Method for producing tomosynthetic images

p0001a method is known from WO 93/22 893 A1, with which it is possible to reconstruct a picture of a subject, without the case the projection angle α, the geometric arrangement of the radiation emitter and radiation detector and the focal plane are known. According to this method, a reference from radiation-absorbing material is provided with a known size and known distance from the radiation receiver in the range of the radiation receiver, which is projected at every single projection on the beam receiver. Based on local mapping of the reference to the radiation receiver for each individual projection of the geometric arrangement and the two-dimensional projection angle α can be determined.

p0002A holder for positioning a beam emitter of X-ray diagnostic apparatus for tomosynthesis is known from DE 44 14 689 A1. At the holder arm is coupled to the - viewed in the radiation direction - before the examination subject a spherical reference object and behind the object under examination, a radiation receiver are arranged. About the holder is set to a distance of the radiation transmitter to the reference object and the radiation receiver and the angle α of the light emitted by radiation transmitter beam to a reference axis of the holder. It is further known to arrange the adjustable radiation source in a housing to which a positioning device for the reference object and the radiation detector is coupled.

p0003Object of the invention is further advantageous embodiment of a method and apparatus for creating Tomosyntheseaufnabmen. In particular, should be created to make the device to position the object under examination and to create Tomosyntheseaufnahmen from the signals from the radiation detector by a precise detection of the geometrical arrangement of the radiation emitter particular radiation source, radiation detector and the object to be examined more flexible and effective ways.

p0004This object is achieved by a method according to claim 1 and an apparatus according to claim 11th

p0005Advantage of the invention is that in the method and the apparatus a reference object is used according to the invention, which consists of at least two sub-objects. Thus, it can be determined very accurately not only the distance of the radiation source from the radiation receiver, but also the angle of incidence (projection angle) and the irradiation direction. Even a rotation of the beam receiver relative to the reference object can be accurately detected. The reference object can also be directly connected to the beam transmitter and need not be coupled to the optical receiver.

p0006It is particularly advantageous if in the inventive method, the partial objects form of a bar and are arranged in a cross shape, or alternatively at least three sub-objects are provided, their mutual arrangement deviates from a straight line. The part objects can then spherical particularly advantageous or disc-shaped and form a geometric body. Do the sub-objects in terms of radiation absorption, it can thus be determined very precisely the irradiation direction.

p0007Further advantages and details of the invention will become apparent from the following description of an embodiment with reference to the drawing in conjunction with the dependent claims.

p0008It shows:<dl id="dl0001" compact="compact"><dt>1 shows</dt><dd>an X-ray diagnostic device for Tomosyntheseaufnahmen basic illustration, wherein the reference object has a fixed relation to the beam transmitter, with which it is directly connected,</dd><dt>FIG 2</dt><dd>an X-ray diagnostic device for Tomosyntheseaufnahmen basic illustration, wherein the reference object has a fixed relation to the radiation detector, with which it is directly connected,</dd><dt>FIG 3</dt><dd>a first,</dd><dt>FIG 4</dt><dd>a second,</dd><dt>FIG 5</dt><dd>a third and</dd><dt>FIG 6</dt><dd>A fourth embodiment of a reference object of the X-ray diagnostic device according to FIG 1 or FIG. 2</dd></dl>

p0009To perform the method for creating a Tomosyntheseaufnahme an examination object has an X-ray diagnostic appliance to a beam transmitter, in particular a radiation source 1, a reference object 2 and a radiation detector. 3 PURSUANT of Figure 1 here have another reference object 2 and the radiation transmitter, in particular the radiation source 1, for example via a bracket 11, a fixed reference. The signals produced by the radiation receiver 3 during irradiation of the reference object 2 and the examination object are an image forming device 4 is supplied from the signals of the reference object 2 the distance from the radiation receiver 3 and the object under examination and the irradiation angle (projection angle) and the irradiation direction and in conjunction with the signals the examination subject image signals a Tomosyntheseaufnahme calculated. According to the method for creating a Tomosyntheseaufnahme invention finds a reference object 2 application, which consists of at least two partial objects 5.6, which according to a first variant (FIG 3) are bar-shaped and intersect. In a second variant (FIG 4) finds a reference object 2 application at least three subobjects 7,8,9,10, whose relationship to each other is different from a straight line. These sub-objects 7,8,9,10 For example, spherical, disk, timbered, rod or cylindrical. Preferably, at least part of the object 6.10 different, at least in a partial area, in terms of radiation absorption, so that can be of further partial objects 5,7,8,9, the projection directions accurately determine if the dimensions of the reference object or the part of objects 5, are 6,7,8,9,10 known. The distinction in terms of radiation absorption may be determined by the absence or cutouts at the subobjects 6.10, the thickness, the length, the distance between them, their material or their shape.

p0010The X-ray diagnosis apparatus shown in FIG 2 is different from the X-ray diagnostic apparatus shown in FIG 1 in that the reference object 2 has a fixed relation to the radiation receiver 3, to which it, is, for example via a bracket 11 in connection.

p0011A particularly advantageous embodiment of the method is obtained if at least three different in terms of radiation absorption properties are part 12,13,14 provided their mutual arrangement deviates from a straight line. For this example, beads may be provided whose radiation absorption are different at least in some areas, for example by accessories fitted to the balls marking bodies and / or that the projection is at least approximately known in the radiation receiver 3 as to the location. In FIG 5, it is indicated that a first partial object 12 is formed for example as a solid sphere. A second and third partial object 13,14 have, for example formed as balls, an edge which in terms of radiation absorption by the core differs significantly. The second and third part object 13,14 differ in size or thickness of the edge. A particular advantage of this results that may be obtained from use of such a reference object that has a fixed relation to the object under examination, the position and orientation of the object under examination and the radiation source 1 relative to the radiation detector 3, the geometrical arrangement and the two-dimensional projection angle so that a Tomosyntheseaufnahme of the object can be reconstructed without the object under examination with the radiation receiver 3 or the radiation source 1 or these need to be coupled to one another. Another advantage is that the partial objects 12,13,14 of the reference object can be arranged independently in any position relative to the object under examination.

p0012By evaluating the mapping locations of the sub-objects on the radiation receiver 3 and the distortion occurring in oblique projection of its rays silhouette on the extent and direction can first determine the position of the radiation source 1 in the coordinate system of the radiation receiver. 3 If the position of the radiation source 1 is known, it can be concluded from the magnification with a known size of the partial objects to their position. With a first recording with any incident direction thus is an initial position of the object to define and subsequent changes in position can be clearly identified.

p0013In a modification of the method may also be a reference object of only two terms of radiation absorption differing part objects such as balls, and a third partial object that is formed bar- or rod-shaped, apply. An embodiment of such a reference object is shown in FIG. 6 It is shown that in this case a further first object part 15 is formed as a sphere. At another second embodied as a ball part object 16 a bar- or rod-shaped part object 17 is provided. This distinctness is produced simultaneously. The position of the radiation source 1 can thus already be determined using only two differing Subobjects 16.17. By evaluating the projection distortion of the two sections of the bar- or rod-shaped part object 17 a rotation of the object under examination can be determined by the line joining these subobjects 15.16.

p0014If more than three sub-objects used in the evaluation, so the accuracy of the position and angle determination can be improved and redundancy are kept, if, for example, the pictures of individual sub-objects can not be evaluated because superimpose this example with highly absorbent structures of the object under examination.