Patent Application
20070268999
a-c illustrate each schematically, in a top view, a particular X-ray bundle as it traverses the object during scanning by the X-ray apparatus of
The apparatus of
The X-ray apparatus comprises generally an X-ray source 21 and an X-ray detector 23 as being illustrated in
The reconstruction device 15 for creating a three-dimensional tomosynthesis image of the object 13 from the tomosynthesis image data may e.g. be any device known in the art. The reconstruction may be based on e.g. shift-and-add, filtered back projection, Fourier, or iterative methods for calculating the attenuation in the object 13 in three dimensions. Typically, the three-dimensional tomosynthesis image is obtained in the shape as a stack of parallel two-dimensional images 25 as being illustrated in
The projection image construction device 17 is arranged for creating the two-dimensional projection image of the object 13 by means of projecting the three-dimensional tomosynthesis image on a first plane. Hereby, a high-quality two-dimensional projection image with high spatial resolution, signal-to-noise ratio, dynamic range, and image contrast is obtained.
Preferably, the two-dimensional projection image is formed by means of summing, for each of the pixels of the two-dimensional projection image 27, pixel values of pixels along a respective straight line 29 in the three-dimensional tomosynthesis image 25 as shown in
The geometry that is reconstructed is cone-shaped with an almost point-shaped X-ray source 21 at the top, from which a cone-shaped X-ray bundle of radiation is originating. The X-ray bundle traverses the object 13 and strikes the X-ray detector 23. The straight lines 29 thus coincide with the propagation path of radiation photons of the cone-shaped X-ray bundle.
If the tomosynthesis image is in the form of a reconstructed three dimensional model of the object, the summation could alternatively be done in any direction through the three dimensional model. For instance, the summation could be done in along parallel lines direction through the three dimensional model, e.g. perpendicular to the planes 25.
Further, the invention does not exclude that the two dimensional projection image is calculated in the same way as a three dimensional model of the object is calculated, but where the three dimensional model only consists of a single layer of voxels. The attenuation of X-rays in each voxel is then a representation of the two dimensional projection image.
Thus, according to a further embodiment of the invention three-dimensional tomosynthesis and two-dimensional attenuation images of the object 13 are created, wherein the tomosynthesis image data of the object is collected in a single measurement, a three-dimensional tomosynthesis image 25 of the object is created from the tomosynthesis image data, wherein the three-dimensional tomosynthesis image 25 comprises a plurality of stacked two-dimensional images (in some sense all three-dimensional images can be seen as a stack of two-dimensional images), and a two-dimensional attenuation image of the object is created from the three-dimensional tomosynthesis image by means of selecting a single one of the plurality of stacked two-dimensional images.
Alternatively, multiple ones, but maybe not all, of the plurality of stacked two-dimensional images are added to create the two-dimensional attenuation image of the object 13.
The reconstruction device 15 and the projection image construction device 17 may be integrated as software program modules in a common apparatus such as a microcomputer. The microcomputer and/or the display device 19 may further be integrated into the X-ray apparatus 11 or may be separate devices.
The microcomputer is advantageously provided for displaying the three-dimensional tomosynthesis image and the two-dimensional projection image simultaneously side by side on the display device 19 so that the physician or radiologist will be able to compare the three-dimensional tomosynthesis image with the more familiar two-dimensional projection image.
More advantageously though, the microcomputer comprises input means, e.g. a keyboard, a pointing device, or voice command receiving means for receiving user selections, and the display device 19 is provided for displaying the two-dimensional projection image in response to a first user selection through the input means and for displaying the three-dimensional tomosynthesis image in response to a second subsequent user selection through the input means. Hereby, the physician or radiologist is able to study the more familiar two-dimensional projection image firstly, and then if something suspicious is found, the physician or radiologist may select to display the three-dimensional tomosynthesis image without having to perform a second measurement. The microcomputer may have means for displaying the three-dimensional tomosynthesis image in various manners and layouts and means for displaying several three-dimensional tomosynthesis images from different angles—one after the other or several at the same time.
Further, the projection image construction device 17 may be arranged for creating a second two-dimensional projection image of the object 13 from the three-dimensional tomosynthesis image 25 by means of projecting the three-dimensional tomosynthesis image on a second plane, wherein the first and second planes are non-parallel. Hereby, a second two-dimensional projection image of the object 13 at another view angle is obtained. Such second two-dimensional projection image may be of importance to the physician or radiologist, not at least in mammography applications.
If the X-ray apparatus 11 is provided for obtaining the tomosynthesis image data at angles defining an angular range of at least 90°, the first and second planes may be substantially perpendicular to each another. In case of mammography two two-dimensional projection images may be taken of each of the patient's breast—one two-dimensional projection image from above and one two-dimensional projection image from the side.
It shall be appreciated that in case the three-dimensional tomosynthesis image is formed by a three-dimensional set of pixels or picture elements, each in the shape of e.g. a cube or cuboid, and each representing the X-ray attenuation in a corresponding voxel of the object 13, each of the summations of pixel values of pixels along a respective straight line in the three-dimensional tomosynthesis image may be weighted depending on how the straight line passes or cuts through the pixels. For example, if the straight line passes or cuts through a pixel in the middle thereof the pixel value of that pixel should be given high weight in the summation, whereas if the straight line passes or cuts through a corner portion of a pixel the pixel value of that pixel should be given low weight in the summation.
Generally, if the pixels in the three-dimensional tomosynthesis image are cubic or cuboidic, the weight of the pixel value of each cubic or cuboidic pixel along each straight line may depend on the length of the straight line that is within the cubic or cuboidic pixel.
With reference now to
The X-ray apparatus comprises a divergent X-ray source 31, which produces X-rays 32 centered around an axis of symmetry 33, a collimator 34, a radiation detector 36, and a device 37, which rigidly connects the X-ray source 31, the collimator 34, and the radiation detector 36 to each other and which moves the X-ray source 31, the collimator 34, and the radiation detector 36 linearly in direction 38 essentially orthogonal to the axis of symmetry 33 to scan scan an object 35, which is to be examined.
The radiation detector 36 comprises a stack of line detectors 36a, each being directed towards the divergent radiation source 31 to allow a respective ray bundle b1, . . . , bn, . . . , bN of the radiation 32 that propagates in a respective one of a plurality of different angles α1, . . . , αn, . . . , αN with respect to the front surface of the radiation detector 36 to enter the respective line detector 36a.
The collimator 34 may be a thin foil of e.g. tungsten with narrow radiation transparent slits etched away, the number of which corresponds to the number of line detectors 36a of the radiation detector 36. The slits are aligned with the line detectors 36a so that X-rays passing through the slits of the collimator 34 will reach the detector units 36a, i.e. as the respective ray bundles b1, . . . , bn, . . . , bN. The collimator 34, which is optional, prevents radiation, which is not directed directly towards the line detectors 36a, from impinging on the object 35, thereby reducing the radiation dose to the object 35. This is advantageous in all applications where the object 35 is a human or an animal, or parts thereof.
During scanning the device 37 moves the radiation source 31, the collimator 34, and the radiation detector 36 relative to the object 35 in a linear manner parallel with the front of the radiation detector as being indicated by arrow 38, while each of the line detectors 36a records a plurality of line images of radiation as transmitted through the object 35 in a respective one of the different angles α1, . . . , αn, . . . , αN.
The scanning may alternatively be performed by rotating the radiation source 31, the collimator 34, and the radiation detector 36 relative to the object 35. It shall also be appreciated that a similar scanning is obtained by holding the radiation source 31, the collimator 34, and the radiation detector 36 still and instead moving the object 35 to be examined.
The scanning of the object 35 is performed a length, which is sufficiently large so that each one of the line detectors 36a can be scanned across the entire object of interest to obtain, for each of the line detectors 6a, a two-dimensional image of radiation as transmitted through the object 35 in a respective one of the different angles α1, . . . , αn, . . . , αN.
In
As can be seen in
A preferred line detector for use in the X-ray apparatus of
For further details regarding such kind of gaseous-based line detectors for use in the present invention, reference is made to the following U.S. Patents by Tom Francke et al. and assigned to XCounter AB of Sweden, which patents are hereby incorporated by reference: U.S. Pat. Nos. 6,546,070; 6,522,722; 6,518,578; 6,118,125; 6,373,065; 6,337,482; 6,385,282; 6,414,317; 6,476,397; and 6,477,223.
It shall, nevertheless, be realized that any other line detector may be used in the X-ray apparatus of
Still further, other X-ray apparatuses such as e.g. one including a two-dimensional flat panel detector for detection may be used in the apparatus of
| Number | Date | Country | Kind |
|---|---|---|---|
| 0601135-7 | May 2006 | SE | national |
