  There has been a longstanding expectation that the optical resolution
embodiment of photoacoustic tomography could have a substantial impact on
gastrointestinal endoscopy by enabling microscopic visualization of the
vasculature based on the endogenous contrast mechanism. Although multiple
studies have demonstrated the in vivo imaging capability of a developed imaging
device over the last decade, the implementation of such an endoscopic system
that can be applied immediately when necessary via the instrument channel of a
video endoscope has been a challenge. In this study, we developed a 3.38 mm
diameter catheter based, integrated optical resolution photoacoustic and
ultrasonic miniprobe system and successfully demonstrated its intrainstrument
channel workability for the standard 3.7 mm diameter instrument channel of a
clinical video endoscope based on a swine model. Through the instrument
channel, we acquired the first in vivo photoacoustic and ultrasonic dual mode
endoscopic images from the esophagogastric junction, which is one of the most
frequently cited anatomical sites in the gastrointestinal tract in relation to
Barretts esophagus. Moreover, from a rat colorectum in vivo imaging experiment,
we visualized hierarchically developed mesh like capillary networks with a hole
size as small as 50 microns, which suggests the potential level of image
details that could be photoacoustically provided in clinical settings in the
future.
