Imaging-therapy computed tomography with quasi-monochromatic X-rays.
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.
Jost
Gregor
G
Bayer Schering Pharma AG, Contrast Media Research, Muellerstrasse 178, 13353 Berlin, Germany. gregor.jost@bayerhealthcare.com
Golfier
Sven
S
Lawaczeck
Ruediger
R
Weinmann
Hanns-Joachim
HJ
Gerlach
Martin
M
Cibik
Levent
L
Krumrey
Michael
M
Fratzscher
Daniel
D
Rabe
Johannis
J
Arkadiev
Vladimir
V
Haschke
Michael
M
Langhoff
Norbert
N
Wedell
Reiner
R
Luedemann
Lutz
L
Wust
Peter
P
Pietsch
Hubertus
H
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*