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Journal of Biomedical Optics

Stress Relaxation of Porcine Septal Cartilage During Nd:YAG (A=1.32 um) Laser Irradiation: Mechanical, Optical and Thermal Responses
Author(s): Brian Jet-Fei Wong; Thomas E. Milner; Hong H. Kim; J. Stuart Nelson; Emil N. Sobol
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Paper Abstract

Laser-assisted cartilage reshaping is mediated by thermally induced stress relaxation, and may be used to alter cartilage morphology for reconstructive surgical procedures in the upper airway and face without carving, morselizing, or suturing. Internal stress ?(t), integrated backscattered light intensity I(t) from a He–Ne probe laser (?=632.8 nm), and radiometric surface temperature Sc(t) were measured during the reshaping of porcine nasal septal cartilage using a pulsed Nd:YAG laser (?=1.32 µm). Internal stress and integrated backscattered light intensity were observed to increase, plateau, and then decrease in similar ways during laser irradiation. The plateau region occurred when the cartilage front surface temperature approached 65 °C. I(t) was utilized in a feedback control procedure to reshape cartilage specimens from a flat to a curved geometry. Immediately following laser irradiation, the tissues were rehydrated in normal saline for 15 min while wrapped around a small dowel. A stable shape change was retained for 21 days while the specimens were stored in normal saline at 5 °C. The backscattered light intensity signal mirrors underlying changes in internal stress, and further rate of change or slope of I(t) is nearly zero when the surface temperature reaches about 65 °C. Measurements of I(t) (or, equivalently, the fractional change in integrated backscattered light intensity ?I(t)/I0) may be used to control the process of laser-assisted cartilage reshaping and minimize nonspecific thermal injury due to uncontrolled heating.

Paper Details

Date Published: 1 October 1998
PDF: 6 pages
J. Biomed. Opt. 3(4) doi: 10.1117/1.429896
Published in: Journal of Biomedical Optics Volume 3, Issue 4
Show Author Affiliations
Brian Jet-Fei Wong, Univ. of California/Irvine (United States)
Thomas E. Milner, Univ. of Texas/Austin (United States)
Hong H. Kim, Univ. of California/Irvine (United States)
J. Stuart Nelson, Univ. of California/Irvine (United States)
Emil N. Sobol, Research Ctr. for Technologica Tech Lasers (Russia)

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