A non-invasive imaging system for assisting in the diagnosis of malignant melanoma

• Main Author: Cotton, Symon D'Oyly
• Published: University of Birmingham 1998
• Subjects: 610.21
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511481

Malignant melanoma is a malignant tumour of the pigment forming cells of the skin, the melanocytes, which normally reside within the epidermis abutting the dermo-epidermal junction. Although the cancer is dangerous, its treatment is frequently successful if the condition is detected at an early stage: typically whilst penetration into the dermis is less than 0.7mm. This thesis presents a non-invasive method for assisting in the diagnosis of malignant melanoma by quantifying diagnostically relevant histological information from the analysis of one colour and two infrared images of a lesion. In particular, it is shown that the presence of melanin can be detected when its invasion from the dermo-epidermal junction is 0.02mm. Through development of an optical image formation model of human skin it is shown that all normal skin colours lie on a two-dimensional surface within a three-dimensional colour-space. In contrast, colour co-ordinates corresponding to the penetration of melanin into the dermis deviate from this surface along characteristic paths and thus can be identified. This solution could not be directly applied because the colours resulting from a decrease in the thickness of the top layer of the dermis, the papillary dermis, can occupy the same position in the colour space as colours resulting from melanin descent. This ambiguity can be resolved by transforming the measured colour co-ordinates to compensate for the thickness of the papillary dermis. It is shown that this thickness can be obtained through the analysis of a pair of infrared images. It is further shown, although not experimentally verified, that the amount of epidermal melanin, dermal blood and thickness of the papillary dermis can also be quantified.