Transvaginal fast-scanning optical-resolution photoacoustic endoscopy.

Photoacoustic endoscopy offers in vivo examination of the visceral tissue using endogenous contrast, but its typical B-scan rate is ∼10  Hz, restricted by the speed of the scanning unit and the laser pulse repetition rate. Here, we present a transvaginal fast-scanning optical-resolution photoacoustic endoscope with a 250-Hz B-scan rate over a 3-mm scanning range. Using this modality, we not only illustrated the morphological differences of vasculatures among the human ectocervix, uterine body, and sublingual mucosa but also showed the longitudinal and cross-sectional differences of cervical vasculatures in pregnant women.