Usability of optical coherence tomography, clinical
photography, thermal imaging, and laser speckle contrast imaging in the
evaluation of i.d. injections
Subjects were acclimatized in a temperature-controlled room (21°C) for
15 minutes with bare legs. The sequence of measurements was (starting
with the least invasive to minimize disturbance of the subsequent
measurements): (1) thermography; (2) cutaneous micro circulation; (3) 3D
photography; (4) multispectral imaging; and (5) skin morphology. Details
of skin imaging methods are described below.
Skin micro circulation was quantified by LSCI (PeriCam PSI NR system,
Perimed, Sweden). Laser speckle is the interference pattern returning
from erythrocytes, resulting in a speckle pattern that differs under
changes in blood flow (17). Recordings of 40 seconds were taken from a
distance of 15 cm with a reading frame of 7 by 7 cm. Analysis was
performed using the internal software (PimSoft, Perimed, Sweden) and
regions of interest were selected based on the most predominant
injection site reaction.
Skin temperature was quantified by infrared thermography (FLIR X6540sc
camera, FLIR Systems Inc., USA). After calibration for room temperature
using a black body, 10 second recordings were taken from a distance of
80 cm. Recordings were averaged for analysis.
Skin morphology was assessed by OCT (D-OCT VivoSight, Michelson
Diagnostics, UK). Thirty second scans were performed with a 6 mm
diameter probe. Three automatically calculated parameters were used to
quantify morphology (attenuation compensation, blood flow at depth and
skin roughness). Qualitative analysis was performed by two clinical
scientists with experience in analyzing D-OCT images.
Erythema and swelling were quantified using a multispectral camera
(Antera 3D, Miravex, Ireland), and a 3D stereophotogrammetry camera (3D
LifeViz, QuantifiCare, USA). The multispectral camera was placed over
the skin creating a closed environment with the lesion in the centre of
the frame. Erythema was measured using the CIELab *a value. CIELab is a
standardized quantitative method to discriminate colours using an
XYZ-axis system. CIELab *a value is represented on the red/green axis
and is correlated to skin erythema (18,19). Three-dimensional images
were taken from a distance of 20 cm with use of a guidance laser and
analyzed in imaging processing software (DermaPix Software,
QuantifiCare, Valbonne, France).