A s imultaneous multimodal imaging system for tissue functional …home.ustc.edu.cn/~rwq1112/papers/SPIE-2014.pdf · 2016-08-07 · A s imultaneous multimodal imaging system for tissue

A simultaneous multimodal imaging system for tissue functional

parameters

Wenqi Ren1, Zhiwu Zhang1, Qiang Wu1, Shiwu Zhang1*, Ronald Xu1, 2 1Centers for Biomedical Engineering, University of Science and Technology of China, Hefei,

230027, China; 2Department of Biomedical Engineering, the Ohio State University, Columbus, OH

43210

ABSTRACT

Simultaneous and quantitative assessment of skin functional characteristics in different modalities will facilitate diagnosis

and therapy in many clinical applications such as wound healing. However, many existing clinical practices and

multimodal imaging systems are subjective, qualitative, sequential for multimodal data collection, and need co-registration

between different modalities. To overcome these limitations, we developed a multimodal imaging system for quantitative,

non-invasive, and simultaneous imaging of cutaneous tissue oxygenation and blood perfusion parameters. The imaging

system integrated multispectral and laser speckle imaging technologies into one experimental setup. A Labview interface

was developed for equipment control, synchronization, and image acquisition. Advanced algorithms based on a wide gap

second derivative reflectometry and laser speckle contrast analysis (LASCA) were developed for accurate reconstruction

of tissue oxygenation and blood perfusion respectively. Quantitative calibration experiments and a new style of skin-

simulating phantom were designed to verify the accuracy and reliability of the imaging system. The experimental results

were compared with a Moor tissue oxygenation and perfusion monitor. For In vivo testing, a post-occlusion reactive

hyperemia (PORH) procedure in human subject and an ongoing wound healing monitoring experiment using dorsal

skinfold chamber models were conducted to validate the usability of our system for dynamic detection of oxygenation and

perfusion parameters. In this study, we have not only setup an advanced multimodal imaging system for cutaneous tissue

oxygenation and perfusion parameters but also elucidated its potential for wound healing assessment in clinical practice.

Keywords: Simultaneous, multispectral, laser speckle, oxygenation, perfusion, phantom, nude mice, wound healing.

* Corresponding author: [email protected], tel: 86-0551- 63601482

1. INTRODUCTION

Chronic wounds are among the most common wounds in clinical medicine, which greatly reduce patients’ quality of life

and cost hundreds of billion on the treatment every year [1]. A variety of etiologic, systemic, and local factors may be

involved in the pathogenesis of a chronic wound. Normal wound healing process involves the reparative phases of

inflammation, proliferation, and remodeling [2]. Interrupting any of these phases may result in chronically unhealed

wounds, amputation, or even death. Therefore, accurate and quantitative characterization of the functional parameters at

each phase of the wound healing process will help objectively assess the clinical outcome and quantitatively guide the

therapeutic process.

Multimodal Biomedical Imaging IX, edited by Fred S. Azar, Xavier Intes, Proc. of SPIE Vol. 8937, 893706 · © 2014 SPIE · CCC code: 1605-7422/14/$18 · doi: 10.1117/12.2041008

Proc. of SPIE Vol. 8937 893706-1

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Oxygen exists in biological tissue in multiple forms, accurate assessment of wound tissue oxygenation is important for

appropriate diagnosis, prevention, and treatment of chronic wounds [3]. Recently, multispectral imaging opens a new

avenue for non-invasive and real-time assessment of tissue oxygenation. Images of the tissue at multiple wavelengths were

collected and a number of methods have been investigated to reconstruct the oxygen saturation. Besides oxygenation,

sufficient nutritive delivered by subcutaneous perfusion is also critical for wound healing process, and the blood vessel

evolution is also involved in all the three healing phases [4]. At present, as a full-field technique that produces two-

dimensional map of blood flow over an area of tissue, Laser Speckle Contrast Analysis (LASCA) based on the spatial or

temporal statistic of speckle pattern has been commonly used for clinical assessment.

The development of all imaging methods requires the use of tissue-simulating phantoms to mimic the properties of tissues.

Generally, phantoms are used for testing system designs, optimizing signal to noise in existing systems, performing routine

quality control, and comparing performance between systems [5]. In this study, a liquid blood phantom consists of fresh

blood, India ink, and intralipid was prepared for multispectral imaging of oxygen saturation. An integrated calibration

method using a Flux Standard and a moving white diffuser was developed for accurate laser speckle imaging of blood

perfusion. In addition, we designed a new kind of reusable phantom made of polydimethylsiloxane (PDMS), which could

be used to simulate the optical characteristics and blood circulation in cutaneous tissue.

Despite the progress in tissue oxygenation and perfusion measurements, no imaging tool is available yet for simultaneous

assessment of these two important parameters in a uniform field of view (FOV).In this paper, we developed a multimodal

imaging system that integrated multispectral imaging and laser speckle imaging modules, multimodal images were

acquired synchronized with corresponding light illumination switched by an electronic shutter. Tissue oxygenation and

blood perfusion were reconstructed by a wide gap second derivative reflectometry and laser speckle contrast analysis

(LASCA) algorithm respectively. Quantitative calibration experiments and skin-simulating phantoms were designed to

verify the numerical accuracy and reliability of the imaging system. In vivo, a post-occlusion reactive hyperemia (PORH)

procedure, and an ongoing wound healing process monitoring experiment using nude mice dorsal window chamber models

were conducted to demonstrate the potential of our system for wound healing assessment in clinical practice.

2. MULTIMODAL IMAGING SYSTEM

Figure 1. (A) Integrated multimodal imaging system. (B) User interface of the imaging system

A B



The multimodal imaging system integrates multispectral and laser speckle imaging technologies into one setup. The

greatest advantage of this system is the combination of the illumination and images acquisition from two different imaging

modalities, which can realize the identical field of view and simultaneous data acquisition. The components of the system

are shown in Figure 1 (A), an AOTF tunable light source (500~900nm range, 10nm bandwidth@633nm, Brimrose, US)

and a laser device (λ=785nm, 150mW, Changchun New Industries, China) are connected to a light ring via a bifurcated

optical fiber for average illumination, an electronic shutter (Daheng New Epoch Technology, Inc. Beijing, China) is fixed

on the fiber to switch the two light source periodically. The reflected intensity of tissue or phantoms will be imaged onto

a homochromous 12-bit CCD camera (Microvision Digital Imaging Technology Co.Ltd, China) with 1392×1040 pixels.

The quantum efficiency of the CCD chip is greater than 50% at a wavelength range from 400~650nm, suitable for

multispectral imaging. The light source and electronic shutter are connected to a laptop via serial port, and the camera is

connected through 1394A port. To control all the equipment and synchronize the data acquisition with modalities switching,

we developed a Labview (National Instruments, TX, US) interface as shown in figure 1(B). The program has a function

of automatic exposure in case of improper image intensity. With the integrated multimodal imaging system, the

noninvasive, simultaneous, and multimodal measurement of the tissue characteristics can be realized.

3. ALGORITHMS AND METHODS OF THE IMAGING SYSTEM

3.1. Multispectral imaging of tissue oxygenation

Reflection spectrum of a semi-infinite turbid media was simulated using a simplified numerical model [6]. In our system,

tissue oxygen saturation (StO2) was reconstructed by a wide gap second derivative reflectometry [7]. Six wavelengths (544,

552, 568, 576, 592, 600nm) were selected to calculate a Second Derivative Ratio (SDR), which is an index only corrected

to StO2 regardless of blood concentration, scattering and melanin level. SDR was calculated as:

SDR =)576(2)552()600(

)568(2)544()592(

rrr

rrr

, r (λ) =

)(

)(

s'

a

(1)

where μa is the absorption coefficient and μs is the reduced scattering coefficient. The index has a monotonous relationship

with StO2, thus one can calculate StO2 from the measurements of SDR.

The procedure of multispectral imaging for oxygenation StO2 using various wavelengths is introduced below. Firstly,

sample to be measured and a 99% reflected diffuser (The National Institute of Standards and Technology, Gaithersburg,

MD) were placed within the FOV of the CCD camera at an equal height. Then an image in totally dark environment was

captured to record the dark current noise of the CCD chip. Next, the AOTF tunable light source was controlled to illuminate

the specific wavelength beam successively, meanwhile the auto-exposure function was run to set up the optimal exposure

time t of each wavelength in case of improper intensity. After that, the monochromatic images of every wavelength will

be taken and stored at corresponding exposure time for further processing by the wide gap second derivative reflectometry

as described above. In addition, to avoid the measurement artifact caused by ambient light, it was suggested that the

experiment should be conducted in a dark environment.

3.2. Laser speckle imaging of tissue perfusion

Tissue perfusion characteristics can be acquired with Laser Speckle Contrast Analysis (LASCA) [8]. Illumination of a

tissue by monochromatic laser light will produce an interference pattern on the tissue surface. When the illuminated object



is static, the speckle pattern is stationary. However, when moving particles (such as blood cells) are present in the sampled

tissue, the speckle pattern will fluctuate over time. By analyzing these intensity fluctuations, parameter about the blood

perfusion in the tissue can be obtained.

In this system, a 785nm laser device was selected for enough depth of light transmission, images of tissue speckle pattern

were recorded by camera synchronizing with the electronic shutter switch to laser illumination. From the images data, we

can get the intensity and variance of a region of interest (ROI). To calculate the contrast from intensity – variance pairs,

the following formula should be used:

C=I

V (2)

where C is the contrast, V is the variance, I is the intensity and β is the coherence factor. The coherence factor ensures C =

1 (and thus perfusion = 0) for static objects. It is system specific and will be determined by a calibrate experiment as

described later. The perfusion is calculated from the contrast as follows:

P= )11( Ck (3)

where P is the perfusion, C the contrast and k the signal gain factor. The same as the coherence factor, the signal gain

factor will be calibrated and ensure a certain perfusion values on a flux standard.

4. PHANTOM EXPERIMENTS AND SYSTEM CALIBRATION

4.1. Blood Phantom experiment for multispectral imaging

4.1.1 Blood Phantom Fabrication and calibration methods

The StO2measurement was verified using a liquid blood phantom [9], which was prepared by mixing fresh chicken blood,

India ink (Bomei Biotechnology, Hefei, China), and 20% intralipid (Sino-Swed Pharmaceutical Corp, Ltd. China) in

phosphate buffered solution (Bomei Biotechnology, Hefei, China).Ink and intralipid were used to simulate the melanin

absorption and skin scattering respectively, and the concentration of these ingredients should be determined to ensure the

optical parameters of the phantom would match with those of in vivo tissue. In our experiments, the absorption coefficients

of the blood phantom was regulated to be 0.172 cm-1 (at 690 nm) and the reduced scattering coefficient to be 4.5 cm-1 (at

690 nm), as confirmed by an OxiplexTS tissue spectrophotometer (ISS Inc., Champaign, IL). The pH level of the phantom

was adjusted to 7.4 by adding NaOH and HCl. Finally, The oxygenation level of the phantom was adjusted by dropwise

addition of sodium hydrosulfite (0.025 g/mL, Bomei Biotechnology, Hefei, China) using an injection syringe (LSP01-1A,

Baoding Longer Precision Pump Co., Ltd, China).



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Figure 2. Schematic drawing of an experimental setup for multispectral imaging of a blood phantom.

To calibrate the multispectral imaging method, multispectral data of the blood phantom were acquired from a setup as

shown in Figure 2. The blood phantom was placed in a container full of argon gas to eliminate the measurement artifact

caused by oxygen in ambient air. During the calibration test, 11oxygenation levels ranging from nearly 100% to nearly 0%

were achieved by dropwise addition of sodium hydrosulfite at proper doses. At each oxygenation plateau, the blood

phantom was mixed to homogeneity by a magnetic stirrer, then multispectral data of each oxygenation level were acquired

and saved. At the same time, a probe of the Moor oxygenation monitor (VMS-OXY, Moor Instruments Inc., Devon, UK)

was adhered to the beaker, which recorded the actual oxygen saturation of the blood phantom during calibration procedure.

4.1.2. Experiment result

Figure 3. (A)Blood phantom StO2 measured by multispectral algorithm versus that measured by Moor oxygenation monitor.

(B)& (C) Blood phantom at full oxygenation and full deoxygenation. (D)& (E) StO2 map of blood phantom at full

oxygenation and full deoxygenation

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At each oxygenation levels of each recipe, StO2 were reconstructed from multispectral images of 544, 552, 568, 576, 592,

600nm using our algorithm as described previously. Three region of interest (ROIs) on the maps were selected to average

the StO2 values. After normalized to the scale of 0% to 100% by a linear function, the results were compared with the

actualStO2measured by Moor oxygenation monitor as plotted in Figure 3(A). According to the figure, linear correlation

can be observed between the calculated oxygenation levels and their actual values, indicating that the algorithm was able

to reconstruct tissue oxygenation. Figure 3(B) - (E) intuitively show the contrast of blood phantom at full oxygenation,

deoxygenation and corresponding StO2color maps.

4.2. Calibration experiment for laser speckle imaging

4.2.1. Calibration materials and methods

Here we introduce an integrated calibration method for accurate laser speckle imaging using a Flux Standard and a moving

white diffuser. The Flux Standard (Moor Instruments Inc., Devon, UK) was a colloidal suspension of polystyrene particles.

After shacked gently for 10 seconds and left to rest for 2 minutes, the suspension would be imaged with laser illumination.

At room temperature (25℃), the stationary background area will produce a contrast value of 1, and the Flux Standard will

produce a perfusion value of 250±5 Perfusion Units (PU). Thus, the parameters β and k described in formula (2) and (3)

can be determined. Besides, the white diffuser (The National Institute of Standards and Technology, Gaithersburg, MD)

was pushed by a motorized positioning system (TSA100, ZOLIX instruments, China) at a constant velocity to simulate

the movements of blood flow [10]. The measurements were taken over the regular velocity range from 0 to 10 mm/s, and

at each velocity plateau, 30 consecutive speckle images were acquired at 5 frames per second, then the perfusion P were

calculated by LASCA algorithm as above described.

4.2.2 Experiment result

Figure 4. Perfusion measured by LASCA versus white diffuser moving speed

Firstly, the perfusion result of a Flux Standard and static background was calculated by original LASCA algorithm. Three

ROIs were selected to average the contrast and perfusion values. According to Formula (2) and (3), to ensure C=1 for static

background and P=250±5 PU for Flux Standard, the parameters β and k were determined to be 2.00 and 21.45 respectively.

Perfusion (PU)

A

B



CCDcamera

light ring

AOTF light source

Moor oxygenation& perfusion monitor

electronic L

shutter 785nm Laserlight source

Tissue NIST traceablesimulating white diffuserphantom

Secondly, as shown in Figure 4(A), perfusion produced from the dynamic speckle on white diffuser increases with the

moving velocity linearly within a regular range of blood flow, the fitting line reveals an impressive correlation between

two parameters. Figure 4(B) shows four representative perfusion maps at different moving speeds. Combing this two

experiment results into account, the linearity and numerical accuracy of laser speckle imaging can be verified.

4.3. Test on a tissue-simulating and blood circulation phantom

4.3.1. Phantom Fabrication Protocol

In order to simulate the optical characteristics and blood circulation in cutaneous tissue, we designed a new style of solid-

state, biocompatible, permanent, and reusable phantom containing vessel-simulating channels. The phantom was

composed of polydimethylsiloxane (PDMS), Titanium dioxide powder (TiO2), and India ink. Firstly, we prepared PDMS

(Dow Corning, US) and matched hardener for matrix solidification in a ratio of 10:1 by weight. Secondly, designed dosage

of TiO2 (Guangfu Fine Chemical Research Institute, China) and India ink (Bomei Biotechnology Co., Ltd, Hefei, China)

were added into the matrix as the scattering and absorbing agents respectively. After stirred to homogeneity, the mixture

would be put in the vacuum pump for air exhaust. Then we poured the mixture into a rounded mold with a square section

vessel model at proper position and left it to harden for several hours. Finally, the vessel model was taken out when the

phantom was completely solidified. In order to check the phantom’s optical characteristics, an OxiplexTS tissue

spectrophotometer was used to confirm the absorption coefficients of PDMS phantom to be 0.122 cm-1 (at 690 nm) and

the reduced scattering coefficient to be 5.3 cm-1 (at 690 nm), the optical parameters was match with those of normal human

cutaneous tissue.

4.3.2. Experiments procedure and result

Figure 5. Schematic drawing of an experiment setup for simulating blood circulation and oxygenation adjustment

An experiment system as shown in Figure 5 was setup to simulate the blood circulation and oxygenation adjustment. Two

completely duplicate PDMS phantoms were connected in series by silicone tubes, one was used for multimodal imaging

and the other one was used to validate the imaging result via an affixed Moor oxygenation and perfusion detector (VMS-

OXY & VMS-LDF, Moor Instruments Inc., Devon, UK). To realize the simulating blood circulation in phantoms, a



Perfusion (PU) St0

peristaltic pump (BT100-2J, Baoding Longer Precision Pump Co., Ltd, China) was used to drive 250 mL blood solution

(diluted by distilled water in a ratio of 1:5 by volume) sealed in a conical flask, which could eliminate the effect of oxygen

in ambient air and weaken the intermittency of peristaltic pump. The oxygenation level of the blood was adjusted by

dropwise addition of sodium hydrosulfite (0.025g/mL) using an injection syringe through a silicone tube. At each

oxygenation plateau, the blood phantom was mixed to homogeneity by a magnetic stirrer. On the basis of this system, the

multispectral imaging and laser speckle imaging can be verified on PDMS phantom simultaneously or respectively.

Figure 6. (A)& (B) PDMS phantoms used for imaging and verification. (C)& (D) Perfusion maps of the phantom at

stationary blood flow and high blood flow. (E)& (F) Oxygenation maps of the phantom at full oxygenation and full

deoxygenation.

Figure 6(A) & (B) demonstrated the RGB images of two tissue-simulating phantoms and the probe of Moor oxygenation

and perfusion monitor. When the peristaltic pump was laid off, the simulating blood flow was static and perfusion map

showed a low level as Figure 6(C), meanwhile the Moor perfusion monitor indicated to be 5±3 PU. As a comparison,

Figure 6(D) exhibited the perfusion map of high blood flow in the vessel simulating channels, when the Moor monitor

indicated to be 100±10 PU. With regard to the oxygen saturation adjustment, StO2 maps of the phantom at full

oxygenation and full deoxygenation were shown in Figure 6(D) & (E), accordingly, the Moor oxygenation monitor

displayed as 56.7% and 0%. The elementary test results revealed the potential of this new style of phantom to verify our

multimodal imaging system.

5. IN VIVO VERIFICATION ON CUTANEOUS TISSUE

5.1. Human skin StO2 and perfusion dynamics during post-occlusive reactive hyperemia (PORH)

The multimodal imaging system of measuring StO2 and perfusion was verified on a healthy volunteer following a protocol

of post-occlusive reactive hyperemia (PORH) [11]. The subject’s hand was comfortably rested on a countertop within the

view field of the CCD camera. A Moor tissue oxygenation and perfusion detector was affixed next to the monitoring region.

The PORH process consisted of a pre-occlusive baseline period (no pressure applied to the arm) of one minute, a

suprasystolic occlusion (180 mm Hg) period of three minutes, and a reactive hyperemia period (pressure released) of two

minutes. During the PORH test, the illumination was switched from multispectral light beam to laser light beam by

electronic shutter periodically, correspondingly, multispectral images of six designated wavelengths (544, 552, 568, 576,

592, 600nm) and laser speckle images were acquired. It took about 6 to 8 seconds to finish one acquisition period. At the

meantime, Moor oxygenation and perfusion monitor recorded the dynamics of oxygenation and perfusion during the

PORH process.



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Figure 7. Comparison of the measurements results between the imaging system and Moor tissue oxygenation and laser

Doppler monitor during a PORH process

After image acquisition, tissue oxygen saturation and perfusion parameters of the monitoring region were reconstructed

by the calibrated algorithms as described previously. Three ROIs on the monitoring region were selected to even out the

possible errors. Figure 7 shows the comparison of the measurements results between multimodal imaging system and the

Moor oxygenation and perfusion monitor during the PORH process. It can be seen from the green curves that the StO2

measurement of both the imaging system and the Moor monitor matches well. The StO2 dropped during suprasystolic

occlusion period (60s ~ 240s) and shot up above the starting StO2 when the pressure on the arm was released (240s ~ 360s).

Similar trend of perfusion measurement is plotted by the blue curves, but there still existed some disparities between the

two measurements in the initial and final stages. The difference may due to two reasons. On one hand, the acquisition

period of multimodal images took about 6-8 seconds due to the responsive time of electronic shutter switching, enough

exposure time for capturing every image, and the time delay of Labview Run-Time software package. Thus, optimization

of the software and reducing the time required for illumination switch will improve the accuracy of the measurement. On

the other hand, the measurement position and depth of Moor monitor were not exactly coincide with the imaging system.

Besides, the Moor monitor maybe affected by the variation of the blood concentration, skin color and scattering properties

of the human subject.

5.2. Wound healing process monitoring using dorsal skinfold chamber models

5.2.1. Dorsal skinfold chamber model setup

Figure 8. (A) Nude mouse implanted of a dorsal skin-fold chamber; (B) a modified mice holder; (C) Dorsal skin-fold wound

chamber model with a Teflon diffuser



In this study we established in vivo mouse dorsal skin-fold chamber models in order to monitor the dynamics of

oxygenation and perfusion during cutaneous wound healing process. Four male BALB/c-nu nude mice (Vital River

Laboratory Animal Technology Co. Ltd., China) of 10 weeks old with a body weight of 23-25g were used for the

experiments. Figure 8(A) shows a nude mouse implanted of a dorsal skin-fold chamber, the fold of the depilated dorsal

skin of a mouse was taken and then fixed like a sandwich between the two titanium frames of the chamber. A full dermal

thickness wound of 2mm in diameter was made by removing the skin (including epidermis, dermis, subcutis, cutaneous

muscle, and subcutaneous fatty tissue) of one skin layer completely using a biopsy punch. A sterile coverslip was used to

close the operation filed to avoid infection or mechanical damage. To make it convenient for multimodal assessment by

imaging system, a modified mice holder was developed to fix the mouse as show in Figure 8(B). Furthermore, a calibrated

white diffuser made of Teflon was used to replace the NIST 99% reflected diffuser for multispectral imaging as shown in

Figure 8(C).The experiments were conducted in accordance with guidelines for the Care and Use of Laboratory Animals

and the Institutional Animal Care and Use Committee of University of Science and Technology of China.

5.2.2. Experiment results

Figure 9. Dynamics maps of oxygen saturation and blood perfusion of tissue in wound healing process

For the sake of monitoring the dynamic tendency of wound tissue functional characteristics during the healing process, the

sequential multimodal images were captured from the first day after biopsy to the ninth day, when the wound had

remodeled completely. Oxygen saturation and blood perfusion maps of the wound tissue areas were reconstructed and

compared. Figure 9 enumerates the representative result series of wound tissue StO2 and perfusion dynamics during the

wound healing process. Considering the StO2 series, tissue oxygen saturation at the first day indicated to be a relative low

level. However, an obvious increase was witnessed from day 2 to day 5 after biopsy. After that, the StO2subsided slowly

and reached a stable oxygen level as healing completed. Towards the perfusion, similar dynamic trend could be seen except

that the peak blood flow of wound tissue occurred later in contrast with the rising of the StO2. It could be deduced that the

initial dip in StO2 and perfusion may be attributed to the hemostasis due to biopsy. And with the growth of vessels at 3-6

days, the parameters exhibited a significant increase, the results were consistent with our current understanding of the

positive and negative regulation of angiogenesis during the different phases of wound healing [12].

Days 1 2 3 4 5 6 7 8 9

Wound

StO2

Perfusion

Proc. of SPIE Vol. 8937 893706-10


6. CONCLUSION

In this paper, we present a simultaneous and multimodal imaging system that integrates multispectral imaging module and

laser speckle imaging module. The system was capable of quasi-simultaneous and quantitative characterization of tissue

oxygenation and perfusion in the same region, which was significant to assess wound healing. To calibrate and verify the

imaging system, two quantitative calibration experiments and a new style of skin-simulating phantoms were designed,

therefore the numerical accuracy and reliability of the imaging system can be assured. In vivo, a PORH procedure test on

human hand presented commendable results comparing with a Moor oxygenation and perfusion monitor. What’s more, an

ongoing wound healing monitoring experiment using nude mice dorsal skinfold chamber models revealed the dynamic

tendency of StO2 and perfusion parameters during the healing process. All these results demonstrate the potential of the

imaging system for cutaneous tissue assessment and diagnosis in clinical practice. The future work will focus on enhancing

the accuracy and processing speed of the system and integrating structural and functional characteristics detection together.

ACKONWLEDGEMENTS

The project was partially supported by Natural Science Foundation of China (Nos. 81271527 and 81327803) and the

Fundamental Research Funds for the Central Universities (WK2090090013).

REFFERENCES

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Wound Repair and Regeneration, 17(6), 763-771 (2009).

[2] Broughton 2nd, G., Jeffrey E. Janis, and Christopher E. Attinger. "The basic science of wound healing," Plastic

and reconstructive surgery, 117(7), 12S-34S (2006).

[3] Sen, Chandan K. "Wound healing essentials: let there be oxygen," Wound Repair and Regeneration, 17(1), 1-

18(2009).

[4] Singer, Adam J., and R. A. Clark. "Cutaneous wound healing," N Engl J Med, 341(10), 738-746, (1999).

[5] Brian W. Pogue., Micheal S. Patterson., "Review of tissue simulating phantoms for optical spectroscopy, imaging

and dosimetry," J Biomed Opt, 11(4), 041102 (2006).

[6] S. Prahl, "Simple and Accurate Approximations for Reflectance from a Semi-Infinite Turbid Medium," OSA

Biomedical Topical Meetings, 613-615 (2002).

[7] D. E. Myers, L. D. Anderson, et al., "Noninvasive method for measuring local hemoglobin oxygen saturation in

tissue using wide gap second derivative near-infrared spectroscopy," J Biomed Opt, 10(3), 034017-03401718

(2005).

[8] Briers, J. D. & Webster, S. "Laser speckle contrast analysis (LASCA): a nonscanning, full-field technique for

monitoring capillary blood flow," J Biomed Opt, 1(2), 174-179 (1996).

[9] Ronald X. Xu, et al. "Developing digital tissue phantoms for hyperspectral imaging of ischemic wounds,"

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[10] Li Pengcheng, et al. "Imaging cerebral blood flow through the intact rat skull with temporal laser speckle

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[11] Arkin, H., L. X. Xu, and K. R. Holmes. "Recent developments in modeling heat transfer in blood perfused

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Proc. of SPIE Vol. 8937 893706-11


[12] Rege, Abhishek, et al. "In vivo laser speckle imaging reveals microvascular remodeling and hemodynamic

changes during wound healing angiogenesis," Angiogenesis, 15(1), 87-98 (2012).

Proc. of SPIE Vol. 8937 893706-12


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