31 August 2011 Filamentation of femtosecond laser pulses as a source for radiotherapy
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Proceedings Volume 8007, Photonics North 2011; 800708 (2011) https://doi.org/10.1117/12.905711
Event: Photonics North 2011, 2011, Ottawa, Canada
Abstract
Here, we report that intense ultra-short laser pulses produce a plasma of low energy electrons (LEEs) by the inverse Bremsstrahlung effect and multiphoton ionization process. The phenomena show five striking characteristics. First, the self-focusing of ultra-short laser pulses creates a plasma of LEEs (6.5 eV), which is concentrated in filaments through an avalanche process. Second, kinetically hot 6.5 eV electrons interact with surrounding molecules resulting in reactive radical species. Third, the dose rate reaches an enormous level of ~2.8 × 1011 Gy/s as determined by a cericcerous sulfate dosimetry and this leads to an ultra-high deposition of energy of between 4.6 × 107 to 8.16 × 107 keV/μm. Fourth, filaments of variable length are produced by femtosecond pulses depending on the pulse duration as determined by a tissue-equivalent radiation polymer gel dosimeter and imaged by magnetic resonance imaging (MRI). These results reveal that one of the very interesting novelty of filamentation is the very low entrance dose, similar to proton irradiation. Lastly, filamentary irradiation results in the decomposition of thymidine in the absence and the presence of oxygen similar to the radiolysis of water.
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Ridthee Meesat, Jean-François Allard, Hakim Belmouaddine, Tiberius Brastaviceanu, Luc Tremblay, Benoit Paquette, Jean-Paul Jay-Gerin, J. Richard Wagner, Martin Lepage, Daniel Houde, "Filamentation of femtosecond laser pulses as a source for radiotherapy", Proc. SPIE 8007, Photonics North 2011, 800708 (31 August 2011); doi: 10.1117/12.905711; https://doi.org/10.1117/12.905711
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