JP4233079B2 - CT equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a computed tomography apparatus (abbreviated as a CT apparatus), and more particularly to a CT apparatus capable of continuously executing a scanning operation.
[0002]
[Prior art]
In general, in a CT apparatus, three processes of scanning, image reconstruction, and image display are performed in time series. Multi-directional projection data collected by the rotation of the X-ray tube or the integrated rotation of the X-ray tube and the detector is digitized, subjected to preprocessing such as calibration, and then 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 reconstruction unit is stored on the magnetic disk, and transferred to the CRT monitor via the display memory for display.
By the way, in recent years, continuous scanning has become possible by the introduction of slip rings. By this continuous scanning, a plurality of multidirectional projection data relating to the same or a plurality of slices can be collected in time series. These multi-directional projection data are read out to the reconstruction unit at an arbitrary timing via the magnetic disk as described above and used for reconstruction. Here, there are the following two conventional techniques for increasing the reconfiguration rate.
[0003]
(First Technology) JP-A-4-266744
In the present technology, partial images are reconstructed one after another for each projection data collected while the X-ray tube and the detector are rotated by a minute angle α degree (for example, α degree = 10 degrees). Then, by adding the 36 partial images, one complete tomographic image for 360 degrees is created. Once one tomographic image is created, the latest partial image is added to the tomographic image and the oldest partial image is subtracted from the tomographic image. As a result, new tomographic images are created one after another every 10 degrees of rotation, and the tomographic images can be continuously acquired at a high reconstruction rate.
(Second Technology) JP-A-57-134142
According to the present technology, the latest projection data (for example, projection data for 360 to 370 degrees) after the projection data collected for generating the tomographic image is obtained for one complete tomographic image for 360 degrees. And the difference data between the latest projection data and projection data whose projection angle differs by about 180 degrees (for example, projection data for 180 degrees to 190 degrees) is further subjected to back projection processing (hereinafter referred to as back projection). )I do. By repeating this, new tomographic images can be created one after the other every time it is rotated by 10 degrees as in the first technique.
[0004]
[Problems to be solved by the invention]
However, in any of the conventional techniques, the update angle is determined in advance, and an arbitrary update angle cannot be set depending on the operator's preference, and the same update angle is used depending on the difference in the inspection method and the like. The image was updated.
Here, the update angle refers to an angle at which the X-ray irradiation direction changes while acquiring projection data (or projection data group) newly required to update an image. In the first prior art, this corresponds to the minute angle α degrees.
In addition, the update angle is not necessarily better for the operator as it is smaller (updated faster as an image), but varies depending on the operator's preference, examination site, and examination method.
For example, when an operator observes a relatively fast moving part, for example, the heartbeat, it is possible to update the image quickly by reducing the update angle. When observing a slow-moving part, for example, an organ of the digestive system, an image may be updated slowly by increasing the update angle.
[0005]
In addition, as one of the inspection methods, there is a contrast agent inspection. As one of the techniques in the contrast agent inspection, pre-scanning is performed until the contrast agent reaches a predetermined region of interest (hereinafter referred to as ROI). The scan is called, and the pre-scan is used to detect the timing of the ROI scan (hereinafter referred to as the main scan).
More specifically, this pre-scan is to measure the CT value of a region other than a predetermined ROI. When this CT value reaches a predetermined value, it is considered that the contrast agent has reached the ROI and the main scan is automatically performed. Scan.
In such a contrast agent pre-scan, if the update angle is too small, the degree of increase in CT value for each image update becomes small, and there is a possibility that the main scan cannot be performed at the optimum timing.
In addition to this, there are cases where the update speed of the real-time image is changed for various reasons.
The present invention has been made in view of the above-described circumstances, and an object thereof is to improve the convenience of real-time CT.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is directed to an X-ray generation means for generating X-rays and a detector having a plurality of detection elements facing each other with the subject interposed therebetween. In a CT apparatus that continuously rotates and reconstructs an image based on the projection data collected by the detector, the image is reconstructed based on the projection data collected by the detection means, and is provided at predetermined intervals. Image reconstructing means configured to update the image by performing back projection of the projection data, display means for displaying the image reconstructed by the reconstructed image generating means, and the X-ray generating means Reconstructing interval setting means capable of changing the interval so that the time interval at which the reconstructed image is updated is changed while X-ray irradiation is performed. The image reconstruction means is based on the projection data obtained before the change and the projection data obtained after the change immediately after the interval is changed by the reconstruction interval setting means. Configured to update the image CT apparatus characterized by the above. It is characterized by comprising.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of a CT apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a CT apparatus according to the first embodiment.
The X-ray CT apparatus according to the present embodiment includes a gantry 1, a bed 2, and a console 3. An opening 4 into which a subject (generally a patient) is inserted is provided at 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. A couchtop 5 on which a subject is placed is provided on the upper surface of the couch 2, and the couchtop 5 is configured to be slidable electrically from the upper surface of the couch 2 toward the gantry 1. Although not shown, a caster or the like is attached to the lower part of the gantry 1 so that the gantry 1 can slide manually or automatically toward the bed 2. In this case, CT fluoroscopy may be used in combination with surgery. In this case, it is possible to change the slice position by moving the gantry 1 rather than moving the top 5 from the viewpoint of the safety of the subject. It is because it is preferable. Of course, the slice position can be changed by sliding the top plate 5. Note that the slice position is generally changed only by sliding the top plate 5.
[0008]
A keyboard (which may include a mouse or the like) 6 and a CRT monitor 7 are disposed on the console 3, and a control unit is housed in the console 3. This control unit is connected to both the gantry 1 and the bed 2.
Further, as shown in FIG. 2 which is a block diagram, in the gantry 1, an X-ray tube 12 for exposing a subject 10 placed on the top 5 to a fan-shaped X-ray beam, and an X-ray The detector 16 in which a plurality of detection elements are arranged in an arc shape around the focal point of the tube 12 is rotated so that the periphery of the subject 10 can be continuously rotated as a unit while facing the subject 10. Supported by the department.
Further, the X-ray tube 12 and the detector 16 are electrically connected to the fixed portion via a slip ring.
In addition, an X-ray generator 14 for supplying tube current and tube voltage to the X-ray tube 12 in a continuous or pulsed manner for generating X-rays is installed in the fixed part of the gantry 1 via a slip ring. It is connected to the X-ray tube 12. The X-ray generator 14 can also be mounted on the rotating part of the gantry 1. In addition, a data acquisition system (DAS) 18 is installed in the rotating part of the gantry 1 and connected to the detector 16. This DAS 18 integrates an output signal from each detector of the detector 16 with respect to time, a multiplexer for taking in the output of this integrator in a high-speed and serial manner in units of channels, and an output signal of this multiplexer. It is composed of an analog-digital converter or the like for converting to digital, and collects and outputs projection data reflected in the X-ray transmittance for each X-ray path.
[0009]
The X-ray generator 14 and the DAS 18 are connected to the control unit 20.
Next, the control unit 20 will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a block diagram of the control unit 20 in the console 3, and FIG. 4 is a block diagram of the reconstruction unit 32.
The control unit 20 is provided with a CPU 22 as a host controller, and a control bus 24 and a data bus 26 are connected to the CPU 22. The CPU 22 has a built-in clock circuit 42, manages the operation and time of each unit using the clock from the clock circuit 42, and supplies this clock to each unit in the control unit 20 as a common clock.
An updated view number storage unit 41, a memory 36, a preprocessing unit 28, a disk interface (disk I / F) 30, a reconstruction unit 32, and a display memory 34 are connected to the control bus 24. The updated view number storage unit 41 stores the number of projection data that is the basis of the partial image generated in the reconstruction unit 32. Details will be described later.
[0010]
In addition, a keyboard 6 and an X-ray generator 14 are connected to the control bus 24.
On the other hand, a pre-processing unit 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. A magnetic disk device 38 as a mass storage device is connected to the disk I / F 30. A DAS 18 is connected to the preprocessing unit 28.
Further, as shown in FIG. 4, the reconstruction unit 32 includes a partial image generation unit 51 to which the updated view number storage unit 41 and the memory 36 are connected, an output of the partial image generation unit 51 and an updated view number storage unit 41. A partial image memory 52 connected to the output unit, a weighting unit 53 connected to the output and updated view number storage unit 41 of the partial image memory 52, and an addition unit 54 connected to the weighting unit 53. Are connected to the display memory 34.
Here, the number of views will be described. The number of views is the number of times projection data is collected. For example, when projection data is collected 900 times while the X-ray tube 12 makes one revolution, one revolution is 900 views. Become. The updated view number is the number of times projection data is newly collected to update the image. For example, when the reconstructed image is updated every 90 views, the updated view number is 90 views. .
[0011]
Also, the relationship between the update angle and the number of updated views is
Update angle: 360 degrees = updated view number: The number of views (the number of one-rotation view) while the X-ray irradiation direction rotates 360 degrees. Furthermore, the relationship with the time interval (update time) at which the reconstructed image is updated is as follows: update time = time required for the X-ray irradiation direction to rotate 360 degrees × updated view number / 1 rotation view number Can be represented. The time required for the X-ray irradiation direction to rotate 360 degrees is the time required for the detector to make one rotation in the third generation CT apparatus, for example, 0.5 seconds.
The partial image generation unit 51 performs back projection based on the projection data group with the updated number of views, and generates a partial image.
The partial image memory 52 stores this partial image, and has a capacity for storing at least 12 partial images.
The weighting unit 53 is provided with two types of weighting filters, and each weighting filter has a plurality of coefficients. The weighting filter will be described later.
[0012]
The adding unit 54 adds the partial images weighted by the weighting filter 53 and generates one CT image.
Next, the overall operation of the X-ray CT apparatus in the present embodiment will be described with reference to FIG. 1 and FIG.
The operator creates a CT image from the keyboard 6 in a state in which the X-ray CT apparatus is stopped (a state in which no X-ray is irradiated from the X-ray tube 12). In addition, set the number of updated views.
Hereinafter, a case where the number of updated views is set to 90 views will be described.
After setting the scanning conditions and the number of updated views by the operator, X-rays are emitted from the X-ray tube 12 via the X-ray generator 14 by a predetermined operation, and projection data is sent to the DAS 18 via the detector 16. Sent.
Projection data collected by the DAS 18 is input to the control unit 20. In the control unit 20, as shown in FIG. 3, the projection data from the DAS 18 is subjected to preprocessing such as calibration by the preprocessing unit 28, and then is transmitted as raw data via the data bus 26 to the disk I / F 30. Then, a part of raw data is written in a memory 36 such as a readable / writable DRAM.
[0013]
The updated view number set by the operator is stored in the updated view number storage unit 41.
The raw data stored in the memory 36 is sequentially sent to the reconstruction unit 32.
The reconstruction unit 32 generates a reconstructed image based on the projection data group. This reconstructed image is once written in a display memory 34 such as a readable / writable DRAM, and then read out and displayed on the CRT monitor 7 from here. The reconstructed image is read from the display memory 34 and stored in the magnetic disk device 38 via the disk I / F 30.
The operation of the reconstruction unit 32 is divided into three operations: (1) normal operation for image reconstruction, (2) operation when an image is updated, and (3) operation when changing the number of updated views. explain.
(1) Normal operation of image reconstruction
The normal operation of image reconstruction will be described with reference to FIGS. FIG. 5 is a conceptual diagram showing a data flow in the reconstruction unit 32.
[0014]
The partial image generation unit 51 uses the projection data group 61 with the updated view number (90 views) stored in the updated view number storage unit 41 as a unit among the projection data read from the memory 36 to display the partial data. Back projection is performed after the convolution processing for all the pixels to be performed, and one partial image 62 is generated. The partial image generation unit 51 sequentially generates partial images 62 every time 90 projections of projection data are read from the memory 36, and the generated partial images 62 are sent to the partial image memory 52 shown in FIG. Stored sequentially.
The weighting unit 53 has two types of weighting filters having different numbers of weighting coefficients, and each weighting coefficient is 10 (0.2, 0.6, 1, 1, 1, 1, 1, 1, 0.6). , 0.2) and 12 (0.2, 0.6, 1, 1, 1, 1, 1, 1, 1, 1, 0.6, 0.2).
[0015]
In this embodiment, since the number of updated views is 90 views and the number of rotated views is 900 views, it is necessary to multiply each of the 10 partial images by a coefficient, and the weighting filter 63 having 10 coefficients is selected.
Of the 10 coefficients, the one with the smallest coefficient value (coefficient value 0.2) is multiplied by the latest partial image and the oldest partial image, and the next one with the next smallest coefficient value (coefficient value 0.6) is the latest two. The partial image of the eye and the second partial image from the oldest are multiplied by a larger coefficient value (coefficient value 1) to the other partial images. Each pixel value of one partial image is multiplied by the same coefficient.
In the addition unit 54, the partial images 64 thus weighted are added for each pixel, with one partial image for one round (10 partial images as one unit). A composition image 65 is created.
The created reconstructed image 65 is sent to the display memory 34 and displayed on the CRT monitor 7. The above series of operations is performed every 90 views, and the reconstructed image 65 updated every 90 views is displayed.
[0016]
(2) Operation when an image is updated
Hereinafter, an operation when the generated reconstructed image is updated will be described with reference to FIGS. 4 and 6. FIG. 6 is a diagram showing the relationship between projection data, partial images, and weighting filters. 5 and 6 are denoted by the same reference numerals and description thereof is omitted.
The dotted line frame 66 in FIG. 6 surrounds the partial image 62 before update and the weighting filter 63 multiplied by this, and the dotted line frame 66 'indicates the partial image 62 after update and the weighting filter multiplied by this. 63 is enclosed.
The projection data group 61 ′ shown in FIG. 6 is a newly collected projection data group, and a partial image 62 ′ is generated from the projection data group 61 ′.
When the partial image 62 ′ is generated, the weighting filter 63 shifts so that the latest partial image 62 ′ is multiplied by the coefficient of the weighting filter, as shown in FIG. , Each coefficient of the weighting filter 63 is multiplied.
[0017]
That is, when the latest partial image 62 ′ is generated, the oldest partial image before acquisition of the partial image 62 ′ is not used, and 10 parts are newly generated from the latest partial image 62 ′. Only the image is weighted, and a reconstructed image is generated.
Explaining this from the partial image side, each partial image 62 means that each coefficient of the weighting filter 63 is shifted and multiplied one after another.
That is, each partial image is weighted in the order of 0.2, 0.6, 1, 1, 1, 1, 1, 1, 0.6, 0.2 in accordance with the update of the reconstructed image.
(3) Operation when changing the number of updated views
Hereinafter, the operation when the number of updated views is changed by the operator during the operation of the X-ray CT apparatus will be described with reference to FIGS. 3 and 4.
When the number of updated views is changed by the operator, the changed number of updated views is stored in the updated view number storage unit 41 and stored in the memory 36, the partial image memory 52 in the reconstruction unit 32, and the display memory 34. The information being reset is reset. As a result, the CT image displayed on the CRT monitor is also not displayed.
[0018]
In addition, the partial image generation unit 51 in the reconstruction unit 32 created one partial image from the projection data group 90 View before the update view number change, but when the update view number is changed to 75 views, One partial image is generated from the projection data 75View.
A weighting filter having 12 coefficients is selected. This is because 12 partial images (900View / 75View) are required to generate one reconstructed image.
In addition, in the addition unit 54, in the state where the number of updated views is 90 views, one reconstructed image is created with 10 partial images. However, when the number of updated views is changed to 75 views, the reconstructed image is displayed. Is generated by generating one reconstructed image from 12 partial images.
After a predetermined setting is made when changing the number of updated views, a reconstructed image is generated and displayed on the CRT monitor 7 as in the case where the number of updated views is 90 views.
[0019]
In the CT apparatus according to the present embodiment, since the operator can arbitrarily determine the number of views of projection data for creating a partial image, it is possible to appropriately adjust the real-time property according to imaging. is there.
In this embodiment, the number of updated views can be changed even during operation (while X-ray irradiation is in progress). . Movement The ability to set the number of updated views during the operation means that, from the standpoint of the operator, once the appropriate number of updated views are set and the displayed image is observed, the updated view is further compared to this image. This means that it is possible to determine whether to increase or decrease the number, and this is effective particularly when the same part is continuously imaged (when dynamic scanning is performed).
[0020]
In the above-described embodiment, no particular reference is made to the scanning method. For example, in order to track changes in tomographic images due to inflow and outflow of a contrast agent, the scan system continuously rotates at the same slice position of the subject. A so-called dynamic scan may be performed, or a so-called helical scan that changes the slice position in synchronization with the rotation may be performed.
In addition, regarding the X-ray tube and the detector, the X-ray tube and the detector are both supported by the rotating part, and the so-called third generation (R / R method) is described, but is not limited to this type. A so-called fourth generation (R / S method) in which detectors are arranged around the subject over 360 ° and only the X-ray tube rotates, or an anode that generates X-rays around the subject over 360 °. The so-called fifth generation (S / S method) may be used.
In addition, regarding the method for setting the number of updated views, in the above embodiment, the operator inputs or selects the number of views. However, from the viewpoint of the operator, the time (for example, seconds) The concept of () is more recognizable, so it is desirable that the view concept is converted into seconds and displayed on the CRT monitor 7 to set the number of updated views.
[0021]
For example, in the case of the third generation CT apparatus, for example, when the detector 16 rotates once around the subject 10 in 0.5 seconds, the number of views that can be acquired in one rotation, this embodiment Then, since it is 900View, it can be converted as 900View in 0.5 seconds.
For example, when a partial image is generated with 90 View as one unit, 0.05 sec or 50 μsec may be displayed on the CRT monitor 7.
Moreover, it is good also as an update angle display instead of a time display. In this case, since 360 degrees is 900 views, 90 views are displayed as 36 degrees.
Moreover, although the number of filter coefficients was demonstrated as the same number as a partial image, it does not necessarily need to be the same number. For example, although there are 12 filter coefficients, only 10 coefficients may be used, and some filter coefficients may be used.
Further, although the case where a partial image corresponding to 360 degrees of projection data is used when generating a reconstructed image has been described, one reconstructed image may be generated using projection data of 360 degrees + α. For example, when the detector is 900 views in one rotation and the number of updated views is 90 views, a reconstructed image may be generated using 1080 view projection data (12 partial images).
[0022]
In addition, for simplicity of explanation, the number of weighting filters is two, but having more weighting filters means that a larger number of updated views can be selected, and the operator can change the real-time property more finely. Can do.
Further, the coefficient value of the weighting filter is not particularly limited. However, the coefficient of the weighting filter is applied with a small weight on the latest and oldest partial images (multiplied by a small coefficient), and a larger weight is applied as the distance from the latest and oldest partial images is increased in time (larger). Assuming that the coefficients are multiplied), artifacts on the reconstructed image can be reduced.
Next, a modification of the first embodiment will be described with reference to FIGS. FIG. 7 is a diagram showing the relationship between projection data, partial images, and weighting filters when changing the number of updated views. In addition, the same thing as FIG. 6 attaches | subjects the same number, and abbreviate | omits description.
[0023]
Briefly described, this modified example updates the reconstructed image more smoothly without resetting each memory when the number of updated views is changed as in the first embodiment.
In the present embodiment, as shown in FIG. 7, in addition to the partial image 62 ′ ″ generated from the projection data group 61 ′ ″ collected after the updated view number is changed from 90 View to 75 View, the update One reconstructed image is created from a total of 12 partial images using the partial images 62 and 62 '' created when the number of views is 90 views.
Note that the partial image 62 is a partial image used for creating a reconstructed image one time before the updated view number is changed, and the partial image 62 ″ is used one time before the updated view number is changed. The partial image used two times before the update view number is changed is shown.
Here, again, the operation when the updated view number is 90 views will be described. In the partial image generation unit 51, one partial image is generated for each 90 views and is sequentially stored in the partial image memory 52. Also, the latest 10 partial images are read out from the partial image memory 52 among the stored partial images, and each partial image is read by the weighting filter having 10 coefficients in the weighting unit 53. Are weighted, and the addition unit 54 performs an addition process.
[0024]
In this state, when the number of updated views is changed to 75 views, the partial image generation unit 51 generates one partial image for every 75 views from the next update timing.
Further, the partial image memory 52 stores at least 12 partial images including the partial image generated by 75View.
In other words, after changing the number of updated views, the latest 12 partial images stored in the partial image memory 52 are one partial image generated by 75 views, and the other 11 partial images generated by 90 views. Become.
In the weighting unit 53, the weighting filter is changed to include 12 coefficients, and 12 partial images stored in the partial image memory 52 are read and weighted.
In FIG. 7, it is indicated by a dotted frame 66 ″. In accordance with this, the weighting filter is also changed to a weighting filter 63 ″ having 12 coefficients.
In the CT apparatus according to this modification, the real-time property can be appropriately adjusted according to the imaging, as in the first embodiment.
[0025]
In the first embodiment, when the number of updated views is changed, a predetermined time lag occurs until the next reconstructed image is displayed by resetting the partial image memory. In the CT device in the example, when the operator changes the number of updated views, a new image is created using the partial image created before the change, so the displayed reconstructed image transitions smoothly without interruption. Is done.
Next, a second embodiment of the present invention will be described.
Briefly describing this embodiment, the number of updated views is changed between the pre-scan and the main scan in the contrast medium inspection. Here, the main scan refers to a scan of an area in which the operator is most interested in taking an image, and the pre-scan refers to a contrast agent from the area where the main scan is performed in order to optimize the timing of the main scan. This is a scan of the area upstream of the flow. Note that the pre-scan is performed prior to the main scan.
[0026]
The CT apparatus according to the present embodiment includes a contrast medium inspection control circuit (in the control unit 20 shown in FIG. 3 according to the first embodiment) that has a function of performing a main scan according to the timing obtained by the prescan. (Not shown) is provided.
Before injecting the contrast medium, the operator performs settings for performing a contrast medium inspection with the X-ray CT apparatus via the keyboard 6.
This setting includes, for example, the position of the subject to be pre-scanned, the pre-scan condition (updated view number), the position of the subject to be subjected to the main scan, the condition of the main scan (number of updated views), and the pre-scan is completed. The CT value is an index for starting the main scan. Here, as an example, a description will be given assuming that the pre-scan position is the neck, the main scan position is the head, the pre-scan update view number is 90 views, and the main scan update view number is 30 views. It should be noted that the larger the number of updated views, the greater the degree of increase in the CT value. Therefore, it is desirable that the number of updated views be larger in the prescan than in the main scan.
[0027]
The setting information input by the operator is sent to the CPU 22. In particular, the information on the updated view number is sent to the updated view number storage unit 41 via the CPU 22.
The operator sets an ROI on the neck by a pre-scan ROI setting unit (not shown). Pre-scan is started by injecting contrast medium into the arm vein. That is, the scan is performed so as to go around the neck of the subject, and projection data collection is repeated. As a result, the tomographic image of the cervix is reconstructed in real time (reconstruction has already been shown in the first embodiment), while the CT values of all the pixels in the ROI (carotid artery) are calculated as CT values in the ROI. Part (not shown). The intra-ROI CT value calculation unit adds these CT values and supplies the addition result to a graph generation unit (not shown). The graph generation unit generates a graph of concentration change by sequentially plotting the added value from the CT value calculation unit in the ROI with the vertical axis as the level (CT value) and the horizontal axis as the time.
[0028]
The graph generated by the graph generation unit is sent to a determination unit (not shown). The determination unit determines the pre-scan end timing and the main scan start timing, sends a trigger signal to the clock circuit 42, and sends a change signal for changing the updated view number to the updated view number storage unit 41.
Thus, the pre-scan is completed, the bed is moved by the distance between the main scan start position of the head and the pre-scan position, and the main scan start position of the head is made to coincide with the imaging region. Then, after the pre-scan is finished, the main scan is started at the timing when the delay time set as the time for the blood flow to reach the head from the neck portion has elapsed. Note that the number of updated views is changed from 90 views to 30 views before the main scan is started.
As a result, the tomographic image of the head is sequentially reconstructed and displayed in real time.
In the present embodiment, by using different updated view numbers for the pre-scan and the main scan, particularly in the contrast medium inspection, it is possible to detect the optimal timing for performing the main scan in the pre-scan, and more appropriate contrast medium inspection. It can be performed.
[0029]
In this embodiment, the update view number is automatically set based on the CT value obtained by the pre-scan. However, the present invention is not limited to this, and the scan time and the tube current of the X-ray tube are described. The number of updated views may be automatically set based on such parameters.
In each embodiment and modification, the number of updated views can be changed and the rotation speed and the timing of reading projection data from the detector are constant. However, the reconstructed image displayed on the CRT monitor If the update time can be changed, the update view number is not necessarily changed. For example, it can also be achieved by changing the number of views per rotation while changing the number of views updated (changing the signal readout timing from the detector).
Note that the above-described embodiments and modifications can be combined. For example, the configuration may be such that the setting of the updated view number is performed both manually and automatically.
[0030]
In the above embodiment, a two-dimensional image has been particularly described as a reconstructed image. However, the present invention is not limited to this and includes a three-dimensional real-time image.
[0031]
【The invention's effect】
As explained in detail above, according to the present invention, While X-ray irradiation is performed, Image update in reconstruction interval The convenience of real-time CT can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of a CT apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram in the gantry in the first embodiment according to the present invention.
FIG. 3 is a block diagram of a control unit in the console according to the first embodiment of the present invention.
FIG. 4 is a block diagram of a reconstruction unit in the first embodiment according to the present invention.
FIG. 5 is a conceptual diagram showing a data flow in a reconfiguration unit in the first exemplary embodiment of the present invention.
FIG. 6 is a conceptual diagram showing a data flow when reconfiguration is performed in the first embodiment according to the present invention.
FIG. 7 is a conceptual diagram showing a data flow when reconfiguration is performed when the number of updated views is changed in the first embodiment of the present invention.
[Explanation of symbols]
1 frame
2 Sleeper 2
3 console
4 openings
5 Top plate
6 Keyboard
7 CRT monitor
10 Subject
12 X-ray tube
14 X-ray generator
16 Detector
18 DAS
20 Control unit
22 CPU
24 Control bus
26 data buses
28 Pre-processing section
30 disk I / F
32 Reconstruction part
34 Display memory
36 memory
38 Magnetic disk drive
41 Updated view number setting circuit
42 Clock circuit
51 Partial image generator
52 Partial image memory
53 Weighting section
54 Adder
61 Projection data group
62 Partial images
63 Weighting filter
64 partial images
65 Reconstructed image

Claims (8)

Based on the projection data collected by the detector, the X-ray generation means for generating X-rays and the detector having a plurality of detection elements are opposed to each other with the subject interposed therebetween and continuously rotated around the subject. In a CT apparatus for reconstructing an image,
An image reconstruction unit configured to reconstruct an image based on the projection data collected by the detection unit, and configured to perform back projection of the projection data at predetermined intervals to update the image; ,
Display means for displaying the image reconstructed by the reconstructed image generating means;
Reconstructing interval setting means capable of changing the interval so that the time interval at which the reconstructed image is updated is changed while X-ray irradiation is performed from the X-ray generating unit ;
The image reconstruction means includes
Immediately after the interval is changed by the reconstruction interval setting means, the image is updated based on the projection data acquired before the change and the projection data acquired after the change. CT apparatus characterized by the above. The reconstruction means includes
Partial image generation means for generating a partial image at each predetermined interval based on the data detected by the detection means;
Reconstructed image generating means for generating a reconstructed image based on a plurality of partial images generated by the partial image generating means;
The CT apparatus according to claim 1, further comprising:   The CT apparatus according to claim 1, wherein the reconstruction interval setting unit includes a manual setting unit in which an operator manually sets the predetermined interval.   The CT apparatus according to claim 1, wherein the reconstruction interval setting means includes automatic setting means for automatically setting the predetermined interval.   The CT apparatus according to claim 1, wherein the detection unit draws the same trajectory a plurality of times with respect to the subject, or draws a spiral trajectory with respect to the subject.   The CT apparatus according to claim 1, wherein the predetermined interval for performing the reconstruction is determined based on time.   The CT apparatus according to claim 1, wherein the predetermined interval for performing the reconstruction is determined based on a projection angle.   The CT apparatus according to claim 1, wherein the predetermined interval for performing the reconstruction is determined based on the number of times projection data is collected.

Images