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- Characterization of the retinal changes of the 3×Tg-AD mouse model of Alzheimer’s diseasePublication . Ferreira, Hugo; Martins, João; Nunes, Ana; Moreira, Paula I.; Castelo-Branco, Miguel; Ambrósio, António F.; Serranho, Pedro; Bernardes, RuiAlzheimer’s disease (AD) is a progressive neurodegenerative disorder whose diagnosis remains a notable challenge. The literature suggests that cerebral changes precede AD symptoms by over two decades, implying a significantly advanced stage of AD by the time it is usually diagnosed. In the study herein, texture analysis was applied to computed optical coherence tomography ocular fundus images to identify differences between a group of the transgenic mouse model of the Alzheimer’s disease (3×Tg-AD) and a group of wild-type mice, at the ages of one and two-months-old. A substantial difference between groups was found at both time-points across all neuroretina’s layers. Here, the inner nuclear layer stands out both in the level of statistically significant differences and on the extension of these differences which span through the imaged area. Also, the progression of AD is suggested to be spotted by texture analysis as demonstrated by the significant difference found in the inner plexiform and the outer nuclear layers from the age of one to the age of two-months-old. These findings demonstrate the potential of the use of the retina and texture analysis to the diagnosis of AD and monitor AD progression. Besides, the differences between groups found in this study suggest that the 3×Tg-AD model may be inappropriate to study early changes associated with the AD and other animal models should be tested following the same path and rationale. Moreover, these results also suggest that the human genes present in these transgenic mice may have an impact on the neurodevelopment of offspring which would justify the significant changes found at the age of one-month-old.
- Texture analysis and Its applications in biomedical imaging: a surveyPublication . Khaksar Ghalati, Maryam; Nunes, Ana; Ferreira, Hugo; Serranho, Pedro; Bernardes, RuiTexture analysis describes a variety of image analysis techniques that quantify the variation in intensity and pattern. This paper provides an overview of several texture analysis approaches addressing the rationale supporting them, their advantages, drawbacks, and applications. This survey’s emphasis is in collecting and categorising over five decades of active research on texture analysis.Brief descriptions of different approaches are presented along with application examples. From a broad range of texture analysis applications, this survey’s final focus is on biomedical image analysis. An up-to-date list of biological tissues and organs in which disorders produce texture changes that may be used to spot disease onset and progression is provided. Finally, the role of texture analysis methods as biomarkers of disease is summarised.
- Sexual dimorphism of the adult human retina assessed by optical coherence tomographyPublication . Nunes, Ana; Serranho, Pedro; Quental, Hugo; Ambrósio, António F.; Castelo-Branco, Miguel; Bernardes, RuiSexual dimorphism in the human visual system is a well-established phenomenon, and recent research has unveiled possible connections between gonadal hormones and the retina status. In the literature, the findings are quite diverse and inconclusive results have been reported as well. In the study herein, texture analysis was applied to computed optical coherence tomography (OCT) fundus images to identify differences between female and male healthy adult controls at the six neuroretinal layers. Furthermore, younger and older groups were formed to assess differences across the adult lifespan. Besides local and global texture features, the thickness of each retinal layer at study was also analysed. The vast majority of the differences between female and male groups were found from the ganglion cell layer (GCL) to the outer plexiform layer (OPL), with the retinal nerve fibre layer (RNFL) layer being the least distinct one. For the sub-study by age, the younger group show similar results as those for the entire population, except for the RNFL. On the other hand, the older group presents minute differences between female and male subjects. These findings suggest that studies should be well balanced by sex, and particular care should be taken in the age span of the study groups. In the present study, we also demonstrate that texture and thickness are independent, for the most part, that thickness conveys the least information, and that texture is a strong candidate biomarker of eye and central nervous system status in health and disease.
- When sex matters: differences in the central nervous system as imaged by OCT through the retinaPublication . Nunes, Ana; Serranho, Pedro; Guimarães, Pedro; Ferreira, João; Castelo-Branco, Miguel; Bernardes, RuiBackground: Retinal texture has gained momentum as a source of biomarkers of neurodegeneration, as it is sensitive to subtle differences in the central nervous system from texture analysis of the neuroretina. Sex differences in the retina structure, as detected by layer thickness measurements from optical coherence tomography (OCT) data, have been discussed in the literature. However, the effect of sex on retinal interocular differences in healthy adults has been overlooked and remains largely unreported. Methods: We computed mean value fundus images for the neuroretina layers as imaged by OCT of healthy individuals. Texture metrics were obtained from these images to assess whether women and men have the same retina texture characteristics in both eyes. Texture features were tested for group mean differences between the right and left eye. Results: Corrected texture differences exist only in the female group. Conclusions: This work illustrates that the differences between the right and left eyes manifest differently in females and males. This further supports the need for tight control and minute analysis in studies where interocular asymmetry may be used as a disease biomarker, and the potential of texture analysis applied to OCT imaging to spot differences in the retina.
- The effect of menopause on the sexual dimorphism in the human retina: texture analysis of optical coherence tomography dataPublication . Nunes, Ana; Serranho, Pedro; Quental, Hugo; Castelo-Branco, Miguel; Bernardes, RuiSexual dimorphism in the human retina has recently been connected to gonadal hormones. In the study herein presented, texture analysis was applied to computed mean value fundus (MVF) images from optical coherence tomography data of female and male healthy adult controls. Two separate age-group analyses that excluded the probable perimenopause period of the women in the present study were performed, using a modified MVF image computation method that further highlights texture differences present in the retina. While distinct texture characteristics were found between premenopausal females and age-matched males, these differences almost disappeared in the older groups (postmenopausal women vs age-matched men), suggesting that sex-related texture differences in the retina can be correlated to the hormonal changes that women go through during the menopausal transition. These findings suggest that texture-based metrics may be used as biomarkers of physiology and pathophysiology of the retina and the central nervous system.