CN102429680B - For method and the computed tomographic scanner of computed tomographic scanner - Google Patents

Abstract

The invention relates to a method for recording x-ray projections of specified tissues of a patient (P) and a computed tomography scanner with at least one x-ray source (6) and at least one x-ray detector (7) and The X-ray system of the isocenter (IZ) and the patient (P) perform relative movement adjustment along the direction of the system axis (S) of the computed tomography scanner (1) extending through the isocenter (IZ) when taking the X-ray projection, wherein, The specified tissue has a centerline (M) or tissue axis (G) along which to scan, but the centerline (M) or tissue axis (G) is not parallel to the system axis (S), where the X-ray system and the patient ( P) are adjusted to move in combination relative to each other such that the centerline (M) or tissue axis (G) moves through the isocenter (IZ) of the X-ray system.

Description

Method for a computed tomography scanner and computed tomography scanner

technical field

The invention relates to a method for recording x-ray projections of specified tissues of a patient in a helical scan using a computed tomography scanner. The invention also relates to a computer program for carrying out the method, a data carrier with the computer program, and a computed tomography scanner with a computer unit in which the computer program is loaded for execution.

Background technique

In computed tomography, the patient is scanned in sequential or helical scans. In helical scans, for example by means of third-generation computed tomography scanners, the scan is generally performed with the table height and the tilt angle of the gantry unchanged relative to the patient. Before the helical scan, the patient support plate with the patient is first generally oriented relative to the system axis of the computed tomography scanner, which runs through the isocenter of the x-ray system, so that the system axis runs through the tissue of interest of the patient to be scanned. During a helical scan, the patient support plate with the patient is moved in the direction of the system axis through the measuring range defined by the X-ray system, the tissue of interest is thus located at the isocenter of the X-ray system, and thus the quality of the tissue of interest can be generated. Changed tomographic images.

However, there are also patient tissues, in particular tissues that extend over a certain length, such as the femur or the spine, which cannot be completely scanned in the above-described manner, because the femur or the spine is oriented when the patient is lying flat on the patient support plate Not parallel to the surface of the patient support plate or the system axis of the gantry. Therefore, during the adjustment movement of the patient support plate, the section of the femur or the spine is not on the isocenter of the x-ray system, so that the tomographic images generated by the femur or the spine have a mutual relationship depending on the position of the femur or the spine relative to the isocenter. Different image quality.

Contents of the invention

The technical problem underlying the invention is to provide a method, a computer program, a data carrier and a computed tomography scanner of the type mentioned at the outset, whereby the image of a tissue tomogram generated during a helical scan can be improved Quality, in particular improving the image quality of tomographic images of tissues whose center lines or tissue axes do not run parallel to the system axis of the computed tomography scanner when the patient is lying flat on the patient support plate.

According to the invention, this technical problem is solved by a method for recording x-ray projections of defined tissues of a patient in a helical scan using a computed tomography scanner, wherein at least one x-ray source and at least one x-ray detector are provided and The x-ray system of the isocenter and the patient are adjusted to move relative to each other in the direction of the system axis of the computed tomography scanner extending through the isocenter when the x-ray projections are taken, wherein a given tissue has a centerline or tissue axis along which to scan , but the centerline or tissue axis is not parallel to the system axis of the computed tomography scanner extending through the isocenter of the X-ray system when the patient is lying flat on the examination table, wherein the X-ray system and the patient are adjusted for combined movement relative to each other or The resultant movement is such that the centerline or tissue axis moves through the isocenter of the X-ray system.

The inventors of the present invention therefore propose to adjust the x-ray system and the patient to one another depending on the alignment of the center line or tissue axis of the specified tissue of interest to be imaged in the tomographic image or volume data set. Since the center line or tissue axis is not parallel to the system axis of the computed tomography scanner or, for example, to the surface of the patient support plate of the examination table when the patient is lying flat on the examination table, a relative mobile adjustment of the x-ray system and the patient is not possible. It proceeds purely linearly in the direction of the system axis, but also has at least one motion component transverse to the system axis. In this way it can be achieved that the tissue of interest which is to be imaged in the tomographic image is always at least partially located at the isocenter of the x-ray system or at the isocenter of the imaging plane of the x-ray system during the recording of the x-ray projections, whereby Quality-invariant tomographic images of specified tissues of interest can be generated or reconstructed.

Furthermore, a scan, in particular a helical scan, is understood to mean the recording of x-ray projections, in particular two-dimensional x-ray projections, of the patient's tissue from different projection directions, wherein the x-ray system and the patient are constantly moving relative to each other.

A tissue can generally have a plurality of tissue axes, for example three main axes oriented orthogonally to each other. For the helical scan, the patient is oriented or positioned relative to the x-ray system in such a way that the helical scan can be performed along the desired tissue axis.

According to a variant of the invention, the patient lies flat on the examination table, wherein the examination table or at least one part of the examination table is adjusted in height and/or moved transversely to the system axis during the recording of the x-ray projections so that the center The wire or tissue axis moves through the isocenter of the x-ray system. In third-generation computed tomography scanners, the gantry generally does not translate, but is fixed in position. Furthermore, the patient support plate, which receives the patient, for example an examination couch or a patient support table, is adjusted linearly in the direction of the system axis after an initial height adjustment relative to the machine frame. In this variant of the invention, the examination table or at least one part of the examination table is additionally adjusted in height and/or transversely to the system axis during the recording of the x-ray projections in such a way that the center line or the tissue axis moves through the x-rays The isocenter of the system. However, there are also third-generation computed tomography scanners with a “sliding gantry”, in which the gantry is adjusted linearly relative to the height-adjusted examination table during the recording of the x-ray projections. In this embodiment of the invention, therefore, the patient support plate of the examination table does not carry out a linear adjustment movement in the direction of the system axis, but the examination table or at least one part of the examination table only moves vertically and/or transversely to the system axis. to adjust. Mixtures between the two variants are also included in the invention.

According to a further variant of the invention, the x-ray system is adjusted vertically and/or transversely to the patient during the recording of the x-ray projections such that the center line or tissue axis is displaced through the isocenter of the x-ray system. In this embodiment of the invention, for example, a linear movement along the system axis is carried out by adjusting the patient support plate, while the x-ray system or the gantry with the x-ray system is correspondingly adjusted in height and/or transversely to the patient. , so as to match the direction of the centerline or tissue axis. In this case, the movement of, for example, the patient support plate can additionally be adjusted in height and/or laterally. Furthermore, the adjustment movement can only be carried out by the x-ray system according to the sample "sliding gantry", so that in addition to the linear movement of the x-ray system or the gantry also a height and/or lateral adjustment takes place. In this case, hybrid forms between the variants are also included in the invention.

According to one embodiment of the invention, the x-ray system is additionally tilted or tilted about at least one axis running perpendicularly to the system axis during the recording of the x-ray projections. The tipping axis generally extends horizontally (extends in a horizontal plane) relative to the system axis. Tilting or tilting the x-ray system or the gantry with the x-ray system can produce tomographic or cross-sectional images in which the tissue of interest is oriented perpendicular to the center line or tissue axis.

According to one configuration of the invention, prior to the helical scanning with the computed tomography scanner, at least one topogram of the patient is recorded, in which the centerline of the specified tissue or the course of the tissue axis is marked. During the recording of at least one scout, the x-ray system and the patient move only linearly relative to each other. Positioning films are mostly taken from front to back or from the side. However, it is also possible to take a positioning film in both directions. If, for example, a patient's spine is to be scanned, the patient is positioned, for example, on a patient support plate, and when the x-ray system is rotated by 90° from its vertical original position, a positioning film of the patient's spine is taken from the side, wherein only The patient support plate is adjusted linearly in the direction of the system axis relative to the x-ray system. In this case, the centerline of the spine or the longitudinal axis of the spine that describes the double S-shape of the spine can be drawn or marked as the tissue axis for the spine in the positioning sheet. The centerline of the spine is not parallel to the system axis which can also be entered into the positioning sheet and the tissue axis is also generally inclined relative to the system axis.

According to a further embodiment of the invention, the combined displacement adjustment of the x-ray system and the patient takes place as a function of the course of the center line or tissue axis of a given tissue marked in at least one positioning slide. In this case, the deviation of the center line or tissue axis course from the course of the center line or tissue axis is preferably automatically calculated from the course of the system axis and converted into a height adjustment for the patient support plate and/or the x-ray system, for example. control data.

A variant of the invention provides that positions or points are additionally marked relative to the center line or the tissue axis in the at least one positioning piece marking the course of the center line or tissue axis, at which positions or points, X-ray The system should be tilted or tilted relative to the patient so that the X-ray projections of the specified tissue of interest can be taken as perpendicular as possible to the centerline or tissue axis and thus can be generated or reconstructed in a simple manner perpendicular to the centerline or tissue axis orientation tissue slice images.

Preferably, an inclination or tilt angle is also specified or automatically specified or calculated for each marked position, which is set such that an x-ray projection of the specified tissue of interest can be recorded as perpendicularly as possible to the center line or tissue axis.

The technical problem to be solved by the present invention is also solved by a computing program for implementing one of the aforementioned methods, a data carrier with the computing program, and a computed tomography scanner comprising a computing unit with the aforementioned calculation program.

Description of drawings

An exemplary embodiment of the invention is described in the schematic drawing. In the attached picture:

Figure 1 is a computed tomography scanner as well as

Fig. 2 is a positioning film of the patient in Fig. 1 .

Detailed ways

In the figures, identical or functionally identical elements are provided with the same reference signs throughout. The drawings are shown schematically and not necessarily to scale. The computed tomography scanner 1 is described below only to the extent necessary for understanding the invention without limiting its generality.

The computed tomography scanner 1 shown in FIG. 1 comprises a gantry 2 having a fixed part 3 and a part 4 rotatable about a system axis S. As shown in FIG. In an exemplary embodiment of the invention, the rotatable part 4 has an x-ray system with an x-ray source 6 and an x-ray detector 7 which are arranged opposite each other on the rotatable part 4 . Furthermore, the gantry 2 or the rotatable part 4 also has an isocenter IZ which lies on the system axis S and represents the point or midpoint around which the x-ray system rotates. During operation of the computed tomography scanner 1 , an x-ray beam 8 emerges from the x-ray source 6 in the direction of the x-ray detector 7 , penetrates the measurement object and is detected by the x-ray detector 7 in the form of measurement data or measurement signals .

The frame 2 also comprises a base 5 on which the fixed part 3 and the rotatable part 4 of the frame 2 are arranged. The fixed part 3 and the rotatable part 4 of the frame 2 can be tilted or turned together relative to the base 5 about the tilting axis K in the direction of the double-headed arrow a. The tilting axis K of the machine frame 2 is arranged perpendicular to the system axis S and extends substantially horizontally. In order that the fixed part 3 and the rotatable part 4 of the frame 2 can be tilted or tilted relative to the base 5 about the tipping axis K, a support and a support shown schematically in FIG. 1 are provided on at least one side of the base 5. Drive unit 20.

The computed tomography scanner 1 also has an examination table 9 for positioning a patient P to be examined. The examination table 9 comprises a pedestal 10 on which a patient support plate 11 designed to actually receive the patient P is provided. In this exemplary embodiment of the invention, the patient support plate 11 is arranged on the pedestal 10 in such a way that it can be adjusted relative to the pedestal 10 in the direction of the system axis S. As shown in FIG. The patient support plate 11 can thus be guided together with the patient P into a door opening or tunnel 12 of the gantry 2 for recording a two-dimensional x-ray projection of the patient P, for example in a helical scan. Furthermore, in this embodiment of the invention, the pedestal 10 is adjustable in height.

Two-dimensional x-ray projections taken by the x-ray system or reconstructed tomographic images, three-dimensional images or three-dimensional data from the measurement data or measurement signals of the two-dimensional x-ray projections are computationally processed by means of the schematically represented imaging computer 13 of the computed tomography scanner 1 Group.

The computed tomography scanner 1 also has a computing unit 14 connected to the imaging computer 13 , via which computing unit 14 computer programs for operating and controlling the computed tomograph 1 can be executed and executed. The computing unit 14 does not have to be designed as a separate computing unit 14 , but can also be integrated in the computed tomography scanner 1 as the imaging computer 13 .

In this exemplary embodiment of the invention, a calculation program 15 is installed in the calculation unit 14, this calculation program 15 implements a method according to the invention for improving the quality of tissue tomographic images, the central axis or tissue axis of the tissue When the patient is lying flat on the patient support plate, it is not parallel to the surface of the patient support plate or to the system axis of the x-ray system. The computing program 15 here represents a special mode of operation for the computed tomography scanner 1 and can be loaded into the computing unit 14 from a removable data carrier, such as a CD 16 or a memory stick, or from a server 17 via a network 18 . It can be a public network or an internal network of a clinic or hospital.

In this embodiment of the invention, the spine of the patient P needs to be examined, i.e. anteroposterior tomographic images of the spine of the patient P should be generated in the direction of the system axis S, these tomographic images should be of the highest possible and constant quality .

For this purpose, in the method, a localization film of the region of the body of the patient P with the spine is first obtained in a manner known per se. After the patient P is lying on the patient support plate 11 , the patient support plate 11 is adjusted in height by the stand 10 such that the system axis S of the x-ray system extends at least approximately through the spine of the patient P. The surface of the patient support plate 11 and the system axis S of the x-ray system run parallel to one another. As shown in Figure 1, rotate the X-ray system 90 degrees from its vertical home position to a sideways position. In this exemplary embodiment of the invention, the positioning film is taken in the lateral position of the x-ray system, wherein the patient support plate 11 with the patient P is adjusted linearly in the direction of the system axis.

FIG. 2 schematically shows a captured positioning slide 21 as it is shown on display device 22 of computing unit 14 . In this case, the course of the system axis S is now plotted in the positioning plate 21 , which visually shows the spine W. FIG. Furthermore, the centerline M of the spine W and the longitudinal tissue axis G of the spine W are recorded or marked on the positioning sheet 21 , wherein the longitudinal tissue axis G of the spine W registers the double S-shape of the spine W. The marking or recording of the central axis M of the spine W and the longitudinal axis G of the tissue can be carried out manually by means of an input device assigned to the computing unit 14 , such as a computer mouse, or automatically, for example by means of a pattern recognition algorithm.

As is clear from FIG. 2 , the centerline M of the spine W does not run parallel to the system axis S, and the longitudinal tissue axis G is also inclined relative to the system axis S. As shown in FIG. If the patient support plate 11 is only adjusted linearly in the direction of the system axis S, which indicates the position of the isocenter IZ, during a helical scan, as is customary until now, the center line M and the longitudinal tissue axis G will most likely not lie on the isocenter IZ.

For this reason, the distance between the center line M and the system axis S is calculated along the system axis S from the course of the center line M and the known course of the system axis S marked in the positioning sheet 21 and converted by the calculation unit 14 into a control signal for adjusting the patient support plate 11 and the table 10. In this exemplary embodiment of the invention, the system axis S extends in the direction of the z-axis of the Cartesian coordinate system depicted in FIG. 1 and the center line M has an offset relative to the system axis S only in the direction of the x-axis. Therefore, the calculated control signal is a signal related to height adjustment of the pedestal 10 .

In the same way, the distance between the longitudinal tissue axis G and the system axis S is calculated along the system axis S from the course of the longitudinal tissue axis G and the known course of the system axis S marked in the positioning sheet 21 and is calculated by the calculation unit 14 This is converted into a control signal for adjusting the patient support plate 11 or the pedestal 10 . In this exemplary embodiment of the invention, the longitudinal tissue axis G in this case also has an offset from the system axis S only in the direction of the x-axis. The control signals calculated for the longitudinal tissue axis G are therefore likewise only signals relating to the height adjustment of the stand 10 .

In addition, for the center line M in the positioning piece 21, points or points can be specified along the center line M at which the machine frame 2 is to be tilted or tilted about the tipping axis K, in particular such that during a helical scan The x-ray projections are recorded perpendicularly to the center line M by the x-ray system. The user can mark or mark these important positions or position points in the positioning sheet 21 one by one by manually setting the inclination angle or by automatically determining the corresponding inclination angle based on the center line M and the system axis S. From this given information, a corresponding tilt control signal for tilting the frame 2 is generated by the computing unit 14 . However, it is also possible to represent or in this case select the entire center line M, so that during the helical scan the gantry 2 is actually continuously adjusted or tilted according to the course of the center line M and the system axis S. For this purpose, corresponding tilting control signals for a continuous tilting or tilting movement about the tilting axis K are generated for the entire course of the center line M by the computing unit 14 .

In the same way, an inclination angle can be determined for the longitudinal tissue axis G as a function of the longitudinal tissue axis G and the system axis S such that the x-ray projections are recorded perpendicular to the longitudinal tissue axis G. A corresponding inclination control signal can be generated by the positioning plate via the computing unit 14 .

For performing a helical scan, the user can choose between scanning along the center line M or along the longitudinal axis G of the tissue, wherein for both variants there are control signals for the height adjustment of the pedestal 10 and for the tilting of the gantry 2 or the x-ray system control signal.

If the user selects a helical scan along centerline M, the patient support is continuously adjusted in the direction of the system axis S or z-axis as the x-ray system rotates about the isocenter IZ or system axis S in the case of an embodiment of the invention plate 11. This adjustment movement is superimposed on the height adjustment of the pedestal 10 according to the previously calculated control signal, through which the center line M of the spine moves through the isocenter IZ when the patient support plate 11 is adjusted in the direction of the system axis S or the z-axis . At the same time, according to the previously calculated tilt control signal, the gantry 2 or the X-ray system performs a corresponding tilt around the tipping axis K. Due to the wave shape of the centerline M, this corresponding tilt is a continuous tilt along the direction of the double arrow a sports.

Alternatively, the user may choose to scan helically along the longitudinal axis G of the tissue. In this case, the patient support plate 11 is also continuously adjusted in the direction of the system axis S or z-axis during rotation of the x-ray system about the isocenter IZ or system axis S. This adjustment movement is superimposed on the height adjustment of the pedestal 10 according to the previously calculated control signal, through which the height adjustment in turn enables the longitudinal tissue axis G of the spine to move through etc. when the patient support plate 11 is adjusted in the direction of the system axis S or the z-axis. Center IZ. For a helical scan along the longitudinal axis G of the tissue, the gantry is only tilted once according to the calculated control signal and remains in this position during the scan.

In both cases of the helical scan described above, a high-quality tomographic image of the spine of the patient P can be reconstructed by the imaging computer 13 since the central axis M or the longitudinal tissue axis G moves through the isocenter IZ of the x-ray system during the recording of the x-ray projections.

For controlling the method, a graphical user interface is preferably provided, for example on computing unit 14 . Via graphical buttons, for example, it is also possible for the computing unit 14 to calculate, with reference to the system axis S, the control signal for adjusting the height of the stand 10 according to the center line M or the longitudinal axis G of the tissue, and according to the center line M or the longitudinal axis G of the tissue. Compute the tilt control signal. Furthermore, the adjustment of other optional scan parameters and finally the initiation of the helical scan can be carried out in a manner known per se.

In contrast to the above-described exemplary embodiments of the invention, only the centerline of the spine or only the longitudinal tissue axis delineating the spine can be used for the helical scan, so that corresponding control signals are also only generated for the respectively selected variants.

In addition to the lateral positioning slices, at least one further positioning slice can be produced, preferably in the front-to-back direction, in order to be able, for example, to carry out the alignment of the X-ray system and the patient, which may be required due to the corresponding orientation of the center line of the spine or the longitudinal axis of the tissue. The y-directions move relative to each other for lateral adjustment. This means that, in addition to height adjustments, lateral adjustments in the direction of the y-axis are also possible if the center line or the longitudinal tissue axis has a corresponding y-component. If the adjustment motion that causes the centerline or the longitudinal axis of the tissue to move through the isocenter contains an x-component and a y-component, it is generally referred to as a lateral adjustment relative to the system axis S.

The application of the method is not limited to helical scans of the spine. However, other tissues, such as the femur, can also be scanned according to the method. It is not always necessary to tilt the gantry or the x-ray system here. The gantry can also maintain its vertical configuration shown in Figure 1 during helical scanning.

There is also the possibility that the gantry or the x-ray system can also be tilted about another vertically extending axis standing perpendicularly to the system axis and the tilting axis, provided the center line has a corresponding course.

In this embodiment of the present invention, the adjustment movement along each axis direction of the Cartesian coordinate system is implemented by the examination table. However, the adjusting movement can also be realized completely or only partially by the frame, which must be correspondingly adjustable for this purpose.

Claims (8)

1. the method projected for the X-ray of taking patient (P) specified tissue in the helical scanning using computed tomographic scanner (1) to carry out, wherein, have at least one x-ray source (6) and at least one X-ray detector (7) and etc. the x-ray system at center (IZ) and described patient (P) the modulated direction extending past the system axis (S) at the center (IZ) such as described along described computed tomographic scanner (1) when taking X-ray projection move relative to each other, wherein, described tissue of specifying has and carries out along it the centrage (M) that scans or organize axis (G), but described centrage (M) or described organize axis (G) be not parallel to described computed tomographic scanner (1) extend past described x-ray system etc. the system axis (S) at center (IZ), wherein, modulated to carry out combination toward each other mobile for described x-ray system and described patient (P), make described centrage (M) or described organize axis (G) move through described x-ray system etc. center (IZ).

2. the method for claim 1, wherein, described patient (P) lies low on examining table (9), wherein, at least one parts (10 of described examining table (9) or described examining table (9), 11) in height modulated and/or mobile transverse to described system axis (S) when taking the projection of described X-ray, make described centrage (M) or described organize axis (G) move through described x-ray system etc. center (IZ).

3. the method for claim 1, wherein, described x-ray system is in height modulated and/or mobile transverse to described patient (P) when taking the projection of described X-ray, make described centrage (M) or described organize axis (G) move through described x-ray system etc. center (IZ).

4. the method as described in one of claims 1 to 3, wherein, axis (K) inclination that described x-ray system additionally extends around at least one perpendicular to described system axis (S) when taking the projection of described X-ray.

5. the method for claim 1, wherein, use described computed tomographic scanner (1) carry out helical scanning before take at least one spacer (21) of described patient (P), in described spacer (21) specified tissue described in labelling centrage (M) or organize the trend of axis (G).

6. method as claimed in claim 5, wherein, according to labelling in described at least one spacer (21), the centrage (M) of described specified tissue or organize the trend of axis (G) to carry out described combination moving type adjustment.

7. the method as described in claim 5 or 6, wherein, described at least one to mark in described centrage (M) or the described spacer (21) organizing axis (G) to move towards relatively described centrage (M) or describedly organize axis (G) the additionally one or more position of labelling, in this one or more position, described x-ray system should tilt relative to described patient (P).

8. method as claimed in claim 7, wherein, is respectively each regulation inclination angle, position marked.