Noninvasive Optical Imaging Techniques as a Quantitative Analysis of Kaposi's Sarcoma Skin Lesions

Abstract

The visible inspection and palpation of skin lesions have long been used to assess the course of cutaneous disease in individuals with Kaposi's sarcoma (KS). Assessing the KS lesions requires a highly trained evaluator and evaluations made by different observers or by the same observer at different times can be inconsistent. Since lesions can grow from slow to explosively fast, and be associated with mortality and morbidity, reliable assessment of the lesions is important.

Optical imaging techniques are quantitative methods that potentially offer a more objective means of assessing skin health that can supplement visual clinical observations. In this dissertation, the first paper describes using thermography and laser Doppler imaging (LDI) to monitor the temperature and vasculature, respectively, of KS lesions undergoing experimental therapy. Results showed that the median temperature elevation of lesions compared to the surrounding tissue was 1.1 ºC (range -0.68 to 3.43 ºC). In addition, 12 of the 16 lesions studied had increased blood perfusion as assessed by LDI (median 66 arbitrary units (AU), range -44 to 451 AU).

The second paper describes the use of near-infrared (NIR) multi-spectral imaging to provide functional information about the lesions and surrounding tissue. Multi-spectral images were input to a mathematical optical skin model based on the absorption and scattering properties of skin, including the effects of melanin, blood, and oxygenated and deoxygenated hemoglobin. Functional information about the lesions before and after treatment with experimental therapies was determined.

The third paper describes Monte-Carlo simulations of tissue conducted to determine the detection limits of a typical multi-spectral imaging system. The results showed that biological information contained in a typical spectral image reflected a small volume of tissue situated vertically under each pixel from a depth less than 2-3 mm. The objects appearing on a spectral image reasonably reproduce the correct geometrical shape and size of underlying inclusions of pathological tissue.

Based on the three papers included in this dissertation, these three imaging techniques were found to be objective, easy to perform, and appear to be very sensitive in quantitatively assessing KS lesion progress upon administration of therapy.