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http://hdl.handle.net/11375/11345
Title: | Experimental Evaluation of Bone Drilling using Ultrashort Pulsed Laser Ablation |
Authors: | Emigh, Brent J. |
Advisor: | Fang, Qiyin Hayward, Joseph E. Haugen, Harold K. |
Department: | Medical Physics |
Keywords: | Laser ablation;femtosecond;bone;ultrafast material processing;incubation;Bioimaging and biomedical optics;Bioimaging and biomedical optics |
Publication Date: | Oct-2011 |
Abstract: | <p>Mechanical oscillating drills and saws are used in orthopaedic surgery to cut bone and develop screw-holes; however, their use causes friction resulting in significant thermal damage. Ultrashort pulsed lasers appear well-suited to replace traditional tools as they have the ability to efficiently remove bone tissue while causing only minimal collateral damage. Laser ablation also has the added advantages of: (i) no mechanical vibration; (ii) minimal invasiveness; and (iii) small focus spot size. In this thesis work, we experimentally investigated a few key aspects of ultrashort laser ablation of bone tissue.</p> <p>The ablation threshold of unaltered bone was measured using the <em>D</em><sup>2 </sup>technique and found to range from 1.66 J/cm<sup>2 </sup>± 0.87 J/cm<sup>2</sup> to 2.37 J/cm<sup>2 </sup>± 0.78 J/cm<sup>2</sup> depending on incident pulse number. The reduction in ablation threshold with pulse number was an indication of an incubation effect. Using a power law model, the incubation coefficient, ζ, was measured to be 0.89 ± 0.03.</p> <p>The effect of specific laser parameters and drilling protocols on ablation efficiency was also characterized. For ultrashort pulses (≤10 ps), the removal rate was found to be inversely related to the pulse duration; however, irradiation with 5-10 ps pulses were also shown to result in significant tissue removal. With a pulse repetition rate of 1 kHz, the removal rate was observed to be highest when ablating with 50-100 pulses per spot.</p> <p>Larger volumes (>1 mm<sup>3</sup>) of bone tissue were removed using laser scanning procedures. A series of scanned concentric circles produced a structure ~2.4 mm deep; however, ablated side-lobes were present at oblique angles to the incident beam. A two-layer structure subsequently produced no side-lobes. The ablative precision in trabecular bone was observed to be less than cortical bone. Using mimicked Nd:YAG laser parameters, cylindrical drilling produced craters significantly less deep than those achieved with a typical Ti:Sapphire configuration. The ability to drill large-scale holes using low average pulse energies and optimized scanning procedures will alleviate the stringent requirements for optical components in clinical practice.</p> |
URI: | http://hdl.handle.net/11375/11345 |
Identifier: | opendissertations/6319 7371 2262372 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Size | Format | |
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fulltext.pdf | 3.09 MB | Adobe PDF | View/Open |
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