Dual energy x-ray detector

1. A dual energy x-ray imaging detector, comprising:

an array of x-ray detector elements configured to detect x-rays in an x-ray imaging system, each x-ray detector element configured to measure x-ray attenuation by an object at two different x-ray energies so that x-ray images of the object can be generated at the two different energies;

wherein each x-ray detector element includes:

a first scintillator element configured to convert x-rays from the x-ray source that have traversed the object into light having a first wavelength;

a second scintillator element configured to convert x-rays from the x-ray source that have traversed the object and that have passed through the first scintillator element into light having a second wavelength;

a first optical sensor configured to detect the light from the first and second scintillator elements, the first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

a second optical sensor configured to detect the light from the first and second scintillator elements, the second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first scintillator element comprises gadolinium oxisulfite ceramic, and has a thickness of between about 0.03 mm and about 0.06 mm; and

wherein the second scintillator element comprises single crystal cadmium tungstate, and has a thickness of between about 2 mm and about 3 mm.

2. The x-ray detector of claim 1 , wherein the first optical sensor includes a 600 nm highpass filter, and wherein the second optical sensor includes a 600 nm lowpass filter.

3. The x-ray detector of claim 1 , wherein the first sensor includes a 450 nm lowpass filter, and the second sensor includes a 550 nm highpass filter.

4. The x-ray detector of claim 1 , wherein at least one of the optical sensors comprises a silicon p-i-n photodiode.

5. The x-ray detector of claim 1 , wherein a total thickness of the scintillator elements is between 1.0 mm and 10.0 mm.

6. The x-ray detector of claim 1 , further comprising an optical filter located between the first scintillator and the second scintillator.

7. The x-ray detector of claim 1 , wherein the array comprises a two-dimensional array that includes multiple rows.

8. The x-ray detector of claim 1 , wherein each x-ray detector element further includes a light reflector, the light reflector disposed between the x-ray source and the scintillators and on the sides of the scintillators, the light reflector configured to increase light collection in the optical sensors.

9. The x-ray detector of claim 1 , wherein the first and second optical sensors are positioned side-by-side on a single silicon chip.

10. A dual energy x-ray imaging detector, comprising:

an array of x-ray detector elements configured to detect x-rays in an x-ray imaging system, each x-ray detector element configured to measure x-ray attenuation by an object at two different x-ray energies so that x-ray images of the object can be generated at the two different energies;

wherein each x-ray detector element includes:

a first scintillator element configured to convert x-rays from the x-ray source that have traversed the object into light having a first wavelength;

a second scintillator element configured to convert x-rays from the x-ray source that have traversed the object and that have passed through the first scintillator element into light having a second wavelength;

a first optical sensor configured to detect the light from the first and second scintillator elements, the first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

a second optical sensor configured to detect the light from the first and second scintillator elements, the second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first scintillator element comprises CsI-Na, and has a thickness of about 0.5 mm and about 2.0 mm; and

wherein the second scintillator element comprises CsI-Tl, and has a thickness of between about 3 mm and about 5 mm.

11. A dual enemy x-ray imaging detector, comprising:

an array of x-ray detector elements configured to detect x-rays in an x-ray imaging system, each x-ray detector element configured to measure x-ray attenuation by an object at two different x-ray energies so that x-ray images of the object can be generated at the two different energies;

wherein each x-ray detector element includes:

a first scintillator element configured to convert x-rays from the x-ray source that have traversed the object into light having a first wavelength;

a second scintillator element configured to convert x-rays from the x-ray source that have traversed the object and that have passed through the first scintillator element into light having a second wavelength;

a first optical sensor configured to detect the light from the first and second scintillator elements, the first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

a second optical sensor configured to detect the light from the first and second scintillator elements, the second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first scintillator element comprises zinc selenide (ZnSe), and has a thickness of between about 0.03 mm and about 1 mm; and

wherein the second scintillator element comprises single crystal cadmium tungstate, and has a thickness of between about 2 mm and about 3 mm.

12. The x-ray detector of claim 11 , wherein the first optical sensor includes a 600 nm highpass filter, and wherein the second optical sensor includes a 600 nm lowpass filter.

13. A method of generating x-ray images of an object at two different energies, the method comprising:

converting x-rays that are generated by an x-ray source and that have passed through an object that includes the material, into light having a first wavelength, using a first scintillator element;

converting x-rays from the x-ray source that have passed through the object and that have passed through the first scintillator element into light having a second wavelength, using a second scintillator element;

detecting light from the first and the second scintillator elements, with a first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

detecting light from the first and second scintillator elements, with a second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first and second scintillator elements and the first and second optical sensors are included in one x-ray detector element in an array of x-ray detector elements for an x-ray imaging system;

wherein the first scintillator element comprises gadolinium oxisulfite ceramic, and has a thickness of between about 0.03 mm and about 0.06 mm; and

wherein the second scintillator element comprises single crystal cadmium tungstate, and has a thickness of between about 2 mm and about 3 mm.

14. The method of claim 13 , further comprising filtering the light from the first and the second scintillator elements with a lowpass filter before detecting said light with the first optical sensor.

15. The method of claim 13 , further comprising filtering the light from the first and the second scintillator elements with a highpass filter before detecting said light with the second optical sensor.

16. The method of claim 13 , wherein at least one of the optical sensors comprises a silicon p-i-n photodiode.

17. A method of generating x-ray images of an object at two different energies, the method comprising:

converting x-rays that are generated by an x-ray source and that have passed through an object that includes the material, into light having a first wavelength, using a first scintillator element;

converting x-rays from the x-ray source that have passed through the object and that have passed through the first scintillator element into light having a second wavelength, using a second scintillator element;

detecting light from the first and the second scintillator elements, with a first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

detecting light from the first and second scintillator elements, with a second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first and second scintillator elements and the first and second optical sensors are included in one x-ray detector element in an array of x-ray detector elements for an x-ray imaging system;

wherein the first scintillator element comprises CsI-Na, and has a thickness of about 0.5 mm and about 2.0 mm; and

wherein the second scintillator element comprises CsI-Tl, and has a thickness of between about 3 mm and about 5 mm.

18. A method of generating x-ray images of an object at two different energies, the method comprising:

converting x-rays that are generated by an x-ray source and that have passed through an object that includes the material, into light having a first wavelength, using a first scintillator element;

converting x-rays from the x-ray source that have passed through the object and that have passed through the first scintillator element into light having a second wavelength, using a second scintillator element;

detecting light from the first and the second scintillator elements, with a first optical sensor having a spectral sensitivity substantially matched to the first wavelength; and

detecting light from the first and second scintillator elements, with a second optical sensor having a spectral sensitivity substantially matched to the second wavelength;

wherein the first and second scintillator elements and the first and second optical sensors are included in one x-ray detector element in an array of x-ray detector elements for an x-ray imaging system;

wherein the first scintillator element comprises zinc selenide (ZnSe), and has a thickness of between about 0.03 mm and about 1 mm; and

wherein the second scintillator element comprises single crystal cadmium tungstate, and has a thickness of between about 2 mm and about 3 mm.