Photoacoustic imaging: principle and endoscopic applications

Abstract

To improve diagnostic accuracy of gastrointestinal diseases, such as gastric and colorectal cancers, it is essential to develop advanced tomographic endoscopic techniques. The major limitation of conventional video endoscopy technique is that it is incapable of providing such useful diagnostic information as the depth of invasion or vascular connections for advanced high-stage cancers because it entirely relies on the surface-mapping CCD camera images. Presently, endoscopic ultrasound (EUS) and confocal endoscopy techniques are available options for delineating tumor margin and visualizing neighboring structures. However, these techniques are still insufficient for evaluating the mentioned diagnostic information due to poor image contrast for soft tissues or shallow penetration depths. In such aspect, the photoacoustic endoscopy (PAE) technique that we are currently developing could become a new clinical endoscopic tool that overcomes the limitations of the aforementioned endoscopic techniques. Since PAE inherits all the key imaging features of photoacoustic tomography (PAT), which provides a variety of endogenous and exogenous image contrasts at several-centimeter levels, we expect that PAE has strong potential for solving the mentioned clinical issues.