Optical Technology for Ultraviolet Erythema Assessment and

Minimal Erythema Dose Determination in Healthy Volunteers

Mikhail Makmatov-Rys

, Alexey Glazkov

, Irina Raznitsyna

, Dmitriy Kulikov

1,3

Anton Molochkov

, Albina Khlebnikova

, Ekaterina Kaznacheeva

, Alexey Sekirin

and Dmitry Rogatkin

Moscow Regional Research and Clinical Institute "MONIKI", 61/2,

Shchepkina Str., Moscow, RF, 129110, Russian Federation

Cosmetological Clinic «Lemark», Voronezh, 32 Vladimir Nevsky Str., RF, 394088, Russian Federation

Institute of Public Health named after N.A. Semashko,

12/1c1 Vorontsovo Pole Str., Moscow, RF, 105064, Russian Federation

Keywords: Ultraviolet Erythema, Minimal Erythema Dose, Inflammation, Fluorescence, Saturation, Non-invasive,

Diagnostics.

Abstract: Currently, in clinical practice, the assessment of ultraviolet (UV) -induced erythema and the determination

of the minimal erythema dose (MED) is done visually, which is subjective, inaccurate and associated with

high variability of the results. To solve this problem, the application of optical methods seems promising,

allowing us to evaluate changes in epidermis and dermis induced by UV exposure. In this study the analysis

of endogenous fluorescence and microcirculation characteristics by non-invasive optical methods revealed

the relationship between the intensity of endogenous fluorescence of porphyrins and oxygen consumption

with a dose of UV radiation. The correlation of the intensity of endogenous fluorescence of the irradiated

region normalized to intact tissue with a dose of UV was demonstrated. Therefore, optical diagnostic methods

can be a promising tool for non-invasive and quantitative assessment of UV erythema and MED.

1 INTRODUCTION

The assessment of skin reaction on different doses of

ultraviolet radiation (UVR) with different

wavelengths is one of the challenging issues of

modern photobiology and medicine. Currently, the

traditional method of assessing the degree of

exposure to UV radiation in humans and animals is

based on the calculation of the minimal erythema

dose. Minimal erythema dose (MED) is an amount of

UV exposure leading to the development of

minimally perceptible erythema on untanned skin

within 24 hours after irradiation (Heckman et al.,

2013). Thus, determination of MED is based on

assessment the charactheristics of the

pathophysiologic phenomenon - UV-erthema

(Makmatov-Rys et al., 2019). MED is usually

measured in mJ/cm

. MED is widely used in clinical

practice and experiments in the evaluation of

photosensitivity. It is applied to determine the UVA

and UVB starting doses in the phototherapy of skin

diseases (Krutmann et al., 2008). Moreover, MED

assessment is one of the diagnostic methods for some

photodermatoses (Hönigsmann, 2008).

MED is traditionally determined visually by

naked eye, which is a subjective and inaccurate

method (Lock‐Andersen et al., 1996). For instance,

Falk M. and Ilias M. showed that the agreement

between observers on the characteristics of UV

erythema, was excellent for skin redness with a sharp

border, but for reactions with a diffuse or indistinct

border there was a substantial inter-observer

variability. Mistakes can occur during the visual

assessment of the Fitzpatrick skin type especially in

tanned patients or in dark skin when the evaluation is

made by untrained doctor (Falk et al., 2008).

Incorrect determination of MED can lead to an

overestimation of the dose of UV radiation in the

starting point of phototherapy course and to such

complications as burns, hyperpigmentation, dry skin,

herpes simplex reactivation, and in some cases to

aggravation of the underlying skin disease. In

addition, the occurrence of such complications leads

to an interruption in the phototherapy course, an

Makmatov-Rys, M., Glazkov, A., Raznitsyna, I., Kulikov, D., Molochkov, A., Khlebnikova, A., Kaznacheeva, E., Sekirin, A. and Rogatkin, D.

Optical Technology for Ultraviolet Erythema Assessment and Minimal Erythema Dose Determination in Healthy Volunteers.

DOI: 10.5220/0009177000730078

In Proceedings of the 13th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2020) - Volume 1: BIODEVICES, pages 73-78

ISBN: 978-989-758-398-8; ISSN: 2184-4305

increase in the numer of clinic visits and the

associated economic costs. In the long term, the risk

of malignant skin neoplasms and photoaging

increases.

To avoid the limitations of conventional methods

for MED assessment additional instrumental

methods, in particular optical, are used.

There are data in the literature on the use of the

following optical methods for assessing erythema

intensity and MED: reflective spectroscopy

(Bodekær et al., 2013), colorimetry (Jeon et al.,

2014), laser doppler flowmetry (Falk et al. 2008),

laser doppler visualization (Wilhelm et al., 2001), and

confocal microscopy (Yamashita et al., 2007).

Despite the progress in the field of the objective

assessment of UV erythema and MED, the

abovementioned methods have some limitations.

Current studies are trying to find a correlation

between objective optical metrics and subjective

visual characteristics of erythema, such as color,

distinctness of borders, contours. Unfortunately, the

examination of pathophysiological mechanisms of

severe UV-induced tissue damage is beyond the

scope of these studies.

Meanwhile, laser fluorescence spectroscopy

(LFS) has potential applications in this field.

Fluorophores responsible for inflammation and

hypoxia which play a role in UV-induced skin

damage, could be detected by LFS in red and green

spectrum range (Franco et al., 2016). The literature

describes the use of laser fluorescence spectroscopy

in vivo in experimental models for assessment local

inflammation (Petritskaya et al., 2015), radiation skin

damage (Raznitsyna et al., 2018) and the skin fibrosis

(Chursinova et al., 2019). There are studies on the use

of fluorescence spectroscopy to assess structural skin

changes during chronic UV damage (Tian et al.,

2001). Papazoglou E. et al. (2010) compared the data

of LFS, skin morphology and expression of matrix

metalloproteinase 13 (MMP-13) to assess changes

caused by prolonged exposure to UVB radiation on

the skin of hairless mice. The authors found that LFS

can be used to estimate epidermal thickness and

fluorescence parameters correlates with tryptophan

expression and cell proliferation and may indicate the

presence of “burn cells” in the epidermis (Papazoglou

et al., 2010)

The aim of this study was to assess the

applicability of complex optical technologies

including LFS and optical tissue oximetry in the

assessment of ultraviolet-induced skin damage and

MED at different time periods after UV irradiation

2 MATERIALS AND METHODS

The study was conducted on a group of healthy

volunteers (n = 14, 8 male and 6 female) aged 26 ± 3

years with Fitzpatrick skin phototypes II and III. In

all participants traditional MED assessment method

(described by Heckman et al. (2013)) was perfomed

on the skin of the upper back or on the skin of the

abdomen. UVB irradiation was performed using a Dr.

Honle Dermalight 500-1 series (manufactured by Dr.

Honle Medical Technology GmbH, Germany),

equipped with Phillips UV-B Narrowband PL lamps

with a wavelength of 311 nm. The Daavlin DosePatch

hypoallergenic plate with six square windows (a

square size of 1ⅹ1 cm

) was attached to the skin of the

back or abdomen, the distance to the UV source was

30 cm. The UV intensity was measured using a

Waldmann Variocontrol spectroradiometer (UV

meter). The dose of UV radiation from cell to cell

increased stepwise depending on the phototype of the

skin of the subject according to reference tables

(Palmer et al., 2005). The skin in the windows was

cumulatively exposed to UV radiation in the range

from 100 to 770 mJ/cm

. 24 hours after UV-B

exposure, the participants in the experiment were

conducted a subjective visual assessment of erythema

by 2 observers. The erythema reaction was graded

using a visual rating scale (Faurschou, et al., 2009).

Based on the results of the visual examination, the site

corresponding to the MED (barely noticeable

erythema) was determined and the dose of UVB was

calculated. Detailed characteristics of MED and

phototype participants are presented in table 1.

Before UVB irradiation and after 0.5, 3, 6, 24

hours after it, on the skin in each of 6 square windows

and on the contralateral area of intact skin (1 cm2),

the endogenous fluorescence of porphyrins was

evaluated by LFS and local blood flow characteristics

was measured by optical tissue oximetry (OTO)

implemented in the LAKK-M system (SPE 'LAZMA'

Ltd, Russia), as described in (Chursinova et al.,

2019).

The diagnostic system scheme is shown in Figure

2. The choice of the abovementioned time points was

based on an analysis of the literature on the

pathogenesis of the of acute UV damage (Hruza et al.,

1993). The process of measuring of optical

parameters is presented in Figure 1.

BIODEVICES 2020 - 13th International Conference on Biomedical Electronics and Devices

Figure 1: Process of optical measurements of the abdomen

skin after irradiation with ultraviolet B.

Figure 2: Scheme of the diagnostic system.

As a rule, the maximum absorption of most

endogenous fluorophores is observed in the UV

wavelength range. However, the radiation of this

range has a low penetrating power (less then 0.1 mm

(Mustafa et al., 2013) as distinct from the visible part

of the spectrum. Therefore, the spectra of secondary

radiation (backscattered and fluorescence) were

recorded from each region of interest after its

irradiation by low-power laser sources with

wavelengths λ

= 635 nm and λ

= 535 nm.

Porphyrin is characterized by a two-hump

fluorescence spectrum with maxima at wavelengths

of 625–630 and 700-710 nm (Croce et al., 2014). In

the wavelength range of 650 - 750 nm, porphyrins

make the main contribution to the endogenous

fluorescence of biological tissue, but at a wavelength

of 625–630 nm fluorescence of porphyrins is more

pronounced.

The fluorescence intensities I

of porphyrins were

estimated at wavelengths λ

= 710 to verify theirs

presence and at λ

= 630 nm to quantitative

assessment, respectively. Despite the fact that other

fluorophores (for example, lipofuscin) can also

fluoresce in the range of 625–630 nm, their

contribution to the total intensity insignificant.

To exclude the variability of the initial

endogenous fluorescence of volunteers’ skin, the

fluorescence intensity was normalized to the intact

region μ(λ

μ(λ

) = I(λ

)/ I

(λ

) (1)

where I(λ

) is the fluorescence intensity from the

iradiated area, I

(λ

) is the fluorescence intensity from

the intact area.

To evaluate the parameters of local blood flow,

blood filling volume (V

) and tissue oxyhemoglobin

saturation (S

) were recorded for each region of

interest for 20 seconds. Then, according to the time-

averaged data the specific oxygen consumption of the

tissues U characterized by the oxygen intake per

tissue blood flow volume unit was calculated with the

use of the following formula (Rogatkin et al., 2013):

U= (S

- S

)/ V

(2)

In this formula S

is the functional pulse

saturation of the oxyhaemoglobin fraction in the

arterial peripheral blood. It was assumed equal to

98%.

In the intact skin area, a melanin index (MI) was

measured for each participant using a

spectrophotometric instrument. «Spectrotest» (SPE

‘Cyclone-Test’ Ltd, Russia) (Afanasyev et al., 2007).

Results of measurements are showed in Table 1.

Table 1: Characteristics of volunteers enrolled in the study.

N Phototype MI

MED,

mJ/cm2

Site of

MED

assessment

1 3 0.0524 280 abdomen

2 3 0.0566 400 upper bac

3 2 0.0445 280 upper bac

4 2 0.0501 200 abdomen

5 3 - 470 abdomen

6 2 0.0501 280 u

er bac

7 3 0.0560 750 u

er bac

8 2 0.0544 560 upper bac

9 3 0.0574 380 upper bac

10 3 0.0693 750 u

er bac

11 3 0.0693 770 u

er bac

12 2 - 280 u

er bac

13 3 - 380 upper bac

14 3 - 380 abdomen

Statistical analysis was performed in Microsoft

Excel 2016 and Statistica 12 (Statsoft inc., USA). The

analysis of dynamic changes in the optical parameters

described above was carried out using the Wilcoxon

Optical Technology for Ultraviolet Erythema Assessment and Minimal Erythema Dose Determination in Healthy Volunteers

test. The relationship between the obtained optical

data and the dose of UV radiation was evaluated using

the Spearman rank correlation coefficient. The

probability of an error of the first kind was considered

statistically significant to be less than 5% (p <0.05).

3 RESULTS AND DISCUSSION

Examples of measured fluorescence spectra from the

intact (non-irradiated) and irradiated skin sites at λ

630 nm after 24 hours after the UV-irradiation is

shown in the Figure 3.

Figure 3: The example of the fluorescence spectra in intact

and irradiated skin after 24 hours after UVB exposure; λe =

630 nm.

Using Spearman's rank correlation coefficient,

positive correlation relationships were revealed

between the cumulative dose of UV and the specific

oxygen consumption of the tissues (U) normalized to

intact skin after 3 hours (correlation coefficient [r] =

0.297; p = 0.01) and 24 hours (r = 0.307; p = 0.0004)

after the irradiation. In addition, a positive correlation

was found between the total UV dose and the

fluorescence intensity of porphyrins λ

= 630 nm 6

hours after UV irradiation normalized to intact skin (r

= 0.249, p = 0.01).

The findings may reflect the course of acute UV-

induced skin damage. Thus, the U index reflects an

increase in the metabolic activity of skin cells

susceptible to acute UV damage. Under the influence

of UV, mast cell degranulation, vascular endothelial

damage, vasoditalation are observed, vasoactive

substances are released - histamine, nitric oxide,

arachidonic acid derivatives, which also contribute to

the formation of infiltrate from immune cells in the

affected area (Clydesdale et al., 2001). Logan and

colleagues showed that one consequence of UV

exposure of the skin is damage to epidermal cells

which becomes evident as early as 2 hours after UV

irradiation (Logan & Wilhelm, 1963). One study

showed that peak infiltration of leucocytes after UVB

irradiation occurs at 4-6 hours and the response

concludes after 48 hours (Logan & Wilhelm, 1966).

It has also been shown that with increasing intensity

and dose of UV radiation, skin damage becomes more

pronounced (Hruza, 1993)

In addition, according to the results of the study,

it was found that normalized fluorescence intensity

and tissue content index in all irradiated skin sites

regularly changed stepwise over time. The most

significant increase in the intensity of fluorescence of

porphyrins in green light (λ

= 630 nm), normalized

to intact skin in all 6 cells was observed 24 hours

compared with 0,5 hours after UV exposure (Figure

4).

These results allow us to hypothesize that UV

exposure affects the metabolism and accumulation of

porphyrins in the skin.

Figure 4: The dynamics of the porphyrin's intensity

normalized to intact tissue in skin sites irradiated with

stepwise increasing doses of UVB (6 – lowest dose, 1 –

highest dose) in 4 time points after UV-exposure; λe = 630

nm.

Additionally, using Spearman's rank correlation

coefficient, it was found that the MED of volunteers

correlated with Fitzpatrick's skin phototype (r = 0.56;

p= 0.036), the melanin index (MI) showed correlation

with the skin phototype (r = 0.79; p= 0.007). This

results corresponds with previously to published data:

for instance, D.L. Damian and colleges in their study

showed good correlation between MI, Fitzpatrick

phototype and MED in 60 healthy volunteers

(Damian et al 1997).

It is important to mention that our work have some

limitations. We didn’t include subjects with darker

skin phototypes (IV-VI) in study population. It is

known that melanin content is significantly higher in

the skin of subjects with darker skin type (Lu et al.,

1996).

BIODEVICES 2020 - 13th International Conference on Biomedical Electronics and Devices

Melanin is known to absorb the radiation of the

visible spectrum, which reduces the registered signal

significantly. In these cases increasing the power of

the laser radiation may increase the signal-to-noise

ratio and solve the problem. But in further studies it

is important to estimate the minimum laser power for

skin phototypes IV-VI at which peaks of endogenous

fluorophores can be distinguished.

Also, since this study involved young patients of

approximately the same age, it is also necessary to

conduct the similar studies with subjects of different

age groups. Lipofuscin age pigments accumulate in

cells with age, also has fluorescent properties (Brunk

et al., 2002). Therefore, it is necessary to evaluate its

contribution to the total skin spectrum and the

possibility of reliable identification of porphyrins in

older people.

4 CONCLUSIONS

The results of this pilot study showed that the

integrated application of the LFS and OTO methods

for objective non-invasive assessment of erythema

has prospects for further investigation in larger

studies. This techniques give us opportunity to access

pathophisiological alternations (e.g. inflmmation and

vasodilatation) taking place in the skin after acute UV

damage. To gain more precise data, it is worth to

analyze optical parameters of of the skin of different

anatomical zones irradiated with UV (for example,

back and abdomen) in a larger groups of young

volunteers darker skin phototypes.

In the future, these developments may become the

basis for the development of diagnostic systems for

quantitative predictive assessment of MED.

ACKNOWLEDGEMENTS

The reported study was funded by RFBR, project

number 20-32-70134

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