1. HyperSpectral Skin Imaging Tianchen Shi, Prof. Charles A. DiMarzio
Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115
“This work was supported in part by CenSSIS, the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the National Science Foundation ( Award Number EEC ), “
scar
veins
Light
Source
CCD Camera
Liquid Crystal
Filter (build-in LP)
Lens
Linear
Polarizer(LP)
Subject’s
Palm
CenSISS Value Added
Current Status
Achieved fast imaging ability to obtain reasonable skin chromospheres concentrations, and oxygen saturation.
Obtained blood vessel’s general geometry information: average diameter and depth of blood vessels.
Future Plans
Extend to a spatially resolved concentration mapping.
Explore blood vessels diameter and depth distributions
Obtain better light source and detection arrays for high accuracy measurements,and increase the accuracy and stability of the information extraction procedures.
Take more in-vivo data for different skin subjects.
References
L.O.Svaasand, et.al., Lasers Med. Sci., 10: , 1995
M. Shimada, et.al., Phys. Med. Biol., 46: , 2001
R.L.P. van Veen, et.al., Opt. Lett. , 27: ,2002
Izumi Nishidate, et.al., J. Bio. Opt., 9(4): , 2004
PI Contact Information
Prof. Charles A. DiMarzio:
Northeastern University, 360 Huntington Avenue
Stearns Building 302,Boston, MA 02115
Phone : (617) , Fax: (617)
400um
100um
5000um +
Epidermis: (melanin)
Dermis:
(upper part contains hemoglobin in blood vessels)
Abstract
Chromosphere monitoring is an important aspect in most of skin studies, especially for hemoglobin in human skin, which is closely related to development and diagnosis of various skin diseases. However, recent studies reveals that hemoglobin concentration obtained by assuming homogeneous distribution may deviate from its true value. On the other hand, diameter and distribution of blood vessels in skin are also crucial in monitoring of blood pressure and body temperature. Among various optical skin imaging techniques, HyperSpectral Imaging is a fast, stable method to provide spatial and spectral information of skin tissue. In this poster, we present a Monte Carlo assisted HyperSpectral imaging method to meet both of the challenges mentioned above. Reflection spectrum measurements are used to determine absolute concentration of chromospheres with aid from a Monte Carlo model, and blood vessel information can be further derived by a correction model for the inhomogeneity in skin layers.
State of the Art
Izumi Nishidate, Muroran Institute of Technology, Japan [4]. The group used a multiple regression analysis assisted by a homogeneous Monte Carlo model to extract chromospheres concentration for point based total reflection measurement.
W. Verkruysse, Department of Radiation Oncology, University hospital Rotterdam, Rotterdam, The Netherlands [3]. The group was using a correction factor obtained by a single blood vessel assumption for a fiber based skin measurement.
Significance and Challenges
Linear multiple regression based HyperSpectral imaging may provide possibility of fast imaging over an area of skin.
Pre-computed inhomogeneous Monte Carlo model may allow to obtain general information of blood vessels at superficial skin layer.
The method may need very high accuracy and stability of the Monte Carlo model to solve the non-linear and inter dependent relationship between chromosphere concentration and obtained multiple regression coefficients.
Technical Approaches
Orthogonal polarization detection with incoherent HyperSpectral imaging for in-vivo human skin measurement.
Monte Carlo simulation for inhomogeneous layered skin model with very carefully selected parameters.
Fast 2-D imaging with linear multiple regression analysis and non- linear conversion by pre-computed Monte Carlo results. R1 R2
Overview of the Strategic Research Plan
Fundamental Science
Validating TestBEDs L1 L2 L3 R3 S1 S4 S5 S3 S2
Bio-Med
Enviro-Civil
Figure 2, Experiment Setup Layout
Figure 1, Two-layer skin model: randomly distributed blood vessels with diffusively incident photon packets.
wavelength 480nm
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wavelength 560nm
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wavelength 620nm
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wavelength 690nm
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Scar tissue
Skin Model
Modified Lambert-Beer’s Law:
where A is absorption, S is scattering term,  is molar concentration of prevailing chromospheres (melanin, hemoglobin), and L is mean free transport path length.
Monte Carlo assisted Multiple Regression Analysis:
where am is linear multiple regression coefficients, a is a vector consisting of the combination of am for the first and the third order, and b is a conversion vector nonlinearly relating Cm and am , obtained with an inhomogeneous Monte Carlo skin model.
Inhomogeneity in skin model (blood vessels) :
where D is the average diameter of blood vessels, Z is the average depth of blood vessels, bD and bZ are corresponding conversion vectors obtained from the Monte Carlo model.
Figure 3, In-vivo human skin absorption data cube
blood oxygen saturation map
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Figure 4, Extracted oxygen saturation map, average chromospheres volume concentration: melanin (4.30%), total hemoglobin(0.32%), average blood vessels diameter (101um) and depth (164um)
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wavelength (nm)
Absorption (a.u.)
measurement
Monte Carlo
Figure 5, Comparison of in-vivo spectrum and Monte Carlo simulation with extracted parameters: