Two-dimensional slot x-ray bone densitometry, radiography and tomography

• US 6,496,557 B2
• Filed: 01/22/2001
• Issued: 12/17/2002
• Est. Priority Date: 02/09/2000
• Status: Expired due to Term

• Current Assignee: Hologic Incorporated
• Original Assignee: Hologic Incorporated
• Inventors: Wilson, Kevin E., Quinn, Vinnie, Cabral, Richard, Stein, Jay A., Smith, Andrew P.
• Primary Examiner(s): Bruce, David V.
• Assistant Examiner(s): Hobden, Pamela R.
• Application Number:
  US09/767,286
• Publication Number:
  US 20010048732A1
• Time in Patent Office: 694 Days
• Field of Search: 378/197, 378/205, 378/98.8, 378/11, 378/85, 378/21, 250/370.09
• US Class Current: 378/21
• CPC Class Codes: A61B 6/0487 Motor-assisted positioning
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4266 characterised by using a plurality of detector units A61B6/4014 takes precedence
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/4476 related to motor-assisted motion of the source unit
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/505 for diagnosis of bone
• CPC Class Codes: A61B 6/5241 combining overlapping images of the same imaging modality, e.g. by stitching
• CPC Class Codes: A61B 6/544 dependent on patient size
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 2223/612 biological material
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]

Abstract

An x-ray system using a slot-shaped detector having n rows and m columns of pixels, where n<<m, and providing a variety of relative motions between a patient table and a source-detector unit, including translation along the length of the table, translation across the table, and rotation about the focal spot, and processing the pixel values in a variety of ways to produce information such a shadow graphic x-ray images, tomosynthetic images of surfaces that need not be planar, and bone density estimates. In another embodiment, tomographic images can be obtained directly, using a post-patient collimator that passes nearly all of the primary beam to the imager while eliminating nearly all of the scatter. A feedback loop can equalize the exposure for selected parts of the image substantially in real time.

Claims

1. An x-ray examination process comprising:

scanning an x-ray beam and a slot-shaped x-ray detector relative to an object penetrated by the beam, while the beam impinges on the detector, and deriving pixel values related to x-rays received during respective time frames at pixel positions arranged in n rows and m columns in the detector, where n<

<

m;

processing said pixel values into a tomosynthetic image of a planar or a non-planar surface in the object through a process that comprises selectively shifting information regarding spatial positions for which said pixel values are derived relative to information regarding pixel positions in said image; and

displaying said tomosynthetic image.

2. An x-ray examination process as in claim 1 including rotating the beam about a selected rotational axis.

3. An x-ray examination process as in claim 2 in which said beam emanates from a focal spot coinciding with said rotational axis.

4. An x-ray examination process as in claim 1 including orienting the beam along a direction selected from a range of directions that includes both vertical and non-vertical directions, and carrying out said scanning thereafter at the selected orientation of the beam, said beam translating relative to the object during said scanning.

5. An x-ray examination process comprising:

providing an x-ray source and a detector mounted in alignment with each other such that an x-ray beam emanating from the source impinges on the detector after passing through an object subjected to examination;

said source and detector being mounted for motion as a unit relative to the object, said motion selectively including translation relative to the object along a first direction, translation relative to the object along a second direction transverse to the first direction, and rotation about a rotational axis transverse to said first direction and matching a focal spot from which said beam emanates;

scanning the source and detector relative to the object in a selected subset of said motions while detecting x-rays received by the detector within said beam at each of a multiplicity of pixel positions arranged in n rows and m columns, where n<

<

m, to derive respective pixel values related to x-rays received at said pixel positions in respective time frames;

processing said pixel values to estimate characteristics of portions of said object scanned during said scanning.

6. An x-ray examination process as in claim 5 in which said pixel values are dual-energy pixel values, one set for a lower range of x-ray energies and another set for a higher range of x-ray energies.

7. An x-ray examination process as in claim 6 in which said characteristics of the object comprise numerical bone density estimates.

8. An x-ray examination process as in claim 6 in which said characteristics of the object comprise an image derived from the pixel values for one of the two energy ranges.

9. An x-ray examination process as in claim 6 in which said characteristics comprise an x-ray image derived in a process involving blending the pixel values for the two energy ranges.

10. An x-ray examination process as in claim 6 in which said characteristics comprise a tomosynthetic image of a selected surface that is within the object and is selected from a planar surface and a non-planar surface.

11. A system comprising:

an x-ray source selectively generating an x-ray beam and an x-ray detector aligned therewith to receive x-rays within said beam;

a patient table between the source and the detector;

a support structure carrying said source and detector and selectively moving the source and detector along the length of the table, across the length of the table and up or down;

said support structure further selectively rotating the source and detector as a unit about a selected rotational axis that is transverse to the length of the table;

said detector comprising a slot shaped array of n rows and m columns of pixel positions, where n<

<

m, each pixel position producing a respective pixel value for each of a succession of time frames during a scanning motion of the source and detector relative to the patient table; and

a processor receiving said pixel values and deriving therefrom characteristics of a patient3 s body supported at said table.

12. A method of carrying out tomographic x-ray examination of a patient comprising:

moving with respect to each other at least two of the patient, a fan-shaped x-ray beam entering a first side of the patient, and an x-ray imager at a second side of the patient;

providing a post scatter collimator between the patient and the imager, said collimator having a slot-shaped window matching a cross-sectional shape of the fan-shaped x-ray beam; and

controlling the motion of at least two of the patient, the x-ray beam and the imager, while maintaining the x-ray beam and the window in the post scatter collimator in substantial alignment with each other, to form a tomographic x-ray image of a selected surface in the patient.

13. A method as in claim 12 in which the x-ray imager comprises a digital flat panel x-ray detector.

14. A method as in claim 12 in which the window in the collimator is a cut out in a plate of material that outside the window substantially blocks radiation emerging from the patient.