Burn wound healing time assessed by laser Doppler imaging (LDI). Part 1: Derivation of a dedicated colour code for image interpretation

IntroductionLaser Doppler imaging produces a colour-coded image of dermal blood flow, which can be used to quantify the inflammatory response in a burn. The original colour palette had arbitrary boundaries, which inexperienced clinicians found difficult to interpret. The aim of this study was to define clinically useful boundaries that would assist in the prediction of burn healing potential.MethodWe conducted a prospective, multi-centre study of burns in adults and children. LDI scans were performed between 48 h and 5 days after injury. The burns were assessed clinically and photographed on day of scan, day 14 and day 21 post-injury. Areas healed at day 14, healed between day 14 and 21 and unhealed at day 21 were identified on the LDI scan. The flow values for the pixels in these regions were analysed to calculate boundaries between the three healing categories.ResultsWe recruited 137 patients (ages 1–88 years, 65% male); 392 LDI scans contained 433 different burn sites; 109 regions of interest were studied. Analysis allowed us to define ranges for the three healing categories: HP14 colour coded red, >600PU; HP14–21, yellow, 260–440PU; HP>21, blue, <200PU; separated by two overlap regions pink, 440–600PU and green, 200–260PU. Blue was subdivided to show the very high association between LDI < 140PU and non-healing at day 21.ConclusionWe have devised a new colour palette for LDI burn imaging based on healing times of a series of burns. Validation of this palette is described separately, in Part 2.