High-resolution handheld rigid endomicroscope based on full-field optical coherence tomography

Abstract

Full-field optical coherence tomography (FF-OCT) is a powerful tool for nondestructive assessment of biological tissue, i.e., for the structural examination of tissue in depth at a cellular resolution. Mostly known as a microscopy device for ex vivo analysis, FF-OCT has also been adapted to endoscopy setups since it shows good potential for in situ cancer diagnosis and biopsy guidance. Nevertheless, all the attempts to perform endoscopic FF-OCT imaging did not go beyond lab setups. We describe here, to the best of our knowledge, the first handheld FF-OCT endoscope based on a tandem interferometry assembly using incoherent illumination. A common-path passive imaging interferometer at the tip of an optical probe makes it robust and insensitive to environmental perturbations, and a low finesse Fabry-Perot processing interferometer guarantees a compact system. A good resolution (2.7 μm transverse and 6 μm axial) is maintained through the long distance, small diameter relay optics of the probe, and a good signal-to-noise ratio is achieved in a limited 100 ms acquisition time. High-resolution images and a movie of a rat brain slice have been recorded by moving the contact endoscope over the surface of the sample, allowing for tissue microscopic exploration at 20 m under the surface. These promising ex vivo results open new perspectives for in vivo imaging of biological tissue, in particular, in the field of cancer and surgical margin assessment.

Full‐field swept‐source optical coherence tomography and neural tissue classification for deep brain imaging

“…This work introduced the first full-field SS-OCT system with an endoscopic probe, operating in the wavelength range centered at 1310 nm. The achieved transverse and axial resolution is comparable with some of the previously demonstrated systems [32,42,59], and it presents additional advantages over other higher-resolution systems [28,45,46], in particular due to the relatively thin endoscopic tip and the long imaging depth. The system has the advantage of using components developed for telecommunications.…”

“…The achieved transverse and axial resolution is comparable with some of the previously demonstrated systems [32,42,59], and it presents additional advantages over other higher-resolution systems [28,45,46], in particular due to the relatively thin endoscopic tip and the long imaging depth. The achieved transverse and axial resolution is comparable with some of the previously demonstrated systems [32,42,59], and it presents additional advantages over other higher-resolution systems [28,45,46], in particular due to the relatively thin endoscopic tip and the long imaging depth.…”

“…Finally, for clinical settings, the optical system must be miniaturized and packaged with a longer endoscope similar to the prototype developed by Benoit a la Guillaume et al [46], but with longer imaging depth. Despite the limitations of our system and measurements, to our knowledge, our findings currently have no direct counterpart in the literature, and can be refined further for greater fidelity.…”

“…An endoscopic FF-OCT system demonstrated by Benoit a la Guillaume et al provided sufficient resolution to resolve neurons, but its imaging depth was limited to tens of microns [46], whereas the structures of interest for neurosurgeical procedures are at least 1 mm thick. Another study, by Liang et al, employed an endoscopic probe in a SS-OCT system around 1310 nm and was able to distinguish between white matter, gray matter and blood vessels in a sheep brain, which has a brain volume that is about 100 times larger than a rat, but the authors could not distinguish not between among different types of gray matter [32].…”

Validation of full-field optical coherence tomography in distinguishing malignant and benign tissue in resected pancreatic cancer specimens

“…Progression is made on both accounts. The first handheld endomicroscope based on FF-OCT was recently described by Benoit a la Guillaume et al [43], which opens new perspectives for in vivo imaging. Furthermore, a 7 times faster and 3 times more sensitive camera was introduced in the device, also bringing it closer to clinical implementation [44].…”