Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

Abstract

We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10 microm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20 microm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 microJ, beam diameter 36 microm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mms. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

Planning and simulation of microsurgical laser bone ablation

“…Nowadays short pulsed laser types promise advanced possibilities (i.e. smaller ablations, less traumatization [12]). In the scope of computerassisted surgery two questions are most important:…”

Creation of an incus recess for a middle-ear microphone using a drill or laser ablation: a comparison of equivalent noise level and middle ear transfer function

“…Laser ablation is used for stapes surgery, both to cut the stapedius muscle and the posterior crus of the stapes and to create a recess in the footplate of the stapes [for review see 11 ]. Furthermore, because of the ability to cause minimal trauma to surrounding tissue with laser ablation, it has also been used directly on the ossicular chain [ 12 ] and can be used to remove cholesteatoma from the ossicular chain when attempting to preserve its transfer function [ 13 ]. Nonetheless, whilst direct trauma is reduced using laser ablation, the potential damage to the inner ear through pressure transients remains an open question [ 12 , 14 , 15 ].…”

“…Furthermore, because of the ability to cause minimal trauma to surrounding tissue with laser ablation, it has also been used directly on the ossicular chain [ 12 ] and can be used to remove cholesteatoma from the ossicular chain when attempting to preserve its transfer function [ 13 ]. Nonetheless, whilst direct trauma is reduced using laser ablation, the potential damage to the inner ear through pressure transients remains an open question [ 12 , 14 , 15 ]. Whether laser ablation is advantageous for other types of ear surgery is also an open question and will depend on the shape and size of cut required.…”

Femtosecond laser ablation of the stapes

“…4 Ultrashort laser pulses have been shown to effectively ablate bone and hard tissue. 5–10 This study evaluates the ablation of ossicular bone with a femtosecond laser, commonly used in LASIK eye surgery. 11 …”