Janis Spigulis, Vanesa Lukinsone, Martins Osis and Ilze Oshina Applications of cw and pulsed lasers for in-vivo skin diagnostics: some recent results Janis Spigulis, Vanesa Lukinsone, Martins Osis and Ilze Oshina SFM-2018, 24/09/2018

Biophotonics lab in Riga: our profile Aim – to develop affordable for end-users methods, devices and technologies for clinical diagnostics and monitoring, by exploiting optical features of in-vivo skin: - Skin autofluorescence (AF): photo-bleaching (AFPB) effects, skin “photo-memory” parametric AFPB rate imaging  diagnostic potential studies Skin diffuse reflectance spectroscopy (DRS): fibre-optic contact probe DRS, multi-spectral imaging  skin chromophore mapping  potential for distant skin assessment Skin blood pulsations (photoplethysmography, PPG) bilateral, multi-site and multi-spectral PPG distant (wireless and non-contact) PPG  clinical applications

Skin malformations MALIGNANT BENIGN Melanoma Nevi Basal cell carcinoma Seborrheic keratosis Squamous cell carcinoma Hemangioma

Motivation for better skin assessment Clinical need for a non-invasive, patient-friendly and informative devices for skin diagnostics; Drawbacks of currently available devices: Low sensitivity; Insufficient reliability; Bulky design, cable/PC; Mainly use skin color images  parametric images are helpful (e.g. chromophore maps, specific index-maps); Expensive. Siascope DermaLite MelaFind

Seborrheic keratosis (SK): AF signature! Every 4th misdiagnosed melanoma appeared to be SK. cw 405nm LED excitation  smartphone camera G-band AF intensity images for a number of skin malformations AF intensity of SK - always higher than that of healthy skin; nevi, BCC and MM - lower A.Lihachev et al., “Differentiation of seborrheic keratosis from basal cell carcinoma, nevi and melanoma by RGB autofluorescence imaging”, Biomed.Opt.Expr., 9(4), 1852-1858 (2018).

AF kinetics studies: ps measurement setup

Skin AF under 405nm laser excitation: 3 lifetime components,photobleaching effect I.Ferulova, A.Lihachev, J.Spigulis, “Photobleaching effects on in-vivo skin autofluorescence lifetime”, J.Biomed.Opt., 20(5), 051031 (2015).

Skin AF lifetime images: photobleaching effects V.Lukinsone, “In-vivo skin autofluorescence kinetics at continuous and pulsed laser excitation”, PhD Theses, Riga, 2017.

Problem: skin-remitted photon path length. Monte-Carlo simulations (A Problem: skin-remitted photon path length. Monte-Carlo simulations (A.Bykov) I(x) I(x) I Diffuse reflectance absorption: Slab absorption, I(x) = I exp(-kx) x x  f(x) ! J.Spigulis, I.Oshina, A.Berzina, A.Bykov, “Smartphone snapshot mapping of skin chromophores under triple-wavelength laser illumination”, J.Biomed.Opt., 22(9), 091508 (2017).

Can it be measured directly?  

Setup for skin diffuse reflectance kinetics Differences from the fluorescence setup – the same (input) wavelengths detected; «white» ps laser used, spectral bands selected by a set of interference filters; special fibre holder designed

Skin input and remitted pulse shapes, 650 nm   Left forearm of a single volunteer

Input-output pulse peak delay Left forearms of 8 volunteers, averaged values

Output-input pulse half-width difference Left forearms of 8 volunteers, averaged values

Pulse peak delays: spectral dependence Left forearms of 8 volunteers, averaged values

Differences of pulse half-widths: spectral dependences Left forearms of 8 volunteers, averaged values; «jump» around 600nm observed only at 8 mm Inter-fibre distance, unsufficient S/N at longer distances for 550nm and 600nm

Calculated path length of the “first” skin-remitted photons as a function of wavelength at inter-fibre distance 8mm (n=1.36, single volunteer) s = t . c/n

Multi-monochromatic spectral imaging We can extract 3 monochromatic spectral images from a single-snapshot RGB image data, if object (skin) is illuminated simultaneously by 3 laser lines and the RGB-band sensitivities of the image sensor are known Next step – conversion of 3 monochromatic spectral images into distribution maps of 3 main skin chromophores

Smartphone add-on triple wavelength laser illuminator: 450nm, 532nm, 659nm Method and device for smartphone mapping of tissue compounds. WO 2017/012675 A1, 2017.

RGB image (a) and maps of chromophore content changes for 3 vascular hemangiomas: b – oxy-hemoglobin, c – deoxy-hemoglobin, d – melanin Spigulis J., et al. Smartphone snapshot mapping of skin chromophores under triple-wavelength laser illumination. J.Biomed.Opt., 2017, 22(9): 091508.

Under development Double-snapshot RGB imaging technique, each snapshot under different 3l-combined illumination  enables mapping up to 6 skin chromophores (patented) Quality improvement of the monochromatic spectral images by laser speckle removal (patented) First switchable 4l and 5l laser illuminator prototypes created  Monochromatic spectral imaging for counterfeit detection (forensics) LV 15106 B (2016). Method and device for mapping of chromophores under illumination by several laser lines (J.Spigulis. I.Oshina).

Smartphone forensics: Spectral line ratio images (A – authentic, C – counterfeit) RGB 659/448nm 448/532nm

SUMMARY Two biophotonic technologies for improved in-vivo diagnostics of skin malformations have been proposed, experimentally studied and validated in clinical measurements: Kinetic analysis of skin AF lifetimes and diffuse reflectance under ps-laser pulsed irradiation; Snapshot mapping of the main skin chromophores under triple-wavelength laser illumination. Clinical measurements  promising potential for future implementation in clinical praxis We are open for further international collaboration

janispi@latnet.lv www.lanet.lv/~spigulis Thank You!