Chapter 12
Selected Clinical Applications
of Functional PPGI Perfusion Mapping
in Dermatology
Claudia Blazek and Vladimir Blazek
Abstract Assessment of dermal blood perfusion before and after standardized clinical skin tests is mostly provided by clinical inspection. This chapter aims to supplement this qualitative assessment with the Photoplethysmography Imaging (PPGI)
method. Our experimental PPGI system contains a light source consisting of multiple
LEDs that illuminate a larger part of the skin surface with selective light intensity
and wavelength. The light intensity scattered back from the skin is detected by a
highly sensitive CCD camera (UltraPix FE250) acting like a PPG detector array to
detect weak light modulation caused by the arterial pulsation. Our setup utilizes a
silicon frame-transfer CCD chip with a pixel resolution of 512x512, cooled down to
-40 °C to reduce the readout noise. Depending on the camera lens, the observed skin
region can range from a few square centimeters to whole extremities, observed from
a distance of 50 cm. After the recording of a short video sequence (e.g., 120 s) of
the skin surface, the operator can choose different regions of interest (ROIs acting
like the “virtual sensors”). Then the time-dependent backscattered light intensity
of the ROIs is calculated. The resulting signals visualize the arterial blood volume
changes in the respective skin regions. Fourier and Wavelet Transforms, artifact
reduction algorithms, and algorithms for point-to-point multidimensional perfusion
calculation and visualization (functional perfusion mapping) provide a sound basis
for quantified clinically relevant skin perfusion studies. Our first clinical trials validate the diagnostic potential of the proposed method in dermatology (especially at
skin allergy testing) and dermato-angiology.
C. Blazek (B)
The Private Clinic of Dermatology, Limmatquai 80, 8001 Zurich, Switzerland
e-mail: claudia.blazek@gmx.net
V. Blazek
Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH
Aachen University, Aachen, Germany
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_12
207
Selected Clinical Applications
of Functional PPGI Perfusion Mapping
in Dermatology
Claudia Blazek and Vladimir Blazek
Abstract Assessment of dermal blood perfusion before and after standardized clinical skin tests is mostly provided by clinical inspection. This chapter aims to supplement this qualitative assessment with the Photoplethysmography Imaging (PPGI)
method. Our experimental PPGI system contains a light source consisting of multiple
LEDs that illuminate a larger part of the skin surface with selective light intensity
and wavelength. The light intensity scattered back from the skin is detected by a
highly sensitive CCD camera (UltraPix FE250) acting like a PPG detector array to
detect weak light modulation caused by the arterial pulsation. Our setup utilizes a
silicon frame-transfer CCD chip with a pixel resolution of 512x512, cooled down to
-40 °C to reduce the readout noise. Depending on the camera lens, the observed skin
region can range from a few square centimeters to whole extremities, observed from
a distance of 50 cm. After the recording of a short video sequence (e.g., 120 s) of
the skin surface, the operator can choose different regions of interest (ROIs acting
like the “virtual sensors”). Then the time-dependent backscattered light intensity
of the ROIs is calculated. The resulting signals visualize the arterial blood volume
changes in the respective skin regions. Fourier and Wavelet Transforms, artifact
reduction algorithms, and algorithms for point-to-point multidimensional perfusion
calculation and visualization (functional perfusion mapping) provide a sound basis
for quantified clinically relevant skin perfusion studies. Our first clinical trials validate the diagnostic potential of the proposed method in dermatology (especially at
skin allergy testing) and dermato-angiology.
C. Blazek (B)
The Private Clinic of Dermatology, Limmatquai 80, 8001 Zurich, Switzerland
e-mail: claudia.blazek@gmx.net
V. Blazek
Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH
Aachen University, Aachen, Germany
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_12
207