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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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Seifert E, Tode J, Pielen A, Theisen-Kunde D, Framme C, Roider J, Miura Y, Birngruber R, Brinkmann R. Algorithms for optoacoustically controlled selective retina therapy (SRT). PHOTOACOUSTICS 2022; 25:100316. [PMID: 34926158 PMCID: PMC8649889 DOI: 10.1016/j.pacs.2021.100316] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 10/19/2021] [Accepted: 11/09/2021] [Indexed: 06/14/2023]
Abstract
OBJECTIVES Selective Retina Therapy (SRT) uses microbubble formation (MBF) to target retinal pigment epithelium (RPE) cells selectively while sparing the neural retina and the choroid. Intra- and inter-individual variations of RPE pigmentation makes frequent radiant exposure adaption necessary. Since selective RPE cell disintegration is ophthalmoscopically non-visible, MBF detection techniques are useful to control adequate radiant exposures. It was the purpose of this study to evaluate optoacoustically based MBF detection algorithms. METHODS Fifteen patients suffering from central serous chorioretinopathy and diabetic macula edema were treated with a SRT laser using a wavelength of 527 nm, a pulse duration of 1.7 µs and a pulse energy ramp (15 pulses, 100 Hz repetition rate). An ultrasonic transducer for MBF detection was embedded in a contact lens. RPE damage was verified with fluorescence angiography. RESULTS An algorithm to detect MBF as an indicator for RPE cell damage was evaluated. Overall, 4646 irradiations were used for algorithm optimization and testing. The tested algorithms were superior to a baseline model. A sensitivity/specificity pair of 0.96/1 was achieved. The few false algorithmic decisions were caused by unevaluable signals. CONCLUSIONS The algorithm can be used for guidance or automatization of microbubble related treatments like SRT or selective laser trabeculoplasty (SLT).
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Affiliation(s)
- Eric Seifert
- Medizinisches Laserzentrum Lübeck GmbH, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
| | - Jan Tode
- Universitätsklinik für Augenheilkunde, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Amelie Pielen
- Universitätsklinik für Augenheilkunde, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dirk Theisen-Kunde
- Medizinisches Laserzentrum Lübeck GmbH, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
| | - Carsten Framme
- Universitätsklinik für Augenheilkunde, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Johann Roider
- Klinik für Ophthalmologie, Universitätsklinikum Schleswig-Holstein, Arnold-Heller-Straße, 24105 Kiel, Germany
| | - Yoko Miura
- Medizinisches Laserzentrum Lübeck GmbH, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
- Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
| | - Reginald Birngruber
- Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
| | - Ralf Brinkmann
- Medizinisches Laserzentrum Lübeck GmbH, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
- Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany
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Factors Predicting Response to Selective Retina Therapy in Patients with Chronic Central Serous Chorioretinopathy. J Clin Med 2022; 11:jcm11020323. [PMID: 35054017 PMCID: PMC8778271 DOI: 10.3390/jcm11020323] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 12/05/2021] [Accepted: 01/05/2022] [Indexed: 02/06/2023] Open
Abstract
This retrospective study aimed to assess the safety and efficacy of selective retina therapy (SRT) with real-time feedback-controlled dosimetry (RFD) for chronic central serous chorioretinopathy (CSC) and to evaluate factors predictive of treatment response. We included 137 eyes of 135 patients with chronic CSC. SRT was performed to cover each of the leakage areas on fundus fluorescein angiography. Changes in mean best-corrected visual acuity (BCVA), central macular thickness (CMT), and subretinal fluid (SRF) height were evaluated at baseline and at 3 and 6 months after treatment. Complete SRF resolution was observed in 52.6% (72/137 eyes) and 90.5% (124/137 eyes) at 3 and 6 months, respectively. Mean BCVA (logMAR) significantly improved from 0.41 ± 0.31 at baseline to 0.33 ± 0.31 at month 6 (p < 0.001). Mean CMT significantly decreased from 347.67 ± 97.38 μm at baseline to 173.42 ± 30.95 μm at month 6 (p < 0.001). Mean SRF height significantly decreased from 187.85 ± 97.56 µm at baseline to 8.60 ± 31.29 µm after 6 months (p < 0.001). Baseline SRF height was a significant predictive factor for retreatment requirement (p = 0.008). In conclusion, SRT showed favorable anatomical outcomes in patients with chronic CSC. A higher baseline SRF height was a risk factor for retreatment.
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Seifert E, Sonntag SR, Kleingarn P, Theisen-Kunde D, Grisanti S, Birngruber R, Miura Y, Brinkmann R. Investigations on Retinal Pigment Epithelial Damage at Laser Irradiation in the Lower Microsecond Time Regime. Invest Ophthalmol Vis Sci 2021; 62:32. [PMID: 33755044 PMCID: PMC7991964 DOI: 10.1167/iovs.62.3.32] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Purpose New lasers with a continuous wave power exceeding 15 W are currently investigated for retinal therapies, promising highly localized effects at and close to the Retinal Pigment Epithelium (RPE). The goal of this work is to evaluate mechanisms and thresholds for RPE cell damage by means of pulse durations up to 50 µs. Methods A diode laser with a wavelength of 514 nm, a power of 15 W, and adjustable pulse durations between 2 µs and 50 µs was used. Porcine RPE-choroidal explants (ex vivo) and chinchilla bastard rabbits (in vivo) were irradiated to determine threshold radiant exposures for RPE damage H¯Cell by calcein vitality staining and fluorescence angiography, respectively. Thresholds for microbubble formation (MBF) H¯MBF were evaluated by time-resolved optoacoustics. Exemplary histologies support the findings. Results H¯MBF
is significantly higher than H¯Cell at pulse durations ≥ 5 µs (P < 0.05) ex vivo, while at 2 µs, no statistically significant difference was found. The ratios between H¯MBF and H¯Cell increase with pulse duration from 1.07 to 1.48 ex vivo and 1.1 to 1.6 in vivo, for 5.2 and 50 µs. Conclusions Cellular damage with and without MBF related disintegration are both present and very likely to play a role for pulse durations ≥ 5 µs. With the lower µs pulses, selective RPE disruption might be possible, while higher values allow achieving spatially limited thermal effects without MBF. However, both modi require a very accurate real-time dosing control in order to avoid extended retinal disintegration in this power range.
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Affiliation(s)
| | | | | | | | | | - Reginald Birngruber
- Medical Laser Center Lübeck, Lübeck, Germany.,Institute of Biomedical Optics, University of Lübeck, Lübeck, Germany
| | - Yoko Miura
- Department of Ophthalmology, University of Lübeck, Lübeck, Germany.,Institute of Biomedical Optics, University of Lübeck, Lübeck, Germany
| | - Ralf Brinkmann
- Medical Laser Center Lübeck, Lübeck, Germany.,Institute of Biomedical Optics, University of Lübeck, Lübeck, Germany
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Sherpa RD, Hui SP. An insight on established retinal injury mechanisms and prevalent retinal stem cell activation pathways in vertebrate models. Animal Model Exp Med 2021; 4:189-203. [PMID: 34557646 PMCID: PMC8446703 DOI: 10.1002/ame2.12177] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 06/09/2021] [Indexed: 12/22/2022] Open
Abstract
Implementing different tools and injury mechanisms in multiple animal models of retina regeneration, researchers have discovered the existence of retinal stem/progenitor cells. Although they appear to be distributed uniformly across the vertebrate lineage, the reparative potential of the retina is mainly restricted to lower vertebrates. Regenerative repair post-injury requires the creation of a proliferative niche, vital for proper stem cell activation, propagation, and lineage differentiation. This seems to be lacking in mammals. Hence, in this review, we first discuss the many forms of retinal injuries that have been generated using animal models. Next, we discuss how they are utilized to stimulate regeneration and mimic eye disease pathologies. The key to driving stem cell activation in mammals relies on the information we can gather from these models. Lastly, we present a brief update about the genes, growth factors, and signaling pathways that have been brought to light using these models.
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Affiliation(s)
| | - Subhra Prakash Hui
- S. N. Pradhan Centre for NeurosciencesUniversity of CalcuttaKolkataIndia
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Burri C, Al-Nawaiseh S, Wakili P, Salzmann S, Krötz C, Považay B, Meier C, Frenz M, Szurman P, Schulz A, Stanzel B. Selective Large-Area Retinal Pigment Epithelial Removal by Microsecond Laser in Preparation for Cell Therapy. Transl Vis Sci Technol 2021; 10:17. [PMID: 34842907 PMCID: PMC8631056 DOI: 10.1167/tvst.10.10.17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 10/16/2021] [Indexed: 11/25/2022] Open
Abstract
Purpose Cell therapy is a promising treatment for retinal pigment epithelium (RPE)-associated eye diseases such as age-related macular degeneration. Herein, selective microsecond laser irradiation targeting RPE cells was used for minimally invasive, large-area RPE removal in preparation for delivery of retinal cell therapeutics. Methods Ten rabbit eyes were exposed to laser pulses 8, 12, 16, and 20 µs in duration (wavelength, 532 nm; top-hat beam profile, 223 × 223 µm²). Post-irradiation retinal changes were assessed with fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT). RPE viability was evaluated with an angiographic probit model. Following vitrectomy, a subretinal injection of balanced salt solution was performed over a lasered (maximum 13.6 mm2) and untreated control area. Bleb retinal detachment (bRD) morphology was then evaluated by intraoperative OCT. Results Within 1 hour after irradiation, laser lesions showed FA and ICGA leakage. OCT revealed that large-area laser damage was limited to the RPE. The angiographic median effective dose irradiation thresholds (ED50) were 45 µJ (90 mJ/cm2) at 8 µs, 52 µJ (104 mJ/cm2) at 12 µs, 59 µJ (118 mJ/cm2) at 16 µs, and 71 µJ (142 mJ/cm2) at 20 µs. Subretinal injection over the lasered area resulted in a controlled, shallow bRD rise, whereas control blebs were convex in shape, with less predictable spread. Conclusions Large-area, laser-based removal of host RPE without visible photoreceptor damage is possible and facilitates surgical retinal detachment. Translational Relevance Selective microsecond laser-based, large-area RPE removal prior to retinal cell therapy may reduce iatrogenic trauma.
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Affiliation(s)
- Christian Burri
- Institute for Human Centered Engineering (HuCE)–optoLab, Bern University of Applied Sciences, Biel, Switzerland
- Biomedical Photonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - Sami Al-Nawaiseh
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach, Saar, Germany
- Department of Ophthalmology, University of Münster, Münster, Germany
| | - Philip Wakili
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach, Saar, Germany
| | - Simon Salzmann
- Institute for Human Centered Engineering (HuCE)–optoLab, Bern University of Applied Sciences, Biel, Switzerland
| | - Christina Krötz
- Fraunhofer Institute for Biomedical Engineering, Sulzbach, Saar, Germany
| | - Boris Považay
- Institute for Human Centered Engineering (HuCE)–optoLab, Bern University of Applied Sciences, Biel, Switzerland
| | - Christoph Meier
- Institute for Human Centered Engineering (HuCE)–optoLab, Bern University of Applied Sciences, Biel, Switzerland
| | - Martin Frenz
- Biomedical Photonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - Peter Szurman
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach, Saar, Germany
- Klaus Heimann Eye Research Institute, Sulzbach, Saar, Germany
| | - André Schulz
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach, Saar, Germany
- Klaus Heimann Eye Research Institute, Sulzbach, Saar, Germany
| | - Boris Stanzel
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach, Saar, Germany
- Klaus Heimann Eye Research Institute, Sulzbach, Saar, Germany
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7
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Kim U, Kwon M, Jung G, Kim Y, Lee Y, Im S, Cense B, Lee H, Ohm WS, Joo C. Optical dosimeter for selective retinal therapy based on multi-port fiber-optic interferometry. BIOMEDICAL OPTICS EXPRESS 2021; 12:4920-4933. [PMID: 34513233 PMCID: PMC8407823 DOI: 10.1364/boe.434812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 07/07/2021] [Indexed: 06/13/2023]
Abstract
Selective retinal therapy (SRT) employs a micro-second short-pulse lasers to induce localized destruction of the targeted retinal structures with a pulse duration and power aimed at minimal damage to other healthy retinal cells. SRT has demonstrated a great promise in the treatment of retinal diseases, but pulse energy thresholds for effective SRT procedures should be determined precisely and in real time, as the thresholds could vary with disease status and patients. In this study, we present the use of a multi-port fiber-based interferometer (MFI) for highly sensitive real-time SRT monitoring. We exploit distinct phase differences among the fiber ports in the MFI to quantitatively measure localized fluctuations of complex-valued information during the SRT procedure. We evaluate several metrics that can be computed from the full complex-valued information and demonstrate that the complex contour integration is highly sensitive and most correlative to pulse energies, acoustic outputs, and cell deaths. The validity of our method was demonstrated on excised porcine retinas, with a sensitivity and specificity of 0.92 and 0.88, respectively, as compared with the results from a cell viability assay.
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Affiliation(s)
- Uihan Kim
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
- These authors contributed equally to this work
| | - Minsung Kwon
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
- These authors contributed equally to this work
| | - Gyeongyeon Jung
- Department of Research, Lutronic Corporation, 219 Sowon-ro, Goyang, 10534, Republic of Korea
| | - Youngnam Kim
- Department of Research, Lutronic Corporation, 219 Sowon-ro, Goyang, 10534, Republic of Korea
| | - Yunam Lee
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Seonghun Im
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Barry Cense
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
- Optical and Biomedical Engineering Laboratory, Department of Electrical, Electronic & Computer Engineering, The University of Western Australia, Perth, WA 6009, Australia
| | - Hyungsuk Lee
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Won-Suk Ohm
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Chulmin Joo
- Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
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Shimojo Y, Nishimura T, Hazama H, Ito N, Awazu K. Incident Fluence Analysis for 755-nm Picosecond Laser Treatment of Pigmented Skin Lesions Based on Threshold Fluences for Melanosome Disruption. Lasers Surg Med 2021; 53:1096-1104. [PMID: 33604920 PMCID: PMC8519018 DOI: 10.1002/lsm.23391] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/25/2021] [Accepted: 02/01/2021] [Indexed: 11/24/2022]
Abstract
Background and Objectives In this study, the threshold fluences for disrupting the melanosomes for pigmented skin lesion treatment were determined using a 755‐nm picosecond laser for clinical use. Based on the melanosome disruption thresholds, incident fluences corresponding to the target lesion depths were evaluated in silico for different laser spot sizes. Study Design/Materials and Methods Melanosome samples were isolated from porcine eyes as alternative samples for human cutaneous melanosomes. The isolated melanosomes were exposed to 755‐nm picosecond laser pulses to measure the mean particle sizes by dynamic light scattering and confirm their disruption by scanning electron microscopy. The threshold fluences were statistically determined from the relationships between the irradiated fluences and the mean particle sizes. Incident fluences of picosecond laser pulses for the disruption of melanosomes located at different depths in skin tissue were calculated through a light transport simulation using the obtained thresholds. Results The threshold fluences of 550‐ and 750‐picosecond laser pulses were determined to be 2.19 and 2.49 J/cm2, respectively. The numerical simulation indicated that appropriate incident fluences of picosecond laser pulses differ depending on the depth distribution of the melanosomes in the skin tissue, and large spot sizes are desirable for disrupting the melanosomes more deeply located within the skin tissue. Conclusion The threshold fluences of picosecond laser pulses for melanosome disruption were determined. The incident fluence analysis based on the thresholds for melanosome disruption provides valuable information for the selection of irradiation endpoints for picosecond laser treatment of pigmented skin lesions. Lasers Surg. Med. © 2021 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC
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Affiliation(s)
- Yu Shimojo
- Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
| | - Takahiro Nishimura
- Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
| | - Hisanao Hazama
- Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
| | - Nobuhisa Ito
- Global Center for Medical Engineering and Informatics, Osaka University, Yamadaoka 2-2, Suita, Osaka, 565-0871, Japan
| | - Kunio Awazu
- Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan.,Global Center for Medical Engineering and Informatics, Osaka University, Yamadaoka 2-2, Suita, Osaka, 565-0871, Japan.,Graduate School of Frontier Biosciences, Osaka University, Yamadaoka 1-3, Suita, Osaka, 565-0871, Japan
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Brown RB, Dufour S, Deladurantaye P, Bouch NL, Gallant P, Méthot S, Rochette PJ, Mermut O. Effect of laser pulse shaping on photoacoustic dosimetry in retinal models. BIOMEDICAL OPTICS EXPRESS 2020; 11:6590-6604. [PMID: 33282510 PMCID: PMC7687941 DOI: 10.1364/boe.403703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 06/12/2023]
Abstract
Photoacoustic sensing can be a powerful technique to obtain real-time feedback of laser energy dose in treatments of biological tissue. However, when laser therapy uses pulses with microsecond duration, they are not optimal for photoacoustic pressure wave generation. This study examines a programmable fiber laser technique using pulse modulation in order to optimize the photoacoustic feedback signal to noise ratio (SNR) in a context where longer laser pulses are employed, such as in selective retinal therapy. We have demonstrated with a homogeneous tissue phantom that this method can yield a greater than seven-fold improvement in SNR over non-modulated square pulses of the same duration and pulse energy. This technique was further investigated for assessment of treatment outcomes in leporine retinal explants by photoacoustic mapping around the cavitation-induced frequency band.
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Affiliation(s)
- Robert B. Brown
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
- authors contributed equally to this work
| | - Suzie Dufour
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
- authors contributed equally to this work
| | - Pascal Deladurantaye
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
| | - Nolwenn Le Bouch
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
| | - Pascal Gallant
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
| | - Sébastien Méthot
- Laval University, Department of Ophthalmology and ORL, Quebec City, G1 V 0A6, Canada
- Regenerative Medicine Research Center, CHU Quebec, Saint-Sacrement Hospital, Quebec City, G1S 4L8, Canada
| | - Patrick J. Rochette
- Laval University, Department of Ophthalmology and ORL, Quebec City, G1 V 0A6, Canada
- Regenerative Medicine Research Center, CHU Quebec, Saint-Sacrement Hospital, Quebec City, G1S 4L8, Canada
| | - Ozzy Mermut
- National Optics Institute (INO), 2740 Einstein St., Quebec City, G1P 4S4, Canada
- York University, Department of Physics and Astronomy, Toronto, Canada, M3J 1P3, Canada
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10
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Kim M, Park YG, Roh YJ. One-Year Functional and Anatomical Outcomes After Selective Retina Therapy With Real-Time Feedback-Controlled Dosimetry in Patients With Intermediate Age-Related Macular Degeneration: A Pilot Study. Lasers Surg Med 2020; 53:499-513. [PMID: 32757324 DOI: 10.1002/lsm.23305] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 07/20/2020] [Accepted: 07/20/2020] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND OBJECTIVES This pilot study sought to evaluate changes in macular function and drusen volume (DV) after selective retina therapy (SRT) in patients with intermediate age-related macular degeneration (iAMD). STUDY DESIGN/MATERIALS AND METHODS Twenty participants with bilateral iAMD were included in this prospective interventional case series study. After titrating pulse energy by real-time feedback-controlled dosimetry, SRT with a wavelength of 527 nm was applied around the macula of one eye of each patient. Changes in best-corrected visual acuity (BCVA), DV within the central 5-mm ring (C5), and retinal sensitivity (RS) of the SRT-treated eyes (treated eyes) and untreated fellow eyes (untreated eyes) were evaluated at baseline and then at 3, 6, 9, and 12 months after treatment using linear mixed models. RESULTS The mean BCVA did not change significantly between baseline and 12 months in both treated and untreated eyes (P = 0.06, P = 0.24, respectively), whereas the BCVA increase rate was faster for treated than for untreated eyes at the 12-month visit (-0.072 logMAR; 95% confidence interval [CI], -0.085 to -0.059 logMAR; P = 0.006). The mean cube root transformation of DV (cube root DV) within C5 in the untreated eyes increased significantly from 0.278 ± 0.115 at baseline to 0.295 ± 0.132 mm (P = 0.027) at 12 months, whereas the cube root DV change in treated eyes was not significant (P = 0.553). The rate of increase in the cube root DV was lower in treated than in untreated eyes at the 12-month visit (-0.016 mm; 95% CI, -0.018 to -0.011 mm; P = 0.015). The mean RS was increased from 22.49 ± 2.40 dB to 24.09 ± 2.19 dB (P < 0.001) in the treated eyes, whereas the change of mean RS in the untreated eyes was not significant at the 12-month visit (P = 0.18). The treated eyes had a higher rate of increase in RS than untreated eyes at the 12-month visit (1.012 dB; 95% CI, 0.776-1.251 dB; P = 0.037). The RS change was significantly associated with the interaction between SRT treatment and time (P = 0.028), whereas it was not associated with cube root DV change (P = 0.106). No SRT-related adverse effects were observed in all participants during the 1-year follow-up. CONCLUSION Since SRT improved the mean RS and reduced the rate of change in drusen load in the treated eyes, as compared to the untreated eyes, SRT might slow the progression of iAMD. However, further large randomized clinical trials are necessary to confirm the efficacy of SRT for iAMD. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.
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Affiliation(s)
- Minhee Kim
- Department of Ophthalmology and Visual Science, Yeouido St. Mary's Hospital, College of Medicine, Catholic University of Korea, 10, 63-ro, Yeongdeungpo-gu, Seoul, 07345, Republic of Korea
| | - Young Gun Park
- Department of Ophthalmology and Visual Science, Seoul St. Mary's Hospital, College of Medicine, Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul, 06591, Republic of Korea
| | - Young-Jung Roh
- Department of Ophthalmology and Visual Science, Yeouido St. Mary's Hospital, College of Medicine, Catholic University of Korea, 10, 63-ro, Yeongdeungpo-gu, Seoul, 07345, Republic of Korea
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11
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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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12
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Kilin V, Campargue G, Fureraj I, Sakong S, Sabri T, Riporto F, Vieren A, Mugnier Y, Mas C, Staedler D, Collins JM, Bonacina L, Vogel A, Capobianco JA, Wolf JP. Wavelength-Selective Nonlinear Imaging and Photo-Induced Cell Damage by Dielectric Harmonic Nanoparticles. ACS NANO 2020; 14:4087-4095. [PMID: 32282184 DOI: 10.1021/acsnano.9b08813] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We introduce a nonlinear all-optical theranostics protocol based on the excitation wavelength decoupling between imaging and photoinduced damage of human cancer cells labeled by bismuth ferrite (BFO) harmonic nanoparticles (HNPs). To characterize the damage process, we rely on a scheme for in situ temperature monitoring based on upconversion nanoparticles: by spectrally resolving the emission of silica coated NaGdF4:Yb3+/Er3+ nanoparticles in close vicinity of a BFO HNP, we show that the photointeraction upon NIR-I excitation at high irradiance is associated with a temperature increase >100 °C. The observed laser-cell interaction implies a permanent change of the BFO nonlinear optical properties, which can be used as a proxy to read out the outcome of a theranostics procedure combining imaging at 980 nm and selective cell damage at 830 nm. The approach has potential applications to monitor and treat lesions within NIR light penetration depth in tissues.
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Affiliation(s)
- Vasyl Kilin
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | - Gabriel Campargue
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | - Ina Fureraj
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | - Sim Sakong
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | - Tarek Sabri
- Department of Chemistry and Biochemistry and Centre for NanoScience Research, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada
| | | | - Alice Vieren
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | | | - Christophe Mas
- OncoTheis Sàrl, 18 chemin des Aulx, CH-1228, Plan-les-Ouates, Geneva, Switzerland
| | - Davide Staedler
- Department of Pharmacology and Toxicology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - John Michael Collins
- Wheaton College, 26 East Main Street, Norton, Massachusetts 02766, United States
| | - Luigi Bonacina
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
| | - Alfred Vogel
- Institute of Biomedical Optics University of Luebeck, Peter-Monnik-Weg 4, 23562 Luebeck, Germany
| | - John A Capobianco
- Department of Chemistry and Biochemistry and Centre for NanoScience Research, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada
| | - Jean-Pierre Wolf
- Department of Applied Physics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland
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Statement and supplementary statement from the BVA, the DOG, and the RG on laser treatment of drusen in age-related macular degeneration (AMD) : August 2017, update October 2018. Ophthalmologe 2020; 117:1-10. [PMID: 30997527 DOI: 10.1007/s00347-019-0889-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Deladurantaye P, Méthot S, Mermut O, Galarneau P, Rochette PJ. Potential of sub-microsecond laser pulse shaping for controlling microcavitation in selective retinal therapies. BIOMEDICAL OPTICS EXPRESS 2020; 11:109-132. [PMID: 32010504 PMCID: PMC6968749 DOI: 10.1364/boe.11.000109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/08/2019] [Accepted: 11/25/2019] [Indexed: 06/10/2023]
Abstract
Pilot results showing the potential of sub-microsecond laser pulse shaping to optimize thermomechanical confinement in laser-tissue interactions involving microcavitation are presented. Model samples based on aqueous suspensions of retinal melanosomes and eumelanin particles were irradiated at 532 nm with nanosecond laser pulses and picosecond laser pulse trains having differing shapes and durations. The cavitation threshold radiant exposure and the bubble lifetime above the threshold were measured using a pump-probe setup and sub-nanosecond time-resolved imaging. Both quantities were found to strongly depend on the pulse format. These results suggest that sub-microsecond laser pulse shaping could be exploited to optimize precision and control in numerous applications of laser-directed microcavitation, including selective retinal laser treatments.
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Affiliation(s)
- Pascal Deladurantaye
- Axe Médecine Régénératrice, Centre de recherche du CHU de Québec- Université Laval, Hôpital du Saint-Sacrement, Québec, Canada
- Centre de recherche en Organogénèse Expérimentale de l’Université Laval/LOEX, Université Laval, Québec, Canada
- Institut National d’Optique (INO), Québec, Canada
| | - Sébastien Méthot
- Axe Médecine Régénératrice, Centre de recherche du CHU de Québec- Université Laval, Hôpital du Saint-Sacrement, Québec, Canada
- Centre de recherche en Organogénèse Expérimentale de l’Université Laval/LOEX, Université Laval, Québec, Canada
| | - Ozzy Mermut
- Institut National d’Optique (INO), Québec, Canada
- Department of Physics and Astronomy, York University, Ontario, M3J 1P3, Canada
| | | | - Patrick J Rochette
- Axe Médecine Régénératrice, Centre de recherche du CHU de Québec- Université Laval, Hôpital du Saint-Sacrement, Québec, Canada
- Centre de recherche en Organogénèse Expérimentale de l’Université Laval/LOEX, Université Laval, Québec, Canada
- Département d’ophtalmologie, Faculté de Médecine, Université Laval, Québec, Canada
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15
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[Statement from the BVA, the DOG and the RG on laser treatment of drusen in age-related macular degeneration (AMD) : August 2017]. Ophthalmologe 2017; 114:1008-1014. [PMID: 28980062 DOI: 10.1007/s00347-017-0574-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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16
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Framme C, Walter A, Berger L, Prahs P, Alt C, Theisen-Kunde D, Kowal J, Brinkmann R. Selective Retina Therapy in Acute and Chronic-Recurrent Central Serous Chorioretinopathy. Ophthalmologica 2015; 234:177-88. [PMID: 26368551 DOI: 10.1159/000439188] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 07/30/2015] [Indexed: 11/19/2022]
Abstract
PURPOSE Selective retina therapy (SRT), the confined laser heating and destruction of retinal pigment epithelial cells, has been shown to treat acute types of central serous chorioretinopathy (CSC) successfully without damaging the photoreceptors and thus avoiding laser-induced scotoma. However, a benefit of laser treatment for chronic forms of CSC is questionable. In this study, the efficacy of SRT by means of the previously used 1.7-µs and shorter 300-ns pulse duration was evaluated for both types of CSC, also considering re-treatment for nonresponders. MATERIAL AND METHODS In a two-center trial, 26 patients were treated with SRT for acute (n = 10) and chronic-recurrent CSC (n = 16). All patients presented with subretinal fluid (SRF) in OCT and leakage in fluorescein angiography (FA). SRT was performed using a prototype SRT laser system (frequency-doubled Q-switched Nd:YLF-laser, wavelength 527 nm) with adjustable pulse duration. The following irradiation settings were used: a train of 30 laser pulses with a repetition rate of 100 Hz and pulse durations of 300 ns and 1.7 µs, pulse energy 120-200 µJ, retinal spot size 200 µm. Because SRT lesions are invisible, FA was always performed 1 h after treatment to demonstrate laser outcome (5-8 single spots in the area of leakage). In cases where energy was too low, as indicated by missing FA leakage, energy was adjusted and the patient re-treated immediately. Observation intervals were after 4 weeks and 3 months. In case of nonimprovement of the disease after 3 months, re-treatment was considered. RESULTS Of 10 patients with active CSC that presents focal leakage in FA, 5 had completely resolved fluid after 4 weeks and all 10 after 3 months. Mean visual acuity increased from 76.6 ETDRS letters to 85.0 ETDRS letters 3 months after SRT. Chronic-recurrent CSC was characterized by less severe SRF at baseline in OCT and weaker leakage in FA than in acute types. Visual acuity changed from baseline 71.6 to 72.8 ETDRS letters after 3 months. At this time, SRF was absent in 3 out of 16 patients (19%), FA leakage had come to a complete stop in 6 out of 16 patients (38%). In 6 of the remaining chronic CSC patients, repeated SRT with higher pulse energy was considered because of persistent leakage activity. After the re-treatment, SRF resolved completely in 5 patients (83.3%) after only 25 days. CONCLUSION SRT showed promising results in treating acute CSC, but was less effective in chronic cases. Interestingly, re-treatment resulted in enhanced fluid resolution and dry conditions after a considerably shorter time in most patients. Therefore, SRT including re-treatment if necessary might be a valuable CSC treatment alternative even in chronic-recurrent cases.
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Affiliation(s)
- Carsten Framme
- University Eye Hospital, Medical School Hannover, Hannover, Germany
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17
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Lund DJ, Sliney DH. A new understanding of multiple-pulsed laser-induced retinal injury thresholds. HEALTH PHYSICS 2014; 106:505-515. [PMID: 24562071 DOI: 10.1097/hp.0b013e3182a2a837] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Laser safety standards committees have struggled for years to formulate adequately a sound method for treating repetitive-pulse laser exposures. Safety standards for lamps and LEDs have ignored this issue because averaged irradiance appeared to treat the issue adequately for large retinal image sizes and skin exposures. Several authors have recently questioned the current approach of three test conditions (i.e., limiting single-pulse exposure, average irradiance, and a single-pulse-reduction factor) as still insufficient to treat pulses of unequal energies or certain pulse groupings. Schulmeister et al. employed thermal modeling to show that a total-on-time pulse (TOTP) rule was conservative. Lund further developed the approach of probability summation proposed by Menendez et al. to explain pulse-additivity, whereby additivity is the result of an increasing probability of detecting injury with multiple pulse exposures. This latter argument relates the increase in detection probability to the slope of the probit curve for the threshold studies. Since the uncertainty in the threshold for producing an ophthalmoscopically detectable minimal visible lesion (MVL) is large for retinal exposure to a collimated laser beam, safety committees traditionally applied large risk reduction factors ("safety factors") of one order of magnitude when deriving intrabeam, "point-source" exposure limits. This reduction factor took into account the probability of visually detecting the low-contrast lesion among other factors. The reduction factor is smaller for large spot sizes where these difficulties are quite reduced. Thus the N⁻⁰·²⁵ reduction factor may result from the difficulties in detecting the lesion. Recent studies on repetitive pulse exposures in both animal and in vitro (retinal explant) models support this interpretation of the available data.
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Affiliation(s)
- David J Lund
- *Consulting Biophysicist, San Antonio, TX 78248; †Consulting Medical Physicist, Fallston, MD 21047
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18
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Young JK, Figueroa ER, Drezek RA. Tunable Nanostructures as Photothermal Theranostic Agents. Ann Biomed Eng 2011; 40:438-59. [DOI: 10.1007/s10439-011-0472-5] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 11/11/2011] [Indexed: 10/15/2022]
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19
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Tuchin VV, Tárnok A, Zharov VP. In vivo flow cytometry: a horizon of opportunities. Cytometry A 2011; 79:737-45. [PMID: 21915991 PMCID: PMC3663136 DOI: 10.1002/cyto.a.21143] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 08/24/2011] [Indexed: 12/12/2022]
Abstract
Flow cytometry (FCM) has been a fundamental tool of biological discovery for many years. Invasive extraction of cells from a living organism, however, may lead to changes in cell properties and prevents studying cells in their native environment. These problems can be overcome by use of in vivo FCM, which provides detection and imaging of circulating normal and abnormal cells directly in blood or lymph flow. The goal of this review is to provide a brief history, features, and challenges of this new generation of FCM methods and instruments. Spectrum of possibilities of in vivo FCM in biological science (e.g., cell metabolism, immune function, or apoptosis) and medical fields (e.g., cancer, infection, and cardiovascular disorder) including integrated photoacoustic-photothermal theranostics of circulating abnormal cells are discussed with focus on recent advances of this new platform.
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Affiliation(s)
- Valery V. Tuchin
- Research-Educational Institute of Optics and Biophotonics, Saratov State University, Saratov, 410012 Russia
- Institute of Precise Mechanics and Control, Russian Academy of Sciences, Saratov 410028, Russia
- University of Oulu, Oulu, FI-90014 Finland
| | - Attila Tárnok
- Pediatric Cardiology, Heart Center, University of Leipzig, Leipzig, G04289 Germany
| | - Vladimir P. Zharov
- Phillips Classic Laser and Nanomedicine Laboratories, University of Arkansas for Medical Sciences, Little Rock, Arkansas, 72205 USA
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20
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Schulmeister K, Stuck BE, Lund DJ, Sliney DH. Review of thresholds and recommendations for revised exposure limits for laser and optical radiation for thermally induced retinal injury. HEALTH PHYSICS 2011; 100:210-220. [PMID: 21399437 DOI: 10.1097/hp.0b013e3181ea51e3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Exposure limits (ELs) for laser and optical broadband radiation that are derived to protect the retina from adverse thermally-induced effects vary as a function of wavelength, exposure duration, and retinal irradiance diameter (spot size) expressed as the angular subtense α. A review of ex vivo injury threshold data shows that, in the ns regime, the microcavitation-induced damage mechanism results in retinal injury thresholds below thermal denaturation-induced thresholds. This appears to be the reason that the injury thresholds for retinal spot sizes of about 80 μm (α = 6 mrad) and pulse durations of about 5 ns in the green wavelength range are very close to current ELs, calling for a reduction of the EL in the ns regime. The ELs, expressed in terms of retinal radiant exposure or radiance dose, currently exhibit a 1/α dependence up to a retinal spot size of 100 mrad, referred to as αmax. For α ≥ αmax, the EL is a constant retinal radiant exposure (no α dependence) for any given exposure duration. Recent ex vivo, computer model, and non-human primate in vivo threshold data provide a more complete assessment of the retinal irradiance diameter dependence for a wide range of exposure durations. The transition of the 1/α dependence to a constant retinal radiant exposure (or constant radiance dose) is not a constant αmax but varies as a function of the exposure duration. The value of αmax of 100 mrad reflects the spot size dependence of the injury thresholds only for longer duration exposures. The injury threshold data suggest that αmax could increase as a function of the exposure duration, starting in the range of 5 mrad in the μs regime, which would increase the EL for pulsed exposure and extended sources by up to a factor of 20, while still assuring an appropriate reduction factor between the injury threshold and the exposure limit.
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21
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Zharov VP. Ultrasharp nonlinear photothermal and photoacoustic resonances and holes beyond the spectral limit. NATURE PHOTONICS 2011; 5:110-116. [PMID: 25558274 PMCID: PMC4282491 DOI: 10.1038/nphoton.2010.280] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
High-resolution nonlinear laser spectroscopy based on absorption saturation, Lamb-dip and spectral hole-burning phenomena have contributed much to basic and applied photonics. Here, a laser spectroscopy based on nonlinear photothermal and photoacoustic phenomena is presented. It shows ultrasharp resonances and dips up to a few nanometres wide in broad plasmonic spectra of nanoparticles. It also demonstrates narrowing of absorption spectra of dyes and chromophores, as well as an increase in the sensitivity and resolution of the spectral hole-burning technique. This approach can permit the study of laser-nanoparticle interactions at a level of resolution beyond the spectral limits, identification of weakly absorbing spectral holes, spectral optimization of photothermal nanotherapy, measurements of tiny red and blue plasmon resonance shifts, multispectral imaging and multicolour cytometry.
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Affiliation(s)
- Vladimir P Zharov
- Phillips Classic Laser and Nanomedicine Laboratories, University of Arkansas for Medical Sciences, 4301 W. Markham St., Little Rock, Arkansas 72205
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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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23
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Pérez-Gutiérrez FG, Camacho-López S, Evans R, Guillén G, Goldschmidt BS, Viator JA, Aguilar G. Plasma membrane integrity and survival of melanoma cells after nanosecond laser pulses. Ann Biomed Eng 2010; 38:3521-31. [PMID: 20589533 PMCID: PMC2949564 DOI: 10.1007/s10439-010-0101-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 06/11/2010] [Indexed: 12/05/2022]
Abstract
Circulating tumor cells (CTCs) photoacoustic detection systems can aid clinical decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond laser pulses generates photoacoustic waves that make its detection possible. This study aims at: (1) determining melanoma cell survival after laser pulses of 6 ns at λ = 355 and 532 nm; (2) comparing the potential enhancement in the photoacoustic signal using λ = 355 nm in contrast with λ = 532 nm; (3) determining the critical laser fluence at which melanin begins to leak out from melanoma cells; and (4) developing a time-resolved imaging (TRI) system to study the intracellular interactions and their effect on the plasma membrane integrity. Monolayers of melanoma cells were grown on tissue culture-treated clusters and irradiated with up to 1.0 J/cm2. Surviving cells were stained with trypan blue and counted using a hemacytometer. The phosphate buffered saline absorbance was measured with a nanodrop spectrophotometer to detect melanin leakage from the melanoma cells post-laser irradiation. Photoacoustic signal magnitude was studied at both wavelengths using piezoelectric sensors. TRI with 6 ns resolution was used to image plasma membrane damage. Cell survival decreased proportionally with increasing laser fluence for both wavelengths, although the decrease is more pronounced for 355 nm radiation than for 532 nm. It was found that melanin leaks from cells equally for both wavelengths. No significant difference in photoacoustic signal was found between wavelengths. TRI showed clear damage to plasma membrane due to laser-induced bubble formation.
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Affiliation(s)
- Francisco G Pérez-Gutiérrez
- Department of Mechanical Engineering, University of California at Riverside, 900 University Ave., Riverside, CA 92521, USA
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24
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Schulmeister K, Jean M. The risk of retinal injury from Class 2 and visible Class 3R lasers, including medical laser aiming beams. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.mla.2010.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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25
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Rockwell BA, Thomas RJ, Vogel A. Ultrashort laser pulse retinal damage mechanisms and their impact on thresholds. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.mla.2010.02.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Framme C, Brinkmann R. Response to Stanga et al.: Structural Changes of the Retina after Laser Photocoagulation in Spectral Domain Optical Coherence Tomography. Curr Eye Res 2010. [DOI: 10.3109/02713680903486437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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27
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Tanev S, Sun W, Pond J, Tuchin VV, Zharov VP. Flow cytometry with gold nanoparticles and their clusters as scattering contrast agents: FDTD simulation of light-cell interaction. JOURNAL OF BIOPHOTONICS 2009; 2:505-20. [PMID: 19670359 PMCID: PMC2893151 DOI: 10.1002/jbio.200910039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The formulation of the finite-difference time-domain (FDTD) approach is presented in the framework of its potential applications to in-vivo flow cytometry based on light scattering. The consideration is focused on comparison of light scattering by a single biological cell alone in controlled refractive-index matching conditions and by cells labeled by gold nanoparticles. The optical schematics including phase contrast (OPCM) microscopy as a prospective modality for in-vivo flow cytometry is also analyzed. The validation of the FDTD approach for the simulation of flow cytometry may open up a new avenue in the development of advanced cytometric techniques based on scattering effects from nanoscale targets.
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Affiliation(s)
- Stoyan Tanev
- Technology Innovation Management Program in the Department of Systems and Computer Engineering, Faculty of Engineering and Design, Carleton University, Ottawa, ON, Canada.
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Sramek C, Paulus Y, Nomoto H, Huie P, Brown J, Palanker D. Dynamics of retinal photocoagulation and rupture. JOURNAL OF BIOMEDICAL OPTICS 2009; 14:034007. [PMID: 19566300 DOI: 10.1117/1.3130282] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
In laser retinal photocoagulation, short (<20 ms) pulses have been found to reduce thermal damage to the inner retina, decrease treatment time, and minimize pain. However, the safe therapeutic window (defined as the ratio of power for producing a rupture to that of mild coagulation) decreases with shorter exposures. To quantify the extent of retinal heating and maximize the therapeutic window, a computational model of millisecond retinal photocoagulation and rupture was developed. Optical attenuation of 532-nm laser light in ocular tissues was measured, including retinal pigment epithelial (RPE) pigmentation and cell-size variability. Threshold powers for vaporization and RPE damage were measured with pulse durations ranging from 1 to 200 ms. A finite element model of retinal heating inferred that vaporization (rupture) takes place at 180-190 degrees C. RPE damage was accurately described by the Arrhenius model with activation energy of 340 kJ/mol. Computed photocoagulation lesion width increased logarithmically with pulse duration, in agreement with histological findings. The model will allow for the optimization of beam parameters to increase the width of the therapeutic window for short exposures.
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Affiliation(s)
- Christopher Sramek
- Stanford University, Department of Applied Physics, 452 Lomita Mall, Room 140, Stanford, California 94305, USA.
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29
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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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30
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Schulmeister K, Husinsky J, Seiser B, Edthofer F, Fekete B, Farmer L, Lund DJ. Ex vivo and computer model study on retinal thermal laser-induced damage in the visible wavelength range. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:054038. [PMID: 19021418 DOI: 10.1117/1.2982526] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Excised bovine eyes are used as models for threshold determination of 532-nm laser-induced thermal damage of the retina in the pulse duration regime of 100 micros to 2 s for varying laser spot size diameters. The thresholds as determined by fluorescence viability staining compare well with the prediction of an extended Thompson-Gerstman computer model. Both models compare well with published Rhesus monkey threshold data. A previously unknown variation of the spot size dependence is seen for different pulse durations, which allows for a more complete understanding of the retinal thermal damage. Current International Commission on Nonionized Radiation Protection (ICNIRP), American National Standards Institute (ANS), and International Electromechanical Commission (IEC) laser and incoherent optical radiation exposure limits can be increased for extended sources for pulsed exposures. We conclude that the damage mechanism at threshold detected at 24 and 1 h for the nonhuman primate model is retinal pigment epithelium (RPE) cell damage and not thermal coagulation of the sensory retina. This work validates the bovine ex vivo and computer models for prediction of thresholds of thermally induced damage in the time domain of 10 micros to 2 s, which provides the basis for safety analysis of more complicated retinal exposure scenarios such as repetitive pulses, nonconstant retinal irradiance profiles, and scanned exposure.
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Affiliation(s)
- Karl Schulmeister
- Austrian Research Centers GmbH, Laser and Optical Radiation Test House, A-2444 Seibersdorf, Austria.
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