In vivo photoacoustic tomography of porcine abdominal organs using Fabry-Pérot sensing integrated platform

Abstract

Objective: To evaluate in vivo a fully integrated photoacoustic tomography imaging system based on Fabry-Pérot ultrasound sensing method applied on porcine abdominal organs. This approach could be used by surgeons during intraoperative clinical procedures.

Methods: The photoacoustic imaging system was fully integrated into a single structure, and the detection technology was based on a Fabry-Pérot interferometer. The detection probe connected to the imaging system was applied directly to the organs of a male "large white" Sus scrofa pig weighing 80 kg, either manually or using a stand, with or without a gel interface. All experiments were performed in compliance with EU Directive 2010/63/EU on animal experimentation (APAFiS #31507).

Results: All intraperitoneal and retroperitoneal organs were evaluated using photoacoustic imaging. The evaluation of both hollow and solid organs was successfully conducted with consistent three-dimensional image quality. We demonstrate the system's ability to image blood vessels with diameters ranging from several millimeters down to less than 100 µm. Macroscopic evaluation of the organs using photoacoustic tomography imaging did not reveal any damage or burns caused by the excitation laser.

Conclusion: To our knowledge, this is the first reported imaging session of abdominal organs in an in vivo porcine model, performed using a photoacoustic tomography system with Fabry-Pérot interferometer detection. We present a high-resolution photoacoustic tomography system that is closer to routine clinical translation, thanks to a fully integrated system.

Relevance statement: Photoacoustic evaluation of organs using a fully integrated system could become a valuable tool for surgical teams for intraprocedural assessment of vascularization.

Key points: Photoacoustic imaging visualizes blood vessels without contrast agents or ionizing radiation. Photoacoustic imaging systems detect blood vessels ranging from millimeters to 100 µm. Fully integrated photoacoustic imaging systems are autonomously operable by surgical teams.

Keywords: Anatomy; Animal; Disease model; Equipment; Photoacoustic techniques.

Fig. 1

a Photoacoustic tomography prototype. The imaging probe can be seen wrapped in a plastic bag on a stand. b The probe when held by the surgeon performing the images. The organ imaged was the colon wall. c Close-up of the probe and the FPI sensor. d Schematic representation of the photoacoustic tomography system, detailing the components included in the system. CW Laser, Continuous wave laser; EDFA, Erbium-doped fiber amplifier; FPI, Fabry–Pérot interferometer; PC, Integrated computer; Pd, Photodiode chain; Pow. Sup., Power supply

Fig. 2

MIPs of the reconstructed volume of stomach tissue. a Reconstruction between 0.05 mm and 0.5 mm of depth. b Reconstruction between 0.5 mm and 1.5 mm of depth. c Reconstruction between 1.5 mm and 5 mm of depth. The superficial layer formed a web of small vessels mapping the tissue, while the deeper layers consisted of larger, branching vessels

Fig. 3

MIPs of stomach tissue (a) and colon tissue (b). Each figure presents the top-view MIPs, as well as the corresponding lateral MIPs. The arrow indicates vessel networks appearing as either triplets or pairs of parallel vessels traversing the organ (typically one artery and two veins)

Fig. 4

MIPs of gall bladder (a), small intestine (b), stomach (c), bladder (d), rectum (e), and ureter (f). Each figure presents the top-view MIPs. The arrow indicates the contents of the hollow organ. In the case of the rectum, it corresponds to stool, which exhibits optical absorption

Fig. 5

MIPs of liver tissue (a) and kidney tissue (b). Each figure presents the top-view MIP, as well as the corresponding lateral views. The arrow indicates the renal vessels in the form of linear structural features extending from the surface into deeper layers of the tissue. These vessels anatomically correspond to the interlobular arterioles (radiate part of the renal cortex)

Fig. 6

MIPs of pancreas tissue: top-view and corresponding lateral views