Endovenous Laser Application

Summary

Introduction: Endovenous laser ablation is becoming a common procedure in clinical routine. Although technical improvements and certain laser parameters are available there is demand to improve the situation by developing feedback-systems, thus getting online information for the clinical outcome and preventing for under- and over-treatment.

Methods: By means of Monte Carlo simulation the potential of detecting signals due to heat induced shrinkage of the vessel was investigated. Remission spectra of native and coagulated vein tissue were compared to identify potential parameters for signalling the physiological change of the tissue due to the heating process. A miniaturized temperature sensor was developed for intraluminal measurements during laser energy application.

Results: Monte Carlo simulation shows that the detection of remitted light from the vessels wall is possible for small vessel calibres of less than 6 mm in diameter. Remission spectra of native compared to coagulated vein tissue differ. While native tissue relates more to the content of deoxy-hemoglobin, the spectra of coagulated tissue relates more to the oxy-hemoglobin state. Based on the principle of temperature dependent fluorescence emission a miniaturized sensor was developed which can be used in the light field of radial emitting fibres.

Conclusion: Several optical changes for online-monitoring of signals during endovenous laser ablation showed potential to serve as feedback mechanism. Up to now, only the measurement of the endoluminal temperature could be realized. Further investigations are needed to find suitable technical realization to prevent for under- or overheating during endovenous laser ablation.

Zusammenfassung

Einleitung: Die endovenöse Laserablation nimmt einen zunehmenden Stellenwert in der klinischen Routine ein. Obwohl technische Verbesserungen und spezielle Laser-Behandlungsprotokolle zur Verfügung stehen, besteht der Wunsch nach weiterer Optimierung und der Entwicklung von Feedback-Systemen. Sie sollen Informationen über akute Effekte oder auch des klinischen Resultats liefern, sowie während der Anwendung Hinweise auf eine Unter- oder Überbehandlung geben.

Methode: Zunächst wurde mittels Monto-Carlo-Simulationsrechnungen der temperaturinduzierte Schrumpfungseffekt des Gefäßlu-mens modelliert und untersucht, ob die abstandsabhängige Remissionsintensität der Gewebewand als Signal genutzt werden kann. In einem weiteren Schritt wurde die spektrale Remissionsänderung von nativem und koagulierten Zustand verglichen, um daraus potenzielle Informationsparameter zu extrahieren. Schließlich wurde ein Temperatursensor für intraluminale Messungen im Bestrahlungsfeld während der Laserenergieapplikation entwickelt.

Ergebnisse: Die Monte-Carlo-Untersuchung belegt die Erfassung von Remissionslicht als Schrumpfungsparameter nur bei kleinsten Gefäßdurchmesser. Spektrale Unterschiede bei behandelten versus unbehandelten Venengewebes sind vorhanden, unmittelbare Informationen können allerdings nur schwer erfasst werden. Auf der Basis der temperaturabhängigen spektralen Fluoreszenzemission wurde ein Temperatursensor entwickelt und erfolgreich im Rinder-Fuß-Modell getestet.

Schlussfolgerung: Die dargestellten Untersuchungen zeigen, dass verschiedene optische Änderungen als Signal für ein Feedback-System während der Laserlichtapplikation genutzt werden könnten. Allerdings konnte bisher nur die Temperaturmessung im Strahlungsfeld realisiert werden. Weitere Untersuchungen sind für eine technische Umsetzung der Entwicklungen notwendig, um klinisch die Sicherheit und Reproduzierbarkeit der endoluminalen Laserlichtapplikation weiter zu optimieren.

Keywords

Varicosis - laser - temperature - monitoring

Schlüsselwörter

Varikosis - Laser - Temperatur - Monitoring

• Reference

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