Photoacoustic removal of occlusions from blood vessels

Abstract

Partial or total occlusions of fluid passages within the human body are removed by positioning an array of optical fibers in the passage and directing treatment radiation pulses along the fibers, one at a time, to generate a shock wave and hydrodynamic flows that strike and emulsify the occlusions. A preferred application is the removal of blood clots (thrombi and emboli) from small cerebral vessels to reverse the effects of an ischemic stroke. The operating parameters and techniques are chosen to minimize the amount of heating of the fragile cerebral vessel walls occurring during this photoacoustic treatment. One such technique is the optical monitoring of the existence of hydrodynamic flow generating vapor bubbles when they are expected to occur and stopping the heat generating pulses propagated along an optical fiber that is not generating such bubbles.

Description

UNITED STATES GOVERNMENT RIGHTS [0001] The United States Government has, rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.BACKGROUND OF THE INVENTION [0002] This invention relates generally to the removal of a partial or total occlusion from a blood vessel by generating pressure waves within the vessel through optical fiber media, and, more specifically, to the removal of a blood clot from a vessel within the human brain. The term “clot” is used herein to refer to a thrombus, embolus or some other total occlusion of a vessel. [0003] Medical procedures to open a partially or totally blocked blood vessel are available. Angioplasty has long been used to restore full blood flow in a coronary artery by mechanically deforming deposits on the arterial walls but has been less successful to open a totally occluded vessel. Laser techniques ...

AI Technical Summary

Benefits of technology

[0013] It has been found that the use of very small diameter optical fibers allows the desired shock and pressure waves to be generated with a relatively low amount of radiation pulse energy, thereby keeping the amount of heat input to the vessel at a low level. Proper thermal management according to the present invention reduces the likelihood of damaging the walls of the blood vessel adjacent the occlusion, which is especially important for the relatively thin walled vessels of the brain. Further, it is desirable that radiation pulses not being efficiently converted into the desired pressure waves be terminated in order to prevent inputting energy that heats the region without doing useful work. In addition to keeping the power input low, a liquid coolant may be introduced through the catheter to carry heat away from the region of the occlusion during the treatment.

Problems solved by technology

Further, it is desirable that radiation pulses not being efficiently converted into the desired pressure waves be terminated in order to prevent inputting energy that heats the region without doing useful work.

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