Source: https://patents.google.com/patent/DE19957082B4/en
Timestamp: 2020-01-27 23:31:07
Document Index: 122690195

Matched Legal Cases: ['arts 8', 'art 9', 'art 9', 'art 9', 'art 9', 'art 9', 'art 9', 'art 9']

DE19957082B4 - Method for examining an area of the body performing a periodic movement - Google Patents
Method for examining an area of the body performing a periodic movement
DE19957082B4
DE19957082B4 DE1999157082 DE19957082A DE19957082B4 DE 19957082 B4 DE19957082 B4 DE 19957082B4 DE 1999157082 DE1999157082 DE 1999157082 DE 19957082 A DE19957082 A DE 19957082A DE 19957082 B4 DE19957082 B4 DE 19957082B4
DE1999157082
DE19957082A1 (en
Thomas Dr.rer.nat. Flohr
Bernd Dipl.-Ing. Ohnesorge
1999-11-28 Application filed by Siemens AG filed Critical Siemens AG
1999-11-28 Priority to DE1999157082 priority Critical patent/DE19957082B4/en
2001-08-02 Publication of DE19957082A1 publication Critical patent/DE19957082A1/en
2004-08-26 Publication of DE19957082B4 publication Critical patent/DE19957082B4/en
Method for examining a body region of an examination object that performs a periodic movement by means of a CT device with an X-ray source rotating continuously about a system axis, from which an X-ray beam penetrating the examination object originates, and a detector system for the X-ray radiation emanating from the X-ray source, the at least a first one and has a last detector line, the object under examination on the one hand and the x-ray source and the detector system on the other hand being displaced relative to one another in the direction of the system axis during the rotation of the x-ray source, and a sectional image of at least that of the detector system's output data corresponding to the detected x-radiation determines the periodic movement-executing body area, comprising the method step that the X-rays q Source is activated and deactivated at least substantially synchronously with the movement in order to emit x-ray radiation in such a way that the x-ray source is activated during a period of the periodic movement to be imaged with the CT device.
The invention relates to a method to examine a periodic movement body region of an examination object by means of a computer tomography (CT) device with a X-ray source rotating continuously around a system axis, from which an X-ray beam penetrating the examination object emerges, and a detector system for that from the x-ray source outgoing x-rays, which has at least a first and a last detector line, being during the rotation of the x-ray source the object under examination on the one hand and the x-ray source and that Detector system, on the other hand, relative to the system axis are shifted towards each other, and by means of an electronic Computing device from those corresponding to the detected X-rays Output data of the detector system is a sectional image of at least the performing the periodic movement body region determined.
The technique of prospective EKG-triggered recording of single slices with single-line CT devices of the 3rd generation (X-ray source and detector system rotate together around a system axis) has been the early 80s known. A characteristic feature of the EKG signal, e.g. the R-wave, used for this, an axial pick-up for one fixed position (z position) of the examination object relative to X-ray source and detector system in the direction of the system axis (z direction) in one perform defined heart phase. After a selectable time delay (in% of the mean RR interval of the ECG signal or absolute in msec) for the preceding R wave is a full circulation or Partial circulation scan triggered. You can the for the image reconstruction at this z-position requires data in several successive rounds be collected to improve the temporal resolution.
For single-line CT devices, i.e. CT machines Detector system has a single row of individual detectors, there is also the possibility the spiral recording with parallel recorded ECG signal stand technology (so-called retrospective gating). Here will be added later the image reconstruction sectional images only from data in allowed Data areas (in the desired heart phase, e.g. in of diastole). This method suffers from single-line CT scanners the not complete Coverage of the volume in the z direction with sectional images. At a Spiral absorption takes place simultaneously with a continuous rotation from x-ray source and detector system around the system axis a relative displacement of X-ray source and detector system on the one hand and examination object on the other in the z direction.
With the introduction of new 3rd generation CT devices with sub-second rotation, i.e. X-ray source and need a detector system for one complete Rotation around the system axis less than a second, and multi-layer technology, i.e. Detector system with more than one line of individual detectors, experienced cardiac diagnostics with CT devices a new upswing. Both EKG-triggered axial recordings as well as spiral recordings with an ECG signal recorded in parallel (retrospective ECG gating) were performed on multi-slice CT devices, i.e. CT scanners expanded with multi-layer technology. Result from the multiple lines with the retrospectively gated spiral examination with suitable Reconstruction techniques also new possibilities, such as e.g. the gapless in the z direction Representability of the cardiac volume in any phase of the cardiac cycle.
Both previously known methods the ECG triggering of individual axial recordings and the spiral recording with parallel recorded ECG signal (retrospective gating), but have a number of disadvantages.
With EKG-triggered axial recordings Radiation is only triggered within the period of time that is actually used for image reconstruction needed Data are recorded. So the method is dose-conscious, it applies only those for Image calculation really necessary x-rays. Indeed will be a sectional image of a layer for each exposure (scan) (for single-line CT devices) or several (in the case of multi-line CT devices) sectional images of slices recorded at fixed table positions. Between two scans Examination object on the one hand and the X-ray source and that Detector system on the other hand, which is fixed during a scan Assume the z position relative to each other, in the new desired z position to be brought. This takes time and is the reason why in the Usually, sectional images are not taken in every cardiac cycle (cardiac period) can be but only every second or third. This extends the Exam time is considerable, and it is often not possible from the entire heart volume in a breath-hold phase of the ones you want thin Winning layers. Moreover arise in multi-slice CT devices Cross-sectional images automatically at a distance of one detector line in the z direction. For qualitative high quality 3D applications, e.g. B. Volume renderings for display of the coronary arteries but the sectional images in the z direction at a smaller distance. A reconstruction of the corresponding Cross-sectional images are not possible with conventional single-layer exposures.
In the case of spiral recordings with multi-line CT devices with an ECG signal recorded in parallel, data is recorded during the entire duration of the spiral recording. Consequently, the patient also irradiated with X-rays during the entire duration of the spiral recording. From the ECG signal recorded during the spiral recording, the data recorded in the desired phases of the cardiac cycle are later (retrospectively) identified and used for reconstruction. This method has the advantage in multi-slice CT devices that sectional images can be reconstructed in any desired heart phase in the z-direction overlapping at arbitrarily small intervals. Due to the continuous relative movement between the examination object on the one hand and the X-ray source and the detector system on the other hand, in multi-slice CT devices it is also possible to cover the entire heart volume in a breathing phase with thin layers. Both points are prerequisites for high-quality 3D representations of the heart.
If you are interested, however only for sectional images of the heart in one phase, usually the resting phase (diastole), spiral images with multi-line CT devices are included retrospective EKG gating not dose-conscious, because although during the entire spiral image of the patient is irradiated with X-rays, under certain circumstances only a small part of the recorded data is actually used for image reconstruction used.
In connection with a reduction in the dose delivered to a patient, it is out of US 5 625 662 It is known to modulate the tube current of an X-ray tube provided as an X-ray source in a CT device as a function of both the angle of rotation of the X-ray tube and weighting factors to be applied to the data obtained at the respective angle of rotation.
In the same context is in the US 5,485,494 described a CT device in which the tube current of an X-ray tube provided as an X-ray source is modulated as a function of the angle of rotation of the X-ray tube according to a stored function, which is preferably obtained on the basis of a test scan of the patient.
The invention is based on the object Specify the method of the type mentioned, in which a periodic movement body area of an examination subject with a reduced dose can.
According to the invention, this object solved by a method with the features of claim 1.
So in the case of the invention for examinations for example the heart in a predetermined heart phase the advantages of prospective triggering (only the really necessary Dose is applied) with the advantages of spiral absorption of a multi-line CT device (complete volume coverage, possibility the overlapping reconstruction of sectional images) connected. This is done during the individual cardiac cycles prospectively triggered with a selectable time delay (in o or as a fraction of an average duration of the RR interval of ECG signal or absolutely in msec) to the previous R wave the ECG signal Full or partial circulation scans triggered, whereby X-rays only during the time for recording the data during of the full circulation or partial circulation scan by means of the multiple detector lines Detector systems (multi-line full circulation or partial circulation data records) applied will, d. H. not only data acquisition, but also X-rays is triggered prospectively by the x-ray source accordingly is activated and deactivated. The relative displacement in the z direction between the object to be examined and the X-ray source and detector system on the other hand, the "Stop and Go "operation for each Scan stopped and only between two scans from az position to the next made, but takes place continuously as with spiral recordings both during of the scans as well in between. You get multi-line Partial or full circulation data in which each projection is a corresponds to another z position. With suitable reconstruction and weighting methods (e.g. projection-dependent weighting between the Data from the individual detector lines) can be made within it one of the feed rate and thus of the so-called pitch dependent area seamless in the z direction Reconstruct sectional images. The feed rate is in dependence on the period of the cardiac cycles, i.e. the heart rate, under consideration the detector width chosen so that in A partial circulation or full circulation data record was recorded for each cardiac cycle can be and that the of successive records covered areas overlap in the z-direction or - in the borderline case - without gaps abut. Then the entire heart volume in the z direction is complete with sectional images coverable. Due to the continuous relative displacement in the z direction between the object to be examined and the X-ray source and detector system on the other hand and the elimination of the discontinuous relative shift required acceleration and deceleration phases can be thus also scanning the entire heart volume in a breath hold phase.
The method of adjusting the feed rate the heart rate is not only for the method according to the invention, but also for conventional ones Multi-line ECG-gated CT spiral images relevant.
According to a variant of the invention is the length of time during which is the x-ray source while a cardiac cycle is activated is greater than the duration of one Time interval during which measurement data be won, i.e. is greater than the duration of a reconstruction interval or data interval. It is the same in the case of fluctuations in the duration of the cardiac cycles (Arrhythmia) ensures that actually the phase of the cardiac cycle to be imaged.
Another variant of the invention stipulates that the temporal course of the EKG signal and the measurement data are stored and taking the measurement data used to determine a sectional image into consideration of the signal selected in this way be that they while of the phase to be imaged. Based on the method according to the invention a retrospective ECG gating can also be performed.
The invention is described below the attached Drawings described by way of example. Show it:
1 2 shows a view of a CT device used to carry out the method according to the invention,
2 a view of the detector unit of the CT device according to 1 .
3 diagrams illustrating the mode of operation of the method according to the invention.
In the 1 and 2 a CT device for performing the method according to the invention is shown schematically.
The CT device has a measuring unit from an X-ray source 1 that have an x-ray beam 18 emits, and a detector unit 2 on which of several in the direction of an axis of rotation 6 successive rows of individual detectors, for example 512 individual detectors each, is composed. The focus of the X-ray source 1 from which the x-ray beam 18 goes out, is designated 24. The examination object, in the case of the exemplary embodiment shown, a human patient 8th , lies on a storage table 20 that extends through the measuring opening 21 a ring-shaped carrier 7 , the so-called gantry.
The detector unit 2 points according to 2 a first line of detectors 3 and a last line of detectors 4 on. Between the first and the last detector line 3 . 4 can be one or, as shown, several other detector lines 5 be arranged.
The detector lines 3 to 5 run at right angles to the axis of rotation 6 , in the 2 is indicated by dash-dotted lines. Parallel to the axis of rotation 6 are the first row of detectors 3 and the last row of detectors 4 spaced apart by a detector width D. The detector width D is measured from line center to line center.
On the carrier 7 are the x-ray source 1 and the detector unit 2 mounted opposite each other such that the X-ray beam emanating from the X-ray source 18 on the detector unit 2 meets. The carrier 7 is about the axis of rotation 6 of the CT device, which represents the system axis, rotatably mounted and rotated for scanning the patient 8th at a speed n around the axis of rotation 6 , This detects that by means of a generator device 22 operated x-ray source 1 outgoing x-ray beam 18 a measuring field 23 circular cross section. The focus 24 the X-ray source 1 moves on one around on the axis of rotation 6 lying center of rotation circularly curved focus path 25 ,
The X-ray beam 18 shines through the patient 8th and that on the detector unit 2 incoming x-rays are detected during rotation at a multiplicity of projection angles α and the output data of the individual detectors for each of the detector rows 3 to 5 combined to form a projection belonging to the respective projection angle α. Each projection angle α therefore includes one of the number of detector lines 3 to 5 corresponding number of projections.
Using the projections recorded by the detector unit during a reconstruction interval, which can comprise several data intervals 2 to an electronic computing device 31 arrive, the latter reconstructs a sectional image of an object to be examined on the basis of known algorithms. In order to be able to reasonably reconstruct sectional images of the examined object, it is necessary to record projections at successive projection angles α, which extend over a reconstruction interval which must be at least 180 ° + β, β being the in 1 illustrated opening angle of the X-ray beam, also referred to as a fan angle 18 is.
The carrier 7 assigned drive 26 is suitable, as mentioned, the carrier 7 to rotate continuously. In addition, a further drive, not shown in the figures, is provided, which causes a relative displacement of the storage table 20 and thus the patient 8th on the one hand and the wearer 7 with the measuring unit 1 . 2 on the other hand in the direction of the axis of rotation 6 with a feed rate v enables.
So there is the possibility of three-dimensional areas of the patient 8th to scan in the form of a spiral recording by the carrier 7 with the measuring unit 1 . 2 rotates continuously and at the same time a relative displacement of the storage table 20 and carrier 7 in the direction of the axis of rotation 6 at a feed rate v.
To conduct investigations of the Areas of the patient's body that are moving to the heart or close to the heart, in rhythm with the heart action 8th instructs the CT device accordingly 1 also a known electrocardiograph 27 on that over electrodes, one of which is in 1 shown and designated 28 with the patient 8th can be connected and for recording the EKG signal of the patient 8th serves in parallel with the examination by means of the CT device. The electronic computing device preferably contains digital data corresponding to the EKG signal 31 fed.
The electrodes of the electrocardiograph 27 are as close to the patient's body as possible 8th attached that they are the patient's examination 8th do not interfere.
To the electronic computing device 31 are a keyboard 29 and a mouse 30 connected, which enable the operation of the CT device.
So much for the patient's body parts 8th There are no noteworthy problems for recording the projections, which can be immobilized. The critical aspect, however, is the recording of projections of a periodically moving object. An example of such an object is the human heart 9 which in 1 is shown schematically.
As is well known, the human heart leads 9 essentially a periodic movement. The periodic movement consists of an alternating sequence of a rest or relaxation phase and a movement or stroke phase. The rest phase lasts between 500 and 800 ms, the beat phase lasts between 200 and 250 ms.
The speed n of the carrier 7 is usually 45 to 120 revolutions / minute. By comparing the speed n with the duration of the resting phase of the heart 9 can be easily determined that the carrier 7 in the resting phase of the heart 9 rotates through an angle of rotation γ which is between 135 ° (500 ms at 45 revolutions / minute) and 576 ° (800 ms at 120 revolutions / minute).
If the speed n is chosen high enough, the carrier rotates 7 during the phase of a cardiac cycle to be recorded, for example during a resting phase, by an angle which is greater than the required reconstruction interval. It is thus possible, during the phase of a cardiac cycle to be recorded, to reconstruct a sectional image of the recorded area of the heart 9 required projections.
The heart rate is so high that it is not possible the to a complete Reconstruction interval belonging Projections during of a single cardiac cycle can occur during the phase of several consecutive cardiac cycles to be recorded in each case respectively. The reconstruction interval is then made up of several belong to different cardiac cycles Data intervals together.
As mentioned earlier, the electrocardiogram 10 of the human heart 9 included to take the rest phases out of it 13 of the human heart 9 to be able to determine.
In the case of the method according to the invention, the EKG signal is used to identify the X-ray source 1 , for example an x-ray tube, to be activated and deactivated in such a way that it only occurs during the phase of a cardiac cycle to be recorded, for example the resting phases of the heart 9 , X-rays emitted. This causes the generator device 22 connected electronic computing device 31 ,
This way the patient's radiation exposure 8th reduced because the application of X-rays is limited to those time intervals, namely the reconstruction or data intervals, in which projections that can be used for image reconstruction are recorded.
This is over 3 can be seen in the level L of the EKG signal labeled EKG of a patient and the intensity I of the X-ray source 1 outgoing X-rays are plotted one above the other over time t. The EKG signal illustrates the periodic movement of the patient's heart, the beginning of a cardiac cycle in each case by an R-wave R and the duration of the respective cardiac cycle by the RR interval T RR , ie: the distance between the R- initiating the respective cardiac cycle. Wave is determined by the R wave that initiates the following cardiac cycle. The resting phase of the heart to be recorded in the example shown is indicated by hatching in each case.
The X-ray source becomes like the course of the intensity I of the X-ray radiation, which changes between zero and an activation value I a 1 activated and deactivated in such a way that it is only activated during the cardiac phase to be recorded, ie the resting phase.
This is done by the x-ray source 1 is activated prospectively, so to speak, by a delay time D P after the occurrence for a period of time T a .
The time period T a during which projections for a full circulation or partial circulation scan are recorded can be a complete reconstruction interval RI or just a data interval DI.
The electronic computing device determines the delay time D P and the time period T a 31 by determining the mean value of the duration of the RR intervals T RR from a preselectable number of previous RR intervals and from this determining the delay time D P and the time duration T a as preselectable percentages or fractions of this mean value. Alternatively, the delay time D P and the time period T a can also be preselected as time periods, for example in milliseconds.
The feed rate v is set by the electronic computing device 31 under consideration consideration of the mean value of the duration of the RR intervals T RR from a preselectable number of previous RR intervals so that the shifting of the storage table occurring during a reconstruction interval RI or data interval DI 20 in the direction of the system axis 6 , ie the relocation of the measuring unit 1 . 2 and the patient 8th relative to each other in the direction of the system axis 6 , a detector width D (see 2 ) does not exceed. The areas of the patient covered by successive reconstruction intervals RI or data intervals DI 8th thus overlap in the direction of the system axis 6 or bump into each other in the borderline case. This is the total volume of the patient scanned in the direction of the system axis 8th can be completely covered with sectional images.
Otherwise, there is also the possibility of retrospectively extracting the projections belonging to a reconstruction interval from the recorded projections if the projections and the EKG signal are stored. This is in 3 by specifying a time interval D R light that the electronic computing device 31 is determined analogously to the delay time D P.
In summary, it can be stated with regard to the method according to the invention that
- It is a recording technique for volume heart and lung examinations with multi-line CT devices, in which the patient bed moves continuously as with spiral recordings, but in contrast to spiral recordings, it is not continuously blasted and measurement data are not continuously recorded, but instead its prospectively triggered with a freely selectable time shift to the previous R wave of the EKG signal, e.g. full circulation or partial circulation multi-line CT scans are triggered, radiation and data being applied only during the duration of the full circulation or partial circulation scan be included
The bed's feed rate is adjusted to the heart rate so that the z-intervals (in the direction of the patient's longitudinal axis) covered by chronologically successive, prospectively triggered full-circulation or partial-circulation multi-line CT data overlap or connect without gaps, so that the entire examination volume is completely covered,
- It enables an adjustment of the bed's feed rate to the heart rate even for retrospectively EKG-gated spiral recordings.
Instead of the EKG signal you can also other physiological parameters or signals are used that information about give the present phase of the cardiac cycle, e.g. Cardiac wall motion or stetoscopic heartbeat analysis.
The invention is above on Example of examinations of the heart explained. But others can also periodically moving body areas with the method according to the invention to be examined.
In connection with the above Description of the invention uses a third generation CT device, i.e. the x-ray source and the detector unit are during the Image generation shifted together around the system axis. The invention can also be used in connection with CT devices the fourth generation, where only the X-ray source around the System axis is shifted and with a fixed detector ring interacts, find use if the detector ring has several Has detector lines
The invention can also except in the Computer tomography on others with penetrating radiation imaging processes are used.
Procedure for examining a periodic Performing movement body region of an examination object by means of a CT device with a X-ray source rotating continuously around a system axis, from which an X-ray beam penetrating the examination object emerges, and a detector system for that from the x-ray source outgoing x-rays, which has at least a first and a last detector line, being during the rotation of the x-ray source the object under examination on the one hand and the x-ray source and that Detector system, on the other hand, relative to the system axis are shifted towards each other, and by means of an electronic Computing device from those corresponding to the detected X-rays Output data of the detector system is a sectional image of at least the performing the periodic movement body region determined, comprising the method step that the X-ray source at least essentially in synchronism with the movement in such a way as to emit X-rays is activated and deactivated that the X-ray source during a with the CT scanner phase of the periodic movement to be imaged is activated.
The method of claim 1, wherein the amount of time while which the x-ray source during a Period is activated, is greater as the duration of a time interval during which measurement data is obtained become.
The method of claim 1 or 2, wherein the the first and the last detector line in the direction of the system axis are separated by a detector width, and in the case of the examination object on the one hand and the X-ray source and detector system on the other hand are displaced relative to one another in the direction of the system axis with such a feed rate that during a time interval, during which, within a period Measurement data are obtained, occurring displacement does not exceed a detector width.
Method according to one of claims 1 to 3, wherein the activation and deactivation depending from a signal corresponding to the periodic movement.
The method of claim 4, wherein the activation the X-ray source each by a first delay time after the beginning of a period of the signal and the deactivation the X-ray source each by a second delay time after the beginning of a period of the signal, the first delay time shorter than the second delay time is.
The method of claim 4, wherein the average duration The activation of the X-ray source is determined in the period of the signal each by a first fraction of the period of the signal after the Beginning of a period of the signal and deactivation of the X-ray source by a first fraction of the period of the signal after the start a period of the signal takes place, the first fraction is less than the second fraction.
Method according to one of claims 2 to 6, in which the temporal Course of the signal and the measurement data are saved and used to determine a sectional image measurement data considering of the signal selected in this way be that they while of the phase to be imaged.
Method according to one of claims 1 to 7, wherein the one periodic movement body area contains the lung of the object being examined.
Method according to one of claims 1 to 8, wherein the one periodic movement body area contains the heart of the object being examined.
The method of claim 9, wherein that of the periodic Movement corresponding signal the EKG signal of the object under examination is.
DE1999157082 1999-11-28 1999-11-28 Method for examining an area of the body performing a periodic movement Expired - Fee Related DE19957082B4 (en)
DE1999157082 DE19957082B4 (en) 1999-11-28 1999-11-28 Method for examining an area of the body performing a periodic movement
JP2000357576A JP2001198121A (en) 1999-11-28 2000-11-24 Method for inspecting body range performing periodic motion
US09/724,057 US6504893B1 (en) 1999-11-28 2000-11-28 Method for examining a body region executing a periodic motion
DE19957082A1 DE19957082A1 (en) 2001-08-02
DE19957082B4 true DE19957082B4 (en) 2004-08-26
ID=7930514
DE1999157082 Expired - Fee Related DE19957082B4 (en) 1999-11-28 1999-11-28 Method for examining an area of the body performing a periodic movement
US (1) US6504893B1 (en)
JP (1) JP2001198121A (en)
DE (1) DE19957082B4 (en)
DE10245943B4 (en) * 2002-09-30 2008-06-26 Siemens Ag Method for generating CT images of a periodically moved organ and CT apparatus for carrying out such a method
DE10308641A1 (en) 2003-02-27 2004-09-16 Siemens Ag Process for the preparation of existing time / phase dependent primary data sets of a computer tomograph from a moving object to a three-dimensional image series
JP4649150B2 (en) * 2003-10-03 2011-03-09 キヤノン株式会社 Radiation imaging apparatus and imaging method
DE10354214A1 (en) * 2003-11-20 2005-06-02 Siemens Ag A method of generating tomographic slices of a periodically moving object having a plurality of focus-detector combinations
DE102005042798A1 (en) * 2005-09-08 2007-03-22 Siemens Ag Operating method for an X-ray machine, operating method for a computer and objects corresponding to these operating methods
DE102007024409A1 (en) 2007-05-25 2008-11-27 Siemens Ag Method and X-ray CT system for generating computed tomographic images
DE102007056801A1 (en) * 2007-11-23 2009-06-04 Siemens Ag CT apparatus and method for spiral scanning of a periodically moving at least in a Teilberich examination object
1999-11-28 DE DE1999157082 patent/DE19957082B4/en not_active Expired - Fee Related
2000-11-24 JP JP2000357576A patent/JP2001198121A/en not_active Withdrawn
2000-11-28 US US09/724,057 patent/US6504893B1/en active Active
JP2001198121A (en) 2001-07-24
DE19957082A1 (en) 2001-08-02
US6504893B1 (en) 2003-01-07