Optics and Photonics Journal, 2013, 3, 23-27
Published Online November 2013 (http://www.scirp.org/journal/opj)
http://dx.doi.org/10.4236/opj.2013.37A004
Open Access OPJ
Dynamic Analysis of Mental Sweating by the
Time-Sequential Piled-Up En-Face OCT Images
Masato Ohmi, Yuki Wada, Motomu Tanigawa
Division of Health Sciences, Graduate School of Medicine, Osaka University, Suita City, Japan
Received July 26, 2013; revised August 25, 2013; accepted September 23, 2013
Copyright © 2013 Masato Ohmi et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
In this paper, the dynamic analysis of mental sweating for sound stimulus of a few tens of eccrine sweat glands is per-
formed by the time-sequential piled-up en-face optical coherence tomography (OCT) images with the frame spacing of
3.3 sec. In the experiment, the amount of excess sweat can be evaluated simultaneously for a few tens of sweat glands
by piling up of all the en-face OCT images. Strong non-uniformity is observed in mental sweating where the amount of
sweat in response to sound stimulus is different for each sweat gland. Furthermore, the amount of sweat is significantly
increased in proportion to the strength of the stimulus.
Keywords: Optical Coherence Tomography; En-Face OCT Images; Mental Sweating; Sweat Gland; Sympathetic
Nerve
1. Introduction
Optical coherence tomography (OCT) enables cross sec-
tional imaging of tissues in vivo with micron scale reso-
lution, and now used for clinical diagnoses of retina dis-
eases in ophthalmology and arteriosclerosis in circulatory
medicine [1-3]. Besides the clinical applications, OCT
was applied for brain science, in which the nerve re-
sponse was detected by the OCT signals [4]. Recently,
we demonstrated the dynamic OCT of skin physiology
including the dynamics of sweat glands and peripheral
ve ssels was tr ack ed by time-seq uen tial OCT i ma ge s [5-7].
We discussed in detail mental sweating where mental or
physical stress was applied to a subject to accelerate ex-
cess sweating. When a sound stress was used, we found
internal mental sweating without ejection of excess sweat
to the skin surface for evaluation of the nerve activity [8].
In our previous work, the dynamic OCT analysis of
mental sweating of a single eccrine sweat gland was
made using the time-domain OCT (TD-OCT) [5,8]. A lot
of eccrine sweat glands align along the h ill of fingerprint
on human fingertips with the density of several hundred
glands in cm2. Therefore, the 3-D image construction
method with the so-called maximum intensity projection
(MIP) of B-mode OCT images is proposed for in vivo
dynamic analysis of mental sweating [9]. By use of the
fast speed swept-source OCT (SS-OCT), we demonstrate
the dynamic OCT possible for a few tens of eccrine
sweat glands. In this paper, the dynamic analysis of men-
tal sweating for sound stimulus of a few tens of eccrine
sweat glands is performed by the time-sequential piled-
up en-face OCT images with the frame spacing of 3.3
sec.
2. Materials and Methods
In the dynamic analysis of mental sweating, the piled-up
en-face OCT images are obtained time-sequentially for
simultaneous tracking of the sweating dynamics of as
many sweat glands as possible. The frame spacing of the
time-sequential OCT imaging must be a few seconds. In
the experiment, the swept-source (SS) OCT (Thorlabs
OCM 1300SS) is used for the in vivo 3-D imaging of
eccrine sweat glands on human fingertips, where the im-
age resolution (or coherence length) is 12 mm with <50
frames/s at the center wavelength of 1.325 mm. The il-
luminating laser power on a human fingertip is 4 mW or
less. The image construction method for the en-face OCT
of a group of sweat glands is shown in Figure 1. 128
OCT images in the x-z plane are obtained with a spacing
of 12.5 mm over the distance of 1.6 mm along the y di-
rection, as shown in Figure 1(a), where each OCT image
size is 2.0 × 1.5 mm2 with the pixel size of 12.5 × 5.9
mm2. The imaging time is 3.3 s which is the frame spac-

M. OHMI ET AL.
24
x
z
y
400m
(a) (b)
x
zy
400m
2.0 mm
1.6mm
400m
x
y
A1, A2, A3, A4, A5
B1, B2, B3, B4, B5
C1, C2, C3, C4, C5
D1, D2, D3
(c)
Figure 1. Image construction of en-face OCT. (a) 128 OCT
images in the x-z plane are obtained with a spacing of 12.5
mm along the y direction; (b) The en-face OCT images in
the x-y plane are extracted with the slice spacing of 5.9 mm,
(c) Piled-up en-face OCT image of where nineteen eccrine
sweat glands were imaged in the area of 2.0 × 1.6 mm2.
ing of the time-sequential piled-up en-face OCT images.
From the 128 B-mode OCT images, the en-face OCT
images in the x-y plane are extracted with the slice spac-
ing of 5.9 mm, as shown in Figure 1(b), where the num-
ber of en-face OCT images is 100 or more in epidermis.
In the en-face OCT, the pixel size is 12.5 mm which is a
proper image resolution for clear imaging of the spiral
lumen of eccrine sweat glands. All en-face OCT images
along the spiral lumen in stratum corneum of epidermis
are piled up to evaluate the amount of excess sweat. In
the resulting piled-up en-face OCT image, as shown in
Figure 1(c), the amount of excess sweat can be evaluated
simultaneously for seventeen eccrine sweat glands which
align along four lines of the fingerprint on a human fin-
gertip.
3. Experimental Results
3.1. Simultaneous Tracking of Mental Sweating
of a Few Tens of Sweat Glands by Dynamic
OCT
The dynamic OCT analysis was made for mental sweat-
ing of a group of eccrine sweat glands in the area of 2.0 ×
1.6 mm2 on the middle-finger tip, where a subject was a
23-year-old male. In the experiment, after confirmation
of the resting state of the subject, mental stress is applied
to the volunteer where the stress is unpleasant sound of
breaking glass for 0.5 sec at a sound level of 90 dB. Fig-
ure 2 show time-sequential piled-up enface OCT images
with the frame spacing of 3.3 sec. In the sweat glands,
marked by a yellow circle, the reflection light intensity
increases suddenly in response to the sound stress.
The nineteen sweat glands are also classified by four
lines of the fingerprint. Figure 3 shows time variation of
the reflection light intens ity for the sweat glands from A1
to A5. In our previous study, an instantaneous amount of
sweat stored in the sweat glands can be evaluated quan-
titatively by summatio n of the reflection light in tensity o f
all pixels included in the spiral lumen [8]. These five
sweat glands are active, but there is large difference in
the amount of the stored sweat in the spiral lumen. It is
thus found that the response to mental stress is different
for each sweat gland even though the sweat glands are
aligned to each other. Furthermore, Figure 4 shows the
time integrated value of the reflectio n light intensity dur-
ing the experiment indicated by the red bars. These val-
ues are corresponding to the total excess sweat. From
these results, strong non-unifor mity is observed in mental
sweating where the amount of excess sweat in response
to sound stress is different for each sweat gland.
3.2. Influence of the Experience of the Sound
Stimulus
In the next experiment, we consider the influence of the
experience of the sound stimulus. The dynamic analysis
for mental seating of sweat glands was performed for two
times using the same experimental protocol of Figure 2,
where a subject was a 23-year-old male. In this experi-
ment, the sweating dynamics of sixteen eccrine sweat
glands were measured simultaneously. Figure 5 show
the time variation of the total reflection light intensity by
application of the sound stimulus of the first and second
times. There is almost same in the response to the sound
stimulus. In addition, the time integrated value of the
reflection light intensity is indicated by the red and the
pink bars in Figure 6. The values corresponding to the
total excess sweat are almost equal. These results suggest
that there is no influence of the experience of the sound
50 s62.7 s138.6 s
400m
･･･
･･･
Sound stim ulu s
Sound s tim ulus（90 dB ）
50
start end
100
Time（s）3000
0 s
Resting state
Figure 2. Experimental protocol and time-sequential piled-
up en-face OCT images with the frame spacing of 3.3 sec.
Open Access OPJ

M. OHMI ET AL.
Open Access OPJ
25
2.4
1.6
0.8
0100 200 300
Sig nal int ensity（×10
4
）
Tim e ( s)
2.4
1.6
0.8
0100 200 300
2.4
1.6
0.8
0100 200 300
400m
A1 A2
A3 A4 A5
A1 A2 A3 A4 A5
Stimulus Stimulus
Stimulus
Stimulus
Stimulus
2.4
1.6
0.8
0100200 300
2.4
1.6
0.8
0100200 300
Time (s)
Tim e ( s)
Tim e ( s)
Tim e ( s)
Signal intensity（×10
4
）
Figure 3. Time variation of the reflection light intensity of the sweat glands, corresponding to the amount of excess sweat in
response to the sound stress.
stimulus to the subject.
3.0
1.5
0A1 A2 A3 A4 A5B1 B2 B3B4C1C2C3 C4C5D1 D2D301B5
A1, A2, A3, A4, A5
B1, B2, B3, B4, B5
C1, C2, C3, C4, C5
D1, D2, D3
01
400m
Time integrated value of the
ref lec t ion light int ens it y （×10
6
）
Sweat gland
3.3. Variation of the Amount of Mental Sweat
for the Different Sound Stimulus
Finally, we consider the variation of the amount of sweat
for different sound levels. The dynamic analysis for men-
tal seating of sweat glands was performed two times,
where the fir st stimulus of sound lev el was 90 dB and th e
second sound stimulus was 60 dB. Figure 7 show the
time variation of the total reflection light intensity. There
is large difference of time variation of the reflection light
intensity of the sweat glands between 90 dB and 60 dB of
the sound stimulus. The time integrated value of the re-
flection light intensity is also indicated b y the red and the
blue bars in Figure 8. The values corresponding to the
total excess sweat are significantly increased in propor-
tion to the sound levels. This result indicates that the ac-
tivity of the symphathetic nerve is proportional to the
strength of the sound stimulus.
Figure 4. Time integrated values of the reflection light in-
tensity, corresponding to the total amount of excess sweat.
Signal intensity（×10
4
）
3.0
2.0
1.0
0
3.0
2.0
1.0
0
3.0
2.0
1.0
3.0
2.0
1.0
100 200 300
Time (s)
A3
C2 D4
B3
First
Second
100 200 300
0100200300 0100 200300
StimulusStimulus
4. Discussion and Conclusions
We have demonstrated the dynamic OCT analysis of
mental sweating of sweat glands on a human fingertip.
We have proposed a novel method for evaluation of the
amount of excess sweat in response to stress, where the
en-face OCT images of the sweat gland are constructed
by the 128 B-mode OCT images. Amount of sweat can
be evaluated simultaneously for a few tens of sweat
glands by piling up of all the en-face OCT images. The
dynamic analysis of mental sweating is performed by the
time-sequential en-face OCT images with the frame
spacing of 3.3 sec.
Signal intensity（×10
4
）
Time (s)
Time ( s)Tim e (s)
Figure 5. Time variation of the reflection light intensity by
application of the sound stimulus of first and second.

M. OHMI ET AL.
26
Time integrated value of the
reflection light intensity（×106）
A1 A2 A3 A4 B1 B2 B3 C1 C2 C3 C4C5 D1 D2D3 D4
0
First
Second
0.3
0.6
0.9
1.2
1.5
A1, A2, A3, A4
B1, B 2 , B3
C1, C2, C3, C4, C5
D1, D2, D3, D4
Sweat gland
Figure 6. Time integrated values of amount of sweat stimu-
lated by application of the sound stimulus of first and sec-
ond times.
3.0
2.0
1.0
0
3.0
2.0
1.0
0
100 200 300
Tim e ( s)
100 200 300
A2 B2
Stimulus
Stimulus
90dB
60dB
Time (s)
3.0
2.0
1.0
0100200 300
C2
Stimulus
Time (s)
3.0
2.0
1.0
0100 200 300
D2
Stimulus
104)
X10
Ti me ( s)
Signal intensity (X
Signal intensity (4)
Figure 7. Time variation of the reflection light intensity by
application of the sound stimulus of 90 dB and 60 dB.
A1 A2 A3 A4 B1 B2 B3 B4 B5 C1C2C3C4 C5D1 D2D3 D4
0
2.0
4.0
6.0
8.0
90dB
60dB
A1, A2, A3, A4
B1, B2, B3, B4, B5
C1, C2, C3, C4, C5
D1, D2, D3, D4
Sweat gland
Time integrat ed value of the
ref lec tion light int ens ity （×10
6
）
Figure 8. Time integrated values of amount of sweat stimu-
lated by application of the sound stimulus of 90 dB and 60
dB.
From our experimental results, there are some inter-
esting results of mental sweating in sweat glands on a
human fingertip. 1) Strong non-uniformity is observed in
mental sweating where the amount of excess sweat in
response to sound stress is different for each sweat gland.
The non-uniformity may be necessary to adjust as pre-
cisely the total amount of excess sweat as possible
through the sympathetic nerve in response to strength of
the stress. 2) There is no influence of the experience of
the sound stimulus to the volunteer. Our experimental
protocol can be used frequently. 3) The amount of excess
sweat of eccrine sweat glands is increased in proportion
to the strength of the stimulus. This result suggests that
the mental sweating varies quantitatively according to the
stimulus.
5. Acknowledgements
This research was partially supported by Grant-in-Aid for
Scientific Research (C) (2 5350528) from the Japan Soci-
ety for the Promotion of Science (JSPS) and Industrial
Technology Research Grant Program from New Energy
and Industrial Technology Development Organization
(NEDO) of Japan.
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