title: Tissue viability imaging: mapping skin erythema.
abstract: BACKGROUND
  Tissue Viability Imaging (TiVi) is an emerging bioengineering technology intended for two-dimensional mapping of skin erythema and blanching. Before TiVi can be effectively used in studies of diseased or damaged skin, the variability in normal skin red blood cell concentration (RBC(conc)) requires evaluation.
  
  
  OBJECTIVE
  To demonstrate how TiVi maps spatial and temporal variations in normal skin RBC(conc) at the dorsal side of the hand at rest and during post-occlusive hyperemia.
  
  
  METHODS
  Short-term and day-to-day variations in skin RBC(conc) were quantified at the dorsal side of the hand in four healthy volunteers at rest. In a separate study, the increase in skin RBC(conc) was recorded during post-occlusive hyperemia.
  
  
  RESULTS
  A lower skin RBC(conc) (179-184 TiVi units) was observed at the back of the hand and base of the thumb compared with areas adjacent to the nailfoldfold region of the fingers (190-213 TiVi units). The short-term variation (within 70 s) was <2% in all areas of the dorsal side of the hand, while day-to-day variations were in the range 5-7% in the back of the hand and up to 10% in areas adjacent to the nailfold region. In the post-occlusive hyperemia phase, up to a 60% increase in skin RBC(conc) was observed in the early part of the reactive hyperemia phase. This increase in skin RBC(conc) successively decreased but remained about 18% above the pre-occlusion level after 30 min.
  
  
  CONCLUSIONS
  Establishment of healthy skin RBC(conc) reference values is important for the design of versatile test procedures for assessment of skin damage caused by vibration tools, chemical exposure or peripheral vascular disease.
authors.affiliation: Department of Dermatology, School of Medicine, University of California, San Francisco, CA, USA.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhai
authors.forename: Heidi P
authors.initials: HP
authors.lastname: Chan
authors.forename: Sara
authors.initials: S
authors.lastname: Farahmand
authors.forename: Gert E
authors.initials: GE
authors.lastname: Nilsson
authors.forename: Howard I
authors.initials: HI
authors.lastname: Maibach
mesh_terms: D046169:Dermoscopy / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004890:Erythema / Q000473:pathology* / Q000503:physiopathology*; D004906:Erythrocyte Count / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000295:instrumentation*; D013548:Sweden; D014022:Tissue Survival