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Wang Y, Lu A, Gil-Flamer J, Tan O, Izatt JA, Huang D. Measurement of total blood flow in the normal human retina using Doppler Fourier-domain optical coherence tomography. Br J Ophthalmol 2009; 93:634-7. [PMID: 19168468 DOI: 10.1136/bjo.2008.150276] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
AIM To measure total retinal blood flow in normal human eyes using Doppler Fourier-domain optical coherence tomography (FD-OCT). METHODS 10 normal people aged 35 to 69 years were measured for the right eye using Doppler FD-OCT. Double circular scans around the optic nerve heads were used. Four pairs of circular scans that transected all retinal branch vessels were completed in 2 s. Total retinal blood flow was obtained by summing the flows in the branch veins. Measurements from the eight scans were averaged. Veins with diameters >33 microm were taken into account. RESULTS Total retinal blood flow could be measured in eight of 10 subjects: mean (SD) = 45.6 (3.8) microl/min (range 40.8 to 52.9 microl/min). The coefficient of variation for repeated measurements was 10.5%. Measured vein diameters ranged from 33.3 to 155.4 mum. The averaged flow speed was 19.3 (2.9) mm/s, which did not correlate with vessel diameter. There was no significant difference between flows in the superior and inferior retinal hemispheres. CONCLUSIONS Double circular scanning using Doppler FD-OCT is a rapid and reproducible method to measure total retinal blood flow. These flow values are within the range previously established by laser Doppler flowmetry.
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Affiliation(s)
- Y Wang
- Center for Ophthalmic Optics & Lasers, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
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Davis AM, Rothenberg FG, Shepherd N, Izatt JA. In vivo spectral domain optical coherence tomography volumetric imaging and spectral Doppler velocimetry of early stage embryonic chicken heart development. J Opt Soc Am A Opt Image Sci Vis 2008; 25:3134-43. [PMID: 19037405 DOI: 10.1364/josaa.25.003134] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Progress toward understanding embryonic heart development has been hampered by the inability to image embryonic heart structure and simultaneously measure blood flow dynamics in vivo. We have developed a spectral domain optical coherence tomography system for in vivo volumetric imaging of the chicken embryo heart. We have also developed a technique called spectral Doppler velocimetry (SDV) for quantitative measurement of blood flow dynamics. We present in vivo volume images of the embryonic heart from initial tube formation to development of endocardial cushions of the same embryo over several stages of development. SDV measurements reveal the influence of heart tube structure on blood flow dynamics.
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Affiliation(s)
- A M Davis
- Biomedical Engineering Department, Duke University, 136 Hudson Hall, 3000 Science Drive, Durham, North Carolina 27708, USA.
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Abstract
Compact electrostatic micromirror structures for use in the scanning arm of an optical coherence tomography (OCT) system are described. These devices consist of millimeter-scale mirrors resting upon micrometer-scale polyimide hinges that are tilted by a linear micromachine actuator, the integrated force array (IFA). The IFA is a network of deformable capacitor cells that electrostatically contract with an applied voltage. The support structures, hinges, and actuators are fabricated by photolithography from polyimide-upon-silicon wafers. These devices were inserted into the scanning arm of an experimental OCT imaging system to produce in vitro and in vivo images at frame rates of 4 to 8 Hz.
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Affiliation(s)
- J M Zara
- Department of Electrical and Computer Engineering, George Washington University, Washington, D.C. 20052, USA.
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Abstract
By using the Born approximation deconvolved inverse scattering method instead of the traditional pulse-echo method for analyzing ultrasound pulse reflections from plastic phantoms and soft tissue specimens, improvement in image resolution is shown to be possible provided these targets are fair approximations to layered media. These images are free of speckle and are more vivid than the usual pulse-echo images.
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Affiliation(s)
- W Tobocman
- Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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Radhakrishnan S, Rollins AM, Roth JE, Yazdanfar S, Westphal V, Bardenstein DS, Izatt JA. Real-time optical coherence tomography of the anterior segment at 1310 nm. Arch Ophthalmol 2001; 119:1179-85. [PMID: 11483086 DOI: 10.1001/archopht.119.8.1179] [Citation(s) in RCA: 357] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Recent advances in high-speed scanning technology have enabled a new generation of optical coherence tomographic (OCT) systems to perform imaging at video rate. Here, a handheld OCT probe capable of imaging the anterior segment of the eye at high frame rates is demonstrated for the first time. OBJECTIVE To demonstrate real-time OCT imaging of anterior segment structures. DESIGN Survey of anterior segment structures in normal human subjects. SETTING Laboratory. MAIN OUTCOME MEASURES Achieving real-time imaging of the anterior segment, satisfactory image quality, and convenience of a handheld probe. RESULTS Optical coherence tomographic imaging of the anterior segment of the eyes of human subjects was performed using 1310-nm wavelength light with an image rate of 8 frames per second. Imaging trials demonstrated clear resolution of corneal epithelium and stroma, sclerocorneal junction, sclera, iris pigment epithelium and stroma, and anterior lens capsule. The anterior chamber angle was clearly visualized. Limited imaging of the ciliary body was performed. Real-time imaging of pupillary constriction in response to light stimulus was also performed. CONCLUSION High-speed OCT at 1310-nm wavelength is a potentially useful technique for noninvasive assessment of anterior segment structures. CLINICAL RELEVANCE Our results suggest that real-time OCT has potential applications in glaucoma evaluation and refractive surgery.
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Affiliation(s)
- S Radhakrishnan
- Department of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Das A, Sivak MV, Chak A, Wong RC, Westphal V, Rollins AM, Willis J, Isenberg G, Izatt JA. High-resolution endoscopic imaging of the GI tract: a comparative study of optical coherence tomography versus high-frequency catheter probe EUS. Gastrointest Endosc 2001; 54:219-24. [PMID: 11474394 DOI: 10.1067/mge.2001.116109] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND Both optical coherence tomography (OCT) and catheter probe EUS (CPEUS) are candidates for high-resolution imaging of the GI wall, but their potential roles in this clinical context have not been investigated. METHODS OCT and CPEUS were used to image normal-appearing portions of the GI tract at the same sites. CPEUS was performed with a 20-MHz or a new 30-MHz catheter probe. RESULTS Forty-four histologically confirmed normal sites in 27 patients were evaluated. With OCT, mucosa and muscularis mucosa were clearly seen at all sites. Except for stomach, OCT demonstrated the submucosa in all sites. OCT penetration ranged from 0.7 to 0.9 mm. Microscopic structures such as esophageal glands, intestinal villi, colonic crypts, and blood vessels were easily identified. CPEUS penetration ranged from 10 mm to 20 mm, and 5 to 7 distinct layers were discernible. However, both mucosa and submucosa were seen as thin layers without microscopic detail. CONCLUSION OCT resolution is superior to high-frequency CPEUS, but depth of penetration is limited to mucosa and submucosa. OCT images the major structural components of the mucosa and submucosa whereas CPEUS does not. Potentially, OCT and high-frequency CPEUS may be complementary for clinical imaging.
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Affiliation(s)
- A Das
- Department of Medicine, Division of Gastroenterology, School of Biomedical Engineering, Case Western Reserve University, School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio 44106, USA
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Roth JE, Kozak JA, Yazdanfar S, Rollins AM, Izatt JA. Simplified method for polarization-sensitive optical coherence tomography. Opt Lett 2001; 26:1069-71. [PMID: 18049522 DOI: 10.1364/ol.26.001069] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We report a method for extracting the birefringence properties of biological samples with micrometer-scale resolution in three dimensions, using a new form of polarization-sensitive optical coherence tomography. The method measures net retardance, net fast axis, and total reflectivity as a function of depth into the sample. Polarization sensing is accomplished by illumination of the sample with at least three separate polarization states during consecutive acquisitions of the same pixel, A scan, or B scan. The method can be implemented by use of non-polarization-maintaining fiber and a single detector. In a calibration test of the system, net retardance was measured with an average error of 7.5 degrees (standard deviation 2.2 degrees ) over the retardance range 0 degrees to 180 degrees , and a fast axis with average error of 4.8 degrees over the range 0 degrees to 180 degrees .
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Barton JK, Rollins A, Yazdanfar S, Pfefer TJ, Westphal V, Izatt JA. Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling. Phys Med Biol 2001; 46:1665-78. [PMID: 11419626 DOI: 10.1088/0031-9155/46/6/306] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [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: 11/11/2022]
Abstract
Optical-thermal models that can accurately predict temperature rise and damage in blood vessels and surrounding tissue may be used to improve the treatment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this preliminary study, an optical coherence tomography system operating at 4-30 frames per second was used to visualize laser irradiation of cutaneous (hamster dorsal skin flap) blood vessels. An argon laser was utilized with the following parameters: pulse duration 0.1-2.0 s, spot size 0.1-1.0 mm, power 100-400 mW. Video microscopy images were obtained before and after irradiations, and optical-thermal modelling was performed on two irradiation cases. Time-resolved optical coherence tomography and still images were compared with predictions of temperature rise and damage using Monte Carlo and finite difference techniques. In general, predicted damage agreed with the actual blood vessel and surrounding tissue coagulation seen in images. However, limitations of current optical-thermal models were identified, such as the inability to model the dynamic changes in blood vessel diameter that were seen in the optical coherence tomography images.
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Affiliation(s)
- J K Barton
- Division of Biomedical Engineering, The University of Arizona, Tucson 85721, USA.
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Yazdanfar S, Rollins AM, Izatt JA. Imaging and velocimetry of the human retinal circulation with color Doppler optical coherence tomography. Opt Lett 2000; 25:1448-50. [PMID: 18066244 DOI: 10.1364/ol.25.001448] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Noninvasive monitoring of blood flow in retinal microcirculation may elucidate the progression and treatment of ocular disorders, including diabetic retinopathy, age-related macular degeneration, and glaucoma. Color Doppler optical coherence tomography (CDOCT) is a technique that allows simultaneous micrometer-scale resolution cross-sectional imaging of tissue microstructure and blood flow in living tissues. CDOCT is demonstrated for the first time in living human subjects for bidirectional blood-flow mapping of retinal vasculature.
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Trivedi NS, Wang HW, Nieminen AL, Oleinick NL, Izatt JA. Quantitative analysis of Pc 4 localization in mouse lymphoma (LY-R) cells via double-label confocal fluorescence microscopy. Photochem Photobiol 2000; 71:634-9. [PMID: 10818795 DOI: 10.1562/0031-8655(2000)071<0634:qaopli>2.0.co;2] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [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: 11/19/2022]
Abstract
Photodynamic therapy (PDT) is a novel cancer therapy that uses light-activated drugs (photosensitizers) to destroy tumor tissue. Reactive oxygen species produced during PDT are thought to cause the destruction of tumor tissue. However, the precise mechanism of PDT is not completely understood. To provide insight into the in vitro mechanisms of PDT, we studied the subcellular localization of the photosensitizer HOSiPcOSi(CH3)2-(CH2)3N(CH3)2 (Pc 4) in mouse lymphoma (LY-R) cells using double-label confocal fluorescence microscopy. This technique allowed us to observe the relative distributions of Pc 4 and an organelle-specific dye within the same cell via two, spectrally distinct, fluorescence images. To quantify the localization of Pc 4 within different organelles, linear correlation coefficients from the fluorescence data of Pc 4 and the organelle-specific dyes were calculated. Using this measurement, the subcellular spatial distributions of Pc 4 could be successfully monitored over an 18 h period. At early times (0-1 h) after introduction of Pc 4 to LY-R cells, the dye was found in the mitochondria, lysosomes and Golgi apparatus, as well as other cytoplasmic membranes, but not in the plasma membrane or the nucleus. Over the next 2 h, there was some loss of Pc 4 from the lysosomes as shown by the correlation coefficients. After an additional incubation period of 2 h Pc 4 slowly increased its accumulation in the lysosomes. The highest correlation coefficient (0.65) was for Pc 4 and BODIPY-FL C5 ceramide, which targets the Golgi apparatus, and also binds to other cytoplasmic membranes. The correlation coefficient was also high (0.60) for Pc 4 and a mitochondria-targeting dye (Mitotracker Green FM). Both of these correlation coefficients were higher than that for Pc 4 with the lysosome-targeting dye (Lysotracker Green DND-26). The results suggest that Pc 4 binds preferentially and strongly to mitochondria and Golgi complexes.
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Affiliation(s)
- N S Trivedi
- Department of Biomedical Engineering, Case School of Engineering and School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Sivak MV, Kobayashi K, Izatt JA, Rollins AM, Ung-Runyawee R, Chak A, Wong RC, Isenberg GA, Willis J. High-resolution endoscopic imaging of the GI tract using optical coherence tomography. Gastrointest Endosc 2000; 51:474-9. [PMID: 10744825 DOI: 10.1016/s0016-5107(00)70450-0] [Citation(s) in RCA: 231] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Optical coherence tomography (OCT) has demonstrated the microscopic structure of the gastrointestinal (GI) tract mucosa and submucosa in vitro. We evaluated a prototype OCT system and assessed the feasibility of OCT in the human GI tract. METHODS The 2.4 mm diameter prototype OCT probe, inserted through an endoscope, provides a 360-degree radial scan. Images (6.7 frames/sec) are displayed on a television monitor. Tissue contact is not required. In patients undergoing elective endoscopy, OCT images were obtained of normal mucosa (confirmed by biopsy). RESULTS Seventy-two sites were imaged (38 patients): esophagus (21), stomach (12), duodenum (11), terminal ileum (4), colon (15), and rectum (9). Varying the distance between the probe and the mucosal surface produced images of the GI wall of varying depth. When held about 1 mm above the mucosal surface, the images consisted of mucosal structures such as colonic crypts, gastric pits, and duodenal villi. With the probe held against the wall, the OCT image comprised several layers interpreted as mucosa, muscularis mucosae, and submucosa. Structures including blood vessels were evident within the submucosa. A probe with a 0.5 mm working distance to the focal point provided the best images. Reducing the frame rate to 4.0 per second facilitated image interpretation. CONCLUSIONS OCT is feasible in the human GI tract and provides interpretable high-resolution images of mucosa and submucosa.
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Affiliation(s)
- M V Sivak
- Department of Medicine, Division of Gastroenterology, School of Biomedical Engineering, and Department of Pathology, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Ohio 44106, USA
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van Leeuwen TG, Kulkarni MD, Yazdanfar S, Rollins AM, Izatt JA. High-flow-velocity and shear-rate imaging by use of color Doppler optical coherence tomography. Opt Lett 1999; 24:1584-6. [PMID: 18079871 DOI: 10.1364/ol.24.001584] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Color Doppler optical coherence tomography (CDOCT) is capable of precise velocity mapping in turbid media. Previous CDOCT systems based on the short-time Fourier transform have been limited to maximum flow velocities of the order of tens of millimeters per second. We describe a technique, based on interference signal demodulation at multiple frequencies, to extend the physiological relevance of CDOCT by increasing the dynamic range of measurable velocities to hundreds of millimeters per second. The physiologically important parameter of shear rate is also derived from CDOCT measurements. The measured flow-velocity profiles and shear-rate distributions correlate very well with theoretical predictions. The multiple demodulation technique, therefore, may be useful to monitor blood flow in vivo and to identify regions with high and low shear rates.
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Affiliation(s)
- T G van Leeuwen
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106-5066, USA
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Abstract
We introduce a family of power-conserving fiber-optic interferometer designs for low-coherence reflectometry that use optical circulators, unbalanced couplers, and (or) balanced heterodyne detection. Simple design equations for optimization of the signal-to-noise ratio of the interferometers are expressed in terms of relevant signal and noise sources and measurable system parameters. We use the equations to evaluate the expected performance of the new configurations compared with that of the standard Michelson interferometer that is commonly used in optical coherence tomography (OCT) systems. The analysis indicates that improved sensitivity is expected for all the new interferometer designs, compared with the sensitivity of the standard OCT interferometer, under high-speed imaging conditions.
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Rollins AM, Ung-Arunyawee R, Chak A, Wong RC, Kobayashi K, Sivak MV, Izatt JA. Real-time in vivo imaging of human gastrointestinal ultrastructure by use of endoscopic optical coherence tomography with a novel efficient interferometer design. Opt Lett 1999; 24:1358-60. [PMID: 18079803 DOI: 10.1364/ol.24.001358] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We report on the design and initial clinical experience with a real-time endoscopic optical coherence tomography (EOCT) imaging system. The EOCT unit includes a high-speed optical coherence tomography interferometer, endoscope-compatible catheter probes, and real-time data capture and display hardware and software. Several technological innovations are introduced that improve EOCT efficiency and performance. In initial clinical studies using the EOCT system, the esophagus, stomach, duodenum, ileum, colon, and rectum of patients with normal endoscopic findings were examined. In these initial investigations, EOCT imaging clearly delineated the substructure of the mucosa and submucosa in several gastrointestinal organs; microscopic structures such as glands, blood vessels, pits, villi, and crypts were also observed.
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Wang HW, Willis J, Canto MI, Sivak MV, Izatt JA. Quantitative laser scanning confocal autofluorescence microscopy of normal, premalignant, and malignant colonic tissues. IEEE Trans Biomed Eng 1999; 46:1246-52. [PMID: 10513130 DOI: 10.1109/10.790502] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [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: 11/09/2022]
Abstract
Laser scanning confocal autofluorescence microscopy (LSCAM) using 351- to 364-nm excitation light was used to quantitatively compare fluorescent spectral emission of unstained, frozen histological sections of normal, premalignant, and malignant colonic tissues. To identify the spatial origins of fluorescent signals accurately, the same frozen section slides used for microscopy were fixed and histochemically stained immediately following LSCAM imaging. Tissue fluorescence emission was quantified in terms of the intrinsic fluorescence coefficient beta (lambda), defined as the fluorescence power per unit tissue volume per unit wavelength (centered at lambda) divided by the incident light irradiance. Over all emission wavelengths, colonic tissues emitted autofluorescence ranging from beta (lambda) approximately 10(-1.5) to 10(-3.0) cm-1. In the 530- to 610-nm spectral region, markedly increased autofluorescence (beta up to 10(-2.5)) was observed in the dysplastic cells of adenomatous polyps, as compared to normal epithelial cells. Compared to adenomatous polyps, decreased dysplastic cell autofluorescence was observed in adenocarcinoma. The brightest fluorescence in the lamina propria, which was attributed to eosinophils (beta approximately 10(-2.5)) in previous studies, was also observed in other granular structures (beta up to 10(-1.4)). LSCAM reveals quantitative significant differences in fluorescence emission between normal and diseased colonic tissues.
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Affiliation(s)
- H W Wang
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
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Kehlet Barton J, Izatt JA, Kulkarni MD, Yazdanfar S, Welch AJ. Three-dimensional reconstruction of blood vessels from in vivo color Doppler optical coherence tomography images. Dermatology 1999; 198:355-61. [PMID: 10449934 DOI: 10.1159/000018148] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [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: 11/19/2022] Open
Abstract
PURPOSE Current laser treatment for vascular disorders such as port wine stains can have incomplete or unacceptable results. A customized treatment strategy based on knowledge of the patient's blood vessel structure may effect an improved clinical outcome. PROCEDURE We tested the feasibility of using color Doppler optical coherence tomography (OCT) and image processing techniques to locate, measure and reconstruct cutaneous blood vessels in rat and hamster skin. OCT is a recent, potentially noninvasive technique for imaging subsurface tissue structures with micrometer scale resolution. RESULTS Blood vessels were identified in a series of cross-sectional images, then a three-dimensional reconstruction was made. Parameters that can affect optimum laser treatment parameters, such as average blood vessel depth and luminal diameter, were found from the images. CONCLUSION This study shows that color Doppler OCT is a potential tool for improving laser treatment of vascular disorders.
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Affiliation(s)
- J Kehlet Barton
- Biomedical Engineering Program, University of Arizona, Tucson, Ariz. 85721-0104, USA.
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Kulkarni MD, van Leeuwen TG, Yazdanfar S, Izatt JA. Velocity-estimation accuracy and frame-rate limitations in color Doppler optical coherence tomography. Opt Lett 1998; 23:1057-1059. [PMID: 18087428 DOI: 10.1364/ol.23.001057] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Color Doppler optical coherence tomography (CDOCT) is a recent innovation that allows spatially localized flow-velocity mapping simultaneously with microstructural imaging. We present a theoretical model for velocity-image formation in CDOCT. The proportionality between the heterodyne detector current Doppler power spectrum in CDOCT and the optical source power spectrum is established. We show that stochastic modifications of the Doppler spectrum by fluctuating scatterer distributions in the flow field give rise to unavoidable velocity-estimation inaccuracies as well as to a fundamental trade-off between image-acquisition rate and velocity precision. Novel algorithms that permit high-fidelity depth-resolved measurements of velocities in turbid media are also reported.
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Affiliation(s)
- M D Kulkarni
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Kobayashi K, Izatt JA, Kulkarni MD, Willis J, Sivak MV. High-resolution cross-sectional imaging of the gastrointestinal tract using optical coherence tomography: preliminary results. Gastrointest Endosc 1998; 47:515-23. [PMID: 9647378 DOI: 10.1016/s0016-5107(98)70254-8] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Optical coherence tomography (OCT) is a novel technique for noninvasive cross-sectional imaging with high spatial resolution (10 to 20 microm). OCT is similar to B-mode ultrasound except that it uses infrared light rather than ultrasound. We studied OCT imaging of the gastrointestinal (GI) tract in vitro to analyze the potential of this technique for endoscopic applications. METHODS Human gastrointestinal tissues harvested from surgical resection and autopsy specimens were used. Specimens were imaged within 5 hours of resection or snap frozen in liquid nitrogen. After imaging, OCT scan locations were carefully marked using dye microinjections, fixed, and prepared for routine histologic processing. OCT images were then compared and correlated with the histologic sections. RESULTS OCT images demonstrated clear delineation of the mucosa and submucosa in most specimens. Furthermore, microscopic structures such as crypts, blood vessels, or esophageal glands in the submucosa and lymphatic nodules were observed. CONCLUSIONS The resolution of OCT images of GI wall is sufficient to delineate the microscopic structure of the mucosa and submucosa. Potentially, OCT would allow in vivo imaging at endoscopy of the microstructure of the mucosa and submucosa. This would be particularly useful in the detection and staging of small lesions such as early stage cancers.
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Affiliation(s)
- K Kobayashi
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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Abstract
The combined excited-state phosphorescence life-times of an alexandrite crystal and platinum tetraphenylporphyrin Pt(TPP) in a single-fiber sensor are used to monitor temperature and oxygen concentration in the physiological range from 15-45 degrees C and 0-50% O2 with precision of 0.24 degree C and 0.15% O2 and accuracy of 0.28 degree C and 0.2% O2. A 500-micron cubic alexandrite crystal bound to the distal end of a 750-micron-diameter optical fiber core and the Pt(TPP) coated circumferentially with a length of 1 cm from the end of the same fiber are excited with pulsed super-bright blue LED light. This apparatus uses a 125-kHz sampler for data acquisition and frequency domain methods for signal processing. The instrument amplifies both the dc and ac components of the photomultiplier output and band limits the signal to 20 kHz. The fundamental frequency of the excitation is set to 488.3 Hz and the highest harmonic used is the 35th. This bandlimited signal is sampled and averaged over a few hundred cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic are then computed. At least four log-spaced harmonic phases or modulations are averaged before decoding the two lifetimes of temperature and oxygen phosphorescent sensors. A component of zero lifetime is introduced to account for the excitation backscatter leakage through optical interference filters seen by the photodetector. Linear and second-order empirical polynomials are employed to compute the temperatures and oxygen concentrations from the inverse lifetimes. In the situation of constant oxygen concentration, the lifetime of Pt(TPP) changes with temperature but can be compensated using the measured temperature lifetime. The system drift is 0.24 degree C for the temperature measurement and 0.59% for the oxygen concentration measurement over 30 h of continuous operation. The instrumentation and methods allow for 6-s update times and 90-s full-response times.
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Affiliation(s)
- S C Liao
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
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Izatt JA, Kulkarni MD, Yazdanfar S, Barton JK, Welch AJ. In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography. Opt Lett 1997; 22:1439-41. [PMID: 18188263 DOI: 10.1364/ol.22.001439] [Citation(s) in RCA: 167] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We describe a novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo imaging of blood flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform flow imaging simultaneous with conventional OCT imaging. Cross-sectional maps of blood flow velocity with <50-microm spatial resolution and <0.6-mm/s velocity precision were obtained through intact skin in living hamster subdermal tissue. This technology has several potential medical applications.
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Brezinski ME, Tearney GJ, Bouma BE, Izatt JA, Hee MR, Swanson EA, Southern JF, Fujimoto JG. Optical coherence tomography for optical biopsy. Properties and demonstration of vascular pathology. Circulation 1996; 93:1206-13. [PMID: 8653843 DOI: 10.1161/01.cir.93.6.1206] [Citation(s) in RCA: 405] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Optical coherence tomography (OCT) is an recently developed medical diagnostic technology that uses back-reflected infrared light to perform in situ micron scale tomographic imaging. In this work, we investigate the ability of OCT to perform micron scale tomographic imaging of the internal microstructure of in vitro atherosclerotic plaques. METHODS AND RESULTS Aorta and relevant nonvascular tissue were obtained at autopsy. Two-dimensional cross-sectional imaging of the exposed surface of the arterial segments was performed in vitro with OCT. A 1300-nm wavelength, superluminescent diode light source was used that allows an axial spatial resolution of 20 microns. The signal-to-noise ratio was 109 dB. Images were displayed in gray scale or false color, Imaging was performed over 1.5 mm into heavily calcified tissue, and a high contrast was noted between lipid- and water-based constituents, making OCT attractive for intracoronary imaging. The 20-microns axial resolution of OCT allowed small structural details such as the width of intimal caps and the presence of fissures to be determined. The extent of lipid collections, which had a low backscattering intensity, also were well documented. CONCLUSIONS OCT represents a promising new technology for imaging vascular microstructure with a level of resolution not previously achieved with the use of other imaging modalities. It does not required direct contact with the vessel wall and can be performed with a catheter integrated with a relatively inexpensive optical fiber. The high contrast among tissue constituents, high resolution, and ability to penetrate heavily calcified tissue make OCT an attractive new imaging technology for intracoronary diagnostics.
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Affiliation(s)
- M E Brezinski
- Cardiac Unit, Massachusetts General Hospital and Harvard Medical School, Boston 02139, USA
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Schuman JS, Hee MR, Puliafito CA, Wong C, Pedut-Kloizman T, Lin CP, Hertzmark E, Izatt JA, Swanson EA, Fujimoto JG. Quantification of nerve fiber layer thickness in normal and glaucomatous eyes using optical coherence tomography. Arch Ophthalmol 1995; 113:586-96. [PMID: 7748128 DOI: 10.1001/archopht.1995.01100050054031] [Citation(s) in RCA: 557] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
PURPOSE Quantitative assessment of nerve fiber layer (NFL) thickness in normal and glaucomatous eyes, and correlation with conventional measurements of the optic nerve structure and function. METHODS We studied 59 eyes of 33 subjects by conventional ophthalmologic physical examination, Humphrey 24-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. RESULTS Nerve fiber layer thickness as measured by optical coherence tomography demonstrated a high degree of correlation with functional status of the optic nerve, as measured by visual field examination (P = .0001). Neither cupping of the optic nerve nor neuroretinal rim area were as strongly associated with visual field loss as was NFL thickness (P = .17 and P = .21, respectively). Cupping correlated with NFL thickness only when the cup was small (cup-to-diameter ratio, 0.1 to 0.3) or large (cup-to-diameter ratio, 0.8 to 1.0) (P = .006); there was no correlation between cupping and NFL thickness otherwise. Nerve fiber layer, especially in the inferior quadrant, was significantly thinner in glaucomatous eyes than in normal eyes (P = .04). Finally, we found a decrease in NFL thickness with aging, even when controlling for factors associated with the diagnosis of glaucoma (P = .03). CONCLUSIONS Nerve fiber layer thickness can be measured using optical coherence tomography. These measurements provide good structural and functional correlation with known parameters.
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Affiliation(s)
- J S Schuman
- New England Eye Center, Tufts University School of Medicine, Boston, Mass., USA
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Abstract
OBJECTIVE To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. DESIGN Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. SETTING Research laboratory. PARTICIPANTS Convenience sample of normal human subjects. MAIN OUTCOME MEASURES Correlation of optical coherence retinal tomographs with known normal retinal anatomy. RESULTS Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10-microns depth resolution. CONCLUSION Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.
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Affiliation(s)
- M R Hee
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge
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Puliafito CA, Hee MR, Lin CP, Reichel E, Schuman JS, Duker JS, Izatt JA, Swanson EA, Fujimoto JG. Imaging of macular diseases with optical coherence tomography. Ophthalmology 1995; 102:217-29. [PMID: 7862410 DOI: 10.1016/s0161-6420(95)31032-9] [Citation(s) in RCA: 775] [Impact Index Per Article: 26.7] [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: 01/27/2023] Open
Abstract
BACKGROUND/PURPOSE To assess the potential of a new diagnostic technique called optical coherence tomography for imaging macular disease. Optical coherence tomography is a novel noninvasive, noncontact imaging modality which produces high depth resolution (10 microns) cross-sectional tomographs of ocular tissue. It is analogous to ultrasound, except that optical rather than acoustic reflectivity is measured. METHODS Optical coherence tomography images of the macula were obtained in 51 eyes of 44 patients with selected macular diseases. Imaging is performed in a manner compatible with slit-lamp indirect biomicroscopy so that high-resolution optical tomography may be accomplished simultaneously with normal ophthalmic examination. The time-of-flight delay of light backscattered from different layers in the retina is determined using low-coherence interferometry. Cross-sectional tomographs of the retina profiling optical reflectivity versus distance into the tissue are obtained in 2.5 seconds and with a longitudinal resolution of 10 microns. RESULTS Correlation of fundus examination and fluorescein angiography with optical coherence tomography tomographs was demonstrated in 12 eyes with the following pathologies: full- and partial-thickness macular hole, epiretinal membrane, macular edema, intraretinal exudate, idiopathic central serous chorioretinopathy, and detachments of the pigment epithelium and neurosensory retina. CONCLUSION Optical coherence tomography is potentially a powerful tool for detecting and monitoring a variety of macular diseases, including macular edema, macular holes, and detachments of the neurosensory retina and pigment epithelium.
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Affiliation(s)
- C A Puliafito
- New England Eye Center, Tufts University School of Medicine, Boston, MA 02111
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Izatt JA, Hee MR, Swanson EA, Lin CP, Huang D, Schuman JS, Puliafito CA, Fujimoto JG. Micrometer-scale resolution imaging of the anterior eye in vivo with optical coherence tomography. Arch Ophthalmol 1994; 112:1584-9. [PMID: 7993214 DOI: 10.1001/archopht.1994.01090240090031] [Citation(s) in RCA: 527] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE To demonstrate a new diagnostic technique, optical coherence tomography, for high-resolution cross-sectional imaging of structures in the anterior segment of the human eye in vivo. Optical coherence tomography is a new, noninvasive, noncontact optical imaging modality that has spatial resolution superior to that of conventional clinical ultrasonography (< 20 microns) and high sensitivity (dynamic range, > 90 dB). DESIGN Survey of intraocular structure and dimension measurements. SETTING Laboratory. PATIENTS Convenience sample. MAIN OUTCOME MEASURES Correlation with range of accepted normal intraocular structure profiles and dimensions. RESULTS Direct in vivo measurements with micrometer-scale resolution were performed of corneal thickness and surface profile (including visualization of the corneal epithelium), anterior chamber depth and angle, and iris thickness and surface profile. Dense nuclear cataracts were successfully imaged through their full thickness in a cold cataract model in calf eyes in vitro. CONCLUSIONS Optical coherence tomography has potential as a diagnostic tool for applications in noncontact biometry, anterior chamber angle assessment, identification and monitoring of intraocular masses and tumors, and elucidation of abnormalities of the cornea, iris, and crystalline lens.
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Affiliation(s)
- J A Izatt
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge
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Bouma B, Gouveia-Neto A, Izatt JA, Russell J, Sierra R, Keller U, Fujimoto JG. Hybrid mode locking of a flash-lamp-pumped Ti:Al2O3 laser. Opt Lett 1994; 19:1858. [PMID: 19855677 DOI: 10.1364/ol.19.001858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Abstract
We describe a novel technique, based on optical coherence tomography, for enhanced optical sectioning in confocal microscopy. Confocal imaging deep into highly scattering media is demonstrated and compared with the predictions of a single-backscatter theory.
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Ramaswamy M, Gouveia-Neto AS, Negus DK, Izatt JA, Fujimoto JG. 2.3-ps pulses from a Kerr-lens mode-locked lamp-pumped Nd:YLF laser with a microdot mirror. Opt Lett 1993; 18:1825-1827. [PMID: 19829417 DOI: 10.1364/ol.18.001825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Pulses as short as 2.3 ps have been generated by passive mode locking of a lamp-pumped Nd:YLF laser with a microdot mirror mode locker for Kerr-lens mode-locking (KLM) saturable absorber action and a compact Gires-Tournois interferometer for dispersion compensation. KLM was initiated with an acousto-optic modulator. Average output powers of 800 mW have been achieved. This result demonstrates the potential use of KLM for generating near-bandwidth-limited pulses from high-power lamp-pumped sources.
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Swanson EA, Izatt JA, Hee MR, Huang D, Lin CP, Schuman JS, Puliafito CA, Fujimoto JG. In vivo retinal imaging by optical coherence tomography. Opt Lett 1993; 18:1864-6. [PMID: 19829430 DOI: 10.1364/ol.18.001864] [Citation(s) in RCA: 418] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We describe what are to our knowledge the first in vivo measurements of human retinal structure with optical coherence tomography. These images represent the highest depth resolution in vivo retinal images to date. The tomographic system, image-processing techniques, and examples of high-resolution tomographs and their clinical relevance are discussed.
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Hee MR, Izatt JA, Jacobson JM, Fujimoto JG, Swanson EA. Femtosecond transillumination optical coherence tomography. Opt Lett 1993; 18:950-2. [PMID: 19823255 DOI: 10.1364/ol.18.000950] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We describe a new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media. Time gating is performed with a fiber-optic interferometer with femtosecond pulses and coherent heterodyne detection to achieve a 130-dB dynamic range. A confocal imaging arrangement provides additional spatial discrimination against multiply scattered light. By time gating ballistic photons, we achieve 125-microm-resolution images of absorbing objects in media 27 scattering mean free paths thick. We derive a fundamental limit on ballistic imaging thickness based on quantum noise considerations.
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Abstract
Pulsed laser ablation of calcified biological tissue was studied at several wavelengths in the near-ultraviolet, visible, near- and mid-infrared regions of the spectrum. The primary tissue model was bovine shank bone, while human arterial calcified plaque and normal human artery wall were also studied at selected wavelengths for comparison. Laser irradiances were on the order of MW/mm2, fluences ranged up to 1000 mJ/mm2, and repetition rates varied between 0.3-10 Hz. Spot sizes on the tissue surface ranged from 150 to 850 microns. Laser craters made with wavelengths between lambda = 295 nm and lambda = 375 nm and in the lambda = 3 microns region exhibited the highest quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam. Craters drilled with visible wavelengths between lambda = 450 nm and lambda = 590 nm were generally larger than the incident laser beam spot, irregular in shape and often surrounded by large flakes of tissue debris. Ablation fluence thresholds increased with wavelength through the visible wavelengths and into the mid-infrared, but dropped to their lowest values near lambda = 3 microns. Fluence thresholds obtained with the tissue under a 1 mm depth of saline were approximately twice air thresholds. Ablation yields also varied with wavelength, probably due to increased scattering in the visible region, and were the same under saline as in air.
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Affiliation(s)
- J A Izatt
- G.R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge 02139
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Partovi F, Izatt JA, Cothren RM, Kittrell C, Thomas JE, Strikwerda S, Kramer JR, Feld MS. A model for thermal ablation of biological tissue using laser radiation. Lasers Surg Med Suppl 1987; 7:141-54. [PMID: 3613805 DOI: 10.1002/lsm.1900070202] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We present a theory of thermal laser ablation based on the heat equation and on an energy balance equation derived from it. Ablation is assumed to be brought about by the heating and evaporation of tissue water. The model is three-dimensional, and scattering and the water-steam phase transition are explicitly taken into account. The model predicts threshold parameters and a steady-state ablation velocity in terms of the optical and thermal properties of the tissue and the laser beam intensity and spot diameter.
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