A preliminary assessment of laser Doppler perfusion imaging in human skin using the tuberculin reaction as a model

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Abstract
Laser Doppler imaging is a new development in the field of laser Doppler flowmetry. The authors were recently loaned the Lisca laser Doppler perfusion imager (LDI) manufactured by Lisca Development, Linkoping, Sweden for assessment against other methods for assessment of skin perfusion. In order to evaluate the device, it was applied to imaging flux changes induced in human skin during the tuberculin reaction. Flux values were compared directly with those from conventional lightguide laser Doppler flowmetry, and parameters measured using two other methods for assessment of tissue perfusion, dynamic thermographic imaging and tissue spectrophotometry. The results showed very good correlations between the various methods. In addition, the LDI showed that very large differences in flux values (up to 5 V) could be found within distances of only 2 mm during the tuberculin reaction and that focal centres of low flux values surrounded by higher values ('craters') could be found not only at the centre, but elsewhere in the lesion. The LDI enables rapid non-invasive detailed analysis of blood flow patterns in skin and correlates well with other methods for measuring skin perfusion. Its use to examine heterogeneity of microvascular blood flow patterns may lead to further understanding of the local mechanisms for regulation of oxygen supply to tissue.