Potential of contrast agents to enhance in vivo confocal microscopy and optical coherence tomography in dermatology: A review

Abstract

Distinction between normal skin and pathology can be a diagnostic challenge. This systematic review summarizes how various contrast agents, either topically delivered or injected into the skin, affect distinction between skin disease and normal skin when imaged by optical coherence tomography (OCT) and confocal microscopy (CM). A systematic review of in vivo OCT and CM studies using exogenous contrast agents on healthy human skin or skin disease was performed. In total, nine CM studies and one OCT study were eligible. Four contrast agents aluminum chloride (AlCl) n = 2, indocyanine green (ICG) n = 3, sodium fluorescein n = 3 and acetic acid n = 1 applied to CM in variety of skin diseases. ICG, acetic acid and AlCl showed promise to increase contrast of tumor nests in keratinocyte carcinomas. Fluorescein and ICG enhanced contrast of keratinocytes and adnexal structures. In OCT of healthy skin gold nanoshells, increased contrast of natural skin openings. Contrast agents may improve delineation and diagnosis of skin cancers; ICG, acetic acid and AlCl have potential in CM and gold nanoshells facilitate visualization of adnexal skin structures in OCT. However, as utility of bedside optical imaging increases, further studies with robust methodological quality are necessary to implement contrast agents into routine dermatological practice.

Transpathology: molecular imaging-based pathology

“…Optical coherence tomography (OCT) is applied with great success in the eye as well as in inner organs through endoscopes [ 99 ]. Besides, confocal microscopy (CM) has been widely utilized in skin diseases, like melanoma and inflammatory, aiding not only an in vivo diagnosis of skin abnormalities but also choosing better therapies and following the patient’s response to treatment [ 62 ].…”

Subclinical effects of adapalene‐benzoyl peroxide: a prospective in vivo imaging study on acne micromorphology and transfollicular delivery

“…19,20 In non-invasive optical imaging, the gold microparticles have shown to act as hyper-reflective contrast agents. [21][22][23] providing insight about hair follicle characteristics and density. The use of microparticle encapsulation for drug-laden carrier systems has been gaining traction.…”

“…Previous studies have demonstrated that transfollicular delivery is a feasible pathway to distribute 120 nm gold microparticles to the pilosebaceous unit 19,20 . In non‐invasive optical imaging, the gold microparticles have shown to act as hyper‐reflective contrast agents 21–23 . providing insight about hair follicle characteristics and density.…”

In vivo reflectance confocal microscopy of wounds: feasibility of intraoperative basal cell carcinoma margin assessment

“…However, this required topical application of aluminium chloride (AlCl) to optimise nuclear morphology brightening and BCC tumour-to-skin contrast (9). Misrepresented nuclear morphology and tissue necrosis could result depending on the concentration used (9,16). Moreover, they harbour risks for side effects (16).…”

“…Misrepresented nuclear morphology and tissue necrosis could result depending on the concentration used (9,16). Moreover, they harbour risks for side effects (16).…”