Dynamics of laser induced thermoelastic expansion of native and coagulated ex-vivo soft tissue samples and their optical and thermo-mechanical properties

Abstract

The interferometric measurement of laser induced thermoelastic expansion of tissue samples can be used to estimate their optical, thermal and mechanical properties. This method was used to assess the Gruneisen coefficient and optical attenuation depth for native and coagulated ex-vivo bovine liver and porcine kidney samples. The results demonstrate decreases of 54% and 60% in the optical attenuation depth in bovine liver and porcine kidney after coagulation, respectively. The Gruneisen coefficient of native porcine kidney was determined to be 58% smaller (p < 0.05) that native bovine liver. The measured Gruneisen coefficients for native and coagulated ex-vivo porcine kidney were 0.07 ± 0.03 and 0.105 ± 0.02, respectively, whereas the Gruneisen coefficients for native and coagulated liver were 0.126 ± 0.036 and 0.127 ± 0.04, respectively. Our measurements indicate significant inter sample variability due likely to inherent variations in tissue optical absorption and surface preparation.

Interstitial photoacoustic technique and computational simulation for temperature distribution and tissue optical properties in interstitial laser photothermal interaction

“…28, the lack of a signi¯cant di®erence existed in Gruneisen parameters À of native and coagulated tissue to tissue sample variability. For simplicity, we assume in the temperature range relevant to study, À is independent to the tissue type.…”

“…However, its average value showed no obvious di®erences whether the tissue is normal or coagulated. 28 Thus, À is only a function of temperature T for most biological tissues.…”

Heat transport considerations in the mathematical analysis of the photoacoustic and photothermal effects

“…Now independently we followed an approach similar to that introduced by Arias and D Achenbach [21] to obtain the equations that describe the displacement field of the thermoelastic expansion. This equation results from the application of the second Newton's law which is the linear momentum balance, and corresponds to the thermoelastic wave equation which accounts for the propagation of the elastic deformation field [11,21,22] namely…”

“…, which we assume that is independent of the frequency and temperature, but in general it is a function of frequency, ω, and temperature, [27], pg. 27, [11,22,28], then equation (16) can be rewritten as…”

Photoacoustic detection and optical spectroscopy of high-intensity focused ultrasound-induced thermal lesions in biologic tissue

“…31,32 Because the generated PA pressure depends on the absorbed optical energy (i.e., the product of laser energy fluence and optical absorption coefficient) and the thermoacoustic efficiency of the absorbing structure, a change in at least one of these factors can result in a change in the detected PA signal. Therefore, thermally induced changes in the optical [33][34][35][36] and thermomechanical 37,38 properties of tissues have been investigated following laser-induced thermotherapy or water/saline-bath heating. However, to our knowledge, the optical and thermomechanical properties of HIFU-treated tissues have not yet been examined in conjunction with PA detection of HIFU treatments.…”