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Emerging non-invasive tools for hair follicle assessment: a narrative review on hyperspectral and terahertz imaging

Debalina Bose, Rinky Kapoor, Debashree Das, Debraj Shome, Esmael Ahmed

Lasers in Medical Science, 2026

Abstract

Hair loss, though often dismissed as cosmetic, reflects complex vascular, metabolic, structural, and inflammatory changes within the scalp microenvironment. Conventional diagnostic tools such as visual inspection, dermoscopy, trichoscopy, and biopsy remain limited in their ability to determine these evolving processes non-invasively. Recent advances in optical physics and biomedical engineering have introduced light- and wave-based imaging approaches that may expand scalp diagnostics beyond surface visualization. Hyperspectral imaging (HSI) and terahertz (THz) imaging have demonstrated comparable capabilities for assessing tissue biochemistry, microstructure, hydration dynamics, pigmentation, and vascular signatures in related dermatologic applications and may support exploratory investigation of scalp assessment after validation. However, direct clinical evidence supporting HSI and THz imaging specifically in hair-loss patients remains limited. Therefore, this review integrates available alopecia-related imaging evidence, mechanistic and modeling evidence relevant to hair biology, and extrapolated findings from broader dermatologic applications, including oncology and wound-healing research. Relevant literature was identified by structured searches of PubMed, Scopus, and Google Scholar, covering studies published from June 2008 to March 2026. The review analyzes how these technologies may identify indirect, non-invasive scalp-tissue indicators associated with follicular…

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