The Experts below are selected from a list of 1131 Experts worldwide ranked by ideXlab platform
Mark S Blumenkranz - One of the best experts on this subject based on the ideXlab platform.
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optimization of the pulsed electron avalanche knife for anterior segment surgery
Biomedical optics, 2003Co-Authors: Daniel Palanker, Alexander Vankov, Michael F Marmor, Kalayaan V Bilbao, Mark S BlumenkranzAbstract:Precise and tractionless tools are needed for cutting and ablation of ocular tissue in such operations as vitreoretinal surgery, capsulotomy, non-penetrating trabeculectomy and many others. Previously we reported about the Pulsed Electron Avalanche Knife capable of tractionless dissection of soft tissue in liquid media using the 100 ns-long plasma-mediated electric discharges applied via a 25 um inlaid disk electrode. In this work we present a next step in the development of this technique, which dramatically improves its precision, the cutting rate and the scope of applicability. (1) Due to spherical geometry of the discharge with the disk-like microelectrode the width of the cut was equal to its depth. To overcome this limitation we apply now a thin cylindrical electrode where the width and the depth of the cut are controlled independently. (2) Cavitation accompanying the sub-microsecond Explosive Evaporation was a major limiting factor in precision of this technique. In a new modality we apply bursts of pulses, which allow for much higher energy deposition without increase in the size of the transient vapor cavity. (3) Coagulation regime for blood vessels larger than 25 microns in diameter was not possible in the initial approach. It is now available due to extension of the electrode in one dimension. (4) Increase in pulse duration up to several tens of microseconds allows for reduction in voltage and, consequently, in width of the insulator. This, in turn, enables development of the ultra-thin electrodes that can be applied via an intraocular endoscope or 25 G needles. The new device was found capable of rapidly and precisely dissecting virtually all types of ocular tissue: from soft membranes to cornea and sclera. In addition to vitreoretinal surgery it applications can now expand into anterior chamber surgery including capsulotomy and trabeculectomy.
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pulsed electron avalanche knife peak for intraocular surgery
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Daniel Palanker, Philip Huie, Jason Miller, Steven R Sanislo, Michael F Marmor, Mark S BlumenkranzAbstract:PURPOSE. To develop a better and more economical instrument for precise, tractionless, “cold” cutting during intraocular surgery. The use of highly localized electric fields rather than laser light as the means of tissue dissection was investigated. METHODS. A high electric field at the tip of a fine wire can, like lasers, initiate plasma formation. Micrometer-length plasma streamers are generated when an insulated 25 micron (mm) wire, exposed to physiological medium at one end, is subjected to nanosecond electrical pulses between 1 and 8 kV in magnitude. The Explosive Evaporation of water in the vicinity of these streamers cuts soft tissue without heat deposition into surrounding material (cold cutting). Streamers of plasma and the dynamics of water Evaporation were imaged using an inverted microscope and fast flash photography. Cutting effectiveness was evaluated on both polyacrylamide gels, on different tissues from excised bovine eyes, and in vivo on rabbit retina. Standard histology techniques were used to examine the tissue. RESULTS. Electric pulses with energies between 150 and 670 mJ produced plasma streamers in saline between 10 and 200 mm in length. Application of electric discharges to dense (10%) polyacrylamide gels resulted in fracturing of the gel without ejection of bulk material. In both dense and softer (6%) gels, layer by layer shaving was possible with pulse energy rather than number of pulses as the determinant of ultimate cutting depth. The instrument made precise partial or full-thickness cuts of retina, iris, lens, and lens capsule without any evidence of thermal damage. Because different tissues require distinct energies for dissection, tissue-selective cutting on complex structures can be performed if the appropriate pulse energies are used; for example, retina can be dissected without damage to the major retinal vessels. CONCLUSIONS. This instrument, called the Pulsed Electron Avalanche Knife (PEAK), can quickly and precisely cut intraocular tissues without traction. The small delivery probe and modest cost make it promising for many ophthalmic applications, including retinal, cataract, and glaucoma surgery. In addition, the instrument may be useful in nonophthalmic procedures such as intravascular surgery and neurosurgery. (Invest Ophthalmol Vis Sci. 2001;42:2673‐2678)
Daniel Palanker - One of the best experts on this subject based on the ideXlab platform.
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optimization of the pulsed electron avalanche knife for anterior segment surgery
Biomedical optics, 2003Co-Authors: Daniel Palanker, Alexander Vankov, Michael F Marmor, Kalayaan V Bilbao, Mark S BlumenkranzAbstract:Precise and tractionless tools are needed for cutting and ablation of ocular tissue in such operations as vitreoretinal surgery, capsulotomy, non-penetrating trabeculectomy and many others. Previously we reported about the Pulsed Electron Avalanche Knife capable of tractionless dissection of soft tissue in liquid media using the 100 ns-long plasma-mediated electric discharges applied via a 25 um inlaid disk electrode. In this work we present a next step in the development of this technique, which dramatically improves its precision, the cutting rate and the scope of applicability. (1) Due to spherical geometry of the discharge with the disk-like microelectrode the width of the cut was equal to its depth. To overcome this limitation we apply now a thin cylindrical electrode where the width and the depth of the cut are controlled independently. (2) Cavitation accompanying the sub-microsecond Explosive Evaporation was a major limiting factor in precision of this technique. In a new modality we apply bursts of pulses, which allow for much higher energy deposition without increase in the size of the transient vapor cavity. (3) Coagulation regime for blood vessels larger than 25 microns in diameter was not possible in the initial approach. It is now available due to extension of the electrode in one dimension. (4) Increase in pulse duration up to several tens of microseconds allows for reduction in voltage and, consequently, in width of the insulator. This, in turn, enables development of the ultra-thin electrodes that can be applied via an intraocular endoscope or 25 G needles. The new device was found capable of rapidly and precisely dissecting virtually all types of ocular tissue: from soft membranes to cornea and sclera. In addition to vitreoretinal surgery it applications can now expand into anterior chamber surgery including capsulotomy and trabeculectomy.
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pulsed electron avalanche knife peak for intraocular surgery
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Daniel Palanker, Philip Huie, Jason Miller, Steven R Sanislo, Michael F Marmor, Mark S BlumenkranzAbstract:PURPOSE. To develop a better and more economical instrument for precise, tractionless, “cold” cutting during intraocular surgery. The use of highly localized electric fields rather than laser light as the means of tissue dissection was investigated. METHODS. A high electric field at the tip of a fine wire can, like lasers, initiate plasma formation. Micrometer-length plasma streamers are generated when an insulated 25 micron (mm) wire, exposed to physiological medium at one end, is subjected to nanosecond electrical pulses between 1 and 8 kV in magnitude. The Explosive Evaporation of water in the vicinity of these streamers cuts soft tissue without heat deposition into surrounding material (cold cutting). Streamers of plasma and the dynamics of water Evaporation were imaged using an inverted microscope and fast flash photography. Cutting effectiveness was evaluated on both polyacrylamide gels, on different tissues from excised bovine eyes, and in vivo on rabbit retina. Standard histology techniques were used to examine the tissue. RESULTS. Electric pulses with energies between 150 and 670 mJ produced plasma streamers in saline between 10 and 200 mm in length. Application of electric discharges to dense (10%) polyacrylamide gels resulted in fracturing of the gel without ejection of bulk material. In both dense and softer (6%) gels, layer by layer shaving was possible with pulse energy rather than number of pulses as the determinant of ultimate cutting depth. The instrument made precise partial or full-thickness cuts of retina, iris, lens, and lens capsule without any evidence of thermal damage. Because different tissues require distinct energies for dissection, tissue-selective cutting on complex structures can be performed if the appropriate pulse energies are used; for example, retina can be dissected without damage to the major retinal vessels. CONCLUSIONS. This instrument, called the Pulsed Electron Avalanche Knife (PEAK), can quickly and precisely cut intraocular tissues without traction. The small delivery probe and modest cost make it promising for many ophthalmic applications, including retinal, cataract, and glaucoma surgery. In addition, the instrument may be useful in nonophthalmic procedures such as intravascular surgery and neurosurgery. (Invest Ophthalmol Vis Sci. 2001;42:2673‐2678)
Michael F Marmor - One of the best experts on this subject based on the ideXlab platform.
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optimization of the pulsed electron avalanche knife for anterior segment surgery
Biomedical optics, 2003Co-Authors: Daniel Palanker, Alexander Vankov, Michael F Marmor, Kalayaan V Bilbao, Mark S BlumenkranzAbstract:Precise and tractionless tools are needed for cutting and ablation of ocular tissue in such operations as vitreoretinal surgery, capsulotomy, non-penetrating trabeculectomy and many others. Previously we reported about the Pulsed Electron Avalanche Knife capable of tractionless dissection of soft tissue in liquid media using the 100 ns-long plasma-mediated electric discharges applied via a 25 um inlaid disk electrode. In this work we present a next step in the development of this technique, which dramatically improves its precision, the cutting rate and the scope of applicability. (1) Due to spherical geometry of the discharge with the disk-like microelectrode the width of the cut was equal to its depth. To overcome this limitation we apply now a thin cylindrical electrode where the width and the depth of the cut are controlled independently. (2) Cavitation accompanying the sub-microsecond Explosive Evaporation was a major limiting factor in precision of this technique. In a new modality we apply bursts of pulses, which allow for much higher energy deposition without increase in the size of the transient vapor cavity. (3) Coagulation regime for blood vessels larger than 25 microns in diameter was not possible in the initial approach. It is now available due to extension of the electrode in one dimension. (4) Increase in pulse duration up to several tens of microseconds allows for reduction in voltage and, consequently, in width of the insulator. This, in turn, enables development of the ultra-thin electrodes that can be applied via an intraocular endoscope or 25 G needles. The new device was found capable of rapidly and precisely dissecting virtually all types of ocular tissue: from soft membranes to cornea and sclera. In addition to vitreoretinal surgery it applications can now expand into anterior chamber surgery including capsulotomy and trabeculectomy.
-
pulsed electron avalanche knife peak for intraocular surgery
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Daniel Palanker, Philip Huie, Jason Miller, Steven R Sanislo, Michael F Marmor, Mark S BlumenkranzAbstract:PURPOSE. To develop a better and more economical instrument for precise, tractionless, “cold” cutting during intraocular surgery. The use of highly localized electric fields rather than laser light as the means of tissue dissection was investigated. METHODS. A high electric field at the tip of a fine wire can, like lasers, initiate plasma formation. Micrometer-length plasma streamers are generated when an insulated 25 micron (mm) wire, exposed to physiological medium at one end, is subjected to nanosecond electrical pulses between 1 and 8 kV in magnitude. The Explosive Evaporation of water in the vicinity of these streamers cuts soft tissue without heat deposition into surrounding material (cold cutting). Streamers of plasma and the dynamics of water Evaporation were imaged using an inverted microscope and fast flash photography. Cutting effectiveness was evaluated on both polyacrylamide gels, on different tissues from excised bovine eyes, and in vivo on rabbit retina. Standard histology techniques were used to examine the tissue. RESULTS. Electric pulses with energies between 150 and 670 mJ produced plasma streamers in saline between 10 and 200 mm in length. Application of electric discharges to dense (10%) polyacrylamide gels resulted in fracturing of the gel without ejection of bulk material. In both dense and softer (6%) gels, layer by layer shaving was possible with pulse energy rather than number of pulses as the determinant of ultimate cutting depth. The instrument made precise partial or full-thickness cuts of retina, iris, lens, and lens capsule without any evidence of thermal damage. Because different tissues require distinct energies for dissection, tissue-selective cutting on complex structures can be performed if the appropriate pulse energies are used; for example, retina can be dissected without damage to the major retinal vessels. CONCLUSIONS. This instrument, called the Pulsed Electron Avalanche Knife (PEAK), can quickly and precisely cut intraocular tissues without traction. The small delivery probe and modest cost make it promising for many ophthalmic applications, including retinal, cataract, and glaucoma surgery. In addition, the instrument may be useful in nonophthalmic procedures such as intravascular surgery and neurosurgery. (Invest Ophthalmol Vis Sci. 2001;42:2673‐2678)
Brian R Dennis - One of the best experts on this subject based on the ideXlab platform.
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velocity characteristics of evaporated plasma using hinode euv imaging spectrometer
The Astrophysical Journal, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with hard X-ray (HXR) observations from Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T = 0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity (v up) was found to scale with temperature as v up (km s–1) ≈ 8-18T(MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km s–1, their line profiles were found to be dominated by a stationary component in contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v down (km s–1) ≈ 60-17T (MK) and was interpreted as the downward-moving "plug" characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy flux of the electron beam was found to be 5 × 1010 erg cm–2 s–1, consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
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velocity characteristics of evaporated plasma using hinode eis
arXiv: Solar and Stellar Astrophysics, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observations from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T=0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity (v_up) was found to scale with temperature as v_up (km s^-1)~8-18 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km s^-1, their line profiles were found to be dominated by a stationary component in contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v_down (km s^-1)~60-17 T (MK) and was interpreted as the downward-moving `plug' characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy flux of the electron beam was found to be >5x10^10 ergs cm^-2 s^-1 consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
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velocity characteristics of evaporated plasma using hinode eis
SPD, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observat,ions from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T=0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity was found to scale with temperature as v(sub up) (kilometers per second) approximately equal to 5-17 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of greater than 200 kilometers per second, their line profiles were found to be dominated by a stationary component in stark contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v(sub down) (kilometers per second) approximately equal to 60-17 T (MK) and was interpreted as the downward-moving 'plug' characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy contained in the electron beam was found to be greater than or equal to 10(sup 11) ergs per square centimeter per second consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
Ryan O Milligan - One of the best experts on this subject based on the ideXlab platform.
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velocity characteristics of evaporated plasma using hinode euv imaging spectrometer
The Astrophysical Journal, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with hard X-ray (HXR) observations from Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T = 0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity (v up) was found to scale with temperature as v up (km s–1) ≈ 8-18T(MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km s–1, their line profiles were found to be dominated by a stationary component in contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v down (km s–1) ≈ 60-17T (MK) and was interpreted as the downward-moving "plug" characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy flux of the electron beam was found to be 5 × 1010 erg cm–2 s–1, consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
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velocity characteristics of evaporated plasma using hinode eis
arXiv: Solar and Stellar Astrophysics, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observations from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T=0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity (v_up) was found to scale with temperature as v_up (km s^-1)~8-18 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km s^-1, their line profiles were found to be dominated by a stationary component in contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v_down (km s^-1)~60-17 T (MK) and was interpreted as the downward-moving `plug' characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy flux of the electron beam was found to be >5x10^10 ergs cm^-2 s^-1 consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
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velocity characteristics of evaporated plasma using hinode eis
SPD, 2009Co-Authors: Ryan O Milligan, Brian R DennisAbstract:This paper presents a detailed study of chromospheric Evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observat,ions from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T=0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity was found to scale with temperature as v(sub up) (kilometers per second) approximately equal to 5-17 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of greater than 200 kilometers per second, their line profiles were found to be dominated by a stationary component in stark contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v(sub down) (kilometers per second) approximately equal to 60-17 T (MK) and was interpreted as the downward-moving 'plug' characteristic of Explosive Evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the Evaporation. The energy contained in the electron beam was found to be greater than or equal to 10(sup 11) ergs per square centimeter per second consistent with the value required to drive Explosive chromospheric Evaporation from hydrodynamic simulations.
