Measurement of depth of burns by laser Doppler perfusion imaging

Laser Doppler perfusion imaging (LDPI), is a further development in laser Doppler flowmetry (LDF). Its advantage is that it enables assessment of microvascular blood flow in a predefined skin area rather than, as for LDF, in one place. In many ways this method seems to be more promising than LDF in the assessment of burn wounds. However, several methodological issues that are inherent in the LDPI technique, and are relevant for the assessment of burn depth, must be clarified. These include the effect of scanning distance, curvature of the tissue, thickness of topical wound dressings, and pathophysiological effects of skin colour, blisters, and wound fluids. Furthermore, we soon realised that to examine the perfusion image generated by LDPI adequately the process of analysis was appreciably improved by the simultaneous use of digital photography. In the present investigation we used both in vitro and in vivo models and also examined burned patients, and found that the listed factors all significantly affected the LDPI output signal. However, if these factors are known to the examiner, most of them can be adjusted for. If the technique is further improved by minimizing such effects and by reducing the practical difficulties of applying it to a burned patient in the burns unit, the technique may find uses in everyday clinical decision-making.