Patent ID: 12232901

DETAILED DESCRIPTION

FIG.1shows schematically an example embodiment of an X-ray imaging system1for time-resolved three-dimensional (3D) representation of at least one hollow organ7(seeFIG.3) of a person6. The X-ray imaging system1has an X-ray source2and an X-ray detector3, and a drive mechanism for positioning the X-ray source2and the X-ray detector3with respect to an acquisition region for positioning the person6, or the at least one hollow organ7, according to different projection directions. For example, the acquisition region may correspond to a region on a patient couch5or the like, which may be acquired by the X-ray source2and the X-ray detector3.

A projection direction may be specified, for example, by an angle α, for example, that is included by a connecting line between the X-ray source2and the X-ray detector3and an x-axis of a coordinate system spanning a plane in which, using the drive mechanism, the X-ray source2and the X-ray detector3may rotate about a rotational axis that is, for example, parallel to a z-axis that is perpendicular to the x-axis and y-axis.

In addition, the X-ray imaging system1has at least one computing unit4that may control the X-ray source2to emit X-ray radiation, and may obtain relevant detector data from the X-ray detector3. The relevant detector data corresponds to a projection image according to the instantaneous projection direction. The at least one computing unit4may also control the drive mechanism in order to set up the various projection directions.

The X-ray imaging system1may be used to perform an X-ray imaging method according to the present embodiments.FIG.2shows a schematic flow diagram of an example embodiment of such an X-ray imaging method.

During a preparatory phase V, a first time length T1 and a second time length T2 are determined for the person6. The first time length T1, for example, corresponds to a person-specific time length for a contrast agent to flow from a defined contrast-agent injection location for the person6to a defined proximal location8(seeFIG.3) of the at least one hollow organ7. The second time length T2 corresponds to a person-specific time length for the contrast agent to flow from the proximal location8to a defined distal location9(seeFIG.3) of the at least one hollow organ7. Two X-ray acquisitions (e.g., subtraction images) of a vascular tree during a venous phase and an arterial phase, respectively, after contrast agent administration are shown schematically inFIG.3, and an example of a proximal location8in an example of a distal location9is marked. The vascular tree corresponds to the at least one hollow organ7in a suitable embodiment of the X-ray imaging method.

During a first acquisition phase A1, a first sequence of projection images is produced, where each projection image in the first sequence at least partially represents the at least one hollow organ7under a different respectively defined projection direction. The first acquisition phase A1, for example, begins the first time length T1 after the injection start time, at which the injection of the contrast agent is started at the contrast-agent injection location. A duration of the first acquisition phase is equal to the second time length T2.

For example, during a second acquisition phase A2 after the first acquisition phase A1, a second sequence of projection images may be produced, where each projection image in the second sequence at least partially represents the at least one hollow organ7under a different respectively defined projection direction. The second acquisition phase A2 begins at the time the first acquisition phase A1 ends.

A time-resolved three-dimensional reconstruction of the at least one hollow organ7is produced by the at least one computing unit4based on the projection images in the first sequence and, if applicable, based on the projection images in the second sequence. For example, a static three-dimensional reconstruction of the at least one hollow organ7may be produced based on the projection images in the second sequence, and the projection images in the first sequence may each be reprojected into the static three-dimensional reconstruction in order to produce overall the time-resolved three-dimensional reconstruction.

In some embodiments, the X-ray imaging method may be configured as a 4D-DSA method, for example. In this case, during a first mask acquisition phase M1, a first mask sequence of projection images is produced, where each projection image in the first mask sequence at least partially represents the at least one hollow organ7under a different projection direction in each case. Each projection image in the first mask sequence is associated with exactly one projection image in the first sequence, so that the projection direction of the projection image in the first mask sequence is the same as the projection direction of the associated projection image in the first sequence. For each projection image in the first mask sequence, a first subtraction image is produced by subtracting the projection image in the first mask sequence from the associated projection image in the first sequence.

For example, during a second mask acquisition phase M2, a second mask sequence of projection images is produced, where each projection image in the second mask sequence at least partially represents the at least one hollow organ7under a different projection direction in each case. Each projection image in the second mask sequence is associated with exactly one projection image in the second sequence, so that the projection direction of the projection image in the second mask sequence is the same as the projection direction of the associated projection image in the second sequence. For each projection image in the second mask sequence, a second subtraction image is produced by subtracting the projection image in the second mask sequence from the associated projection image in the second sequence.

The time-resolved three-dimensional reconstruction is then produced based on the first subtraction images and, for example, based on the second subtraction images. For example, the static three-dimensional reconstruction of the at least one hollow organ7may be produced based on the second subtraction images, and the first subtraction images may each be backprojected into the static three-dimensional reconstruction in order to produce the time-resolved three-dimensional reconstruction.

A preparatory sequence of projection images may be produced during the preparatory phase V, with each projection image in the preparatory sequence representing the proximal location8and the distal location9. The preparatory sequence begins at the same time as a further injection start time for injecting the contrast agent at the contrast-agent injection location, and the first time length T1 and the second time length T2 are determined based on the projection images in the preparatory sequence.

FIG.4shows in this regard a time curve10of the image intensity of the projection images in the preparatory sequence at the proximal location8, and a corresponding time curve11of the image intensity at the distal location9. The first time length T1 and the second time length T2 may be determined, for example, by determining points of intersection of the respective rising edges of the time curves10,11with a horizontal line given by a defined threshold intensity It. The first time length T1 then corresponds to a point in time at which the time curve10at the proximal location8first reaches the threshold intensity It. The second time length T2 corresponds to the time period between the point of intersection of the curve10with the threshold intensity Itand the point in time at which the time curve11first exceeds the threshold intensity It. In other embodiments, different threshold intensities may also be used for the two time curves10,11. It is also not absolutely necessary for T1 and T2 to be determined based on the same preparatory sequence. For example, two different preparatory sequences may be used for T1 and T2.

The respective number of projection images during the first and second acquisition phases A1, A2, and hence the angular increments between directly successive projection images in the first acquisition phase A1, and, given a set duration, in the second acquisition phase A2, result, for example, from the desired image quality.

FIG.5shows schematically a procedure of a further example embodiment of an X-ray imaging method.

After the injection start time, and after an X-ray delay corresponding to the first time length T1, a first subrange12aof an angle range12of the angle α is traversed in the first acquisition phase A1. The first subrange12ais traversed, for example, within the second time length T2. Then, a second subrange12bof the angle range12is traversed in the second acquisition phase A2 within a further time length ΔT. The first subrange12aand the second subrange12btogether amount to the angle range12, and are traversed in succession in the same direction. Therefore, including the X-ray delay, a time T1+T2+ΔT, for example, is needed to produce the first sequence and the second sequence.

The second subrange12bmay correspond, for example, to an angle range of 200° in total, and the first subrange may equal an angle range of 60°, for example. The angle α thus sweeps a total angle of 260° in the angle range12. Angle ranges that differ from this may be chosen. It has been found that a reliable static three-dimensional reconstruction is possible for an angle range of 200°. The additional 60° of the first subrange12ais then available for capturing the time-resolved information.

If the X-ray imaging method is being performed as a 4D-DSA method, during the mask phases M1, M2, overall, the entire angle range12is likewise traversed, for example, but not necessarily, within the same total time T2+ΔT. For example, the first subrange12amay be traversed during the first mask acquisition phase M1, and the second subrange12bmay be traversed thereafter during the second mask acquisition phase M2. In an optional act M′ between the second mask acquisition phase M2 and the first acquisition phase A1, the angle α may be reset by suitable positioning of the X-ray source2and the X-ray detector3.

FIG.6shows a schematic procedure of a further example embodiment of an X-ray imaging method. Again in this case, the first acquisition phase A1 begins the first time length T1 after the time of injection. During the first acquisition phase A1, the angle α traverses within the second time length T2 an angle range13in a first direction. In the subsequent second acquisition phase A2, the angle α traverses the angle range13again (e.g., in a second direction) that is opposite to the first direction. This may likewise take place within the second time length T2, although this is not absolutely necessary.

Since the angle range13is traversed in full both during the first acquisition phase A1 and during the second acquisition phase A2, the angle range13may be chosen to be smaller than the angle range12in the example ofFIG.5. For example, the angle range13may equal 200°. If the second acquisition phase A2 also has a duration T2, then the time period from the time of injection until the completion of the second acquisition phase A2 equals T1+2*T2.

In the case of 4D-DSA, the angle range13may, for example, likewise be traversed twice in full before the injection start time: once in the first direction during the first mask acquisition phase M1; and in the second direction during the second mask acquisition phase M2. The mask acquisition phases M1, M2 may likewise each be equal to the second time length T2. In this case, the total acquisition time is given by T1+4*T2. Again, however, this is not absolutely necessary.

Independent of the grammatical term usage, individuals with male, female or other gender identities are included within the term.

The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.