The effects of laser repetition rate on femtosecond laser ablation of dry bone: a thermal and LIBS study

Abstract

The aim of this study is to understand the effect of varying laser repetition rate on thermal energy accumulation and dissipation as well as femtosecond Laser Induced Breakdown Spectroscopy (fsLIBS) signals, which may help create the framework for clinical translation of femtosecond lasers for surgical procedures. We study the effect of repetition rates on ablation widths, sample temperature, and LIBS signal of bone. SEM images were acquired to quantify the morphology of the ablated volume and fsLIBS was performed to characterize changes in signal intensity and background. We also report for the first time experimentally measured temperature distributions of bone irradiated with femtosecond lasers at repetition rates below and above carbonization conditions. While high repetition rates would allow for faster cutting, heat accumulation exceeds heat dissipation and results in carbonization of the sample. At repetition rates where carbonization occurs, the sample temperature increases to a level that is well above the threshold for irreversible cellular damage. These results highlight the importance of the need for careful selection of the repetition rate for a femtosecond laser surgery procedure to minimize the extent of thermal damage to surrounding tissues and prevent misclassification of tissue by fsLIBS analysis.

Influence of environmental conditions in bovine bone ablation by ultrafast laser

“…All the Raman bands recorded in the spectra of examined samples were assigned to bone compositions. No new phases such as amorphous carbon peak at 1580 and 1350 cm −1 were observed due to the laser ablation under different conditions which indicate that no carbonization occurred . Despite the laser's high fluence and low scanning speed, we observed no thermal damage in any experimental conditions, in stark contrast to previous studies .…”

“…Over the past two decades, a number of studies have looked into replacing mechanical surgical tools by lasers when cutting/drilling bone and/or cartilage . Advantages of using laser ablation over mechanical cutting include more precise cuts, minimal mechanical stress and thermal collateral damage, the ability to work without physical contact and integration with real‐time optical feedback . Many studies have been carried out to characterize bone ablation using infrared (IR) lasers with long pulse duration (nanoseconds to microseconds), for example, CO 2 ( λ = 9.6 μm), Er:YAG ( λ = 2.94 μm), Ho:YAG ( λ = 2.1 μm) and Nd:YAG ( λ = 1.06 μm) .…”

“…Advantages of using laser ablation over mechanical cutting include more precise cuts, minimal mechanical stress and thermal collateral damage, the ability to work without physical contact and integration with real‐time optical feedback . Many studies have been carried out to characterize bone ablation using infrared (IR) lasers with long pulse duration (nanoseconds to microseconds), for example, CO 2 ( λ = 9.6 μm), Er:YAG ( λ = 2.94 μm), Ho:YAG ( λ = 2.1 μm) and Nd:YAG ( λ = 1.06 μm) . It was shown that long‐pulse IR laser ablation may cause melting, carbonizing, cracking and fissuring of hard tissue .…”

Laser-induced breakdown spectroscopy as a potential tool for autocarbonization detection in laserosteotomy

“…This result is in line with results described in literature. [30][31][32][37][38][39][40][41][42][43][44] Note that the collected spectra may include emission lines of the elements found in the ambient air. Interestingly, the higher concentration of carbon in carbonized samples was not only observed in the average intensity of pure carbon emission line (13.77 for carbonized samples as compared with 3.15 for normal samples) but also in the carbon-related molecular emissions of the C 2 (10.12 for carbonized samples as compared with 4.38 for normal samples).…”

Differentiation of femur bone from surrounding soft tissue using laser-induced breakdown spectroscopy as a feedback system for smart laserosteotomy

“…Such feedback mechanisms can rely on photoacoustic, spectroscopic or OCT-based measurements [16][17][18][19][20][21]. Hereby, the potential spectroscopic methods include diffuse reflectance, laser-induced breakdown, Raman, and fluorescence spectroscopy [22][23][24][25][26]. Among them, laser-induced breakdown spectroscopy (LIBS), as a powerful analytical technique, seems to be most promising to us since it enables using the same laser as during the cutting process.…”