Quantifying whole human hair scalp fibres of varying curl: A micro‐computed tomographic study

Abstract

Scalp hair is a key feature of humans and its variability has been the subject of a broad range of studies. A small subset of these studies has focused on geometric quantification of human scalp hair fibres, however the use of race‐ and ethnicity‐based classification systems makes it challenging to draw objective conclusions about fibre variability. Furthermore, sample preparation techniques for micro‐imaging studies often alter the original form of hair fibres. This study sought to determine which of the commonly reported descriptors could be resolved using micro‐computed tomography (micro‐CT) for fibres of varying curl. Images obtained from micro‐CT were used to reconstruct three‐dimensional images that were then analysed. The study also explored the capabilities and limitations of micro‐CT as an imaging modality by comparing and cross‐validating findings with those obtained from scanning electron microscopy (SEM) and laser micrometry. The former deals with surface imaging while the latter deals with cross‐sectional measurements. Micro‐CT was found to be highly effective at resolving cross‐sectional ellipsoidal parameters, but performed more poorly than SEM in reconstructing surface level details at a 2 resolution. The technique was, however, able to reveal the presence of the medulla in type VI (high curl) hair fibres. When compared with high curl fibres, greater intra‐fibre variability was observed for the low and medium curl fibres, highlighting the importance more objective classification systems.