Stress wave focusing transducers

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Description

Conversion of laser radiation to mechanical energy is the fundamental process behind many medical laser procedures, particularly those involving tissue destruction and removal. Stress waves can be generated with laser radiation in several ways: creation of a plasma and subsequent launch of a shock wave, thermoelastic expansion of the target tissue, vapor bubble collapse, and ablation recoil. Thermoelastic generation of stress waves generally requires short laser pulse durations and high energy density. Thermoelastic stress waves can be formed when the laser pulse duration is shorter than the acoustic transit time of the material: {tau}{sub c} = d/c{sub s} where d ... continued below

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6 p.

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Visuri, S.R., LLNL May 15, 1998.

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Description

Conversion of laser radiation to mechanical energy is the fundamental process behind many medical laser procedures, particularly those involving tissue destruction and removal. Stress waves can be generated with laser radiation in several ways: creation of a plasma and subsequent launch of a shock wave, thermoelastic expansion of the target tissue, vapor bubble collapse, and ablation recoil. Thermoelastic generation of stress waves generally requires short laser pulse durations and high energy density. Thermoelastic stress waves can be formed when the laser pulse duration is shorter than the acoustic transit time of the material: {tau}{sub c} = d/c{sub s} where d = absorption depth or spot diameter, whichever is smaller, and c{sub s} = sound speed in the material. The stress wave due to thermoelastic expansion travels at the sound speed (approximately 1500 m/s in tissue) and leaves the site of irradiation well before subsequent thermal events can be initiated. These stress waves, often evolving into shock waves, can be used to disrupt tissue. Shock waves are used in ophthalmology to perform intraocular microsurgery and photodisruptive procedures as well as in lithotripsy to fragment stones. We have explored a variety of transducers that can efficiently convert optical to mechanical energy. One such class of transducers allows a shock wave to be focused within a material such that the stress magnitude can be greatly increased compared to conventional geometries. Some transducer tips could be made to operate regardless of the absorption properties of the ambient media. The size and nature of the devices enable easy delivery, potentially minimally-invasive procedures, and precise tissue- targeting while limiting thermal loading. The transducer tips may have applications in lithotripsy, ophthalmology, drug delivery, and cardiology.

Physical Description

6 p.

Notes

OSTI as DE98058848

Other: FDE: PDF; PL:

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  • Optical Society of America spring topical meetings, Orlando, FL (United States), 8-11 Mar 1998

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  • Other: DE98058848
  • Report No.: UCRL-JC--130697
  • Report No.: CONF-9803112--
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 302214
  • Archival Resource Key: ark:/67531/metadc678247

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Office of Scientific & Technical Information Technical Reports

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  • May 15, 1998

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • April 6, 2017, 5:55 p.m.

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Visuri, S.R., LLNL. Stress wave focusing transducers, article, May 15, 1998; California. (digital.library.unt.edu/ark:/67531/metadc678247/: accessed April 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.