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Herbst M, Kotzur S, Frederiksen A, Stork W. Nanosecond multipulse retinal damage thresholds of elongated irradiance profiles in explant measurements and simulations. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:125001. [PMID: 38074214 PMCID: PMC10704258 DOI: 10.1117/1.jbo.28.12.125001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023]
Abstract
Significance The database for multipulse retinal damage thresholds for the laser safety standard (IEC 60825-1:2014) is confined, especially for elongated irradiation profiles. To ensure eye safety, retinal damage thresholds (ED 50 values) need to be determined. Aim This study aims to examine nanosecond multipulse scenarios. Approach To determine ED 50 values in ex vivo measurements, an optical laser setup is presented. Porcine explant tissue is irradiated with rectangular top-hat profiles. Thermal simulations are carried out on a validated computer model and retinal injury thresholds are obtained. Results The measurements resulted in ED 50 values from 8.46 to 42.72 μ J with a slope from 1.15 to 1.4. A thermal damage in the measurements can be excluded due to the level value in combination with a different type of declining behavior for increasing pulses compared to the simulations. A dependence with increasing elongation or area of the retinal image emerges in the simulations but could not be confirmed in the measurements due to the influencing factors (biological variability, focusing, and measuring procedure). Conclusions Using slit apertures for beam shaping, variable rectangular spot geometries are realized without changing elements in the setup. For further evaluation of the behavior of elongated irradiation profiles, additional measurements to improve the measurement accuracy are necessary.
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Affiliation(s)
- Marc Herbst
- Cross-Domain Computing Solutions, Robert Bosch GmbH, Schwieberdingen, Germany
- Karlsruhe Institute of Technology, Institute for Information Processing Technologies, Karlsruhe, Germany
| | - Sebastian Kotzur
- Cross-Domain Computing Solutions, Robert Bosch GmbH, Schwieberdingen, Germany
- University of Tübingen, Institute for Ophthalmic Research, Tübingen, Germany
| | - Annette Frederiksen
- Cross-Domain Computing Solutions, Robert Bosch GmbH, Schwieberdingen, Germany
| | - Wilhelm Stork
- Karlsruhe Institute of Technology, Institute for Information Processing Technologies, Karlsruhe, Germany
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Burri C, Salzmann S, Amstutz M, Hoffmann L, Považay B, Meier C, Frenz M. Investigation of the Influence of Pulse Duration and Application Mode on Microsecond Laser Microsurgery of the Retinal Pigment Epithelium. Life (Basel) 2023; 13:1314. [PMID: 37374097 DOI: 10.3390/life13061314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/29/2023] Open
Abstract
Optical microsurgery confined to the retinal pigment epithelium (RPE) requires locally optimized laser parameters and reliable real-time feedback dosimetry (RFD) to prevent unwanted neuroretinal overexposure. This study aimed to compare pulses of different durations and application modes (single, ramp, burst). Moreover, optical coherence tomography (OCT)-based RFD was investigated in an ex vivo experiment, utilizing nine porcine eyes that were exposed to laser pulses of 8, 12, 16 and 20 µs duration (wavelength: 532 nm, exposure area: 90 × 90 µm2, radiant exposure: 247 to 1975 mJ/µm2). Simultaneously, time-resolved OCT M-scans were recorded (central wavelength: 870 nm, scan rate: 85 kHz) for RFD. Post irradiation, retinal changes were assessed with color fundus photography (CFP) and cross-sectional OCT B-scans. RPE cell damage was quantified via fluorescence-based cell viability assay and compared to the OCT dosimetry feedback. Our experiments indicate cumulative RPE damage for pulse bursts of 16 µs and 20 µs, whereas no cumulative effects were found for pulse durations of 8 µs and 12 µs applied in ramp mode. According to statistical analysis, OCT-RFD correctly detected RPE cell damage with 96% sensitivity and 97% specificity using pulses of 8 µs duration in ramp mode.
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Affiliation(s)
- Christian Burri
- Biomedical Photonics Group, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Simon Salzmann
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Mylène Amstutz
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Leonie Hoffmann
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Boris Považay
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Christoph Meier
- Institute for Human Centered Engineering (HuCE)-OptoLab, Bern University of Applied Sciences, Quellgasse 21, 2501 Biel, Switzerland
| | - Martin Frenz
- Biomedical Photonics Group, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
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Wang Z, Feng C, Yang R, Liu T, Chen Y, Chen A, Yan B, Yuan Y, Zhang J. Large-Area Photoreceptor Degeneration Model in Rabbits by Photocoagulation and Oxidative Stress in the Retina. Front Neurosci 2021; 15:617175. [PMID: 34177442 PMCID: PMC8222581 DOI: 10.3389/fnins.2021.617175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 05/06/2021] [Indexed: 11/25/2022] Open
Abstract
Photocoagulation is used for the treatment of retinal ischemic disease. However, due to the invasive nature of photocoagulation and variety of melanin concentrations between individuals, it is challenging to avoid damaging the adjacent photoreceptors and inducing several side effects. Previous studies indicate the role of laser power, duration, and spot size on retinal lesions, but the effect of interspot distance of the laser pulses needs to be considered in panretinal photocoagulation. In this study, we examine different parameters of photocoagulation on lesions of the retina in rabbit, finding that the lesion level of the outer nuclear layer of the retina depended on the pulse duration and laser spot size, and decreasing interspot distance could completely abolish the photoreceptor layer. The degeneration of the photoreceptor by photocoagulation occurred in 24 h and was not restored afterward. We then conducted panretinal photocoagulation in rabbit and found that oxidative stress was decreased in the inner nuclear layer of the retina, and pupillary light reflex and ERG signals were impaired. Our study could provide a rabbit model to explore the mechanism of photoreceptor degeneration and therapies for the side effects after photocoagulation.
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Affiliation(s)
- Zhexuan Wang
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and Ent Hospital of Fudan University, Shanghai, China
| | - Chenli Feng
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and Ent Hospital of Fudan University, Shanghai, China
| | - Ruyi Yang
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and Ent Hospital of Fudan University, Shanghai, China
| | - Tingting Liu
- Department of Ophthalmology, Eye and Ent Hospital of Fudan University, Shanghai, China
| | - Yin Chen
- Key Laboratory of Brain Functional Genomics, Primate Research Center, East China Normal University, Shanghai, China
| | - Aihua Chen
- Key Laboratory of Brain Functional Genomics, Primate Research Center, East China Normal University, Shanghai, China
| | - Biao Yan
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China
| | - Yuanzhi Yuan
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China
| | - Jiayi Zhang
- State Key Laboratory of Medical Neurobiology, Department of Ophthalmology, MOE Frontiers Center for Brain Science, Zhongshan Hospital, Institute for Brain Science, Fudan University, Shanghai, China
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Luecking M, Brinkmann R, Ramos S, Stork W, Heussner N. Capabilities and limitations of a new thermal finite volume model for the evaluation of laser-induced thermo-mechanical retinal damage. Comput Biol Med 2020; 122:103835. [PMID: 32479348 DOI: 10.1016/j.compbiomed.2020.103835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 10/24/2022]
Abstract
Many experimental studies focus on the physical damage mechanisms of short-term exposure to laser radiation. In the nanosecond (ns) pulse range, damage in the Retinal Pigment Epithelium (RPE) will most likely occur at threshold levels due to bubble formation at the surface of the absorbing melanosome. The energy uptake of the melanosomes is one key aspect in modeling the bubble formation and damage thresholds. This work presents a thermal finite volume model for the investigation of rising temperatures and the temperature distribution of irradiated melanosomes. The model takes the different geometries and thermal properties of melanosomes into account, such as the heat capacity and thermal conductivity of the heterogeneous absorbing melanosomes and the surrounding tissue. This is the first time the size and shape variations on the melanosomes' thermal behavior are considered. The calculations illustrate the effect of the geometry on the maximum surface temperature of the irradiated melanosome and the impact on the bubble formation threshold. A comparison between the calculated bubble formation thresholds and the RPE cell damage thresholds within a pulse range of 3 to 5000 ns leads to a mean deviation of μ=22mJ/cm2 with a standard deviation of σ=21mJ/cm2. The best results are achieved between the simulation and RPE cell damage thresholds for pulse durations close to the thermal confinement time of individual melanosomes.
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Affiliation(s)
- Markus Luecking
- FZI Research Center for Information Technology Karlsruhe, Haid-und-Neu-Str. 10, 76131 Karlsruhe, Germany.
| | - Ralf Brinkmann
- Institute of Biomedical Optics, University of Luebeck, Peter-Monnik-Weg 4, 23562 Luebeck, Germany; Medical Laser Center Luebeck, Peter-Monnik-Weg 4, 23562 Luebeck, Germany
| | - Scarlett Ramos
- Robert Bosch GmbH, Herrenwiesenweg 24, 71701 Schwieberdingen, Germany
| | - Wilhelm Stork
- Institute for Information Processing Technologies, Karlsruhe Institute of Technology, Engesserstrasse 5, 76131 Karlsruhe, Germany
| | - Nico Heussner
- Robert Bosch GmbH, Herrenwiesenweg 24, 71701 Schwieberdingen, Germany
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Abstract
Ophthalmology was the first medical specialty to adopt lasers right after their invention more than 50 years ago, and they gradually revolutionized ocular imaging, diagnostics, therapy, and surgery. Challenging precision, safety, and selectivity requirements for ocular therapeutic and surgical procedures keep advancing the laser technologies, which in turn continue enabling novel applications for the preservation and restoration of sight. Modern lasers can provide single-cell-layer selectivity in therapy, submicrometer precision in three-dimensional image-guided surgery, and nondamaging retinal therapy under optoacoustic temperature control. This article reviews the evolution of laser technologies; progress in understanding of the laser-tissue interactions; and concepts, misconceptions, and accidental discoveries that led to modern therapeutic and surgical applications of lasers in ophthalmology. It begins with a brief historical overview, followed by a description of the laser-tissue interactions and corresponding ophthalmic applications.
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Affiliation(s)
- Daniel Palanker
- Department of Ophthalmology and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305;
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A Comparative Study of Retinal Function in Rabbits after Panretinal Selective Retina Therapy versus Conventional Panretinal Photocoagulation. J Ophthalmol 2015; 2015:247259. [PMID: 26525905 PMCID: PMC4615217 DOI: 10.1155/2015/247259] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 09/07/2015] [Accepted: 09/09/2015] [Indexed: 01/21/2023] Open
Abstract
Purpose. This study evaluates functional changes in electroretinographic findings after selective retina therapy (SRT) compared to panretinal photocoagulation (PRP) in rabbits. Methods. The right eyes of 12 Chinchilla rabbits received 200 laser treatment spots. The right eyes of six rabbits received SRT (SRT group), whereas the other six animals were treated using PRP on the right eye (PRP group). The eyes were investigated using full-field ERG 1 hour and 3 weeks after treatment. Histologic exam to assess the tissue response of lasers was performed on 3 weeks. Results. No significant changes in the mean ROD or CR b-wave amplitudes of the SRT lesions were evident, compared to baseline, 1 h after laser treatment (p = 0.372 and 0.278, resp.). In addition, the OPs and 30 Hz flickers of the SRT lesions were not significantly altered (p = 0.17 and 0.243, resp.). At 3 weeks, similar results were found. Comparing the two groups, the ROD b-wave amplitude was reduced in the PRP and SRT groups to 60.04 ± 4.2% and 92.32 ± 6.43% of baseline (p < 0.001). Histologically, there was no visible photoreceptor alterations on week 3. Conclusions. SRT in rabbit eyes induced less functional loss than PRP in both rod-mediated retinal function and cone-mediated retinal function. In addition, SRT irradiated eyes had no functional loss compared to its control.
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Kim DH. Using a melanin granule lattice model to study the thermal effects of pulsed and scanning light irradiations through a measurement aperture. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:125002. [PMID: 22191915 DOI: 10.1117/1.3656746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Optical radiation hazards of scanning light sources are often evaluated using pulsed light source criteria, with the relevant pulse parameter equivalent to the scanning light source determined by the energy delivered through a measurement aperture. However, physical equivalence has not been completely understood: a pulsed light source is temporally dynamic but spatially stationary, while a scanning light source is temporally stationary but spatially dynamic. This study introduces a numerical analysis based upon the melanin granule lattice model to investigate the equivalence of scanning and pulsed light sources through a measurement aperture and their respective thermal effects in the pigmented retinal layer. The numerical analysis calculates the thermal contribution of individual melanin granules with varying temporal sequence, and finds that temperature changes and thermal damage thresholds for the two different types of light sources were not equal. However, dwell times of 40 to 200 μsec did not produce significant differences between pulsed and scanning light sources in temperature change and thermal damage thresholds to the sample tissue.
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Affiliation(s)
- Do-Hyun Kim
- U.S. Food and Drug Administration, Center for Devices and Radiological Health, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993, USA.
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SELECTIVE RETINAL THERAPY WITH MICROSECOND EXPOSURES USING A CONTINUOUS LINE SCANNING LASER. Retina 2011; 31:380-8. [DOI: 10.1097/iae.0b013e3181e76da6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kriechbaum K, Bolz M, Deak GG, Prager S, Scholda C, Schmidt-Erfurth U. High-resolution imaging of the human retina in vivo after scatter photocoagulation treatment using a semiautomated laser system. Ophthalmology 2010; 117:545-51. [PMID: 20031226 DOI: 10.1016/j.ophtha.2009.07.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Revised: 07/12/2009] [Accepted: 07/23/2009] [Indexed: 12/21/2022] Open
Abstract
PURPOSE To image the ultrastructural morphology of retinal laser effects and their healing response in vivo using spectral domain optical coherence tomography (SD-OCT). DESIGN Prospective, interventional study. PARTICIPANTS Ten patients undergoing panretinal photocoagulation for proliferative diabetic retinopathy. METHODS Panretinal photocoagulation (PRP) was performed using a semiautomated patterned scanning laser system providing a raster of effects with homogenous intensity. Retinal morphology and localization of effects owing to laser-tissue interaction were imaged at 1 day, 1 week, and at monthly intervals for 6 months. The characteristic, specific structural changes during the healing process were followed over time using an SD-OCT device (Spectralis OCT) allowing for high-resolution raster scanning of the entire lesion pattern with identification of identical retinal sites (tracking modality). MAIN OUTCOME MEASURES Retinal morphology and localization of effects of photocoagulation on SD-OCT images. RESULTS At day 1 after PRP, the photocoagulation effects were sharply delineated from the surrounding unaffected retina and all spots seemed to be identical in size and location. The area of tissue destruction was confined to the outer retinal layers, extending from the outer nuclear layer (ONL) to the retinal pigment epithelium (RPE). At 1 week, images showed a progressive loss of the affected outer retinal layers, namely, the ONL and the outer plexiform layer. Concomitant distortion of the inner nuclear and plexiform layers generated a pattern of "archways" between adjacent laser spots. The photoreceptor layers (PRL) seemed to be eliminated in the photocoagulated area, particularly at the borders of each lesion. The lesion center contained a condensed RPE and PRL segment. The ONL recovered partially, but the PRL inner and outer segments remained absent. During the long-term follow-up, RPE cells migrated to the center of the lesion, forming a hyperplastic scar. CONCLUSIONS The characteristic morphology of retinal photocoagulation effects in vivo and over time was identified for the first time in human eyes using SD-OCT. The OCT imaging demonstrated a well-defined reproducible area of destruction confined to the outer retinal layers. Healing proceeded as the condensation of the RPE and PRL in the lesion center.
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Affiliation(s)
- Katharina Kriechbaum
- Department of Ophthalmology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
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Lee P, Kim YG, Yu SY, Kwak HW. A Case of Ciliochoroidal Detachment After Patterned Scanning Laser Photocoagulation With Short Exposure Time. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2010. [DOI: 10.3341/jkos.2010.51.6.908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Pyung Lee
- Department of Ophthalmology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Young Gyun Kim
- Department of Ophthalmology, Eulji University School of Medicine, Seoul, Korea
| | - Seung Young Yu
- Department of Ophthalmology, Kyung Hee University School of Medicine, Seoul, Korea
| | - Hyung Woo Kwak
- Department of Ophthalmology, Kyung Hee University School of Medicine, Seoul, Korea
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Framme C, Walter A, Prahs P, Theisen-Kunde D, Brinkmann R. Comparison of threshold irradiances and online dosimetry for selective retina treatment (SRT) in patients treated with 200 nanoseconds and 1.7 microseconds laser pulses. Lasers Surg Med 2008; 40:616-24. [DOI: 10.1002/lsm.20685] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Lee H, Alt C, Pitsillides CM, Lin CP. Optical detection of intracellular cavitation during selective laser targeting of the retinal pigment epithelium: dependence of cell death mechanism on pulse duration. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:064034. [PMID: 18163850 DOI: 10.1117/1.2804078] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Selective laser targeting of the retinal pigment epithelium (RPE) is an attractive method for treating RPE-associated disorders. We are developing a method for optically detecting intracellular microcavitation that can potentially serve as an immediate feedback of the treatment outcome. Thermal denaturation or intracellular cavitation can kill RPE cells during selective targeting. We examined the cell damage mechanism for laser pulse durations from 1 to 40 micros ex vivo. Intracellular cavitation was detected as a transient increase in the backscattered treatment beam. Cavitation and cell death were correlated for individual cells after single-pulse irradiation. The threshold radiant exposures for cell death (ED(50,d)) and cavitation (ED(50,c)) increased with pulse duration and were approximately equal for pulses of up to 10 micros. For 20 micros, the ED(50,d) was about 10% lower than the ED(50,c); the difference increased with 40-micros pulses. Cells were killed predominantly by cavitation (up to 10-micros pulses); probability of thermally induced cell death without cavitation gradually increases with pulse duration. Threshold measurements are discussed by modeling the temperature distribution around laser-heated melanosomes and the scattering function from the resulting cavitation. Detection of intracellular cavitation is a highly sensitive method that can potentially provide real-time assessment of RPE damage during selective laser targeting.
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Affiliation(s)
- Ho Lee
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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