Laser-induced micropore formation and modification of cartilage structure in osteoarthritis healing

Infrared (IR) laser impact has no analogues for rapid and safe cartilage reshaping. For better penetration of radiation optical clearing agents (OCAs) can be applied. In present work, the effect of low-osmolality agent iohexol on costal cartilage is studied. Specifically, it is shown that ½ of total increase of optical transparency occurs in 20 minutes of immersion. Maximally, cartilage transparency on 1560 nm can be increased in 1.5 times. Injection of iohexol results in increased tissue hygroscopicity, lower drying rate and higher percentage of bound water. Effective diffusion coefficients of water liberation at 21°C are (5.3 ± 0.4) × 10 and (3.3 ± 0.1) × 10 cm /s for untreated and iohexol-modified tissue, respectively. Raman spectroscopy of irradiated iohexol solution reveals its photo and thermo-stability under clinically used IR laser energies up to 350 W/cm for exposure times of several seconds. At energies higher than 500 W/cm [Correction added on 5 September 2018, after first online publication: This unit has been changed] decomposition of iohexol occurs rapidly through formation of molecular iodine and fluorescent residue.

Section: Resultsmentioning

confidence: 99%

Control of optical transparency and infrared laser heating of costal cartilage via injection of iohexol

Alexandrovskaya

Evtushenko

Obrezkova

et al. 2018

“…Detailed quantitative OCT‐based elastographic measurements of the postheating reduction of the Young modulus in the irradiated spot and accompanying cumulative tissue dilatation attributed these phenomena to formation of micropores. The latter were not directly resolved by OCT, but their appearance in the laser‐heated collagenous tissues was supported by direct microscopic observations . Formation of such pores is related to irradiation‐induced breaking of a part of internal bonds between the collagenous filaments in the tissue.…”

Section: Discussionmentioning

confidence: 99%

“…The expressions for the radial and angular components of the thermal stress tensor were obtained in the analytical form by solving the thermoelasticity equations assuming cylindrical symmetry of the temperature field T ( r )created by the heating laser beam. Then, under laser irradiation of a tissue layer by laser beam with cylindrical symmetry, the resultant thermal stress (described by the difference between the angular and radial component of the thermal stress tensor) can be written in the following form convenient for numerical integration, which we used earlier in works :

σ_{therm} = italicαE ((), - normalΔ T ((), r) + \frac{2}{r^{2}} \int_{0}^{r} normalΔ T ((), r') r' italicdr')

where α is the coefficient of thermal expansion, E is the Young modulus and Δ T ( r ) is the temperature increase from the background value. Taking into account that for biological tissues with Poisson's ratio close to 0.5, the Young modulus E is related to shear modulus G as E = 3 G and the nomalized temperture increase can be written as

normalΔ \overset{T}{true} ((), r) = normalΔ T ((), r) / normalΔ T ((), r = 0)

.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, laser irradiation can contribute to regeneration of cartilage because chondrocytes are sensitive to external conditions, in particular to temperature and mechanical stress . It is found that pulse‐periodic nonablative laser radiation leads to formation of pores with submicrometer size near the cells of hyaline cartilage, which contributes to the tissue nutrition and its regeneration . From the viewpoint of the effect of radiation on the expression of the chondrocyte gene and the collagen matrix, the cellular response to laser irradiation differs from the cellular response observed in the usual healing of wounds.…”

Section: Introductionmentioning

confidence: 99%

“…Heating above this temperature is accompanied by abrupt changes in thermally induced speckle dynamics due to the change in the dynamic scattering mechanism . In addition, inhomogeneous laser heating leads to pore formation due to thermal stresses . Thus, the temperature‐induced changes in the speckle properties can serve as an indicator for nondestructive modifications of the cartilage structure.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interplay of temperature, thermal‐stresses and strains in laser‐assisted modification of collagenous tissues: Speckle‐contrast and OCT‐based studies

Baum

Zaitsev

Yuzhakov

et al. 2019

Moderate heating of collagenous tissues such as cartilage and cornea by infrared laser irradiation can produce biologically nondestructive structural rearrangements and relaxation of internal stresses resulting in the tissue reshaping. The reshaping results and eventual changes in optical and biological properties of the tissue strongly depend on the laser‐irradiation regime. Here, a speckle‐contrast technique based on monochromatic illumination of the tissue in combination with strain mapping by means of optical coherence elastography (OCE) is applied to reveal the interplay between the temperature and thermal stress fields producing tissue modifications. The speckle‐based technique ensured en face visualization of cross correlation and contrast of speckle images, with evolving proportions between contributions of temperature increase and thermal‐stresses determined by temperature gradients. The speckle‐technique findings are corroborated by quantitative OCE‐based depth‐resolved imaging of irradiation‐induced strain‐evolution. The revealed relationships can be used for real‐time control of the reshaping procedures (e.g., for laser shaping of cartilaginous implants in otolaryngology and maxillofacial surgery) and optimization of the laser‐irradiation regimes to ensure the desired reshaping using lower and biologically safer temperatures. The figure of waterfall OCE‐image demonstrates how the strain‐rate maximum arising in the heating‐beam center gradually splits and drifts towards the zones of maximal thermal stresses located at the temperature‐profile slopes.

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Zaitsev

Matveyev

Matveev

et al. 2018

Moderate heating of such collagenous tissues as cornea and cartilages by infra‐red laser (IR laser) irradiation is an emerging technology for nondestructive modification of the tissue shape and microstructure for a variety of applications in ophthalmology, otolaryngology and so on. Postirradiation high‐resolution microscopic examination indicates the appearance of microscopic either spheroidal or crack‐like narrow pores depending on the tissue type and irradiation regime. Such examinations usually require special tissue preparation (eg, staining, drying that affect microstructure themselves) and are mostly suitable for studying individual pores, whereas evaluation of their averaged parameters, especially in situ, is challenging. Here, we demonstrate the ability of optical coherence tomography (OCT) to visualize areas of pore initiation and evaluate their averaged properties by combining visualization of residual irradiation‐induced tissue dilatation and evaluation of the accompanying Young‐modulus reduction by OCT‐based compressional elastography. We show that the averaged OCT‐based data obtained in situ fairly well agree with the microscopic examination results. The results obtained develop the basis for effective and safe applications of novel nondestructive laser technologies of tissue modification in clinical practice. PICTURE: Elastographic OCT‐based images of an excised rabbit eye cornea subjected to thermomechanical laser‐assisted reshaping. Central panel shows resultant cumulative dilatation in cornea after moderate (~45‐50°C) pulse‐periodic heating by an IR laser together with distribution of the inverse Young modulus 1/E before (left) and after (right) IR irradiation. Significant modulus decrease in the center of irradiated region is caused by initiated micropores. Their parameters can be extracted by analyzing the elastographic images.