JPH0628659B2 - X-ray CT system - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an X-ray CT apparatus.

[Technical background of the invention and its problems] When observing a temporal change of a certain part of an object by an X-ray CT apparatus, a conventional apparatus without a slip ring mechanism requires a scan time as short as possible. A scan is performed on the subject, and then a pause is provided between the scans, and then the scan on the subject is performed again. In this conventional device, it is normal to perform deceleration-stop-acceleration operation in the reverse rotation direction of the gantry after performing one scan, and then perform the next scan. This is because there is no slip ring mechanism and the cable separating mechanism is used. It is based on having.

In such a conventional apparatus, there is a problem that the scan pause time becomes long and it is often impossible to obtain image data sufficient to reconstruct a tomographic image of the subject at an arbitrary time point.

Further, in the above-mentioned conventional apparatus, the pause time between scans is variable, and the third time is set at the time when the temporal change of the phenomenon occurring in the specific part of the subject to be observed usually becomes loose.
As shown in the figure, a pause between scans is set to be long to avoid unnecessary scans according to the temporal change.

Further, as shown in FIG. 4, the projection data from the 360 ° direction on the subject is obtained by one scan, but the image of a certain specific portion can be reconstructed from the projection data less than 360 ° (180 ° plus X Since the beam angle of the source)
As shown in FIG. 4, it is possible to reconstruct three images at different times in one scan.

In this way, there is a method of successively updating and displaying a series of images obtained at the timings shown in FIGS. 3 and 4 on a display means such as a TV monitor in the order in which these images were obtained. This is called a cine display.

By the way, in the conventional cine display, the image update time interval is set to be constant, and it has not been considered at all that the time interval at which a large number of images to be updated and displayed is obtained is not constant and is indefinite.

As a result, when observing the display image by observing the display means, a significant sense of time distortion occurs between the image actually obtained by scanning and the display image.

That is, for example, considering the image reconstruction timing and its display timing as shown in FIG. 4, the time change from the first to the third image of the reconstructed image based on the first scan is the reconstruction time. Although the timing and the display timing can be made to substantially coincide with each other, the reconstruction timing and the display timing are different between the third reconstructed image of the first scan and the first reconstructed image of the second scan. It is markedly different and will be displayed at a timing much faster than the actual reconstruction timing.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to obtain a tomographic image of a subject at a desired point in time and to correlate the image reconstruction timing with the display timing. It is an object of the present invention to provide an X-ray CT apparatus that does not cause the distortion of the sense of time.

[Summary of the Invention] An outline for achieving the above object is to provide a series of X-rays obtained by irradiating an X-ray from an X-ray source that can be continuously rotated around the object and transmitting the same through the object. In an X-ray CT apparatus for obtaining a tomographic image of a subject based on X-ray transmission information, a storage unit that continuously stores the X-ray transmission information and a predetermined X-ray transmission information stored in the storage unit are mutually predetermined. Have spacing,
In addition, the image reconstruction unit that sequentially cuts out a plurality of pieces of information sufficient for image reconstruction for one image each and reconstructs each of them to obtain a series of reconstructed images, and the obtained series of reconstructed images in order. And a display unit for displaying, which is capable of continuously rotating around the subject.
In an X-ray CT apparatus that obtains a tomographic image of a subject based on a series of X-ray transmission information obtained by transmitting X-rays from a radiation source to the subject and transmitting the same through the subject, A storage unit that stores continuously, and a plurality of pieces of information that have a predetermined interval from each other and that are sufficient for image reconstruction of one sheet are sequentially cut out from the X-ray transmission information stored in the storage unit. An image reconstructing unit for reconstructing processing, an image memory for storing reconstructed image data for each reconstructed image at a predetermined address, a setting unit for arbitrarily setting a time interval, and an image memory on the image memory. Display control means for updating the display of the reconstructed image at the time interval set by the setting section based on the address of.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG.

The apparatus of the embodiment shown in FIG. 1 has an X-ray detector with an X2 and an X-ray detector 3 facing each other around a subject M in a gantry having a slip ring 1 and configured to be rotatable. A data collection unit 4 for collecting X-ray transmission information ((transmission X-ray dose, transmission X-ray data) detected by 3 is provided, and X-rays are transmitted to the front X-ray tube 2 from the high-voltage generator 5 via the slip ring 1. It is designed to supply high pressure for exposure.

In addition, this apparatus performs a tomographic image reconstruction process of the subject M based on the storage unit 6 that captures the output of the data collection unit 4 via the slip ring 1 and the X-ray transmission information stored in the storage unit 6. An image reconstructing unit 7 to be executed and a magnetic disk 8 for storing the tomographic image data output from the image reconstructing unit 7 together with original time information indicating which time data was used.
A large-capacity image memory 9 for storing the tomographic image data stored on the magnetic disk 8 and the tomographic image data fetched from the image memory 9 at a predetermined timing.
Display control means 1 for sending to display means 10 such as a monitor
1, a input unit 12 of a keyboard unit for sending predetermined input information to the display control unit 11, and a CPU (Central Proccssing Unit) 13 for controlling each unit of the apparatus described above.

The display control means 11 stores the original time information stored in the magnetic disk 8 and the address of each reconstructed image data in the image memory 9 via the CPU 13.
The time storage unit 14, the update time generation unit 15 that generates the update time Ti of the display image on the display unit 10 based on the input information from the input unit 12, and the address / time storage unit 14 and the update time generation unit 15. An address generator 16 for controlling the image memory 9 so as to sequentially send the reconstructed image data corresponding to each tomographic image corresponding to the update time Ti based on the output, and each reconstructed image sent from the image memory 9. It has a display controller 17 which converts data into an image signal and sends it to the display means 10.

Next, the operation of the above-described apparatus will be described by taking as an example the case of obtaining a tomographic image of the subject M at a desired time.

The X-ray source 2, the X-ray detector 3, and the data acquisition unit 4 are connected to the subject M.
While continuously rotating around, the high pressure is applied from the high pressure generator 5 to the X-ray source 2 through the slip ring 1, and the X-rays are continuously emitted toward the subject M. The rotation cycle at this time is the second
Let T as shown.

The X-ray transmission information obtained by passing through the subject M by the continuous exposure described above is detected by the X-ray detector 3, further collected by the data collecting unit 4, and then written in the storage unit 6 via the slip ring 1. Be done.

After the scan for the subject M is completed, the image reconstruction unit 7 displays C
One revolution (2 revolutions of the X-ray source 2 or the like is controlled from an arbitrary time point of the continuous X-ray transmission information stored in the storage unit 6 under the control of the PU.
The X-ray transmission information a, b, c, ... Corresponding to π) is cut out and image reconstruction processing is performed on each of these. In this case, the X-ray transmission information for reconstructing one tomographic image is not limited to the rotation angle 2π of the X-ray source 2 and the like, and π +
It may be (fan angle of X-ray source 2).

The X-ray transmission information may be the output of the data acquisition unit 4 as it is, and in this case, the image reconstruction unit 7 may be provided with various preprocessing functions in advance. Further, by providing a sufficiently high-speed pre-processing function, the data sent from the data collecting unit 4 is pre-processed during the scan of the subject M and the processing result is used as projection data on the magnetic disk 8 It may be stored in.

The reconstructed image data reconstructed for each sheet in the image reconstruction unit 7 in this manner is written to the magnetic disk 8. The CPU 13 reads the reconstructed image data for one rotation from the magnetic disk 8 with an arbitrary time point as a reference, and writes it in the image memory 9. Then, this reconstructed image data is sent to the display controller 17, where it is converted into an image signal and sent to the display means 10. Display means 10
Displays a tomographic image for each sheet based on this image signal for diagnostic use.

Through a series of operations of this apparatus described above, a tomographic image of the subject M at a desired time can be obtained.

Next, the operation in the case where the timing of image reconstruction and the display timing on the display means 10 are made proportional by this device will be described. The procedure until the X-ray transmission information is captured in the image reconstructing unit 7 is the same as the above-mentioned case, and therefore its detailed description is omitted.

The series of reconstructed image data processed by the image reconstructing unit 7 is stored in the magnetic disk 8 together with the original time information indicating at which time the collected data was used. The information is sequentially stored in a predetermined address of the image memory 9 together with the information.

The number of each reconstructed image corresponding to each reconstructed image data is i (i is a positive integer), and the reconstructed image data is obtained from the time when the reconstructed image data immediately before a certain reconstructed image data is obtained. The following description will be made assuming that the elapsed time up to the time point is ti.

The address / time storage unit 14 of the display control means 11 is a CPU.
The elapsed time ti of the reconstructed image data corresponding to the image number i on the image memory 9 and the address on the image memory 9 are stored in the address / time storage unit 14.

At this time, it is assumed that the reconstructed image with the image number i is displayed on the display unit 10.

The operator operates the input means 12 to send the information K (K is a constant that can be changed appropriately) for updating the display image to the update time generating unit 15. The update time generation unit 15 uses the input means 12
An update time Ti (= Kti) for updating the display on the display means 10 is calculated based on the information K from and is sent to the address generator 16.

The address generator 16 stores the elapsed time ti of the i-th image and its address in the address / time storage unit 14.
And the update time Ti from the update time generation unit 15 is taken in, the address of the (i + 1) th reconstructed image data is calculated based on these, and this address is sent to the image memory 9 after the update time Ti has elapsed. As a result, the (i + 1) th reconstructed image data is sent to the display controller 17, and as a result, the display image on the display means 10 is (i
It is updated to the +1) th reconstructed image.

In this way, the reconstructed images on the display means 10 can be updated one after another at arbitrary intervals by the information K from the input means 12, and if the value of K is set to 1, reconstructed image data can be obtained. The timing and the update timing of the display image can have a 1: 1 correspondence.

In this case, even if the update time Ti is set to a considerably short time, this device does not need to send the reconstructed image data from the magnetic disk 8 to the display control means 11 each time, and the address range of the image memory 9 is changed. Since it is only necessary to do so, it is possible to promptly deal with the update of the display image.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof.

For example, the CPU 13 stores the address of the reconstructed image data corresponding to each image number i and the elapsed time ti, calculates the update time Ti based on these, and after the predetermined elapsed time Ti has passed, the image memory 9 stores it. The reconstructed image data to be displayed may be accessed so as to be transmitted.

If the elapsed time ti is extremely long, the CPU
It is also possible to create an interpolated image on the time axis from the i-th to (i + 1) -th time and display it without waiting for the update time of the (i + 1) -th display image under the control of No. It is a useful modified example for displaying images without accompanying.

Further, when first storing a series of reconstructed image data in the image memory 9, it is possible to create the interpolated image data and use this for display.

Further, as a useful modified example of the present invention, one relating to a gate image such as a heartbeat synchronous image of the heart of the subject M can be mentioned.

This is because the electrocardiographic waveform is recorded in parallel with a plurality of X-ray CT scans, and after completion of scanning, the C for a specific phase of the electrocardiographic waveform diagram is recorded.
By collecting T scan data and reconstructing an image, a series of CT images corresponding to each phase of the electrocardiogram are obtained. In this case, it is possible to create images at relatively narrow time intervals in the vicinity of rapid changes in the shape of the heart.

When such an image is displayed, the image created at a narrow time interval by the application of the present invention updates the displayed image correspondingly, and the image created at a coarse time interval has a relatively long time. If the display image is updated at intervals, it is possible to display a gate image with no sense of time distortion.

It should be noted that this application example does not control the update interval of the display image depending on when the projection gater used for creating the image is obtained, but which time phase in the electrocardiogram waveform is displayed by the image. It means to control the update time interval of the display image depending on the meaning.

Further, in the above-described embodiment, the case where the tomographic image is displayed by the X-ray CT apparatus has been described, but the present invention is also applicable to other radiation CT apparatus, ultrasonic CT apparatus and the like.

[Effects of the Invention] According to the present invention described in detail above, a tomographic image of a subject at a desired time can be obtained, which can contribute to improvement of diagnostic ability, and a change in a specific part of the subject can be sensed with time. X-ray CT that can be displayed as an image without distortion and has great clinical significance
A device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view showing a rotation cycle, a rotation angle of an X-ray source and the like and a cutout timing of reconstructed image data in the apparatus, and FIG. FIG. 4 is an explanatory diagram showing scan timing in the apparatus, and FIG. 4 is an explanatory diagram showing scan timing in the conventional apparatus and configuration timing of a reconstructed image. 1 ... Slip ring, 2 ... X-ray tube, 3 ... X-ray detector, 4 ... Data collection unit, 5 ... High-voltage generator, 6 ... Storage unit, 7 ... Image reconstruction unit, 8 ... magnetic disk, 9 ... image memory, 10 ... display means, 11 ... display control means, 12 ... input means.

Claims (4)

[Claims] 1. A tomographic slice of a subject based on a series of X-ray transmission information obtained by irradiating the subject with X-rays from an X-ray source that can be continuously rotated around the subject and transmitting through the subject. X to get the image
In the X-ray CT apparatus, a storage unit that continuously stores the X-ray transmission information and a series of X-ray transmission information stored in the storage unit have a predetermined interval from each other, and each of the image reconstructions for one sheet A plurality of pieces of information sufficient for composition are sequentially cut out, and an image reconstruction unit for reconstructing each of them to obtain a series of reconstructed images, and a display unit for sequentially displaying the obtained series of reconstructed images are provided. Characteristic X-ray CT device. 2. The X-ray CT apparatus according to claim 1, wherein the transmitted X-ray information is obtained by converting transmitted X-ray dose or transmitted X-ray data into projection data. 3. A slice of a subject based on a series of X-ray transmission information obtained by irradiating the subject with X-rays from an X-ray source that can be continuously rotated around the subject and transmitting through the subject. X to get the image
In the X-ray CT apparatus, a storage unit that continuously stores the X-ray transmission information, and an X-ray transmission information stored in the storage unit that have a predetermined interval from each other, An image reconstructing unit that sequentially cuts out a plurality of pieces of information sufficient for composition and reconstructs each of them, an image memory that stores reconstructed image data for each reconstructed image at a predetermined address, and a time interval. X-rays comprising: a setting unit for arbitrarily setting the display unit and display control means for updating the display of the reconstructed image at the time intervals set by the setting unit based on the address on the image memory. C
T device. 4. The X-ray CT according to claim 3, wherein the display control means has a function of creating an image interpolated based on reconstructed image data when the reconstructed image is updated.
apparatus.