Depth-dependent refractive index of normal and early degenerated articular cartilage

Optical clearing is an effective method to reduce light scattering of biological tissues that provides significant enhancement of light penetration into the biological tissues making non-invasive diagnosis more feasible. In current report Optical Coherence Tomography (OCT) in conjunction with optical clearing is applied for assessment of deep cartilage layers and cartilage-bone interface. The solution of Iohexol in water has been used as an optical clearing agent. The cartilage-bone boundary becomes visible after 15 min of optical clearing that enabling non-invasive estimation of its roughness: Sa = 10 ± 1 µm. The results show that for 0.9 mm thick cartilage optical clearing is stopped after 50 min with an increase of refractive index from 1.386 ± 0.008 to 1.510 ± 0.009. Current approach enables more reliable detection of arthroscopically inaccessible regions, including cartilage-bone boundary and subchondral bone, and potentially improves accuracy of the osteoarthritis diagnosis.

show abstract

“…However, most of authors report only the average value of cartilage refractive index. The available data have high variation:

1.3975 \pm 0.0156

(λ = 561 nm)

1.4444 \pm 0.0363

(λ = 561 nm)

1.358 \pm 0.022

(λ = 1310 nm)

1.510 \pm 0.009

(λ = 1300 nm)

, explained among others by different light source, age, water content and physiological status of the sample.…”

Section: Resultsmentioning

confidence: 99%

“…It was found that before the optical clearing the refractive index value of cartilage averaged over four samples was

1.386 \pm 0.008

which is close to the values obtained in Refs. . Refractive index value measured for the same tissue samples after 100 min of optical clearing with iohexol solution was

1.504 \pm 0.016

.…”

Section: Resultsmentioning

confidence: 99%

Imaging of subchondral bone by optical coherence tomography upon optical clearing of articular cartilage

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Thickness is converted from optical path length by assuming an average refractive index n ¼ 1.444 in articular cartilage. 23 For sample S1, region R-1 is relatively thin with a thickness of ∼125 μm. Region R-2 is twice thicker than R-1, which is consistent with the anatomical knowledge about the thickness of superficial and transitional zones.…”

Section: Data Processing Of Slope-based Segmentationmentioning

confidence: 99%

Slope-based segmentation of articular cartilage using polarization-sensitive optical coherence tomography phase retardation image

Zhou

Huang

et al. 2019

J. Biomed. Opt.

View full text Add to dashboard Cite

A segmentation method based on phase retardation measurements from polarization-sensitive optical coherence tomography (PS-OCT) is developed to differentiate the structural zones of articular cartilage. The organization of collagen matrix in articular cartilage varies over the different structural zones, generating different tissue birefringence. Analyzing the slope of the accumulated phase retardation at different depths can detect the variation in tissue birefringence and be used to segment the structural zones. The method is validated on phantoms composed of layers of different materials. Articular cartilage samples from adult swine are segmented with the method. The characteristics in each segmented zone are also examined by histology and highresolution second-harmonic generation imaging, showing distinctive properties that match with the anatomical structure of articular cartilage. The segmentation algorithm is also applied on PS-OCT images acquired at multiple illumination angles, where the angular dependence of tissue birefringence in the deep zone is detected. This method offers a noninvasive imaging approach to differentiating the structural zones of articular cartilage, as well as a quantification approach based on the phase retardation measurements of PS-OCT. This method has great potential in studying depth-related progression of cartilage degeneration.

show abstract

“…Our previous study has reported that the depth-dependent property of RI was related to PGs in AC tissue. 18 The impact of mechanical wear and biochemical alteration to the depth distribution of RI still need to be further investigated.…”

Section: Introductionmentioning

confidence: 99%

“…The depth fluctuation of RI was characterized by using a previously developed method. 18 2 Materials and Methods…”

Section: Introductionmentioning

confidence: 99%

Characterizing depth-dependent refractive index of articular cartilage subjected to mechanical wear or enzymic degeneration

Wang

Day

et al. 2016

J. Biomed. Opt

Self Cite

View full text Add to dashboard Cite

Utilizing a laser scanning confocal microscope system, the refractive indices of articular cartilage (AC) with mechanical or biochemical degenerations were characterized to investigate whether potential correlations exist between refractive index (RI) and cartilage degeneration. The cartilage samples collected from the medial femoral condyles of kangaroo knees were mechanically degenerated under different loading patterns or digested in trypsin solution with different concentrations. The sequences of RI were then measured from cartilage surface to deep region and the fluctuations of RI were quantified considering combined effects of fluctuating frequency and amplitude. The compositional and microstructural alterations of cartilage samples were assessed with histological methods. Along with the loss of proteoglycans, the average RI of cartilage increased and the local fluctuation of RI became stronger. Short-term high-speed test induced little influence to both the depth fluctuation and overall level of RI. Long-term low-speed test increased the fluctuation of RI but the average RI was barely changed. The results substantially demonstrate that RI of AC varies with both compositional and structural alterations and is potentially an indicator for the degeneration of AC.

show abstract

Depth-dependent refractive index of normal and early degenerated articular cartilage

Cited by 8 publications

References 45 publications

Imaging of subchondral bone by optical coherence tomography upon optical clearing of articular cartilage

Imaging of subchondral bone by optical coherence tomography upon optical clearing of articular cartilage

Slope-based segmentation of articular cartilage using polarization-sensitive optical coherence tomography phase retardation image

Characterizing depth-dependent refractive index of articular cartilage subjected to mechanical wear or enzymic degeneration

Contact Info

Product

Resources

About