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Apparatus and method for reducing laser beam attentuation in a liquid medium

  • US 9,895,196 B2
  • Filed: 06/06/2017
  • Issued: 02/20/2018
  • Est. Priority Date: 06/09/2016
  • Status: Active Grant
First Claim
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1. A method of optimizing the irradiation of a target tissue contained in and mobile within a body lumen with laser radiation, wherein the laser radiation is associated with a laser radiation delivery device and the laser radiation is delivered to the target tissue by one of a waveguide or an optical fiber, the waveguide and the optical fiber each having a distal delivery end, wherein the distal delivery end is spaced from the target tissue, wherein the space between the distal delivery end of the guide and the target tissue is occupied by a liquid medium, and wherein the laser radiation is delivered along a light path in at least one train of laser pulses of a wavelength which is at least partially absorbed in the liquid medium, the at least one train of pulses having a first laser pulse and a second laser pulse, both pulses being substantially along the same longitudinal axis, said method comprising the steps of:

  • selecting and mounting on the laser radiation delivery device a waveguide or optical fiber type to be used in irradiating the target tissue;

    selecting at least the following parameters;

    selecting the total energy of the at least one train of pulses to be delivered to the target tissue, and selecting the distance from the distal delivery end to the target tissue;

    further comprising a controller which controls the laser radiation delivery device and implements the steps of selecting the total energy delivered by the laser radiation delivery device and selecting the distance from the distal delivery end to the target tissue;

    initiating irradiation of the target tissue for the at least one train of pulses by generating the first laser pulse along the longitudinal axis with sufficient energy (Ei) to form a vapor bubble in the liquid medium at the distal delivery end;

    allowing the vapor bubble formed to expand an amount sufficient to displace a substantial portion of the liquid medium from the space between the distal delivery end and the target tissue;

    thereafter, after the selected time delay (Td) sufficient for the formed vapor bubble to have reached its optimum extent and begun to collapse, generating the second laser pulse (Ep), the second laser pulse being delivered along the longitudinal axis to the target tissue through the formed vapor bubble, thereby minimizing the laser radiation absorbed by the liquid medium and optimizing the laser radiation reaching the target tissue;

    whereby the collapsing bubble causes the target tissue to remain substantially stationary when the second laser pulse is delivered, thus reducing retropulsion of the target tissue;

    the controller further comprising a memory including a lookup table, the lookup table including a plurality of parameters including Ei, Ep and Td, and wherein the steps of selecting the waveguide or optical fiber type, selecting the total energy to be irradiated and selecting the distance from the distal delivery end to the target causes the controller to access the lookup table to select corresponding parameters for Ei, Ep and Td and to cause the delivery device to generate and deliver laser radiation with the selected parameters for Ei, Ep and Td.

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