DEVELOPMENT OF CLINICAL PHOTOACOUSTIC ENDOSCOPIC PROBE FOR THE GASTROINTESTINAL TRACT: DESIGN AND IMPLEMENTATION

Aims:

To improve diagnostic accuracy of gastrointestinal diseases, such as gastric and colorectal cancers, it is essential to develop advanced tomographic endoscopic techniques. The major limit of conventional video endoscopy is that it cannot provide such useful diagnostic information as the depth of invasion or vascular connections for advanced high-stage cancers because it solely relies on the visual inspection based on the surface-mapped camera images. At present, endoscopic ultrasound is the only available option for delineating tumor margin and visualizing surrounding structures. However, this technique is still insufficient for evaluating the mentioned diagnostic information due to the poor image contrast for soft tissues.

In our current project, we have been developing a 3.0-mm diameter catheterized photoacoustic endoscopic probe with a clinically-applicable structure and imaging performance to apply to gastrointestinal tract disease diagnosis. Our key focus in designing the endoscope is to enable the probe to perform endoscopic imaging via the 3.7-mm diameter standard instrument channel of a video endoscope.

Methods:

To enable cellular level visualization of suspicious tissues, we are constructing the mini-probe by adopting the optical-resolution photoacoustic imaging concept in which both the optical and acoustic beam are tightly focused in a confocal configuration. All the scanning tip and torque transmitting coil are completely sheathed by a 2.5-m long plastic catheter.

Results:

We have successfully worked out an optimal system configuration that enables very uniform circumferential and radial scanning while conserving a high flexibility. Also, the optical and acoustic imaging performance were satisfactorily validated through a range of computer simulations and mechanical tests. Thus, it is possible to apply this technique to animal models.

Conclusions:

We introduced our endoscopic system and discussed clinical benefits of the proposed endoscopic design. We expect that it could provide invaluable diagnostic information based on the high-resolution and high-contrast image information.