title: Imaging-therapy computed tomography with quasi-monochromatic X-rays.
abstract: BACKGROUND
  Computed tomography (CT) is a widespread and highly precise technique working in the energy range around 50-100 keV. For radiotherapy, however, the MeV energy range enables a better dose distribution. This gap between diagnosis and therapy can be overcome by the use of a modified CT machine in combination with heavy elements targeted to the tumour and used as photoelectric radiation enhancer.
  
  
  METHODS
  The experimental setup consists of an X-ray optical module mounted at the exit of the X-ray tube of a clinical CT. The module converts the standard fan-shaped beam into a high intensity, monochromatized and focused beam. The radiation was characterized using an energy-dispersive detection system calibrated by synchrotron radiation and gel dosimetry. The photoelectric radiation enhancement for different elements was calculated and experimentally verified.
  
  
  RESULTS
  The X-ray optical module filters selectively the energy of the tungsten K alpha-emission line (59.3 keV) with a full width at half maximum (FWHM) of 5 keV and focused the radiation onto a focal spot which coincides with the isocentre of the gantry. This results in a steep dose gradient at the centre of rotation qualified for locoregional radiation therapy. The photon energy of the quasi-monochromatic radiation agrees with the energy range of maximal photoelectric dose enhancement for gadolinium and iodine.
  
  
  CONCLUSIONS
  An additional X-ray optical module optimized for targeted therapy and photoelectric dose enhancement allows the combination of diagnosis and radiotherapy on a clinical CT.
authors.affiliation: Bayer Schering Pharma AG, Contrast Media Research, Muellerstrasse 178, 13353 Berlin, Germany. gregor.jost@bayerhealthcare.com
authors.forename: Gregor
authors.initials: G
authors.lastname: Jost
authors.forename: Sven
authors.initials: S
authors.lastname: Golfier
authors.forename: Ruediger
authors.initials: R
authors.lastname: Lawaczeck
authors.forename: Hanns-Joachim
authors.initials: HJ
authors.lastname: Weinmann
authors.forename: Martin
authors.initials: M
authors.lastname: Gerlach
authors.forename: Levent
authors.initials: L
authors.lastname: Cibik
authors.forename: Michael
authors.initials: M
authors.lastname: Krumrey
authors.forename: Daniel
authors.initials: D
authors.lastname: Fratzscher
authors.forename: Johannis
authors.initials: J
authors.lastname: Rabe
authors.forename: Vladimir
authors.initials: V
authors.lastname: Arkadiev
authors.forename: Michael
authors.initials: M
authors.lastname: Haschke
authors.forename: Norbert
authors.initials: N
authors.lastname: Langhoff
authors.forename: Reiner
authors.initials: R
authors.lastname: Wedell
authors.forename: Lutz
authors.initials: L
authors.lastname: Luedemann
authors.forename: Peter
authors.initials: P
authors.lastname: Wust
authors.forename: Hubertus
authors.initials: H
authors.lastname: Pietsch
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D011882:Radiotherapy, High-Energy / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014056:Tomography, X-Ray / Q000295:instrumentation* / Q000379:methods*