Fluorescence fibre-optic confocal microscopy of skin in vivo: microscope and fluorophores

BACKGROUND/AIMS

Fibre-optic confocal imaging in vivo is a new approach in the assessment of human skin. The objective is to describe a novel instrument and its operation and use in combination with fluorophores.

METHODS

The Stratum is a fibre-optic fluorescence confocal microscope especially developed for the study of skin and mucous membranes. The system is flexible and any body site can be studied with a hand-held scanner. The light source is a 488 nm argon ion laser. Horizontal (en face) images of the epidermis and outer dermis are produced with cellular resolution. Magnification is approximately 1000 x . Fluorescein sodium is routinely used as fluorophore (intradermal injection or application to the skin surface). This fluorophore is safe for human use in vivo, but other substances (rhodamine B, Acridine Orange, green fluorescent protein, curcumin) have also been studied.

RESULTS

The instrument produces sharp images of epidermal cell layers from the epidermal surface to the sub-papillary dermis, with sub-cellular resolution. The scanner is flexible in use. The technique of intradermal fluorophore injection requires some skill.

CONCLUSIONS

We consider this fibre-optic instrument a potentially important tool in skin research for non-invasive optical biopsy of primarily the epidermis. Present use is focussed on research applications, where the fluorophore distribution in the skin may illustrate morphological changes in the epidermis.

Instruments and new technologies for the in vivo diagnosis of melanoma

The principal objective of screening individuals at risk for melanoma is detection of cutaneous melanoma during the curable stages of its early evolution. Unaided visual inspection of the skin is often suboptimal at diagnosing melanoma. Improving the diagnostic accuracy for melanoma remains an area of active research. These research efforts have focused on both the detection of early melanoma and the in-depth evaluation of suspicious pigmented lesions for the presence or absence of melanoma. Numerous instruments are under investigation to determine their usefulness in imaging and ascertaining a correct in vivo diagnosis of melanoma. It is anticipated that some of these tools, alone or in combination, will improve our ability to differentiate, in vivo, melanoma from its simulators. Ultimately, these advances may prevent unnecessary biopsies (increased specificity) while increasing the sensitivity for diagnosing melanoma. This article reviews the current instruments and new technologies for the in vivo diagnosis of melanoma. Learning objective At the conclusion of this learning activity, participants should be acquainted with the instruments designed to facilitate the early detection of melanoma. They should also be familiar with the basic technology behind these instruments and should recognize the potential benefits and limitations inherent in each.

View of Normal Human Skin In Vivo as Observed Using Fluorescent Fiber-Optic Confocal Microscopic Imaging

Fluorescence confocal scanning laser microscopy, using a miniaturized handheld scanner, was performed to visualize the microscopic architecture of normal human epidermis in vivo. Fluorescein sodium (approximately 20 microL of 0.2% wt/vol) was administered via intradermal injection to normal skin on the volar forearm of 22 patients. The skin was imaged continuously from 1 to 15 min after injection. Fluorescein was excited at 488 nm and the fluorescent emission was detected at > 505 nm. In each subject, a series of images was collected at increasing depth, from superficial stratum corneum to papillary dermis. Features observed in confocal images were compared to those seen in hematoxylin- and eosin-stained sections of skin. The confocal images demonstrated the architecture of superficial skin in the horizontal plane. There was a transition in keratinocyte size, shape, and morphology with progressive imaging into the deeper epidermal layers. Superficial dermis and microscopic capillaries with blood flow were easily observed. The morphologic patterns associated with the major cell types of the epidermis were consistent with those known from conventional histology. We report the ability of in vivo fluorescence point scanning laser confocal microscopy to produce real-time, high-resolution images of the microscopic architecture of normal human epidermis using a noninvasive imaging technology.