Effect of Heat Level and Expose Time on Denaturation of Collagen Tissues.

INTRODUCTION: The applied heat level and expose time are main issues in certain operations/applications, such as a laser assisted tissue welding, preparation of collagen-based biomaterials (films, implants). Therefore, the precise investigation of these parameters is crucial. The results can serve as a guideline to assess potential effects while maintaining the functionality of the collagen structures. METHODS: Collagen tissues from rat-tail tendon, calfskin, and bones are soaked in buffer solutions, then examined by microscope at different temperature levels. RESULTS: Increase in temperature reduced the microscopically observed collagen crimp contrast for calfskin and rat-tail tendons but not for bone tissues. The contrast level for rat tail tendon decreased down to 80% of its initial value at 37, 157, and 266 s for 70, 65, and 60 °C, respectively. The decrease in the crimp contrast was about only 25% and 2% at 55 and 50 °C after 2 h, respectively. 50% drop in contrast level was occurred for the skin samples at 16, 90, 110 and 1900 s for 70, 65, and 60 °C, respectively. The bone samples, did not show any significant differences in contrast levels. CONCLUSION: The observed denaturation behaviours are in line with Arrhenius Law. This study could be expanded on to other types of tissues at wider temperature ranges to make a guideline for biological/medical processes that radiate heat in order to assess their side effects on collagen and other proteins.

Monitoring system for investigating the effect of temperature change on optical properties.

Knowledge about the changes in optical properties is needed for planning safer and more accurate laser treatments. A monitoring system was developed to study how the optical properties of a lipid emulsion are affected by temperature changes. A double-integrating-sphere system is modified with a controlled heating apparatus to measure the temperature-dependent diffuse reflectance and total transmittance values. The absorption and reduced scattering coefficients were estimated from the reflectance and transmittance values using an inverse adding-doubling method. The total transmittance showed positive correlation with temperature while the diffuse reflectance was found to be negatively correlated. Although the absorption coefficient did not demonstrate a statistically significant change with temperature, the reduced scattering coefficient was negatively correlated. By using the obtained optical properties, Monte Carlo simulations were performed to observe the difference in light propagation within a tissue. The results indicate that temperature-dependent changes in optical properties should be taken into consideration for a safer laser treatment.

Temperature-dependent optical properties of individual vascular wall components measured by optical coherence tomography.

Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n and the attenuation coefficient mu(t) using optical coherence tomography (OCT) of individual vascular wall layers and plaque components. Moreover, since the temperature dependence of optical properties is widely known, we compare measurements at room and body temperatures. A decrease of n and mu(t) is observed in all samples, with the most profound effect on samples with high lipid content. The sample temperature is of influence on the quantitative measurements within OCT images. For extrapolation of ex-vivo experimental results, especially for structures with high lipid content, this effect should be taken into account.

Comparative optical coherence tomography imaging of human esophagus: how accurate is localization of the muscularis mucosae?

BACKGROUND: Early diagnosis of esophageal cancer limited to the mucosa allows local endoscopic treatment and thereby improves prognosis. Optical coherence tomography images of normal human esophageal tissue obtained with 2 systems with light sources that provide different wavelengths (800 nm and 1275 nm) were compared with histology to determine which wavelength is best suited for detailed optical coherence tomography imaging of the esophageal wall, and to precisely localize the muscularis mucosae. METHODS: Within 1 hour of surgical resection, an esophageal specimen was cleaned of excess blood with saline solution and soaked in formalin for a minimum of 48 hours. After optical coherence tomography imaging, the specimen was prepared for routine histologic assessment. To precisely localize the different layers of the esophageal wall on an optical coherence tomography image, well-defined structures within the esophageal wall were sought. RESULTS: The 1275 nm system with 12 mm resolution was superior in terms of imaging depth. As compared with histology, the 4 microm resolution of the 800 nm system made fine detail more visible. With minimal experience, the muscularis mucosae could be recognized with either system as a hyporeflective layer with a diameter of around 180 microm. CONCLUSIONS: Based on appearance and location of morphologic landmarks, layers of normal esophageal wall, specifically, the location and extent of the muscularis mucosae, could be recognized by using both the 800 nm and 1275 nm optical coherence tomography system. Although different conditions may be operative in vivo, the present ex vivo study further verifies by precise interpretation that optical coherence tomography provides precise images of the esophageal wall.