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Fiber-based Spectroscopy – A Key to the Individual Treatment of Vascular Disease

28 Apr | By Jürgen Popp
Fiber-based Spectroscopy – A Key to the Individual Treatment of Vascular Disease
Image source: Sven Döring/Leibniz-IPHT JenaLeibniz-IPHT Jena


To optimize the in vivo diagnosis and treatment of cardiovascular disease, scientists at the Leibniz Institute of Photonic Technology (Leibniz-IPHT) have combined their know-how in the fields of fiber optics and biophotonics. An exciting project in which many challenges have been tackled.


Light is a special tool. When coupled into optical fibers, it can transmit data and information such as, for example, measurement signals. From scattering light by molecules, one can obtain molecular and biochemical information fast and contract free. “The idea was to combine both of these features to optimize the existing gap in the diagnosis and treatment of arteriosclerosis,” says Prof. Dr. Jürgen Popp, scientific director at Leibniz-IPHT. Within the European Network of Excellence for Biophotonics Photonics4life, which is coordinated by Leibniz-IPHT, the contact to the cardiologist Professor Dr. Bernhard Brehm was established. Together with him the idea was born to quickly and precisely determine the chemical composition of plaque.


The medical need for such a study is great because arteriosclerosis and its consequences – stroke and heart attack – are among the most common causes of death in western industrial nations. In this chronically progressive disease, the arterial walls build up deposits, called plaque. If and how the deposits must be treated depends on their biochemical composition. Better knowledge of the composition of the plaque would help make a more accurate risk assessment. Dangerous, so-called vulnerable, plaques could be more precisely diagnosed. Individualized medical treatment would then follow.


One established method of diagnosis of plaque is heart catheter examination, in which the form and structure of the coronary arteries can be made visible with the help of x-ray procedures using contrast agents; however, with this method, the molecular and biochemical composition of the plaque cannot be identified. Therefore, the diagnosis and individualized treatment is more difficult.




With a probe from the company EM Vision consisting of several light-guiding optical fibers, a spectroscopic analysis was performed in a model experiment in cooperation with Jena University Hospital. “We were able to show that the use of light during heart catheter examination provides precise information on the molecular composition of plaque,” says Dr. Christian Matthäus, researcher at Leibniz-IPHT.


The fiber-spectroscopic probe is not yet suited for human application because the probe head is inflexible at a length of 5-6 cm due to the integrated filters. The risk of damaging the delicate coronary arteries during examination is too high. To meet the medical need for more flexible fibers, Matthäus and his colleague Dr. Sebastian Dochow, also working at Leibniz-IPHT, requested help.


“The filters in the sensor head separate the excitation light required for Raman-spectroscopic examination from the noise generated in the fiber. We, therefore, needed a solution that replaces the filters in the probe,” said Dr. Martin Becker, a fiber technician at Leibniz-IPHT. In the framework of the joint BMBF-funded project Fiber Health Probe, Fiber Bragg gratings (periodic structures) were inscribed in the fiber core. The gratings match the wavelength of the coupled light to their defined structure. At congruence, light is reflected back at a certain wavelength; thus, only the required light is guided through the core.


This solution only works with single-mode fibers (i.e., fibers with a small core). The light collected with such fibers is too weak to record a Raman spectrum. The multi-mode fibers that are common in this field have a core with a large diameter; however, the coupled light cannot be filtered in a targeted manner in the core.


“What we need are customized fibers that can be used to collect a large amount of light and to filter light in a targeted manner,” says Dr. Dochow. To manufacture these fibers, his colleagues from the fiber optics group have at their disposal technological equipment that is, on the international level, essentially unique – from materials to all steps of the fiber manufacturing process to characterization. Together with Sebastian Dochow und Christian Matthäus, they are currently researching the applicability of multi-core fibers. In these fibers, the light is guided together through several cores and bundled at the end.


Although fiber optimization has not yet been completed, the research scientists at IPHT are already thinking ahead to the next step. Optical coherence tomography (OCT) is an imaging method for cardiovascular examination. Similar to Raman, OCT works with scattered light that interacts with the arterial walls. “For doctors, it would be ideal to obtain not only chemical information with a single device but information on the shape and size of the plaque as well,” said Dr. Dochow.


OCT and Raman work with different excitation waves. The multi-core fibers should, therefore, be developed in such a way that they can be integrated in optical coherence tomography in the future. 


The fiber optic Raman probe is suited not only for cardiovascular applications but is, generally speaking, applicable to each endoscopically accessible disease. The research scientists at IPHT are researching, in collaboration with their colleagues from Jena University Hospital, the molecular analysis of colon cancer and brain tumors. With the Institute of Physical Chemistry (IPC) at the University of Jena, IPHT is also investigating which optical fibers are suited for which tissue and how to analyze the signals obtained. Other possible application fields include non-medical uses, such as the analysis of explosives, drugs, medicine, and liquids.

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