title: An image-guided precision proton radiation platform for preclinical in vivo research.
abstract: There are many unknowns in the radiobiology of proton beams and other particle beams. We describe the development and testing of an image-guided low-energy proton system optimized for radiobiological research applications. A 50 MeV proton beam from an existing cyclotron was modified to produce collimated beams (as small as 2 mm in diameter). Ionization chamber and radiochromic film measurements were performed and benchmarked with Monte Carlo simulations (TOPAS). The proton beam was aligned with a commercially-available CT image-guided x-ray irradiator device (SARRP, Xstrahl Inc.). To examine the alternative possibility of adapting a clinical proton therapy system, we performed Monte Carlo simulations of a range-shifted 100 MeV clinical beam. The proton beam exhibits a pristine Bragg Peak at a depth of 21 mm in water with a dose rate of 8.4 Gy min-1(3 mm depth). The energy of the incident beam can be modulated to lower energies while preserving the Bragg peak. The LET was: 2.0 keV µm-1(water surface), 16 keV µm-1(Bragg peak), 27 keV µm-1(10% peak dose). Alignment of the proton beam with the SARRP system isocenter was measured at 0.24 mm agreement. The width of the beam changes very little with depth. Monte Carlo-based calculations of dose using the CT image data set as input demonstrate in vivo use. Monte Carlo simulations of the modulated 100 MeV clinical proton beam show a significantly reduced Bragg peak. We demonstrate the feasibility of a proton beam integrated with a commercial x-ray image-guidance system for preclinical in vivo studies. To our knowledge this is the first description of an experimental image-guided proton beam for preclinical radiobiology research. It will enable in vivo investigations of radiobiological effects in proton beams.
authors.forename: E
authors.initials: E
authors.lastname: Ford
authors.forename: R
authors.initials: R
authors.lastname: Emery
authors.forename: D
authors.initials: D
authors.lastname: Huff
authors.forename: M
authors.initials: M
authors.lastname: Narayanan
authors.forename: J
authors.initials: J
authors.lastname: Schwartz
authors.forename: N
authors.initials: N
authors.lastname: Cao
authors.forename: J
authors.initials: J
authors.lastname: Meyer
authors.forename: R
authors.initials: R
authors.lastname: Rengan
authors.forename: J
authors.initials: J
authors.lastname: Zeng
authors.forename: G
authors.initials: G
authors.lastname: Sandison
authors.forename: G
authors.initials: G
authors.lastname: Laramore
authors.forename: N
authors.initials: N
authors.lastname: Mayr
mesh_terms: D009010:Monte Carlo Method; D061766:Proton Therapy / Q000379:methods*; D011853:Radiobiology / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D014057:Tomography, X-Ray Computed; D014867:Water
chemical_list: D014867:Water