{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T16:19:55Z","timestamp":1780071595504,"version":"3.54.0"},"reference-count":54,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2020,10,16]],"date-time":"2020-10-16T00:00:00Z","timestamp":1602806400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["R21 AG065776"],"award-info":[{"award-number":["R21 AG065776"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["R21 DE029025"],"award-info":[{"award-number":["R21 DE029025"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["DP2 HL137187"],"award-info":[{"award-number":["DP2 HL137187"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["1842387"],"award-info":[{"award-number":["1842387"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["1937674"],"award-info":[{"award-number":["1937674"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Follicular unit extraction (FUE) and follicular unit transplantation (FUT) account for 99% of hair transplant procedures. In both cases, it is important for clinicians to characterize follicle density for treatment planning and evaluation. The existing gold-standard is photographic examination. However, this approach is insensitive to subdermal hair and cannot identify follicle orientation. Here, we introduce a fast and non-invasive imaging technique to measure follicle density and angles across regions of varying density. We first showed that hair is a significant source of photoacoustic signal. We then selected regions of low, medium, and high follicle density and showed that photoacoustic imaging can measure the density of follicles even when they are not visible by eye. We performed handheld imaging by sweeping the transducer across the imaging area to generate 3D images via maximum intensity projection. Background signal from the dermis was removed using a skin tracing method. Measurement of follicle density using photoacoustic imaging was highly correlated with photographic determination (R2 = 0.96). Finally, we measured subdermal follicular angles\u2014a key parameter influencing transection rates in FUE.<\/jats:p>","DOI":"10.3390\/s20205848","type":"journal-article","created":{"date-parts":[[2020,10,16]],"date-time":"2020-10-16T08:56:48Z","timestamp":1602838608000},"page":"5848","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Photoacoustic Imaging as a Tool for Assessing Hair Follicular Organization"],"prefix":"10.3390","volume":"20","author":[{"given":"Ali","family":"Hariri","sequence":"first","affiliation":[{"name":"Nanoengineering Department, University of California-San Diego, La Jolla, CA 92093, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1809-5955","authenticated-orcid":false,"given":"Colman","family":"Moore","sequence":"additional","affiliation":[{"name":"Nanoengineering Department, University of California-San Diego, La Jolla, CA 92093, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yash","family":"Mantri","sequence":"additional","affiliation":[{"name":"Bioengineering Department, University of California-San Diego, La Jolla, CA 92093, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesse V.","family":"Jokerst","sequence":"additional","affiliation":[{"name":"Nanoengineering Department, University of California-San Diego, La Jolla, CA 92093, USA"},{"name":"Material Science and Engineering Program, University of California-San Diego, La Jolla, CA 92093, USA"},{"name":"Radiology Department, University of California-San Diego, La Jolla, CA 92093, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,10,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1177\/1090820X12468314","article-title":"Hair Restoration Surgery: The State of the Art","volume":"33","author":"Vogel","year":"2013","journal-title":"Aesthetic Surg. 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