Hair thickeness measurement

Hello all, I am a hair researcher and a newbie to Slicer3D.
I came to know Slicer3D from the article entitled “Clinical efficacy and safety of low‐dose oral minoxidil versus topical solution in the improvement of androgenetic alopecia: A randomized controlled trial - Asilian - 2024 - Journal of Cosmetic Dermatology - Wiley Online Library”
https://onlinelibrary.wiley.com/doi/10.1111/jocd.16086
The authors mentioned they used Slicer3D to measure hair strand thickness from trichoscopic images (like my sample photos attached).
I couldn’t find any instructions or tutorials regarding this use case, so I would be grateful if fellow members might guide me to how to measure hair thickeness.
Thank you