Spectra of clinical CT scanners using a portable Compton spectrometer

Abstract

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.

A robust empirical parametrization of proton stopping power using dual energy CT

“…29 Comparison could also have been made to the method presented by Yang et al 4 However, that method requires full knowledge of the CT energy spectrum, which would make it cumbersome for clinical use. The CT energy spectrum can be measured by, e.g., a Compton spectrometer, see Duisterwinkel et al, 26 or it can be approximated by calculation, e.g., using ImaSim. [22][23][24][25] But the results for the SPR estimations are suspected to be dependent on the accuracy of the energy spectra determination.…”

“…We generated energy spectra approximating the 80, Sn140 and 120 kVp energy spectra of the Flash CT scanner, where Sn denotes that an additional tin filtration of 0.4 mm was used. As input parameters to ImaSim we used an anode angle of 8 • , and filtrated all three energy spectra by 3 mm aluminium, 0.9 mm titanium and 500 mm air (as stated for the Flash CT scanner by Duisterwinkel et al 26 ) and 160 mm F. 1.…”

Caracterização de feixes de TC utilizando Espectrometria Compton

“…Vieira et al 6 descreveram os princípios de um espectrômetro Compton portátil, usando um espalhador de PMMA, relatando aplicações preliminares em laboratório para feixes de mamografia e radiologia. Duisterwinkel et al 7 , além disso, construíram um espectrômetro portátil e aplicaram-no em TC.…”

A unified material decomposition framework for quantitative dual‐ and triple‐energy CT imaging

“…There are a lot of methods that can be employed to obtain the spectrum. [39][40][41][42][43] In this study, we employ an indirect transmission measurement (ITM) method to estimate the triple-energy spectra. 39 Specifically, the energy spectrum is expressed by a set of model spectra.…”