Diffuse multispectral imaging uses multiple wavelengths light source in the near infrared spectral range and provides 2D functional image. The preferred wavelengths are chosen according the optical properties of a given lesion based on peak absorption, depth, and characteristics of the overlying tissue. Chromophores absorb and transmit photons and determine the color of a certain organic compound. Hemoglobin, (oxygenated/deoxygenated), melanin, collagen, contain chromophores that can be imaged optically. For skin imaging, this technique is widely used for imaging hemoglobin. Since the absorption characteristics of oxygenated and deoxygenated hemoglobin are quite different from each other, it is possible to distinguish and assess each separately. Using mathematical models to describe how light interacts with the skin for each wavelength and combining multiple wavelength images, quantitative subsurface hemoglobin maps can be reconstructed.
The limitations of such techniques lie in the resolution, depth information, as well as computational expensiveness of reconstruction algorithms, which make real time assessment of those parameters difficult. However, recent work has shown that real-time quantitative hemoglobin maps can be obtained by using novel data analysis tool and computational mathematical algorithm.
Treatment response in cutaneous vascular lesions
The sub-surface hemoglobin maps has shown to provide information about the metabolic state of the HIV associated Kaposi’s Sarcoma to assess the severity and sub-surface area of involvement in addition to and follow up evaluation of treatment response with accurate histopathological correlation.
Application in other vascular skin lesions
Other cutaneous vascular lesions can be qualitatively and semi-quantitatively assessed to evaluate the sub-surface extent of involvement at the base line. This can be used for comparison on follow up images to evaluate efficacy of treatment and guide further or termination of therapeutic plan.
Qualitative and quantitative sub-surface assessment of epidermal and dermal chromophores
Qualitative (sub-surface optical parametric and characteristics of chromophores, not influence by the overlying tissue or light) and quantitative (sub-surface percentage of various chromophores with their specific optical characteristics contributing to the final coloration of a particular lesion of interest as perceived from the surface) assessment of the chromophores which are contributing to the final coloration of the lesion of interest as seen or perceived from the surface can help plan and guide a more precise therapeutic Laser delivery.
Quantitative and objective qualitative assessment of pigmented lesions
In a recent study on pigmented lesions with multispectral imaging analysis showed that melanoma has a higher absorbance and uneven distribution of chromophores. These are some of the features that may allow potential differentiation of malignant vs benign in pigmented lesions in the future.