Relationship between rheological properties and transverse relaxation time (T2) of artificial and porcine vitreous humour

Thakur, Sachin; Pan, Xingzheng; Kumarasinghe, Gamith L.; Yin, Naibo; Pontré, Beau; Vaghefi, Ehsan; Rupenthal, Ilva D.

doi:10.1016/j.exer.2020.108006

Cited by 5 publications

(6 citation statements)

References 32 publications

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“…Ideally, the mechanical properties of the intact vitreous humor should be tested in vivo. Non-invasive techniques used to study the material properties of the vitreous include MRI, 12,19,30,36,42 light scattering, 35,45 microbubble-based acoustic radiation force 28 , ultrasound, 29,39,47 and Brillouin spectroscopy. 160 With the advantageous ability of nondestructive in vivo vitreous assessment, the disadvantage of these methods is that they do not provide data (storage modulus and loss modulus) that are comparable to the current rheological data on the vitreous humor or reported experimental hydrogel vitreous substitutes.…”

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

“…Correlation between MRI-predicted values and the actual values measured using shear rheology still has room for improvement. 12 It should be noted that the T2 relaxation time measurements follow the local motion of water. Since the vitreous is composed of 99% water, T2 relaxation time has great potential to be utilized in future investigations to study the rates of diffusion in the vitreous.…”

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

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Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Tram

Maxwell

Swindle-Reilly

2020

Current Eye Research

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Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.

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Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Tram

Maxwell

Swindle-Reilly

2020

Current Eye Research

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“…23 Relaxation times are markers of tissue microstructure, viscosity, and composition. [24][25][26][27][28][29] Many metabolites are confined primarily to the intracellular space of specific cell types, for example, NAA to neurons, 23 or myo-inositol to astrocytes, 30 and their relaxation times specifically reflect the intracellular microenvironments of these cell types. Indeed, reports of altered metabolite relaxation times have been made in a wide range of neuropathologies, from multiple sclerosis 31 to brain tumors 32,33 and Alzheimer's disease.…”

Section: F I G U R Ementioning

confidence: 99%

Adaptive model‐based Magnetic Resonance

Beracha

Seginer

Tal

2023

Magnetic Resonance in Med

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Conventional sequences are static in nature, fixing measurement parameters in advance in anticipation of a wide range of expected tissue parameter values. We set out to design and benchmark a new, personalized approach-termed adaptive MR-in which incoming subject data is used to update and fine-tune the pulse sequence parameters in real time. Methods: We implemented an adaptive, real-time multi-echo (MTE) experiment for estimating T 2 s. Our approach combined a Bayesian framework with model-based reconstruction. It maintained and continuously updated a prior distribution of the desired tissue parameters, including T 2 , which was used to guide the selection of sequence parameters in real time. Results:Computer simulations predicted accelerations between 1.7-and 3.3-fold for adaptive multi-echo sequences relative to static ones. These predictions were corroborated in phantom experiments. In healthy volunteers, our adaptive framework accelerated the measurement of T 2 for n-acetyl-aspartate by a factor of 2.5. Conclusion:Adaptive pulse sequences that alter their excitations in real time could provide substantial reductions in acquisition times. Given the generality of our proposed framework, our results motivate further research into other adaptive model-based approaches to MRI and MRS.

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“…Magnetic resonance imaging (MRI) has also been employed not only to measure, but also to image the rheological properties of vitreous, both in porcine [ 14 ] and human eyes (post mortem) [ 15 ]. The so-called transverse relaxation time T2 is correlated to viscoelastic properties of the vitreous, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The great advantage of this approach is that it maps T2 and thus provides images which allows spatial variation of viscoelastic properties to be visualised. For example, the central vitreous has a slightly shorter T2 compared to the peripheral vitreous [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Determining vitreous viscosity using fluorescence recovery after photobleaching

et al. 2022

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Purpose Vitreous humor is a complex biofluid whose composition determines its structure and function. Vitreous viscosity will affect the delivery, distribution, and half-life of intraocular drugs, and key physiological molecules. The central pig vitreous is thought to closely match human vitreous viscosity. Diffusion is inversely related to viscosity, and diffusion is of fundamental importance for all biochemical reactions. Fluorescence Recovery After Photobleaching (FRAP) may provide a novel means of measuring intravitreal diffusion that could be applied to drugs and physiological macromolecules. It would also provide information about vitreous viscosity, which is relevant to drug elimination, and delivery. Methods Vitreous viscosity and intravitreal macromolecular diffusion of fluorescently labelled macromolecules were investigated in porcine eyes using fluorescence recovery after photobleaching (FRAP). Fluorescein isothiocyanate conjugated (FITC) dextrans and ficolls of varying molecular weights (MWs), and FITC-bovine serum albumin (BSA) were employed using FRAP bleach areas of different diameters. Results The mean (±standard deviation) viscosity of porcine vitreous using dextran, ficoll and BSA were 3.54 ± 1.40, 2.86 ± 1.13 and 4.54 ± 0.13 cP respectively, with an average of 3.65 ± 0.60 cP. Conclusions FRAP is a feasible and practical optical method to quantify the diffusion of macromolecules through vitreous.

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Relationship between rheological properties and transverse relaxation time (T2) of artificial and porcine vitreous humour

Cited by 5 publications

References 32 publications

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Adaptive model‐based Magnetic Resonance

Determining vitreous viscosity using fluorescence recovery after photobleaching

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