X-ray diffraction and computed tomography
An imaging system combines CT and XRD measurements, both measuring the XRD diffraction and the absorption as a function of energy. A goniometer 2 , source 4 and two dimensional detector 10 may be used. Embodiments use relatively soft X-rays in the 5-25 keV range. An integrated mounting unit to mount the sample 8 close to detector 10 is also described.
1. A dual mode X-ray diffraction and computed tomography imaging system, comprising:
an X-ray source for emitting an X-ray beam;
a two-dimensional X-ray detector;
a sample position;
a goniometer for positioning the X-ray source, X-ray detector and a sample at the sample position relative to one another; and
a computer arranged to process the input from the 2D detector and output information about the sample based on the input from the 2D detector and the relative positions of X-ray source, X-ray detector and sample;
wherein the computer positions the X-ray source, X-ray detector and sample to operate in an X-ray diffraction, XRD, mode carrying out angle dispersive X-ray diffraction on the sample by measuring the X-ray diffraction as a function of diffraction angle 2θ using the X-ray detector; and
the computer positions the X-ray source, X-ray detector and sample to operate in a computed tomography, CT, mode to measure absorption of a sample as a function of position across the sample with the two-dimensional X-ray detector;
wherein the imaging system operates in dual XRD mode and CT mode; and
wherein the X-ray source is a source that emits X-rays having at least 30% of the total emitted X-ray intensity in at least one X-ray line in an energy band in the range 4.5 keV to 25 keV.
2. An imaging system according to claim 1 , wherein the X-ray source uses a Cr, Co, Cu, Mo or Ag target.
3. An imaging system according to claim 1 wherein the X-ray detector is a two dimensional photon counting X-ray detector.
4. An imaging system according to claim 1 , wherein the imaging system is arranged to operate in the CT mode to capture a plurality of absorption measurements of the absorption of the sample as a function of position across the sample by rotating the sample with respect to the source and detector, and to combine the plurality of measured absorption measurements to produce a CT image.
5. An imaging system according to claim 1 further comprising an integrated unit comprising a rotary sample mount for mounting the sample within 5 cm of the detector.
6. An imaging system according to claim 5 wherein the integrated unit further comprises a rotary drive connected to the sample mount for rotating the rotary sample mount to a plurality of different orientations for a CT measurement in the CT mode.
7. An imaging system according to claim 1 further comprising a beam conditioner arranged adjacent to the X-ray source, the beam conditioner being a pinhole aperture, a slit or an X-ray mirror.
8. An imaging system according to claim 1 further comprising a monochromator.
9. An imaging system according to claim 1 , further comprising a beam stop placed in the direct line of the X-ray beam after the sample in the XRD mode, the beam stop being removed in the CT mode.
10. A method of operating an imaging system, comprising:
positioning an X-ray source, X-ray detector and a sample at a sample position relative to one another;
emitting an X-ray beam from the X-ray source towards the sample;
detecting the beam after interaction with a sample using a two-dimensional X-ray detector;
the method including processing the input from the 2D detector and output information about the sample based on the input from the 2D detector and the relative positions of X-ray source, X-ray detector and sample; and
operating the imaging system in an X-ray diffraction, XRD, mode carrying out angle dispersive X-ray diffraction on the sample by measuring the X-ray diffraction as a function of diffraction angle 2θ using the X-ray detector; and
operating the imaging system in a computed tomography, CT, mode measuring absorption of a sample as a function of position across the sample with the two-dimensional X-ray detector;
wherein the imaging system is operated in dual XRD mode and CT mode; and
wherein the X-ray source is a source that emits X-rays having at least 30% of the total emitted X-ray intensity in at least one X-ray line in an energy band in the range 4.5 keV to 25 keV.
11. A method according to claim 10 , wherein the X-rays are emitted by a Cr, Co, Cu, Mo or Ag target.
12. A method according to claim 10 including detecting the beam using a two dimensional photon counting X-ray detector.
13. A method according to claim 10 comprising operating in the CT mode by capturing a plurality of absorption measurements of the absorption of the sample as a function of position across the sample by rotating the sample with respect to the source and detector, and combining the plurality of measured absorption measurements to produce a CT image.
14. A method according to claim 13 , further comprising mounting the sample on an integrated unit comprising the two-dimensional X-ray detector and a rotary sample mount, mounting the sample within 5 cm of the detector; and
rotating the sample on the rotary sample mount to obtain the plurality of absorption measurements.