Dual-modality endomicroscopy with co-registered fluorescence and phase contrast

Functional Microendoscopy Reveals Calcium Responses of Single Cells in Tracheal Tuft Cells and Kidney Podocytes

Microendoscopy, a crucial technology for minimally invasive investigations of organs, facilitates studies within confined cavities. However, conventional microendoscopy is often limited by probe size and the constraint of using a single excitation wavelength. In response to these constraints, a multichannel microendoscope with a slender profile of only 360 µm is engineered. Functional signals both in situ and in vivo are successfully captured from individual single cells, employing a specially developed software suite for image processing, and exhibiting an effective resolution of 4.6 µm, allowing for the resolution of subcellular neuronal structures. This system enabled the first examination of calcium dynamics in vivo in murine tracheal tuft cells (formerly named brush cells) and in situ in kidney podocytes. Additionally, it recorded ratiometric redox reactions in various biological settings, including intact explanted organs and pancreatic islet cultures. The flexibility and streamlined operation of the microendoscopic technique open new avenues for conducting in vivo research, allowing for studies of tissue and organ function at cellular resolution.

Image computing for fibre-bundle endomicroscopy: A review

Endomicroscopy is an emerging imaging modality, that facilitates the acquisition of in vivo, in situ optical biopsies, assisting diagnostic and potentially therapeutic interventions. While there is a diverse and constantly expanding range of commercial and experimental optical biopsy platforms available, fibre-bundle endomicroscopy is currently the most widely used platform and is approved for clinical use in a range of clinical indications. Miniaturised, flexible fibre-bundles, guided through the working channel of endoscopes, needles and catheters, enable high-resolution imaging across a variety of organ systems. Yet, the nature of image acquisition though a fibre-bundle gives rise to several inherent characteristics and limitations necessitating novel and effective image pre- and post-processing algorithms, ranging from image formation, enhancement and mosaicing to pathology detection and quantification. This paper introduces the underlying technology and most prevalent clinical applications of fibre-bundle endomicroscopy, and provides a comprehensive, up-to-date, review of relevant image reconstruction, analysis and understanding/inference methodologies. Furthermore, current limitations as well as future challenges and opportunities in fibre-bundle endomicroscopy computing are identified and discussed.

Reconstruction of Optical Vector-Fields With Applications in Endoscopic Imaging

We introduce a framework for the reconstruction of the amplitude, phase, and polarization of an optical vector-field using measurements acquired by an imaging device characterized by an integral transform with an unknown spatially variant kernel. By incorporating effective regularization terms, this new approach is able to recover an optical vector-field with respect to an arbitrary representation system, which may be different from the one used for device calibration. In particular, it enables the recovery of an optical vector-field with respect to a Fourier basis, which is shown to yield indicative features of increased scattering associated with tissue abnormalities. We demonstrate the effectiveness of our approach using synthetic holographic images and biological tissue samples in an experimental setting, where the measurements of an optical vector-field are acquired by a multicore fiber endoscope, and observe that indeed the recovered Fourier coefficients are useful in distinguishing healthy tissues from tumors in early stages of oesophageal cancer.

Pupil plane differential detection microscopy

Differential interference contrast (DIC) microscopy is a powerful technique for imaging phase objects in transparent samples but does not work with scattering samples. This Letter, to the best of our knowledge, describes a new technique for obtaining DIC-like phase-gradient images in scattering media based on differential detection of forward-scattered light, using detectors arranged in a ring configuration around the microscope objective pupil or its conjugate pupil plane. This method, called pupil plane differential detection (P2D2) microscopy, does not need polarization optics or a confocal pinhole, yet produces images that are free of speckles and interference noises. We compared the P2D2 imaging technique with reflectance confocal microscopy and demonstrated P2D2 as a simple add-on to conventional laser scanning microscopes.

Fast hyperspectral phase and amplitude imaging in scattering tissue

Hyperspectral imaging in scattering tissue generally suffers from low light collection efficiency. In this Letter, we propose a microscope based on Fourier transform spectroscopy and oblique back-illumination microscopy that provides hyperspectral phase and amplitude images of thick, scattering samples with high throughput. Images can be acquired at >0.1  Hz rates with spectral resolution better than 200  cm-1, over a wide spectral range of 450-1700 nm. Proof-of-principle demonstrations are presented with chorioallantoic membrane of a chick embryo, illustrating the possibility of high-resolution hemodynamics imaging in thick tissue, based on transmission contrast.

Emerging optical methods for endoscopic surveillance of Barrett's oesophagus

Barrett's oesophagus is an acquired metaplastic condition that predisposes patients to the development of oesophageal adenocarcinoma, prompting the use of surveillance regimes to detect early malignancy for endoscopic therapy with curative intent. The currently accepted surveillance regime uses white light endoscopy together with random biopsies, but has poor sensitivity and discards information from numerous light-tissue interactions that could be exploited to probe structural, functional, and molecular changes in the tissue. Advanced optical methods are now emerging that are highly sensitive to these changes and hold potential to improve surveillance of Barrett's oesophagus if they can be applied endoscopically. The next decade will see some of these exciting new methods applied to surveillance of Barrett's oesophagus in new device architectures for the first time, potentially leading to a long-awaited improvement in the standard of care.