Simultaneous functional photoacoustic and ultrasonic endoscopy of internal organs in vivo

Abstract

Presently, clinicians routinely apply ultrasound endoscopy in a variety of interventional procedures which provide treatment solutions for diseased organs. Ultrasound endoscopy not only produces high resolution images, it is also safe for clinical use and broadly applicable. However, for soft tissue imaging, its mechanical wave-based image contrast fundamentally limits its ability to provide physiologically-specific functional information. By contrast, photoacoustic endoscopy possesses a unique combination of functional optical contrast and high spatial resolution at clinically-relevant depths, ideal for soft tissue imaging. With these attributes, photoacoustic endoscopy can overcome the current limitations of ultrasound endoscopy. Moreover, the benefits of photoacoustic imaging do not come at the expense of existing ultrasound functions; photoacoustic endoscopy systems are inherently compatible with ultrasound imaging, enabling multi-modality imaging with complementary contrast. Here, we present simultaneous photoacoustic and ultrasonic dual-mode endoscopy and demonstrate its ability to image internal organs in vivo, illustrating its potential clinical application.

The potential role of optical biopsy in the study and diagnosis of environmental enteric dysfunction

“…One approach would involve imaging the leakage of an intravenously delivered photoacoustic contrast agent from the blood stream into the gut using endoscopic probes. Several endoscopic PAI probes have been reported 97 and a number have been applied to gastrointestinal studies, both in live animals 98 and in ex vivo samples of human tissue 99 , suggesting that this technique would be entirely feasible. Alternatively, non invasive PAI could be achieved by using an orally ingested contrast agent along with an external imaging probe (likely to consist of a pulsed excitation laser combined with a commer cially available ultrasound transducer similar to the devices reported in REF.…”

Label-free optical-resolution photoacoustic endomicroscopy in vivo

“…We designed the OR-PAEM probe [ Fig. 1(a)] based on the scanning mirror and built-in micromotor-based mechanical scanning mechanism reported in our previous papers [36][37][38][39]. The built-in scanning mechanism provides much better scanning stability than a flexible shaftbased proximal actuation mechanism [43].…”

“…1(b)], the configuration of the confocal optical illumination and acoustic detection [ Fig. 1(c)], and the acoustic matching and sheathing methods were also similar to previous acoustic-resolution (AR) PAE probes [36][37][38][39]. However, to realize OR-PAEM imaging, we implemented the optical illumination unit with optical focusing capability.…”

“…The basic components are the same as in the previous AR-PAE system [39], namely a micromotor driver circuit (Namiki), a delay generator (home-made), a Q-switched diode-pumped Nd:YAG laser (SPOT 10-200-532, Elforlight), a US amplifier (5073PR, Panametrics), a data acquisition (DAQ) card (200 MHz, NI PCI-5124, National Instruments), and a computer for recording signals and displaying images. However, to perform OR-PAEM imaging with a sufficient A-line sampling density for each B-scan, we implemented a frequency multiplier circuit that multiplies the original step frequency of the geared micromotor (SBL015-06XXPG254, Namiki Precision) by eight times.…”

“…with focused US ring transducer-based optical illumination and an acoustic detection unit, and installed them in a small diameter imaging probe with a mechanical scanning mechanism. We solved the probe encapsulation and acoustic matching requirements by adopting a related strategy utilized in our earlier works [36][37][38][39]. To demonstrate the new imaging probe's in vivo imaging ability, we imaged the descending colons of two rats and acquired the first in vivo OR-PAEM image.…”