minimum detectable displacement in real OCE data was also observed, particularly in data with low signal-to-noise ratios. The feasibility of using Δ𝑑𝑎𝑣 to estimate agarose phantoms’ Young’s modulus is illustrated.

2023Journal article

Open access

Retinal imaging in animal models: searching for biomarkers of neurodegeneration

Publication . Batista, Ana; Guimarães, Pedro; Serranho, Pedro; Nunes, Ana; Martins, João; Moreira, Paula I.; Ambrósio, António F.; Morgado, Miguel; Castelo-Branco, Miguel; Bernardes, Rui

There is a pressing need for novel diagnostic and progression biomarkers of neurodegeneration. However, the inability to determine disease duration and stage in patients with Alzheimer’s disease (AD) hinders their discovery. Because animal models of disease allow us to circumvent some of these limitations, they have proven to be of paramount importance in clinical research. Due to the clear optics of the eye, the retina combined with optical coherence tomography (OCT) offers the perfect opportunity to image neurodegeneration in the retina in vivo, non-invasively, directly, quickly, and inexpensively. Based on these premises, our group has worked towards uncovering neurodegeneration-associated changes in the retina of the triple-transgenic mouse model of familial AD (3×Tg-AD). In this work, we present an overview of our work on this topic. We report on thickness variations of the retina and retinal layers/layer aggregates caused by healthy aging and AD-like conditions and discuss the implications of focusing research efforts solely on retinal thickness. We explore what other information is embedded in the OCT data, extracted based on texture analysis and deep-learning approaches, to further identify biomarkers that could be used for early detection and diagnosis. We were able to detect changes in the retina of the animal model of AD as early as 1 month of age. We also discuss our work to develop an optical coherence elastography system to measure retinal elasticity, which can be used in conjunction with conventional OCT. Finally, we discuss the potential application of these technologies in human patients and the steps needed to make OCT a helpful screening tool for the detection of neurodegeneration.

2023Journal article

Open access