10.5826/dpc.1301a58
Introduction: The interpretation of colors is essential in the dermoscopic evaluation of skin lesions. The same blue color on white dermoscopy may indicate blood or pigment deep in the dermis. Skin parameter maps, generated from multispectral dermoscopic images, allow to more clearly visualize specific skin structures such as pigment distribution (pigment map) and vasculature (blood map).
Objectives: Aim of this research is to investigate whether skin parameter maps can be used to objectively identify and distinguish the presence of pigment and blood.
Methods: We retrospectively analyzed 24 blue naevi and 79 angiomas. The skin parameter maps of each of the lesions were independently reviewed by 3 expert dermoscopists, in the absence of the regular white-light dermoscopic image.
Results: All the observers provided high levels of diagnostic accuracy for blue naevus and angioma based on skin parameter maps alone, and the dermoscopic diagnosis was considered substantially reliable because of the 79% of diagnostic K agreement. Percentages of blue naevi and angiomas that showed respectively deep pigment and blood were very high at 95.8% and 97.5%. There was a percentage of lesions that counterintuitively showed blood in blue naevi (37.5%) and deep pigment in angiomas (28.8%).
Conclusions: Skin parameter maps based on multispectral images can help to objectify the presence of deep pigment or blood in blue naevi and angiomas. Application of these skin parameter maps could help in the differential diagnosis between pigmented and vascular lesions.
text/xml
2160-9381
2536
en
Marjan Garmyn
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
skin parameter maps
Can Multispectral Dermoscopy Help In Distinguishing Blue Color?
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Original Article
2023-01-31
2022-05-11
2023-01-31
2023-02-27
e2023058
Dermatol Pract Concept
Introduction: The interpretation of colors is essential in the dermoscopic evaluation of skin lesions. The same blue color on white dermoscopy may indicate blood or pigment deep in the dermis. Skin parameter maps, generated from multispectral dermoscopic images, allow to more clearly visualize specific skin structures such as pigment distribution (pigment map) and vasculature (blood map).
Objectives: Aim of this research is to investigate whether skin parameter maps can be used to objectively identify and distinguish the presence of pigment and blood.
Methods: We retrospectively analyzed 24 blue naevi and 79 angiomas. The skin parameter maps of each of the lesions were independently reviewed by 3 expert dermoscopists, in the absence of the regular white-light dermoscopic image.
Results: All the observers provided high levels of diagnostic accuracy for blue naevus and angioma based on skin parameter maps alone, and the dermoscopic diagnosis was considered substantially reliable because of the 79% of diagnostic K agreement. Percentages of blue naevi and angiomas that showed respectively deep pigment and blood were very high at 95.8% and 97.5%. There was a percentage of lesions that counterintuitively showed blood in blue naevi (37.5%) and deep pigment in angiomas (28.8%).
Conclusions: Skin parameter maps based on multispectral images can help to objectify the presence of deep pigment or blood in blue naevi and angiomas. Application of these skin parameter maps could help in the differential diagnosis between pigmented and vascular lesions.
Marjan Garmyn
2023/01/31
10.5826/dpc.1301a58
e2023058
Department of Dermatology, KU Leuven, Belgium 
2160-9381
skin parameter maps
en
e2023058
Costa J, Ortiz-Ibañez K, Malvehy J, et al. Dermoscopic patterns of melanoma metastases: interobserver consistency and accuracy for metastasis recognition. British Journal of Dermatology, 2013 169(1), pp.91-99.
Can Multispectral Dermoscopy Help In Distinguishing Blue Color?
https://dpcj.org/index.php/dpc/article/download/2536/1955
                     Can Multispectral Dermoscopy Help
                        In Distinguishing Blue Color?
           Laudine Janssen1, Sofie Van Kelst1, Bart Diricx2, Tom Kimpe2, Jorien Papeleu3,
                      Evelien Verhaeghe3, Lieve Brochez3, Marjan Garmyn1


1 Department of Dermatology, KU Leuven, Belgium
2 Barco healthcare, Kortrijk, Belgium
3 Department of Dermatology, UZ Gent, Belgium



Key words: dermoscopy, blue naevus, angioma, multispectral, skin parameter maps
Citation: Janssen L, Van Kelst S, Diricx B, et al. Can Multispectral Dermoscopy Help In Distinguishing Blue Color? Dermatol Pract
Concept. 2023;13(1):e2023058. DOI: https://doi.org/10.5826/dpc.1301a58
Accepted: May 31, 2022; Published: January 2023
Copyright: ©2023 Janssen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use,
distribution, and reproduction in any medium, provided the original authors and source are credited.
Funding: None.
Competing Interests: None.
Authorship: All authors have contributed significantly to this publication.
Corresponding Author: Marjan Garmyn MD, PhD, Department of Dermatology, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
Tel: +3216337950 Fax: +3216337951 E-mail: marjan.garmyn@kuleuven.be




  ABSTRACT             Introduction: The interpretation of colors is essential in the dermoscopic evaluation of skin lesions.
                       The same blue color on white dermoscopy may indicate blood or pigment deep in the dermis. Contrary
                       to white dermoscopy, multispectral dermoscopy uses different wavelengths of light to illuminate a
                       ­lesion and is able to decompose the dermoscopic image into individual maps that allow to more clearly
                        visualize specific skin structures such as pigment distribution (pigment map) and vasculature (blood
                        map). These maps are called skin parameter maps.
                       Objectives: The aim of this research is to investigate whether skin parameter maps can be used
                       to ­objectively identify and distinguish the presence of pigment and blood, by using blue naevi and
                       ­angiomas as models for respectively pigment and blood.
                       Methods: We retrospectively analyzed 24 blue naevi and 79 angiomas. The skin parameter maps
                       of each of the lesions were independently reviewed by 3 expert dermoscopists, in the absence of the
                       ­regular white-light dermoscopic image.
                       Results: All the observers provided high levels of diagnostic accuracy for blue naevus and a­ ngioma
                       based on skin parameter maps alone, and the dermoscopic diagnosis was considered s­ubstantially
                       reliable because of the 79% of diagnostic K agreement. Percentages of blue naevi and angiomas
                       that showed respectively deep pigment and blood were very high at 95.8% and 97.5%. There was a
                       ­percentage of lesions that counterintuitively showed blood in blue naevi (37.5%) and deep pigment
                        in angiomas (28.8%).




Original Article | Dermatol Pract Concept. 2023;13(1):e2023058                                                                      1
                      Conclusions: Skin parameter maps based on multispectral images can help to objectify the presence
                      of deep pigment or blood in blue naevi and angiomas. The application of these skin parameter maps
                      could help in the differential diagnosis between pigmented and vascular lesions.




Introduction                                                       with good clinical practice guidelines. The research protocol
                                                                   was approved by the Ethics Committee of Leuven (s60193).
The interpretation of colors is essential in the dermoscopic       A deep pigment and blood parameter map was created for
evaluation of skin lesions. These colors result from different     all the lesions, aiming to highlight respectively the presence
chromophores in the skin, such as pigment and blood. De-           of deep pigment or blood. These two skin parameter maps
pending on the location of pigment in the skin, white light        of each lesion were independently reviewed by 3 expert der-
dermoscopy reveals the following colors: brown (pigment at         moscopists (EV, LB and MG).
the dermo-epidermal junction), black (pigment in the stratum
corneum or superficial epidermis), gray (pigment in the pap-       Setting
illary dermis) or blue (pigment in the reticular dermis). A red,   The images of the skin parameter maps (deep pigment and
blue or purple color represents blood [1]. Consequently, the       blood) were presented in a mixed order to the observers and
same blue color on white dermoscopy may indicate blood             scored blinded to the white light dermoscopic image or diag-
or pigment deep in the dermis [2]. In contrast to white light      nosis and without knowledge of any clinical data. In each case,
dermoscopy, multispectral dermoscopy uses different wave-          the presence of deep pigment and blood was semiquantitatively
lengths of light to illuminate a lesion. This technique is able    scored as absent or present. Additionally, participants were
to decompose the dermoscopic image into individual maps            asked to diagnose the lesion (blue naevus or angioma) based
that allow to more clearly visualize specific skin structures      on the multispectral images alone and to assess in which of
such as pigment distribution (pigment map) and vascula-            the two skin parameter maps the signal was highlighting most.
ture (blood map). These visualizations can be generated in
real-time and are called skin parameter maps (SPM) [3]. A          Outcomes
further distinction between superficial and deep pigment can
                                                                   The primary outcome measure was the rate of lesions in
be made, based on their different spectral signature, which
                                                                   which a signal in the blood and/or pigment map was ob-
can be visualized with a superficial and deep pigment map.
                                                                   served. Secondary outcomes were correlation of intensity
                                                                   with a correct diagnosis, interobserver concordance and the
Objectives                                                         accuracy rate in predicting angioma versus blue naevus.

The aim of this research is to investigate whether skin pa-        Statistical Analysis
rameter maps can be used to objectively identify and dis-          The prevalence of pigment or blood was compared among
tinguish the presence of pigment and blood. We conducted           the 2 lesion groups (blue naevus, angioma) using the χ2 test.
a retrospective study on blue naevi and angiomas as proto-         All P values cited are two-sided, and values of P less than .05
types of lesions with, respectively, pigment deep in the der-      were considered statistically significant. Sensitivity and spec-
mis (melanin-producing melanocytes deep in the dermis) and         ificity for the diagnosis of the skin lesions were calculated
collection of capillaries in the dermis to validate the presence   for each observer as compared to clinical or histopatho-
of pigment or blood in skin parameter maps.                        logic diagnosis. The agreement between ratings made by 3
                                                                   expert dermoscopists (interrater reliability) was estimated
                                                                   using Fleiss’ kappa statistic with 95% confidence intervals.
Methods
                                                                   Statistical analysis was performed with SPSS statistics for
We retrospectively analyzed all dermoscopic images taken           ­Windows version 26 (IBM Corp).
of blue naevi and angiomas that were collected in two cen-
ters (UZ Leuven and UZ Gent) from February 2019 until
                                                                   Results
January 2020 using a handheld digital dermatoscope (Barco
Demetra®), after patients had given informed consent. Di-          Images of 103 lesions, of which 24 blue naevi and 79 angi-
agnosis was either histopathologically proven or made clini-       omas, were collected. Ten lesions (6 blue naevi and 4 angi-
cally (by LJ or SM). This study was conducted in accordance        omas) were histologically confirmed. For the other lesions,



2                                                                      Original Article | Dermatol Pract Concept. 2023;13(1):e2023058
the diagnosis was made clinically (by LJ or SM). An example           other 15.6% of cases, majority decision-making was used.
of skin parameter maps as shown to the observers is shown             As far as diagnosing blue naevi and angiomas based on the
in Figure 1. Out of the 24 blue naevi, 23 showed a signal on          skin parameter maps alone, a sensitivity of 81% (64 out of
the deep pigment map (95.8%), whereas in only 22 out of               79 angiomas diagnosed correctly) and a specificity of 100%
the 79 angiomas (28.8%) a signal on the deep pigment map              (24 out of 24 blue naevi diagnosed correctly) with an overall
was observed (p < 0.001). In 77 out of 79 angiomas (97.5%)            accuracy of 85.4% was reached. Of the 15 cases that were
a signal was detected in the blood map, versus 9/24 (37.5%)           diagnosed incorrectly, 7 of them were not answered unani-
in blue naevi (p < 0.001) (Table 1).                                  mously by the observers.
    Next, we checked if the intensity of the signal of the skin          An illustration of blood and deep pigment maps of two
parameter map correlates with the correct diagnosis. When             blue naevi and an angioma, in addition to the information
choosing the most intense signal between the two skin pa-             from regular white dermoscopy (which was not shown to
rameter maps, we found that in 20 out of the 24 blue naevi            the observers), is shown in Figure 2. In the skin parameter
(83.3%) the intensity of the signal was most pronounced               maps of Image A, only pigment is highlighted, as expected
in the deep pigment map. Of 79 angiomas, in 72 of them                in a blue naevus. In Image B, a collision between a blue nae-
(91.1%) the most intense signal was seen in the blood map.            vus and angioma, the angioma is highlighted in the blood
To determine if there was agreement between the answers               contrast map, whereas the blue naevus is highlighted in the
of the three experts a Fleiss’ kappa was made. Overall,               pigment contrast map. These two cases illustrate the possible
there was good agreement, κ = .792 (95% CI, .790 to .793).            use of these skin parameter maps to diagnose skin lesions.
84,5% of all questions (presence or absence of deep pigment           The use of skin parameter maps may not only be limited to
or blood, most highlighted skin parameter map and diagno-             blue naevi and angiomas, but could be useful in other types
sis) were answered unanimously by the three experts. In the           of skin lesions (e.g. basal cell carcinoma).




Figure 1. Skin parameter maps (left deep pigment map, right blood map) of a blue naevus (top row) and angioma (bottom row).



             Table 1. Absolute and relative frequencies of presence of deep pigment and blood
                         in the skin parameter maps of blue naevi and angiomas.
                                                   Lesion group                              χ2 test for comparisons among
  Skin parameter map            Blue naevus (n = 24)             Angioma(n = 79)                   lesion group, P value
 Deep pigment                         23 (95.8%)                   22 (28.8%)                              <.001
 Blood                                 9 (37.5%)                   77 (97.5%)                              <.001




Original Article | Dermatol Pract Concept. 2023;13(1):e2023058                                                                   3
Figure 2. White light dermoscopic image (left column), deep pigment map (middle column) and blood map (right column) of a blue naevus
(top row) and collision between a blue naevus and angioma (bottom row).




Discussion                                                          skin parameter maps could help to determine if the lesion
                                                                    is a vascular or pigmented lesion. Despite the fact that it
In this study, we investigated the use of skin parameter maps       was not an objective to use the skin parameter maps without
as a tool to semi-quantitively score the presence or absence        the corresponding white light image, this research indicates
of blood or deep pigment in skin lesions. We validated the          that the sensitivity and specificity are good when using skin
presence of blood and deep pigment, as indicated by high-           parameter maps on their own for these skin lesions. Our
lighted areas in the skin parameter maps in two types of skin       recommendation for the application of skin parameter maps
lesions: blue naevus and angioma.                                   in general practice would still be to use them in conjunction
    Three dermoscopy experts assessed the skin parameter            with the white light image.
maps of 103 lesions, of which 24 blue naevi and 79 angio-
mas, for presence or absence of deep pigment or blood, most
highlighted skin parameter map and diagnosis. All observers         Conclusion
provided high levels of diagnostic accuracy for blue naevus
                                                                    Skin parameter maps based on multispectral images can
and angioma based on skin parameter maps alone, and the
                                                                    help to objectify the presence of deep pigment or blood in
dermoscopic diagnosis was considered substantially reliable
                                                                    blue naevi and angiomas. Application of these skin param-
because of the 79% of diagnostic K agreement. Percentages
                                                                    eter maps could help in the differential diagnosis between
of blue naevi and angiomas that showed respectively deep
                                                                    pigmented and vascular lesions. These skin parameter maps
pigment and blood were very high at 95.8% and 97.5%.
                                                                    should be used complementary to regular dermoscopy, but
There is a percentage of lesions that counterintuitively
                                                                    assessment based on the skin parameter maps alone results
shows blood in blue naevi (37.5%) and deep pigment in an-
                                                                    in good diagnostic accuracy.
giomas (28.8%). The presence of vascularity in blue naevi
suggests a vascular component, which is reported in liter-
ature [2]. We have no explanation for the presence of deep          References
pigment in some angiomas, but further research on this will
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