Stress Relaxation of Porcine Septal Cartilage During Nd:YAG (λ=1.32 μm) Laser Irradiation: Mechanical, Optical, and Thermal Responses

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 σ(t), integrated backscattered light intensity I(t) from a He-Ne probe laser (λ=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 (λ=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 ΔI(t)/I0) may be used to control the process of laser-assisted cartilage reshaping and minimize nonspecific thermal injury due to uncontrolled heating. © 1998 Society of Photo-Optical Instrumentation Engineers.

Laser-Time Interaction XII: Photochemical, Photothermal, and Photomechanical

“…It is evident that the application of high-power pulsed lasers will significantly potentiate these effects. This especially concerns the combination of pharmaceutical methods with laser perforation of skin structures 32 and ultrasonic treatment 33 . It seems very promising to combine ultrasonic and photodynamic therapies 33 .…”

“…This especially concerns the combination of pharmaceutical methods with laser perforation of skin structures 32 and ultrasonic treatment 33 . It seems very promising to combine ultrasonic and photodynamic therapies 33 . Recently, we demonstrated that, when the prostate gland was subjected to intraurethral irradiation with the aid of a semiconductor laser, the efficiency of drug delivery to internal organs increased due to local blood circulation enhancement stimulated by a photothermal effect 35 .…”

“…In order to overcome the barrier functions of stratum corneum, researchers developed a number of techniques. The latter include stratum comeum laser ablation performed with the aid of pulsed lasers 30 , photomechanical and acoustic wave generation ■ , forced laser drug injection based on skin perforation 32 , and combined laser-ultrasound treatment 33 . In carrying out these investigations, a spectro-chromatographic technique was developed to study possible effects of radiation on drug properties ' In this section, we shall consider a number of unpublished results obtained earlier.…”

“…During tissue ischemia, xanthine dehydrogenase is converted into the oxidant-producing xanthine oxidase while the breakdown of ATP leads to the accumulation of hypoxanthine. Sudden reintroduction of oxygen at the time of reperfusion will then lead to the conversion of hypoxanthine into xanthine by xanthine oxidase, which is associated with massive generation of reactive oxygen species, primarily Superoxide anion 33 . This results in the induction of oxidative stress at the level of vascular epithelium that promotes complement activation leading to the formation of inflammatory agents which recruit and activate host neutrophils 36 .…”

“…Ischemia/reperfusion (I/R) injury is a classical physiological insult responsible for severe tissue damage in a variety of common pathological conditions (including myocardial infarction, stroke, acute kidney and liver failure, pulmonary and hemorrhagic shock, and organ transplant rejection) 33 " 35 . During tissue ischemia, xanthine dehydrogenase is converted into the oxidant-producing xanthine oxidase while the breakdown of ATP leads to the accumulation of hypoxanthine.…”