Thermal lensing in biologic medium

Motamedi, Massoud; Welch, Ashley J.; Cheong, Wai-Fung; Ghaffari, Shahriar; Tan, Oon Tian

doi:10.1109/3.180

Cited by 18 publications

(7 citation statements)

References 5 publications

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“…ear photodynamic therapy, [17][18][19][20][21][22] focusing of light through multimode fibers, [23][24][25] as well as for applications employing high power beams, which experience thermal nonlinearity in a variety of samples. 26,27 In this work we study the focusing of light through a scattering medium in the presence of nonlinearity using adaptive optimization of the input wavefront, and show that focusing nonlinearity in fact serves to increase the fraction of total power that the focus contains. Since adaptive optimization iteratively adjusts the solution rather than relying on calibration measurements, it is well-suited for nonlinear media.…”

Section: Introductionmentioning

confidence: 99%

Focusing light by wavefront shaping through disorder and nonlinearity

Frostig

Small

Daniel

et al. 2017

Optica

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Wavefront shaping is a powerful technique that can be used to focus light through scattering media, which can be important for imaging through scattering samples such as tissue. The method is based on the assumption that the field at the output of the medium is a linear superposition of the modes traveling through different paths in the medium. However, when the scattering medium also exhibits nonlinearity, as may occur in multiphoton microscopy, this assumption is violated and the applicability of wavefront shaping becomes unclear. Here we show, using a simple model system with a scattering layer followed by a nonlinear layer, that with adaptive optimization of the wavefront light can still be controlled and focused through a scattering medium in the presence of nonlinearity. Notably, we find that moderate positive nonlinearity can serve to significantly increase the focused fraction of power, whereas negative nonlinearity reduces it. arXiv:1607.08105v2 [physics.optics]

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Section: Introductionmentioning

confidence: 99%

Focusing light by wavefront shaping through disorder and nonlinearity

Frostig

Small

Daniel

et al. 2017

Optica

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“…5 When ablating biological tissue, the nature and extent of photothermal effects of laser-tissue interactions are governed by the distribution of light within the tissues, tissue temperature, the duration for which tissue is exposed to elevated temperature, and the tissue thermal properties of heat capacity and diffusivity. 11,15,20,26,34 With these variables in mind, in the absence of a change in intraoperative parameters, any changes seen in ablation dynamics in subsequent ablations compared to ablation of naive tissue can be assumed to be attributable to changes in light distribution within the tissue and changes in tissue thermal properties following exposure to an initial thermal dose. In this study, we investigated how these changes affect the rate of tissue ablation and maximal achievable ablative area.…”

Section: Discussionmentioning

confidence: 99%

Ablation dynamics of subsequent thermal doses delivered to previously heat-damaged tissue during magnetic resonance–guided laser-induced thermal therapy

Munier¹,

Hargreaves²,

Patel³

et al. 2019

Journal of Neurosurgery

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OBJECTIVEIntraoperative dynamics of magnetic resonance–guided laser-induced thermal therapy (MRgLITT) have been previously characterized for ablations of naive tissue. However, most treatment sessions require the delivery of multiple doses, and little is known about the ablation dynamics when additional doses are applied to heat-damaged tissue. This study investigated the differences in ablation dynamics between naive versus damaged tissue.METHODSThe authors examined 168 ablations from 60 patients across various surgical indications. All ablations were performed using the Visualase MRI-guided laser ablation system (Medtronic), which employs a 980-nm diffusing tip diode laser. Cases with multiple topographically overlapping doses with constant power were selected for this study. Single-dose intraoperative thermal damage was used to calculate ablation rate based on the thermal damage estimate (TDE) of the maximum area of ablation achieved (TDEmax) and the total duration of ablation (tmax). We compared ablation rates of naive undamaged tissue and damaged tissue exposed to subsequent thermal doses following an initial ablation.RESULTSTDEmax was significantly decreased in subsequent ablations compared to the preceding ablation (initial ablation 227.8 ± 17.7 mm2, second ablation 164.1 ± 21.5 mm2, third ablation 124.3 ± 11.2 mm2; p = < 0.001). The ablation rate of subsequent thermal doses delivered to previously damaged tissue was significantly decreased compared to the ablation rate of naive tissue (initial ablation 2.703 mm2/sec; second ablation 1.559 mm2/sec; third ablation 1.237 mm2/sec; fourth ablation 1.076 mm/sec; p = < 0.001). A negative correlation was found between TDEmax and percentage of overlap in a subsequent ablation with previously damaged tissue (r = −0.164; p < 0.02).CONCLUSIONSAblation of previously ablated tissue results in a reduced ablation rate and reduced TDEmax. Additionally, each successive thermal dose in a series of sequential ablations results in a decreased ablation rate relative to that of the preceding ablation. In the absence of a change in power, operators should anticipate a possible reduction in TDE when ablating partially damaged tissue for a similar amount of time compared to the preceding ablation.

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“…Misalignment in the optical system for the z-scan would introduce aberrations not accounted for in the first-order model, which considers only a Gaussian wavefront. Further, it has been demonstrated that thermal lensing in water results in convective flow processes introducing nonlinear aberrations into the steady-state reading [20,[35][36][37].…”

Section: Discussionmentioning

confidence: 99%

First-order model of thermal lensing in a virtual eye

et al. 2009

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An ABCD beam-propagation method was used to build a first-order mathematical model of a thermal lens effect from a near-infrared laser beam in water and ocular media. The model was found to fit experimental z-scan data best when the thermo-optic coefficient dn/dT of liquid water at 292 K was -4.46x10(-5) K(-1). The physiological parameters of the human eye were simulated in a simple eye model using this fitted dn/dT value. Conservative model simulations for 1150 and 1318 nm laser radiation include parameter sets used in experimental ocular exposures performed by Zuclich et al. [Health Phys.92, 15 (2007)] to illustrate the transient response of the thermal lens approaching the limits of the retinal damage thresholds for equivalent laser radiation sources.

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Thermal lensing in biologic medium

Cited by 18 publications

References 5 publications

Focusing light by wavefront shaping through disorder and nonlinearity

Focusing light by wavefront shaping through disorder and nonlinearity

Ablation dynamics of subsequent thermal doses delivered to previously heat-damaged tissue during magnetic resonance–guided laser-induced thermal therapy

First-order model of thermal lensing in a virtual eye

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