Optoacoustic Endoscopy of the Gastrointestinal Tract

Abstract

Optical endoscopy is the most commonly applied procedure for inspecting the gastrointestinal (GI) tract, and it is based on different approaches and designs, from using a flexible optical scope to swallowing a small camera capsule that obtains photographs as it advances through the digestive tract. Despite its wide use in GI diagnostics and theranostics, optical visualization only allows a superficial inspection of the wall lining (mucosa), therefore limiting the ability to obtain information from deeper GI layers. In the quest for developing methods to visualize under the mucosal layers, we review herein progress with optoacoustic endoscopy, a technique that captures optical contrast in high resolution deep inside tissues, enabling imaging beneath the surface of the mucosa. Optoacoustic endoscopy combines imaging of optical contrast with the resolution and depth penetration afforded by ultrasonography, thus merging highly advantageous characteristics for clinical applications. We review progress and the current status of the technology, its key endoscopic competitors, and challenges for clinical application. We further offer a perspective regarding future directions and the overall application potential of the technique to complement the current state-of-the-art.

Unsupervised segmentation of 3D microvascular photoacoustic images using deep generative learning

“…All real and simulated photoacoustic images were normalised by performing XY slice-wise Z-score normalisation followed by thresholding of the top and bottom 0.05% of pixel intensities to correct for uneven illumination with respect to depth. Finally, datasets were normalised to a pixel intensity range of [−1, 1]. Datasets were partitioned with 10% assigned for testing and with the remaining 90% split 80/20 between training/validation.…”

“…Mesoscopic photoacoustic imaging (PAI) provides high-resolution, contrast-rich images of vascular structures in vivo based on the absorption of light by haemoglobin. These images reveal subtle changes in vascular architecture in tissues, which have demonstrated importance in diagnosis and staging of a range of diseases, from diabetes to oncology 1,2 . To quantify disease status, segmenting microvascular networks from 3D image volumes is vital, however, the development of segmentation frameworks has not kept pace with the rapid advancements in imaging technology.…”

A review of a strategic roadmapping exercise to advance clinical translation of photoacoustic imaging: From current barriers to future adoption

“…More importantly, PAI is on the pathway for clinical translation into mainstream medicine [16] , [17] , with a variety of applications demonstrated in patients using the tomographic PAI geometry, with a substantial number of studies applying PAI for cancer visualisation, especially in breast cancer [18] , [19] , [20] , [21] . Recently, a wide range of potential further clinical applications have emerged, such as evaluation of skin microvasculature [22] , [23] , functional and endoscopic assessment of the gastrointestinal tract [24] , [25] , surgical guidance [26] , monitoring inflammation [27] , [28] , [29] and monitoring lymphadenopathies [30] / lymphedema [31] . These diverse applications demonstrate the future clinical potential for PAI underpinned by the versatile nature of the hardware implementations available.…”