JP3512874B2 - X-ray computed tomography equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray computed tomography apparatus (hereinafter abbreviated as CT), and more particularly to a CT capable of continuously performing a scanning operation.

[0002]

2. Description of the Related Art Generally, in CT, three processes of scanning, image reconstruction and image display are performed in time series. Multi-directional projection data collected by rotating the X-ray tube or rotating the X-ray tube and the detector array together is digitized and subjected to preprocessing such as calibration, and then used as raw data such as a magnetic disk. Once stored in the mass storage device.

At the time of reconstruction, raw data is read from the magnetic disk and sent to the reconstruction unit via the memory.
The tomographic image data reconstructed by the reconstructing unit is stored in the magnetic disk and transferred to the CRT monitor as a video signal via the display memory and displayed.

By the way, the introduction of the slip ring has enabled continuous scanning. With this continuous scan,
It has become possible to collect multiple multi-directional projection data for the same or multiple slices in time series. These multi-directional projection data have been read by the reconstruction unit via the magnetic disk at an arbitrary timing as described above and used for reconstruction. The time required for this reconstruction processing is longer than the scan time, and the storage and access time of the magnetic disk is long. Therefore, it was not possible to continuously display a tomographic image like a cine image while executing continuous scanning.

In recent years, high-speed reconstruction processing has been studied and is about to reach practical use. This is expected to display tomographic images continuously in real time, like cine images, while performing continuous scanning.
A long storage and access time of the magnetic disk has been an obstacle to practical use. Furthermore, the waiting time during storage and access to the magnetic disk is irregular, so the time interval from the scan operation to the display of the tomographic image is irregular, and the actual movement of the subject is reproduced. I couldn't.

In addition to this, when the real-time X-ray CT is used in a clinical setting, the following various problems occur. The first problem is that the operator usually adjusts the slice position by manually sliding the tabletop while watching the cross light projected from the projector onto the subject, but this operation requires a long time. The second problem is that in a scan involving movement of the tabletop such as a helical scan or a multi-slice scan, if the scan is temporarily interrupted, it takes a long time to restart. This is because when restarting, it is necessary to manually return the top plate to the slice position of the display image at the time of interruption.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned circumstances, and an object thereof is to provide an X-ray computed tomography apparatus capable of displaying the actual movement of a subject in real time during scanning. It is to be.

[0008]

[0009]

[0010]

SUMMARY OF THE INVENTION The present invention exposes X-rays to radiation.
X-ray detection for detecting X-rays transmitted through X-ray tube and subject
And the X-ray tube has a spiral orbit when viewed from the subject.
A helical scanning means for scanning as drawn,
A data collection means for the X-ray detector continuously acquire projection data from the data of X-rays detected, in parallel with the collection of the projection data, projection angle range required to generate a single image
The projection time acquired by the scan operation is shorter than the time required for the scan operation to collect shadow data.
An image reconstructor that reconstructs image data based on shadow data and sequentially repeats it to obtain a series of image data.
In parallel with the step, and the collection of the projection data, said one after another again
The configuration image data is a computer tomography apparatus characterized by comprising a table Shimesuru display unit after a predetermined time from the scanning operation to respond each pair.

[0011]

[0012]

[0013]

[0014]

[0015]

According to the present invention, the multi-directional projection data in a shorter time than the time required for the scanning operation might have to reconstruct the based-out images data, even images data from the scanning operation deer
Since display after a certain time, without it becomes impossible to time interval between the display of the scanning motion or al picture image reproducing the actual motion of the subject becomes irregular, real-time
In it is possible to continuously displayed as cine images the images.

[0016]

[0017]

[0018]

[0019]

[0020]

Embodiments of the X-ray computed tomography apparatus according to the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 2 is a schematic diagram showing the structure of the first embodiment. The X-ray computed tomography apparatus according to this embodiment includes a gantry 1, a bed 2, and a console 3. An opening 4 into which the subject is inserted is provided in the center of the gantry 1. A bed 2 is arranged on the front surface of the gantry 1. The bed 2 is configured to be electrically adjustable in height. Sleeper 2
A top plate 5 on which a subject is placed is provided on the top surface of the table, and the top plate 5 is configured to be capable of being electrically slid from the top surface of the bed 2 toward the gantry 1. Although not shown, casters or the like are attached to the lower part of the gantry 1, and the gantry 1 can be manually slid toward the bed 2. This is because CT fluoroscopy is sometimes used in combination with surgery,
In this case, it is preferable in terms of safety to change the slice position by moving the gantry 1 rather than moving the top plate 5. Of course, the slice position can be changed by sliding the top plate 5. In the shooting mode, it is common to change the slice position only by sliding the top plate 5.

A keyboard (which may include a mouse) 6 and a CRT monitor 7 are arranged on the console 3, and a controller is housed in the console 3. This control unit is connected to both the gantry 1 and the bed 2.

Inside the mount 1, as shown in FIG.
The X-ray tube 12 that irradiates the subject 10 placed on the fan-shaped X-ray beam, and a plurality of detectors arranged in an arc shape around the focus of the X-ray tube 12 The detector array 16 for detecting the X-rays transmitted through the multi-channel is supported by the rotating unit so as to be able to continuously rotate around the subject 10 while facing each other with the subject 10 interposed therebetween. . Further, the X-ray tube 12 and the detector array 16 are electrically connected to the fixed portion via a slip ring. As a result, the X-ray tube 12 and the detector array 16 continuously rotate around the subject 10,
Multi-directional projection data on the subject 10 required for reconstruction of one tomographic image can be continuously collected, and when continuously rotating at the same slice position, for example, a slice due to inflow and outflow of a contrast agent is used. So-called dynamic scanning is possible to track changes in the image, and so-called helical scanning is possible when the slice position is changed in synchronization with rotation. Note that this type of CT is called the so-called third generation (R / R system). The pedestal 1 is not limited to this type, and may be a so-called fourth generation (R / S system) in which detectors are arranged around the subject over 360 ° and only the X-ray tube 12 rotates. In addition to the detector, the X-ray tube 12 may be a so-called fifth generation (S / S system) arranged around the subject over 360 °.

An X-ray generator 14 for supplying a tube current and a tube voltage to the X-ray tube 12 for generating X-rays is installed on the fixed part of the gantry 1 through a slip ring. Connected to the X-ray tube 12. This X-ray generator 14 can also be mounted on the rotating part of the gantry 1. A data acquisition system (DAS) 18 is installed on the rotating part of the gantry 1.
It is connected to the detector array 16. The data acquisition system 18 includes an integrator that temporally integrates the output signals from the detectors of the detector array 16, a multiplexer that captures the output of the integrator at high speed and serially in units of channels, and the multiplexer. It is composed of an analog-digital converter or the like for converting the output signal of 1 to digital and collects and outputs the projection data reflected in the X-ray transmittance of each X-ray path.

FIG. 4 is a block diagram of the control unit 20 in the console 3. A CPU 22 as a host controller is provided, and a control bus 24 and a data bus 26 are connected to this CPU 22. The CPU 22 has a built-in clock circuit 42, uses the clock from the clock circuit 42 to manage the operation and time of each unit, and supplies this clock as a common clock to each unit in the control unit 20. The control bus 24 includes a preprocessor 28 and a disk interface (disk I / F) 3
0, the reconstruction unit 32, and the display memory 34 are connected. The control bus 24 includes the keyboard 6 and the X described above.
The line generator 14 is connected. A preprocessor 28, a disk I / F 30, a reconstruction unit 32, a display memory 34, and a memory 36 are connected to the data bus 26. Disk I / F
30 is a magnetic disk device 38 as a mass storage device
Are connected. The data collection system 18 is connected to the preprocessing unit 28. The projection data from the data collection system 18 is subjected to preprocessing such as calibration by the preprocessing unit 28, and then temporarily written as raw data in the readable / writable memory 36 such as DRAM via the data bus 26. It is read from here and sent to the reconstruction unit 32. The reconstruction unit 32 reconstructs tomographic image data based on multidirectional projection data. This tomographic image data is once written in the display memory 34 such as a readable / writable DRAM, and is further read from here to the CRT monitor 7 and displayed as a tomographic image. The tomographic image data is read from the display memory 34 and stored in the magnetic disk device 38 via the disk I / F 30.

Next, the operation of this embodiment will be described. Figure 1
Is a flow chart of the perspective mode. FIG. 5 is a diagram showing a schematic flow from scanning in the perspective mode to display. . In the present embodiment, as described above, the operation modes include the perspective mode and the photographing mode, and one mode is selectively set according to the operator's instruction input via the keyboard 6. When the operation is started, the continuous rotation of the X-ray tube 12 and the detector array 16 is started in step # 10, and the continuous scan is started. The continuous scan is defined by continuously repeating the scan operation. The scanning operation means the X-ray tube 12 and the detector array 16
And are rotated, and are defined by collecting projection data in multiple directions required to reconstruct one tomographic image.
The slice position may be fixed or may change during successive scans. As will be described later, according to the present embodiment, data collection, image reconstruction, and display are performed at high speed as a series of operations, and the reconstruction operation is performed from the scan operation time for collecting projection data for one sheet. Since the time interval (time difference) until the tomographic image is displayed is constant for all scan operations, the time interval from the scan operation to the display of the tomographic image is the waiting time for writing and reading to the memories 34 and 36. It is possible to display a tomographic image like a cine image almost in real time without being unable to reproduce the actual movement of the subject 10 in real time due to irregularity due to the presence or absence of time. This fluoroscopic mode is performed, for example, in order to confirm that the tip of the puncture needle has reached the tumor portion during the puncture treatment by continuously displaying tomographic images while continuously scanning. In this case, the slice position during continuous scanning is fixed. It can also be used for positioning the slice position for normal imaging, but in this case it is considered necessary to change the slice position freely. This change in slice position may be made by sliding the top plate 5, but when using the fluoroscopic mode during surgery, it is not preferable to move the patient to which various tubes and equipment are attached, so the gantry 1
It is desirable to change the slice position by sliding. In this case, it is preferable that the gantry 1 is provided with a power assist mechanism so that the doctor can move manually easily. Further, the change of the slice position in the perspective mode does not have to be a constant speed as in a normal helical scan, and the stop and movement may be repeated irregularly or the speed may be changed.

During the scanning operation, the projection data collected and output by the data collection device 18 is subjected to preprocessing such as calibration by the preprocessing unit 28, and then sequentially written in the memory 36 as raw data. For example, the rotation speed of the X-ray tube 12 and the detector array 16 is 1 second / revolution, and the period (50 seconds) in which the X-ray tube 12 and the detector array 16 rotate 50 times is determined for one continuous scan. This period is set so as not to exceed the allowable time determined from the viewpoint of the heat resistance of the X-ray tube 12 and the safety of the subject 10 against exposure. The memory 36 has a storage capacity of about 100 MB, assuming that 2 MB of raw data is collected by one rotation so that all raw data for one continuous scan can be stored. Further, the display memory 34 has a storage capacity capable of storing a plurality of tomographic image data obtained by one continuous scan.

At step # 12, it is determined whether or not the raw data necessary for reconstructing one tomographic image data is collected.
It is determined by PU22. If collected, step #
At 14 this raw data is transferred from the memory 36 to the reconstruction unit 32. The scan operation is continuously continued. Since the raw data is sent from the data collection device 18 to the reconstruction unit 32 via the memory 36, the time from the scan operation to the start of the reconstruction process is significantly shortened as compared with the case of using a magnetic disk having a long access time. It became possible to do. Conventionally, since all raw data was temporarily stored on a magnetic disk and then read and reconstructed in a vacant time, it takes a long time from the scan operation to the start of the reconstruction process, and real-time property is required. Couldn't get

Further, the processing time of the reconstructing section 32 is high speed processing which is shorter than the scanning operation (data collection time). As a result, the time difference between the completion of reconstruction of the tomographic image with respect to the scanning operation, specifically, the reconstruction using the data from the time when the collection of projection data necessary for reconstructing one tomographic image is completed It is avoided that the time difference until the time of completion is cumulatively increased each time the scanning operation is repeated. In this high-speed processing, the reconstruction unit 32 connects a plurality of processors in parallel and reconstructs by dividing raw data for each view or for each channel (generally one detector corresponds to one channel). The process proceeds in parallel. By increasing the number of parallel processing,
The processing speed can be increased. Also, the processing speed can be increased by speeding up the clock.

In order to realize high-speed reconstruction processing, it is also adopted in the present embodiment that the number of views per 360 ° (one rotation) is reduced (thinned or bundled). For example, during normal imaging, the projection data of 900 views / one rotation is collected, that is, the data collection device 18 repeats the data collection for 900 cycles during one rotation.
In the perspective mode, data collection is repeated at 450 views / one rotation. If this is done, the spatial resolution of the tomographic image is reduced, but the purpose of the fluoroscopic mode by continuous scanning is to immediately see the movement of the subject 10 in a state close to real time, and a tomographic image with high spatial resolution is captured. Since the image can be taken in the mode, there is no problem that spreads from the deterioration of the spatial resolution. Furthermore, in order to shorten the reconstruction time, the number of pixels (the number of pixels) at the time of reconstruction may be reduced. In the normal shooting mode, one tomographic image is reconstructed with a size of 512 × 512 pixels,
It is displayed in that size, but in perspective mode, 256
The time can be shortened by reconstructing with a size of 256 pixels and interpolating at the time of display to increase the number of pixels to 512 × 512 pixels.

Further, although the tomographic image is repeatedly reconstructed in the continuous scan, if one tomographic image is reconstructed by one rotation and the next one tomographic image is reconstructed by the next one rotation. If the rotation speeds of the X-ray tube 12 and the detector array 16 are 1 second / revolution, the tomographic image is reconstructed at a rate of 1/1 / second. In this embodiment, in order to increase the reconstruction rate, the technique described in Japanese Patent Laid-Open No. 4-266744 may be adopted. This is because the X-ray tube 12 and the detector array 16 have a small angle α ° (for example, α ° = 10).
°) Each time it rotates, partial images are reconstructed one after another from projection data for 10 °. Then, by adding 36 partial images for 360 °, one complete tomographic image for 360 ° is created. Furthermore, once one tomographic image has been created, the latest partial image is added to this tomographic image,
And the subtraction of the oldest partial image from the tomographic image is repeated. As a result, new tomographic images are created one after another every 10 ° rotation, and it is possible to continuously acquire tomographic images at a high reconstruction rate. Further, in order to increase the reconstruction rate, the technique of Japanese Patent Application No. 1-213136 may be adopted. With this technique, reconstructed image information is obtained by back projection from a group of projection data for one image. Then, the difference data between the latest projection data obtained immediately after this group of projection data and the projection data in the group corresponding to the projection data immediately after this group is further backed up to the reconstructed image information. Project. As a result, it becomes possible to create the next reconstructed image information that is deviated in time at high speed. The basic idea of any of these techniques is to sequentially update the tomographic images that have been reconstructed, and other techniques that spread from this concept may be adopted to increase the reconstruction rate.

When the reconstruction is completed, the tomographic image data is written in the display memory 34 in step # 16. C until the next tomographic image is reconstructed and displayed
In order to display the current tomographic image on the RT monitor 7 in a frozen state, the current tomographic image data is repeatedly read from the display memory 34 at a constant cycle, and the read data is transferred to the CRT monitor 7. Such a display system is the same as the cine display in the X-ray imaging apparatus. Note that if the next tomographic image data is written while the display memory 34 is being read, the information will be different between the top and bottom of the image, so it is necessary to wait for the writing during the reading.

At step # 18, it is determined whether or not one continuous scan is completed, that is, 50 after the scan is started.
The CPU 22 determines whether the seconds have elapsed. In the case of no, the process returns to step # 12 and waits until the collection of the data necessary for the reconstruction of the next one tomographic image is completed. If one continuous scan is finished, step #
At 20, the raw data in the memory 36 is stored in the magnetic disk 38. If it is not necessary to store the raw data, step # 20 may be omitted. In step # 22, it is determined whether or not the next continuous scan is to be performed. If yes, the process returns to step # 10, and if not, the process ends.

Since the raw data for at least the last one continuous scan is stored in the memory 36, when it is desired to display a tomographic image again after the end of continuous scan,
The raw data read from the memory 36 may be reconstructed.
As described above, since the tomographic image can be observed almost in real time in the fluoroscopic mode, it may be used as a support image for surgery during surgery such as puncture. However, the operator often cannot observe the monitor during the operation, and the assistant gives various instructions to the operator (doctor) while looking at the assistant. However, the doctor may want to see the progress of the puncture after the end of one continuous scan, and after the end of the continuous scan, the final tomographic image is frozen and read out from the memory 36 when the doctor gives an instruction. It can be viewed by reconstructing the raw data and displaying the images frame by frame.

Next, the operation from data collection to display of one piece of tomographic image data will be described in detail. FIG. 6 is a time chart showing this operation. While the X-ray tube 12 and the detector array 16 rotate around the subject 10, projection data is output from the data acquisition system 18 at every minute angle.
This projection data is sequentially written in the memory 36 as raw data via the preprocessing unit 28. After all projection data for all angles (0 ° to 360 °) necessary for reconstructing one tomographic image is written in the memory 36, the projection data is read from the memory 36, and the reconstruction unit 32 Transferred to. The reconstruction unit 32 reconstructs the tomographic image data at a high speed, that is, in a shorter time than the data acquisition time, and writes it in the display memory 34. During this time, the magnetic disk 38 is not accessed. The tomographic image data is read from the display memory 34 and sent to the CRT monitor 7 for display. As described above, the reading of the tomographic image data from the display memory 34 is repeated until the next tomographic image is displayed.

Here, what is important for real-time cine display (moving image display) is not only shortening the time from the scanning operation to displaying the tomographic image, but also faithfully reproducing the speed of movement. For example, switching and displaying two tomographic images, which have been collected at 1-second intervals, at 1.1-second intervals does not reproduce the actual movement. In the present embodiment, as shown in FIG. 7A, from the time when the scanning operation for one tomographic image is completed (the time when the data acquisition is completed),
By making the time difference Δt until the display start of the tomographic images constant for all the tomographic images I1, I2, I3, in other words, as shown in FIG. 7B, the tomographic images I1, I2 are shown.
Are displayed at intervals equal to the interval Δt1 of each scan operation, and the tomographic images I2 and I3 are displayed at an interval Δ of each scan operation.
By displaying tomographic images at an interval equal to t2 and then sequentially switching and displaying tomographic images with a time difference equal to the interval of scan operation, the scan operation and display time scales are made equivalent and the actual motion is faithfully reproduced. To realize.
Generally, the time Δt ′ from the scanning operation to the end of writing the tomographic image data in the display memory 34 is C
Depending on the load condition applied to the PU 22, for example, it varies such that it is long during scanning and short when not scanning. Therefore, if the reading operation is started immediately after the writing of the tomographic image data to the display memory 34 is completed, the actual movement cannot be reproduced. In the present embodiment, the time difference from the scanning operation to the start of reading the tomographic image data (start of display) is fixed to at least the time (maximum time) when the CPU 22 is under the maximum load to reproduce the actual movement. To realize. This time control can be realized by a known technique, and as shown in FIG.
The CPU 22 may collectively control the operation of each unit 28, 32, 34, 36 by time, or the reconfiguring unit 32 and the display memory 34 may have the same clock as shown in FIG. Although not shown, the preprocessing unit 28 and the display memory 3
4 is equipped with a timer circuit, the pre-processing unit 28 notifies the controller in the display memory 34 of the time when the projection data for one sheet has arrived, and at the time when a certain time has elapsed from this time, the display memory 34 The tomographic image data may be read from the.

As described above, according to this embodiment,
While scanning continuously, you can observe the movement of the target in almost real time like a cine image. Therefore,
Observe blood flow (flow of contrast agent), perform imaging at optimal timing under this fluoroscopy, move the catheter,
By seeing the change in blood type, it is possible to support biopsy and the like.

As a modified example of increasing the data acquisition speed, in the case of the third-generation CT apparatus, a multi-tube (for example, three-tube) X-ray tube is used, or the X-ray rotation speed is high. This can be achieved by using a 5th generation CT apparatus. The fifth-generation CT apparatus is a high-speed system in which a large number of X-ray tubes are arranged around a subject or a bell-shaped X-ray tube having an annular cathode surrounding the subject is used to scan an electron beam. Achieve rotation.

Further, as a modified example of speeding up the data acquisition speed and the reconstruction time, the reconstruction is not performed from the projection data of 360 °, but is reconstructed from the projection data of less than 360 °, for example, 180 °. The so-called half-scan reconstruction method is used.

Further, as a modified example for preventing an increase in exposure dose due to continuous scanning, an X-ray which can generate an X-ray with a low tube current.
An X-ray generator that can generate a pulse X-ray is used. The X-ray dose largely depends on mAs, which is the product of the tube current mA and the exposure time t (seconds). Therefore, in order to reduce the dose, the tube current may be lowered. But the normal C
Since the T-device is designed to output X-rays with a tube current of several hundreds mA, the tube voltage / tube current control method is changed so that X-rays can be output even with a tube current as low as several tens of mA.

In order to reduce the exposure dose, C
Pulse X instead of continuous X-ray which is the mainstream in T equipment
There is a way to use lines. For example, as shown in FIG.
When pulse X-rays with a duty ratio of 50% (X-rays are emitted for half the total time) are used, the dose can be halved compared to continuous X-rays. Further, a circuit for controlling on / off of the X-ray irradiation at high speed is provided in the control unit in the console 3 to keep the X-ray tube 12 and the detector array 16 rotating.
Alternatively, the X-ray may be turned on or off at a high speed when the operator intends, while continuing the preheated state of the X-ray tube 12. This makes it possible to easily turn on / off the X-rays easily and at high speed, and reduce the exposure dose of the subject.

Further, as shown in FIG. 10, the X-ray tube 12
By providing the filter 40 made of aluminum or copper at the X-ray exit or near the upper slit 42, it is possible to reduce the exposure dose of the subject. As the material of the filter 40, there are Teflon, molybdenum and the like.
Further, by adopting a configuration in which the thicknesses of the filter 40 and the wedge 43 can be changed during photographing, the exposure dose can be adjusted during photographing.

Further, in the above description, the tomographic image data is not stored in the magnetic disk 38, but the CRT monitor 7 is used.
The tomographic image displayed at may be saved using a video recorder if necessary. After the scan is completed, by playing and displaying the tomographic image from the video recorder,
Frame advance and reverse feed are also possible, making diagnosis easy. Further, the reconstructed image data and the incidental information may be recorded in the digital format as they are. When displaying the recorded data, it is transferred to the CRT monitor 7 via the display 34. When recorded as digital data, post-processing such as deletion can be easily performed. (Second Embodiment) FIG. 11 shows the arrangement of an X-ray computed tomography apparatus according to the second embodiment. Here, an X-ray computed tomography apparatus of the third generation (R / R) in which an X-ray tube and an X-ray detector integrally rotate around the subject will be described. However, only the X-ray tube rotates, It may be a fourth generation (R / S) X-ray computed tomography apparatus in which the X-ray detector for one round is fixed.

Inside the pedestal 51, the X-ray tube 53 and the multi-channel X-ray detector 54 are supported by the rotating portion 52 in a state of being opposed to each other with the subject being sandwiched therebetween. The gantry control unit 57 controls the rotation of the rotating unit 52 by supplying drive power to a driving device such as an electric motor that drives the rotation of the rotating unit 52. Each of the X-ray tube 53 and the multi-channel X-ray detector 54 is provided with a slip ring (not shown) so that projection data at an angle of 360 ° or more can be continuously collected.
It is electrically connected to the high voltage generator 55 and the data collection unit 60 on the fixed unit side. From the focus of the X-ray tube 53 supplied with power from the high voltage generator 55, X-rays are radiated in a fan shape. The multi-channel X-ray detector 54 is composed of a plurality of detection elements arranged in an arc shape with the focus of the X-ray tube 53 as the center. An opening (not shown) capable of accommodating the subject is provided in the central portion of the gantry 51. Stand 51
Is installed on the floor through a tilt base so that it can be tilted with respect to the vertical axis. A bed (not shown) is arranged on the front surface of the gantry 51. A top plate on which the subject is placed is provided on the upper surface of the bed. The top plate is supported so as to be slidable in the longitudinal direction from the bed to the gantry 51 and also in the width direction orthogonal to the longitudinal direction in the horizontal plane. The top plate is electrically driven to slide in each direction independently by a driving device such as an electric motor. Couch controller 56
Supplies a control signal to the drive device to control the position of the top in the longitudinal direction (slice position of the subject) and the position in the width direction.

The data collector 60 collects projection data corresponding to the X-ray transmittance based on the output of the multi-channel X-ray detector 54. The projection data from the data collection unit 60 is stored in the scanogram memory 6 during scanogram photography.
1 and is sent to the reconstruction processing unit 62 at the time of scanning. The scanogram is an X-ray projection image of the subject viewed from one direction, and is photographed while sliding the tabletop with the rotating unit 52 stopped. Scanogram memory 61
From the above, the scanogram data is repeatedly read out at a constant cycle during CT fluoroscopy, and is combined with the line cursor data from the system control unit 8 by the adder 63, and then reconstructed by the reconstruction processing unit 62. It is sent to the image display device 64 together with the data. On the image display device 64, a scanogram and a tomographic image are simultaneously displayed on one screen during CT fluoroscopy. An operation unit 59 such as a trackball or a joystick is connected to the system control unit 8. When the operator operates the operation unit 59, the line cursor moves accordingly on the scanogram. The position of the line cursor on the scanogram corresponds to the slice position of the subject who is actually collecting data. When the line cursor is moved on the scanogram, the system control unit 8 controls the bed control unit 56 to move the tabletop so that the slice position corresponds to this position.

Next, the operation of this embodiment will be described. FIG. 12 shows an example of a display screen during CT fluoroscopy. CT
Since the fluoroscopy has been described in the first embodiment, it is omitted here. A scanogram is taken before actually starting CT fluoroscopy. The X-ray exposure and data collection are repeated with the rotating unit 2 fixed at an angle of 0 °, for example. During this time, the top plate is moved continuously or intermittently. The X-ray exposure and the data collection may be repeated only when the angle is 0 ° while rotating the rotating unit 2.
Based on the output of the multi-channel X-ray detector 54, the data acquisition unit 60 repeats acquisition of projection data in synchronization with X-ray exposure. Projection data is scanogram memory 1
1 and stored. As described above, the scanogram is an X-ray projection image, and the projection data collected by the data collecting unit 60 is used as it is as scanogram data.

Next, CT fluoroscopy is actually started. Here, it will be explained as a single slice CT perspective. In CT fluoroscopy, X-ray exposure and data acquisition are repeated while the rotating unit 52 continuously rotates, and projection data is continuously acquired over an angle of 360 ° or more. Every time projection data necessary for reconstructing one piece of tomographic image data is collected, the reconstruction processing unit 62 continuously reconstructs the tomographic image data, and sequentially sends it to the image display device 64. To be Further, the scanogram data is read from the scanogram memory 61, the line cursor data is added through the adder 63, and then sent to the image display device 64. In the image display device 64, as shown in FIG. 12, the tomographic image is combined with the scanogram and displayed on one screen and displayed simultaneously. The line cursor on the scanogram is
The current slice position is shown.

When the operator wants to change the slice position (diagnosis region), he or she operates the operation unit 59 to move the line cursor along the body axis direction on the scanogram. The system control unit 8 controls the bed control unit 56 to move the tabletop along the longitudinal direction according to the movement of the line cursor on the scanogram. As a result, the top plate moves following the movement of the line cursor, the slice position corresponding to the position of the line cursor on the scanogram is set, and this slice position can be scanned. Actually, it is considered that the line cursor is roughly moved to a desired position on the scanogram and then the position of the line cursor is finely adjusted while observing the tomographic image displayed in real time. .

By operating the operation unit 59, the line cursor is moved on the scanogram along the width direction orthogonal to the body axis. The system control unit 8 responds to the movement of the line cursor on the scanogram by the bed control unit 56.
To move the top plate along the width direction. This makes it possible to correct the deviation between the reconstruction area and the subject so that the desired region is included in the tomographic image.

By thus moving the line cursor on the scanogram, the slice position can be changed easily and in a short time. Note that, while the top plate is sliding and while the gantry 51 is tilted as shown in FIG. 14, the gantry control unit 57 controls the rotating unit by the control of the system control unit 58 as shown in FIG. The rotation of 52 is continued, and the high voltage generator 55 temporarily stops the power supply to the X-ray tube 53 to stop the X-ray exposure. Since the rotation unit 52 continues to rotate in this manner, the high voltage generator 55 supplies power to the X-ray tube 53 after the slide of the top plate 65 is completed and the desired slice position is set. Data collection will be restarted immediately by restarting, and CT
You can start seeing through. Because, when the rotation of the rotating portion 52 is stopped while the top plate 65 is sliding,
This is because after the slide of the top plate 65 is completed, the waiting time until the rotating unit 52 reaches the rotation of the constant angular velocity is unnecessary. Further, since the X-ray exposure is stopped while the top plate 65 is sliding, unnecessary exposure can be prevented.

[0050]

[0051]

[0052]

[0053]

[0054]

According to the present invention, the multi-directional projection data in a shorter time than the time required for the scanning operation might have to reconstruct the based-out images data, a predetermined time is also the images data from the scanning operation deer since display later, without it becomes impossible to time interval until the display of the scanning motion or al picture <br/> image to reproduce the actual movement of the object becomes irregular, cine images the images in real time It is possible to continuously display such as.

[0055]

[0056]

[0057]

[0058]

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation in a perspective mode in the first embodiment.

FIG. 2 is an external view of an X-ray CT.

FIG. 3 is a structural diagram of the inside of the gantry of FIG.

FIG. 4 is a block diagram of a control unit.

FIG. 5 is a diagram showing a process progress in a perspective mode.

FIG. 6 is a diagram showing a processing procedure from data collection to display of one tomographic image.

FIG. 7 is a diagram showing the timing of data collection and display in continuous scanning.

FIG. 8 is a modification of FIG.

FIG. 9 is a diagram showing pulsed X-rays used for reducing exposure dose.

FIG. 10 is a view showing a filter used for reducing an exposure dose.

FIG. 11 is a configuration diagram of an X-ray CT according to a second embodiment.

FIG. 12 is a diagram showing an example of a display screen.

FIG. 13 is a time chart showing operations related to the rotating unit and X-ray exposure when the tabletop is slid and the gantry is tilted.

FIG. 14 is a diagram showing a gantry tilt.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stand, 2 ... Bed, 3 ... Operation console, 4 ... Opening part, 5 ... Top plate, 6 ... Keyboard, 7 ... CRT monitor, 10 ... Subject, 12 ... X-ray tube, 14 ... X-ray generator, 16 ... Detector array, 18 ... Data collection system, 20 ... Control unit, 2
2 ... CPU, 24 ... Control bus, 26 ... Data bus, 28 ... Pre-processing unit, 30 ... Disk interface, 32 ... Reconfiguring unit, 34 ... Display memory, 36 ... Memory, 38 ... Magnetic disk device, 42 ... Clock circuit .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naoki Sugihara               1385 No. 1385 Shimoishi, Otawara, Tochigi               Company Toshiba Nasu Factory                (56) Reference JP-A-5-31105 (JP, A)                 JP-A-4-266744 (JP, A)                 JP-A-57-85174 (JP, A)                 JP-A-2-272680 (JP, A)                 JP-A-2-31283 (JP, A)                 Japanese Patent Laid-Open No. 7-323027 (JP, A)                 "CT Scanner" Showa 57-12-20, Ko               Rona Publishing, pages 142-155, 136-137                 New medicine 20 [10] 1993-10-1, 98-99               page

Claims (2)

(57) [Claims] 1. An X-ray tube for irradiating X-rays and an X-ray detector for detecting X-rays transmitted through a subject, wherein the X-ray tube scans so as to draw a spiral trajectory when viewed from the subject. Helical scanning means, data collecting means for continuously collecting projection data from the X-ray data detected by the X-ray detector, and necessary for generating one image in parallel with the collection of the projection data Image data is reconstructed based on the projection data collected by the scan operation in a shorter time than the time required for the scan operation for collecting projection data in a wide range of angles, and this is repeated sequentially to obtain a series of image data. Image reconstructing means for sequentially obtaining the projection data, and display means for displaying the reconstructed image data one after another after a predetermined time from the corresponding scanning operation in parallel with the collection of the projection data. A computer tomography apparatus characterized by the above. 2. The image reconstructing means comprises a plurality of processors connected in parallel for dividing the raw data for each view or each channel to reconstruct the image data. Computer tomography equipment.