This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.
Digital Object Identifier 10.1109/ACCESS.2017.DOI
A Multi-spectral Image Database for
In-vivo Hand Perfusion Evaluation
OMAR GUTIERREZ-NAVARRO1 , (Member, IEEE), LILIANA GRANADOS-CASTRO2 , ALDO R.
MEJIA-RODRIGUEZ2 , AND DANIEL U. CAMPOS-DELGADO2,3 (Senior Member, IEEE).
1
Departamento de Ingenieria Biomedica, Universidad Autonoma de Aguascalientes, Ags 20340, Mexico.
Facultad de Ciencias, Universidad Autonoma de San Luis Potosi, SLP. 78295, Mexico.
3
Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi. SLP 78210. Mexico.
2
Corresponding author: Omar Gutierrez-Navarro (e-mail: omar.gutierrezn@edu.uaa.mx).
This work was supported in part by CONACYT under grant 321899, and the Universidad Autonoma de Aguascalientes under Grant
PII22-2.
ABSTRACT The increasing prevalence of vascular diseases encourages the development of minimally
invasive approaches to assess tissue perfusion. A significant challenge facing current state-of-the-art
methods is their validation against clinical data. In this study, we introduce an open-source database designed
to evaluate tissue perfusion during the application of an occlusion protocol. The database comprises
sequences of multi-spectral images (visible and near-infrared region) from the subjects’ predominant
hand and their photoplethysmography data for validation. Our study recruited 45 healthy participants,
including 21 females, with an age range between 18-24 years old (standard deviation equal to 1.73). The
database was evaluated using two methods for estimating skin perfusion parameters based on multi-spectral
images: a Kubelka-Munk model, and a linear regression. Meanwhile, for validation purposes, the changes
in oxygenated and deoxygenated hemoglobin were evaluated by photoplethysmography data as baseline
perfusion parameters. The Pearson correlation between plethysmography-based perfusion parameters and
those extracted from multi-spectral images was evaluated in all cases as a validation metric. Our findings
demonstrated a strong Pearson correlation (ρ > 0.7) between changes in oxygenated and deoxygenated
hemoglobin and multi-spectral based perfusion parameters, suggesting that the database is useful for further
research related to in-vivo perfusion assessment. The primary objective of this database is to provide opensource data from a controlled occlusion protocol to evaluate new approaches based on multi-spectral images
in the visible and near-infrared regions. In addition, the validation by photoplethysmography data facilitates
the development and assessment of innovative tissue perfusion estimation techniques.
INDEX TERMS tissue perfusion monitoring, multi-spectral image processing, functional monitoring and
imaging, tissue oxygenation, microcirculation.
I. INTRODUCTION
HE human body runs on oxygen, nutrients and immune
factors, which are transported by the circulatory and
lymphatic systems, in a process known as tissular perfusion.
Poor blood perfusion may cause problems such as ischemia,
and additional complications may lead to organ damage or
even failure. Impaired blood flow also affects wound healing
[1], which can lead to infections in open wounds. In fact,
this scenario is critical for diabetic patients, whose blood
vessels in the lower extremities are usually affected by their
condition [2].
T
reflect the general state of perfusion throughout the body.
It is common practice to evaluate temperature, skin color,
and even perform some simple tests to assess capillary refill time by applying pressure to a fingernail [3]. Modern
methods available may require the use of contrast agents,
such as thermography, laser speckle contrast analysis [4],
and indocyanine green fluorescent imaging [5]. In some
cases, techniques such as magnetic resonance imaging [6],
computer tomography [7], laser doppler imaging [8], multispectral optoacoustic tomography [9] and surface electrode
approaches [10] can provide information about regional perfusion. There are perfusion tests available for specific organs,
At clinical level, physicians pay attention to variables that
1
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
such as myocardial perfusion imaging, cerebral oximetry,
renal scintigraphy, and hepatic vein characterization, just to
name a few [11]. Nonetheless, there is a growing interest in
the development of minimally invasive methods for perfusion
estimation in large tissue regions. Such methods aim to
characterize tissular perfusion at multiple positions up to the
microcirculatory level [12]. Non-invasive imaging tests are
generally safe, painless, and require minimal preparation.
They serve as an initial screening tool and offer valuable
information about organ function and health. However, they
may have limitations in terms of resolution and sensitivity
compared to invasive tests.
In this context, a common approach is to use imaging
techniques, either reflectance or absorbance of light, from
different portions of the spectra to measure a perfusion parameter. For instance, PulseCam [13] estimates maps of the
pulsatile component (AC) of blood flow in the skin by using
an RGB camera and reference photoplethysmography (PPG)
values. The authors in [13] test their method by applying
occlusion on healthy participants (vascular occlusion at 70
mmHg, and total occlusion at 140 mmHg) using a blood cuff
on the arm. They evaluated a total of 12 participants with
various skin tones (Fitzpatrick skin types I to V [14]).
Another approach using visible spectra is detailed in [15].
The proposed method estimates a video output corresponding
to variations in finger blood perfusion on non-caucasian subjects. Authors validate their approach by identifying ischemia
in 10 volunteers, who underwent an occlusion test. This test
lasted 10 min, 3 min without pressure, and 7 more with a
tourniquet-induced occlusion.
Spectral imaging techniques capture radiation across multiple wavelengths, they are not restricted to the visible spectrum [16]. This includes infrared, multispectral, and hyperspectral modalities. These techniques can reveal properties
not discernible with standard imaging approaches. As such,
spectral imaging can provide insight into the biochemical
composition of samples in a non-invasive manner. A primary
challenge lies in extracting meaningful information from the
large volumes of data generated through spectral imaging
[17], [18]. Originally developed for remote sensing purposes
[19], advancements in technology have enabled the proliferation of spectral imaging into diverse fields. These include
precision agriculture [20], food quality evaluation [21], and
medical applications [22] , among others. Perfusion imaging
represents one novel and promising application [23] . By
noninvasively measuring physiological information, perfusion imaging may allow for the evaluation of organ function
and disease monitoring.
The proposal in [24] employs multi-spectral imaging
(MSI) and compares their results against tissue oxygen saturation (StO2 ) from near-infrared reflectance spectroscopy
(NIRS). The authors measure local tissue desaturation and
reperfusion during two consecutive vascular occlusion tests.
However, no detailed information exists on the methodology
for estimating the MSI perfusion parameters. A total of 58
volunteers participated in this study, and the subject’s systolic
pressure was used as a control parameter. The authors induced a total occlusion by applying 30 mmHg above systolic
pressure, and then the cuff was released until oxygen saturation was below 40%, according to NIRS measurements. Pearson’s correlation was used to evaluate the level of agreement
between the MSI and NIRS perfusion parameters. According
to their results, the correlation was moderate (r = 0.42).
Other approaches are based on the combination of different
systems, such is the case of [25]. In this study, the authors
propose a laser speckle incorporated multispectral system to
estimate StO2 and a relative blood perfusion parameter. The
multispectral channels in the green portion of the spectrum
(530-570 nm) were utilized, and a model based on the Extended Beer Lambert Model was fitted using light attenuation. The authors assessed the application of this approach
for monitoring the healing progression of skin grafting in
patients with diabetic ulcers. Over a span of two years, approximately four sessions were conducted. The results were
validated by comparing the outcomes between individuals
with type II diabetes and foot ulcers, and a healthy control
group. The participants were divided into two groups: one
with positive healing and the other with impaired healing.
However, the findings related to StO2 revealed only a small
mean absolute difference in comparison to the control group.
Hyper-spectral (HS) images is another technique that can
measure reflectance data in the visible and near-infrared
(VIS-NIR) range but with more wavelength bands available.
These systems are also non-destructive, representing a great
option for biomedical applications. Such is the case of invivo tumor boundary delimitation [26]. The authors built a
database of HS images during neurosurgery procedures. They
collected 36 HS images from 22 participants. The images
were labeled by neurosurgeons to identify four classes of
tissue: normal, primary, and secondary cancer, and a fourth
class containing blood-vessels and background elements. In
[27], the authors employ a commercially available system for
clinical use that can record images with a spatial resolution of
640 × 480, and 100 spectral channels with a processing time
of around 30 seconds. However, many of these approaches
rely on prior information such as absorption and scattering
coefficients [28]. In addition, they do not actually use all the
available spectral information. The methods proposed in [29]
can estimate perfusion parameters in a clinical setting such as
StO2 , hemoglobin, and water indexes. In this research line,
the work in [30] established a key contribution, where the
authors applied two different models and their inverses to obtain perfusion parameters. They used Markov-chain [31] and
Kubelka-Munk models to estimate skin’s parameters [32].
Hence, a hyper-spectral input image was used to estimate
concentrations of melanin, blood volume, and blood-oxygen
fractions along with the depth of the skin layers.
The main problem in estimating perfusion parameters
through imaging methods is the lack of a proper validation.
In-vivo validation is challenging due to ethical considerations, variability between populations and the sample size, as
well as limited control of experimental conditions. Several
2
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
diagnostic tests that, although they may be specific, are
highly invasive, such as arterial blood gas analysis [33]. This
exam requires a blood sample, from which oxygen levels, pH,
and other information about tissue perfusion can be extracted.
These tests are the gold standard for the calibration of oximetry devices [34]. To evaluate perfusion, another option is the
application of occlusion tests to induce ischemia. These tests
consist of the temporal restriction of blood flow to an area of
interest. When applied to a limb, a simple tool such as a blood
cuff, a tourniquet, or even a rubber band can be used for blood
vessel blockage. When the pressure applied only restricts
the blood flow in the veins, it is called venous occlusion.
A total occlusion occurs when the blood circulation stops
completely. When the blockage is released, the restoration
of blood flow is called reperfusion. This condition can lead
to hyperemia, which is a rapid and exaggerated reperfusion
to the organs affected by ischemia [35]. The changes in
oxygen levels might be useful to validate reperfusion parameters. However, perfusion parameters based on pulseoximetry
might not register accurate readings during blood occlusion
[36]. In contrast, it is possible to correctly measure these
abrupt oxygen changes using NIRS or PPG readings [37]
Thus, our work introduces an open-source database for
evaluating perfusion parameters in an upper limb. The
database comprises sequences of multi-spectral images of the
hand palm and PPG data from the thumb. The latter is used
for validation purposes through the estimation of baseline
perfusion parameters (changes in oxygenated and deoxygenated hemoglobin). The data is recorded in-vivo during
the application of a occlusion protocol, inducing changes in
the dominant hand palm for approximately 10 min. for each
subject. In addition, we have conducted an initial evaluation
of the data by using two well-known regression techniques:
the Kubelka-Munk method and a linear model for monitoring
skin perfusion parameters. These methods provide valuable
insight into the data and can be used to validate perfusion
MSI-based techniques.
The rest of the manuscript is organized as follows. A description of the experimental protocol and hardware, as well
as the details of the processing algorithms and the validation
stage, are provided in Section II. The characteristics of the
database, and the results obtained to estimate hemoglobin
changes during the induced hyperemia, are described in
Section III. To conclude, the results are discussed, and the
final remarks are presented in Section IV
II. METHODOLOGY
In this section, we describe the experimental protocol used
to generate the database, as well as the hardware employed
for PPG and MSI data acquisition. We present the methodology to estimate different perfusion parameters with both
acquisition approaches. Hence, the proposed methodology is
summarized in Fig. 1.
FIGURE 1. Summary of the methodology used to capture the database,
highlighting key hardware components (MSI camera and PPG sensor). The
field of view (FOV) and position of the sensors are depicted in the top image.
The demographics of the study and an overview of the content of the database
are listed in the left-bottom. In the right-bottom, a diagram of the five-stage
occlusion protocol shows the acquisition sequence, including start time and
applied pressure for each stage.
A. EXPERIMENTAL PROTOCOL
This work aims to generate an open-source database to evaluate changes in tissue perfusion. To do so, we reproduced the
protocol from [36], to induce key changes in blood oxygen
levels. This protocol uses a blood pressure cuff to partially
occlude the blood flow in an upper limb. This protocol is
considered safe and was performed in line with the principles
of the Declaration of Helsinki. We followed the guidelines
of our institution for experiments involving human subjects
and submitted the protocol to be reviewed by the Ethics
Committee “Comité Institucional de Bioética” of the Universidad Autonoma de Aguascalientes in Mexico. The protocol
was approved with the code: CIB-UAA-37. Furthermore,
the protocol was explained to each participant, and they
were required to sign an informed consent to be included
in this study. Participants were excluded according to the
following criteria: any individual with a history of vascular
disease or chronic conditions such as diabetes mellitus and
hypertension was not eligible to participate. In addition, those
with skin infections or abnormalities were also excluded to
maintain the integrity of the study and to ensure an accurate
assessment of tissue perfusion.
3
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
Before starting the protocol, the participants were given
a minimum of 10 minutes to rest in a room set to ambient
temperature. All testing was conducted between 9:00 and
15:00 hours, ensuring consistency. Each measurement stage
was carried out in a unified laboratory setting, deliberately
isolated from sunlight. The participants were seated and
their superior limbs extended on a table. The blood pressure
cuff, as well as all sensors, were placed in their dominant
hand, which was recorded by the multi-spectral camera. A
pulseoximeter was placed on the index finger while the PPG
device on the thumb. These sensors and their cables were
covered with black pasteboard to avoid reflections on the
camera. First, the participant’s systolic and diastolic pressures were sampled. Each experiment lasted 10 min. and
the protocol was divided into five stages of two min. each
one. During the first stage, data acquisition begins and no
pressure is applied through the sphygmomanometer. The
vascular occlusion (VO) stage starts at 2:00 min., where a
fixed and constant 60 mmHg pressure is applied manually
using the blood pressure cuff. At the beginning of the rest
stage (4:00 min. mark), the pressure is released, and no
pressure is applied. The total occlusion (TO) stage starts
at 6:00 min., where pressure is constantly applied for the
whole two min. This pressure is set to 20 mmHg above the
registered systolic pressure for the participant. At the 8-min.
mark, the pressure is released at the hyperemia stage, where
the subject is allowed to rest. The experiment ends at ten min.
Photoplethysmography data is used to obtain baseline perfusion parameters. For this goal, the PPG sensor MAX30102
is used [38]. This device is a transmittance PPG sensor
that emits light using red (660 nm) and infrared (880 nm)
LEDs. The light is sampled with a photodetector with a
spectral range of sensitivity between 600 and 900 nm. The
PPG sensor was controlled using an Arduino Mega microcontroller, through the I 2 C interface. The sampling rate
was fixed to 80 Hz. The components DC and AC were
obtained according to the methodology in [39]. First, the
supply voltage interference is filtered from both, red and
infrared PPG channels. Then the signal peaks are localized
to identify each cycle in the PPG measurements. The DC
component is removed from the pulse baseline by a lowpass filter. Once the DC component is extracted from each
PPG signal, the AC component is calculated as the difference
between maximum and minimum values in a single PPG
cycle. The components AC and DC of each PPG signal are
the basis for estimating multiple perfusion parameters [40].
We estimated the ratio of absorbances defined as:
ACRed /DCRed
,
ACIR /DCIR
2
SpO2 = −45.06RP
P G + 30.354RP P G + 94.845.
(1)
where sub-index Red represents the PPG component
recorded at 660 nm, and IR represents the measurement at
880 nm. There are several models in the literature to estimate
(2)
The perfusion index measures the relationship between the
AC and DC components [41]. In this work, we employed a
definition based only on the IR measurement [40], according
to the formula:
ACIR
(3)
P IIR =
× 100 .
DCIR
Given the DC signal for each PPG channel,the light attenuation was calculated as:
DCRed (0)
,
(4)
∆ARed = ln
DCRed
DCIR (0)
∆AIR = ln
,
(5)
DCIR
where the index (0) represents the initial measurements
during the protocol. In this work, we employed the average of
the first 100 samples for each DC signal in every experiment.
Next, we employ the solution proposed by [36] to estimate
baseline perfusion parameters by the changes in oxygenated
hemoglobin ∆[HbO2 ] and deoxyhemoglobin ∆[Hb], which
were calculated as:
∆ARed εHb − ∆AIR εHb
Red
,
(6)
∆[HbO2 ] = HbO2 Hb IR
2 Hb
εRed εIR − εHbO
ε
·
d
· DP F
IR
Red
∆[Hb] =
B. PHOTOPLETHYSMOGRAPHY DATA
RP P G =
peripheral capillary oxygen saturation (SpO2 ), in this work
we used the following definition from [39]:
HbO2
2
∆AIR εHbO
Red − ∆ARed εIR
HbO2 Hb
2 Hb
εHbO
εRed · d · DP F
Red εIR − εIR
,
(7)
where the molar extinction coefficients for each molecule
HbO2 Hb HbO2
and wavelength (εHb
) were taken from
Red , εRed , εIR , εIR
[42]. As a result, these parameters were set to εHb
Red =
−1
−1 Hb
2
3.4408 M m−1 cm−1 , εHbO
=
0.3346
M
m
cm
,
εIR =
Red
−1
−1
2
=
1.2846
M
m
cm
.
0.8412 M m−1 cm−1 , and εHbO
IR
Meanwhile, parameter d in (6) and (7) represents the distance between the light emitter and the detector, while
DP F is the differential path factor. This data is not available for the MAX30102 sensor. Therefore, to estimate
the changes proportional to [absolute concentration] ×
[optical pathlenght], we followed the methodology by Abay
et al. [36], [37].
C. MULTI-SPECTRAL IMAGING DATA
In this work, we used a nine channels multi-spectral camera (SILIOS Technologies SA., France) model CMS-V1C-EVR1M-USB3. The camera measures eight wavelength
channels centered at
Λ = {558, 594, 632, 672, 714, 751, 791, 827}
nm.
(8)
The full-width half-maximum values for the camera channels
are 26, 24, 25, 25, 27, 28, 31, 34 nm. The 9th channel records
the average response from the other 8 channels. However, this
information was not employed in our study. The scene was
illuminated with a 150 W halogen light (Fiber-lite Mi-150 Illuminator Series, DolanJenner Industries, Boxborough, MA,
4
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
USA). The camera was equipped with a polarizer (PS1000
VIS/SWIR Wire Grid Linear Polarizer Film), and the raw
spatial resolution of each spectral image is 339 × 426 pixels.
The camera was set to record multi-spectral images at a rate
of 4.10 Hz with an exposure time of 16.70 ms.
At the processing stage, the images were cropped to
320 × 400. A mask was calculated to process pixel positions corresponding only to the subject’s hand. To do so,
we calculated the maximum value of the Euclidean norm
of each image along the spectral dimension, and for every
pixel with a value lower than 25%, this position was masked.
Furthermore, pixels in the boundary regions of the limb
were removed by applying morphological erosion with a disk
kernel of ratio three. The set of all available pixels in the mask
for a multi-spectral image is denoted as P ⊂ Z × Z.
A multi-spectral image at pixel position p and wavelength
channel λ is denoted as I(p, λ), where p ∈ P and λ ∈ Λ.
The reflectance at channel λ and pixel p is obtained by a
normalization step:
R(p, λ) =
I(p, λ) − ID (p, λ)
IW (p, λ) − ID (p, λ)
∀p ∈ P, λ ∈ Λ ,
(9)
where IW (p, λ) and ID (p, λ) denote the corresponding
white and dark reference images. In this work, we employed
a polytetrafluoroethylene (PTFE) plate to generate the white
reference IW (p, λ) [43]. The dark reference ID (p, λ) was
captured by taking images with the lens cap on. Some
methods to estimate perfusion parameters are based on the
absorbance, which is defined as:
A(p, λ) = − ln (R (p, λ))
(10)
∀p ∈ P, λ ∈ Λ.
for the molar extinction coefficients eHbO2 and eHb in [cm −
1/(moles/liter)] were taken from [44] at the closest values
tabulated for our wavelength channels in Λ.
The most common chromophore present in human skin
is melanin, whose spectral absorption coefficient can be
approximated by the next equation [32], [50]:
µa.mel (λ) = 6.6 × 1011 λ−3.33 [cm−1 ]
∀λ ∈ Λ.
(13)
1) Linear-Model
This model considers a minimal contribution of chromophores other than HbO2 and Hb, and it has been used
to evaluate oxygenation changes in hands occlusion [46],
tumors [48] and validated in-vivo in an animal model [45].
According to this model, the estimated absorbance of incident light ALM at channel λ is a linear combination of the
chromophores:
ALM (CHbO2 , CHb , α, λ) = CHbO2 · µa.HbO2 (λ) + CHb · µa.Hb (λ) + α ,
(14)
where (CHbO2 , CHb , α) are scaling coefficients. In this work,
we employed the absorption coefficients µa.HbO2 and µa.Hb
from eqs. (11) and (12), respectively. This model concentrates the contribution from other chromophores in the bias
term α. Given a subset of channels ΛA ⊂ Λ, we estimate the
optimal parameters (CHbO2 , CHb , α) at each pixel p ∈ P by
minimizing the following cost function:
X
2
[A(p, λ) − ALM (CHbO2 , CHb , α, λ)] ,
JLM =
λ∈ΛA
(15)
where A(p, λ) is the sampled absorbance from the multispectral camera in (10).
D. ESTIMATION OF MSI PERFUSION PARAMETERS
To demonstrate the value of the presented database, we evaluated two methods to estimate perfusion parameters based
on regression techniques and multi-spectral images. These
methods use reference spectral responses, i.e., tabulated spectral absorption coefficients measured in laboratory conditions
or approximations [28], [44]. We analyzed a linear model
based on absorbance [45]–[48], and a non-linear model [30],
[32], [49], [50] which is based on reflectance images. For
this evaluation, we quantified perfusion parameters related
to the contribution of hemoglobin in oxygenated HbO2 and
deoxygenated Hb forms using the MSI data. The results
obtained were contrasted against the baseline PPG perfusion
parameters.
The spectral absorption coefficients at λ wavelength channel were approximated [50] as:
2) Kubelka-Munk Model
µa.HbO2 (λ) = ln (10) · eHbO2 (λ) · G/M [cm−1 ]
where fmel is a free parameter. In (16), we employ the
spectral absorption of melanin µa.mel (λ) defined in (13), and
for the baseline µa.baseline (λ), we employ the definition from
[32], [50]:
−[λ − 164]
[cm−1 ].
µa.baseline (λ) = 0.244 + 85.3 exp
66.2
(17)
µa.Hb (λ) = ln (10) · eHb (λ) · G/M [cm−1 ] ,
∀λ ∈ Λ,
(11)
(12)
where G represents the weight in grams per liter, and M is the
gram molecular weight of hemoglobin. In these experiments,
we set G = 150 g/l and M = 64, 500 g/mol [50]. The values
The Kubelka-Munk model was designed to describe light
interactions in a multi-layer medium [51]. It is employed to
estimate light reflectance based on the spectral absorption
and scattering coefficients, and thickness of the materials.
When applied to human skin, these layers correspond to
the epidermis and dermis. The former contains melanin and
other minor chromophores such as bilirubin, collagen, keratin, and carotene. However, melanin is the most abundant
chromophore in the human skin, while the rest only present a
minor contribution in healthy subjects. At wavelength channel λ, the optical absorption coefficient of the epidermis layer
µa.epi (λ) is characterized as:
µa.epi (λ) = fmel · µa.mel (λ) + (1 − fmel )µa.baseline (λ),
(16)
5
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
Since the dermis contains blood vessels, this layer also
presents hemoglobin-based chromophores. At wavelength
channel λ, the dermis spectral absorption coefficient
µa.der (λ) is defined as:
µa.der (λ) =fblood · (Coxy · µa.HbO2 (λ))
fblood · (1 − Coxy ) · µa.Hb (λ)
(1 − fblood ) · µa.baseline (λ)),
+
RKM (fmel , fblood , Coxy , Ddermis , Depi , λ) = RT (λ)
+
µs.M ie (λ) = 2 × 105 × λ−1.5 ,
(19)
µs.Rayleigh (λ) = 2 × 1012 × λ−4 ,
(20)
µs.epi (λ) = µs.der (λ)
= µs.M ie (λ) + µs.Rayleigh (λ).
(21)
According to the Kubelka-Munk model, the absorbances
from eqs. (16) and (18) and the scattering coefficients from
(21) determine the amount of light moving in two opposite
directions within the skin layers. The backward flux K and
the forward flux variables β of each layer are defined as
q
Kepi (λ) = µa,epi (λ) (µa,epi (λ) + 2µs,epi (λ)) , (22)
q
µa,der (λ) (µa,der (λ) + 2µs,der (λ)) ,
(23)
βepi (λ) =
s
µa,epi (λ)
,
µa,epi (λ) + 2µs,epi (λ)
(24)
βder (λ) =
s
µa,der (λ)
.
µa,der (λ) + 2µs,der (λ)
(25)
The reflectances Repi , Rder and the light transmitted from
the epidermis to the dermis Tepi have the following expressions:
Repi (λ) =
Rder (λ) =
Tepi (λ) =
2
1 − βepi
(λ) × eKepi (λ)Depi (λ) − e−Kepi (λ)Depi (λ)
2
2
(1 + βepi (λ)) eKepi Depi − (1 − βepi (λ)) e−Kepi (λ)Depi (λ)
2
(λ) × eKder (λ)Dder (λ) − e−Kder (λ)Dder (λ)
1 − βder
2
2
,
(27)
4βepi (λ)
2
,
(26)
(1 + βder (λ)) eKder (λ)Dder (λ) − (1 − βder (λ)) e−Kder (λ)Dder (λ)
2
(1 + βepi (λ)) eKepi (λ)Depi (λ) − (1 − βepi (λ)) e−Kepi (λ)Depi (λ)
,
(28)
where variables Dder and Depi represent the thickness of
each layer in the skin. The total reflectance [32], [50] measured at the surface of the skin RKM is a function of the form
RT (λ) = Repi (λ) +
Tepi (λ)2 Rder (λ)
.
1 − Repi (λ)Rder (λ)
∀λ ∈ ΛR .
(30)
(18)
where fblood and Coxy are free variables. In the case of
the scattering coefficients of both layers, we employ the
definition of [50], where they are considered the sum of the
Mie and Rayleigh scattering coefficients at λ channel:
Kder (λ) =
Given a fixed set of wavelengths ΛR ⊂ Λ, the KubelkaMunk models the light based on the absorption and scattering
coefficients. Consequently, the total reflectance can be considered a function of the parameters given a set of frequencies
(29)
The model parameters are estimated by fitting a reflectance
sample (9) to the Kubelka-Muk reflectance model, such as
equation (3) in [50]. The cost function used to identify the
perfusion parameters is described next:
JKM =
X
2
[R(p, λ) − RKM (fmel , fblood , Coxy , Ddermis , Depi , λ)] ,
λ∈ΛR
(31)
where R(p, λ) is the sample reflectance from the multispectral camera in (9). Hence, the optimal parameters
(fmel , fblood , Coxy , Ddermis , Depi ) are obtained at each pixel
p ∈ P by minimizing the cost function in (31).
E. COMPARISON AND VALIDATION
The open-source database presented in this work consists
of a video sequence of multi-spectral images and PPG data
recorded in-vivo from multiple subjects. The PPG data serves
as a reference for estimating perfusion parameters from the
thumb. These values were compared against MSI perfusion
parameters from the fingertip of the middle finger. We selected these locations based on the accuracy of the perfusion parameters measured in these positions, such as SpO2
[52]. Due to the 10 min. duration of the occlusion protocol
(see Fig. 1), maintaining a static posture for the subjects
is challenging. Consequently, we implemented a tracking
algorithm to monitor a region of interest (ROI) around the
middle fingertip in the multi-spectral images and compare it
with the thumb PPG data. This section elaborates on the ROI
tracking and on the evaluation of the models for monitoring
skin perfusion.
1) ROI and Tracking
In this study, we employed the Kanade-Lucas-Tomasi (KLT)
feature tracking algorithm to track the fingertip movements
of the participants [53]. We used the point tracker implementation from Matlab (Mathworks, Inc., Natick, Massachusetts,
U.S.; v2020b). Initially, we manually selected a rectangular
ROI surrounding the middle fingertip in the first frame for
each participant video sequence. The features employed for
tracking were corners detected using the features from the accelerated segment test (FAST) algorithm [54]. We conducted
tracking on all participants every four frames throughout
the entire experimental protocol. The ROI obtained from
the tracking algorithm was multiplied with the energy mask
(as described in Section II-C) to isolate and process only
the middle fingertip region for estimating the MSI perfusion
parameters.
6
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
2) Evaluation of regression methods
We estimated skin perfusion parameters by fitting the linear and Kubelka-Munk models to the input absorbance and
reflectance signals, respectively. The perfusion parameters
(CHbO2 , CHb , α) in (14) were estimated using least squares
regression. In a similar fashion to [45], we set all negative
solutions to zero, as no constraints were applied. Meanwhile,
to solve the regression problem in (31) for the perfusion
parameters (fmel , fblood , Coxy , Ddermis , Depi ), we employed
a particle swarm optimization method. We used the Matlab
implementation provided with the optimization toolbox. The
boundaries employed for each perfusion parameter in the
Kubelka-Munk model are detailed in Table 1. The optimization method was configured to work with a swarm size of 50,
20 maximum simulations, and an error tolerance of 10−6 . All
the signal processing was implemented in a Dell Precision
3660 workstation, equipped with a 12th generation Intel Core
i7-12700K processor, and 16 GB of RAM. The preprocessing
stages, as well as the implementations, were performed in
Matlab.
Parameter
Ranges
figurations. We evaluated the perfusion parameters by employing different subsets in Λ. The linear model in (14)
requires at least a couple of wavelength channels; however,
feasible solutions were achieved using the following subsets:
Λ1A = {594, 632, 672} nm,
Λ2A = {632, 791} nm,
Λ3A = {632, 827} nm,
Λ4A
Λ5A
(32)
= {672, 791} nm,
= {672, 827} nm.
In contrast, the Kubelka-Munk model in (30) predominantly
exhibits accurate results for human skin when utilizing data
in the visible range, so we used the following subsets:
Λ1R = {558, 594, 632, 672} nm,
Λ2R = {558, 594, 632, 672, 714} nm,
Λ3R = {558, 594, 632, 672, 714, 751} nm,
Λ4R
Λ5R
(33)
= {594, 632, 672, 714} nm,
= {594, 632, 672, 714, 751} nm.
fmel
0.0100-3.0100
III. RESULTS
fblood
0.0010-0.5010
Coxy
0.6000-0.9900
Depi (cm)
0.0001-0.0006
Ddermis (cm)
0.0010-0.0040
The open-source database presented in this work comprises
records from 45 subjects who provided informed consent.
The age of the participants ranged from 18 to 24 (mean
= 20.17, SD = 1.73), with a majority being right-handed
(44/45) and having Fitzpatrick Skin Type III (26 participants)
and Type IV (19 participants). The information for each
participant is summarized in Table 2.
TABLE 1. Parameter ranges employed for the perfusion parameters
estimated from the Kubelka-Munk model
In this way, there are three perfusion parameters that can
be estimated from (15), and five from (31). However, we
could not obtain reference values for melanin or other chromophores, nor the thickness of the skin layers. Therefore, we
only perform a particular analysis of perfusion parameters
related to hemoglobin, namely (CHbO2 , CHb , fblood , Coxy ).
This study aims to evaluate if these parameters correlate with
the measurements obtained by the PPG sensor.
In these identification processes of skin perfusion parameters, one important challenge is the selection of wavelength
bands ΛA and ΛR . The regression methods in (15) and
(31) are sensitive to prior information, since the spectral
absorption and scattering coefficients are functions of the
available wavelength bands Λ.
In this work, we perform an analysis to evaluate the
Pearson correlation between MSI and PPG perfusion parameters during the application of the occlusion protocol.
Our goal is to select the wavelength channels with better
correlation against the PPG reference data, for both the
linear model in (14) and the Kubelka-Munk in (30). The
PPG reference values of ∆[HbO2 ] in (6) and ∆[Hb] in (7)
were interpolated to match the MSI framerate. Every four
multi-spectral images, these values were correlated against
(CHbO2 , CHb , fblood , Coxy ) using different wavelength con-
FIGURE 2. Infographic of the data available online upon request [55]. Raw
data files for all the 45 participants, including PPG files and reference MSI data
are available for the evaluation of novel perfusion parameters estimation
methods.
Sequences of the multi-spectral images and PPG data from
all recruited subjects are accessible in the following repository in Zenodo https://doi.org/10.5281/zenodo.7860900. The
database contains at least 2,445 MSI for each participant, see
7
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
ID
Age
Gender
Skin type
Systolic P.
# Multi-spectral Images
Time Length
Hyperemia
P1
20
M
4
109
2,456
09:58:7960
yes
P2
20
M
3
129
2,458
09:59:2880
yes
P3
22
M
4
117
2,460
09:59:7730
yes
P4
19
F
3
110
2,454
09:58:3120
no
P5
18
F
4
106
2,458
09:59:2839
no
P6
18
F
4
111
2,471
10:02:4600
yes
P7
18
F
4
91
2,462
10:00:2630
yes
P8
18
F
4
102
2,474
10:03:1930
yes
P9
21
M
3
113
2,468
10:01:7300
yes
P10
19
F
3
108
2,461
10:00:0340
yes
P11
18
M
4
137
2,461
10:00:0210
yes
P12
18
F
3
132
2,457
09:59:0429
yes
P13
18
M
4
119
2,461
10:00:0210
yes
P14
18
F
4
100
2,460
09:59:7770
yes
P15
18
F
3
104
2,460
09:59:7740
yes
P16
18
M
3
126
2,462
10:00:2660
yes
P17*
18
F
3
105
2,469
10:01:9710
yes
P18
21
F
4
122
2,461
10:00:0200
no
P19
21
F
3
130
2,462
10:00:2660
yes
P20
21
F
3
106
2,457
09:59:0440
yes
P21
23
M
3
133
2,459
09:59:5290
yes
P22
23
M
3
134
2,471
10:02:4590
no
P23
21
F
3
115
2,472
10:02:6630
yes
P24
21
M
3
111
2,445
10:00:2220
yes
P25
21
M
3
116
2,460
09:59:7330
yes
P26
21
M
4
107
2,462
10:00:2310
yes
P27
21
F
4
106
2,460
09:59:7440
yes
P28
24
F
4
106
2,460
09:59:7720
yes
P29
22
M
4
125
2,460
09:59:7700
yes
P30
21
M
4
125
2,461
10:00:0150
yes
P31
21
F
3
100
2,472
10:02:6959
yes
P32
22
M
3
120
2,460
09:59:7720
yes
P33
21
M
4
127
2,461
10:00:0140
yes
P34
19
F
3
100
2,457
09:59:0400
yes
P35
19
F
3
108
2,460
09:59:7730
yes
P36
20
F
3
136
2,471
10:02:4570
yes
P37
19
M
4
129
2,457
09:59:0380
yes
P38*
19
M
3
128
2,463
10:00:5040
yes
P39*
18
M
3
111
2,479
10:04:4060
yes
P40
23
M
4
110
2,462
10:00:2570
yes
P41
21
M
3
130
2,465
10:00:9930
yes
P42
20
F
3
126
2,461
10:00:0170
yes
P43
22
F
3
125
2,459
09:59:5270
yes
P44
22
M
3
138
2,467
10:01:4820
yes
P45
22
M
4
104
2,461
10:00:0160
yes
TABLE 2. Participants data in the experimental protocol, where the table presents information from each subject, identifiable by a unique code. Age, gender, and
skin type (as per the Fitzpatrick scale) are reported. The systolic pressure recorded before the start stage of the protocol is also presented for each subject. In the
following columns, the number of multi-spectral images per patient, each composed of nine channels, along with the length of data collection in minutes, seconds,
and milliseconds are detailed. The last column indicates the occurrence of reactive hyperemia, marked by a decrease in ∆[HbO2 ] and an increase in ∆[Hb]
during the TO stage, as well as an inverse trend following the pressure release. The participants who presented high movement during the experiment are marked
with a symbol *.
8
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
Fig. 2. Each multi-spectral image consists of the nine single
channels in PNG format, as detailed in subsection II-C. We
opted for the PNG format due to its lossless compression and
user-friendly metadata management, particularly for nontechnical users like those in the medical field. This choice
aligns with our goal of creating a database accessible to
multidisciplinary research teams. Full hand and finger masks
obtained from the tracking process are available. The raw
PPG data is also included as simple comma-separated value
files. Reference white material MSI data is also available to
test different calibration methods.
Examples of multispectral images obtained for a single
participant, at two different times (start and TO stages),
during the occlusion protocol are displayed in Fig. 3. The perfusion parameters estimated at each location of the MSI can
be arranged to obtain perfusion maps. These images provide
spatially localized quantitative information that can assist
physicians in diagnosing and monitoring tissue conditions
without a biopsy. Examples of perfusion maps obtained for a
single patient at different stages of the occlusion experiment
are displayed in Fig. 4. While changes in CHbO2 , CHb , and
fmel are evident, the magnitude of these changes is measured
by evaluating the correlation between the values obtained
from the middle finger and the reference PPG signals from
the thumb.
For the initial evaluation of the database, the participants
who presented excessive movement during the protocol (P17,
P38, and P39) were excluded. Additionally, subjects who did
not exhibit hyperemia during the occlusion protocol were
also excluded (participants: P4, P5, P18, and P22). Consequently, the validation experiments presented in the subsequent subsections are based on data from 38 participants.
A. PPG PERFUSION PARAMETERS
The measurements obtained are shown in the Figs. 5 to 7
. Figure 5 A) illustrates the range and mean values for the
estimations of ACRed and ACIR by (4) and (5) in the thumb,
respectively. The observed data aligns with measurements
reported by Abay et al. (2015) [36], wherein a considerable
decrease in AC values occurs during total occlusion (8:00 to
10:00 min). As depicted in Fig. 5 B), the DC components
are also affected by the occlusion stages, with considerable
inter-subject variability, particularly in the red component.
Both DCRed and DCIR components exhibit a decline during
the VO stage. However, during TO, DCRed decreases, while
DCIR increases above nominal values.
The resulting ratio of absorbances RP P G in (1) is presented in Fig. 5 C). This perfusion parameter displays high
variability throughout the entire experiment, with multiple
peaks occurring even in stages without blood cuff pressure.
As observed during the protocol, the average value of RP P G
rises during occlusion stages at 2:00-4:00 min. (VO) and
6:00-8:00 min. (TO).
The SpO2 range and mean values, as calculated from
equation (2), are displayed in Fig. 6 A). This perfusion
parameter also exhibits variability in the absence of applied
pressure. It is worth noting that, according to the literature
[56], values below 70% for SpO2 are considered unreliable.
This threshold is reached during occlusion stages, which is
why this parameter is not included in the evaluation against
MSI perfusion parameters. Next, Fig. 6 B) illustrates the estimation of P IIR by (3). This perfusion parameter is sensitive
to reperfusion occurring after each occlusion stage, particularly around 4:00 and 8:00 min. During total occlusion, the
values of P IIR drop considerably.
Figure 7 presents the changes in hemoglobin contribution
∆[HbO2 ] and ∆[Hb] by (6) and (7), respectively. These values exhibit low inter-subject variability, particularly during
the start (0:00-2:00 min.) and rest (4:00-6:00 min.) stages.
The sampled signals are tolerant to occlusion protocols, as
reported by Abay et al. (2018) [37]. Both range and mean
signals decline during the VO stage and return to normal
during the resting one. During TO (6:00-8:00 min.), the mean
value of ∆[HbO2 ] decreases, while ∆[Hb] increases. Upon
the release of blood cuff pressure, the hyperemia stage (8:0010:00 min.) is characterized by a rapid increase in ∆[HbO2 ]
levels and a decrease in ∆[Hb]. Hence, the changes in these
PPG perfusion parameters were utilized for the evaluation of
MSI parameters.
B. MSI PERFUSION PARAMETERS CORRELATION
In this preliminary analysis, we sought to validate the effectiveness of MSI data for assessing the estimation of in-vivo
perfusion parameters during an occlusion protocol. According to the literature [40], and the obtained PPG measurements
(see Fig. 7, the parameters least prone to inconsistencies
during an occlusion are ∆[HbO2 ] and ∆[Hb]. Nonetheless,
the estimated signals for each parameter display a similar
trend throughout the initial three stages of the protocol (start,
VO and rest). In fact, during the VO stage (2:00-4:00 min.),
both ∆[HbO2 ] and ∆[Hb] tend to increase and subsequently
revert to a baseline state during the rest stage (4:00-6:00 min).
To avoid potential inaccuracies in the Pearson correlationbased evaluation, we focused on assessing the correlation
outcomes for the signals ∆[HbO2 ] and ∆[Hb] during the
latter half of the experiment, starting from the 5:00 min. mark
until the end.
1) Correlation between ∆[HbO2 ] and MSI perfusion
parameters
The ∆[HbO2 ] reference measurements were obtained from
the thumb of each participant, based on the PPG measurements (see Fig. 1). They were estimated by (6) and are shown
in Fig. 7. We evaluated the Pearson correlation of this signal
against the perfusion parameters (CHbO2 , CHb , fblood , Coxy )
from the linear and Kubelka-Munk models. These parameters
were extracted from a ROI surrounding the middle fingertip,
which was tracked throughout the occlusion protocol. The
correlation calculated for the 38 participants, during the rest,
TO, and hyperemia stages, employing the wavelength subsets
in (32) and (33) are illustrated in violin plots in Figs. 8 to 11
[57].
9
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
FIGURE 3. Four single channel images recorded for Participant 1. Each column displays the reflectance at 558, 632, 714 and 791 nm, respectively. The images on
the bottom were recorded at 1 minute and 8 seconds from the start of the experiment (Start). Meanwhile, on the top, the images were recorded at 7 minutes and 48
seconds, near the end of the TO stage.
FIGURE 4. Perfusion Maps of 4 parameters related to hemoglobin and obtained during the Start (top row) and TO (bottom row) stages. The first and second
columns depict the CHbO2 and CHb maps estimated with the linear model. The third and fourth columns show the fblood and Coxy maps estimated with the
Kubelka-Munk model, respectively.
First, the hemoglobin perfusion parameters (CHbO2 , CHb )
from the linear model in (14) exhibited mostly strong negative correlation values, with medians ranging from -0.5 to 0.7, as shown in Figs. 8 and 9. Nevertheless, a strong positive
correlation was observed for CHbO2 with a median of 0.8,
using the subset Λ2A . This value represented the highest
correlation with ∆[HbO2 ] among all the MSI perfusion
parameters evaluated. Next, we evaluated the blood perfusion
parameters (fblood , Coxy ) from the Kubelka-Munk model in
(18). The estimated values of fblood for different subsets ΛR
show weak negative correlations, see Fig. 10, with median
values around -0.3. Meanwhile, according to the findings in
Fig. 11, only three configurations yielded moderate to strong
positive correlations with Coxy .
2) Correlation between ∆[Hb] and MSI perfusion
parameters
The correlation results for the PPG parameter ∆[Hb] in (7)
and shown in Fig. 7, in relation to MSI perfusion parameters,
are presented in Figs. 12 to 15. The results for the linear
10
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
FIGURE 5. Range and average values of reference parameters measured using the PPG sensor throughout the occlusion protocol. Panel A) displays the ACRed
and ACIR components, which are sensitive to the total occlusion applied at the beggining of the 8:00 minute mark. Panel B) shows the DCRed and DCIR
signals, which do not register a considerable reduction during the occlusion stages. Panel C) shows RP P G estimated by (1).
FIGURE 6. Panel A) displays the range and mean values of SpO2 estimated using equation (2) throughout the occlusion experiment. SpO2 values above the
black dotted line are considered to be within an acceptable range. Panel B) shows P IIR estimated using equation (3).
11
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
FIGURE 7. Range and mean values of ∆[HbO2 ] and ∆[Hb] estimated by (6) and (7), respectively, for the 38 participants included in this analysis. These
perfusion parameters are tolerant to total occlusion and illustrate the hyperemia and reperfusion phenomena around 08:00 min.
The correlation results with CHb were all highly positive,
exhibiting median values around 0.8 for all wavelength subsets, which is consistent with expectations.
Pearson Correlation vs
Pearson Correlation vs
[HbO2]
[HbO2]
model parameters (CHbO2 , CHb ) are illustrated in Figs. 12
and 13. A strong negative correlation between ∆[Hb] and
CHbO2 was anticipated; however, this trend was only observed for the subset λ1A , while the remaining configurations
demonstrated strong positive correlations.
Wavelength bands used in the KM method for estimating fblood
Wavelength bands used in the LM method for estimating CHbO
2
FIGURE 10. Distribution of the correlation results for ∆[HbO2 ] vs fblood
from the Kubelka-Munk model 31. The median value is displayed with a
magenta marker.
Pearson Correlation vs
Pearson Correlation vs
[HbO2]
[HbO2]
FIGURE 8. Distribution of the correlation results for ∆[HbO2 ] vs CHbO2 from
the linear model 15. The median value is displayed with a magenta marker.
Wavelength bands used in the KM method for estimating Coxy
Wavelength bands used in the LM method for estimating CHb
FIGURE 9. Distribution of the correlation results for ∆[HbO2 ] vs CHb from
the linear model 15. The median value is displayed with a magenta marker.
FIGURE 11. Distribution of the correlation results for ∆[HbO2 ] vs Coxy from
the Kubelka-Munk model 31. The median value is displayed with a magenta
marker.
12
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Pearson Correlation vs
Pearson Correlation vs
[Hb]
[Hb]
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
Wavelength bands used in the LM method for estimating CHbO
Wavelength bands used in the KM method for estimating Coxy
2
FIGURE 12. Distribution of the correlation results for ∆[Hb] vs CHbO2 from
the linear model 15. The median value is displayed with a magenta marker.
FIGURE 15. Distribution of the correlation results for ∆[Hb] vs Coxy from the
Kubelka-Munk model 31.The median value is displayed with a magenta
marker.
Pearson Correlation vs
[Hb]
IV. DISCUSSION
Wavelength bands used in the LM method for estimating CHb
Pearson Correlation vs
[Hb]
FIGURE 13. Distribution of the correlation results for ∆[Hb] vs CHb from
linear model 15. The median value is displayed with a magenta marker.
Wavelength bands used in the KM method for estimating fblood
FIGURE 14. Distribution of the correlation results for ∆[Hb] vs fblood from
the Kubelka-Munk model 31 The median value is displayed with a magenta
marker.
On the other hand, the fblood parameter from the KubelkaMunk model demonstrated a strong positive correlation
(0.72-0.82) across all wavelength subsets when compared
with ∆[Hb], see Fig. 14. No clear trend emerged from the
multiple implementations with Coxy from the Kubelka-Munk
model, see Fig. 15. However, these results are consistent with
the results reported for ∆[HbO2 ] in Fig. 11. This is, the
results obtained for ∆[Hb] have an opposite sign to those
obtained for ∆[HbO2 ].
In this study, we developed an open-source database to measure changes in hemoglobin concentrations by a sequence
of multi-spectral images. These changes were induced by
a controlled occlusion protocol that lasts 10 min. During
the protocol, MSI data from the hand palm and PPG measurements from the thumb were simultaneously recorded.
The database comprises records from 45 test subjects who
provided informed consent. The database can be accessed
upon request via Zenodo [55]. We also conducted a preliminary evaluation of the database. Our analysis of the PPG
measurements revealed certain parameter failures during the
occlusion stages, particularly concerning SpO2 . The findings
corroborate those of Abay et al. [36], demonstrating that
∆[HbO2 ] and ∆[Hb], as estimated from PPG sensors, are
sensitive to occlusion stages and capable of tracking phenomena such as reperfusion and hyperemia after blood cuff
pressure release.
In an initial evaluation of the MSI data, we tested two
regression approaches for estimating perfusion parameters.
These methods are based on prior knowledge, particularly
spectral absorption and scattering coefficients for the most
prevalent chromophores in human skin. Our results confirmed strong correlations, both positive and negative, between PPG and MSI-based perfusion parameters. The preliminary outcomes indicate that MSI-based perfusion parameters can effectively measure changes in both oxygenated
and deoxygenated hemoglobin. Additionally, the database
provides valuable data for validation purposes, which is often
challenging to obtain experimentally and is available for evaluating alternative MSI-based methodologies under a standardized protocol and controlled conditions. We anticipate
that this database will be useful in validating novel methods
based on MSI for in-vivo estimation of perfusion parameters.
Finally, the study population is young and representative of
the Mexican inhabitants, which exhibits minimal variation
in skin phenotypes. However, the sample does not consider
younger or older subjects. Owing to acquisition limitations,
the evaluation was conducted using only a subset of the actual
data. A total of 38 subjects with clean PPG data and observable hyperemia following the total occlusion stage were
included in the analysis. Future research will be committed to
13
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
the development of practical perfusion monitoring in clinical
settings. Moreover, we aim to estimate perfusion parameters
without prior information, such as assumptions about the
sample population.
[16]
[17]
ACKNOWLEDGMENT
L. Granados-Castro acknowledges the financial support of
CONACYT through a doctoral fellowship [grant number
881980].
[18]
REFERENCES
[19]
[1] P. Shaw, A. K. Sharma, A. Kalonia, and S. K. Shukla, “Vascular perfusion:
A predictive tool for thermal burn injury,” Journal of tissue viability,
vol. 29, no. 1, pp. 48–50, 2020.
[2] R. K. Rogers, M. Montero-Baker, M. Biswas, J. Morrison, and J. Braun,
“Assessment of foot perfusion: Overview of modalities, review of evidence, and identification of evidence gaps,” Vascular Medicine, vol. 25,
no. 3, pp. 235–245, 2020.
[3] Y. Monteerarat, R. Limthongthang, P. Laohaprasitiporn, and T. Vathana,
“Reliability of capillary refill time for evaluation of tissue perfusion in
simulated vascular occluded limbs,” European Journal of Trauma and
Emergency Surgery, pp. 1–7, 2022.
[4] B. Ruaro, M. G. Nallino, A. Casabella, F. Salton, P. Confalonieri,
A. De Tanti, and C. Bruni, “Monitoring the microcirculation in the diagnosis and follow-up of systemic sclerosis patients: Focus on pulmonary
and peripheral vascular manifestations,” Microcirculation, vol. 27, no. 8,
p. e12647, 2020.
[5] R. Kumar, R. J. Gush, C. E. Murdoch, and N. Krstajić, “Simultaneous
white light and laser speckle contrast imaging for in-vivo blood flow
imaging during laparoscopic surgery: an alternative to fluorescence-based
endoscopy,” in Endoscopic Microscopy XVII, vol. 11937, p. 1193702,
SPIE, 2022.
[6] R. Aughwane, N. Mufti, D. Flouri, K. Maksym, R. Spencer, M. Sokolska,
G. Kendall, D. Atkinson, A. Bainbridge, J. Deprest, et al., “Magnetic resonance imaging measurement of placental perfusion and oxygen saturation
in early-onset fetal growth restriction,” BJOG: An International Journal of
Obstetrics & Gynaecology, vol. 128, no. 2, pp. 337–345, 2021.
[7] C. Huang, J. Liang, X. Lei, X. Xu, Z. Xiao, and L. Luo, “Diagnostic
performance of perfusion computed tomography for differentiating lung
cancer from benign lesions: a meta-analysis,” Medical Science Monitor:
International Medical Journal of Experimental and Clinical Research,
vol. 25, p. 3485, 2019.
[8] G. Dinsdale, S. Wilkinson, J. Wilkinson, T. L. Moore, J. B. Manning,
M. Berks, E. Marjanovic, M. Dickinson, A. L. Herrick, and A. K. Murray,
“State-of-the-art technologies provide new insights linking skin and blood
vessel abnormalities in ssc-related disorders,” Microvascular Research,
vol. 130, p. 104006, 2020.
[9] A. Karlas, M. Kallmayer, N.-A. Fasoula, E. Liapis, M. Bariotakis,
M. Krönke, M. Anastasopoulou, J. Reber, H.-H. Eckstein, and V. Ntziachristos, “Multispectral optoacoustic tomography of muscle perfusion
and oxygenation under arterial and venous occlusion: A human pilot
study,” Journal of Biophotonics, vol. 13, no. 6, p. e201960169, 2020.
[10] W. Li, J. Xia, G. Zhang, H. Ma, B. Liu, L. Yang, Y. Zhou, X. Dong, F. Fu,
and X. Shi, “Fast high-precision electrical impedance tomography system
for real-time perfusion imaging,” IEEE Access, vol. 7, pp. 61570–61580,
2019.
[11] W. Huber, R. Zanner, G. Schneider, R. Schmid, and T. Lahmer, “Assessment of regional perfusion and organ function: less and non-invasive
techniques,” Frontiers in medicine, vol. 6, p. 50, 2019.
[12] I. N. de Keijzer, D. Massari, M. Sahinovic, M. Flick, J. J. Vos, and
T. W. Scheeren, “What is new in microcirculation and tissue oxygenation
monitoring?,” Journal of Clinical Monitoring and Computing, vol. 36,
no. 2, pp. 291–299, 2022.
[13] M. Kumar, J. W. Suliburk, A. Veeraraghavan, and A. Sabharwal, “Pulsecam: a camera-based, motion-robust and highly sensitive blood perfusion
imaging modality,” Scientific reports, vol. 10, no. 1, pp. 1–17, 2020.
[14] V. Gupta and V. K. Sharma, “Skin typing: Fitzpatrick grading and others,”
Clinics in dermatology, vol. 37, no. 5, pp. 430–436, 2019.
[15] S. Rahman, A. Iskandarova, M. E. Horowitz, K. K. Sanghavi, K. T. Aziz,
N. Durr, and A. M. Giladi, “Assessing hand perfusion with eulerian video
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
magnification and waveform extraction,” The Journal of Hand Surgery,
2022.
Y. Garini, I. T. Young, and G. McNamara, “Spectral imaging: principles
and applications,” Cytometry Part A: The Journal of the International
Society for Analytical Cytology, vol. 69, no. 8, pp. 735–747, 2006.
M. Wang, D. Hong, Z. Han, J. Li, J. Yao, L. Gao, B. Zhang, and
J. Chanussot, “Tensor decompositions for hyperspectral data processing in
remote sensing: A comprehensive review,” IEEE Geoscience and Remote
Sensing Magazine, vol. 11, no. 1, pp. 26–72, 2023.
Y. Xu, Q. Du, and N. Younan, “Particle swarm optimization-based band
selection for hyperspectral target detection,” in 2016 IEEE International
Geoscience and Remote Sensing Symposium (IGARSS), pp. 5872–5875,
2016.
P. Wang, L. Wang, H. Leung, and G. Zhang, “Super-resolution mapping
based on spatial–spectral correlation for spectral imagery,” IEEE Transactions on Geoscience and Remote Sensing, vol. 59, no. 3, pp. 2256–2268,
2021.
A. Mancini, E. Frontoni, and P. Zingaretti, “Satellite and uav data for
precision agriculture applications,” in 2019 International Conference on
Unmanned Aircraft Systems (ICUAS), pp. 491–497, 2019.
X. Xia, W. Liu, L. Wang, and J. Sun, “Hsifoodingr-64: A dataset for hyperspectral food-related studies and a benchmark method on food ingredient
retrieval,” IEEE Access, vol. 11, pp. 13152–13162, 2023.
N. T. Clancy, G. Jones, L. Maier-Hein, D. S. Elson, and D. Stoyanov,
“Surgical spectral imaging,” Medical image analysis, vol. 63, p. 101699,
2020.
A. Schmidt, F. Nießner, T. von Woedtke, and S. Bekeschus, “Hyperspectral
imaging of wounds reveals augmented tissue oxygenation following cold
physical plasma treatment in vivo,” IEEE Transactions on Radiation and
Plasma Medical Sciences, vol. 5, no. 3, pp. 412–419, 2021.
A. A. Bruins, D. G. Geboers, J. R. Bauer, J. H. Klaessens, R. M. Verdaasdonk, and C. Boer, “The vascular occlusion test using multispectral
imaging: a validation study: the vasoimage study,” Journal of clinical
monitoring and computing, vol. 35, pp. 113–121, 2021.
S. P. Philimon and A. K. C. Huong, “Laser speckle integrated multispectral
imaging system for in-vivo assessment of diabetic foot ulcer healing: A
clinical study,” IEEE Access, vol. 9, pp. 23726–23736, 2021.
H. Fabelo, S. Ortega, A. Szolna, D. Bulters, J. F. Piñeiro, S. Kabwama,
A. J-O’Shanahan, H. Bulstrode, S. Bisshopp, B. R. Kiran, D. Ravi,
R. Lazcano, D. Madroñal, C. Sosa, C. Espino, M. Marquez, M. De La
Luz Plaza, R. Camacho, D. Carrera, M. Hernández, G. M. Callicó, J. Morera Molina, B. Stanciulescu, G.-Z. Yang, R. Salvador, E. Juárez, C. Sanz,
and R. Sarmiento, “In-vivo hyperspectral human brain image database for
brain cancer detection,” IEEE Access, vol. 7, pp. 39098–39116, 2019.
M. Dietrich, S. Marx, M. von der Forst, T. Bruckner, F. Schmitt, M. Fiedler,
F. Nickel, A. Studier-Fischer, B. Müller-Stich, T. Hackert, et al., “Bedside
hyperspectral imaging indicates a microcirculatory sepsis pattern-an observational study,” Microvascular Research, vol. 136, p. 104164, 2021.
S. L. Jacques, “Optical properties of biological tissues: a review,” Physics
in Medicine & Biology, vol. 58, no. 11, p. R37, 2013.
A. Holmer, J. Marotz, P. Wahl, M. Dau, and P. W. Kämmerer, “Hyperspectral imaging in perfusion and wound diagnostics–methods and
algorithms for the determination of tissue parameters,” Biomedical Engineering/Biomedizinische Technik, vol. 63, no. 5, pp. 547–556, 2018.
L. Annala and I. Pölönen, “Kubelka–munk model and stochastic model
comparison in skin physical parameter retrieval,” Computational Sciences
and Artificial Intelligence in Industry: New Digital Technologies for
Solving Future Societal and Economical Challenges, pp. 137–151, 2022.
L. Annala, S. Äyrämö, and I. Pölönen, “Comparison of machine learning
methods in stochastic skin optical model inversion,” Applied Sciences,
vol. 10, no. 20, p. 7097, 2020.
R. Jolivot, Y. Benezeth, and F. Marzani, “Skin parameter map retrieval
from a dedicated multispectral imaging system applied to dermatology/cosmetology,” Journal of Biomedical Imaging, vol. 2013, pp. 26–26, 2013.
J. B. West, D. L. Wang, G. K. Prisk, J. M. Fine, A. Bellinghausen,
M. Light, and D. R. Crouch, “Noninvasive measurement of pulmonary
gas exchange: comparison with data from arterial blood gases,” American
Journal of Physiology-Lung Cellular and Molecular Physiology, vol. 316,
no. 1, pp. L114–L118, 2019. PMID: 30335497.
I. Badiola, V. Blazek, V. J. Kumar, B. George, S. Leonhardt, and C. H.
Antink, “Accuracy enhancement in reflective pulse oximetry by considering wavelength-dependent pathlengths,” Physiological Measurement,
vol. 43, no. 9, p. 095001, 2022.
14
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
[35] G. Bade, D. S. Chandran, A. Kumar Jaryal, A. Talwar, and K. K. Deepak,
“Contribution of systemic vascular reactivity to variability in pulse volume amplitude response during reactive hyperemia,” European journal of
applied physiology, vol. 119, pp. 753–760, 2019.
[36] T. Y. Abay and P. A. Kyriacou, “Reflectance photoplethysmography as
noninvasive monitoring of tissue blood perfusion,” IEEE Transactions on
Biomedical Engineering, vol. 62, no. 9, pp. 2187–2195, 2015.
[37] T. Abay and P. Kyriacou, “Photoplethysmography for blood volumes and
oxygenation changes during intermittent vascular occlusions,” Journal of
clinical monitoring and computing, vol. 32, no. 3, pp. 447–455, 2018.
[38] M. INTEGRATED, “Max30102 high-sensitivity pulse oximeter and heartrate sensor for wearable health,” Datasheet, Rev, vol. 1, p. 32, 2018.
[39] S. K. Longmore, G. Y. Lui, G. Naik, P. P. Breen, B. Jalaludin, and G. D.
Gargiulo, “A comparison of reflective photoplethysmography for detection
of heart rate, blood oxygen saturation, and respiration rate at various
anatomical locations,” Sensors, vol. 19, no. 8, p. 1874, 2019.
[40] T. Abay and P. Kyriacou, “Comparison of nirs, laser doppler flowmetry,
photoplethysmography, and pulse oximetry during vascular occlusion
challenges,” Physiological Measurement, vol. 37, no. 4, p. 503, 2016.
[41] M. Coutrot, E. Dudoignon, J. Joachim, E. Gayat, F. Vallee, and F. Depret,
“Perfusion index: Physical principles, physiological meanings and clinical
implications in anaesthesia and critical care,” Anaesthesia Critical Care &
Pain Medicine, vol. 40, no. 6, p. 100964, 2021.
[42] M. Cope, The development of a near infrared spectroscopy system and
its application for non invasive monitoring of cerebral blood and tissue
oxygenation in the newborn infants. University of London, University
College London (United Kingdom), 1991.
[43] M. S. Shaikh, K. Jaferzadeh, B. Thörnberg, and J. Casselgren, “Calibration
of a hyper-spectral imaging system using a low-cost reference,” Sensors,
vol. 21, no. 11, p. 3738, 2021.
[44] S. Prahl, “Optical absorption of hemoglobin. 1999,” URl:
https://omlc.org/spectra/hemoglobin/, 2014.
[45] N. T. Clancy, S. Arya, D. Stoyanov, M. Singh, G. B. Hanna, and D. S.
Elson, “Intraoperative measurement of bowel oxygen saturation using a
multispectral imaging laparoscope,” Biomedical optics express, vol. 6,
no. 10, pp. 4179–4190, 2015.
[46] K. J. Zuzak, M. D. Schaeberle, E. N. Lewis, and I. W. Levin, “Visible reflectance hyperspectral imaging: characterization of a noninvasive, in vivo
system for determining tissue perfusion,” Analytical chemistry, vol. 74,
no. 9, pp. 2021–2028, 2002.
[47] S. P. Nighswander-Rempel, R. A. Shaw, V. V. Kupriyanov, J. Rendell,
B. Xiang, and H. H. Mantsch, “Mapping tissue oxygenation in the beating
heart with near-infrared spectroscopic imaging,” Vibrational spectroscopy,
vol. 32, no. 1, pp. 85–94, 2003.
[48] B. S. Sorg, B. J. Moeller, O. Donovan, Y. Cao, and M. W. Dewhirst, “Hyperspectral imaging of hemoglobin saturation in tumor microvasculature
and tumor hypoxia development,” Journal of biomedical optics, vol. 10,
no. 4, pp. 044004–044004, 2005.
[49] L. Gevaux, C. Adnet, P. Séroul, R. Clerc, A. Trémeau, J. L. Perrot, and
M. Hébert, “Three-dimensional maps of human skin properties on full face
with shadows using 3-d hyperspectral imaging,” Journal of biomedical
optics, vol. 24, no. 6, pp. 066002–066002, 2019.
[50] C. Li, V. Brost, Y. Benezeth, F. Marzani, and F. Yang, “Design and evaluation of a parallel and optimized light–tissue interaction-based method
for fast skin lesion assessment,” Journal of Real-Time Image Processing,
vol. 15, pp. 407–420, 2018.
[51] R. R. Anderson and J. A. Parrish, “The optics of human skin,” Journal of
investigative dermatology, vol. 77, no. 1, pp. 13–19, 1981.
[52] G. Basaranoglu, M. Bakan, T. Umutoglu, S. U. Zengin, K. Idin, and
Z. Salihoglu, “Comparison of spo2 values from different fingers of the
hands,” Springerplus, vol. 4, no. 1, p. 561, 2015.
[53] B. D. Lucas and T. Kanade, “An iterative image registration technique
with an application to stereo vision,” in IJCAI’81: 7th international joint
conference on Artificial intelligence, vol. 2, pp. 674–679, 1981.
[54] E. Rosten and T. Drummond, “Fusing points and lines for high performance tracking,” in Tenth IEEE International Conference on Computer
Vision (ICCV’05) Volume 1, vol. 2, pp. 1508–1515 Vol. 2, 2005.
[55] O. Gutierrez-Navarro, L. Granados-Castro, A. R. Mejia-Rodriguez, and
D. U. Campos-Delgado, “A Dataset for Evaluating and Validating Blood
Perfusion Monitoring During an Occlusion Protocol: Multi-spectral and
Plethysmography data,” Apr. 2023. Data formats MSI: png files PPG: csv
files with txt extension.
[56] E. D. Chan, M. M. Chan, and M. M. Chan, “Pulse oximetry: understanding
its basic principles facilitates appreciation of its limitations,” Respiratory
medicine, vol. 107, no. 6, pp. 789–799, 2013.
[57] Jonas, “Violin plots for plotting multiple distributions (distributionplot.m).”
OMAR GUTIERREZ-NAVARRO earned his
Bachelor of Science degree in Electronics Engineering from the Universidad Autónoma of San
Luis Potosí (UASLP), Mexico, in 2007. He later
pursued a Master of Science degree in Computer
Science and Industrial Mathematics from the Centro de Investigacion en Matematicas (CIMAT),
Guanajuato, Mexico, in 2010. In 2012, Omar was
awarded with the Fulbright-Garcia Robles grant,
facilitating his research as a Visiting Scholar at
Texas A&M University’s Biomedical Engineering Department. He completed his Ph.D. in Electronics Engineering at UASLP in 2015, concentrating on numerical methods for characterizing in-vivo tissue through timeresolved fluorescence lifetime imaging microscopy data. Dr. GutierrezNavarro joined the Biomedical Engineering Department at the Universidad
Autonoma de Aguascalientes in 2015. His research interests include signal
processing, machine learning, and multi/hyperspectral imaging applications
within food science and biomedical engineering.
LILIANA GRANADOS-CASTRO received the
B.Sc. degree in biomedical engineering in 2017
and the M. Sc. degree in computer science and
artificial intelligence, in 2020, from the Universidad Autónoma de Aguascalientes, Aguascalientes,
Mexico. She made a research stay in 2019 at
the Universidad Tecnológica de Panama and in
2022 at the Universidad de Las Palmas de Gran
Canaria. She is currently working toward a Ph.D.
in biomedical engineering at the Universidad Autonoma de San Luis Potosi, San Luis Potosi, México. Her research interest includes photoplethysmography, pulse-oximetry, spectral imaging, and
blood perfusion on large body areas.
ALDO RODRIGO MEJIA RODRIGUEZ received the B.S. and Master of Science degrees
in biomedical engineering from UAM-I, Mexico
City, Mexico, in 2006 and 2009 respectively, and
the Ph.D. degree in bioengineering from the Politecnico di Milano, Milan, Italy, in 2013. Since
June 2014, he has been a Faculty Member for
the Biomedical Engineering and the Postgraduates Programs on Electronic Engineering and Life
Sciences at the School of Sciences, Universidad
Autónoma de San Luis Potosi (UASLP). His research work focuses mainly
on the processing and analysis of medical images for clinical applications,
and the design and analysis of biomedical instrumentation for wearable
devices and support systems in clinical decision making. He was involved
in the organization of conferences related to biomedical engineering such
as ENIBET 2018 and 2019 (Conference Chair), CLAIB 2019 (Scientific
Challenge Chair), CNIB 2020 (Conference Chair), EMBC-IEEE 2021
(Theme Chair—Biomedical Imaging and Image Processing), and CNBI
2023 (Theme Chair— AI, Modeling and Simulation of Biological Systems,
Bioinformatics and Computational Biology). He was an Associate Editor
for the Mexican Journal of Biomedical Engineering (Revista Mexicana de
Ingeniería Biomédica—RMIB) from January 2020 to December 2021
15
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3305256
Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS
DANIEL U. CAMPOS-DELGADO received the
BS degree in electronics engineering from Universidad Autónoma of San Luis Potosí (UASLP),
Mexico, in 1996, and the MSEE and PhD degrees
in electrical engineering from Louisiana State University (LSU), USA, in 1999 and 2001, respectively. In 2001, he joined the School of Science
of UASLP as a profesor. His research interests
include estimation and detection, optimization algorithms, fault diagnosis, artificial inteligence and
signal processing. Dr Campos-Delgado has been advisor or co-advisor
of 27 bachelor thesis projects, 22 Master thesis works, and 8 Doctoral
dissertations. He is currently a member of the Mexican Academy of Sciences (AMC), and a Senior Member in the IEEE. In 2001, the College of
Engineering of LSU granted him the ‘Exemplary Dissertation Award’, and
in 2009 and 2013, he received awards as a Young Researcher from UASLP
and AMC. From July/2016 to June/2020, Dr. Campos-Delgado was the Head
of the School of Science, and since January/2021, he was appointed as the
Director of the Institute for Optical Comunication Research, both in UASLP.
From May/2019 to September/2022, he was an associate editor for IEEE
Latin America Transactions (ISSN: 1548-0992), and since October/2022, he
is Deputy Editor-in-Chief in this same journal.
16
VOLUME 4, 2016
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/