Dual-energy scanning-based detection of ionizing radiation

• US 7,027,561 B2
• Filed: 05/21/2003
• Issued: 04/11/2006
• Est. Priority Date: 04/16/2003
• Status: Expired due to Term

• Current Assignee: Xcounter AB (Varex Imaging Corporation)
• Original Assignee: Xcounter AB (Varex Imaging Corporation)
• Inventors: Ullberg, Christer, Francke, Tom
• Primary Examiner(s): Church, Craig E.
• Assistant Examiner(s): Artman, Thomas R.
• Application Number:
  US10/442,208
• Publication Number:
  US 20040234031A1
• Time in Patent Office: 1,056 Days
• Field of Search: 378/5, 378/54, 378/146, 378/157, 378/158, 378/55
• US Class Current: 378/146
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4014 arranged in multiple source-detector units
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• 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

A dual-energy scanning-based radiation detecting apparatus comprises a line detector; a device for scanning said line detector across an object while said line detector is exposed to an ionizing radiation beam, which has impinged on said object, to thereby record a plurality of line images of said object; a filter device arranged in the path of said ionizing radiation beam upstream of said object to filtrate said ionizing radiation beam, the filter device being capable of operating in two operation modes having different filter characteristics; and a control device for altering operation mode of the filter device subsequent to at least every second of said line images being recorded.

Claims

1. A dual-energy scanning-based radiation detecting apparatus comprising:

a line detector;

a device for scanning said line detector across an object to be examined while said line detector is exposed to an ionizing radiation beam, which has impinged on said object, to thereby record a plurality of line images of said object;

a filter device arranged in the path of said ionizing radiation beam upstream of said object to filtrate said ionizing radiation beam, the filter device being capable of operating in two operation modes having different filter characteristics; and

a control device for altering operation mode of the filter device subsequent to at least every second of said line images being recorded, wherein

said device for scanning said line detector across said object is adapted to scan said line detector in stepwise movements and said line detector is adapted to be exposed and read out when being still between each of said stepwise movements to thereby record said plurality of line images of said object; and

said control device is adapted to alter the operation mode of said filter device once while said line detector is still between each of said stepwise movements at each to each one of said line images being recorded and said line detector is adapted, when being still between each of said stepwise movements, to be exposed and read out once before and once after said operation mode alteration performed while said line detector is still.

2. The apparatus of claim 1 wherein said filter device comprises at least two filter sections which sections are capable of being arranged, one at a time, in the path of said radiation beam to form said two operation modes.

3. The apparatus of claim 2 wherein said control device comprises a moving mechanism for inserting said at least two filter sections, one at a time, in the path of said radiation beam.

4. The apparatus of claim 1 wherein said line detector is a gaseous-based ionization detector, wherein electrons freed as a result of ionization by said ionizing radiation beam are accelerated in a direction essentially perpendicular to the direction of said ionizing radiation beam.

5. The apparatus of claim 1 wherein said line detector is any of a scintillator-based detector, a PIN-diode array, a TFT array, a CCD array, a liquid-based detector, and a solid-state detector.

6. The apparatus of claim 1 comprising an X-ray tube for producing said ionizing radiation beam, said X-ray tube having an operating voltage, which is kept essentially constant during the scanning of said line detector across the object to be examined.

7. A dual-energy scanning-based radiation detecting apparatus comprising:

a plurality of stacked line detectors;

a device provided for scanning said plurality of stacked line detectors across an object to be examined substantially in a linear path parallel with the stack of line detectors while each of said plurality of stacked line detectors is exposed to an ionizing radiation beam, which has been transmitted through said object, to thereby record a plurality of line images of radiation as transmitted through said object;

a filter device arranged in the path of said ionizing radiation beams upstream of said object to filtrate said ionizing radiation beams, the filter device comprising an array of filter sections aligned with said ionizing radiation beams during scanning so that each of said ionizing radiation beams will have been filtered by a respective one of said filter sections when impinging on said object, where every second filter section in the array has a first filter characteristic and the other filter sections in the array have each a second filter characteristic; and

said device for scanning said plurality of stacked line detector scans a distance corresponding to two times the distance between two adjacent line detectors of said plurality of stacked line detectors to create two two-dimensional images of radiation as transmitted through said object, one two-dimensional image of radiation which has been filtered by a filter section having the first filter characteristic, and one two-dimensional image of radiation which has been filtered by a filter section having the second filter characteristic, wherein

the number of said plurality of stacked line detectors is at least 10;

said at least 10 stacked line detectors are essentially evenly distributed over the entire two-dimensional images; and

said device for scanning said plurality of stacked line detectors scans a maximum distance corresponding to the width of the two-dimensional images divided by five to create said two-dimensional images of radiation.

8. The apparatus of claim 7 comprising an X-ray tube for producing said ionizing radiation beam, said X-ray tube having an operating voltage, which is kept essentially constant during the scanning of said plurality of stacked line detectors across the object to be examined.

9. The apparatus of claim 7 wherein each one of said plurality of stacked line detectors comprises multiple line detector units arranged in parallel.

10. The apparatus of claim 9 wherein said multiple line detector units are at least 4.

11. The apparatus of claim 10 wherein each one of said multiple line detector units is 40–

60 mm wide.

12. The apparatus of claim 10 wherein said multiple line detector units are arranged in a staggered manner.

13. A dual-energy scanning-based radiation detecting method comprising the steps of:

scanning a plurality of stacked line detectors across an object to be examined substantially in a linear path parallel with the stack of line detectors while each of said plurality of stacked line detectors is exposed to an ionizing radiation beam, which has been transmitted through said object, to thereby record a plurality of line images of radiation as transmitted through said object;

arranging a filter device in the path of said ionizing radiation beams upstream of said object to filtrate said ionizing radiation beams, the filter device comprising an array of filter sections; and

having said filter sections aligned with said ionizing radiation beams during scanning so that each of said ionizing radiation beams will have been filtered by a respective one of said filter sections when impinging on said object, where every second filter section in the array has a first filter characteristic and the other filter sections in the array have each a second filter characteristic;

wherein

said scanning said plurality of stacked line detector is performed a distance corresponding to two times the distance between two adjacent line detectors of said plurality of stacked line detectors to create two two-dimensional images of radiation as transmitted through said object, one two-dimensional image of radiation which has been filtered by a filter section having the first filter characteristic, and one two-dimensional image of radiation which has been filtered by a filter section having the second filter characteristic, wherein

the number of said plurality of stacked line detectors is at least 10;

said at least 10 stacked line detectors are essentially evenly distributed over the entire two-dimensional images; and

said scanning said plurality of stacked line detectors scans a maximum distance corresponding to the width of the two-dimensional images divided by five to create said two-dimensional images of radiation.

14. A dual-energy scanning-based radiation detecting apparatus comprising:

a plurality of stacked line detectors;

a device provided for scanning said plurality of stacked line detectors across an object to be examined while each of said plurality of stacked line detectors is exposed to an ionizing radiation beam, which has been transmitted through said object, to thereby record a plurality of line images of radiation as transmitted through said object;

a filter device comprising filter sections of two kinds having different filter characteristics alternately arranged in an array, wherein

the number of filter sections of each of the two kinds is higher than the number of said plurality of stacked line detectors;

the filter device is held still during scanning so that the filter sections of each of the two kinds are alternately arranged in the radiation paths of said ionizing radiation beams upstream of said object to filtrate said ionizing radiation beams; and

said device for scanning said plurality of stacked line detector scans a distance corresponding to the distance between two adjacent line detectors of said plurality of stacked line detectors to create two two-dimensional images of radiation as transmitted through said object, one two-dimensional image of radiation which has been filtered by a filter section having a first filter characteristic, and one two-dimensional image of radiation which has been filtered by a filter section having a second filter characteristic different from the first filter characteristic, wherein the number of the filter sections of the two kinds are adapted to the scanning step of said scanning so that each of said plurality of line detectors record line images of radiation, which has alternately passed through a filter section having the first filter characteristic and a filter section having the second filter characteristic.