Urolithias, calculus formation in the urinary system, affects 5 – 10% of the population
and is a painful and recurrent medical condition. A common approach in the treatment
of calculi is the use of laser radiation, a procedure known as laser lithotripsy, however,
the technique has not yet been fully optimised. This research examines the experimental
parameters relevant to the interactions of the variable microsecond pulsed holmium
laser (λ = 2.12 μm, τp = 120 – 800 μs, I ~ 3 MW cm-2) and the Q-switched neodymium
laser (λ = 1064 nm, τp = 6 ns, I ~ 90 GW cm-2) with calculi.
The laser-calculus interaction was investigated from two perspectives: actions that lead
to calculus fragmentation through the formation of shockwave and plasma, and the
prospect of material analysis of calculi by laser induced breakdown spectroscopy
(LIBS) to reveal elemental composition. This work is expected to contribute to
improved scientific understanding and development of laser lithotripsy.
The results support the general model of thermal and plasma processes leading to
vaporization and pressure pulses. Nd:YAG laser interaction processes were found to be
plasma-mediated and shockwave pressure (~ 12 MPa) dependent on plasma and
strongly influenced by metal ions. Ho:YAG laser-induced shockwaves (~ 50 MPa) were
found to be due to direct vaporisation of water and dependent on laser pulse duration.
The characteristics of the pressure pulse waveforms were found to be different, and the
efficiency and repeatability of shockwave and the nature of the dependencies for the
lasers suggest different bubble dynamics.
For the Nd:YAG laser, LIBS has been demonstrated as a potential tool for in situ
analysis of calculus composition and has been used for the identification of major and
trace quantities of calcium, magnesium, sodium, potassium, strontium, chromium, iron,
copper, lead and other elements.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/4013 |
| Date | 25 November 2009 |
| Creators | Mayo, M E |
| Contributors | Ahmad, S R, Bellerby, J |
| Publisher | Department of Applied Science, Security and Resillience |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, PhD |
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