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Camli B, Andrus L, Roy A, Mishra B, Xu C, Georgakoudi I, Tkaczyk T, Ben-Yakar A. Two photon imaging probe with highly efficient autofluorescence collection at high scattering and deep imaging conditions. BIOMEDICAL OPTICS EXPRESS 2024; 15:3163-3182. [PMID: 38855663 PMCID: PMC11161376 DOI: 10.1364/boe.520729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/05/2024] [Accepted: 04/06/2024] [Indexed: 06/11/2024]
Abstract
In this paper, we present a 2-photon imaging probe system featuring a novel fluorescence collection method with improved and reliable efficiency. The system aims to miniaturize the potential of 2-photon imaging in the metabolic and morphological characterization of cervical tissue at sub-micron resolution over large imaging depths into a flexible and clinically viable platform towards the early detection of cancers. Clinical implementation of such a probe system is challenging due to inherently low levels of autofluorescence, particularly when imaging deep in highly scattering tissues. For an efficient collection of fluorescence signals, our probe employs 12 0.5 NA collection fibers arranged around a miniaturized excitation objective. By bending and terminating a multitude of collection fibers at a specific angle, we increase collection area and directivity significantly. Positioning of these fibers allows the collection of fluorescence photons scattered away from their ballistic trajectory multiple times, which offers a system collection efficiency of 4%, which is 55% of what our bench-top microscope with 0.75 NA objective achieves. We demonstrate that the collection efficiency is largely maintained even at high scattering conditions and high imaging depths. Radial symmetry of arrangement maintains uniformity of collection efficiency across the whole FOV. Additionally, our probe can image at different tissue depths via axial actuation by a dc servo motor, allowing depth dependent tissue characterization. We designed our probe to perform imaging at 775 nm, targeting 2-photon autofluorescence from NAD(P)H and FAD molecules, which are often used in metabolic tissue characterization. An air core photonic bandgap fiber delivers laser pulses of 100 fs duration to the sample. A miniaturized objective designed with commercially available lenses of 3 mm diameter focuses the laser beam on tissue, attaining lateral and axial imaging resolutions of 0.66 µm and 4.65 µm, respectively. Characterization results verify that our probe achieves collection efficiency comparable to our optimized bench-top 2-photon imaging microscope, minimally affected by imaging depth and radial positioning. We validate autofluorescence imaging capability with excised porcine vocal fold tissue samples. Images with 120 µm FOV and 0.33 µm pixel sizes collected at 2 fps confirm that the 300 µm imaging depth was achieved.
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Affiliation(s)
- Berk Camli
- Department of Mechanical Engineering, UT Austin, Austin, Texas, USA
| | - Liam Andrus
- Department of Biomedical Engineering, UT Austin, Austin, Texas, USA
| | - Aditya Roy
- Department of Mechanical Engineering, UT Austin, Austin, Texas, USA
| | - Biswajit Mishra
- Department of Mechanical Engineering, UT Austin, Austin, Texas, USA
| | - Chris Xu
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York, USA
| | - Irene Georgakoudi
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - Tomasz Tkaczyk
- Department of Bioengineering, Rice University, Houston, Texas, USA
| | - Adela Ben-Yakar
- Department of Mechanical Engineering, UT Austin, Austin, Texas, USA
- Department of Biomedical Engineering, UT Austin, Austin, Texas, USA
- Department of Electrical and Computer Engineering, UT Austin, Austin, Texas, USA
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Andrus L, Jeon H, Pawlowski M, Debord B, Gerome F, Benabid F, Mau T, Tkaczyk T, Ben-Yakar A. Ultrafast laser surgery probe for sub-surface ablation to enable biomaterial injection in vocal folds. Sci Rep 2022; 12:20554. [PMID: 36446830 PMCID: PMC9708667 DOI: 10.1038/s41598-022-24446-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 11/15/2022] [Indexed: 11/30/2022] Open
Abstract
Creation of sub-epithelial voids within scarred vocal folds via ultrafast laser ablation may help in localization of injectable therapeutic biomaterials towards an improved treatment for vocal fold scarring. Several ultrafast laser surgery probes have been developed for precise ablation of surface tissues; however, these probes lack the tight beam focusing required for sub-surface ablation in highly scattering tissues such as vocal folds. Here, we present a miniaturized ultrafast laser surgery probe designed to perform sub-epithelial ablation in vocal folds. The requirement of high numerical aperture for sub-surface ablation, in addition to the small form factor and side-firing architecture required for clinical use, made for a challenging optical design. An Inhibited Coupling guiding Kagome hollow core photonic crystal fiber delivered micro-Joule level ultrashort pulses from a high repetition rate fiber laser towards a custom-built miniaturized objective, producing a 1/e2 focal beam radius of 1.12 ± 0.10 μm and covering a 46 × 46 μm2 scan area. The probe could deliver up to 3.8 μJ pulses to the tissue surface at 40% transmission efficiency through the entire system, providing significantly higher fluences at the focal plane than were required for sub-epithelial ablation. To assess surgical performance, we performed ablation studies on freshly excised porcine hemi-larynges and found that large area sub-epithelial voids could be created within vocal folds by mechanically translating the probe tip across the tissue surface using external stages. Finally, injection of a model biomaterial into a 1 × 2 mm2 void created 114 ± 30 μm beneath the vocal fold epithelium surface indicated improved localization when compared to direct injection into the tissue without a void, suggesting that our probe may be useful for pre-clinical evaluation of injectable therapeutic biomaterials for vocal fold scarring therapy. With future developments, the surgical system presented here may enable treatment of vocal fold scarring in a clinical setting.
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Affiliation(s)
- Liam Andrus
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Hamin Jeon
- Department of Bioengineering, Rice University, Houston, TX, 77005, USA
| | - Michal Pawlowski
- Department of Bioengineering, Rice University, Houston, TX, 77005, USA
| | - Benoit Debord
- GPPMM Group, XLIM, CNRS-University of Limoges, Limoges, France
| | - Frederic Gerome
- GPPMM Group, XLIM, CNRS-University of Limoges, Limoges, France
| | - Fetah Benabid
- GPPMM Group, XLIM, CNRS-University of Limoges, Limoges, France
| | - Ted Mau
- Department of Otolaryngology-Head and Neck Surgery, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Tomasz Tkaczyk
- Department of Bioengineering, Rice University, Houston, TX, 77005, USA
| | - Adela Ben-Yakar
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA.
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA.
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Gabay I, Subramanian K, Andrus L, DuPlissis A, Yildirim M, Ben-Yakar A. In vivo hamster cheek pouch subepithelial ablation, biomaterial injection, and localization: pilot study. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:080501. [PMID: 36008882 PMCID: PMC9407625 DOI: 10.1117/1.jbo.27.8.080501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
SIGNIFICANCE The creation of subepithelial voids within scarred vocal folds via ultrafast laser ablation may help in localization of injectable biomaterials toward a clinically viable therapy for vocal fold scarring. AIM We aim to prove that subepithelial voids can be created in a live animal model and that the ablation process does not engender additional scar formation. We demonstrate localization and long-term retention of an injectable biomaterial within subepithelial voids. APPROACH A benchtop nonlinear microscope was used to create subepithelial voids within healthy and scarred cheek pouches of four Syrian hamsters. A model biomaterial, polyethylene glycol tagged with rhodamine dye, was then injected into these voids using a custom injection setup. Follow-up imaging studies at 1- and 2-week time points were performed using the same benchtop nonlinear microscope. Subsequent histology assessed void morphology and biomaterial retention. RESULTS Focused ultrashort pulses can be used to create large subepithelial voids in vivo. Our analysis suggests that the ablation process does not introduce any scar formation. Moreover, these studies indicate localization, and, more importantly, long-term retention of the model biomaterial injected into these voids. Both nonlinear microscopy and histological examination indicate the presence of biomaterial-filled voids in healthy and scarred cheek pouches 2 weeks postoperation. CONCLUSIONS We successfully demonstrated subepithelial void formation, biomaterial injection, and biomaterial retention in a live animal model. This pilot study is an important step toward clinical acceptance of a new type of therapy for vocal fold scarring. Future long-term studies on large animals will utilize a miniaturized surgical probe to further assess the clinical viability of such a therapy.
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Affiliation(s)
- Ilan Gabay
- University of Texas at Austin, Department of Mechanical Engineering, Austin, Texas, United States
| | - Kaushik Subramanian
- University of Texas at Austin, Department of Mechanical Engineering, Austin, Texas, United States
| | - Liam Andrus
- University of Texas at Austin, Department of Biomedical Engineering, Austin, Texas, United States
| | - Andrew DuPlissis
- University of Texas at Austin, Department of Biomedical Engineering, Austin, Texas, United States
| | - Murat Yildirim
- University of Texas at Austin, Department of Mechanical Engineering, Austin, Texas, United States
| | - Adela Ben-Yakar
- University of Texas at Austin, Department of Mechanical Engineering, Austin, Texas, United States
- University of Texas at Austin, Department of Biomedical Engineering, Austin, Texas, United States
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Orthopedics-Related Applications of Ultrafast Laser and Its Recent Advances. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12083957] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The potential of ultrafast lasers (pico- to femtosecond) in orthopedics-related procedures has been studied extensively for clinical adoption. As compared to conventional laser systems with continuous wave or longer wave pulse, ultrafast lasers provide advantages such as higher precision and minimal collateral thermal damages. Translation to surgical applications in the clinic has been restrained by limitations of material removal rate and pulse average power, whereas the use in surface texturing of implants has become more refined to greatly improve bioactivation and osteointegration within bone matrices. With recent advances, we review the advantages and limitations of ultrafast lasers, specifically in orthopedic bone ablation as well as bone implant laser texturing, and consider the difficulties encountered within orthopedic surgical applications where ultrafast lasers could provide a benefit. We conclude by proposing our perspectives on applications where ultrafast lasers could be of advantage, specifically due to the non-thermal nature of ablation and control of cutting.
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Katta N, Estrada AD, McErloy AB, Milner TE. Fiber-laser platform for precision brain surgery. BIOMEDICAL OPTICS EXPRESS 2022; 13:1985-1994. [PMID: 35519278 PMCID: PMC9045916 DOI: 10.1364/boe.449312] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 02/20/2022] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
Minimally invasive neurological surgeries are increasingly being sought after for treatment in neurological pathologies and oncology. A critical limitation in these minimally invasive procedures is lack of specialized tools that allow for space-time controlled delivery of sufficient energy for coagulation and cutting of tissue. Advent of fiber-lasers provide high average power with improved beam quality (lower M2), biocompatible silica fiber delivery, reduced cost of manufacturing, and radiant output stability over long operating periods. Despite these advancements, no fiber-laser based surgical tools are currently available for tissue resection in vivo. Here we demonstrate a first to our knowledge, fiber-laser platform for performing precise brain surgery in a murine brain model. In this study, our primary aims were to first demonstrate efficacy of fiber-lasers in performing precise blood-less surgery in a murine brain with limited non-specific thermal damage. Second, fiber-lasers' ability to deliver radiant energy through biocompatible silica fibers was explored in a murine brain model for blood less resection. A bench-top optical coherence tomography (OCT) guided fiber-laser platform was constructed with a stereotactic stage for performing precision brain surgery. A pulsed quasi-continuous wave ytterbium (Yb) fiber-laser (1.07 µm) was used to perform vascular specific coagulation while a pulsed nanosecond thulium fiber-laser (1.94 µm) was used to conduct bloodless cutting, all under the guidance of a swept-source OCT system centered at 1310 +/- 70 nm. Specialty linear and circular cuts were made in an in vivo murine brain for bloodless brain tissue resection. The two fiber-lasers were combined into a single biocompatible silica fiber to conduct brain surgery resection under the bench-top OCT system's imaging microscope. Vascular specific coagulation was demonstrated in all five mice studied. Bloodless linear cuts and point cuts were demonstrated in vivo. Histologically, thermal injury was measured to be less than 100 µm while a removal rate of close to 5 mm3/s was achieved with an average Tm fiber-laser power of 15 W. To the authors' knowledge, this is the first demonstration of a fiber-laser platform for conducting in vivo bloodless brain tissue resection with a pulsed thulium (Tm) fiber-laser and a quasi-continuous wave (QCW) Yb fiber-laser. The demonstrated fiber-laser platform, if successfully configured for use in the operating room (OR), can provide surgeons a tool for rapid removal of tissue while making surgical resections of brain regions more precise, and can be basis for a flexible cutting tool capable of reaching hard-to-operate regions.
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Affiliation(s)
- Nitesh Katta
- Beckman Laser Institute, University of California at Irvine, East Irvine, CA 92617, USA
| | - Arnoldo D. Estrada
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
| | - Austin B. McErloy
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
| | - Thomas E. Milner
- Beckman Laser Institute, University of California at Irvine, East Irvine, CA 92617, USA
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