We report a study of ν(μ) charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a μ- and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, dσ/dQ², and study the low energy particle content of the final state. Deviations are found between the measured dσ/dQ² and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state.
We have isolatedνµ charged-current quasi-elastic interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We measure the flux-averaged differential cross-section, dσ/dQ 2 , and compare to several theoretical models of quasi-elastic scattering. Good agreement is obtained with a model where the nucleon axial mass, MA, is set to 0.99 GeV/c 2 but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross-section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher Q 2 favor this interpretation over an alternative in which the axial mass is increased.
Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration.
To develop a compact, proof-of-concept kilovoltage intensity modulated radiotherapy platform to deliver contrast-enhanced radiotherapy (CERT). Methods: The proof-of-concept requirements were threefold: (i) develop a compact means to generate a kilovoltage x-ray broadbeam capable of targeting the K-edge of heavy metal contrast, (ii) investigate the potential clinical application of such a beam in silico, and (iii) construct a limited working prototype of the platform to identify weaknesses in the approach. The x-ray broadbeam was created with a standard kilovoltage x-ray tube heavily filtered with 0.156 mm tungsten. Depth dose and treatment characteristics of the beam were investigated using GEANT4 Monte Carlo framework. The working prototype included a miniaturized multi-rod collimator (MRC) constructed with tungsten carbide rods, 3D-printed gear rack, and an in-house GUI/microprocessor assembly. Measurements of simulated treatments were made with EBT3 radiochromic film. Results: Monte Carlo simulations of pseudo-clinical treatments on a homogeneous spherical Lucite phantom produced dose distributions that indicated surface dose was less than target dose. When simulated-bone was added to the calculations, dose-to-bone was found to be the probable limiting factor in clinical treatment. Nevertheless, when iodine contrast enhancement was accounted for, dose was escalated in the tumor compared to standard megavoltage treatments even with dose-to-bone limitations. Experimentally, after commissioning the MRC and calibrating the radiochromic film, surface dose was compared to maximum dose measured on each film. Surface dose measurements were higher than those in a megavoltage beam, but below the skin toxicity threshold. Dose at depth was reasonable despite increased beam attenuation at these energies from photoelectric interactions in bone. IMRT and non-coplanar dose falloffs around the target were steeper than kV 3D conformal dose falloff. Conclusions: The compact kilovoltage treatment platform presented here proved clinically feasible in both simulation and measurement. It is reasonable to pursue this modality further as a potential CERT platform.
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