Modern medicine faces a major challenge in preventing, diagnosing, and treating cancer, especially in its early stages. Current tools for early detection and minimally invasive treatment are insufficient. Laser-based nonlinear endoscopy combining CARS, SHG, and TPEF emerges as a promising solution for cancer diagnostics by detecting molecular changes in tissue for differentiating cancer from healthy tissue. We developed an endomicroscopic system for head and neck cancer diagnosis and femtosecond laser ablation of tissue. The system has been validated through ex-vivo measurements on patient tissue slices and machine learning methods are being developed for quantitative comparison with standard H&E histopathology.
Acknowledgements:
Funding from the European Community’s Horizon 2020 Programme under the grant agreement No. 860185 (PHAST), No 101016923 (CRIMSON) and from the German Federal Ministry of Education and Research (BMBF): within the project TheraOptik (FKZ 13GW0370E) and LPI (Grant Number 13N15467) is acknowledged.
We present here the concept of a MEMS-mirror based nonlinear endomicroscopic probe for coherent anti-Stokes Raman scattering (CARS), two-photon excitation fluorescence (TPEF), and second harmonic generation (SHG). The rigid probe head is 5 mm in diameter and 4 cm in length, offering a large field of view (FOV) with a high numerical aperture (NA). It incorporates a double-core fiber delivering two excitation wavelengths of CARS in isolated cores, with a large cladding area to increase the collection efficiency of the nonlinear signal from the tissue. A diffractive grating element is included in the probe to compensate for the spatial offset of two emission cores.
SignificanceConventional diagnosis of laryngeal cancer is normally made by a combination of endoscopic examination, a subsequent biopsy, and histopathology, but this requires several days and unnecessary biopsies can increase pathologist workload. Nonlinear imaging implemented through endoscopy can shorten this diagnosis time, and localize the margin of the cancerous area with high resolution.AimDevelop a rigid endomicroscope for the head and neck region, aiming for in-vivo multimodal imaging with a large field of view (FOV) and tissue ablation.ApproachThree nonlinear imaging modalities, which are coherent anti-Stokes Raman scattering, two-photon excitation fluorescence, and second harmonic generation, as well as the single photon fluorescence of indocyanine green, are applied for multimodal endomicroscopic imaging. High-energy femtosecond laser pulses are transmitted for tissue ablation.ResultsThis endomicroscopic system consists of two major parts, one is the rigid endomicroscopic tube 250 mm in length and 6 mm in diameter, and the other is the scan-head (10 × 12 × 6 cm3 in size) for quasi-static scanning imaging. The final multimodal image accomplishes a maximum FOV up to 650 μm, and a resolution of 1 μm is achieved over 560 μm FOV. The optics can easily guide sub-picosecond pulses for ablation.ConclusionsThe system exhibits large potential for helping real-time tissue diagnosis in surgery, by providing histological tissue information with a large FOV and high resolution, label-free. By guiding high-energy fs laser pulses, the system is even able to remove suspicious tissue areas, as has been shown for thin tissue sections in this study.
Here, we present a new handheld multiphoton endomicroscopic system designed for tumor diagnosis in the head and neck region. It consists of an approximate 25-cm-long rigid endomicroscopic probe with two variants (0° and 45° bended tip), connected to a handheld scan-head. The system can achieve a field of view ⪆600 µm for Coherent Anti-stokes Raman Scattering (CARS) and other nonlinear imaging modalities by a non-de-scanned detection and using a de-scanned confocal imaging channel to detect light from tissue labeled with Indocyanine Green (ICG). Furthermore, high-power femtosecond laser pulses can be transmitted through the system for precise tissue ablation which was considered in the optical design of the probe.
Here, we present a new handheld multiphoton endomicroscopic system for tumor diagnosis in the head and neck region. It consists of an approx. 25 cm long rigid endomicroscopic probe with two variants (0° and 45° bended tip), connected to a handheld scan-head. The system can achieve a field of view > 600 μm for coherent anti-Stokes Raman scattering (CARS) and other nonlinear imaging techniques by a non-descanned detection channel, and laser confocal imaging with indocyanine green (ICG) by a descanned detection channel. Furthermore, high-power femtosecond laser pulses can be transmitted through the system for precise tissue ablation without the risk of damaging the optical components.
Here, we report a new handheld endoscopic system for nonlinear multimodal imaging of the head and neck region. It has a long rigid endomicroscopic probe with two versions (0° and 45° bended tip), connecting with a compact scan-head of approx. 10×12×6 cm3 size. The rigid probe is 6 mm in diameter and 24 cm long and allows diffraction-limited multiphoton imaging of tissue with at least 430 μm field of view and sub-micron resolution. The signals of Coherent anti-Stokes Raman Scattering (CARS), second harmonic generation (SHG), and two-photon excited fluorescence (TPEF) are collected by a non-descanned detection path in the scan-head, and the fluorescence of Indocyanine green (ICG) labeled lesions is detected by a confocal descanned configuration. Furthermore, this system is capable of guiding high-power femtosecond laser pulses for tissue ablation without the risk of damaging optical glass components.
This work presents the design and implementation of an endoscopic probe for point-of-care diagnosis of bladder cancer, with an outer diameter of 4.5 mm that allows for in-vivo usage. This triple-modality device can deliver volumetric OCT images, optoacoustic tomograms, and single point Raman spectroscopy that target complementary biomarkers. The probe features a piezo-based fiber scanner, which delivers the illumination or excitation light for all modalities, with a maximum Field of View of 1.6 mm. The same path is used for light collection for OCT imaging. A separate fiber is used for detection of the Raman signals, while two additional fibers with microcavity tips sense the ultrasonic waves for optoacoustic tomography. A hyperchromatic micro-optical objective provides a working distance optimized for each modality. The probe housing is produced by selective laser-induced etching of fused silica.
Non-linear endoscopic imaging probes allow for in-vivo, label free tissue histology and thus bring tumour treatment to a new level providing accurate, real time diagnostics. Here we present an endomicroscopic imaging probe for coherent anti-Stokes Raman scattering (CARS) imaging based on a fiber piezo scanner at the distal side of the probe. One of the main hurdles in the implementation of CARS imaging in all-fiber solutions is the generation of a background four-wave-mixing (FWM) signal within the delivery fiber by the Stokes- and pump lasers involved in the process of generation of the nonlinear image. We developed and realised a novel solution based on a silica double-core double-clad (DCDC) fiber, which allows a separate guiding of the exciting Stokes- and pump laser radiation in two separate cores of the delivery fiber. The optical design of the endoscopic probe allows perfect overlap and focusing of the Stokes and pump lasers across the full field of view of the probe.
A miniature endomicroscope is presented that combines a large field-of-view (up to 1.7 mm) for OCT-imaging and a high-resolution mode with 360 μm field-of-view (NA = 0.5) for multi-photon fluorescence or OCT imaging. The 4.7x magnification variation is achieved by the axial positioning of an inner micro-optical lens group using an integrated electro-magnetic z-actuator. A reverse fiber-optic piezotube-scanner with minimized length is employed for the image acquisition by resonant spiral scanning. With the probe diameter of 2.7 mm and a rigid length of about 60 mm, the approach may pave the way to clinical applications of these two modalities in a single probe.
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