Internal structuring of silica glass fibers: Requirements for scattered light applicators for the usability in medicine
-
Jenny Köcher
,
Verena Knappe
Abstract
Background:
Diffuser fibers have been used for some time in the fields of laser-induced thermotherapy and photodynamic therapy. For their applicability the breaking strength, the thermostability and a homogeneous radiation profile are of great importance. Flexible applicators offer special benefits because they introduce a totally new range of application possibilities.
Objective:
The aim of the presented investigations was to develop a totally new flexible diffuser fiber generation which can be produced cheaper and without the use of any further materials. For this purpose it was proposed to induce scattering micro dots directly into silica fibers by generating a local change of the refractive index in the core of the optical fiber. The resulting diffuser was expected to create a homogeneous radiation profile containing at least 80% of the light coupled into the optical fiber, i.e. less than 20% prograde (forward) emission.
Materials and methods:
On the basis of former research results, scattering micro dots were induced linearly into the core of an optical silica fiber through a multiple photon process using a femtosecond laser. In addition to the macroscopic optical control by means of a microscope, the form of the radiation profile was examined as well as the non-scattered forward emission which depends on a variety of influencing factors. The processing was optimized according to the observations made. The thermostability of the developed prototypes was assessed by using a thermocamera, and the minimal bending radius was determined. Finally the prototypes were tested and validated ex vivo using porcine liver.
Results:
An influence of the processing power, the number and radial position of the scattering micro dots as well as the therapeutic coupled-in wavelength onto the form of the radiation profile and the non-scattered forward emission was determined. Both the form of the radiation profile and the prograde emission were found to be independent of the therapeutic laser power coupled into the fiber. The developed prototype had a nearly homogeneous radiation profile, a forward emission of 12.8±2.1% in average, and a minimum bending radius of 31±6 mm.
Conclusion:
The non-scattered forward emission of the developed diffusers was within the objective of below 20% and the radiation profile was very nearly homogeneous. In order to improve the reproducibility of the production process, an improved fixation apparatus needs to be developed.
Zusammenfassung
Hintergrund:
Streulichtapplikatoren werden seit langem für die Laserinduzierte Thermotherapie und die Photodynamische Therapie eingesetzt. Von besonderer Bedeutung für die Anwendbarkeit sind hierbei die Bruchfestigkeit und Thermostabilität der Applikatoren sowie ein homogenes Abstrahlprofil. Flexible Applikatoren bieten besondere Vorzüge, da sie ein vollkommen neues Anwendungsspektrum eröffnen.
Zielsetzung:
Ziel der hier vorgestellten Untersuchungen war es daher, eine vollkommen neue flexible Streulichtapplikator-Generation zu entwickeln, die kosten- und zeiteffizienter hergestellt werden kann und ohne die Verwendung zusätzlicher Materialien auskommt. Hierzu sollten Streuzentren direkt in der optischen Faser über eine lokale Brechungsindexänderung im Glasfaserkern erzeugt werden, wobei ein gleichmäßiges Intensitätsprofil der Streustrahlung erzeugt werden sollte, welches mindestens 80% der eingekoppelten Strahlung beinhaltet (ungestreuter Vorwärtsanteil kleiner 20%).
Material und Methoden:
Auf Grundlage früherer Forschungsergebnisse wurden mit Hilfe eines Femtosekundenlasers durch einen Multi-Photonen-Prozess Streuzentren direkt im Faserkern von Quarzglasfasern linienförmig, entlang der Faserachse verlaufend, induziert. Neben der optischen Kontrolle mit Hilfe eines Mikroskops, wurden die Form des Abstrahlprofils sowie der ungestreute Vorwärtsanteil in Abhängigkeit verschiedener Einflussfaktoren untersucht und der Bearbeitungsprozess optimiert. Die entwickelten Prototypen wurden mit Hilfe einer Thermokamera auf ihre Thermostabilität hin untersucht und der minimale Biegeradius wurde ermittelt. Schlussendlich wurden die Prototypen ex vivo in Schweineleber getestet und validiert.
Ergebnisse:
Es konnte ein Einfluss der Bearbeitungsleistung, der Anzahl und radialen Lage der Streuzentren sowie der in den Applikator eingekoppelten Wellenlänge auf das Streuverhalten beobachtet werden. Die Laserleistung des in den Streuapplikator eingekoppelten Lichts hatte keinen Einfluss auf die Form des Abstrahlprofils sowie den ungestreuten Vorwärtsanteil. Für den entwickelten Prototypen konnte ein annähernd homogenes Streustrahlungsprofil bei einem ungestreuten Vorwärtsanteil von durchschnittlich 12,8 ± 2,1% erreicht werden. Der minimale Biegeradius betrug 31 ± 6 mm. In den Ex-Vivo-Versuchen wurde bei Einsatz eines Nd:YAG-Lasers eine optimale Behandlungsleistung von 21 W ermittelt.
Fazit:
Der Vorwärtsanteil der entwickelten Streulichtapplikatoren liegt im Rahmen des gesetzten Ziels von unter 20%. Das erreichte Streustrahlungsprofil ist annähernd homogen. Um die Reproduzierbarkeit des Bearbeitungsprozesses weiter zu verbessern ist die Entwicklung einer verbesserten Faserfixierung erforderlich.
Acknowledgments
Financially supported by BMWI, Zentrales Innovationsprogramm Mittelstand (ZIM), support code KF 2821701KJ1: “LaDiff – Forschung und Entwicklung der Laserbearbeitung von neuen Diffusoren für medizinische Anwendungen”.
Conflict of interest statement: Authors state no conflict of interest. All authors have read the journal’s Publication Ethics and Publication Malpractice Statement available at the journal’s website and hereby confirm that they comply with all its parts applicable to the present scientific work.
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©2016 Walter de Gruyter GmbH, Berlin/Boston
Artikel in diesem Heft
- Frontmatter
- Editorial
- Laser-advanced new methods for diagnostics and therapeutics
- Announcement
- Upcoming issues in 2016 – Call for papers
- Magazine section
- Snapshots
- Review
- Status and opportunities for future use of terahertz radiation for clinical applications
- Original contributions
- Quantitative assessment of oral microstructural and microvascular changes in late oral radiation toxicity, using noninvasive in-vivo optical coherence tomography
- Ex-vivo investigation on the potential of 1470 nm diode laser light for enucleation of uterine leiomyoma
- Clinical observation of a professional tattooing procedure and evolutionary study of the skin damage provoked
- Preliminary research reports
- Design of a new two-dimensional optical biosensor using photonic crystal waveguides and a nanocavity
- Internal structuring of silica glass fibers: Requirements for scattered light applicators for the usability in medicine
- Short communication
- Optical fiber solutions for laser ablation of tissue and immunostimulating interstitial laser thermotherapy – Product development in the network of developers, industry and users
- Press release
- LMTB winner of the Innovation Award Berlin Brandenburg 2015
- Congress announcements
- Congresses 2016
Artikel in diesem Heft
- Frontmatter
- Editorial
- Laser-advanced new methods for diagnostics and therapeutics
- Announcement
- Upcoming issues in 2016 – Call for papers
- Magazine section
- Snapshots
- Review
- Status and opportunities for future use of terahertz radiation for clinical applications
- Original contributions
- Quantitative assessment of oral microstructural and microvascular changes in late oral radiation toxicity, using noninvasive in-vivo optical coherence tomography
- Ex-vivo investigation on the potential of 1470 nm diode laser light for enucleation of uterine leiomyoma
- Clinical observation of a professional tattooing procedure and evolutionary study of the skin damage provoked
- Preliminary research reports
- Design of a new two-dimensional optical biosensor using photonic crystal waveguides and a nanocavity
- Internal structuring of silica glass fibers: Requirements for scattered light applicators for the usability in medicine
- Short communication
- Optical fiber solutions for laser ablation of tissue and immunostimulating interstitial laser thermotherapy – Product development in the network of developers, industry and users
- Press release
- LMTB winner of the Innovation Award Berlin Brandenburg 2015
- Congress announcements
- Congresses 2016
