title: Establishment of a small animal tumour model for in vivo studies with low energy laser accelerated particles.
abstract: BACKGROUND
  The long-term aim of developing a laser based acceleration of protons and ions towards clinical application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra-short pulsed particle beams. Recent in vitro data showed similar effects of laser-accelerated versus "conventional" protons on clonogenic cell survival. As the proton energies currently achieved by laser driven acceleration are too low to penetrate standard tumour models on mouse legs, the aim of the present work was to establish a tumour model allowing for the penetration of low energy protons (~ 20 MeV) to further verify their effects in vivo.
  
  
  METHODS
  KHT mouse sarcoma cells were injected subcutaneously in the right ear of NMRI (nu/nu) mice and the growing tumours were characterized with respect to growth parameters, histology and radiation response. In parallel, the laser system JETI was prepared for animal experimentation, i.e. a new irradiation setup was implemented and the laser parameters were carefully adjusted. Finally, a proof-of-principle experiment with laser accelerated electrons was performed to validate the tumour model under realistic conditions, i.e. altered environment and horizontal beam delivery.
  
  
  RESULTS
  KHT sarcoma on mice ears showed a high take rate and continuous tumour growth after reaching a volume of ~ 5 mm(3). The first irradiation experiment using laser accelerated electrons versus 200 kV X-rays was successfully performed and tumour growth delay was evaluated. Comparable tumour growth delay was found between X-ray and laser accelerated electron irradiation. Moreover, experimental influences, like anaesthesia and positioning at JETI, were found to be negligible.
  
  
  CONCLUSIONS
  A small animal tumour model suitable for the irradiation with low energy particles was established and validated at a laser based particle accelerator. Thus, the translation from in vitro to in vivo experimentation was for the first time realized allowing a broader preclinical validation of radiobiological characteristics and efficacy of laser driven particle accelerators in the future.
authors.affiliation: Department of Radiation Oncology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstr, 74, 01307 Dresden, Germany. Kerstin.Bruechner@uniklinikum-dresden.de.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Brüchner
authors.forename: Elke
authors.initials: E
authors.lastname: Beyreuther
authors.forename: Michael
authors.initials: M
authors.lastname: Baumann
authors.forename: Mechthild
authors.initials: M
authors.lastname: Krause
authors.forename: Melanie
authors.initials: M
authors.lastname: Oppelt
authors.forename: Jörg
authors.initials: J
authors.lastname: Pawelke
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004867:Equipment Design; D005260:Female; D007477:Ions / Q000627:therapeutic use; D007834:Lasers; D028022:Low-Level Light Therapy / Q000295:instrumentation / Q000379:methods; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D010315:Particle Accelerators / Q000295:instrumentation*; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D014407:Tumor Cells, Cultured; D014965:X-Rays
chemical_list: D007477:Ions