Browsing by Author "Batista, Ana"
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- Normative mice retinal thickness: 16-month longitudinal characterization of wild-type mice and changes in a model of Alzheimer's diseasePublication . Batista, Ana; Guimarães, Pedro; Martins, João; Moreira, Paula I.; Ambrósio, António F.; Castelo-Branco, Miguel; Serranho, Pedro; Bernardes, RuiAnimal models of disease are paramount to understand retinal development, the pathophysiology of eye diseases, and to study neurodegeneration using optical coherence tomography (OCT) data. In this study, we present a comprehensive normative database of retinal thickness in C57BL6/129S mice using spectral-domain OCT data. The database covers a longitudinal period of 16 months, from 1 to 16 months of age, and provides valuable insights into retinal development and changes over time. Our findings reveal that total retinal thickness decreases with age, while the thickness of individual retinal layers and layer aggregates changes in different ways. For example, the outer plexiform layer (OPL), photoreceptor inner segments (ILS), and retinal pigment epithelium (RPE) thickened over time, whereas other retinal layers and layer aggregates became thinner. Additionally, we compare the retinal thickness of wild-type (WT) mice with an animal model of Alzheimer's disease (3×Tg-AD) and show that the transgenic mice exhibit a decrease in total retinal thickness compared to age-matched WT mice, with statistically significant differences observed at all evaluated ages. This normative database of retinal thickness in mice will serve as a reference for future studies on retinal changes in neurodegenerative and eye diseases and will further our understanding of the pathophysiology of these conditions.
- On the numerical solution of the inverse elastography problem for time-harmonic excitationPublication . Serranho, Pedro; Barbeiro, Sílvia; Henriques, Rafael; Batista, Ana; Santos, Mário; Correia, Carlos; Domingues, José Paulo; Loureiro, Custódio; Cardoso, João M. R.; Bernardes, Rui; Morgado, António MiguelIn this paper we address the numerical solution of the inverse elastography problem, from the knowledge of the excitation field on the boundary and the displacement field in a grid of points within the domain. We suggest using a representation of the solution by the method of fundamental solutions and using a Newtontype method to iteratively approximate the Lam´e coefficients of the medium from elastography displacement measurements. We consider a toy model to illustrate the performance of the method.
- Phase-resolved optical coherence elastography: an insight into tissue displacement estimationPublication . Batista, Ana; Serranho, Pedro; Santos, Mário; Correia, Carlos; Domingues, José P.; Loureiro, Custódio; Cardoso, João; Barbeiro, Sílvia; Morgado, António Miguel; Bernardes, RuiRobust 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.
- Retinal imaging in animal models: searching for biomarkers of neurodegenerationPublication . Batista, Ana; Guimarães, Pedro; Serranho, Pedro; Nunes, Ana; Martins, João; Moreira, Paula I.; Ambrósio, António F.; Morgado, Miguel; Castelo-Branco, Miguel; Bernardes, RuiThere 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.
- Swept-source phase-stabilized optical coherence tomography setup for elastographyPublication . Batista, Ana; Correia, Carlos; Barbeiro, Sílvia; Cardoso, João; Domingues, José Paulo; Henriques, Rafael; Loureiro, Custódio; Santos, Mário; Serranho, Pedro; Bernardes, Rui; Morgado, António MiguelWe present an Optical Coherence Elastography (OCE) system, based on a swept-source Optical Coherence Tomography (OCT) setup, and evaluate its performance in terms of phase stability and minimum detectable displacement. The ability to record sub-pixel movements in samples under dynamic conditions was also assessed. The OCE system has a time stability of 396.9 ± 46.7 ps. The phase stability, given by the standard deviation of the measured phase difference, was 72.44 mrad, which corresponds to a minimum detectable displacement of 6.11 nm. Tests showed that the OCE system can detect and measure sub-pixel movements in samples under dynamic mechanical excitation.
- Time-dependent elastic numerical model for Optical Coherence Elastography of the murine retinaPublication . Correia, Carlos; Batista, Ana; Barbeiro, Sílvia; Cardoso, João; Domingues, José Paulo; Henriques, Rafael; Loureiro, Custódio; Santos, Mário J.; Serranho, Pedro; Bernardes, Rui; Morgado, MiguelWe present the initial stages of development of a Finite Element Method-based time-dependent elastic numerical model which seeks to support the employment of our Optical Coherence Elastography system for assessing murine retinal elasticity. The current model is able to reconstruct displacement maps in both homogeneous and heterogeneous domains with errors up to a few hundredths relatively to a known exact displacement map, within 1 millisecond. The results demonstrate the robustness of the numerical algorithm under different elastic domains, and model parametrization with real Optical Coherence Elastography data is already in progress.