X-ray detector, imaging apparatus and calibration method

Patent metadata

Field	Value
Publication number	US-10001567-B2
Application number	US-201515114444-A
Country	US
Kind code	B2
Filing date	Dec 9, 2015
Priority date	Dec 11, 2014
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

An X-ray detector comprises a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer, wherein said incident radiation is x-ray radiation emitted by an x-ray source or light omitted by at least one light source. An evaluation unit calculates evaluation signals per pixel or group of pixels from first electrical measurement signals generated when light from said at least one light source at a first intensity is coupled into the semiconductor layer, and second electrical measurement signals generated when light from said at least one light source at a second intensity is coupled into the semiconductor layer. A detection unit determines detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and a calibration unit calibrates the detection unit on the basis of the evaluation signals.

First claim

The invention claimed is:

1. An X-ray detector comprising:
a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer, wherein said incident radiation is x-ray radiation emitted by an x-ray source or light emitted by at least one light source, said light having an energy above the band gap energy of the semiconductor layer for simulation of incident x-ray quanta,
an evaluation unit for calculating evaluation signals per pixel or group of pixels from first electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a first intensity is coupled into the semiconductor layer and second electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a second intensity is coupled into the semiconductor layer, wherein said evaluation unit is configured to detect per pixel or group of pixels a noise peak in said first and second electrical measurement signals and to determine offset and gain per pixel or group of pixels from the detected noise peaks,
a detection unit for determining detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and
a calibration unit for calibrating the detection unit on the basis of the evaluation signals.

2. The X-ray detector as claimed in claim 1 ,
wherein said evaluation unit is configured to perform a threshold scan to obtain said first and second electrical measurement signals.

3. The X-ray detector as claimed in claim 2 ,
wherein said evaluation unit is configured to determine the offset per pixel or group of pixels from an absolute threshold value of the noise peak in a threshold scan performed to obtain said first electrical measurement signals.

4. The X-ray detector as claimed in claim 2 ,
wherein said evaluation unit is configured to determine the gain per pixel or group of pixels from an absolute difference in threshold values of the noise peak in a first threshold scan performed to obtain said first electrical measurement signals and a second threshold scan performed to obtain said second electrical measurement signals and from the intensity level of the light coupled into the semiconductor layer during the generation of the first and second electrical measurement signals.

5. The X-ray detector as claimed in claim 1 ,
wherein said evaluation unit is configured to calculate evaluation signals per pixel or group of pixels from at least three electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at three different intensities is coupled into the semiconductor layer.

6. The X-ray detection apparatus comprising:
an x-ray detector as claimed in claim 1 and
at least one light source for coupling light into the semiconductor layer, wherein the generated light, for the simulation of incident x-ray quanta, has an energy above the band gap energy of the semiconductor layer.

7. The X-ray detection apparatus as claimed in claim 6 ,
comprising a single light source for coupling light into the semiconductor layer.

8. The X-ray detection apparatus as claimed in claim 6 ,
comprising a plurality of light sources, including a single light source per pixel or group of pixels, for coupling light into the semiconductor layer.

9. The X-ray detection apparatus as claimed in claim 6 ,
further comprising at least one of beam widening optics for beam widening of the light emitted from said at least one light source onto the semiconductor layer or beam guiding optics for beam guiding of the light emitted from said at least one light source onto the semiconductor layer.

10. The X-ray detection apparatus as claimed in claim 9 ,
comprising one or more removable or displaceable mirrors, fiber optics, diffraction gratings for diffracting the light onto the pixels of the semiconductor layer and/or lenses.

11. The X-ray detection apparatus as claimed in claim 6 ,
wherein said at least one light source is arranged outside of the path of the x-ray radiation.

12. The X-ray detection apparatus as claimed in claim 6 ,
wherein said at least one light source is configured for pulsed or continuous emission of light.

13. An imaging apparatus comprising:
a radiation source for emitting radiation through an imaging area,
an x-ray detection apparatus as claimed in claim 6 for detecting radiation from said imaging area,
a gantry to which at least said x-ray detector is mounted and which allows rotation of said x-ray detector around said imaging area, and
a controller for controlling said x-ray detection apparatus to detect radiation at a plurality of projection positions during rotation around said imaging area.

14. A calibration method for calibrating an x-ray detector comprising a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer and at least one light source for coupling light into the semiconductor layer, wherein the generated light, for simulation of incident x-ray quanta, has an energy above the band gap energy of the semiconductor layer, said method comprising:
acquiring first electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a first intensity is coupled into the semiconductor layer,
acquiring second electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a second intensity is coupled into the semiconductor layer,
calculating evaluation signals per pixel or group of pixels from the acquired first electrical measurement signals and the acquired second electrical measurement signals by detecting per pixel or group of pixels a noise peak in said first and second electrical measurement signals and determining offset and gain per pixel or group of pixels from the detected noise peaks,
determining detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and
calibrating the x-ray detector on the basis of the evaluation signals.

15. A non-transitory computer readable medium encoded with a computer program comprising program code for causing a computer to control an imaging apparatus to carry out the steps of the method as claimed in claim 14 when said computer program is carried out on the computer.

Assignees

• Koninklijke Philips Nv

Inventors

• Roessl Ewald
• Daerr Heiner

Classifications

• G01T1/24 Primary

  with semiconductor detectors · CPC title

• H05G1/08

  Electrical details · CPC title

• G01T7/005

  calibration techniques (stabilization of spectrometer G01T1/40) · CPC title

• A61B6/585

  Calibration of detector units · CPC title

• H01J35/02

  Details · CPC title