title: A computer-based method for precise detection and calculation of affected skin areas.
abstract: BACKGROUND
  The aim of this study was to describe and validate a method to obtain reproducible and comparable results concerning extension of a specific skin area, unaffected by individual differences in body surface area.
  
  
  METHODS
  A phantom simulating the human torso was equipped with three irregular areas representing the increasing extension of an affected skin area over time. A large sheet of flexible calques paper was placed at the phantom, and five clinicians copied the three irregular shapes two times, resulting in 60 copies. Subsequently, a digital photograph was taken of the calques papers with a clinical ruler placed at the margin. The images were postprocessed and measured in the program 'ImageJ' by two observers. An exact area measurement of the three irregular shapes was performed for comparison.
  
  
  RESULTS
  We found an interobserver variation of 0·36% when comparing the measurements of all three areas. Comparing observer measurements with the exact areas size, we found an underestimate of 2·52%. We observed a tendency that the discrepancy in measurement increases when the measured area decreases.
  
  
  CONCLUSIONS
  We find this method accurate, reproducible and easy to use. The presented method can be of help when documenting psoriasis and other dermatologic conditions as well as when exploring the effects of new types and variations of ultrasound-guided peripheral nerve blocks - especially in study volunteers.
authors.affiliation: Department of Neurology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark.
authors.forename: Sille Mølvig
authors.initials: SM
authors.lastname: Henriksen
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark.
authors.forename: Janus Damm
authors.initials: JD
authors.lastname: Nybing
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Frederiksberg, Copenhagen NV, Denmark.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Bouert
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark. seestein@gmail.com.
authors.forename: Inger
authors.initials: I
authors.lastname: Havsteen
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark.
authors.forename: Anders F
authors.initials: AF
authors.lastname: Christensen
authors.affiliation: Department of Anaesthesiology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Jensen
authors.affiliation: Department of Neurology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV, Denmark.
authors.forename: Hanne
authors.initials: H
authors.lastname: Christensen
authors.affiliation: Department of Anaesthesiology, Roskilde Hospital, University of Copenhagen, Roskilde, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Børglum
mesh_terms: D003880:Dermatology / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008348:Manikins; D015588:Observer Variation; D010781:Photography / Q000379:methods*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012867:Skin / Q000473:pathology*
keywords: clinical photo; interindividual application; phantom study; reliability; skin area estimation