Radiographic imaging apparatus and method

Patent metadata

Field	Value
Publication number	US-9504438-B2
Application number	US-201314434209-A
Country	US
Kind code	B2
Filing date	Oct 3, 2013
Priority date	Oct 12, 2012
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

The present invention relates to a radiographic imaging apparatus and a corresponding radiographic imaging method. The proposed apparatus comprises an X-ray source ( 20, 108 ) and a photon counting X-ray detector ( 40, 110 ). The X-ray source ( 20, 108 ) comprises a rotary X-ray anode ( 23 ) having a number of radial slits and a target layer provided on a surface of said rotary X-ray anode in between said radial slits for emitting X-ray radiation when hit by said electron beam. The said photon counting X-ray detector ( 40, 110 ) comprises a persistent current sensing and correction unit ( 70 ) for sensing a persistent output current in a blanking interval during which no X-ray radiation is emitted by said X-ray source and for using the sensed persistent output current to correct a detector signal in a subsequent measurement interval during which X-ray radiation is emitted by said X-ray source.

First claim

The invention claimed is:

1. A radiographic imaging apparatus comprising an X-ray source for projecting X-ray radiation into an examination region and a photon counting X-ray detector for receiving X-ray radiation after passing through said examination region and converting the received X-ray radiation into detector signals,
wherein said X-ray source comprises
a cathode for emitting an electron beam,
a rotary X-ray anode having a number of radial slits and a target layer provided on a surface of said rotary X-ray anode in between said radial slits for emitting X-ray radiation when hit by said electron beam, and
a drive unit for rotating said X-ray anode,

and
wherein said photon counting X-ray detector comprises
a direct conversion X-ray detection unit for receiving the X-ray radiation and outputting an electrical signal,
a photon counting unit for generating, from said electrical signal, said detector signal representing the number of photons of the received X-ray radiation, and
a persistent current sensing and correction unit for sensing a persistent output current in a blanking interval during which no X-ray radiation is emitted by said X-ray source and for using the sensed persistent output current to correct a detector signal generated by said photon counting unit in a subsequent measurement interval during which X-ray radiation is emitted by said X-ray source.

2. A radiographic imaging apparatus as claimed in claim 1 , wherein the width of the radial slits, of the rotary anode is configured such that during a blanking interval the persistent output current can be completely sensed by said persistent current sensing and correction unit.

3. A radiographic imaging apparatus as claimed in claim 1 , wherein the radial slits of the rotary anode have a minimum slit width of FS+(R×Ω×T), wherein FS is the focal spot size on the anode, R is the radius of the focal track on the rotary anode, Ω is the angular speed of the rotary anode and T is the minimum time required for completely sensing the persistent output current by said persistent current sensing and correction unit.

4. A radiographic imaging apparatus as claimed in claim 3 , wherein R is in the range from 5 cm to 35 cm, Ω is in the range from 2π×50 Hz to 2π×400 Hz, and T is in the range from 0.1 μsec to 100 μsec.

5. A radiographic imaging apparatus as claimed in claim 1 , wherein said the angular width of a slit is in the range from 0.5 mm to 3 mm.

6. A radiographic imaging apparatus as claimed in claim 1 , wherein said persistent current sensing and correction unit comprises
an amplifier coupled between the output of said direct conversion X-ray detection unit and the input of said photon counting unit for amplifying said electrical signal, and
a sample and hold unit for receiving said amplified electrical signal and generating, during the blanking interval, a compensation signal coupled to the output of said direct conversion X-ray detection unit for dynamically adjusting the electrical signal to compensate the persistent output current.

7. A radiographic imaging apparatus as claimed in claim 6 , wherein said sample and hold unit comprises a switch for enabling a dynamic adjustment of the electrical signal during a blanking interval by use of the dynamically generated compensation signal and for keeping the compensation signal constant during a subsequent measurement interval.

8. A radiographic imaging apparatus as claimed in claim 7 , wherein said switch is controlled by a blanking signal to be synchronously with the blanking interval switched on and off.

9. A radiographic imaging apparatus as claimed in claim 7 , wherein said switch is controlled by a blanking signal to be asynchronously with the measurement intervals of the photon counting X-ray detector and wherein a reference measurement is used to correct for X-ray flux variation caused by flux blanking.

10. A radiographic imaging apparatus as claimed in claim 7 , wherein said switch is controlled by a blanking signal to be synchronously with the measurement intervals of the photon counting X-ray detector and between two successive measurement intervals.

11. A radiographic imaging method comprising
projecting X-ray radiation into an examination region by use of an X-ray source comprising a cathode for emitting an electron beam, a rotary X-ray anode having a number of radial slits and a target layer provided on a surface of said rotary X-ray anode in between said radial slits for emitting X-ray radiation when hit by said electron beam, and a drive unit for rotating said X-ray anode,
receiving X-ray radiation after passing through said examination region by use of a direct conversion X-ray detection unit,
outputting an electrical signal from said direct conversion X-ray detection unit,
converting the electrical signal into a detector signal representing the number of photons of the received X-ray radiation.
sensing the persistent output current of the photon counting unit in a blanking interval during which no X-ray radiation is emitted by said X-ray source, and
using the sensed persistent output current to correct a detector signal generated by said photon counting unit in a subsequent measurement interval during which X-ray radiation is emitted by said X-ray source.

Assignees

• Koninklijke Philips Nv
• Philips Deutschland Gmbh

Inventors

• Proksa Roland

Classifications

• G21K1/043

  changing time structure of beams by mechanical means, e.g. choppers, spinning filter wheels · CPC title

• A61B6/54 Primary

  Control of apparatus or devices for radiation diagnosis · CPC title

• H01J2235/086

  Target geometry · CPC title

• G01T1/24 Primary

  with semiconductor detectors · CPC title

• A61B6/42

  Arrangements for detecting radiation specially adapted for radiation diagnosis · CPC title