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EP-4741810-A1 - DEVICE FOR CALIBRATING AN X-RAY SYSTEM, X-RAY APPARATUS AND METHOD FOR CALIBRATING AN X-RAY APPARATUS

EP4741810A1EP 4741810 A1EP4741810 A1EP 4741810A1EP-4741810-A1

Abstract

A device (100) for calibrating an X-ray system (200) with an X-ray source (210) and an X-ray detector (220), the calibration device (100) comprising a set of at least two X-ray absorptive elements (1, 2), each element (1, 2) extending in a longitudinal (LO) and in a lateral (LA) direction, is according to the invention characterized in that the device (100) is configured to enable adjustment of the position of each element (1, 2) along a closed curve ( C 1 , C 2 ) in a plane that extends transverse to the lateral direction (LA) and in parallel to the longitudinal direction (LO) so that elements (1, 2) in each of a first and a second subset (10, 20) of the set of elements (1, 2) are positioned with their longitudinal directions (LO) aligned in an alignment direction transverse to the curve ( C 1 , C 2 ) , and wherein a first total length in the longitudinal direction (LO) of the elements (1, 2) of the first subset (10) is different from a second total length in the longitudinal direction (LO) of the elements (1, 2) of the second subset (20).

Inventors

  • HOFFMANN, Benedikt

Assignees

  • Mettler-Toledo, LLC

Dates

Publication Date
20260513
Application Date
20241108

Claims (15)

  1. Device (100) for calibrating an X-ray system (200) with an X-ray source (210) and an X-ray detector (220), the calibration device (100) comprising a set of at least two X-ray absorptive elements (1, 2), each element (1, 2) extending in a longitudinal (LO) and in a lateral (LA) direction, characterized in that the device (100) is configured to enable adjustment of the position of each element (1, 2) along a closed curve ( C 1 , C 2 ) in a plane that extends transverse to the lateral direction (LA) and in parallel to the longitudinal direction (LO) so that elements (1, 2) in each of a first and a second subset (10, 20) of the set of elements (1, 2) are positioned with their longitudinal directions (LO) aligned in an alignment direction transverse to the curve ( C 1 , C 2 ), and wherein a first total length in the longitudinal direction (LO) of the elements (1, 2) of the first subset (10) is different from a second total length in the longitudinal direction (LO) of the elements (1, 2) of the second subset (20).
  2. Device (100) according to claim 1, wherein the curve ( C 1 , C 2 ) comprises a plurality of nested, crossing-free curves ( C 1 , C 2 ) in the plane that extends transverse to the lateral direction (LA) and in parallel to the longitudinal direction (LO), each element (1, 2) is associated with one curve ( C 1 , C 2 ) of the plurality of curves and the device (100) is configured to enable adjustment of the position of each element (1, 2) along the associated curve ( C 1 , C 2 ) independent of the position of the elements (1, 2) associated with the other curves ( C 1 , C 2 ) .
  3. Device (100) according to claim 2, wherein the curves ( C 1 , C 2 ) are concentric curves.
  4. Device (100) according to anyone of the preceding claims, wherein each of the curves ( C 1 , C 2 ) is circular.
  5. Device (100) according to anyone of the preceding claims, wherein at least two elements have a different longitudinal extension ( h 1 , h 3 , H 1 , H 2 , H 3 ).
  6. Device (100) according to anyone of the preceding claims, wherein the elements (1, 2) are separate elements (1, 2).
  7. Device (100) according to claim 6, wherein the device (100) is configured to enable adjustment of the position of the elements so as to form a passageway extending straightly across the curve(s) and having none of the elements positioned therein.
  8. Device (100) according to anyone of the preceding claims, wherein at least one of the first and second subsets (10, 20) comprises two elements (1, 2) associated with the same curve ( C 1 , C 2 ).
  9. Device (100) according to anyone of the preceding claims, wherein first and second lateral ends (3, 4) of the elements (1, 2) are mounted on first and second supports (30a, 30b) which are spaced apart in the lateral direction and the device is configured to enable independent rotation of the first and second supports (30a, 30b) around a common axis (A) extending in the lateral direction (LA) to thereby adjust the position of the elements (1, 2) along the closed curves(s) ( C 1 , C 2 ).
  10. Device (100) according to claim 2 and 9, wherein each of the first and second supports (30a, 30b) comprises a plurality of first and second segments (31a, 31b, 32a, 32b), respectively, and the device (100) is configured to enable rotation of the first and second segments (31a, 31b, 32a, 32b) relative to each other to thereby enable a relative movement of the elements (1, 2) associated with different curves ( C 1 , C 2 ).
  11. Device (100) according to anyone of the preceding claim, further comprising means for positioning (40) the calibration device (100) in the X-ray system (200) between the X-ray source (210) and the X-ray detector (220).
  12. Device (100) according to anyone of the preceding claims, further comprising a stationary X-ray absorber arranged within the curve(s) ( C 1 , C 2 ).
  13. An X-ray apparatus (1000) comprising an X-ray system (200) having an X-ray source (210) operative to emit an X-ray beam (211) in a radiation plane and an X-ray detector (220) arranged so as to receive the X-ray beam (211) and to output a signal in response to an amount of the received radiation, and a calibration device (100) according to anyone of the preceding claims, wherein the calibration device (100) is arranged between the X-ray source (210) and the X-ray detector (220) such that when the longitudinal direction of the elements (1, 2) of the first and second subsets (10, 20) are respectively aligned in the alignment direction, and the longitudinal extension of the elements (1, 2) of the first and second subsets (10, 20) is within the radiation plane, along a radiation path (R) of the X-ray beam.
  14. X-ray apparatus (1000) according to claim 13, wherein the X-ray source (210) is configured to emit a fan-shaped X-ray beam (211) in a radiation plane and the X-ray detector (220) comprises a line detector which is arranged in the radiation plane so as to receive the radiation beam (211).
  15. Method for calibrating an X-ray system of an X-ray apparatus (1000) according to claim 13 or 14, the method comprising the following steps: adjusting the positions of the elements (1,2) of the calibration device (100) in a first position so that the aligned longitudinal directions (LO) of the first subset (10) of elements (1, 2) are in the radiation plane; after adjusting the elements (1, 2) in the first position, operating the X-ray source (210) to thereby receive a first signal in response to a first amount of radiation which has passed through the elements (1, 2) of the first subset (10); adjusting the positions of the elements (1, 2) of the calibration device (100) in a second position so that the aligned longitudinal directions (LO) of the second subset (20) of elements (1, 2) are in the radiation plane; after adjusting the elements (1, 2) in the second position, operating the X-ray source (210) to thereby receive a second signal in response to a second amount of radiation which has passed through the elements (1, 2) of the second subset (20); calibrating the X-ray system (200) on the basis of the first and second signals.

Description

The present invention is related to a device for calibrating an X-ray system with an X-ray source and an X-ray detector, the calibration device comprising a set of at least two X-ray absorptive elements, each element extending in a longitudinal and in a lateral direction. The calibration device is in particular suitable for calibrating an X-ray system where an object to be inspected is transported along a transport path between the X-ray source and the X-ray detector. The invention is further related to an X-ray apparatus comprising the X-ray system and the calibration device and to a method for calibrating the X-ray apparatus. X-ray systems have many applications, including product inspection. In the food industry for example, the reliable detection of foreign objects in food products is of high importance. To this end, an object to be inspected may be transported along a transport path, for example, by a belt conveyor, between an X-ray source and an X-ray detector of an X-ray system. The X-ray source may create a fan-shaped beam, and the X-ray detector may be arranged so as to receive the X-ray beam and may be configured to output a signal in response to an amount of received radiation. In this way, a two-dimensional X-ray image of the object to be inspected may be created. In the example of food inspection mentioned above, the X-ray image may allow to infer the presence of foreign objects in a food product. X-ray systems are based on the physical phenomenon of X-ray absorption. For a monochromatic beam, the absorption is directly related to the distance x travelled by the X-rays in a homogenous body according to I = I0e-bx (Beer-Lambert law). Here, I0 is the intensity of the incident radiation, I is the intensity of the transmitted radiation and b is the coefficient of X-ray absorption that depends on the material. X-ray systems have to undergo calibration in regular intervals to ensure that the output signal of the detector is indicative of the amount of the received radiation. This is due to the fact that the properties of the X-ray system, in particular, properties of the X-ray source and the X-ray detector may change with time. Furthermore, the properties of a newly produced X-ray system may not be completely known. For example, the X-ray detector may comprise a scintillation material which responds to the incident X-ray radiation. This scintillation material may not be homogeneous. Furthermore, for line detectors made of a plurality of individual detector elements, the detector elements may have slightly different properties and therefore the detector may require calibration before use. In a common calibration process, a so-called phantom which is an object with known absorption properties is placed between the X-ray source and the X-ray detector within the X-ray beam. The output signal of the detector is recorded for the phantom and the X-ray system may be calibrated so that the output signal is indicative of the amount of radiation that must have passed through the phantom. In certain calibration processes, phantoms with spatially varying absorption properties are required to carry out calibration. A variety of possible calibration devices (phantoms) are known in the art. In general, the calibration devices are adapted for the calibration of a specific type of X-ray system. US 5,214,578 discloses a method for calibrating an X-ray system with an X-ray source and an X-ray detector, wherein the X-ray detector is rotatable on an axis around a body under study and wherein a circular phantom is positioned with its center offcentered with respect to the axis of rotation of the X-ray system. This calibration device is well-suited for calibrating X-ray systems with a rotatable detector. JP 7102190 B2 discloses a calibration device for an X-ray CT scanner. The calibration device comprises a plurality of concentric layers and at least one of the composition and concentration of substances included in each of the plurality of layers is different from each other at a plurality of rotation angles. The calibration device is scanned at the plurality of different rotation angles. This calibration device is well-suited for calibrating X-ray systems that are based on scanning at different rotation angles. US 4,400,827 discloses a calibration device for calibrating rapid sequence radiography. The calibration device comprises a disc on which a plurality of X-ray absorptive elements with different thickness perpendicular to the surface of the disc are arranged in a stepwise manner along the circumference of the disc. The disc is rotated along a central axis perpendicular to its surface in synchronism with cinematic photography means of the cinematic radiography means to thereby change the thickness of the X-ray absorptive material of the disc for each frame of the cinematic radiography. US 5,565,678 discloses a calibration target for a radiographic imaging system with a plurality of X-ray absorbing discs being stacked