title: A survey of target materials and orientations suitable for the production of coherent bremsstrahlung in megavoltage imaging.
abstract: Megavoltage imaging in image-guided radiotherapy usually suffers from the relatively small fraction of photons present in the energy range providing good soft tissue contrast, which corresponds to photon energies below 50 keV. As a consequence, comparatively high imaging doses are required to form low-noise images. Single-crystal targets can help to alleviate this problem through the emission of so-called coherent bremsstrahlung, amounting to a net increase in low-energy photons if the electron beam impinging on a target is carefully aligned with a major symmetry axis of the underlying crystal lattice. In this work, we present an overview of crystal materials and directions that appeared particularly promising during our studies of this phenomenon, based on theoretical considerations. We find that, while diamond targets perform best in absolute terms, those transition metals that exhibit a body-centred cubic lattice appear as interesting alternatives.
authors.affiliation: German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany. t.koenig@dkfz.de
authors.forename: T
authors.initials: T
authors.lastname: Koenig
authors.forename: P
authors.initials: P
authors.lastname: Ziegenhein
authors.forename: U
authors.initials: U
authors.lastname: Oelfke
mesh_terms: D003952:Diagnostic Imaging / Q000379:methods*; D004583:Electrons; D017785:Photons; D011881:Radiotherapy, Computer-Assisted; D028561:Transition Elements
chemical_list: D028561:Transition Elements