Fourier transform-second-harmonic generation imaging of collagen fibers in biological tissues

Rao, Raghu Ambekar Ramachandra; Mehta, Monal R.; Leithem, Scott; Toussaint, Kimani C.

doi:10.1364/biomed.2010.bsud63

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…Moreover, we decided to quantitatively assess the bands found in the high-pass filter map with the Fourier Transform because it fits adequately in the study of periodic patterns like this, and many studies applied it to analyze collagen structures from different tissues 21–24 . Nevertheless, there is no unique method to assess this kind of pattern 31,33,35 , and one of our following goals will be to compare Fourier methods with others, such as the Radon Transform, which is also capable of automatically detecting and quantifying the band patterns 39 .…”

Section: Discussionmentioning

confidence: 99%

“…Previously, the map that reveals these folds had only been submitted qualitatively but can be described quantitatively using the map itself and assessing it by means of the Fourier Transform (FT). This mathematical method has been applied to numerically evaluate several biological tissues featured by bands (as collagen structures) observed in other techniques 21,22 . Hence, due to the versatility of this imaging treatment, it should be applied to achieve the differences between healthy and keratoconic eyes and characterize the patterns obtained in those.…”

Section: Introductionmentioning

confidence: 99%

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Clinical applicability of the WaveFront Phase Imaging Sensor in the Keratoconus Disease

Belda-Para,

Velarde-Rodríguez,

Velasco-Ocaña

et al. 2023

Preprint

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SignificanceThe analysis of the wavefront phase of keratoconus eyes has become increasingly important due to its impact on the assessment of visual quality loss, irrecoverable with conventional optical treatments, and the understanding of morphological changes in corneal structures.AimThe aim of this work is to quantitatively assess the wavefront phase of keratoconic eyes measured by the novel high-resolution ocular aberrometer t·eyede (based on WaveFront Phase Imaging Sensor).ApproachThe measurements with this device were taken on healthy and keratoconic eyes at the Hospital Universitario Fundación Jiménez Díaz (Madrid, Spain). The wavefront phase recovered is post-processed and displayed in different phase maps, using exclusively the high-pass filter map for this study. From this map, the Root Mean Square, the Peak-to-Valley, and the amplitude value of the predominant obtained from its Fourier Transform are the parameters to distinguish between healthy and keratoconic eyes. Furthermore, the banding pattern observed in most keratoconic eyes is quantitatively analyzed by means of its period and orientation calculated from the Fourier Transform.ResultsThe Control group was composed of 43 healthy eyes, and the Pathological group presented 43 keratoconic eyes. Regarding the first three parameters used to compare both groups, there were significant statistical differences between them in all parameters, where the values obtained with the keratoconic group were higher than those of the healthy group. Although the values cannot be statistically comparable between stages, they tended to increase according to the severity of the disease. On the other hand, analyzing the banding pattern, the mean value of the period was approximately 50 µm, and most orientations were obliquus, tending to be horizontal rather than vertical.ConclusionsThe present study demonstrates that the objective analysis of the high frequencies detected by this wavefront sensor is a potential tool to reliably advise in the keratoconus diagnosis. Furthermore, combining this achievement with the quantitative assessment of the banding pattern would be used to objectively monitor the internal corneal status throughout the disease and its treatment optimization and surgery time.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Clinical applicability of the WaveFront Phase Imaging Sensor in the Keratoconus Disease

Belda-Para,

Velarde-Rodríguez,

Velasco-Ocaña

et al. 2023

Preprint

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Characterizing the Collagen Fiber Orientation in Pericardial Leaflets Under Mechanical Loading Conditions

et al. 2012

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When implanted inside the body, bioprosthetic heart valve leaflets experience a variety of cyclic mechanical stresses such as shear stress due to blood flow when the valve is open, flexural stress due to cyclic opening and closure of the valve, and tensile stress when the valve is closed. These types of stress lead to a variety of failure modes. In either a natural valve leaflet or a processed pericardial tissue leaflet, collagen fibers reinforce the tissue and provide structural integrity such that the very thin leaflet can stand enormous loads related to cyclic pressure changes. The mechanical response of the leaflet tissue greatly depends on collagen fiber concentration, characteristics, and orientation. Thus, understating the microstructure of pericardial tissue and its response to dynamic loading is crucial for the development of more durable heart valve, and computational models to predict heart valves’ behavior. In this work, we have characterized the 3D collagen fiber arrangement of bovine pericardial tissue leaflets in response to a variety of different loading conditions under Second-Harmonic Generation Microscopy. This real-time visualization method assists in better understanding of the effect of cyclic load on collagen fiber orientation in time and space.

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Load-dependent extracellular matrix organization in atrioventricular heart valves: differences and similarities

Alavi

Sinha

Steward

et al. 2015

American Journal of Physiology-Heart and Circulatory Physiology

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The extracellular matrix of the atrioventricular (AV) valves' leaflets has a key role in the ability of these valves to properly remodel in response to constantly varying physiological loads. While the loading on mitral and tricuspid valves is significantly different, no information is available on how collagen fibers change their orientation in response to these loads. This study delineates the effect of physiological loading on AV valves' leaflets microstructures using Second Harmonic Generation (SHG) microscopy. Fresh natural porcine tricuspid and mitral valves' leaflets (n = 12/valve type) were cut and prepared for the experiments. Histology and immunohistochemistry were performed to compare the microstructural differences between the valves. The specimens were imaged live during the relaxed, loading, and unloading phases using SHG microscopy. The images were analyzed with Fourier decomposition to mathematically seek changes in collagen fiber orientation. Despite the similarities in both AV valves as seen in the histology and immunohistochemistry data, the microstructural arrangement, especially the collagen fiber distribution and orientation in the stress-free condition, were found to be different. Uniaxial loading was dependent on the arrangement of the fibers in their relaxed mode, which led the fibers to reorient in-line with the load throughout the depth of the mitral leaflet but only to reorient in-line with the load in deeper layers of the tricuspid leaflet. Biaxial loading arranged the fibers in between the two principal axes of the stresses independently from their relaxed states. Unlike previous findings, this study concludes that the AV valves' three-dimensional extracellular fiber arrangement is significantly different in their stress-free and uniaxially loaded states; however, fiber rearrangement in response to the biaxial loading remains similar.

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Fourier transform-second-harmonic generation imaging of collagen fibers in biological tissues

Cited by 3 publications

References 9 publications

Clinical applicability of the WaveFront Phase Imaging Sensor in the Keratoconus Disease

Clinical applicability of the WaveFront Phase Imaging Sensor in the Keratoconus Disease

Characterizing the Collagen Fiber Orientation in Pericardial Leaflets Under Mechanical Loading Conditions

Load-dependent extracellular matrix organization in atrioventricular heart valves: differences and similarities

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