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Software is used to convert wavefront information into a 3D image reconstruction. The resulting images depict the distribution of the optical absorbers in tissue. In recent years, several optoacoustic approaches have been tested for skin imaging. The penetration depth of such systems is, however, fundamentally limited by light scattering and, therefore, similar to that of RCM or MPM.
To the best of our knowledge, microscopic optoacoustic devices have not yet entered clinical research.
The span of ultrasonic frequencies emitted by microvessels is very broad and depends on their size and depth. In RSOM, the area of interest is scanned line by line in raster mode using a single ultrasound detector combined with the illumination source. An important difference is that while HFUS employs narrowband signals e. This unprecedented performance has provided the first elaborate views of the microvascular tree of the skin, in which the smallest capillaries close to the epidermis are visible together with the larger arterioles and venules of the deep vascular plexus.
Optoacoustic mesoscopy can, therefore, image the vascular tree and melanin distribution with virtually no background signal, providing excellent contrast without the need for any exogenous label. This allows assessment of the allocation of oxyhemoglobin, deoxyhemoglobin and melanin within the skin Fig. In healthy skin, RSOM images allow for an evaluation of the epidermal melanin layer, the dermal capillary loops, the underlying horizontal plexus of the dermis and deeper laying dermal vessels Fig.
The measured epidermal thickness correlates quite well with histology. RSOM's ability to image epidermis morphology and vasculature down to capillary level has already been shown to deliver valuable information, which we highlight below in the context of several dermatological diseases. Psoriasis is a chronic autoimmune disease most commonly involving skin with multiple red plaques covered by silver scales.
Because of its characteristic microscopic appearance, histology constitutes an important tool for diagnosis. Currently, quantitative evaluation of psoriasis relies mainly on subjective clinical features: the widely used Psoriasis Area and Severity Index PASI is calculated from the appearance of plaque thickness, lesion redness, scaling and involved percentage of the body.
These findings, including vessel diameters, were in accordance with histology and immunohistochemistry Fig.
This study confirmed that teledermatoscopy can be a reliable technique but is dependent on the expertise of the observing physician. O ptical coherence tomography OCT is a noninvasive imaging technique that is cleared by the US Food and Drug Administration as a k class II regulatory device to visualize biological tissues in vivo and in real time. Dermatol Bull ; — J Am Acad Dermatol. The DermEngine imaging and analytics system is the most advanced web-based solution for capturing and analyzing images of the skin, hair, and nails. Dermatoscopy is a valuable and convenient tool in routine clinical examinations.
These features include the thickness of the epidermis, total blood volume in the dermis, fractal number of the vascular structure, as well as density and mean diameter of the capillary loops. Eczema is a different type of skin inflammation largely of atopic, toxic or allergic origin and characterized by erythema, papules and itching, sometimes as well as blisters or lichenification. In skin affected by atopic eczema, RSOM imaging detected less acanthosis and elongation of the capillary loops than in psoriatic skin.
This diagnostic approach is, however, limited to superficial layers of the nail fold's microvascular structure, and dry or thickened epidermis can severely compromise image quality. RSOM imaging of superficial nail fold vasculature gave estimates of vessel density and capillary diameter that agreed extremely well with estimates obtained with conventional microscopy. These two parameters are widely used biomarkers of scleroderma progression.
This capability may allow RSOM to facilitate diagnosis of malignant skin lesions and determination of tumour excision margins. Research is underway to extend multispectral RSOM to other skin components such as lipids by illuminating the skin with infrared light. While current RSOM devices demonstrate the potential of the technique there are still certain limitations.
One current shortcoming of RSOM, when compared, e. Their implementation, together with shortened scan times due to innovative detector technologies beyond the scope of this article, is expected to improve image quality in such examinations. Microscopic dermatological imaging modalities penetrate down to only a few hundred micrometres. In addition, these mesoscopic methods at best only partially resolve the skin's microvascular structure. Volume 33 , Issue 6. The full text of this article hosted at iucr.
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Aguirre Corresponding Author E-mail address: juanaguir gmail. Funding sources The authors have received funding from the European Union's Horizon research and innovation programme under grant agreement no. Tools Request permission Export citation Add to favorites Track citation.
Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Introduction There is a wide range of dermatologic diseases that cannot be diagnosed or evaluated sufficiently by visual inspection alone.
Typical field of view, mm 2 0. Current state of development Clinical practice Clinical research Clinical practice Clinical practice Clinical research. Dermatologic imaging methods based purely on optical or ultrasound excitation Microscopy methods Reflectance confocal microscopy RCM is increasingly being used in routine clinical dermatology. Mesoscopy methods Mesoscopic imaging modalities compensate for light scattering, providing deeper penetration.
Smaller structures e. The heating causes reactive vasodilation. The elongated capillary loops green nearly reach the skin surface and appear interwoven with the depigmented and acanthotic epidermis red with low contrast, EP. In the underlying dermal layer DR , the vessels of the dermal plexus appear dilated and organized in a dense manner. The tips of the capillary loops appear as green dots.
Histology shows increased dermal vascularization, papillomatosis and elongated capillary loops. Bottom row: Differences between measurements in psoriatic vs. Capillary loops white arrow are longer and more dilated than in healthy skin but appear more irregularly and sparsely distributed than in psoriatic skin [see panels a and b ]. Vessels of the dermal plexus are dilated. Yellow arrow marks capillaries that lie close to the base of the nail and are oriented parallel to the skin surface.
Brown arrow highlights capillaries farther away from the nail, oriented perpendicular to the skin. For accurate documentation of a skin condition, it is important to take, at the very least, three types of images:. Macro images photomacrography or macro photography are close-up images of a subject. In dermatology, it usually refers to close-up images of a lesion or dermatosis.
Normally anatomical context is largely lost due to the image being focused on the lesion or dermatosis to the exclusion of surrounding anatomic structures. If smaller sized sensors are used in digital cameras, smaller ratios can be used to obtain the life-sized capture of a lesion or dermatosis. Micro images or photomicrography in general refer to the imaging of a subject lesions or dermatoses in dermatology with a greater than scale of reproduction.
With increasing magnification of a subject, all anatomic landmarks are lost with this degree of magnification. Most commonly in dermatology, dermatoscopic imaging is capturing a lesion that has already had roughly 10—15x magnification. Micro images in dermatology also encompasses the capturing the images directly from a microscope at x 5, x 10, x 20, x 40, and x magnification.
Even more extreme magnifications can be used to image tiny parasites like mites , fleas, lice and other subjects with portable USB digital microscopes. See smartphone apps to check your skin.