Physical properties of hydrated tissue determined by surface interferometry of laser-induced thermoelastic deformation

Dark, Marta; Perelman, Lev T.; Itzkan, Irving; Schaffer, Jonathan; Feld, Michael S.

doi:10.1088/0031-9155/45/2/318

Cited by 28 publications

(28 citation statements)

References 12 publications

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“…Obviously, the additional biological components in the tissue contribute to the observed thermal expansion. However, the available data on thermal tissue expansion and the related Grüneisen coefficient suggest no large differences between water and tissue [29, 30, 31, 32]. Only fat tissue has a several times higher thermal expansion coefficient [29].…”

Section: Resultsmentioning

confidence: 99%

Imaging thermal expansion and retinal tissue changes during photocoagulation by high speed OCT

Müller¹,

Ptaszynski²,

Schlott³

et al. 2012

Biomed. Opt. Express

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Visualizing retinal photocoagulation by real-time OCT measurements may considerably improve the understanding of thermally induced tissue changes and might enable a better reproducibility of the ocular laser treatment. High speed Doppler OCT with 860 frames per second imaged tissue changes in the fundus of enucleated porcine eyes during laser irradiation. Tissue motion, measured by Doppler OCT with nanometer resolution, was correlated with the temperature increase, which was measured non-invasively by optoacoustics. In enucleated eyes, the increase of the OCT signal near the retinal pigment epithelium (RPE) corresponded well to the macroscopically visible whitening of the tissue. At low irradiance, Doppler OCT revealed additionally a reversible thermal expansion of the retina. At higher irradiance additional movement due to irreversible tissue changes was observed. Measurements of the tissue expansion were also possible in vivo in a rabbit with submicrometer resolution when global tissue motion was compensated. Doppler OCT may be used for spatially resolved measurements of retinal temperature increases and thermally induced tissue changes. It can play an important role in understanding the mechanisms of photocoagulation and, eventually, lead to new strategies for retinal laser treatments.

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Section: Resultsmentioning

confidence: 99%

Imaging thermal expansion and retinal tissue changes during photocoagulation by high speed OCT

Müller¹,

Ptaszynski²,

Schlott³

et al. 2012

Biomed. Opt. Express

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“…Water may play a significant role in the reshaping process since evaporation occurs during laser irradiation (with a subsequent increase in the concentrations of collagen and other proteins within the matrix). It is well known that the degree of hydration greatly influences tissue ablation and shrinkage behavior [18,33,34]. Thus this hypothetical bound to free transition of water may increase the mobility of constitutive elements of the matrix, which may lead to stress relaxation.…”

Section: Introductionmentioning

confidence: 99%

Characterization of temperature dependent mechanical behavior of cartilage

et al. 2003

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The anisotropic mechanical behavior of cartilage was quantitatively analyzed in the transversely and longitudinally oriented specimens. Viscoelastic behavior appeared to be strongly dependent on the water content. Using empirically determined estimates of the transition zone temperature range accompanying stress relaxation, the activation energy for stress relaxation was calculated using time and temperature superposition theory and WLF equation. Further investigation of the molecular changes, which occur during laser irradiation, may assist in understanding the thermal and mechanical behavior of cartilage and how the reshaping process might to be optimized.

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“…We can approximate the threedimensional temperature distribution in our model that attenuate with an effective penetration depth as [7]:…”

Section: Estimation Of Measurable Surface Displacementmentioning

confidence: 99%

Non-contact photoacoustic tomography with a laser Doppler vibrometer

Wang

Tian

et al. 2014

SPIE Proceedings

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Most concurrent photoacoustic tomography systems are based on traditional ultrasound measurement regime, which requires the contact or acoustic coupling material between the biological tissue and the ultrasound transducer. This study investigates the feasibility of non-contact measurement of photacoustic signals generated inside biomedical tissues by observing the vibrations at the surface of the tissues with a commercial laser Doppler vibrometer. The vibrometer with 0-2MHz measurement bandwidth and 5 MHz sampling frequency was integrated to a conventional rotational PAT data acquisition system. The data acquisition of the vibrometer was synchronized to the laser illumination from an Nd:YAG laser with output at 532nm. The laser energy was tuned to 17.5mJ per square centimeter. The PA signals were acquired at 120 angular locations uniformly distributed around the scanned objects. The frequency response of the measurement system was first calibrated. 2-inch-diamater cylindrical phantoms containing small rubber plates and biological tissues were afterwards imaged. The phantoms were made from 5% intralipid solution in 10% porcine gelatin to simulate the light scattering in biological tissue and to backscatter the measurement laser from the vibrometer. Time-domain backprojection method was used for the image reconstruction. Experiments with real-tissue phantoms show that with laser illumination of 17.5 mJ/cm 2 at 532 nm, the non-contact photoacoustic (PA) imaging system with 15dB detection bandwidth of 2.5 MHz can resolve spherical optical inclusions with dimension of 500µm and multi-layered structure with optical contrast in strongly scattering medium. The experiment results prompt the potential implementation of the non-contact PAT to achieve "photoacoustic camera".

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Physical properties of hydrated tissue determined by surface interferometry of laser-induced thermoelastic deformation

Cited by 28 publications

References 12 publications

Imaging thermal expansion and retinal tissue changes during photocoagulation by high speed OCT

Imaging thermal expansion and retinal tissue changes during photocoagulation by high speed OCT

Characterization of temperature dependent mechanical behavior of cartilage

Non-contact photoacoustic tomography with a laser Doppler vibrometer

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