Speaker
Description
The University of Washington (UW) Medical Center operates a Scanditronix MC50 multi-particle, variable energy cyclotron for fast neutron therapy patient care, radioisotope production, radiation-effects testing of electronic devices, and translational in vitro and in vivo research. The cyclotron is located within the UW Radiation Oncology Department and has four beamlines. The first beamline is to the fast neutron treatment vault, which has an isocentric gantry and a collimator with 40 individually moveable leaves for field shaping. Fast neutrons with an average energy ~ 20 MeV are produced by 50.5 MeV protons incident on a Be target. For many molecular, cellular and clinical endpoints, fast neutrons have a relative biological effectiveness (RBE) in the range from 3-5. Two further beamlines are used for isotope production. A fourth beamline directs proton or alpha beams to a dedicated research room that houses the Precision Preclinical Proton Radiotherapy Platform, which integrates the proton beam with a SARRP (small animal radiation research platform) for comparative studies of x-rays and protons. The typical proton beam utilized for both radiobiology and industrial research is 48.5 MeV and has a maximum field size of 60 x 60mm. It can be operated at a range of dose rates, from conventional up to ultra-high (FLASH) with >100Gy/s. The proton RBE for double strand break induction ranges from ~1 on beam entrance to ~1.4 at the depth of a pristine Bragg peak, which is at a depth of approximately 2 cm. The RBE estimates are based on TOPAS Monte Carlo simulations of the beam line. Animals can be transferred between the clinical neutron vault and the research vault for comparative studies of low linear energy transfer (LET) x-rays and protons and high LET neutrons. For research with spatially fractionated beams, a portable slit collimator system is precisely positioned via motion stages to produce a proton minibeam (pMBRT) with 300μm peak width, 1020μm center-to-center spacing and a peak-to-valley-dose ratio of 19 at 2 mm depth in PMMA. The facility is certified to handle biological specimen for both cellular and small animal research. A radiobiology lab equipped with common lab apparatus is within walking distance.
