title: Wound Area Measurement with Digital Planimetry: Improved Accuracy and Precision with Calibration Based on 2 Rulers.
abstract: BACKGROUND
  In the treatment of chronic wounds the wound surface area change over time is useful parameter in assessment of the applied therapy plan. The more precise the method of wound area measurement the earlier may be identified and changed inappropriate treatment plan. Digital planimetry may be used in wound area measurement and therapy assessment when it is properly used, but the common problem is the camera lens orientation during the taking of a picture. The camera lens axis should be perpendicular to the wound plane, and if it is not, the measured area differ from the true area.
  
  
  RESULTS
  Current study shows that the use of 2 rulers placed in parallel below and above the wound for the calibration increases on average 3.8 times the precision of area measurement in comparison to the measurement with one ruler used for calibration. The proposed procedure of calibration increases also 4 times accuracy of area measurement. It was also showed that wound area range and camera type do not influence the precision of area measurement with digital planimetry based on two ruler calibration, however the measurements based on smartphone camera were significantly less accurate than these based on D-SLR or compact cameras. Area measurement on flat surface was more precise with the digital planimetry with 2 rulers than performed with the Visitrak device, the Silhouette Mobile device or the AreaMe software-based method.
  
  
  CONCLUSIONS
  The calibration in digital planimetry with using 2 rulers remarkably increases precision and accuracy of measurement and therefore should be recommended instead of calibration based on single ruler.
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Foltynski
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Ladyzynski
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Ciechanowska
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Migalska-Musial
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Judzewicz
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Stanislawa
authors.initials: S
authors.lastname: Sabalinska
mesh_terms: D002138:Calibration; D006801:Humans; D010781:Photography / Q000379:methods*; D000068997:Smartphone; D012984:Software; D014947:Wounds and Injuries / Q000473:pathology*