Nucleation and dynamics of bubbles forming around laser heated microabsorbers

Neumann, Jörg; Brinkmann, Ralf

doi:10.1117/12.633102

Cited by 8 publications

(3 citation statements)

References 20 publications

(43 reference statements)

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“…The high peak temperatures occurring at the melanosomes during irradiation lead to short living microbubbles which mechanically disrupt the RPE cells due to a short but strong volume increase [21]. Moreover, it could be observed that the radiant exposure and thus the energy required for bubble formation decreases with pulse duration [22].…”

Section: Introductionmentioning

confidence: 99%

Investigation of selective retina treatment (SRT) by means of 8 ns laser pulses in a rabbit model

et al. 2008

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Background: It has been shown that selective retina treatment (SRT) using a train of 1.7 microseconds laser pulses allows selective damage of the retinal pigment epithelium (RPE) while sparing the adjacent photoreceptors and thus avoiding laser scotoma. It was the purpose of this work to investigate SRT laser effects with Q-switched pulses of only 8 nanoseconds in duration by evaluating the angiographic and ophthalmoscopic damage thresholds and the damage range by histology in a rabbit model. Materials and Methods: A flash lamp pumped frequency doubled (532 nm) Nd:YAG laser with 8 nanoseconds pulse duration was used. In total 210 laser lesions, each calculated to be 102 mm in diameter on retina, were applied through a slit lamp onto the fundus of six eyes of Chinchilla Bastard rabbits. The rabbits were irradiated with increasing energies with single pulses and a train of 10 laser pulses at 10 Hz. After treatment fundus photography and angiography were performed to determine the damage thresholds (ED 50 -probability of RPE cell damage and neurosensory retinal damage) as well as the safety range between both thresholds (ratio of angiographic ED 86 vs. ophthalmoscopic ED 14 ). Selected histology was taken for single and repetitive pulse lesions after treatment. Results: Angiographic and ophthalmoscopic ED 50 -thresholds decreased with increasing number of pulses. For single pulse application ophthalmoscopic and angiographic ED 50 were determined to 365 and 144 mJ/cm 2 , respectively. Regarding 10 pulses 266 and 72 mJ/cm 2 were found. No retinal hemorrhages or disruptions were observed for both sets of parameters. The therapeutic window between angiographic and ophthalmoscopic threshold revealed a factor of 3.1 for single pulses and 2.3 for repetitive pulse irradiation. The safety range respectively had a factor of 0.8 (single pulses) and 1.7 (10 pulses). Histologic examination of laser lesions with single and repetitive pulses at radiant exposures within the therapeutic window-292 and 213 mJ/cm 2 respectively-revealed damaged RPE, intact Bruch's membrane and choriocapillaries. Photoreceptors were partly spared but also damaged to various extents. Conclusions: Short laser pulses of 8 nanoseconds pulse duration can damage the RPE without retinal hemorrhage or disruption. Selective damage of the RPE without affecting the photoreceptors can only rarely be achieved due to the small safety range. Thus, so far microsecond laser pulses for SRT seems favorable compared to nanosecond pulses in order to prevent unintentional photoreceptor damage.

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Section: Introductionmentioning

confidence: 99%

Investigation of selective retina treatment (SRT) by means of 8 ns laser pulses in a rabbit model

et al. 2008

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“…The results of Brinkmann et al 39 using single porcine melanosomes show that the 'origin of RPE cell damage for single pulse irradiation up to pulse durations of 3 ms can be described by a damage mechanism in which microbubbles around the melanosomes cause a rupture of the cell structure'. 39 In the following years research on the microbubble formation and the damage mechanism itself, 40,41 the detection of the laser-induced microbubbles 42 or damage thresholds caused by microbubble formation 13,40,43 was performed. A retinal in-vitro model was developed and cultured cells were irridiated by Denton et al 44,45 with different wavelength scenarios.…”

Section: History and State Of The Artmentioning

confidence: 99%

Determination of the biological variability of porcine explant tissue in retinal damage ex-vivo experiments with optical laser radiation

Herbst,

Frederiksen,

Stork

2023

Laser Beam Shaping XXIII

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The emission limits and the rulesets in the international laser safety standard IEC 60825-1:2014 are based on scientific evidence from damage threshold experiments and simulations. However, available data sets of laser-induced damage experiments for specific parameter spaces are limited. Therefore, further determination of damage thresholds for laser systems, operating in these parameter spaces, is crucial. Retinal damage thresholds are determined with experiments using animal tissue and optical setups with pulsed lasers and beam profiles of constant irradiance. Several factors influencing these experiments, such as the focusing were identified. This work investigates the biological variability of porcine tissue samples by minimizing the influencing factors and performing damage experiments.

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“…The performance of SRT relies on spatial and temporal confinement which reduces the energy required to achieve the same result without affecting neighbored layers when the laser operates with a pulse length shorter than the thermal relaxation time of the RPE of 10 µs [30]. During this process, the structural integrity of RPE cells is destroyed by fast expanding and collapsing microbubbles which are formed around laser heated intracellular pigments [34][35][36]. Although the precise biological effects, especially caused by sub-lethal cellular irradiation, still need to be evaluated clinically, it is certain that cell-wall rupture leads to cell death.…”

Section: Introductionmentioning

confidence: 99%

Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

Kaufmann¹,

Burri²,

Arnold³

et al. 2018

Biomed. Opt. Express

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Selective treatment of the retinal pigment epithelium (RPE) by using short-pulse lasers leads to a less destructive treatment for certain retinal diseases in contrast to conventional photocoagulation. The introduction of selective retina therapy (SRT) to clinical routine is still precluded by the challenges to reliably monitor treatment success and to automatically adjust dose within the locally varying therapeutic window. Combining micrometer-scale depth resolving capabilities of optical coherence tomography (OCT) with SRT can yield real-time information on the laser-induced changes within the RPE after a laser pulse or even during treatment with a laser pulse train. In the present study, SRT and OCT were combined to treat ex-vivo porcine eyes demonstrating closed-loop dose-control. We found a reliable correlation of specific signal changes in time resolved OCT images and physiological lesions in the RPE. First experiments, including 23 porcine eyes, prove the feasibility of the novel treatment concept.

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Nucleation and dynamics of bubbles forming around laser heated microabsorbers

Cited by 8 publications

References 20 publications

Investigation of selective retina treatment (SRT) by means of 8 ns laser pulses in a rabbit model

Investigation of selective retina treatment (SRT) by means of 8 ns laser pulses in a rabbit model

Determination of the biological variability of porcine explant tissue in retinal damage ex-vivo experiments with optical laser radiation

Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

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