Elena Salomatina

Optical properties of normal and cancerous human skin in the visible and near-infrared spectral range

Differences in absorption and/or scattering of cancerous and normal skin have the potential to provide a basis for noninvasive cancer detection. In this study, we have determined and compared the in vitro optical properties of human epidermis, dermis, and subcutaneous fat with those of nonmelanoma skin cancers in the spectral range from 370 to 1600 nm. Fresh specimens of normal and cancerous human skin were obtained from surgeries. The samples were rinsed in saline solution and sectioned. Diffuse reflectance and total transmittance were measured using an integrating sphere spectrophotometer. Absorption and reduced scattering coefficients were calculated from the measured quantities using an inverse Monte Carlo technique. The differences between optical properties of each normal tissue-cancer pair were statistically analyzed. The results indicate that there are significant differences in the scattering of cancerous and healthy tissues in the spectral range from 1050 to 1400 nm. In this spectral region, the scattering of cancerous lesions is consistently lower than that of normal tissues, whereas absorption does not differ significantly, with the exception of nodular basal cell carcinomas (BCC). Nodular BCCs exhibit significantly lower absorption as compared to normal skin. Therefore, the spectral range between 1050 and 1400 nm appears to be optimal for nonmelanoma skin cancer detection.

Fluorescence polarization of tetracycline derivatives as a technique for mapping nonmelanoma skin cancers

Nonmelanoma skin cancer is the most common form of human cancer, often resulting in high morbidity. Low visual contrast of these tumors makes their delineation a challenging problem. Employing a linearly polarized monochromatic light source and a wide-field CCD camera, we have developed a technique for fluorescence polarization imaging of the nonmelanoma cancers stained using antibiotics from the tetracycline family. To determine the feasibility of the method, fluorescence polarization images of 86 thick, fresh cancer excisions were studied. We found that the level of endogenous fluorescence polarization was much lower than that of exogenous, and that the average values of fluorescence polarization of tetracycline derivatives were significantly higher in cancerous as compared to normal tissue. Out of 86 tumors [54 stained in demeclocycline (DMN) and 32 in tetracycline (TCN)], in 79 cases (51-DMN, 28-TCN) the location, size, and shape of the lesions were identified accurately. The results of this trial indicate that nonmelanoma skin tumors can be distinguished from healthy tissue based on the differences in exogenous fluorescence polarization of TCN and/or DMN. Therefore, the developed technique can provide an important new tool for image-guided cancer surgery.

Multimodal optical imaging and spectroscopy for the intraoperative mapping of nonmelanoma skin cancer

Basal cell carcinoma (BCC) is the most common human malignancy, and its incidence increases yearly. In this contribution we investigate the feasibility of combining multimodal reflectance and fluorescence polarization imaging (RFPI) with spectroscopic analysis of the reflectance images for facilitating intraoperative delineation of BCCs. Twenty fresh thick BCC specimens were obtained within 1 h after Mohs micrographic surgeries. The samples were soaked for up to 2 min in an aqueous 0.2 mg/ml solution of methylene blue, briefly rinsed in saline solution, and imaged. Reflectance images were acquired in the range from 395 to 735 nm, with steps of 10 nm. Fluorescence polarization images were excited at 630 nm and registered in the range between 660 and 750 nm. The results yielded by RFPI were qualitatively compared to each other and to histopathology. From the copolarized reflectance images the spectral responses including the optical densities and their wavelength derivatives were calculated. The differences...

High-contrast mapping of basal cell carcinomas

Because of low optical contrast in the visible spectral range, accurate detection of basal cell carcinomas (BCC) remains a challenging problem. In this letter, we experimentally demonstrate that reflectance confocal imaging in the vicinity of 1300 nm can be used for the detection of BCC without exogenous contrast agents. We present high-contrast reflectance confocal images of thick fresh skin tissues with clearly delineated cancer and discuss possible reasons for causing decreased scattering of BCC. Comparison with histopathology confirms that tumors scatter less and exhibit lower pixel values in the images, as compared to benign skin structures. The results demonstrate the feasibility of real-time noninvasive detection of BCC using intrinsic differences in scattering between tumors and normal skin.

Dye-enhanced reflectance and fluorescence confocal microscopy as an optical pathology tool

Early detection and precise excision of neoplasms are imperative requirements for successful cancer treatment. In this study we evaluated the use of dye-enhanced confocal microscopy as an optical pathology tool in the ex vivo trial with fresh thick non-melanoma skin cancer excisions and in vivo trial with B16F10 melanoma cancer in mice. For the experiments the tumors were rapidly stained using aqueous solutions of either toluidine blue or methylene blue and imaged using multimodal confocal microscope. Reflectance images were acquired at the wavelengths of 630nm and 650 nm. Fluorescence was excited at 630 nm and 650 nm. Fluorescence emission was registered in the range between 680 nm and 710 nm. The images were compared to the corresponding en face frozen H&E sections. The results of the study indicate confocal images of stained cancerous tissue closely resemble corresponding H&E sections both in vivo and in vitro. This remarkable similarity enables interpretation of confocal images in a manner similar to that of histopathology. The developed technique may provide an efficient real-time optical tool for detecting skin pathology.

Low-level light therapy for zymosan-induced arthritis in rats

It has been known for many years that low level laser (or light) therapy (LLLT) can ameliorate the pain, swelling and inflammation associated with various forms of arthritis. Light is absorbed by mitochondrial chromophores leading to an increase in ATP, reactive oxygen species and/or cyclic AMP production and consequent gene transcription via activation of transcription factors. However, despite many reports about the positive effects of LLLT in medicine, its use remains controversial. Our laboratory has developed animal models designed to objectively quantify response to LLLT and compare different light delivery regimens. In the arthritis model we inject zymosan into rat knee joints to induce inflammatory arthritis. We have compared illumination regimens consisting of a high and low fluence (3 J/cm2 and 30 J/cm2), delivered at a high and low irradiance (5 mW/cm2 and 50 mW/cm2) using 810-nm laser light daily for 5 days, with the effect of conventional corticosteroid (dexamethasone) therapy. Results indicated that illumination with 810-nm laser is highly effective (almost as good as dexamethasone) at reducing swelling and that longer illumination time was more important in determining effectiveness than either total fluence delivered or irradiance. Experiments carried out using 810-nm LLLT on excisional wound healing in mice also confirmed the importance of longer illumination times. These data will be of value in designing clinical trials of LLLT.

Dye-Enhanced Confocal Microscopy as an Optical Pathology Tool

Dye-enhanced multi-modal confocal microscopy provides an efficient real-time optical pathology tool. Reflectance and fluorescence confocal images are remarkably similar to histology. Fluorescence polarization registered from cancer is higher than that of other structures.

Wound healing stimulation in mice by low-level light

It has been known for many years that low levels of laser or non-coherent light (LLLT) accelerate some phases of wound healing. LLLT can stimulate fibroblast and keratinocyte proliferation and migration. It is thought to work via light absorption by mitochondrial chromophores leading to an increase in ATP, reactive oxygen species and consequent gene transcription. However, despite many reports about the positive effects of LLLT on wound healing, its use remains controversial. Our laboratory has developed a model of a full thickness excisional wound in mice that allows quantitative and reproducible light dose healing response curves to be generated. We have found a biphasic dose response curve with a maximum positive effect at 2 J/cm2 of 635-nm light and successively lower beneficial effects from 3-25 J/cm2, the effect is diminished at doses below 2J/cm2 and gradually reaches control healing levels. At light doses above 25 J/cm2 healing is actually worse than controls. The two most effective wavelengths of light were found to be 635 and 820-nm. We found no difference between filtered 635±15-nm light from a lamp and 633-nm light from a HeNe laser. The strain and age of the mouse affected the magnitude of the effect. Light treated wounds start to contract after illumination while control wounds initially expand for the first 24 hours. Our hypothesis is that a single brief light exposure soon after wounding affects fibroblast cells in the margins of the wound. Cells may be induced to proliferate, migrate and assume a myofibroblast phenotype. Our future work will be focused on understanding the mechanisms underlying effects of light on wound healing processes.