Wu, Pei JhePei JheWuTseng, Hsiao ChiehHsiao ChiehTsengCHI-CHAO CHAOYI-HUA LIAOCHEN-TUNG YENWEN-YING LINSUNG-TSANG HSIEHWEI-ZEN SUNCHI-KUANG SUN2024-04-182024-04-182024-03-2526672375https://scholars.lib.ntu.edu.tw/handle/123456789/641964Label-free imaging methodologies for nerve fibers rely on spatial signal continuity to identify fibers and fail to image free intraepidermal nerve endings (FINEs). Here, we present an imaging methodology—called discontinuity third harmonic generation (THG) microscopy (dTHGM)—that detects three-dimensional discontinuities in THG signals as the contrast. We describe the mechanism and design of dTHGM and apply it to reveal the bead-string characteristics of unmyelinated FINEs. We confirmed the label-free capability of dTHGM through a comparison study with the PGP9.5 immunohistochemical staining slides and a longitudinal spared nerve injury study. An intraepidermal nerve fiber (IENF) index based on a discontinuous-dot-connecting algorithm was developed to facilitate clinical applications of dTHGM. A preliminary clinical study confirmed that the IENF index was highly correlated with skin-biopsy-based IENF density (Pearson's correlation coefficient R = 0.98) and could achieve differential identification of small-fiber neuropathy (p = 0.0102) in patients with diabetic peripheral neuropathy.enCP: imaging | CP: neuroscience | diabetic peripheral neuropathy | free intraepidermal nerve endings | noninvasive imaging technique | optical biopsy | skin biopsy | skin innervation | small-fiber neuropathy | third harmonic generation | unmyelinated nerve fibers[SDGs]SDG3[SDGs]SDG7journal article10.1016/j.crmeth.2024.100735385032902-s2.0-85188543661https://api.elsevier.com/content/abstract/scopus_id/85188543661