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Evaluation of facial blood flow using three-dimensional scanning

Evaluation of facial blood flow using three-dimensional scanning



Evaluation of facial blood flow using three-dimensional scanning




British Journal of Oral and Maxillofacial Surgery, 2017-11-01, Volume 55, Issue 9, Pages 974-976, Copyright © 2017 The British Association of Oral and Maxillofacial Surgeons


Abstract

The Vectra X3 3-dimensional face scanner allows us to visualise the erythema of superficial layers of skin in addition to its regular scanning functions. The aim of our study was to find out whether changes we provoked in the circulation of the skin would be registered and displayed by the face scanner. We measured the circulation in the skin of the cheeks of 20 volunteers with a face scanner, a laser Doppler device, and a skin pigmentation analyser before and after the application of a nitric oxide cream. The results were compared in terms of grey tones, local concentrations of haemoglobin, and erythema. All methods showed significant changes (p < 0.001) before and after application of the cream. The study proved that the Vectra X3 recognises changes in skin circulation and displays them in a simple and evident way.


Introduction

Over the last few years, 3-dimensional face scanners have become a popular device and an important component in daily clinical routines, alongside tools that monitor skin perfusion.

To improve clinical routines, devices that combine diverse functions are needed. A device that is supposed to fulfil these requirements is the Vectra X3 3D face scanner (Canfield Scientific Incorporated, Fairfield, NJ, USA). The scanner contains RapidBuilder Multimedia Simulation Format (XStream Software) (RBX), which enables the operator to visualise melanin and erythema in the skin. This means that the operator can see abnormal concentrations of melanin, such as hyperpigmentation, or vascular irregularities, such as telangiectasia.

The primary aim of this study was to evaluate the scanner’s erythema function, by comparing the results of the face scanner with a laser Doppler device and a skin pigmentation analyser.


Material and methods

After institutional approval and with informed consent, 20 volunteers (mean (SD) age 24 (1.5) years, 13 women, 7 men) participated in this clinical study. The exclusion criterion was an acute or chronic disease of the facial skin. Three-dimensional scans of their faces were taken using the Vectra X3. On a selected portion of the skin, we measured the relative concentration of haemoglobin with the laser Doppler O2C (LEA Medizintechnik GmbH, Gießen, Germany). The concentrations of melanin and erythema was measured with the skin pigmentation analyser (Courage + Khazaka Electronic GmbH, Cologne, Germany). Both devices sent light of specific wavelengths into the skin and analysed the light that was reflected. Then, we used the nitric oxide cream to increase local blood flow to the selected area, as described by Opländer et al, and we repeated all three measurements immediately.

For the homogeneous and detailed analysis of the face scans, the colours red and brown were filtered, which corresponded to the distribution of haemoglobin and melanin. Then the scans were transformed into grey pictures. On the selected area, four corresponding points were identified, the grey tones were measured and mean values calculated ( Fig. 1 ).

Corresponding points for the analyses before and after the application of the nitric oxide cream.
Fig. 1
Corresponding points for the analyses before and after the application of the nitric oxide cream.

Statistical analyses

The data obtained were structured using MS Office Excel 2003 ® (Microsoft Corporation, Redmond, WA, USA). Statistical analyses were done with the help of SAS ® (SAS Institute, Cary, NC, USA). The Pearson correlation coefficient was used to investigate any significant changes in measurement for each person. A paired t -test was used to compare the three methods of measuring the circulation of the skin. All data were expressed as mean (SD), and values of p = ≤0.05 were considered to be significant.


Results

After the cream was applied to the skin, macroscopic changes in colour were detected. After the facial scans were converted into a 2-dimensional picture and grey tones, the mean measured grey tone was 163.3 RGB before the application of the cream and 99.9 RGB afterwards, which corresponds to a darker grey tone. All devices showed a significant improvement in local blood flow after the cream was applied (p < 0.001) ( Table 1 ).

Table 1
Results before and after application of nitric oxide cream. Data are mean (SD).
Device Characteristic Before After p value
Vectra X3 Grey 163 (23) 100 (29) <0.001
SPA 99 Erythema 51 (10) 58 (9) <0.001
O2C Local haemoglobin 64 (8) 77 (6) <0.001
O2C Velocity 15 (6) 11 (4) <0.001
O2C Flow 53 (36) 168 (61) <0.001

The Pearson correlation coefficient showed a strongly positive linear relationship of the grey tone and the local concentration of haemoglobin, (r = 0.772) the erythema and the local concentration of haemoglobin, (r = 0.764) and erythema and the grey tone (r = 0.796). All results were significant (p < 0.0001).

According to these results, the haemoglobin concentration values were assigned to corresponding grey tones in a chart ( Fig. 2 ).

Colour scale of the grey tones with the corresponding concentrations of haemoglobin.
Fig. 2
Colour scale of the grey tones with the corresponding concentrations of haemoglobin.

Discussion

The Vectra X3 camera has been used in many studies and it has been proved that the scans are particularly useful for documentation, anthropometric, and volume measurements. Using the RBX technology our measurement showed that the 3-dimensional camera shows changes of blood flow in the superficial skin layer with great sensitivity.

For daily use, a colour scale with a corresponding chart was developed. By using the colour scale, it is possible to assess the local haemoglobin concentration by the RGB value of a picture. Although the developed procedure provides a reliable output, the system can be further optimised as not all grey tones were covered in this study. The scale could be particularly useful to evaluate areas of skin with scars from previous operations or burns, and to evaluate critical areas of perfusion when further operations with flap rotations have to be planned.


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