Is photoshop with Qualitative Image Analysis a valid technique for measuring hair morphology? A test using wires of known dimensions

Abstract. Three image analysis methods were compared to assess the most effective way to accurately measure the length and width of a series of wires, which represent mammalian hair. Five different wires of known length and width were mounted with straight wires (Layout A) or curvy wires (Layout B) each with different angles or curvature. Prepared cards were scanned on a flatbed scanner at maximum resolution (1200 dpi), and analysed using Qualitative Image Analysis 64 software (QIA-64). Method 1 utilized the default automatic thresholding algorithm to measure all generated features. Method 2 used manual selection of features. Method 3 also used manual feature selection, but used the Johannsen thresholding algorithm instead of automatic thresholding. QIA-64 could accurately measure the length of straight wires when features were selected manually (Methods 2 and 3), but could not accurately determine the length of curved wires. With respect to width measurements, the Inscribed Radius procedure measured width more accurately than Mean Fibre Width. QIA-64 has the potential for use in research but requires further refinement and validation before it can replace manual measurement of length and width using a microscope.