Application of thermal imaging to assess the superficial skin temperature distribution after local cryotherapy and ultrasound
Application of thermal imaging to assess the superficial skin temperature distribution after local cryotherapy and ultrasound
Ewa Boerner 0 1 2
Halina Podbielska 0 1 2
0 Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology , Wybrzez_e Wyspian ́skiego 27, 50-370 Wrocław , Poland
1 Faculty of Physiotherapy, University School of Physical Education , Al. I. J. Paderewskiego 35, 51-612 Wrocław , Poland
2 & Ewa Boerner
Thermal imaging is a safe, noninvasive, and quite low-cost technique that allows for the rapid and noninvasive recording of thermal radiation emitted by the human body. In recent years, it is increasingly used for physiotherapy monitoring. The main goal of the study was to compare the influence of two various treatments applied in two various orders, namely local cryotherapy (CRYO) and ultrasound therapy (US). The impact of combined therapies, applied in two various orders, was studied in terms of changes of the superficial temperature distribution on the front right thigh surface. The response to the therapy depending the treated persons' gender, along with a consensual reaction, was examined. The research material consisted of 30 healthy volunteers, 19-23-year old students, aged 19.93 (± 1.42). All treatments were performed at weekly intervals in the following order: in the first week, CRYO immediately followed by US, and in the second week, ultrasound immediately followed by local cryotherapy. All treatments were performed on the right quadriceps. The combined sequence of local cryotherapy and ultrasound therapy caused temperature decrease in the treated area regardless of their performance order. The temperature decrease considerably depends on the sequence of the applied treatments, and it was more significant after the ultrasound-cryotherapy sequence.
Thermal imaging; Ultrasound; Physiotherapy; Local cryotherapy
Body temperature is one of the most commonly used
indicators of health status in humans. Thermal imaging for
the superficial temperature measurement has been used
since the early 1960s in various fields. Recent technical
advances in infrared cameras open new possibilities [
Thermal imaging is a safe, noninvasive, and quite
inexpensive technique that allows for the monitoring of the
superficial body temperature for various applications [
Furthermore, thermal imaging enables to specify
temperature changes not only in terms of values, but also in terms
of spatial distribution, what can be exploited in various
biomedical applications [
]. The spatial distribution of
temperatures is associated with the spatial distribution of
the energy emitted from the examined body. The thermal
imaging enables to determine the temperature in each point
on the surface basing on the recording of the spatial
distribution of the emitted energy.
In physical medicine, various physical stimuli to evoke
beneficial effects in the human body are used. Many
physical agent modalities cause changes in the superficial
and deep tissue temperature [
]. Properly chosen
physical agent should lead to a specific reaction with a desired
effect. When recommending physical treatment, two or
three modalities are very often administered to be executed
in one session. These treatments, causing various thermal
effects, are often performed one after another . As a
general rule, the order of such polytherapy is random,
because there is little information regarding the correct
sequence. These physical treatment modalities may act
synergistically or antagonistically one to another.
Individual characteristics of a patient, such as sex and age, or even
body mass, should also be taken into consideration.
Therefore, temperature distribution after the application of
the selected physical factors, change in tissue temperature
values and, in particular, the period after which the
temperature returns to its initial value, should be assessed.
Local cryotherapy and ultrasound therapy (called
sonotherapy) are applied in physical treatment for their
analgesic and anti-inflammatory effects. These two
treatments are often recommended in one session. Local
cryotherapy is the stimulating application of low
temperatures around - 100/ C or slightly below for 1–3 min.
Cryotherapy supports basic treatment and facilitates
kinesiotherapy. From the clinical standpoint, local cryotherapy
has analgesic, anti-inflammatory, antioedematous effects
and reduces muscle tone [
In sonotherapy, the ultrasound waves with frequency
between 0.8 and 3.0 MHz and power density not exceeding
3 W/cm2 are used as physical agent. Many biophysical
changes comprising thermal, mechanical, and
physicochemical effects occur in the body under the influence of
the ultrasonic waves. These include analgesic activity,
muscle relaxing, vasodilation, stabilizing the sympathetic
nervous system, inhibiting the inflammatory processes
]. The therapeutic effect of physiotherapy may be
monitored by analyzing temperature changes on the
superficial tissues [
The aim of this study was to compare the impact of the
sequence of local cryotherapy and sonotherapy, applied
immediately one after another, on the superficial
temperature distribution on the front right thigh surface. The
impact of combined therapies, applied in two various
orders, was studied in terms of changes of the superficial
temperature distribution on the front right thigh surface.
The responses to the therapy depending the treated
persons’ gender, along with a consensual reaction, were
The study group consisted of 30 healthy, nonsmoking,
volunteers including 17 women (57%) and 13 men (43%),
aged 19–24 years (Table 1). Participants enrolled into the
study were informed about the experiment and gave their
consent to participate in the research. In order to conduct
the study, approval from the Senate Commission of
Bioethics of the Wrocław University School of Physical
Education in Wroclaw was obtained on March 19, 2012.
Regarding the body mass index (BMI), these groups
were quite homogenous: BMI did not vary significantly
statistically in the examined women and men (t = 0.59,
p = 0.56 [ 0.05). All examined persons were
characterized by a BMI value within the norm (18.8–24.9)
Each volunteer was subjected to treatments in the
following order: in the first week local cryotherapy treatment,
directly followed by ultrasound. The sequence was named
CRYO–US. In the second week, ultrasound immediately
followed by local cryotherapy was applied. The sequence
was called US–CRYO. The body area subjected to
physiotherapeutic treatments was the right quadriceps. The
treated place on the thigh was situated 10 cm above the
kneecap top and 15 cm below the groin.
Kriotel apparatus from Wrocław, Poland, was used for
local cryotherapy. The treatment lasted 3 min. The
temperature at the nozzle outlet was - 156 C, reaching
approximately - 100 C on the skin. The ultrasound was
applied by means of Ionoson apparatus from Physiomed,
Germany. The dose applied was 0.6 W/cm2 with 1 MHz
frequency, and the treatment lasted 6 min. The coupling
substance was liquid paraffin, Avena, Poland. The
physiotherapeutic treatments were executed by the same person
in accordance with the generally accepted rules. All
experiments were performed in the same therapy room and
under the same conditions. The room temperature was
24 ± 1.0 C, and the humidity was 39 ± 1.0%.
Temperature changes were examined by means of a
thermal imaging camera FLIR T335. Prior to the study, the
volunteers were not subjected to any intense physical strain
or physical treatments. Each participant adapted to the
conditions for a period of 20 min, by exposing the
uncovered treated area to the room conditions. Infrared
images were recorded in a standing position at the distance
1.2 m from the camera. The optical axis of the camera was
perpendicular to the center of the treated spot. Five thermal
images were recorded for each participant in the first week
and in the second week.
For each image, a region of interest ROI was
determined, corresponding to the treatment area, as described
above. The mean, maximal, and minimal temperatures in
ROI were analyzed. As the obtained data follow normal
distribution, the Student’s t test for dependent samples was
used for statistical analysis. The influence of gender
dimorphism was analyzed by means of Student’s t test for
independent samples. The correlation of the results with
consensual reaction was calculated with the help of
Pearson’s coefficient r. For statistical analysis, the
STATISTICA 10 software was used.
Results and discussion
The relationship between the temperature changes and the treatments sequence
Exemplary thermal images captured in the examination are
depicted in Figs. 1 and 2.
The recorded thermal images, and further the data, were
marked in the following manner: T1—before treatment,
T2—immediately after the first treatment,
T3—immediately after the second treatment, T4—15 min after the
second treatment, T5—30 min after the second treatment.
Thermal images in the rainbow pseudo-color scale were
stored on a computer disk as the files in JPG format with a
size of 340 9 240 pixels. The Therma CAM Researcher
2.9 software was used for analysis to find out mean,
minimal, and maximal values of temperatures in the
rectangular region of interest ROI.
The analysis of the initial temperatures on the right thigh
front surface before treatments showed that these values
were similar and did not differ significantly, independent of
the examined sequence: the CRYO–US or the US–CRYO
order. However, the significant changes were observed
after treatments. Various therapy sequences resulted in
various changes of the temperature (Fig. 3). Directly, after
both treatments, regardless of their order, the mean thigh
surface temperature changed in all examined persons (T2).
The significant decrease in the temperature after CRYO–
US sequence was observed (T2 dropped from 31.5 to
24.3 C). For the US–CRYO sequence, slightly higher
temperature was seen; however, this change was not
statistically significant (T2 raised from 31.7 to 31.9 C). The
mean T3 temperature was lower than mean T1. No further
decrease was observed after the second treatment;
however, T3 for the sequence US–CRYO was 5.1 C lower
than T3 for the CRYO–US order.
One can also see that the decrease in the examined
temperature due to the US–CRYO treatment lasted longer
than in the case of CRYO–US. After the treatment, an
increase in the mean temperature between T3 and T4 is
observed. However, it is higher for the US–CRYO
sequence (from 25.2 to 30.4 C), while for CRYO–US it
varies from 30.2 to 31 C. Table 3 depicts the examined
changes, showing these statistically significant, for the
significance level p = 0.001. After last treatment (T3) and
15 min later (T4), the mean temperatures differences were
statistically significant. After 30 min (T5), the difference in
temperatures caused by CRYO–US and US–CRYO was
not statistically significant (p = 0.056).
The relationship between thigh surface temperature changes and gender
The same analyses were performed for male and female
participants separately. Before the treatment, the mean
right thigh surface temperature in men was slightly higher
than the mean thigh surface temperature in women. The
difference between the initial mean values was 1.1 C, and
it was statistically significant. No statistical differences
between men and women were found when analyzing the
therapy results. The trend was the same as for the entire
group, meaning the statistically significant differences
observed after last treatment (T3) and 15 min later (T4).
However, in each time point, no statistical difference
between genders was seen. The initial difference 1.1 C
between mean temperatures in men and women was similar
in the entire experiment. No statistically significant
differences in reaction to the therapy were found in the
studied group of young volunteers (Fig. 4).
For various stimuli, a consensual response may be
observed on contralateral side of the body, when the other
side has been stimulated. For example, such reaction is
seen in human eye pupil after the light exposure. Here, we
examined mean temperature changes on the left thigh after
the exposure of the right thigh to the US–CRYO and
CRYO–US treatment sequences, to find out whether there
is any consensual reaction.
As it was shown above, immediately after the treatment,
the mean temperature of the right thigh was lower than the
initial one (before treatment). The positively correlated
consensual response should also follow this trend.
However, it was observed only in some of the subjects, only
when the temperature difference was higher than - 2 C. It
was more evident in the case of the CRYO–US sequence
than in the US–CRYO sequence. Thus, the consensual
reaction appeared to be more evident in the CRYO–US
sequence. The correlation factor of the surface temperature
changes on both thighs after treatments and on the right
thigh was equal r = 0.77 and was statistically relevant
(p \ 0.001), whereas after the US–CRYO sequence, the
correlation was significantly weaker, although it was also
statistically relevant (r = 0.36. p = 0.047).
Studying this effect in women and men separately, it
was stated that in women for CRYO–US sequence, the
reaction is more visible, since r = 0.90 (p = 0.000001),
Student’s t test
whereas in men the correlation is weak and statistically
insignificant: r = 0.46 (p = 0.11) (Fig. 5a, b,
The opposite effect was observed in case of US–CRYO
sequence (see Fig. 6a, b). In women, the correlation was
weak and statistically insignificant: r = 0.34 (p = 0.18),
whereas in men the higher correlation was observed
r = 0.56 and it was statistically significant (p = 0.046).
Summarizing, quite similar consensual effect was
observed in men for both therapy sequences, while in
women that was higher for CRYO–US sequence.
Consensual reaction may be an important factor in
physiotherapeutic practice, since in some circumstances it can be
regarded as an additional benefit or in other cases, it may
negatively influence the therapeutic outcomes or even may
be contraindicated. Physiotherapeutic stimuli are, e.g., not
recommended in cancer patients in places near the
pathological sites. But even remote application may evoke
contralateral response. The consensual reaction is always
less pronounced than the local one, directly exposed to the
physical agent. In examined therapy sequences, this effect
was minimal. Interesting that it was gender dependent,
what may be explained by differences in fat distribution
and skin vasculature.
In physical medicine, treatments applying various
physical stimuli, e.g., thermal, electrical, optical,
mechanical, or magnetic stimuli, are used. Most of them have
thermal effects, resulting in a change of the temperature in
the treated area [
]. Thermal imaging is one of the most
sufficient methods of superficial temperature distribution
There are some publications describing the application
of thermal imaging for the assessment of the physical
treatment effectiveness [
]. However, as so far, no
studies are reported describing temperature changes after
combination of selected physical treatments and examining
time interval, in which the temperature returns to initial
values. To our best knowledge, the presented study was not
described in the literature.
On the basis of the performed research, it was found that
cryotherapy combined with ultrasound in one therapeutic
session decreases the temperature in the treated area,
irrespectively of the sequence of their performance. However,
it was found that the temperature decrease depends
significantly on the sequence of the applied treatments, and it
was 5 C higher after the US–CRYO sequence than
CRYO–US. The difference between the mean values
clearly decreased within 15 min after the treatments, but
still the mean thigh surface temperature after the US–
CRYO treatment sequence was significantly lower than the
mean temperature after the CRYO–US sequence. On the
other hand, 30 min after the treatments, the mean surface
temperature values were not different in terms of statistical
relevance, but they still remained lower than the initial
values, regardless of the order of the performed treatments.
Cryotherapy applied as a second treatment caused a higher
When examining a consensual reaction, it was found
that applied treatments cause a consensual reaction on the
contralateral thigh and it was much more visible after
applying the CRYO–US sequence. Here, the gender
dependence was observed.
The obtained results may contribute to better planning of
the physical treatment, especially in cases where more than
one therapy is recommended. Both examined treatments
have an anti-inflammatory and analgesic effects. However,
they cause different reactions. Therefore, when
kinesiotherapy is administered, cryotherapy should be the last
treatment, since the temperature decrease lasted longer,
facilitating movement and exercises.
Further studies regarding surface temperature
distribution in other physical treatments and their combination
should be conducted in order to establish a proper
personalized therapy, which is more recommended than the
standard protocols [
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