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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - BiOp-FibEnd (Biopsy equivalent Optical Fiber multifunctional Endoscope)

Teaser

Suspect body cavity tissues are currently investigated, in-vivo, by endoscopy. Endoscopy relies on visual identification of potential problematic areas by the judgement of a trained clinician to determine whether the investigated tissue is healthy. If further investigation is...

Summary

Suspect body cavity tissues are currently investigated, in-vivo, by endoscopy. Endoscopy relies on visual identification of potential problematic areas by the judgement of a trained clinician to determine whether the investigated tissue is healthy. If further investigation is needed, part of the tissue is removed and sent to laboratories for a biopsy. This entire procedure relies on subjective judgment and ends up with delayed diagnosis. The implications of it span between an incorrect diagnosis, unnecessary psychological pressure on the patients and high costs to the system because of the need of repeated examinations.
The project aims at realizing tools that can help reduce the risk of mistakes and the costs of healthcare, and obtain quicker diagnosis, reducing the stress factors related to such investigations. In particular, this is done by combining spectroscopy to obtain information on the composition of tissues together with imaging techniques.
The project is separated in 3 parts:
- The first part is the realization of metamaterial lenses working in the mid-IR. Such lenses would allow to use longer wavelengths, beneficial for spectroscopy, without compromising imaging resolution.
- The second part is the realization of endoscopes for imaging and spectroscopy to carry the information from inside to outside the body.
- The third part is to include depth imaging information by mid-IR Optical Coherence Tomography (OCT).

Work performed

In the first 24 months the focus was on the metamaterial lens (hyperlens) and on the endoscope. For both tasks, the fabrication by fiber drawing of the structures was the central part of the project.
The fabrication of metamaterial hyperlenses for the mid-IR required multimaterial drawing of small and non-trivial structures. In particular, dielectric structures including as many as 500 metallic components, with features as small as 150 nm have been realized. The fabrication was not limited to wire-array structures, but also spanned to resonators arrays, covering both the key elements for metamaterials. Other aspects of fabricating hyperlenses have also been investigated: tapering, handling, polishing, gluing. Following the understanding and implementation of the fabrication process, the optical performances of the hyperlenses were characterized. The first step has been to test the devices at THz frequencies, where these lenses have less stringent requirements, but covering anyway a very interesting domain for spectroscopy. In this regime, imaging below the diffraction limit to resolution 13 times lower than the wavelength and focusing to a spot 176 times smaller than the wavelength have been achieved. Also, a simplified magnifying hyperlens structure - a prism instead of a taper – has been investigated both theoretically and experimentally. Preliminary investigations of the hyperlenses in the mid-IR showed promising results, but further testing is required.
The second part of the project focused on endoscopes for the mid-IR, with interest more in new materials than new structures. There are well known glasses that can be used for transmission in the mid-IR. However, most of the contain arsenic, which is not ideal for medical applications. Two approaches to this problem have been implemented. The first has been to look for an arsenic-free glass with similar transmission and fabricate devices with such glass. The glass chosen is commercially known as IG5. The fabrication process for fibers made with such glass was successfully developed. The second approach followed was that to find a more biocompatible material compared to the IG5 glass. To this purpose, an elastic polymer was used to fabricate optical fibers for the first time, polyurethane. This polymer is already largely used in medical devices. The mechanical properties of such material allowed to also realize tunable metamaterials (with the potential to actively control the imaging properties of the hyperlens), to create waveguides that allow radiation manipulation and to realize very sensitive pressure sensor. From the spectroscopy point of view, a system for tissue recognition based on visible light spectroscopy and neural network data analysis was developed.
The project outcomes resulted in, so far, 8 journal articles published, and have been presented in 25 conference contributions.

Final results

The new fabrication procedures and materials developed within the project will see large use in the fields of metamaterials, multifunctional fibers, mid- IR applications and medical devices. The project will continue such development with an eye on potential commercialization of devices by its end.
The largest contribution is expected to be given in the field of smart fabrics. The novel type of fibers realized have the ideal mechanical properties and show both optical and electrical functionalities, which are key to the realization of devices that can “feel” and interact with the environment around them.

Website & more info

More info: http://orbit.dtu.dk/en/projects/biopsy-equivalent-optical-fiber-multifunctional-endoscope.