Multimodal invivo skin imaging Janis Spigulis Biophotonics Laboratory

Multimodal in-vivo skin imaging Janis Spigulis Biophotonics Laboratory, Institute of Atomic Physics and Spectroscopy, University of Latvia janis. spigulis@lu. lv ABSTRACT Multimodal imaging has a number of promising applications in skin diagnostics and recovery monitoring. Three multimodal skin imaging prototype devices developed and tested in the Biophotonics Laboratory of IAPS, UL are presented, along with a brief description of the running project on this topic. More details on our prototype designs – in a review paper: J. Spigulis, “Multispectral, fluorescent and photoplethysmographic imaging for remote skin assessment”, Sensors, 17, 1165 (2017). Sk. Imager A proof-of-concept device that performs complex multimodal skin imaging by recording: • RGB reflectance image at white polarized illumination reveals subcutaneous structures • 4 spectral images (450, 540, 660, 940 nm) calculates distribution maps of skin melanin, haemoglobin, bilirubin, erythema index, melanoma/nevus index • Photoplethysmography video-image at green illumination PPG amplitude distribution skin blood perfusion mapping • Autofluorescence video-image at UV-excitation map of photo-bleaching rates skin fluorophore map Provides: • Mapping of melanin, oxy-/deoxy-hemoglobin and bilirubin distribution in skin • Maping of erythema index and melanoma index • Mapping of skin fluorophore clusters • Mapping of skin blood perfusion Reference: J. Spigulis et al. «Sk. Imager: a concept device for in-vivo skin assessment by multimodal imaging» . Proc. Est. Acad. Sci. , 63(3), 213 -220 (2014). Melanoma checker Combined multi-spectral and autofluoresce imaging ensures fast assessment of skin cancer (malignant melanoma) with high sensitivity and specificity (>90%). The prototype collects three spectral images (peak wavelengths 526 nm, 663 nm and 964 nm), as well as a fluorescence image under 405 nm excitation. After the image processing by cloud technology, value of a specific melanoma criterion is calculated for the suspicious skin malformation. Hundreds of clinical in-vivo measurements have confirmed high efficiency of the developed technology. Reference: V. Lukinsone et al. , “Multispectral and autofluorescence RGB imaging for skin cancer diagnostics”, Proc. SPIE 11065, 110650 A (2019). Combined multispectral / thermal skin imager Compact multimodal imaging device (technology demonstrator) with a dual modality camera system was developed. The prototype involves a single-snapshot mosaic type camera for fast acquisition of HSI data (16 channels in the range 470 -630 nm and a thermal camera for skin temperature measurements. A built-in powerful mini-computer operated by custom-developed software (based on integrated di�use light-skin transport model) estimates the skin mottling parameters for sepsis diagnostics in real time. To validate the system, in-vivo data using vascular occlusion on healthy subjects were collected, and maps of skin oxygen saturation and temperature distribution constructed. Reference: U. Rubins et. al. , «Multimodal device for real-time monitoring of skin oxygen saturation and microcirculation function» , Biosensors, 9, 97 (2019). ERDF project «Multimodal imaging technology for in-vivo diagnostics of skin malformations» This inter-disciplinary (optics + medicine) project relates to biophotonics and aims at further development and multimodal merging of three innovative skin imaging technologies: (i) multispectral diffuse reflectance imaging, (ii) autofluorescence lifetime imaging; (iii) Raman spectral band imaging. After processing, the three kinds of images provide clinically significant distribution maps of the main skin chromophores (absorbing pigments), the emitting skin fluorophores and specific bio-molecules on the skin surface and superficial layers. The main objective is to develop and clinically validate a new triple-image diagnostic technology (implemented in a demonstrator set-up) where the same skin malformation is examined by mapping the above-mentioned three skin ingredients, with further possibility to compare and manipulate the obtained images for gaining more detailed information about the molecular structure of the malformation. The proposed multimodal imaging technology will considerably improve the sensitivity/specificity and reliability of in-vivo skin diagnostics; it will also facilitate early identification of various skin pathologies, including skin cancers. On the other hand, it will help to reduce unnecessary surgeries of misdiagnosed suspected skin malignancies. In result, improved public health care as a societal benefit will be ensured. • • The expected main results include: Compact portable prototype of diagnostic device for measurements of skin fluorescence lifetimes (FLT), TRL=4 Novel optical fibre probe prototype for bi-modal measurements and imaging of FLT and Raman spectral bands, TRL=4 Updated laser mirror scanner equipment and software Advanced algorithms for non-contact skin chromophore mapping (with respect to directly measured diffusely reflected photon travel times in skin) and skin fluorophore mapping; New experimental set-up for Raman imaging spectroscopy of in-vivo skin Tri-modal skin imaging demonstrator set-up Database with three kinds of clinical images (multispectral, FLT, Raman) and parametric maps of vascular and pigmented skin malformations, including skin cancers. ACKNOWLEDGEMENTS Financial support from European Regional Development fund ( project #1. 1/18/A/132 Multimodal imaging technology for in-vivo diagnostics of skin malformations) is highly appreciated.