Correlation between near infrared spectroscopy and electrical techniques in measuring skin moisture content

By: Mastura Mohamad

Supervisor: Prof. Dr. Mohd Zubir Mat JafriCo-Supervisor: Dr. Ahmad Fairuz Omar

School of PhysicsUniversiti Sains Malaysia

11800 USM, Penang, MalaysiaTel : 604-6533888 Fax : 604-6579150

Motivation of Study

Background of Study

Conclusion

Instrumentation & Experimental Methodology

Result & Discussion

Research Contribution

OUTLINE

MOTIVATION OF STUDY

•Moisture in skin plays an important role to keep skin soft and supple as well as maintaining healthy skin. •A healthy skin has water in stratum corneum (SC) normally around 20% .•Much attention has been paid in evaluating the water content of the SC over the last decade.•The bioengineering provides a non-invasive technique to measure moisture content of skin in vivo with the most popular technique based on measuring electrical properties on skin surface. However, this technique has some limitation.

•Nowadays, NIR spectroscopy technique serves as an important tool for the measurement of moisture content of skin owing to the advantages it has over the other techniques. •The aim of this study to develop a correlation between NIR spectroscopy (NIRQuest) with conventional electrical technique (Dermalab Moisture Module and Scalar Moisture Checker) for skin moisture measurement.

BACKGROUND OF STUDY

What is Skin?Skin is the largest organ of the human body and make up approximately 16% of total body weight.

Skin Layer : Epidermis Dermis Subcutaneous Tissue

Major role : To prevent loss of water and

regulates body temperature by blood flow & evaporation of sweat.

Act as physical barrier to the hostile external environment.

• The epidermis-outer layer of skin.

• The epidermis contains of 5 layers:

Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale

• Stratum corneum (SC) - Outermost layer, thickness 10-20 µm

• The SC functions: Maintaining life - water holding

capacity and lipid content. As a barrier to water loss and

keep skin surface smooth and soft by binding the water

Dry atmosphere - act as a skin barrier to protect the underlying hydrated living skin tissue from desiccation.

Normal skin - water content about 10-20 % near the SC surface.

• The water content of SC is an important physiological parameter indicating skin condition.

Xerosis (Dry skin)

Electrical Technique• The most popular technique to

determine water content of skin is based on measuring electrical properties such as capacitance and alternating current conductivity on the skin surface (Arimoto et. al, 2005).

• Probes have two electrodes of various designs and when it is applied to the skin, the instruments are used to record the value of capacitance or conductance correlate directly with the water content of the skin.

Dermalab (Cortex Technology)

Corneometer (Courage & Khazaka)

NIR Spectroscopy

What is the special about the waves NIR ranges?• NIR light is absorbed by the molecules containing C-

H, O-H and N-H groups.• O-H bands of water are very intensive which exhibit

five absorption maxima at 760, 970, 1190, 1450, 1900 nm (Reich, 2005).

NIR range: 750 -2500 nm

• Electromagnetic spectrum

The stability in changes of temperature

and RH

High in accuracy and

precision

Non occlusive

High sensitivity to

hydrogen bonding

Fast data collection (0.1 s per single spectrum) - with single spectrum allow several parameter determined simultaneously

ADVANTAGES OF NIR SPECTROSCOPY FOR SKIN MOISTURE MEASUREMENT

INSTRUMENTATION AND EXPERIMENTAL METHODOLOGY

Skin Analysis System

•Based on measuring capacitance of SC • Accurate correlation with actual moisture content• Measurement: ranging from 0 to 99.9 %•Unit : percentage (%).

Scalar Moisture Checker MY-808S (Scalar Corporation, Japan)

•Electrical conductance based device •Operating at single frequency 100 kHz• Measurement: ranging from 0-1999 μS •Unit : microSiemens (μS)

DermaLab Moisture Module (Cortex Technology, Hadsund, Denmark)

Reading of Measurement

Moisture Probe

NIRQuest (Ocean Optics)

• High sensitivity optical bench and low noise and dark current.

• Wavelength range: 900nm – 2500nm

• Detector : high performance InGaAs array detector

NIR Spectroscopy Instruments• Light source :

HL-2000 tungsten halogen lamp (wavelength region 360-2500 nm)

• Reflectance probe: R600-7-VIS-125F (wavelength 400-2500 nm)

Human Subjects

10 healthy volunteers (male &

female )

Age : 21- 25 years

Area: Left&right (palm, uppear

arm,forearm,cheek) & forehead

Subject-acclimatized at least 20 minutes in a

temperature-controlled room

Approved by The Human Research Ethics

Committee, USM

Skin self evaluation

Non invasive measurement of skin hydration using NIR spectrometer and

Electrical instruments

Analysis: Minitab 16 Statistical and Unscrambler X 10.3 (trial version) software

For each measurement, a 2 cm x 2 cm test site was applied with three replicated measurements

Methodology

Skin Moisture Measurement Methodology

Measurement techniques of moisture content of skin using conventional electrical instruments.

Experimental setup for skin moisture measurement using NIR spectroscopy technique.

Temperature and humidity sensor

NIRQuest spectrometer

Tungsten halogen lamp

White reference

Fiber optic probe

RESULT AND DISCUSSION

900 1100 1300 1500 1700 1900 2100 2300 25000

10

20

30

40

50

60

70

80

Cheek L

Palm R

Palm L

Forearm R

Forearm L

Upper arm R

Upper arm L

Forehead

Cheek R

Wavelength (nm)

Ref

lect

ance

(%)

Reflectance Spectra of nine different parts of hand and face using NIRQuest spectrometer (Ocean Optics)

1900 nm1450 nm

1190 nm

970 nm

Summary of the experimental results conducted on a skin sample of 10 subjects using a combination of four selected wavelengths (950-970 nm, 1100-1900 nm, 1400-1450 nm and 1870-1900 nm).

SubjectsCoefficient of determination, R2 (%)

NIRQuest &Dermalab

NIRQuest & Moisture Checker

1 77.2 80.1

2 70.9 58.8

3 95.2 56.3

4 96.5 94.4

5 91.7 81.6

6 95.0 51.6

7 81.5 67.3

8 97.9 74.5

9 93.4 90.3

10 88.3 74.1

Average 88.8 72.9

• From the experimental data summarized in the table, moisture content of skin determined by NIR spectroscopy technique correlated well with the electrical conventional techniques with the R2 values range from 70.9 to 97.9 % (average of 88.8 %) between NIRQuest and Dermalab moisture probe.

• Least accuracy has been observed for the correlation between NIRQuest and Moisture Checker with the R2 values ranges from 51.6 to 94.4 % (average of 72.9 %).

The scatter plot graph for the best correlation obtained between the value of (a) NIRQuest &Dermalab (b) NIRQuest & Moisture Checker

a b

25020015010050

250

200

150

100

50

Actual Moisture

Calc

ula

ted M

ois

ture

R2 =97.9 % R2 =94.4 %

CONCLUSION

• A skin-self evaluation questionnaire was conducted and a non invasive measurement were performed on the left and right of the palm, forearm, upper arm and cheek also on the forehead.

• The four ranges of wavelengths 950-990 nm, 1110-1190 nm, 1400-1450 nm and 1870-1900 nm were identified to be strongly dominated by the absorption of water and have contributed very well in the development of correlation between spectroscopic and conventional electrical technique.

RESEARCH CONTRIBUTION

• A correlation of spectroscopic techniques was successfully developed for quantifying moisture content of human skin.

• From the analysis of the entire research confirmed the ability of spectroscopic technique for practically used in quantifying moisture content of human skin.

• Therefore, can help to establish novel specialized optical system for rapid and non-occlusive measurement in clinical used especially in the dermatology field.

THANK YOU FOR LISTENING

School of PhysicsUniversiti Sains Malaysia