title: Correcting for possible tissue distortion between provocation and assessment in skin testing: the divergent beam UVB photo-test.
abstract: BACKGROUND
  In tissue viability imaging (TiVi), an assessment method for skin erythema, correct orientation of skin position from provocation to assessment optimizes data interpretation. Image processing algorithms could compensate for the effects of skin translation, torsion and rotation realigning assessment images to the position of the skin at provocation.
  
  
  METHODS
  A reference image of a divergent, UVB phototest was acquired, as well as test images at varying levels of translation, rotation and torsion. Using 12 skin markers, an algorithm was applied to restore the distorted test images to the reference image.
  
  
  RESULTS
  The algorithm corrected torsion and rotation up to approximately 35 degrees. The radius of the erythemal reaction and average value of the input image closely matched that of the reference image's 'true value'.
  
  
  CONCLUSIONS
  The image 'de-warping' procedure improves the robustness of the response image evaluation in a clinical research setting and opens the possibility of the correction of possibly flawed images performed away from the laboratory setting by the subject/patient themselves. This opportunity may increase the use of photo-testing and, by extension, other late response skin testing where the necessity of a return assessment visit is a disincentive to performance of the test.
authors.affiliation: Division of Imaging Sciences & Biomedical Engineering, King's College London, St Thomas' Hospital, London, SE1 7EH, United Kingdom.
authors.forename: Jim
authors.initials: J
authors.lastname: O'Doherty
authors.forename: Joakim
authors.initials: J
authors.lastname: Henricson
authors.forename: Magnus
authors.initials: M
authors.lastname: Falk
authors.forename: Chris D
authors.initials: CD
authors.lastname: Anderson
mesh_terms: D000328:Adult; D000465:Algorithms; D004890:Erythema / Q000473:pathology*; D005260:Female; D005542:Forearm; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D056951:Photoelectron Spectroscopy / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D012867:Skin / Q000473:pathology; D014022:Tissue Survival
keywords: TiVi; image correction; photo-test; spectroscopy; tissue viability imaging