Precision of laser Doppler scanning in clinical use

Reactions of the cutaneous microcirculation to local stimuli have been quantitated in terms of area of erythema (planimetry), change in colour (colorimetry) and time-dependent changes in perfusion (one-dimensional laser Doppler fluxmetry (LDF)). Using the new technique of laser Doppler scanning (LDS) it is now possible to quantify and demonstrate two-dimensional patterns of microvascular perfusion in terms of intensity and extent. The precision of this new technique was compared with the previously established techniques by examining the reactions of 15 healthy volunteers to the intracutaneous injection of carbacholin and isotonic NaCl solutions. Both stimuli were applied paravertebrally, on the left and right side. Reactions were examined after 10 min. As a control for temporal reproducibility the examination was repeated on another day. All methods allowed the differentiation of reactions to carbacholin from those to NaCl (P < or = 0.0001). Only colorimetry and LDS provided data that were unequivocally reproducible when comparing both sides (r > or = 0.78). Using LDF or planimetry, reproducibility of values was lower (r < or = 0.58). When looking at measurements performed on different days, only values of LDS were reproducible (r > or = 0.77). Hyperaemic areas seen with LDS were significantly larger than those determined by planimetry. Results of LDS are reproducible spatially and temporally: the technique will allow time-course observations of skin reactions that are accompanied by medium-term changes in perfusion.