Article

Laser Doppler imaging of burn scars: A comparison of wavelength and scanning methods

Department of Surgery, The University of Calgary, Calgary, Alberta, Canada
Burns (Impact Factor: 1.84). 06/2003; 29(3):199-206. DOI: 10.1016/S0305-4179(02)00307-8
Source: PubMed

ABSTRACT Laser Doppler perfusion imaging (LDI) is a useful tool for the early clinical assessment of burn depth and prognostic evaluation of injuries that may require skin grafting. We have evaluated two commercially available laser Doppler imagers for the perfusion measurement of normal and burn scar tissue.
A single wavelength (635 nm), step-wise scanning LDI and a dual wavelength (633 and 780 nm), continuous scanning LDI were used. Twenty patients with hypertrophic burn scars (time since injury: 1 month-8 years) were recruited and the color and elevation of the scar was clinically assessed using a modified Vancouver Burn Scar Scale. Perfusion of each scar region was measured using both imagers. A symmetric contralateral region of unburned skin was also imaged to record baseline perfusion.
Comparisons of wavelength and scanning technique were made using perfusion values obtained from 22 burn scars. Highly significant positive correlation was observed in all comparisons. In addition, output from both instruments was strongly and significantly correlated with the clinical grading of the scar.
Both LDI scanners perform similar perfusion measurements. The results also indicate that red and near-infrared (NIR) wavelength photons provide similar blood flow information. The faster, continuous scanning method provides a clinical advantage without a significant loss of blood flow information. However, a critical evaluation of both instruments suggests that caution must be exercised when using these optical diagnostic techniques and that some knowledge of light-tissue interaction is required for the proper analysis and interpretation of clinical data.

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    • "This enhancement of local blood flow, the stimulation of microcirculation, and possibly neovascularization, may be beneficial for the treatment of diseases that are caused by excessive fibrosis, as well as influence fibroblast growth in vitro. However, fresh hypertrophic scars display a pattern of 100–150% increase in perfusion, as has been shown in trunk and extremity scars using Laser Doppler measurements [13] [14] [15]. We believe the use of PTF in vivo in fresh HS might therefore cause an increase in inflammation and excessive formation of HS rather than a decrease. "
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    • "Thus, as tissue absorption increases, the LSPI perfusion index will decrease for a given flow rate and the slope of the LSPI output across a specified flow range has an inverse relation with the tissue absorption coefficient. Our previous work using LDI with burn patients demonstrated the problems of specular reflection artifact [19] "
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