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Barauah V, Parsa S, Chowdhury N, Milner T, Rylander HG. Scattering angle resolved optical coherence tomography measures morphological changes in Bacillus subtilis colonies. J Biomed Opt 2022; 27:126004. [PMID: 36590979 PMCID: PMC9800589 DOI: 10.1117/1.jbo.27.12.126004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
SIGNIFICANCE An unmet need is recognized for early detection and diagnosis of neurological diseases. Many psychological markers emerge years after disease onset. Mitochondrial dysfunction and corresponding neurodegeneration occur before onset of large-scale cell and tissue pathology. Early detection of subcellular morphology changes could serve as a beacon for early detection of neurological diseases. This study is on bacterial colonies, Bacillus subtilis, which are similar in size to mitochondria. AIM This study investigates whether morphological changes can be detected in Bacillus subtilis using scattering angle resolved optical coherence tomography (SAR-OCT). APPROACH The SAR-OCT was applied to detect scattering angle distribution changes in Bacillus subtilis. The rod-to-coccus shape transition of the bacteria was imaged, and the backscattering angle was analyzed by recording the distribution of the ratio of low- to medium angle scattering (L/M ratio). Bacillus orientation at different locations in colonies was analytically modeled and compared with SAR-OCT results. RESULTS Significant differences in the distribution of backscattering angle were observed in Bacillus subtilis transitioning from rod-to-coccus shapes. In Bacillus subtilis, the C -parameter of the Burr distribution of the SAR-OCT-derived L/M ratio was significantly smaller in coccus compared with rod-shaped bacteria. SAR-OCT-derived L/M ratio varied with bacterial position in the colony and is consistent with predicted orientations from previous studies. CONCLUSIONS Study results support the potential of utilizing SAR-OCT to detect bacterial morphological changes.
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Affiliation(s)
- Vikram Barauah
- The University of Texas at Austin, Biomedical Optics Lab, Department of Biomedical Imaging, Austin, Texas, United States
| | - Shyon Parsa
- UT Southwestern Medical School, Dallas, Texas, United States
| | - Naail Chowdhury
- The University of Texas at Austin, Biomedical Optics Lab, Department of Biomedical Imaging, Austin, Texas, United States
| | - Thomas Milner
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Henry Grady Rylander
- The University of Texas at Austin, Biomedical Optics Lab, Department of Biomedical Imaging, Austin, Texas, United States
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2
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Liu S, Datta A, Ho D, Dwelle J, Wang D, Milner TE, Rylander HG, Markey MK. Effect of image registration on longitudinal analysis of retinal nerve fiber layer thickness of non-human primates using Optical Coherence Tomography (OCT). Eye Vis (Lond) 2015; 2:3. [PMID: 26605359 PMCID: PMC4657366 DOI: 10.1186/s40662-015-0013-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 01/27/2015] [Indexed: 11/18/2022]
Abstract
BACKGROUND In this paper we determined the benefits of image registration on estimating longitudinal retinal nerve fiber layer thickness (RNFLT) changes. METHODS RNFLT maps around the optic nerve head (ONH) of healthy primate eyes were measured using Optical Coherence Tomography (OCT) weekly for 30 weeks. One automatic algorithm based on mutual information (MI) and the other semi-automatic algorithm based on log-polar transform cross-correlation using manually segmented blood vessels (LPCC_MSBV), were used to register retinal maps longitudinally. We compared the precision and recall between manually segmented image pairs for the two algorithms using a linear mixed effects model. RESULTS We found that the precision calculated between manually segmented image pairs following registration by LPCC_MSBV algorithm is significantly better than the one following registration by MI algorithm (p < <0.0001). Trend of the all-rings and temporal, superior, nasal and inferior (TSNI) quadrants average of RNFLT over time in healthy primate eyes are not affected by registration. RNFLT of clock hours 1, 2, and 10 showed significant change over 30 weeks (p = 0.0058, 0.0054, and 0.0298 for clock hours 1, 2 and 10 respectively) without registration, but stayed constant over time with registration. CONCLUSIONS The LPCC_MSBV provides better registration of RNFLT maps recorded on different dates than the automatic MI algorithm. Registration of RNFLT maps can improve clinical analysis of glaucoma progression.
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Affiliation(s)
- Shuang Liu
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
- />Present address: Clinical Neuroscience Imaging Center (CNIC), Department of Neurology, Yale School of Medicine, New Haven, CT 06510 USA
| | - Anjali Datta
- />Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Derek Ho
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Jordan Dwelle
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Daifeng Wang
- />Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Thomas E Milner
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Henry Grady Rylander
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
| | - Mia K Markey
- />Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712 USA
- />Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 USA
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3
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Zaman RT, Diagaradjane P, Wang JC, Schwartz J, Rajaram N, Gill-Sharp KL, Cho SH, Rylander HG, Payne JD, Krishnan S, Tunnell JW. In Vivo Detection of Gold Nanoshells in Tumors Using Diffuse Optical Spectroscopy. IEEE J Sel Top Quantum Electron 2007; 13:1715-1720. [PMID: 33859459 PMCID: PMC8045142 DOI: 10.1109/jstqe.2007.910804] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
This study demonstrates the use of diffuse optical spectroscopy (DOS) for the noninvasive measurement of gold nanoshell concentrations in tumors of live mice. We measured the diffuse optical spectra (500-800 nm) using an optical fiber probe placed in contact with the tissue surface. We performed in vitro studies on tissue phantoms illustrating an accurate measurement of gold-silica nanoshell concentration within 12.6% of the known concentration. In vivo studies were performed on a mouse xenograft tumor model. DOS spectra were measured at preinjection, immediately postinjection, 1 and 24 h postinjection times, and the nanoshell concentrations were verified using neutron activation analysis.
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Affiliation(s)
- Raiyan T Zaman
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712 USA
| | | | - James C Wang
- Nanospectra Biosciences, Inc., Houston, TX 77054 USA
| | - Jon Schwartz
- Nanospectra Biosciences, Inc., Houston, TX 77054 USA
| | - Narasimhan Rajaram
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712 USA
| | | | - Sang H Cho
- MD Anderson Cancer Center, University of Texas, Houston, TX 77030 USA. He is now with the Department of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA
| | - Henry Grady Rylander
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712 USA
| | | | - Sunil Krishnan
- Radiation Oncology, MD Anderson Cancer Center, Houston, TX 77030-4090 USA
| | - James W Tunnell
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712 USA
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4
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Hammer DX, Davé D, Milner TE, Choi B, Rylander HG, Welch AJ. Investigation of the transduction mechanism of infrared detection in Melanophila acuminata: photo-thermal-mechanical hypothesis. Comp Biochem Physiol A Mol Integr Physiol 2002; 132:381-92. [PMID: 12020654 DOI: 10.1016/s1095-6433(02)00036-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Differential phase optical low coherence reflectometry (OLCR) was used to detect sub-wavelength displacements in the infrared-sensitive thoracic pit organ of Melanophila acuminata (Coleoptera: Buprestidae) upon absorption of infrared radiation at 3.39 microm. The displacement had more complex morphology but similar amplitude ( approximately 100 nm at 1 W cm(-2)) when compared to the displacement measured from the exocuticle in an alternate region on the beetle's body. In addition, a simplified finite difference model was developed to predict the temperature distribution and resultant thermal expansion in the pit organ tissue. The experimental and model results were interpreted to help clarify the mechanism by which the sensilla in the pit organ convert infrared radiation to neural signals. The results of this paper are discussed in relation to the photo-thermal-mechanical transduction hypothesis. This is the first experimental examination of the transduction mechanism in Melanophila acuminata.
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Affiliation(s)
- D X Hammer
- Department of Electrical Engineering, University of Texas, Austin, TX 78712, USA.
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5
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Ducros MG, Marsack JD, Rylander HG, Thomsen SL, Milner TE. Primate retina imaging with polarization-sensitive optical coherence tomography. J Opt Soc Am A Opt Image Sci Vis 2001; 18:2945-56. [PMID: 11760194 DOI: 10.1364/josaa.18.002945] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polarization-sensitive optical coherence tomography (PSOCT) is applied to determine the depth-resolved polarization state of light backreflected from the eye. The birefringence of the retinal nerve fiber layer (RNFL) was observed and measured from PSOCT images recorded postmortem in a Rhesus monkey. An image-processing algorithm was developed to identify birefringent regions in acquired PSOCT retinal images and automatically determine the thickness of the RNFL. Values of the RNFL thickness determined from histology and PSOCT were compared. PSOCT may provide a new method to determine RNFL thickness and birefringence for glaucoma diagnostics.
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Affiliation(s)
- M G Ducros
- Biomedical Engineering Laser Laboratory, The University of Texas at Austin, Austin, Texas 78712, USA
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6
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Metha AB, Crane AM, Rylander HG, Thomsen SL, Albrecht DG. Maintaining the cornea and the general physiological environment in visual neurophysiology experiments. J Neurosci Methods 2001; 109:153-66. [PMID: 11513950 DOI: 10.1016/s0165-0270(01)00409-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neurophysiologists have been investigating the responses of neurons in the visual system for the past half-century using monkeys and cats that are anesthetized and paralyzed, with the non-blinking eyelids open for prolonged periods of time. Impermeable plastic contact lenses have been used to prevent dehydration of the corneal epithelium, which would otherwise occur in minutes. Unfortunately, such lenses rapidly introduce a variety of abnormal states that lead to clouding of the cornea, degradation of the retinal image, and premature termination of the experiment. To extend the viability of such preparations, a new protocol for maintenance of corneal health has been developed. The protocol uses rigid gas permeable contact lenses designed to maximize gas transmission, rigorous sterile methods, and a variety of methods for sustaining and monitoring the overall physiology of the animal. The effectiveness of the protocol was evaluated clinically by ophthalmoscopy before, during, and after the experiments, which lasted 8-10 days. Histopathology and quantitative histology were performed on the corneas following the experiment. Our observations showed that this protocol permits continuous contact lens wear without adversely affecting the corneas. Thus, it is possible to collect data 24 h each day, for the entire duration of the experiment.
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Affiliation(s)
- A B Metha
- Department of Optometry and Vision Sciences, The University of Melbourne, Victoria 3053, Carlton, Australia
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7
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Barrett SF, Wright CH, Oberg ED, Rockwell BA, Cain C, Rylander HG, Welch AJ. Digital integrated retinal surgical laser system. Biomed Sci Instrum 2001; 33:354-9. [PMID: 9731385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The year is 2001--ophthalmic retinal surgery is now fully computer assisted. Patients arriving for scheduled treatments of diabetic retinopathy, retinal tears, or macular degeneration have their retina digitally mapped by a technician. From the retinal map, the ophthalmologist plots therapeutic lesion sites with a light pen on the computer screen that will automatically be placed by a computer controlled argon laser. The treatment only requires 100 ms per lesion placement thus reducing office calls to approximately 45 minutes freeing the ophthalmologist for other pressing cases. This paper reports on the development of a clinically significant prototype system that will help bring this scenario to fruition.
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Affiliation(s)
- S F Barrett
- Department of Electrical Engineering, USAF Academy, CO 80840, USA
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8
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Wright CH, Ferguson RD, Barrett SF, Rylander HG, Welch AJ, Oberg ED. Hybrid retinal photocoagulation system using analog tracking. Biomed Sci Instrum 2001; 33:366-71. [PMID: 9731387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We describe initial in vivo experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control. An overview of the design is given. The results show in vivo tracking rates which exceed the equivalent of 38 degrees per second in the eye, with automated lesion pattern creation. Robotically-assisted laser surgery to treat conditions such as diabetic retinopathy and retinal breaks may soon be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components based on this design.
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Affiliation(s)
- C H Wright
- Department of Electrical Engineering, U.S. Air Force Academy, CO 80840, USA
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9
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Abstract
BACKGROUND AND OBJECTIVE A method to increase light transport deeply into target areas of tissue would enhance both therapeutic and diagnostic laser applications. The effects of a hyperosmotic agent on the scattering properties of rat and hamster skin were investigated. STUDY DESIGN/MATERIALS AND METHODS A hyperosmotic agent, glycerol, was applied in vitro and in vivo to rat and hamster skin to assess the changes in tissue optical properties. Changes in the reduced scattering coefficient after application of the agent in vitro to rat skin and after the skin has been rehydrated were assessed to evaluate the effect of the agent on tissue. RESULTS Experimental results showed a transient change in the optical properties of in vitro rat skin. A 50% increase in transmittance and decrease in diffuse reflectance occurred within 5-10 min after the introduction of anhydrous glycerol. In addition, reduction of light scattering with this technique increased depth of visibility with optical coherence tomography. Injection of glycerol under the skin allowed in vivo visualization of blood vessels. CONCLUSIONS The application of the agent reduces the amount of refractive mismatch found in the tissue and markedly reduces random scattering, thereby making the skin less turbid for visible wavelengths for a controlled period of time.
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Affiliation(s)
- G Vargas
- Biomedical Engineering Program, The University of Texas at Austin, 78712, USA.
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10
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Wright CH, Barrett SF, Ferguson RD, Rylander HG, Welch AJ. Initial in vivo results of a hybrid retinal photocoagulation system. J Biomed Opt 2000; 5:56-61. [PMID: 10938767 DOI: 10.1117/1.429969] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/1998] [Revised: 07/27/1999] [Accepted: 08/27/1999] [Indexed: 05/23/2023]
Abstract
We describe initial in vivo experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control. An overview of the design is given. The results show in vivo tracking rates which exceed the equivalent of 38 degrees/s in the eye. A robotically assisted lesion pattern is created for laser surgery to treat conditions such as diabetic retinopathy and retinal breaks.
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Affiliation(s)
- C H Wright
- US Air Force Academy, Colorado 80840-6236, USA.
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11
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Nemati B, Dunn A, Welch AJ, Rylander HG. Optical model for light distribution during transscleral cyclophotocoagulation. Appl Opt 1998; 37:764-71. [PMID: 18268651 DOI: 10.1364/ao.37.000764] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Transscleral cyclophotocoagulation (TSCPC) is currently performed clinically as an effective treatment for end-stage glaucoma. We develop a theoretical model for the analysis of optical attenuation phenomena during TSCPC as a basis for selection of an optimal wavelength. A multilayered Monte Carlo model was developed to calculate the fluence and the rate of heat generation in each tissue layer for the wavelengths of Nd:YAG, diode, ruby, krypton yellow, and argon lasers. Of the five wavelengths under study, our theoretical results suggest that the diode laser wavelength offers the best penetration through the conjunctiva, sclera, and ciliary muscle and highest absorption within the ciliary pigment epithelium.
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12
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Nemati B, Rylander HG, Welch A. Optical properties of conjunctiva, sclera, and the ciliary body and their consequences for transscleral cyclophotocoagulation: erratum. Appl Opt 1997; 36:416. [PMID: 18250689 DOI: 10.1364/ao.36.000416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Corrections are given to the reported [Appl. Opt. 35, 3321 (1996)] units of the absorption and scattering coefficients mu (a) and mu (s), respectively. The corrections pertain to two figures, several tables, and the text describing results.
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13
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Barrett SF, Wright CH, Oberg ED, Rockwell BA, Cain C, Rylander HG, Welch AJ. Development of an integrated automated retinal surgical laser system. Biomed Sci Instrum 1996; 32:215-224. [PMID: 8672671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Researchers at the University of Texas and the USAF Academy have worked toward the development of a retinal robotic laser system. The overall goal of this ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Preliminary testing on rhesus primate subjects have been accomplished with the CW argon laser and also the ultrashort pulse laser. Recent efforts have concentrated on combining the two subsystems into a single prototype capable of simultaneously controlling both lesion depth and placement. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. Several interesting areas of study have developed in integrating the two subsystems: 1) "doughnut" shaped lesions that occur under certain combinations of laser power, spot size, and irradiation time complicating measurements of central lesion reflectance, 2) the optimal retinal field of view (FOV) to achieve both tracking and lesion parameter control, and 3) development of a hybrid analog/digital tracker using confocal reflectometry to achieve retinal tracking speeds of up to 100 dgs. This presentation will discuss these design issues of this clinically significant prototype system. Details of the hybrid prototype system are provided in "Hybrid Eye Tracking for Computer-Aided Retinal Surgery" at this conference. The paper will close with remaining technical hurdles to clear prior to testing the full-up clinical prototype system.
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Affiliation(s)
- S F Barrett
- Department of Electrical Engineering, USAF Academy, CO 80840, USA
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14
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Abstract
In this study, the effectiveness of pulsed and continuous wave (CW) holmium: YAG lasers in coagulating in vitro pig corneas was analyzed. With the CW laser, irradiance and exposure time were varied; irradiance, from 162 to 324 W/cm2 and exposure time, from 200 to 800 ms. With the pulsed laser, number of pulses and radiant exposure were varied; number of pulses per lesion, from 4 to 30 and radiant exposure, from 10 to 25 J/cm2. Laser-induced corneal damage was determined by analyzing histological cross sections of each lesion. Depth and diameter of the lesions were plotted against the varying laser parameters. Light and birefringent photomicrographs of typical lesion histology show that the pulsed laser significantly damaged superficial layers of the cornea and could not achieve the coagulation depths produced by the CW laser. Additional histology demonstrates that minimal surface damage (intrastromal coagulation) occurred when the CW laser beam was delivered with a sapphire-tipped contact probe. The results provide empirical data on the sensitivity of each parameter in producing a range of coagulation end points. In addition, the experimental results describe trends between the parameters of either laser and the extent of coagulation.
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Affiliation(s)
- C Smithpeter
- Biomedical engineering program, University of Texas at Austin 78712, USA
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15
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Barrett SF, Wright CH, Jerath MR, Lewis RS, Dillard BC, Rylander HG, Welch AJ. Automated retinal robotic laser system. Biomed Sci Instrum 1995; 31:89-93. [PMID: 7654990 DOI: 10.1117/12.208403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Researchers at the University of Texas and the USAF Academy have worked toward the development of a retinal robotic laser system. The overall goal of this ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Recent efforts have concentrated on combining the two subsystems into a single prototype capable of simultaneously controlling both lesion depth and placement. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies.
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Affiliation(s)
- S F Barrett
- Department of Electrical Engineering, USAF Academy, CO 80840, USA
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16
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Abstract
BACKGROUND AND OBJECTIVE The objective of this research was to build a prototype feedback control system to precisely place argon laser lesions on the retina for treatment of retinal disorders. STUDY DESIGN/MATERIALS, AND METHODS: The prototype feedback control system was tested by placing lesions at specific locations on the retina of pigmented rabbits to simulate the treatment of diabetic retinopathy, retinal breaks or tears, and a pre-programmed, two-dimensional array of lesions was placed at a specific site. RESULTS Results of feedback-controlled lesion placement performed in vivo on pigmented rabbits are presented. The ability to place lesions with automated feedback control is demonstrated. CONCLUSION Automated feedback control placement of argon laser lesions is possible at a reasonable cost and has numerous therapeutic and safety benefits over current ballistic delivery.
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Affiliation(s)
- S F Barrett
- Biomedical Engineering Program, University of Texas, Austin 78712, USA
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17
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Jerath MR, Chundru R, Barrett SF, Rylander HG, Welch AJ. Preliminary results on reflectance feedback control of photocoagulation in vivo. IEEE Trans Biomed Eng 1994; 41:201-3. [PMID: 8026855 DOI: 10.1109/10.284934] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The size of therapeutic laser-induced retinal lesions is critical for effective treatment and minimal complications. Due to tissue variability, the size of a lesion that results from a given set of laser irradiation parameters cannot be predicted. Real time feedback control of lesion size is implemented based on two-dimensional reflectance images acquired during irradiation. Preliminary results of feedback controlled lesions formed in pigmented rabbits demonstrate an ability to produce uniform lesions despite variations in tissue absorption or changes in laser power.
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Affiliation(s)
- M R Jerath
- Biomedical Engineering Program, University of Texas at Austin 78712
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18
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Abstract
Conventional retinal laser photocoagulation is presently performed by an ophthalmologist manually aiming a low-power laser beam at a desired site and firing a high-power laser for a preselected interval of time. To automate this process a retinal tracker must acquire a target, track small saccades, and identify loss of track during a large saccade. The authors successfully implemented a real-time algorithm that used a simple computer, video digitizing card, low light video camera, and fundus camera to perform rudimentary tracking on a photograph of a retina undergoing smooth circular motion. The algorithm tracked speeds up to 5 Hz, or 27 degrees/s, which equated to the retina moving in a 525 microns diameter circle.
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Affiliation(s)
- M S Markov
- Department of Electrical Engineering, United States Air Force Academy, CO
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19
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Abstract
OBJECTIVE The objective of this research was to build a real-time feedback system that controlled lesion size. Two-dimensional reflectance images were acquired with a charge-coupled device camera during irradiation, and argon laser exposure was ended when parameters of the image reached prespecified values. METHODS The real-time feedback control system was tested by creating lesions at different power levels in pigmented rabbits. Laser exposure time was controlled by monitoring the central reflectance. RESULTS Results of feedback-controlled lesions formed in vivo in pigmented rabbits are presented. An ability to produce uniform lesions despite variation in tissue absorption or changes in laser power is demonstrated. CONCLUSIONS Reflectance control of photocoagulation is possible; incorporation of feedback during photocoagulation has numerous therapeutic and safety benefits over current ballistic delivery.
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Affiliation(s)
- M R Jerath
- Biomedical Engineering Program, University of Texas, Austin 78712
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20
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Jerath MR, Gardner CM, Rylander HG, Welch AJ. Dynamic optical property changes: implications for reflectance feedback control of photocoagulation. J Photochem Photobiol B 1992; 16:113-26. [PMID: 1474421 DOI: 10.1016/1011-1344(92)80003-e] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
During laser treatment, coagulation affects the optical properties of the tissue. In particular, the formation of a white lesion significantly increases the scattering coefficient. This change in the optical properties in turn affects the laser light distribution in the tissue. The white lesion formed during photocoagulation of the retina has a dynamic effect upon reflection and fluence rate. This problem has been simulated on a model medium consisting of a thin absorbing layer covered with a 1 cm thick layer of albumin. The albumin layer is subdivided into coagulated (white) and uncoagulated (clear) layers. The optical properties of each layer have been determined and these values have been used to model light distribution in the medium. One-dimensional adding-doubling and three-dimensional Monte Carlo methods have provided light distributions in the medium for varying thicknesses of the coagulated albumin. Computed fluence reaching the absorbing layer decreased in the presence of a 275 microns or thicker coagulated layer. The coagulated layer attenuates light because it is highly scattering; however, this scattering also leads to a sub-surface peak in fluence rate at a level higher than the incident fluence. The latter effect outweighed the former for coagulated layer thicknesses less than 275 microns. Computed reflectance of argon laser light from a semi-infinite coagulated region initially increased linearly as a function of thickness. As the coagulation thickness increased beyond 4-5 optical depths, the reflectance approached a constant value, R infinity, at 9 optical depths (2 mm). Experimentally measured total reflectance is shown to be an inadequate indicator of the thickness of a lesion (finite coagulated volume); however, central reflectance from a lesion measured with a CCD camera confirmed the computed trends. These results provide a theoretical foundation for control of lesion thickness using reflectance images.
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Affiliation(s)
- M R Jerath
- Biomedical Engineering Program, University of Texas, Austin 78712
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21
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Abstract
Both egg white and egg yolk are excellent media for studying photocoagulation due to thermal response of tissue to laser light. They are readily available, consistently the same, and provide a standard biological medium for different labs to compare results. The irradiation parameters for laser coagulation of these media depend upon their optical properties and their temperature-dependent rate reactions. Estimates of the rate process damage coefficients were obtained from constant-temperature water bath experiments. The activation energy E for egg white was estimated to be 92,000 (cal/M*K] and the integration constant A was found to be 3.8 x 10(57) (second-1).
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Affiliation(s)
- Y Yang
- Department of Electrical and Computer Engineering, University of Texas, Austin
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22
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Yang YL, Markow MS, Rylander HG, Weinberg WS, Welch AJ. Reflectance as an indirect measurement of the extent of laser-induced coagulation. IEEE Trans Biomed Eng 1990; 37:466-73. [PMID: 2345002 DOI: 10.1109/10.55637] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Two-dimensional reflectance images and surface thermal distributions were recorded during argon laser induced coagulation. During laser irradiation, coagulated egg yolk formed a white lesion. The whiteness, or reflectance caused by backscattering of light from the forming lesion, would be measured after a short delay from the onset of laser irradiation. In the experiments which covered exposure time from 4.5 to 17.0 s, we found that it started slowly, the reflectance increased rapidly once the surface temperature of the lesion reached approximately 90 degrees C. After this rapid rise, the reflectance began to taper off until no change in reflectance was recorded. There was a 0.98 correlation between lesion diameter measured from a two dimensional reflectance image and the lesion diameter that was measured microscopically. There was a 0.92 correlation between reflectance at the center of the lesion and microscopically measured depth of coagulation at the same point. However, the correlation between microscopically measured coagulation depth and width was only 0.88.
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Affiliation(s)
- Y L Yang
- Department of Electrical and Computer Engineering, University of Texas, Austin 78712
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23
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Rock RL, Rylander HG. Spontaneous iris retraction occurring after extracapsular cataract extraction and posterior lens implantation in patients with glaucoma. J Am Intraocul Implant Soc 1983; 9:45-7. [PMID: 6853333 DOI: 10.1016/s0146-2776(83)80010-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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24
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Rylander HG, Welch AJ, Fremming B. The effect of radial keratotomy in the rupture strength of pig eyes. Ophthalmic Surg 1983; 14:744-9. [PMID: 6646619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Freshly enucleated pig eyes are significantly weakened following radial keratotomy surgery and are more susceptible to rupture under lateral or axial compression than their unoperated fellow eyes. Patients should be cautioned to restrict hazardous activity in the post-operative period to prevent disastrous globe rupture.
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25
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Abstract
✓ Chronic measurements of epidural pressure made with an induction-powered oscillator transducer revealed several problems with the current design of the device. All transducers failed over a period of months due to the diffusion of extracellular fluid through epoxy seals, which resulted in corrosion of the electrical components. Significant fibrosis occurred around the circumference of the burr hole, which reduced the sensitivity of the transducers. Design modifications are suggested to circumvent these problems.
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26
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Weinstein GW, Rylander HG. Photocoagulation of the fovea. Trans Am Ophthalmol Soc 1978; 76:278-95. [PMID: 112751 PMCID: PMC1311627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The visual outcome, histopathology, and electrodiagnostic tests of a man with a malignant melanoma of the choroid who received foveal argon laser photocoagulation prior to enucleatiion are described. The low intensity foveal burn destroyed only the outer retinal layers and spared the inner retina. Vision was reduced to 20/50 immediately, but recovered to 20/30 after one day. The visually-evoked-potential (VEP) was altered in both amplitude and waveform by the small foveal burn. A patient with solar retinopathy and permanent visual loss demonstrated only waveform changes on VEP testing. Monkeys with mild experimental foveal burns demonstrated outer layer retinal damage and waveform changes on VEP testing. The retinal energy density threshold for argon laser photocoagulation of the fovea is lower than 0.13 joules/mm.2.
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27
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Abstract
An induction-powered oscillator transducer (IPOT) was designed for the chronic measurement of epidural pressure. The transducer was completely implantable so all pressure measurements were made through the intact skin. The IPOT had a linear pressure range from -50 to +200 cm H2O, was sensitive to 1 mm H2O and had a zero drift of less than 1 mm H2O/day under full load. Zero drift was minimized by using a hermetically-sealed metal bellows transducing element which was chemically treated to prevent corrosion and creep. The correlation between epidural pressure and intraventricular pressure was determined during the first 24 hours after implantation in six dogs. Epidural pressure was found to be a linear function of intraventricular fluid pressure. Epidural pressure and intraventricular pressure were essential equal provided the epidural wedge pressure was minimized by proper insertion of the transducer. The correlation between epidural pressure and intraventricular pressure was determined after chronic implantation in five dogs. Epidural pressure was a linear function of intraventricular pressure in the chronically implanted dogs, but epidural pressure was not equal to intraventricular pressure. After chronic implantation, the epidural pressure transducer was not responsive to changes in intraventricular pressure because of mechanical changes in the dura. The dura became stiff and non-compliant. Maximum correlation between epidural pressure and intraventricular fluid pressure in chronic implantations will depend on judicious material selection and mechanical design at the transducer-dura interface.
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Rylander HG, Taylor HL, Wissinger JP, Story JL. Proceedings: Chronic measurement of epidural pressure with an induction power oscillator transducer. J Neurol Neurosurg Psychiatry 1975; 38:409-10. [PMID: 1141943 PMCID: PMC491961 DOI: 10.1136/jnnp.38.4.409-f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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