SPECTRALLY RESOLVING X-RAY IMAGING DEVICE

• US 20100008558A1
• Filed: 12/11/2007
• Published: 01/14/2010
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Vogtmeier, Gereon, Loef, Christoph, Baeumer, Christian, Scheel, Thomas, Steadman Booker, Roger
• Granted Patent: US 8,515,147 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/405 Source units specially adapted to modify characteristics of the beam during the data acquisition process A61B6/4021, A61B6/4035 take precedence

Abstract

The invention relates to an X-ray imaging device (100), particularly a Spectral-CT scanner, that comprises an X-ray source (10) for generating X-radiation with an energy spectrum (P(E,t)) which varies continuously during an observation period (T). In a preferred embodiment, the radiation (X) is attenuated in an object (1) according to an energy-dependent attenuation coefficient μ(E,r), the transmitted radiation is measured by sensor units (22) of a detector (20, 30), and the resulting measurement signal (i(t)) is sampled and A/D converted. This is preferably done by an oversampling A/D converter, for example a ΣΔ-ADC. The tube voltage (U(t)) that drives the X-ray source is sampled with high frequency. In an evaluation system (50), these sampled measurement values can be associated with corresponding effective energy spectra (Φ(E)) to determine the energy dependent attenuation coefficient μ(E,r).

Claims

1. An X-ray imaging device, particularly a CT scanner, comprising

a) an X-ray source for emitting X-rays with an energy spectrum that varies continuously during a given observation period;

b) a detector for producing a plurality of m≧

2 radiation sampling values that are indicative of the amount of X-radiation measured by a sensor unit of the detector during different sampling intervals within the observation period;

c) a spectrum estimation unit for determining the effective energy spectra of the X-ray source that are associated to the m sampling intervals.

2. The X-ray imaging device according to claim 1, wherein the X-ray source comprises a filter element with time-variable spectral characteristics.

3. The X-ray imaging device according to claim 1, wherein the X-ray source comprises an X-ray tube and an associated generator for supplying a periodic tube voltage to the X-ray tube, preferably a sinusoid tube voltage.

4. The X-ray imaging device according to claim 3, wherein it comprises a voltage sensor unit for measuring the tube voltage.

5. The X-ray imaging device according to claim 4, wherein voltage sensor unit comprises a voltage sampling unit for sampling voltage values during the sampling intervals.

6. The X-ray imaging device according to claim 5, wherein the spectrum estimation unit determines the effective energy spectra from model spectra, which are given for various tube voltages.

7. The X-ray imaging device according to claim 1, wherein the detector comprises a radiation sampling unit for sampling the sampling values from a continuous measurement signal according to an associated weighting function.

8. The X-ray imaging device according to claim 6, wherein the spectrum estimation unit determines the effective energy spectra according to the weighting function of the radiation sampling unit.

9. The X-ray imaging device according to claim 5, wherein the voltage sampling unit and/or the radiation sampling unit comprises an oversampling A/D-converter, particularly a Σ

Δ

-ADC.

10. The X-ray imaging device according to claim 5, wherein the voltage sampling unit and/or the radiation sampling unit comprises a filter unit for generating m data streams composed of sampling values that belong to analogous sampling intervals of different observation periods.

11. The X-ray imaging device according to claim 1, wherein it comprises a spectral discrimination module for determining the line integrals

$A_j={\int }_{}^{}$

L 

a j 

( r _ ) ·





r _

for a model function

$\mathrm{\mu <br><br>}<br><br>\left(E,\underset{\_}{r}\right)=\stackrel{}{\underset{j}{\sum <br><br>}}<br><br>f_j<br><br>\left(E\right)·<br><br>a_j<br><br>\left(\underset{\_}{r}\right)$

of the attenuation coefficient in an object located in the X-ray path L between X-ray source and detector, wherein E is the X-ray photon energy, r is the location inside the object, and f_j are given functions.

12. The X-ray imaging device according to claim 1, wherein it comprises a reconstruction module for calculating the attenuation coefficient μ

in an object located in the X-ray path between X-ray source and detector from X-ray projections of this object taken from different projection directions.

13. A method for the generation of spectrally resolved X-ray images of an object, comprising the steps of

a) emitting X-rays with an energy spectrum that varies continuously during a given observation period;

b) producing a plurality of m≧

2 radiation sampling values that are indicative of the amount of X-radiation measured in a given measurement region during different sampling intervals within the observation period;

c) estimating the effective energy spectra of the emitted X-rays that are associated to said sampling intervals.