2D and 3D tomographic X-ray imaging using flat panel detectors

• US 6,236,708 B1
• Filed: 11/25/1998
• Issued: 05/22/2001
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Original Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Inventors: Griesmer, Jerome J., Lin, Zhongmin, Plut, Leonard F., Negrelli, Donald E.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US09/200,652
• Time in Patent Office: 909 Days
• Field of Search: 378/22, 378/21, 378/98.8
• US Class Current: 378/22
• CPC Class Codes: A61B 6/025 Tomosynthesis

Abstract

A penetrating radiation source (14) is disposed on one side of a object (10) which is on a object support (12). A flat panel radiation detector (18) is stationarily disposed on the opposite side of the object (10) than the source (14). A moving system (16, 50, 52) moves the source (14) with respect to the object (10). In each position (X_i, Y_i, Z_i) of the source (14) a center ray of the x-ray beam strikes the detector (18) at a corresponding location (x_i, y_i, 0). For each position (X_i, Y_i, Z_i) of the source (14), the image (x_i, y_i, 0) of an object located on a focal plane offsets by a vector displacement (D_i) relative to a reference position (x_o, y_o, z_o) of the image when the source is at (X₀, Y₀, Z₀). A processor (28) shifts and interpolates each view by the different vector displacements corresponding to each of the focal planes (L₁, L₂, . . . ) and integrates the images to generate a series of slice image representations which are stored in a volume image memory (30). In this manner, by adjusting the view offset by an amount corresponding to each of the focal planes, (L₁, L₂, . . . ) the same data set is used to generate all of the slices of the resultant volume image.

Claims

1. A tomographic imaging system comprising:

a support surface for stationarily supporting a region of interest of a patient to be imaged;

a flat panel detector stationarily mounted parallel to the patient support surface, the flat panel detector being larder than the region of interest in planes parallel to the patient support surface;

an x-ray source for generating penetrating radiation, the x-ray source being movably mounted on an opposite side of the region of interest from the flat panel detector such that the penetrating radiation from the x-ray source passes through the region of interest and is received by the flat panel detector;

a moving system for moving the x-ray source relative to the region of interest such that the penetrating radiation passing from the x-ray source to the flat panel detector passes through the region of interest at a plurality of angles and impinges upon a plurality of different portion of the flat panel detector, the flat panel detector being accessed to generate a plurality of views corresponding to each of a plurality of the angular orientations between the x-ray source and the region of interest;

a reconstruction processor for reconstructing the plurality of views into a tomographic image, the reconstruction processor including;

a means for sorting the views by the angle with which the radiation passed through the region of interest and spatially shifting the views in accordance with said angle;

a means for spatially shifting and interpolating the views in accordance with each of a plurality of selected focal planes; and

,

a means for summing the views spatially shifted in accordance with each of the focal planes to generate a slice image corresponding to each focal plane;

an image memory for storing the slice images; and

a video processor for converting selected portions of the slice images in the image memory into an appropriate format for display on a monitor.

2. An apparatus for imaging a region of interest of an object to generate a three dimensional image representation, the apparatus comprising:

a radiation source for sending a beam of penetrating radiation through the region of interest;

a moving system for cyclically moving the radiation source relative to the object during imaging through a path which passes closer and further from the object;

a flat panel detector stationarily mounted opposite the region of interest from the radiation source for detecting radiation after it has passed through the region of interest, the detector outputting a plurality of electronic views representative of detected radiation intensity variations across the detector in relation to a plurality of different positions of the radiation source relative to the region of interest; and

,

a processor for receiving the plurality of electronic views from the detector, the processor including;

an image correction means for correcting blurring and distortion caused by variations in magnification of the plurality of electronic views as the radiation source moves closer and further from the object during imaging; and

,

a means for generating a stack of slice images from the magnification corrected views to form the three dimensional image representation of the region of interest.

3. The apparatus as set forth in claim 2, wherein the processor further includes:

a means for storing each of the plurality of electronic views;

a means for shifting each of the plurality of electronic views such that radiation attenuation attributable to incremental elements within a selected focal plane, which is parallel to the detector, are displaced at a coherent location in each of the plurality of electronic views while radiation attenuation from incremental elements outside of the selected focal plane contribute to a plurality of locations on the detector; and

,

a view integration means for integrating the shifted views to generate a slice image in the stack of slice images in which data from the incremental elements within the selected focal plane is emphasized and data attributable to the incremental elements outside of the selected focal plane become blurred.

4. The apparatus as set forth in claim 3, wherein the processor includes a means for incrementing the selected focal plane such that the slice image of the stack of slice images is generated and further including a volumetric image memory for storing the stack of slice images.

5. The apparatus as set forth in claim 3 further including:

an image correction means for reducing a contribution of the incremental elements outside of the selected focal plane in the slice image.

6. An apparatus for imaging a region of interest of an object to generate a three dimensional image representation, the apparatus comprising:

an x-ray source for sending a beam of penetrating radiation through the region of interest of the object;

a flat panel detector mounted stationarily relative to the object and the x-ray source for detecting radiation after it has passed through the region of interest of the object, the detector being disposed on an opposite side of the object from the radiation source, the detector outputting a plurality of electronic views representative of detected radiation intensity variations across the detector in relation to a plurality of different positions of the x-ray source relative to the object;

a moving system for moving the x-ray source along an arcuate path such that the x-ray source remains a substantially fixed distance from the flat panel detector to minimize magnification effect; and

,

a processor for receiving and processing the plurality of electronic views from the detector to generate a stack of slice images parallel to the detector to form the three dimensional image representation of the region of interest.

7. The apparatus as set forth in claim 6, wherein:

the moving system supports the x-ray source above the object; and

,

the flat panel detector is stationarily mounted below an object support device.

8. An apparatus for imaging a region of interest of an object to generate a three dimensional image representation, the apparatus comprising:

a radiation source for sending a beam of penetrating radiation through the region of interest of the object;

a moving system for supporting the radiation source below an object support device and for moving the radiation source relative to the object during imaging;

a detector mounted above the object for detecting radiation after it has passed through the region of interest of the object, the detector being disposed on an opposite side of the object from the radiation source, the detector outputting a plurality of electronic views representative of detected radiation intensity variations across the detector in relation to a plurality of different positions of the radiation source relative to the object; and

,

a processor for receiving and processing the plurality of electronic views from the detector to generate a stack of slice images from an axis of the object which is parallel to the detector to form the three dimensional image representation of the region of interest.

9. An apparatus for imaging a region of interest of an object to generate a three dimensional image representation, the apparatus comprising:

a radiation source for sending a beam of penetrating radiation through the region of interest of the object;

a mechanism for moving the radiation source along a spiral trajectory such that the radiation beam passes through the region of interest from a multiplicity of angles and with a variety of radii;

a flat panel detector for detecting radiation after it has passed through the region of interest of the object, the detector being disposed stationarily on an opposite side of the object from the radiation source, the detector outputting a plurality of electronic views representative of detected radiation intensity variations across the detector in relation to a plurality of different positions of the radiation source relative to the object; and

,

a processor for receiving and processing the plurality of electronic views from the detector to generate a stack of slice images to form the three dimensional image representation of the region of interest.

10. A method of generating three dimensional tomographic images of a region of interest of a patient, the method comprising:

a) projecting penetrating radiation from a radiation source through the region of interest;

b) receiving the radiation which has passed through the object on a stationary flat panel detector and converting the received radiation into electronic views indicative of variations in the received radiation across the detection plane;

c) moving the radiation source to a plurality of positions relative to the region of interest such that radiation from the radiation source passing through each of a plurality of focal planes, which are parallel to the flat panel detector and within the region of interest, impinges upon spatially shifted offset portions of the flat panel detector;

d) sampling the electronic views from the flat panel detector at each of a plurality of positions of the radiation source;

e) spatially shifting the electronic views for a first selected focal plane, such that the radiation which passes through an incremental element on the first selected focal plane contributes to a common pixel of each spatially shifted electronic view;

f) summing the spatially shifted electronic views such that the pixels of each spatially shifted electronic view corresponding to the incremental element on the first selected focal plane are summed to generate a first slice image taken through the first selected focal plane and such that radiation attenuation attributable to incremental elements of the region of interest which are off the first selected focal plane are distributed inconsistently among the pixels to form a background blur;

g) storing the first slice image in a volumetric image memory;

h) repeating steps (e), (f), and (g) with different spatial shifts corresponding to additional focal planes to generate additional slice images; and

,

i) storing the additional slice images in the volumetric image memory to form a three dimensional tomographic image.

11. The method as set forth in claim 10 further including:

selecting a plurality of focal planes and repeating the shifting and the summing of the electronic view to generate slice images, wherein each of the slice images corresponds to each of the plurality of focal planes.

12. The method as set forth in claim 11 further including:

storing each of the slice images; and

,

retrieving selected portions of the slice images and converting the retrieved selected portions into a display image.

13. The method as set forth in claim 10 further including:

filtering the slice images to remove blurred background attributable to the incremental elements of the region of interest off of the first selected focal plane.

14. A method of generating diagnostic images of a region of interest of an object, the method comprising:

projecting penetrating radiation from a radiation source through the region of interest;

receiving the radiation which has passed through the object on a radiation detection plane and converting the received radiation into electronic views indicative of variations in the received radiation across the detection plane;

cyclically moving the radiation source to a plurality of positions closer and further from the region of interest such that radiation from the radiation source passing through each of a plurality of focal planes, which are parallel to the detector plane and within the region of interest, impinge upon offset portions of the detector plane and such that there are variations in magnification among the electronic views;

scaling the electronic views to a common dimension;

shifting the electronic views for a first selected focal plane, such that the radiation which passes through an incremental element on the first selected focal plane contributes to a common pixel of the shifted and scaled electronic views;

shifting the electronic views for a second selected focal plane, such that the radiation which passes through an incremental element on the second selected focal plane contributes to a common pixel of the shifted and scaled electronic views; and

,

summing the shifted and scaled electronic views such that the pixels of each electronic view corresponding to the incremental element on the first selected focal plane are summed to generate a slice image taken through the first selected focal plane and the pixels of each electronic view corresponding to the incremental element on the second selected focal plane are summed to generate a slice image taken through the second selected focal plane such that radiation attenuation attributable to incremental elements of the region of interest which are off the first and second selected focal planes are distributed inconsistently among the pixels to form a background blur.