Mechanism of CW Nd:YAG laser recanalization with modified fiber tips: Influence of temperature and axial force on tissue penetration in vitro

Rudolf M. Verdaasdonk*, E. Duco Jansen, Frank C. Holstege, Cornelius Borst

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

15 Citations (Scopus)

Abstract

Modified fiber tips are used for laser angioplasty of totally occluded peripheral arteries. It has not been established, however, to what extent the mechanism of action of various laser probes is optical, thermal, or mechanical. We examined transparant contact probes (hemispherical contact probes and ball‐shaped fibers) and metal laser probes, coupled to a continuous‐wave NdYAG laser. By using homogeneous thick porcine fatty tissue samples submerged in blood plasma, tissue penetration was measured in relation to the temperature of the probe and the axial force exerted on the tissue. By using 15 W, 1 s laser pulses, the surface of transparent contact probes had to be first contaminated by carbonized tissue particles to achieve tissue penetration. Penetration increased from 1 to 10 mm per pulse when axial force increased from 20 to 100 g. Metal probes had to be sufficiently insulated from the liquid environment by water vapour entrapped in a denatured protein layer to exceed the threshold temperature of 225°C for tissue penetration. When axial force increased from 20 to 80 g at 10 W continuous exposure, the velocity of tissue penetration increased in the range from 1 to 4 mm/s. Tissue penetration by modified fiber tips is attributed to both remodeling and vaporization of tissue. With transparant contact probes, tissue is heated partly by direct light absorption and partly by a hot probe surface. Axially directed force is necessary to displace lateral non‐ablated tissue and to overcome mechanical resistance. We conclude that mechanical dilation due to axial catherization force (Dotter effect) contributes substantially to tissue penetration by transparent contact probes.

Original languageEnglish
Pages (from-to)204-212
Number of pages9
JournalLasers in surgery and medicine
Volume11
Issue number3
DOIs
Publication statusPublished - 1991
Externally publishedYes

Keywords

  • fiber optics
  • hot tip
  • laser angioplasty
  • metal laser probe
  • tissue ablation
  • transparent contact probe

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