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Science Translational Medicine  24 May 2017:
Vol. 9, Issue 391, eaan4292
DOI: 10.1126/scitranslmed.aan4292

Abstract

Noninvasive ultra-broadband optoacoustic mesoscopy skin imaging technology may provide objective assessment of skin disease.

The skin is the most accessible tissue in the human body. Paradoxically, noninvasive tools to objectively measure and quantify disease severity have proven difficult to develop. As an example, in clinical trials, assessments of the three most common skin diseases (acne vulgaris, psoriasis, and atopic dermatitis) rely on subjective evaluations. Although in daily practice diagnosing these and other skin diseases is straightforward, quantifying severity and monitoring disease remain subjective. This in turn negatively affects research—especially comparative effectiveness studies. Therefore, there is a need for objective, noninvasive, user-friendly, and validated assessment tools to measure inflammatory skin diseases.

Aguirre et al. report the development of a new hand-held, skin imaging technology: ultra- broadband raster-scan optoacoustic mesoscopy (UB-RSOM). The researchers innovatively combined ultra-short photon pulses—generated by laser fiber bundles to excite a wide spectrum of ultrasound frequencies—with a unique transducer that captures optoacoustic signals over a wide range of bandwidths. This allowed them to image deep into the dermis, without losing the ability to capture high-resolution functional images of the skin’s layers and vascular network. As proof-of-concept, the investigators characterized the differences between normal and psoriatic human skin in vivo using UB-RSOM. They demonstrated specific changes in lesional psoriatic skin compared with unaffected adjacent skin, such as epidermal thickness and vascular spatial complexity, and created a scoring system, which they validated in a small number of subjects.

UB-RSOM appears to take noninvasive skin imaging a step forward by maintaining good image resolution with deeper penetration without the use of labels. Additionally, it can scan 16 mm2 (about the size of a typical skin biopsy) in 80 s and has axial and lateral resolutions of 4.5 and 18.4 μm, respectively, which are maintained at least 1.5 mm into the dermis. These properties make UB-RSOM relevant to clinical practice and may prove useful in imaging subsurface features of other organ systems, such as the vasculature. However, challenges remain; for example, UB-RSOM does not resolve to a single-cell level. It is also unclear if the features differentiating psoriatic skin from normal skin demonstrated in the study are unique to psoriatic skin or may be common in many other inflammatory dermatoses. Additionally, the authors claim that the technology is insensitive to motion (a drawback of other skin imaging devices); however, they excluded subjects from analysis because motion during image acquisition resulted in artifact. Further research and time will tell if this exciting new technology will put noninvasive skin imaging in focus.

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