JP3512875B2 - 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 makes it possible to continuously display a tomographic image like a cine image in real time, like an X-ray television system, while performing continuous scanning. However, when this real-time X-ray CT is actually used in a clinical setting, the following various problems occur. In the case of angiographic diagnosis, it is necessary to start the scan well before the actual inflow because the timing at which the contrast agent flows into the region of interest cannot be determined.

Therefore, in the case of angiographic diagnosis, an object of the present invention is to provide an X-ray computed tomography apparatus capable of easily or automatically setting the timing at which a contrast agent flows into a region of interest and projection data should be collected. It is to be.

[0007]

The X-ray computed tomography apparatus according to the present invention is adapted to carry out the main scan prior to the main scan for collecting projection data relating to a region of interest of a subject placed on a movable top plate. In an X-ray computed tomography apparatus that executes a prescan for timing the inflow of a contrast agent that collects projection data with a lower dose of X-rays than a scan, one tomographic image from the projection data collected by the prescan Reconstruction means for sequentially reconstructing tomographic images in a shorter time than the time required to collect multidirectional projection data necessary for reconstruction, and a graph showing a temporal change in CT value of a part of the tomographic images. Generating means, display means for displaying the tomographic image together with the graph, a switch operated by an operator, and when the switch is operated, the pre-skip Together to end down, and a control means for shifting the main scan. X of the present invention
The X-ray computed tomography apparatus collects projection data with an X-ray of a lower dose than that of the main scan, prior to the main scan for collecting projection data of a region of interest of a subject placed on a movable top plate. In an X-ray computed tomography apparatus that executes a pre-scan for timing the inflow of a contrast agent, multi-directional projection data necessary for reconstructing one tomographic image is acquired from the projection data acquired by the pre-scan. Reconstructing means for sequentially reconstructing tomographic images in a shorter time than the time required to perform, means for sequentially generating a graph showing a temporal change in CT value of a part of the tomographic image, and displaying the tomographic image together with the graph Display means, a determination means for determining the end of the prescan based on the graph, and a display means for determining the end of the prescan. With to end the catcher down, and control means for shifting the main scan.

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

According to the present invention, the timing at which the contrast agent flows into the region of interest can be set easily or automatically.

[0014]

[0015]

[0016]

[0017]

[0018]

Embodiments will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an X-ray computed tomography apparatus (hereinafter abbreviated as “X-ray CT”) according to the first embodiment. The X-ray tube 1 and the multi-channel X-ray detector 2 are rotatably held by the gantry rotating mechanism 3 and are rotationally driven in a state of facing each other with the subject P in the imaging region interposed therebetween. X
Electric power (tube voltage, tube current) for irradiating the X-ray tube 1 is supplied from the line controller 7 to the X-ray tube 1. Data collection control unit 1
By the control of 5, the X-ray detector 2 is set to a state in which X-ray detection is possible. The rotating operation of the gantry rotating mechanism 3 is controlled by the gantry rotation control unit 4. The movement of the bed 5 for placing the bed subject P and inserting it into the imaging region is controlled by the bed control unit 6.

The projection data detected by each channel of the X-ray detector 2 is supplied to the reconstructing device 13 via the data collecting section 8 and the memory 11 in order. The reconstruction device 13 reconstructs a tomographic image from the multidirectional projection data in real time, that is, in a shorter time than the time required to collect the multidirectional projection data required to reconstruct one tomographic image. This tomographic image is sent to the image display device 14 and displayed there.

The system control unit 10 that controls the operation of the entire system includes a scan control unit 9 and a reconstruction device 13.
Are connected. The scan control unit 9 controls the gantry rotation control unit 4, the bed control unit 6, the X-ray control unit 7, and the data acquisition control unit 15 for the scanning operation. Scan control unit 9
A button switch 12 as an input means for selectively inputting ON and OFF is connected to.

Next, the operation of the present embodiment thus constructed will be described. Figure 2 shows an X-ray tube 1 for helical scanning.
Shows the spiral orbit of. The thick line indicates that the button switch 12 is in the ON state. In this embodiment, X-ray irradiation and data acquisition are performed only when the button switch 12 is in the ON state, and the tomographic images I1 to I5 are reconstructed. Here, it is assumed that the multidirectional projection data necessary for reconstructing one tomographic image is obtained while the X-ray tube 1 makes one revolution around the subject P.

FIG. 3 is a time chart of the apparatus shown in FIG. What should be noted here is that the gantry rotates continuously and the bed 5
Even if the helical movement is performed by continuously moving the button, X-ray irradiation is not performed when the button switch 12 is in the OFF state, and thus projection data is not collected. 12
That is, X-ray exposure is performed and projection data is collected only while the button is pressed by the operator and is in the ON state. However, regardless of the duration of the ON state, the button switch 1
It is preferable that the X-ray irradiation is continued while the X-ray tube 1 makes one revolution around the subject P so that at least one tomographic image can be reconstructed even when 2 is pushed once. . Since the helical motion continues even when data is not collected in this way, data collection can be performed immediately after the button operation.

The tomographic images I1 to I5 are sequentially reconstructed after a reconstruction time has elapsed from the completion of the acquisition of projection data in multiple directions necessary for reconstructing one tomographic image, and the image display device 14
Are displayed in sequence.

Until the diagnosis is finally completed, it is preferable that the bed 5 reciprocates within a predetermined range and the helical motion continues in a reverse direction. In this case, the region of interest is located in the imaging region during the reciprocating motion. The button switch 12 is set to the ON state only when it reaches, and the tomographic image of the site can be repeatedly observed.

As described above, according to the present embodiment, it is possible to irradiate only a necessary portion with X-rays, collect projection data, and reconstruct a tomographic image for observation in real time. Therefore, a tomographic image of a desired region of interest can be obtained. The radiation dose can be reduced, and the exposure time due to the restriction of the heat capacity of the X-ray tube can be effectively utilized. In the above description, the helical scan is described as an example, but it is needless to say that continuous scanning of the same position may be performed by continuously rotating the gantry while the bed 5 is stopped.

Next, the second embodiment will be described. FIG. 4 is a diagram showing the overall configuration of the X-ray CT according to the second embodiment,
The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the present embodiment, the pedestal is continuously rotated while the bed 5 is stopped, and in continuous scanning at the same position, X-ray exposure, that is, data acquisition timing is controlled by respiratory synchronization or electrocardiographic synchronization. The projection data of the respiratory phase or the cardiac phase are collected to reconstruct tomographic images of these phases.

Therefore, an electrocardiograph or respiration meter 22 is equipped. The respiratory waveform or electrocardiographic waveform measured by the electrocardiograph or respiration meter 22 is sent to the synchronous monitoring control unit 23. The synchronization monitor controller 23 monitors a specific respiratory phase or cardiac phase from the respiratory waveform or electrocardiographic waveform, and outputs a synchronous signal to the scan controller 20 when the specific respiratory phase or cardiac phase appears. The scan controller 20 receives X signals at the timing when the synchronization signal is received.
Start radiation exposure. This X-ray exposure is continued while the X-ray tube 1 capable of reconstructing at least one tomographic image makes one revolution around the subject P. In this embodiment as well, as in the first embodiment, it is preferable that the gantry continue to rotate even when it is not exposed to X-rays.

The multi-directional projection data collected in this way is reconstructed in real time by the reconstructing device 13 into a tomographic image. The tomographic image is displayed on the image display device 14. Therefore, only the tomographic image of a specific respiratory phase or cardiac phase is reconstructed and displayed.

The following two types of methods are selectively adopted as the method of determining a specific respiratory phase or cardiac phase. In the first method, X-rays are continuously exposed while the gantry 5 is continuously rotated while the bed 5 is stopped in advance, and tomographic images are sequentially reconstructed and displayed in real time. While observing this tomographic image, when the tomographic image of a desired respiratory phase or cardiac phase is displayed, the button switch 21 connected to the scan control unit 20 is operated. The scan control unit 20 compares the timing at which the projection data used for the reconstruction of the tomographic image displayed when the button switch 21 is operated with the respiratory waveform or the electrocardiographic waveform with the operator's desired specification. Recognizes the respiratory phase or cardiac phase and transmits the information of the respiratory phase or cardiac phase to the synchronous monitoring control unit 23.

In the second method, a desired threshold value for the respiratory signal or the electrocardiographic signal is set by the threshold value setting section 24. As shown in FIGS. 5A and 5B, the synchronous monitoring control unit 23 compares the electrocardiographic signal or the respiration signal measured by the electrocardiograph or the respiration meter 22 with the threshold Th as needed to determine the electrocardiographic signal. The sync signal is output at the timing t when the signal exceeds the threshold Th or at the timing t when the respiratory signal falls below the threshold Th.

As described above, according to this embodiment, only a tomographic image having a constant respiratory phase or cardiac phase can be observed in real time. In addition, since X-rays are exposed only for a period of a fixed respiratory phase or cardiac phase, the dose is reduced and
The exposure time due to the restriction of the heat capacity of the X-ray tube can be effectively utilized.

Next, a third embodiment will be described. The present embodiment supports the timing of data collection at a region of interest in angiography. FIG. 6 shows X according to the third embodiment.
It is a figure which shows the whole structure of line CT, The same code | symbol is attached | subjected to the same part as FIG. 1, and description is abbreviate | omitted. The system control unit 31 includes an operation panel 32 for inputting information about a prescan position, a prescan condition, a main scan position, a main scan condition, and a delay time from the end of the prescan to the start of the main scan. A button switch 33 for inputting timing is connected. The main scan refers to a scan of a region of interest (here, the head), and the pre-scan refers to a scan of a region where blood flow is upstream of the region of interest (here, the neck).
The delay time is set to the time for blood flow from the neck to the head.

The tomographic image reconstructed by the reconstructing device 13 is sent to the image memory 34. This tomographic image is stored in the image memory 34.
Sent to the adder 39. The CT values of all pixels in the ROI (carotid artery) set by the ROI setting unit 35 are sent from the image memory 34 to the intra-ROI CT value calculation unit 36. R
The intra-OI CT value calculation unit 36 adds these CT values and supplies the addition result to the graph generation unit 37. The graph generation unit 37 generates a graph of the change in concentration by plotting the added values from the intra-ROI CT value calculation unit 36 sequentially with the vertical axis as the level and the horizontal axis as the time. This graph is sent to the adder 39 via the image memory 38. Adder 39
Displays the tomographic image and the graph on one screen and displays them on the image display device 14
Supply to.

FIG. 7 is a block diagram of the system controller 31 shown in FIG. The prescan position and the prescan condition (mAs, scan time) are supplied from the operation panel 32 to the prescan controller 40 that controls the prescan. The trigger signal is supplied from the button switch 33 to the prescan control unit 40. The pre-scan control unit 40 receives the trigger signal and outputs a main scan start signal to the main scan control unit 42. The main scan control unit 42 is supplied with the main scan position (start position, end position), the prescan condition, and the delay time from the operation panel 32. The integrated control unit 41 receives the outputs of the pre-scan control unit 40 and the main scan control unit 42, and receives the scan-related units 4, 7,
6 and 15 are controlled.

FIG. 8 is a time chart for explaining the operation of this embodiment. 9 is a diagram showing a pre-scan and a main scan, FIG. 10 is a diagram showing a tomographic image before and after a contrast agent flows into a carotid artery in the pre-scan, and FIG. 11 shows a density change generated in the pre-scan. It is a graph shown. First, after the contrast agent is injected from the arm vein, the prescan is started. That is, with the bed 5 stopped at a position where the neck of the subject P coincides with the imaging region, the gantry rotates continuously and data collection is repeated. As a result, a tomographic image of the neck is reconstructed in real time and displayed together with the graph. The operator waits for the timing at which the contrast agent flows into the carotid artery while visually observing the concentration of the carotid artery on the tomographic image and observing the concentration change on the graph. The button switch 33 is operated at the timing when the contrast medium flows into the carotid artery. As a result, the trigger signal is output to the prescan control unit 40 and the prescan ends. At this time, the prescan control unit 40 outputs a main scan start signal to the main scan control unit 42. Upon receiving the main scan start signal, the main scan control unit 42 moves the bed 5 by the distance d between the main scan start position of the head and the pre-scan position, and matches the main scan start position of the head with the imaging region. Let In this state, it waits until the delay time t set for the time for blood flow to reach from the neck to the head elapses after the prescan is completed. However, the gantry is kept in a rotating state from the start of the prescan.

After the end of the prescan, the main scan is started at the timing when the delay time t set for the time for the blood flow from the neck to the head has elapsed. That is, while the bed 5 moves at a constant speed, X-rays are emitted and data is collected. Thereby, the tomographic images of the head are sequentially reconstructed and displayed in real time.

The time taken for the blood flow to reach the head from the neck has little individual difference, and an error is less likely to occur in a shorter time than the time taken for the blood flow to reach the head from the arm. The main scan can be started at the optimum timing when the agent has flowed in. Further, since the neck is small in size and close to the head, the inflow of the contrast agent can be sufficiently confirmed from the tomographic image with a low-dose scan, and the problem of radiation exposure is alleviated. In addition, since the change in concentration in the ROI is displayed in a graph, the inflow of the contrast agent can be confirmed more accurately.

Next, a fourth embodiment will be described. The present embodiment is a development example of the third embodiment in which the determination of the end timing of the prescan is automated. FIG. 12 is a diagram showing the overall configuration of the X-ray CT according to the fourth embodiment. The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof is omitted.

The graph generated by the graph generator 37 is
It is sent to the determination unit 50. The determination unit 50 uses one of the following three types of determination methods to determine the end timing of the prescan,
That is, the timing at which the contrast agent flows into the neck is determined and a trigger signal is output to the pre-scan control unit of the system control unit 31.

FIG. 13A shows the first judgment method. That is, the timing when the density value (CT addition value) reaches a predetermined threshold value is determined as the timing for ending the prescan. A second determination method is shown in FIG. That is, the inclination of the tangent line of the graph is monitored, and the time when the inclination angle reaches a predetermined angle is determined as the timing for ending the prescan. The inclination angle of the tangent line becomes gentle according to the inflow of the contrast medium. FIG. 13C shows the third determination method. That is, the time when the graph reaches the peak (maximum value) is determined as the timing for ending the prescan.

As described above, according to this embodiment, it is possible to automatically determine the timing of ending the prescan.
Next, a fifth embodiment will be described. Similar to the fourth embodiment, the present embodiment is a development of the third embodiment in which the determination of the timing of ending the prescan is automated. FIG. 14 is a diagram showing the overall configuration of the X-ray CT according to the fifth embodiment. The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof is omitted. FIG. 15 is a diagram showing a change with time of the output value (density value) from the difference processing unit 52.

The tomographic image reconstructed by the reconstructing unit 13 is sent to the difference processing unit 52 via the image memory 51. In the difference processing unit 52, a tomographic image (mask image) before the inflow of the contrast agent is prepared in advance.
Is held. The difference processing unit 52 subtracts the mask image from the tomographic image and adds all pixel values of the subtracted image. The result of this addition is compared with a predetermined threshold value by the threshold value processing unit 53. The threshold processing unit 53 determines when the addition result reaches the threshold as the timing of ending the prescan, and outputs a trigger signal to the prescan control unit of the system control unit 31.

As described above, according to this embodiment, it is possible to automatically determine the timing of ending the prescan.
Next, a sixth embodiment will be described. This embodiment is a development of the fourth and fifth embodiments, and is different from the fourth and fifth embodiments only in the method of determining the contrast agent inflow timing in the prescan, and is otherwise the same.

Whereas in the fourth and fifth embodiments the tomographic image is reconstructed even in the prescan, the tomographic image is not reconstructed in the prescan in this embodiment.
In the prescan, as shown in FIG. 16, X-ray exposure is repeated only when the X-ray tube is at a predetermined angular position, for example, 0 ° position. FIG. 17A is a projection data profile as mask data detected before the inflow of the contrast agent.
(B) is a projection data profile detected after the inflow of the contrast agent. The projection data profile is the projection data of each channel distributed along the channel axis.

Each time the X-ray tube makes one revolution, the projection data profile is sequentially measured, the projection data profile as the mask data is subtracted, and the difference area is sequentially measured. FIG. 17C shows the change in the difference area with time.
The sequentially measured difference areas are compared with a predetermined threshold value, and when this threshold value is reached, t1 is determined as the timing for ending the prescan (contrast agent inflow).

According to this embodiment, the same effects as those of the fourth and fifth embodiments can be obtained, and the exposure dose in the prescan is reduced as compared with the cases of the fourth and fifth embodiments. There is an effect. Of course, the projection data profiles that are sequentially measured may be sequentially displayed, and the timing of ending the prescan may be left to the operator's judgment.

Next, a seventh embodiment will be described. X-ray exposure involves heat, and the heat capacity of the X-ray tube increases with X-ray exposure time. Immediately before this heat capacity reaches the limit heat capacity, it is necessary to stop X-ray irradiation to prevent damage to the X-ray tube.
This embodiment relates to the management of the remaining time until the heat capacity reaches the limit heat capacity, so-called OLP management (overload protection management), and after actually obtaining the data necessary for the calculation of the remaining time, it is actually displayed and displayed to the operator. The remaining time is output in real time in consideration of the time difference until notification.

FIG. 18 is a block diagram of the main part of this embodiment. From the operation panel 32, data necessary for calculation of heat capacity such as initial setting of tube voltage and tube current (the same as data necessary for calculation of remaining time) is supplied to the OLP calculation / determination unit 60. In addition, the OLP calculation / determination unit 60 includes an X-ray control unit 7
The current data required for calculating the heat capacity such as the actual tube voltage and tube current supplied from the X-ray tube 1 to the X-ray tube 1 are sequentially supplied every predetermined unit time. In the present embodiment, this unit time is set to the time required to calculate the heat capacity and the remaining time after obtaining the current data required for the heat capacity calculation and to actually display the heat capacity. That is, the remaining time is repeatedly calculated in the shortest possible time and displayed in real time.

The remaining time TR according to the present embodiment is expressed by unit time T2, limit heat capacity H, current heat capacity H1, heat capacity to be added to unit time T2 H2, current tube voltage K, current tube current. Where A is the heat capacity conversion constant and R is the heat capacity conversion constant, TR = (H-H1-H2) / (K * A * R).

Therefore, since the heat capacity to be added to the unit time T2 is subtracted from H-H1 to calculate the remaining time, the actual remaining time at the displayed time is obtained. TR1 in FIG. 20 is the remaining time displayed at a certain time, and
R2 is the remaining time displayed at the time when a unit time has passed from a certain time, and the remaining time is repeatedly displayed every unit time in this way, and this remaining time is the time difference required for calculation processing at the time of display. Has been taken into consideration.

When the calculated remaining time becomes less than the fixed time, the remaining time information is output from the OLP calculation / determination unit 60 to the display control / ramp sound control unit 61, and the output means is controlled by the display control / ramp sound control unit 61. It is output from 62. The output means 62 includes a monitor, a lamp, and a buzzer, and when the remaining time is short, the remaining time is displayed on the monitor as shown in FIG. 19A, the lamp is turned on, and a sound is output from the buzzer. , Give the operator a warning. Note that, as shown in FIG. 19B, it is preferable to display various messages such as continue, stop, and change according to the amount of remaining time. The change is a message prompting to reduce the X-ray dose by changing the exposure conditions such as the tube current and the tube voltage. When the exposure conditions such as the tube current and the tube voltage are changed during the scan, the tendency of increasing the heat capacity is suppressed as shown in FIG. 21, and as a result, the remaining time is extended from before the change.

Further, since the initial stage of scanning is the stage of alignment, even a tomographic image with poor image quality may be used. Therefore, X-ray exposure is performed at a relatively low dose, and after the alignment is completed, an X-ray exposure is performed at a relatively high dose. In some cases, a tomographic image with good image quality is obtained by irradiating the same, but in this case, as shown in FIG.
The remaining time T1 when the current X-ray exposure condition (relatively low dose) is continued at the alignment stage and the remaining time T1 when the X-ray exposure condition is changed to relatively high dose at the present time It is preferable to calculate both and display them on the monitor simultaneously.

Next, the eighth embodiment will be described. FIG. 23
FIG. 7 is a diagram showing an overall configuration of an X-ray CT according to a seventh embodiment, the same parts as those in FIG. In this embodiment, a cone-beam X-ray tube 72 that emits pyramidal cone-beam X-rays and a plurality of X-ray detection elements are arranged two-dimensionally according to the arrival range of the cone-beam X-rays. The X-ray detector 73 is adopted.

The scan mode and the scan mode are selectively designated by the mode changeover switch 70 connected to the scan controller 71. FIG. 24 is a time chart showing the operation of this embodiment. Scano mode is initially selected to confirm the scan position. Even in the scan mode, the X-ray tube 72 is rotated around the subject P as in the scanning operation. However, the X-ray irradiation is intermittently repeated only when the X-ray tube 72 is at the predetermined angular position, here, at the 0 ° position. The projection data detected by each X-ray detection element is individually converted into a luminance signal,
The image is displayed on the image display device 14 as a scanogram similar to the X-ray image of the indirect radiography.

The operator determines the scan position and the scan timing (in the case of contrast imaging) from the scanogram, and the operator operates the mode changeover switch 70 to switch from the scanogram mode to the scan mode. Immediately after this switching, X-rays are continuously emitted and the scanning operation is started. This is because the X-ray tube 72 is continuously rotating from the scano mode. The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0056]

According to the present invention, the timing at which the contrast medium flows into the region of interest can be set easily or automatically.

[0057]

[0058]

[0059]

[0060]

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment device.

FIG. 2 is a diagram showing a spiral orbit of an X-ray tube by a helical scan.

FIG. 3 is a time chart showing the operation of the first embodiment.

FIG. 4 is a configuration diagram of a second embodiment device.

FIG. 5 is a diagram showing threshold processing.

FIG. 6 is a configuration diagram of a third embodiment device.

FIG. 7 is a block diagram of a system control unit in FIG.

FIG. 8 is a time chart showing the operation of the third embodiment.

FIG. 9 is a diagram showing a positional relationship between prescan and main scan.

FIG. 10 is a diagram showing changes in tomographic images before and after the inflow of a contrast agent.

FIG. 11 is a concentration change graph in the ROI.

FIG. 12 is a configuration diagram of a fourth embodiment device.

FIG. 13 is a diagram showing the principle of determining the prescan end timing according to the fourth embodiment.

FIG. 14 is a configuration diagram of a fifth embodiment device.

FIG. 15 is a diagram showing the principle of determining the prescan end timing in the fifth embodiment.

FIG. 16 is a diagram showing an X-ray exposure timing according to the sixth embodiment.

FIG. 17 is a diagram showing changes in the projection data profile before and after the inflow of a contrast agent.

FIG. 18 is a block diagram of the main part of the seventh embodiment device.

FIG. 19 is a diagram showing a display screen.

FIG. 20 is a diagram showing a repeated display of remaining time.

FIG. 21 is a diagram showing changes in the heat capacity increasing tendency when the exposure conditions are changed.

FIG. 22 is a diagram showing the remaining time before and after changing the exposure condition.

FIG. 23 is a configuration diagram of an eighth embodiment device.

FIG. 24 is a time chart showing the operation of the eighth embodiment.

[Explanation of symbols]

1 ... X-ray tube, 2 ... X-ray detector, 3 ... Frame rotating mechanism, 4 ...
Gantry rotation control unit, 5 ... bed, 6 ... bed control unit, 7 ... X-ray control unit, 8 ... data acquisition unit, 9 ... scan control unit, 10
... system control unit, 11 ... memory, 12 ... button switch, 13 ... reconstruction device, 14 ... image display device, 15 ... data collection control unit.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Yamanas 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock Company, Toshiba Nasu Plant (72) Inventor Masakuni Fujise 1385-1 Shimoishi, Otawara, Tochigi Company Toshiba Nasu Factory (72) Inventor Yusuke Higashi 1-1 1-1 Shibaura, Minato-ku, Tokyo Stock company Toshiba Head Office (72) Inventor Yoshihiko Aoji 1385-1 Shimoishi, Otawara, Tochigi Toshiba Nasu Factory (72) Inventor Tatsuya 1385-1 Shimoishigami, Otawara, Tochigi Prefecture Toshiba Nasu Factory (72) Inventor Tetsuro Hada 1385-1 Shimoishi, Otawara, Tochigi Toshiba Nasu Factory, Ltd. (72) Inventor Manabu Hiraoka 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock company Toshiba Nasu factory (72) Inventor Takeo Amao, 1385 Shimoishi-kami, Otawara, Tochigi 1 Toshiba Medical Engineering Co., Ltd. (72) Inventor Ryo Hayashibara 1385-1 Shimoishigami, Otawara-shi, Tochigi Prefecture Toshiba Medical Engineering Co., Ltd. (56) Reference JP 4-292148 (JP, A) JP 63 -29626 (JP, A) JP-A-3-53772 (JP, A) JP-A-2-224647 (JP, A) JP-A-62-281928 (JP, A) JP-A-2-246935 (JP, A) ) (58) Fields surveyed (Int.Cl. ⁷ , DB name) A61B 6/00-6/14

Claims (6)

(57) [Claims] 1. A contrast agent for collecting projection data with X-rays of a lower dose than the main scan, prior to the main scan for collecting projection data on a region of interest of a subject placed on a movable top plate. In an X-ray computed tomography apparatus that executes a pre-scan for determining the inflow timing of multi-directional projection data, multi-directional projection data necessary for reconstructing one tomographic image is obtained from multi-directional projection data collected by the pre-scan. Reconstructing means for sequentially reconstructing tomographic images in a shorter time than the time required for collecting, means for sequentially generating a graph showing a temporal change of a CT value of a part of the tomographic image, and the tomographic image together with the graph. Display means for displaying, a switch operated by an operator, and when the switch is operated, the prescan is ended and the main scan is performed. X-ray computed tomography apparatus characterized by comprising a control means for causing. 2. The X-ray computed tomography apparatus according to claim 1, wherein the control unit starts the main scan after a lapse of a predetermined time from the end of the prescan. 3. A contrast agent for collecting projection data with X-rays of lower dose than the main scan, prior to the main scan for collecting projection data on a region of interest of a subject placed on a movable top plate. In an X-ray computed tomography apparatus that executes a pre-scan for determining the inflow timing of the multi-directional projection data, multi-directional projection data necessary for reconstructing one tomographic image is obtained from the multi-directional projection data collected by the pre-scan. Reconstructing means for sequentially reconstructing tomographic images in a shorter time than the time required for collecting, means for sequentially generating a graph showing a temporal change of a CT value of a part of the tomographic image, and the tomographic image together with the graph. Display means for displaying, determination means for determining the end of the prescan based on the graph, and the prescan when the end of the prescan is determined Together to end, the X-ray computed tomography apparatus characterized by comprising a control means for shifting the main scan. 4. The X-ray computed tomography apparatus according to claim 3, wherein the determination unit determines the end of the prescan when the CT value reaches a predetermined threshold value. 5. The X-ray computed tomography apparatus according to claim 3, wherein the determination unit determines the end of the prescan when the CT value reaches a peak value. 6. The X-ray computed tomography apparatus according to claim 3, wherein the determination unit determines the end of the prescan when the inclination angle of the tangent line of the graph reaches a predetermined angle. .