X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1999-01-19
2001-04-10
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S062000
Reexamination Certificate
active
06215849
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the obtaining of a digitized overall radiographic picture of an object from a succession of partially overlapping initial radiographic pictures taken from different points of view.
The invention applies advantageously, but without implying any limitation, to the pictures acquired in the course of an arteriography of the lower limbs, or in the course of a radiography of the spine from successive images acquired along the vertebral column.
Hardening, stenosis and blocking of the arteries of the lower limbs are detected during a vascular examination of all of the two limbs.
One conventional solution consists in employing an arteriophlebography drum which, on each of its faces, has a cassette of radiological film having a length of approximately 1.20 m. Exposing the patient to X-radiation therefore makes it possible to obtain an overall picture of the lower limbs directly. However, such a solution requires the use of bulky equipment.
Furthermore, a more recent solution consists in using successive films of smaller size (35×35) combined with a programmed advance table. The radiologist can then monitor the progress of the contrast product flowing through the blood vessels of the lower limbs, for example. The various images are then cut manually to avoid overlaps and are repasted manually to reconstruct an image with a total length of 1.20 m, allowing the leg to be viewed in its entirety.
Such a solution therefore requires the handling of films when the radiologist wishes to reconstruct a panoramic view of the legs.
The invention aims to provide a more satisfactory solution to the problem of obtaining an overall radiographic picture of an object from a succession of partially overlapping initial radiographic pictures taken from different points of view.
BRIEF SUMMARY OF THE INVENTION
An embodiment of the invention provides an automatic way, in a computer, of cutting and pasting digital pictures having partial overlap.
In this regard, the embodiment uses the partial overlap zones between the successive pictures to “digitally paste” the pictures in order to obtain the digitized overall picture of the object, in particular the leg.
An embodiment of the invention therefore proposes a method for obtaining a digitized overall radiographic picture of an object from a succession of partially overlapping initial or “primary” radiographic pictures taken from different points of view.
In an embodiment of this method, a digitized secondary image which promotes predetermined elements of interest of the object is created from each primary image or picture. Such a secondary image is, for example in an arteriography application, an image on which the predetermined elements of interest of the object appear, in this case the blood vessels. Such a secondary image may, for example, be obtained by taking the difference between an opacified image (primary image), after injection of a contrast product into the leg, and a so-called “mask” image, that is to say an image obtained without contrast product.
Digital processing for two-dimensional mutual resetting of the secondary images is then carried out per pair of consecutive images so as to obtain mutually reset digitized secondary images. This reset processing is carried out by promoting the predetermined elements of interest of the object and takes into account the motion of the picture acquisition system relative to the patient, for example the displacement step of the table, which may be known or unknown, and the depth of the various elements of interest (for example the blood vessels) inside the object (for example the leg).
For each current reset secondary image a region common to the said current image and to the following reset secondary image is then defined, this common region being bounded by the two respective median horizontal lines of the two reset secondary images. The digitized overall radiographic picture is then created from the upper region of the first reset secondary image of the succession of images taken, this upper region lying above the common region of this first image. The radiographic picture is also created from the lower region of the last reset secondary image of the succession, this lower region lying below the common region of this last image. Lastly, the overall radiographic picture is created from the common regions of each pair of reset secondary images.
According to one embodiment of the method, for each reset secondary image a common region is defined which includes an upper common zone and a lower common zone which respectively extend on either side of the median cut line of the said common region. The overall radiographic picture is then created by using, for each common region, the upper common zone of the common region of the current secondary image and the lower common zone of the common region of the following secondary image.
In other words, the cut line is defined as the trace lying in the middle of the region common to a pair of successive secondary images, a common region whose upper (or lower, respectively) transverse boundary corresponds to the median horizontal line (central line) of the first (or second, respectively) picture of the pair in question. The digital pasting is carried out by aligning and superimposing the cut line while keeping the section (upper common zone) lying above the cut line of the first picture of the pair in question and the section (lower common zone) lying below the cut line of the second picture of the pair in question.
However, when two cuts are assembled in this way, a picture is obtained whose transition is visible on the overall radiographic picture, because of the differences in intensity which are connected with the disparities of points of view, path and absorption of the X-rays giving rise to these pictures.
The embodiment of the invention thus very advantageously proposes digital pasting by “lap dissolve” allowing this problem to be solved. In other words, the final picture results from a progressive transition from one picture to the next, by fading the first and introducing the following one. The various cut lines are therefore invisible in the overall radiographic picture, the background then being continuous.
In other words, according to this advantageous variant of the embodiment of the invention, the overall radiographic picture is created by using, for each common region, a weighted sum of the logarithms of the grey levels of the respective upper and lower common zones of two consecutive reset secondary images.
In certain applications, in particular in arteriography, the acquisition of the primary images may include acquisition of primary images taken from different points of view, referred to as “moving images”, and acquisition of at least one group of several consecutive primary images taken from the same point of view, referred to as “fixed images”. The fixed secondary images corresponding to the fixed primary images are then created, and from these fixed secondary images, a resultant secondary image is created which is used, for the digital reset processing, with the last moving secondary image preceding the first fixed image of the said group, and with the first moving secondary image following the last fixed image of the said group.
The creation of the secondary image resulting from the fixed images advantageously comprises a search for maximum intensity between the corresponding pixels of the fixed secondary images.
In other words, the pictures acquired with fixed points of view, for example in order to fully opacify the underlying arterial network, are merged beforehand into a single picture which will be combined with the moving adjacent pictures of the series of pictures acquired.
The creation of each secondary image which promotes the predetermined elements of interest may comprise acquisition, for each take, of the primary image on which the elements of interest appear (opacified image) and a mask image on which the elements of interest do not appear (unopacified image), then subtraction of th
Lienard Jean
Rougée Anne Marie
Bruce David V.
Chaskin Jay L.
GE Medical Systems SA
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