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Author: Vanessa Ngan, Staff Writer, 2006.
Spectrophotometric or spectral analysis of skin lesions refers to the use of a skin imaging device to help evaluate pigmented skin lesions (moles) and make it easier to identify and diagnose early stage malignant melanomas (skin cancers).
Spectrophotometric analysis is an advanced form of dermoscopy using a computer software program that calculates and extracts information about the cells and structures of the skin. Currently, most dermoscopic devices work by using a powerful lighting system and a high quality magnifying lens. Light penetrates the skin 20 microns deep and magnified digital photographic images are taken. Spectrophotometric analysis takes dermoscopy a step further by using a light beam that penetrates to a depth of 2-2.5 mm (1000x deeper) beneath the skin surface. Light images taken with a digital camera or hand-held scanner are then fed into a computer.
Spectrophotometric analysis works on the principle that light energy is absorbed and remitted by particular target cells with colour (chromophores) in the skin.
Spectrophotometric analysis is used to aid in the early detection and diagnosis of malignant melanoma. In expert hands, it has been shown to increase diagnostic accuracy (sensitivity) from around 70% by clinical examination alone, to 95%.
Devices discussed here are the SIAscope® and MelaFind®.
The SIAscope is a type of spectrophotometer. SIAscope stands for Spectrophotometric Intracutaneous Analysis and is a trademark of Astron Clinica Limited.
Spectrophotometric analysis is performed using a specialised digital camera to examine the skin.
|Contact spectrophotometric analysis||Non-contact spectrophotometric analysis|
MelaFind® is an automated multispectral device that has FDA approval for melanoma detection. In contrast to the SIAscope, MelaFind uses 75 features to evaluate the degree of 3-dimensional disorganisation in the tumour using 10 distinct wavelengths from blue light to near infrared. Highly disorganised lesions should be excised. Lesions with low disorganisation can be left alone.
It was designed to be used by dermatologists to help decide whether to remove suspicious pigmented lesions.
Patient details including history of the lesion are recorded. The lesion is identified and its location is carefully marked on a computer mannikin.
The pigmented lesion is first carefully sprayed with alcohol to provide a wet surface without bubbles for refractive index matching. The scanning head is placed on the skin centering the lesion of concern, and imaging commences. Six seconds later, ten images are displayed on the computer screen with the results of the analysis: biopsy or monitor.
The images are discarded if they are poor quality and the procedure is repeated.
Automatic analysis is in five parts.
MelaFind® is not used to confirm a typical melanoma, nor is it necessary for typical benign lesions. Skin lesions that are ideal for MelaFind® examination have the following characteristics:
Please note, this information was provided by the manufacturer of the devices. DermNet New Zealand's editors consider there is insufficient data to determine the role of these devices in the overall management of patients at risk of melanoma.
Patients concerned about melanoma should undergo full skin examination from a suitably trained health professional. Lesions of concern are best evaluated using derm(at)oscopy.
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