arXiv subjects

Ashvin Thambyah

Publications and source records attributed to Ashvin Thambyah.

5 recordsLinked to original sources

arXiv2025

Density-encoded line integral convolution: polarisation optical axis tractography using centroidal Voronoi tessellation

Visualising complex polarimetry optical axis fields is challenging. We introduce density-encoded line integral convolution (DELIC), a novel approach that builds on the classic line integral convolution algorithm by incorporating the principles of centroidal Voronoi tessellation, enabling clearer and more interpretable representations of complex optical axis fields.

physics.optics↗

arXiv2025

Depth-resolved polarisation sensitive optical coherence tomography reveals the complex microanatomical response of cartilage to compression

Conventional methods for analysing cartilage microstructure under mechanical loading are largely destructive. In this work, we evaluate the efficacy of using depth-resolved polarisation sensitive optical coherence tomography (PS-OCT) to study the cartilage morphological response to compression. We show that depth-resolved PS-OCT reveals the microstructure of cartilage under load, and it can do so non-destructively, opening significant possibilities for enhanced clinical assessment of cartilage health by detecting deviance from normal load-bearing behaviour.

physics.optics↗

arXiv2021

Detection of subtle cartilage and bone tissue degeneration in the equine joint using polarisation-sensitive optical coherence tomography

Objective: To explore the ability of polarisation-sensitive optical coherence tomography (PS-OCT) to rapidly identify subtle signs of tissue degeneration in the equine joint. Design: Polarisation-sensitive optical coherence tomography (PS-OCT) images were systematically acquired in four locations along the medial and lateral condyles of the third metacarpal bone in 5 equine specimens. Intensity and retardation PS-OCT images, and anomalies observed therein, were then compared and validated with high resolution images of the tissue sections obtained using Differential Interference contrast (DIC) optical light microscopy. Results: The PS-OCT system was capable of imaging the entire equine osteochondral unit, and allowed delineation of the three structurally differentiated zones of the joint, that is, the articular cartilage matrix, zone of calcified cartilage and underlying subchondral bone. Importantly, PS-OCT imaging was able to detect underlying matrix and bone changes not visible without dissection and/or microscopy. Conclusion: PS-OCT has substantial potential to detect, non-invasively, sub-surface microstructural changes that are known to be associated with the early stages of joint tissue degeneration.

physics.med-ph↗

arXiv2020

Impact-Induced Cartilage Damage Assessed using Polarisation-Sensitive Optical Coherence Tomography

Significance: Non-invasive determination of structural changes in articular cartilage immediately after impact and rehydration provides insight into the response and recovery of the soft tissue, as well as provides a potential methodology for clinicians to quantify early degenerative changes. Approach: A custom-designed impact testing rig was used to deliver 0.9 J and 1.4 J impact energies to bovine articular cartilage. A total of 55 (n=28 healthy, n=27 mildly degenerate) cartilage-on-bone samples were imaged before, immediately after, and 3 hours after impact. PS-OCT images were analysed to assess changes relating to surface irregularity, optical attenuation, and birefringence. Results: Mildly degenerate cartilage exhibits a significant change in birefringence following 1.4 J impact energies compared to healthy samples which is believed to be attributable to degenerate cartilage being unable to fully utilise the fluid phase to distribute and dampen the energy. After rehydration, the polarisation-sensitive images appear to `optically-recover' reducing the reliability of birefringence as an absolute metric. Surface irregularity and optical attenuation encode diagnostically relevant information and may serve as markers to predict the mechanical response of articular cartilage.

physics.med-ph↗

arXiv2018

Quantifying birefringence in the bovine model of early osteoarthritis using polarisation-sensitive optical coherence tomography and mechanical indentation

Recent studies have shown potential for using polarisation sensitive optical coherence tomography (PS-OCT) to study cartilage morphology, and to be potentially used as an in-vivo, non-invasive tool for detecting osteoarthritic changes. However, there has been relatively limited ability of this method to quantify the subtle changes that occur in the early stages of cartilage degeneration. An established mechanical indenting technique that has previously been used to examine the microstructural response of articular cartilage was employed to fix the bovine samples in an indented state. The samples were subject to creep loading with a constant compressive stress of 4.5 MPa and, when imaged using PS-OCT, enabled birefringent banding patterns to be observed. The magnitude of the birefringence was quantified using the birefringence coefficient (BRC) and statistical analysis revealed that PS-OCT is able to detect and quantify significant changes between healthy and early osteoarthritic cartilage (p<0.001). This presents a novel utilization of PS-OCT for future development as an in-vivo assessment tool.

physics.med-ph↗