Efficacy and predictability of soft tissue ablation using a prototype Raman-shifted alexandrite laser

Kozub, John A.; Shen, Jin-H.; Joos, Karen M.; Prasad, Ratna; Hutson, M. Shane

doi:10.1117/1.jbo.20.10.105004

Cited by 5 publications

(14 citation statements)

References 25 publications

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“…Table summarizes the measured ablation thresholds. For each of the tested wavelengths and both spot sizes, the threshold fluences are slightly higher than those found previously for RSA laser ablation of cornea .…”

Section: Resultscontrasting

confidence: 54%

“…Note that water vapor absorption severely restricts the pulse energies attainable with the RSA laser at many wavelengths in the 6‐ to 7‐μm range . This limitation makes it necessary to slightly detune the laser from the exact peaks of the targeted tissue absorption bands.…”

Section: Resultsmentioning

confidence: 99%

“…The maximum pulse energies available from the RSA laser used for this work varied from ∼3.0 mJ for wavelengths around 6.1 μm to only ∼1.0 mJ for those near 6.45 μm. When optimally tuned for a specific wavelength, the standard deviation of the mid‐IR pulse energy was ∼25–45% . This variability could be traced back to fluctuations in the flashlamp pump energy of the alexandrite laser that then propagated through the nonlinear Raman conversion processes.…”

Section: Methodsmentioning

confidence: 99%

“…Ablation threshold is defined here as the energy for which a single laser pulse has a 50% probability of ejecting material that is detectable using brightfield illumination. Ablation thresholds were determined using probit analysis and conducted in Mathematica (Wolfram Inc., Champagne, IL) as described previously .…”

Section: Methodsmentioning

confidence: 99%

“…Only the last of these three has achieved sufficient energy per pulse and sufficient average power to cut soft tissues at rates that make surgical applications feasible . This capability has recently been quantified with regards to cornea and gelatin . These are model tissues/phantoms that bracket the range of mechanical properties found among soft tissues, but that are not directly relevant to specific surgical applications for mid‐IR lasers.…”

Section: Introductionmentioning

confidence: 99%

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Optic nerve sheath fenestration using a Raman‐shifted alexandrite laser

Kozub¹,

Shen

Joos

et al. 2015

Lasers Surg Med

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Background and Objective Optic nerve sheath fenestration is an established procedure for relief of potentially damaging overpressure on the optic nerve resulting from idiopathic intracranial hypertension. Prior work showed that a mid-IR free-electron laser could be delivered endoscopically and used to produce an effective fenestration. This study evaluates the efficacy of fenestration using a table-top mid-IR source based on a Raman-shifted alexandrite (RSA) laser. Study Design/Materials and Methods Porcine optic nerves were ablated using light from an RSA laser at wavelengths of 6.09, 6.27 and 6.43 μm and pulse energies up to 3 mJ using both free-space and endoscopic beam delivery through 250-μm I.D. hollow-glass waveguides. Waveguide transmission was characterized, ablation thresholds and etch rates were measured, and the efficacy of endoscopic fenestration was evaluated for ex vivo exposures using both optical coherence tomography and histological analysis. Results Using endoscopic delivery, the RSA laser can effectively fenestrate porcine optic nerves. Performance was optimized at a wavelength of 6.09 μm and delivered pulse energies of 0.5-0.8 mJ (requiring 1.5-2.5 mJ to be incident on the waveguide). Under these conditions, the ablation threshold fluence was 0.8 ± 0.2 J/cm2, the ablation rate was 1-4 μm/pulse, and the margins of ablation craters showed little evidence of thermal or mechanical damage. Nonetheless, nominally identical exposures yielded highly variable ablation rates. This led to fenestrations that ranged from too deep to too shallow – either damaging the underlying optic nerve or requiring additional exposure to cut fully through the sheath. Of 48 excised nerves subjected to fenestration at 6.09 μm, 16 ex vivo fenestrations were judged as good, 23 as too deep, and 9 as too shallow. Conclusions Mid-IR pulses from the RSA laser, propagated through a flexible hollow waveguide, are capable of cutting through porcine optic nerve sheaths in surgically relevant times with reasonable accuracy and low collateral damage. This can be accomplished at wavelengths of 6.09 or 6.27 μm, with 6.09 μm slightly preferred. The depth of ex vivo fenestrations was difficult to control, but excised nerves lack a sufficient layer of cerebrospinal fluid that would provide an additional margin of safety in actual patients.

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Section: Resultscontrasting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optic nerve sheath fenestration using a Raman‐shifted alexandrite laser

Kozub¹,

Shen

Joos

et al. 2015

Lasers Surg Med

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Tissue Ablation with Multi‐Millimeter Depth and Cellular‐Scale Collateral Damage by a Femtosecond Mid‐Infrared Laser Tuned to the Amide‐I Vibration

Tian,

Xiang,

Wen

et al. 2023

Laser & Photonics Reviews

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Laser ablation of bio‐tissues is the key technology of future surgeries, owing to the merits of submicron accuracy, non‐contact operation, and precision control assisted by automation and computer intelligence. Excellent efficiency, minimal collateral damage, biological safety, and tissue selectivity are the ideal parameters for delicate surgical applications. Here, by exploring the mid‐infrared (MIR) resonant ablation and the femtosecond cold processing, tissue ablation with multi‐millimeter depth and cellular collateral damage, enabled by a tabletop femtosecond MIR optical parametric amplifier operating at the amide‐I resonant wavelength of 6.1 µm, is demonstrated. Remarkably, the collateral damage is observed to be 15, <4, and <1 µm in the porcine cornea, sclera, and articular cartilage, respectively, with multi‐millimeter incision depth. In addition, preliminary proof‐of‐concept experiments of tissue‐selective ablation, microchannels on cartilage for drug delivery, laser glaucoma, keratotomy, neurologic tissue incision, dentin deep crater formation, and hypertrophic scarring ablation are demonstrated, which pave the way for high‐precision surgical applications with a tabletop solution.

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