Applications of cw and pulsed lasers for in-vivo skin diagnostics: some recent results

1. 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

2. 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

3. Skinmalformations BENIGN MALIGNANT Melanoma Nevi Basal cell carcinoma Seborrheic keratosis Squamous cell carcinoma Hemangioma

4. 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

5. 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).

6. AF kinetics studies: ps measurement setup

7. 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).

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

9. Problem: skin-remitted photon path length.Monte-Carlo simulations (A.Bykov) I(x) I(x) Diffuse reflectance absorption: I 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).

10. Can it be measured directly?

11. 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

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

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

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

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

16. 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

17. Calculated pathlength 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

18. 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

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

20. RGB image (a) and maps of chromophore content changes for 3vascular 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.

21. Underdevelopment • Double-snapshot RGB imaging technique, each snapshot under different 3l-combined illumination enables mapping up to 6 skin chromophores (patented) • Qualityimprovementofthemonochromaticspectralimagesbylaserspeckleremoval(patented) • First switchable4l and 5l laserilluminatorprototypescreated • 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).

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

23. 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

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