1. 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

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. Skin malformations MALIGNANT BENIGN 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), (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), (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
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), (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 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

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/ A1, 2017.

20. 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):

21. 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 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)
RGB
659/448nm
448/532nm

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!