Propogation of the vasodilator response assessed by full-field laser doppler perfusion imaging (FLPI): a new fast tissue blood flow imaging technique

We have previously used high resolution scanning laser Doppler imaging [LDI] to quantify spatial and temporal changes in vascular perfusion following dermal provocation with vasoactive mediators [Clough et al., B J Dermatol 1998;138:806-814]. We used the LDI in repeat mode with scans of 30 sec duration and ?4000 pixel density, giving a spatial resolution of ?0.6 mm² per pixel over an area of 5 x 5 cm². Peak responses were seen within 2-3 min of agonist administration. These studies also reveal heterogeneity of perfusion response that was suggestive of selective recruitment of vessels in relation to the underlying dermal vasculature architecture. We have now explored this further using FLPI: this imaging technique was used at frame rates between 5 Hz and 0.2 Hz and spatial resolutions between 0.017 and 0.52 mm² per pixel over areas of 2 x 2.7 cm² and 6.7 x 9 cm², respectively. Preliminary results suggest that the rate of the linear phase of the increase in blood flux adjacent to the site of provocation is of the order of 1.8 PU [laser Doppler perfusion units]/sec. At more distant sites [17 mm] blood flux appears to rise more slowly [0.6 PU/sec at] with a latency of between 20 – 40 sec. Peak responses were seen within 3 minutes of provocation. The propagation of the dilatation response away from the site of provocation was of the order of 0.5 mm/sec. The FLPI imager is now being used to explore further the development of the vasodilator response in healthy skin in order to study both normal physiological mechanisms and the mechanisms underlying pathological skin disorders in which the microvasculature plays a predominant role.