FF-OCT: Rapid Polyp Analysis During Colonoscopy

A “characterize, resect, and discard” strategy has been proposed as a new approach, allowing more expeditious and efficient management of the patient with colonic polyps as well as histologic procedure cost savings. However, despite recent advances, the technologies embedded in currently available endoscopes have not proven to be sufficiently reliable to implement that strategy in the routine endoscopic practice.¹ Full-field optical coherence tomography (FFOCT) is an emerging optical technique for the rapid evaluation of tissue architecture.² FFOCT has been used to image fresh and fixed human tissues such as skin,³ cornea,⁴ brain,⁵ and even pancreatic biopsy specimens.⁶ FFOCT might prove useful during colonoscopy, when a rapid on-site assessment of tissue architecture can determine whether to discard polyps and immediately advise patients on subsequent surveillance or to warrant further histologic analysis. Here, we present the technical feasibility of ex vivo FFOCT imaging on colonic polyps and its ability to visualize cellular and architectural features of normal and neoplastic colonic tissue.

Description of Technology

The commercially available FFOCT apparatus (Light-CT Scanner, LLTech SAS, Paris, France; Figure 1), which is supplied with a reusable sample holder with no limit to the number of uses, produces images of ex vivo tissue with a transverse resolution of 1.5 μm and an axial resolution of 1.0 μm. This compact (310 × 310 × 800 mm, L × W × H, about the size of a standard optical microscope) FFOCT setup can be located in the endoscopy room. The system is unobtrusive and does not create any undesired heating, lighting, or sound. OCT⁷ is a technique for imaging scattering media such as biological tissues by interferometric selection of ballistic photons. Unlike conventional OCT, FFOCT directly captures en face or cross-sectional images on megapixel cameras at high lateral resolution (down to 1 μm) by using medium to large aperture microscopy optics with high axial resolution (1 μm) and a white light source.²

Capturing images in the desired orientation allows for easy comparison with histologic sections. A pathologist typically analyses tissue at several magnifications where the field of view varies from centimeters down to micrometers. The same effect is achieved with the present system by moving samples on a micrometric bench to create a mosaic of native field images that are stitched together to display a larger field of view. A previous study of the pathologist’s training process dedicated to FFOCT imaging of prostatic tissue samples has shown a short learning curve and a good inter-reader agreement.⁸