Spectra of clinical CT scanners using a portable Compton spectrometer

Purpose: Spectral information of the output of x‐ray tubes in (dual source) computer tomography (CT) scanners can be used to improve the conversion of CT numbers to proton stopping power and can be used to advantage in CT scanner quality assurance. The purpose of this study is to design, validate, a...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2015-04, Vol.42 (4), p.1884-1894
Main Authors: Duisterwinkel, H. A., Abbema, J. K., Goethem, M. J., Kawachimaru, R., Paganini, L., Graaf, E. R., Brandenburg, S.
Format: Article
Language:English
Subjects:
07 ISOTOPES AND RADIATION SOURCES
60 APPLIED LIFE SCIENCES
Algorithms
Biological material, e.g. blood, urine
Haemocytometers
COMPARATIVE EVALUATIONS
Compton effect
Compton scattering
Compton spectrometer
COMPTON SPECTROMETERS
Computed tomography
Computer Simulation
Computerised tomographs
computerised tomography
COMPUTERIZED SIMULATION
COMPUTERIZED TOMOGRAPHY
Devices sensitive to very short wavelength, e.g. x‐rays, gamma‐rays or corpuscular radiation
Digital computing or data processing equipment or methods, specially adapted for specific applications
dual energy CT
Equipment Design
Fluorescence
Humans
Image data processing or generation, in general
image reconstruction
instrument validation
medical image processing
MONTE CARLO METHOD
Monte Carlo methods
Monte Carlo simulations
Multislice
Photon scattering
Photons
QUALITY ASSURANCE
quality assurance CT scanners
Radiation Protection - instrumentation
Radiation Protection - methods
Radiometry - instrumentation
Radiometry - methods
Reconstruction
SHIELDING MATERIALS
Spectrum Analysis - instrumentation
Spectrum Analysis - methods
spectrum reconstruction
STOPPING POWER
Tomography Scanners, X-Ray Computed
Transforming x‐rays
Vacuum tubes
X-RAY SPECTRA
X-RAY TUBES
X-Rays
X‐ray detectors
X‐ray effects
X‐ray scattering
X‐ray spectrometers
X‐ray technique
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Summary:Purpose: Spectral information of the output of x‐ray tubes in (dual source) computer tomography (CT) scanners can be used to improve the conversion of CT numbers to proton stopping power and can be used to advantage in CT scanner quality assurance. The purpose of this study is to design, validate, and apply a compact portable Compton spectrometer that was constructed to accurately measure x‐ray spectra of CT scanners. Methods: In the design of the Compton spectrometer, the shielding materials were carefully chosen and positioned to reduce background by x‐ray fluorescence from the materials used. The spectrum of Compton scattered x‐rays alters from the original source spectrum due to various physical processes. Reconstruction of the original x‐ray spectrum from the Compton scattered spectrum is based on Monte Carlo simulations of the processes involved. This reconstruction is validated by comparing directly and indirectly measured spectra of a mobile x‐ray tube. The Compton spectrometer is assessed in a clinical setting by measuring x‐ray spectra at various tube voltages of three different medical CT scanner x‐ray tubes. Results: The directly and indirectly measured spectra are in good agreement (their ratio being 0.99) thereby validating the reconstruction method. The measured spectra of the medical CT scanners are consistent with theoretical spectra and spectra obtained from the x‐ray tube manufacturer. Conclusions: A Compton spectrometer has been successfully designed, constructed, validated, and applied in the measurement of x‐ray spectra of CT scanners. These measurements show that our compact Compton spectrometer can be rapidly set‐up using the alignment lasers of the CT scanner, thereby enabling its use in commissioning, troubleshooting, and, e.g., annual performance check‐ups of CT scanners.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.4915497