title: Optical coherence tomography using images of hair structure and dyes penetrating into the hair.
abstract: OBJECTIVE
  Hair dyes are commonly evaluated by the appearance of the hair after dyeing. However, this approach cannot simultaneously assess how deep the dye has penetrated into hair.
  
  
  METHODS
  For simultaneous assessment of the appearance and the interior of hair, we developed a visible-range red, green, and blue (RGB) (three primary colors)-optical coherence tomography (OCT) using an RGB LED light source. We then evaluated a phantom model based on the assumption that the sample's absorbability in the vertical direction affects the tomographic imaging.
  
  
  RESULTS
  Consistent with theory, our device showed higher resolution than conventional OCT with far-red light. In the experiment on the phantom model, we confirmed that the tomographic imaging is affected by absorbability unique to the sample. Furthermore, we verified that permeability can be estimated from this tomographic image. We also identified for the first time the relationship between penetration of the dye into hair and characteristics of wavelength by tomographic imaging of dyed hair.
  
  
  CONCLUSIONS
  We successfully simultaneously assessed the appearance of dyed hair and inward penetration of the dye without preparing hair sections.
authors.affiliation: Skin Beauty Research Laboratories, Kao Corporation, Tokyo, Japan; Division of Bio-Applications and System Engineering (BASE), Graduate School of Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tsugita
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Iwai
mesh_terms: D000818:Animals; D003116:Color; D003124:Colorimetry / Q000295:instrumentation*; D046169:Dermoscopy / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006041:Goats; D006197:Hair / Q000737:chemistry* / Q000166:cytology*; D006202:Hair Dyes / Q000737:chemistry*; D008029:Lighting / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000295:instrumentation*
chemical_list: D006202:Hair Dyes
keywords: LED; OCT; RGB light sources; hair dyes; hair structure image