Optoacoustic imaging of the skin

Abstract

Optoacoustic (OA, photoacoustic) imaging capitalizes on the synergistic combination of light excitation and ultrasound detection to empower biological and clinical investigations with rich optical contrast while effectively bridging the gap between micro and macroscopic imaging realms. State-of-the-art OA embodiments consistently provide images at micron-scale resolution through superficial tissue layers by means of focused illumination that can be smoothly exchanged for acoustic-resolution images at diffuse light depths of several millimetres to centimetres via ultrasound beamforming or tomographic reconstruction. Taken together, this unique multi-scale imaging capacity opens unprecedented capabilities for high-resolution in vivo interrogations of the skin at scalable depths. Moreover, diverse anatomical and functional information is retrieved via dynamic mapping of endogenous chromophores such as haemoglobin, melanin, lipids, collagen, water and others. This, along with the use of non-ionizing radiation, facilitates a clinical translation of the OA modalities. We review recent progress in OA imaging of the skin in preclinical and clinical studies exploiting the rich contrast provided by endogenous substances in tissues. The imaging capabilities of existing approaches are discussed in the context of initial translational studies on skin cancer, inflammatory skin diseases, wounds and other conditions.

Three dimensional confocal photoacoustic dermoscopy with an autofocusing sono‐opto probe

“…Figure 3A shows the experimental result about diameters of the optical and acoustic focal spots as functions of the applied voltage. As the applied voltage is increased, the interface deformities of two immiscible liquids become more obvious so that the radius of curvature of the interface is decreasing, which eventually causes the focal length to decrease, according to Equation (1). Owing to the performance of varifocal lens is affected by the f-number, the resolution of 3D-CPAD can be changed as the variation of confocus.…”

“…Photoacoustic dermoscopy (PAD), an important embranchment of optical absorption-based photoacoustic microscopy (PAM), can be used to acquire highspatial-resolution imaging of skin tissue with high contrast based on its strong optical absorption and deep acoustic penetration [1][2][3] and allow functional and structural information via the visualization of skin structures in vivo [4,5]. Over the recent years, lots of integrated PADs have been developed for the diagnosis of skin diseases such as melanoma [6,7], port-wine stains [8,9], psoriasis [10], café au lait spots [11], pigmented nevus [12], scar [13] and human cuticle microvasculature [14,15] imaging.…”

The Potential of Photoacoustic Imaging in Radiation Oncology

“…For example, in a salivary gland stimulation challenge conducted in mouse models, a decrease in sO 2 change between measurements taken before and after salivary stimulation post-EBRT was associated with radiation-induced salivary gland toxicity in a murine model assessed with macroscopic PAI ( Figure 1B ) ( 60 ). Mesoscopic implementations of PAI can achieve ~20 μm in-plane resolution up to ~3 mm in depth for skin imaging ( 52 , 127 ), indicating potential for clinical skin toxicity assessment ( 128 ). Preliminary work on skin atopic dermatitis grading ( 61 ) showed that combining PAI mesoscopy-derived total blood volume, average vessel diameter, and ratio of low to high frequency signals gave a discriminating signature for atopic skin dermatitis grade ( Figure 1C ) ( 129 ).…”

Multiscale confocal photoacoustic dermoscopy to evaluate skin health

“…It has greatly reduced the effect of tissue scattering of photons using one-way ultrasound detection while retaining a high optical absorption contrast (16)(17)(18)(19)(20)(21)(22)(23). Successful use of PAM has been reported in numerous studies (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), including observations of cell distribution, monitoring of vascularization, and label-free photoacoustic (PA) angiography. However, the opto-sono objective in most PAM setups is insufficient for clinical use in dermatology given its single-scale mode (single magnification or depth of focus), which results in a poor depth of resolution and a low signal-to-noise ratio (SNR).…”