JPH11253435A - Computed tomograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a volume computed tomograph having a plane detector and designed to effect rapid volume computer tomography. SOLUTION: In a computed tomograph, having an X-ray source 1 and a detector which are rotated together for producing tomographic X-ray photographs of a wide subject range simultaneously and for collecting volume data within that range, and having image configuring calculators, a control calculator, and an image output unit, a rectangular or square plane detector 4 is provided as a detector for data collection, the detector 4 covering only a part of the subject angles and effecting data collection within the necessary subject angles relative to the X-ray source 1 through successive zone scans during alternate rotation of the X-ray source 1 relative to the subject range and displacement of the plane detector 4 relative to the X-ray source 1, in which case the plane detector 4 can be displaced in such a way as to follow the rotation of the X-ray source 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a computed tomograph.

[0002]

BACKGROUND OF THE INVENTION For cost reasons, the first computed tomography systems of the seventies were limited to point x-ray sources and a single detector element or a small number of detector elements. The object was correspondingly scanned by one or a few needle beams. In particular, in the first generation systems with a single scanning beam, the translation of the scanning system gives each projection, and the stepwise rotation of the scanning system around the object gives the sum of the projections needed for reconstruction. Was done. Such a scan is also referred to as a parallel beam scan because all the scanning beams of the projection extend parallel to each other in such a system. In order to completely reconstruct the object, a sufficiently fine rastering requires projection from an angle range of at least 180 °.

In order to better utilize the X-ray radiation generated within an X-ray source, a second generation system (US Pat.
In 5 313 513, many fan-shaped beams were measured simultaneously by an array of detectors located side by side. The successively measured central beams of the detector array form a parallel projection. Similarly, the other fan beams form a parallel projection to be incorporated during the projection of the center beam. Reclassification and possibly re-interpolation is referred to in the literature as "Rebinning". The first and second generation systems are also referred to as translation-rotation systems, since basically in both systems the translation of the scanning system and then its rotation take place.

In subsequent developments, a "small fan" was spread over all measurement areas, and all fan projections were photographed simultaneously during the measurement process. Measuring devices with co-rotating X-ray sources and arc detectors are referred to in the literature as third generation systems. There are basically two methods for reconstructing the obtained measurement data: direct reconstruction of the fan projection, re-interpolation in the system of parallel beams and subsequent parallel reconstruction. Is distinguished. All previously discussed systems collect measurement data for the reconstruction of the tomographic plane essentially during rotation by means of a detector array.

[0005] The parallel arrangement of a number of detector rows results in a multi-row or planar detector which, during rotation, allows data acquisition that is spread perpendicular to the slice plane (DE-A 196 18). No. 749, German Patent Application Publication No.
195 15 778, German Patent Application No. 195 32
No. 535). Improved dose utilization and / or accelerated measurement are achieved with flat detectors having relatively small widths. Volume detection without additional couch motion remains limited on a few faults. An expanded volume collection is only possible with such a system during continuous scanning and simultaneous bed feeding (spiral C
T).

[0006] K. Dumling, "A Decade of Computed Tomography-A Retrospective" (electromedica, 52 (19
84), Vol. 1, pp. 13-28), the X-ray source and detector systems are exclusively common to the object unless a fourth generation system is used. Exercise relatively. Alternatively, in a fourth generation system, only the X-ray source is moved, and measurements are collected by a ring of detector elements that are fixedly positioned around the object. Spiral scanning is also possible here.

[0007] Along with computed tomography, even now classical radiography and fluoroscopy,
Two-dimensional array of scintillation detectors with photodiodes, or possibly pre-amplification and AD
A detector array is used that has elements that perform the conversion to perform the direct conversion of gamma radiation to an electrical signal. Such arrays can be used in computer tomography with sufficient quality and at a desirable cost.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to configure a volume computed tomography having a planar detector so that rapid volume computed tomography can be performed.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the object is to provide a detector for data acquisition, which covers only a part of the object angle and which is required relative to the X-ray source. Acquisition of data within the object angle is achieved by successive band scans under alternating rotation of the X-ray source relative to the object area and displacement of the planar detector relative to the X-ray source. This is achieved by providing a rectangular or square planar detector which can be displaced so that it follows the rotation of the X-ray source.

For the computed tomography according to the present invention, the array detector has found wide application in radiography, and such a planar detector system has a suitable form and sufficient It is assumed that it is used with a high quality. The detector system used for radiography replaces the photoplates heretofore commonly used, so that the length and width are adapted to the dimensions of the image. Proposed planar detectors (e.g., having 500 x 300 elements 1 x 1 mm in size) compared to the relatively narrow detector arrays of current multi-row systems (e.g., 40 mm wide for four rows) Allows sufficient coverage of objects perpendicular to the slice (in the z-direction). Therefore, based on its width, such a planar detector is suitable for volumetric imaging without relative movement of the object in the z-direction. However, in a slice such a plane detector can detect only one sub-area of the object.

In order to detect the volume range completely in the slice plane, the detector system and the associated x-ray source stop are movably supported on a single arc around the focal point of the beam source. . The measurement is performed in the band one after another. If the detector is supported by the edge at the start of the measurement, the first rotation scans the outer ring zone of the object. The detector is then displaced toward the center by the length of the partial arc, and then another band of the object is scanned. This process continues until the required object area is scanned for artifact-free reconstruction. The data of the individual bands are combined as a whole data record and processed as tomographic images according to known methods. For second-generation systems, the system according to the invention operates according to the rotation-translation method and differs essentially from known systems due to the different measurement courses.

The computed tomography according to the invention enables a volumetric examination without bed movements by means of the measurement sequence described below for individual organs, such as, for example, the heart, liver and head, and thus a time study (4D) in the organs. Particularly suitable for inspection). Compared to a flat detector of equal width, which extends over all object angles, a particularly economically favorable configuration of the computed tomograph is achieved by means of band scanning.

In accordance with the invention, a corresponding CT control of the detector during the course of the measurement can also take place, as will be explained below, a spiral CT scan over the entire body area. As well as the special properties of a volume CT device, the measuring principle according to the invention is also suitable for the standard recording of radiographic or shadow images with corresponding positioning of the X-ray source and the detector.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings.

As an example, the radiographic display of the entire heart volume by a computed tomography device in a fast image sequence must be solved by a CT system with a band detector. The detector used in this case must completely cover the projection of the heart from all projection directions, but not the entire object angle of the patient. Prior to the original dynamic cardiac study, the patient's outer area is scanned to compensate for incomplete projections and stored temporarily for further processing. Measurement of the entire volume data record is thus possible at each revolution.

In the basic concept, a computed tomograph with a band detector corresponds to a third generation system in which the X-ray source and the detector system move around the object to be measured. The principle is shown in FIG. An overview of the overall system with the image construction computer is shown in FIG.

FIG. 1 shows an X-ray source denoted by reference numeral 1, from which a pyramid-shaped X-ray beam 3 narrowed using a diaphragm 2 starts, and this X-ray beam 3 Corresponds to a flat rectangular or square detector 4. The detectors 4 are each formed from a matrix of detector elements forming an electrical signal corresponding to the received beam intensity.

In FIG. 2, components 1, 2, 4, and 6 preferably have a fuzzy logic, a scanning controller 8, a data memory 9, an interpolator 10, a reconstruction unit 11, a host computer 11 and an image reproducing unit. Is shown in the case of a computed tomograph having a rotating frame for components 1, 4 (gantry) having a monitor 13 of FIG.
Optionally, the system for cardiac imaging is EKG
Complemented by the system 15 for derivation.

In conventional systems with detector arrays curved in rows, the detectors must cover at least half the object angle, ie half the measurement area 6 on one side of the central beam 7. To avoid artifacts, especially at the isocenter of the system, a full fan or a partial fan extending beyond the center is typically used. In contrast, the detector 4 covers only a limited area. The required object angles are successively detected at different positions of the detector 4.

As can be seen from FIG. 1, the detector 4 extends over a wide range in a direction perpendicular to the tomographic plane (z direction) for volume scanning. The dimensions of the detector 4 should correspond to the dimensions of the detector used in radiography or fluoroscopy. With sufficient quality, equal detectors and data acquisition systems can thus be used for radiography and computed tomography according to the invention. As an example, one can start with a detector size of about 50 × 30 cm. It corresponds to a matrix of about 500 × 300 = 150,000 elements for a 1 × 1 mm element size. It starts from such a system with an integrated amplifier and A / D converter.

A measurement system having a measurement area limited in the projection direction (b direction) produces a band image due to partial scanning. The CT value of the ring-shaped band image is distorted compared to the original. In addition, there is an associated marginal area inside and out. These effects are outlined in FIG. To correct for image distortion, the unscanned area must be supplemented by measurements from other rotations.
For this, the detector 4 is moved on a circle around the focal point of the X-ray source 1. In a particular measurement mode, the projection can also be supplemented by an estimate from a previously performed rotation with a corresponding detector position.

The arrangement includes corresponding devices for moving the X-ray flux 3 and the detector 4 and for controlling the movement process. Correspondingly, the diaphragm 2 is also controlled to follow in synchronization with the movement of the detector 4. Appropriate measuring, controlling and regulating devices exist for this purpose. The measuring systems 1, 2, 4 may be movable depending on the measuring device in the stationary gantry, but also during the measuring process. The course of the various measurements is further explained.

The data of the individual rotations collected by the detector 4 are stored in a data memory 9 of the image forming detectors (9 to 11).
It is temporarily stored inside. After the end of the data collection, the projection is assembled as an angled complete projection. The individual measurement ranges are arranged to slightly overlap to avoid transition errors. The data from the overlapping ranges in the interpolator 10 are weighted and integrated according to known methods so that no change in the noise structure in the image occurs.

Due to the spread of the detector 4 in the z-direction, the individual measuring surfaces no longer form a parallel beam in the fan beam but a three-dimensional cone beam. Various methods are known for reconstructing the measurement data obtained by the cone beam.

Due to the non-uniform scanning in the z-direction (different tilts of the beam in the z-direction) among the various projections in the cone beam, correction is always sufficiently good with currently known reconstruction and correction methods. Unacceptable distortion and image artifacts result.

FIG. 4 a shows a schematic of a scan with a central focal point 14.

An even scan, and thus also an improved reconstruction of the entire Voxel volume, is achieved, for example, by the three focuses 1 in FIG.
As shown by 4a, 14b and 14c,
This can be achieved with an X-ray source having many focal points in the z-direction. At that time, it is necessary to place the apertures 2a to 2d before each focal point. The individual foci 14a, 14b, 14c are driven one after the other in a pulsed operation, and the detector 4 then has each focus 1
4a, 14b, and 14c are read separately. The multiple readings increase the amount of data to be reconstructed accordingly. The focus position must be taken into account during reconstruction.

With an X-ray source (FIG. 4c) having a focal point 14d widened in the z-direction and a suitable stop 2e, X-ray radiation can be generated which is directed substantially parallel in the slice. However, it only makes sense to use an X-ray source with a distributed focus. It starts out with a sufficiently fast movement of the cathode ray on the anode that an even quantum flux can be achieved over the entire focal plane. Since the X-ray source operates in a so-called continuous operation, for this operation the detector elements need only be read out once per projection. Since the slices to be measured are decoupled from one another by collimation, the reconstruction of parallel slices in a conventional two-dimensional reconstruction method is simplified. In order to reduce the leakage beam, it may be necessary to place another tomographic collimator 16 in front of the detector 4.

Irrespective of the configuration of the X-ray source 1, the dose can be changed during the measurement revolution. In this way it is possible to adapt the dose to the greatest attenuation in the individual bands. Furthermore, there is the possibility of changing the dose in relation to the projection angle. The integration and interpolation of the projections must then be performed in such a way that no recognizable bands with different noise characteristics occur.

In the case of an object (for example the head) that only partially fills the measurement area, the measurement may remain limited above the object area. This speeds up the entire measurement and protects the patient from unnecessary dose applications.

Following the basic principle, the actual measurement process will be described in more detail. A special method for dynamically examining a volume or body area as well as a method for spiral CT is described, as well as a step-wise full scan of the volume area.

In the volumetric imaging principle diagram (FIG. 3), the whole object angle has five partial ranges a.
Or e. The division is then arbitrarily chosen and depends on the respective size of the available detectors 4. For simplicity of illustration, the sub-ranges are shown without overlapping each other. In a practical embodiment of the method, the detector elements are positioned such that a slight overlap occurs. The possible time course of the measurement is shown in FIG. At that time, the detector 4 is initially located at the edge position a. First
During the third rotation, the band outside the object to be measured is scanned.
Subsequently, the detector array is moved to position b. During continuous rotation, the measuring system then moves further by the angle Da. The detail illustration in FIG. 5 shows that the detector 4 goes through the acceleration and braking phases respectively during its movement.
Radiation may be blocked or continued during the transition, depending on the embodiment. In the latter case, the detector position must be stored along with the data for each projection, along with the angular position of the X-ray source 1, so that the data can be used during reconstruction. After the movement of the detector, the currently set band is scanned during the second rotation. Other bands are scanned in corresponding steps. In the example shown, the condition that at least one half of the object area must be scanned during one revolution is satisfied by the third revolution. To increase the image quality-an even scan of both halves-the method can be continued over the entire object arc (measurement at positions d and e). The indicated course of the measurement shows a possible way of operation ensuring that all necessary data for the reconstruction is collected. Complete sinogram (a
All measurement data for the measurement data display in the / b space) can be measured or another measurement sequence can be obtained by complementation interpolation (mirroring of the measurement beam at the isocenter of the system) It is.

The division of the data acquisition into partial rotations at various detector positions (angle range of the X-ray source <360 °) and the overlapping of the individual bands with different intensities,
Included in the present invention. Overlapping data must be weighted and integrated before reconstruction.

A method for dynamically displaying a sub-range of a four-dimensional fluoroscopic object has particular advantages. The three-dimensional display of the heart or the display of blood vessels, for example during the injection of a contrast agent, and the display of their temporal changes is a special application. The course of the measurement is shown in FIGS. 6a and 6b.

In the example shown, one starts from the fact that the measurement area 6 can be divided into two sub-ranges. In order to measure the inner area 17, the detector 4 is moved
Placed symmetrically with respect to In this way, an entire fan-shaped part is used which is symmetrical with respect to the important inner region containing the actual measuring object. The outer area A1 is additionally measured on one side at the detector 4, which has been displaced during the first rotation, to supplement the projection. Interpolation of the complementarity (exchange of focus and detector position) results in a portion of the projection A2 that is mirrored with respect to the central beam. Detector 4 in the center
After the movement, the actual continuous measurement of the object 5 starts. All the progress is again shown in the time diagram (FIG. 6b).

The object 5 is first located using the shadow image created first, the object 5 and the part to be examined, the heart, are located as centrally as possible in the system, and are completely detected by the detector 4. It is placed to be covered. The continuously collected measurement data is temporarily stored in the data memory 9 (FIG. 2). As an estimate for the outer range, the measured partial projection is firstly supplemented in the interpolator 10 by the determined outer range. At that time, the transition must be corrected again by appropriate interpolation. If the measurements in the outer range change based on the movement of the object 5 (heart phase), it may be necessary to prepare supplementary data records for different phases. The number of supplementary data records is determined by the EKG derivation 15 executed at the same time.

With the projection thus completed, reconstruction of the original inner measuring range can be performed with very high quality.
If the individual tomographic images are reconstructed by applying the accelerated quick scan method to the volume data (180 °
Of parallel data records), in principle (FIG. 6b)
After each half turn a new Voxel data record may be displayed on the monitor 13. With sufficient computing capacity, higher image rates are possible. What is important is that each Voxel data record contains only information from each half-turn, thus allowing a true four-dimensional data representation (space and time) of the course within the object area or organ. .

However, the output speed is related to the available computing power of the image construction computer. If the computing power of the system is not sufficient for online calculations, the Voxel data records can be post-calculated and subsequently output on the monitor 13 in real time.

It is often not possible to look at every Voxel data record in order to observe the dynamic course in an organ. Thus, besides the original slice, the online MPR slice (multiplanar reconstruction) and / or the online shaded surface (immediately calculated shaded surface image) can also be displayed on the monitor 13 for diagnosis.

Spiral Volume Imaging Even though the special use of the computed tomography according to the invention lies in the dynamic examination of organs, such a computed tomography system also allows efficient spiral examination in whole body mode. For this purpose, according to FIGS. 7 and 8, the detector 4 is activated in alternating positions during the rotation of the measuring system. In order to scan the volume as evenly as possible, it is necessary to divide the rotation into smaller areas. Starting from an even division of the rotational trajectory, it may be achieved, for example, in a division into three segments, to alternately scan the inner and outer detector positions at equal angular positions a from rotation to rotation. The chain line in FIG. 7 indicates the course of the center of the detector array 4.

When the measurement area is divided into two bands as in the present invention, only half of the required data is obtained on average. This allows the detector 4 to be moved in the z-direction by a maximum half width during rotation. Utilizing the maximum possible movement in the example shown in FIG. 8, from the sinogram (α / β-diagram) and the accompanying z-movement in the α / β-diagram, the It can be seen that all regions can be replaced by corresponding positions from the leading (x) and trailing (+) rotations.

However, the disadvantage is that different tilting of the measuring beam in the z-direction occurs in a measuring system with only one concentric focus. Z per rotation
In the example shown with half the detector shift in the direction,
For example, the element measured directly at the edge of the detector has the largest tilt angle, while the values captured from the center of the detector have little tilt angle. Switching the tilt angle inside the projection can lead to artifacts in the image. By reducing the displacement over a linear portion of the detector width, the cone effect is mitigated by averaging data measured at the same location with different tilt angles. In part, measurements with opposite angles are also compensated. When relatively small in the z-direction, and thus during multiple scans of the volume, the measured values to be captured are located side by side. Correspondingly, the detector array can remain in one position (band) over a longer a-angle range. The switching of the bands after one and a half turns in each case seems to be meaningful in that case.

Different tilts of the beam are a common problem of spiral reconstruction in flat detectors. Known cone-beam reconstruction methods have to be adapted for systems with a band detector 4. In a simplified view, the reconstruction can therefore be considered as a function of the band measurement, later decomposing the image result into a partial reconstruction to be added.

For spiral CT applications, embodiments having a distributed focus (see FIG. 4c) and a collimating beam stop are particularly advantageous. This is because no cone problem occurs in this case.

Another problem with the above simple division of the measuring rotation is that the transition from the outer measuring range to the inner measuring range is
As will be immediately recognized in FIG. 7, this always occurs at the same angular position. FIG. 9 illustrates a system that divides each two rotations into five sections. Thereby, it is achieved that the transition point switches from rotation to rotation and can be corrected by interpolation.

The examples of spiral measurements shown in FIGS. 7, 8 and 9 show that the computed tomography according to the invention is generally suitable for spiral measurements. Numerous courses with transitions at different angular positions and with different degrees of overlap are possible by reducing the pitch of the spiral, both for the measuring range (band) and for the multiple scans, and are included in the present invention. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic principle of a volume computed tomography according to the present invention.

FIG. 2 is a schematic diagram of a gantry having a band detector and a volume CT system having the main components of an image construction computer.

FIG. 3 is a diagram showing the generation of band images and their edge regions by partial scanning.

FIG. 4 shows an X-ray source with differently configured focal points (single-focus X-ray source, multifocal X-ray source, and X-ray source with distributed focus).

FIG. 5 is a diagram showing a measurement process at the time of volume measurement without moving the couch.

FIG. 6 is a diagram showing a measurement process during dynamic measurement (four-dimensional heart imaging).

FIG. 7 shows a spiral CT scan as an example of a simple division of the measurement into three sub-ranges per rotation.

8 is a diagram showing a measurement progress at the time of spiral CT imaging in FIG. 7;

FIG. 9 is a diagram showing an optimized measurement process in spiral CT.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray source 2, 2a-2c Aperture 3 X-ray beam bundle 4 Detector 5 Object 6 Measurement area 7 Central beam 8 Control computer 9 Data memory 10 Interpolator 11 Image construction computer 12 Image output unit 13 Monitor 14, 14a １４14d Focus 15 System for EKG derivation 16 Tomographic collimator near detector 17 Inner measurement range

Claims (34)

[Claims] An X-ray source (1) and a detector, image arrangement, co-rotated for simultaneously producing a tomographic radiograph of a large object area and collecting volumetric data within this area. In a computed tomograph having a computer (9-11), a control computer (8) and an image output unit (12), as a detector for data acquisition, only a part of the object angle is covered and the X-ray source (1) In comparison, the acquisition of data within the required object angle is achieved by alternating rotation of the X-ray source (1) relative to the object area and relative to the X-ray source (1). A band scan is performed one after another under the displacement of the plane detector (4), wherein the plane detector (4) is displaceable so as to follow the rotation of the X-ray source (1). Plane detector (4) is provided. Computer tomograph characterized by the above-mentioned. 2. A computer tomograph according to claim 1, comprising a flat detector (4) or a flat detector (4) curved corresponding to one circle around the focal point. 3. The X-ray source diaphragm (2), wherein the plane detector (4) is displaced relative to the X-ray source over one circular arc around the focal point (14) of the X-ray source (1). 3. The computed tomography device according to claim 1, wherein the at least one of the detectors is oriented at a respective position of the detector. 4. A tomograph according to claim 3, wherein a control and adjustment device (8) is provided for positioning the detector (4) and the diaphragm (2). 5. The tomograph according to claim 4, wherein the control and regulating device comprises fuzzy logic. 6. The tomograph according to claim 1, wherein the partial projection is supplemented by a detector (4) shifted by a measurement resulting from the rotation. 7. The supplementation of projections is performed by means of estimates from predetermined partial projections.
The described computer tomograph. 8. The computer tomograph according to claim 6, wherein data from overlapping measurement ranges are combined by weighted interpolation so that a change in a noise pattern in the CT image does not occur. 9. For cross-sectional images and Voxel calculations,
9. A tomograph according to claim 1, wherein an algorithm for reconstructing the cone beam projection is used. 10. An X-ray tube with multiple focal points (14a to 14c in FIG. 4b) is used to scan the volume range more evenly, and a corresponding reconstruction method for superimposed cone beam projection is suitable. 10. The computed tomograph according to claim 1, wherein the computed tomography is applied starting from a different focus. 11. The method according to claim 1, wherein an X-ray tube having a focal point (14d in FIG. 4c) distributed in the z-direction (perpendicular to the slice plane) is used. The described computer tomograph. 12. A collimator (2e) for generating parallel fan radiation in a number of planes is placed in front of the X-ray source (1) or integrated in the X-ray source. The computer tomograph according to claim 11, wherein: 13. The computed tomography according to claim 12, wherein the tomographic image and the Voxel data are reconstructed in mutually independent tomograms. 14. Computer tomograph according to claim 12, characterized in that an additional tomographic collimator (16) is arranged in front of the detector (4). 15. The computed tomograph according to claim 1, wherein the dose for the individual measurement zones can be varied according to the maximum attenuation occurring in the zones. 16. The computed tomograph according to claim 15, wherein the dose can be additionally changed in relation to the projection angle (α). 17. The measurement sequence is such that the bands are measured at successively different detector positions (a to e), and the measurement data is the complete sinogram (36) for all simultaneously measured faults.
Projections from an angle range of 0 ° and projections spread over all object angles), and are controlled so that a cone beam reconstruction is performed (FIG. 5). Item 17. A computer tomograph according to one of Items 1 to 16. 18. The measurement sequence is characterized in that the bands are measured at successively different detector positions (ac) and the measured data is a partial sinogram (36) for all simultaneously measured slices.
Projections from an angle range of 0 °, and projections extending to half the object angle plus symmetrical parts)
17. Computer tomograph according to one of claims 1 to 16, characterized in that the cone beam reconstruction is controlled subsequently (Fig. 5). 19. The measurement sequence is characterized in that the bands are measured at successively different detector positions (ac) and the measured data are part-sinogram (3) for all simultaneously measured slices.
Projections from an angle range smaller than 60 ° and projections spread over all object angles), and then controlled to perform a cone beam reconstruction (FIG. 5). A computer tomograph according to one of the preceding claims. 20. The computed tomograph according to claim 17, which has a simple tomographic reconstruction for parallel slices in the distributed focus and volume. 21. In order to dynamically display a sub-region of the object (5), the measurement sequence is preliminarily scanned over the outer region of the object (5) and subsequently in a continuous measurement. Computer tomograph according to one of claims 1 to 20, characterized in that only the sub-range is measured and that the partial projection is supplemented by an estimate from the outer range (Fig. 6). 22. The outer region is measured and stored a number of times corresponding to the movement phase of the object to be displayed, and then the movement data is derived (eg EK) when measuring in the inner region.
22. The computed tomograph according to claim 21, wherein the respective outer region is used for supplementing the measured data in accordance with (G derivation). 23. The method according to claim 21, wherein the outer region is measured and the mirror region is generated by complementary interpolation (FIG. 6b).
2. The computer tomograph according to 2. 24. For reconstruction, only data records from a projection angle range of about 180 ° are used, a complete Voxe describing the volume to be examined for each half-turn.
23. A computer tomograph according to claim 21 or claim 22, wherein one data record is generated (Fig. 6b). 25. Computer according to claim 21, wherein the image construction computer (10, 11) is arranged such that a complete Voxel data record is generated and displayed in synchronization with the scanning. Tomograph. 26. In addition to the calculation of the Voxel data record, simultaneously a cross section through the sub-area of the object (5) to be examined and the shading of the part of the object (5) or the organ to be examined. The attached surface is the image configuration computer (1
Computer tomograph according to claim 21 or 22, characterized in that it is calculated in (0, 11) and displayed on a monitor (13). 27. The additionally calculated cross-section and surface image are displayed at a pace from the already scanned area and are respectively enlarged (growing MPR) by measuring slices and continuing reconstruction. 27. The method according to claim 26, wherein
The described computer tomograph. 28. The object (5) is moved relative to the measuring system surface and all detectors (4) are fixedly shifted systematically between predetermined positions, so that all 27. A spiral scan, which provides sufficient measurement data for the reconstruction of tomographic images or Voxel data within the helix region, is achieved.
A computer tomograph according to one of the claims. 29. The range in which the measurement rotation is not occupied by the measurement system (1, 4) during the maximum possible movement (z-direction) of the object (5), respectively, from the measurement from the preceding or subsequent rotation. 29. The system according to claim 28, characterized in that it is set so that it can be replaced by measured values from the correct position.
The described computer tomograph. 30. The object (5) is moved by the measuring system (1, 4) at a speed lower than the maximum possible speed, and the overlapping measured data are summed by weighted interpolation, and the cone beam reconstruction method is performed. 29. The computer tomograph according to claim 28, which is processed according to the following. 31. A computer tomograph according to claim 29, wherein all the acquired measurement data are processed according to a cone beam reconstruction algorithm. 32. Measurements from individual detector positions (bands) are calculated separately as tomographic images or Voxel data according to the cone-beam reconstruction method, and subsequently the images with partial information are combined. 31. The computer tomograph of claim 29 or claim 30. 33. A distributed focal point (X-ray emission), which results in a fan-shaped X-ray emission extending parallel to the measurement system plane, so that two-dimensional reconstructions can be used to calculate tomographic and Voxel data. 14d) and the collimator (2
31. A computed tomograph according to claim 29 or 30, wherein an X-ray source (1) having e) is provided. 34. One of the claims 1 to 33, wherein instead of individual computing mechanisms and special memories, programmable or parallel computers are used to carry out the various processing steps. Computer tomograph described in one of the above.