Recent advances in photoacoustic endoscopy

Figure 1 Illustration of the photoacoustic effect and photoacoustic imaging. Reproduced with permission from Yao et al[6]. PA: Photoacoustic.

Figure 2 Three major implementations of photoacoustic tomography, with representative in vivo images. A: Optical-resolution photoacoustic microscopy and an image of hemoglobin oxygen saturation (SO₂) in a mouse ear; B: Circular-array photoacoustic computed tomography and an image of cerebral hemodynamic changes, ∆[hemoglobin], in response to one-sided whisker stimulation in a rat; C: Photoacoustic endoscopy and an image of a rabbit esophagus and adjacent internal organs, including the trachea and lung. Reproduced with permission from Wang et al[5]. SO₂: Oxygen saturation; UST: Ultrasonic transducer.

Figure 3 Simultaneous, co-registered, photoacoustic endoscopy and endoscopic ultrasound images of rabbit esophagus. A: Three-dimensionally rendered photoacoustic structural image. The left- and right-hand sides of this image correspond to the lower and upper esohagus, respectively, and the lower portion (-y axis) to the ventral side of the rabbit; B: Co-registered ultrasonic structural image for the same volume of A; C: An overlaid images of A and B. In A-C, horizontal and vertical scale bars represent 2 cm and 5 mm, respectively; D: A representative photoacoustic x-y cross-sectional image (18 mm in diameter) near the lung, as indicated by the left arow in A; E: Corresponding ultrasonic cross-sectional image of D; F: A combine image of D and E; G: A photoacoustic x-y cross-sectional image near the trachea, as indicated by the right arow in A; H: Corresponding ultrasonic cross-sectional image of G. In G and H, the dotted arrows indicate the contact point between the trachea and the esophagus; I: Histology of the esophagus (top) and the trachea (bottom) (HE stain). Scale bar, 1 mm. Reproduced with permission from Yang et al[8].