title: A feasibility study on femtosecond laser thrombolysis.
abstract: OBJECTIVE
  In this feasibility study, we investigate possible femtosecond laser thrombolysis.
  
  
  BACKGROUND
  Because of low pulse energies, femtosecond laser surgery inherently minimizes side effects on the surrounding tissue. Moreover, current femtosecond laser sources as well as fiber technology allow consideration of catheter-based treatments.
  
  
  METHODS
  Two femtosecond laser systems (λ=800 nm, λ=1030 nm) along with a three dimensional (3D) scanner system (NA ~0.1) were used in this study. In vitro experiments were performed on porcine thrombi and blood vessels. Ablation thresholds were determined in air, by determining the pulse energy at which single shot ablation was visible under the optical microscope. Ablation rates were determined in physiological saline. Additionally, ablation of thrombi and blood vessels was monitored by means of a fiber spectrometer.
  
  
  RESULTS
  Depending upon the scan velocity, typical ablation rates for thrombi were ~0.04 mm(3)/sec. Ablation thresholds of thrombi and blood vessels differ by factors of 3 and 1.5 at laser wavelengths of 800 and 1030 nm, respectively. At a distance of 5 mm above the surface, second harmonic generation was observed in blood vessels, but not within thrombi.
  
  
  CONCLUSIONS
  The results show that a typical thrombus volume can be destroyed within a reasonable time frame. Because of the higher threshold difference of thrombi and blood vessels, the use of a laser wavelength of 800 nm is preferable. Furthermore, the detection of the second harmonic could provide a feedback mechanism to protect the vascular wall from mechanical and laser damage.
authors: 1 Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena , Jena, Germany .
authors: Johannes
authors: J
authors: Bidinger
authors: Roland
authors: R
authors: Ackermann
authors: Giorgio
authors: G
authors: Cattaneo
authors: Robert
authors: R
authors: Kammel
authors: Stefan
authors: S
authors: Nolte
mesh_terms: D055011:Ablation Techniques; D000818:Animals; D005240:Feasibility Studies; D007834:Lasers; D061185:Mechanical Thrombolysis / Q000379:methods*; D023421:Models, Animal; D013552:Swine