JP2003116836A - X-ray computed tomographic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the transfer time from the monitor scanning of the inflow of a contrast medium to the main scanning thereof in X-ray computed tomographic equipment. SOLUTION: The X-ray computed tomographic equipment is equipped with a first pair 11 having a first X-ray tube bulb 111 and a first X-ray detector 113, a second pair 12 having a second X-ray tube bulb 121 and a second X-ray detector 123 and a Z shift mechanism 13 for moving at least one of the first and second pairs along a rotary shaft. Monitor scanning operation is carried out by the first pair and main scanning operation is carried out by the second pair. The Z shift mechanism is controlled to set the distance between the first and second pairs to a distance calculated by adding the approach run distance of a top plate to the distance between a monitoring position and a start position within a photographing range or subtracting the same from the distance between both positions.

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 having a function of monitoring the inflow of a contrast agent.

[0002]

2. Description of the Related Art In imaging a contrast medium, a scan is performed by measuring the timing at which a contrast medium administered to a subject flows into an imaging range (here, it is a helical scan, and hereinafter, a monitor scan is distinguished from a main scan). It is important to. Therefore, the flow of the contrast agent is monitored by monitoring at a position upstream of the imaging range. That is, scanning is continuously repeated at the monitoring position, and the tomographic image data is immediately reconstructed from the projection data obtained thereby and displayed.

The operator observes this tomographic image, and inputs the trigger of the main scan at the timing when the degree of contrast of the blood vessel of interest becomes high to some extent. Upon receiving the trigger, the device stops the monitor scan, moves the top plate to the scan start position in the imaging range, and sets the scan conditions (X-ray exposure condition, helical pitch, etc.) of the main scan from the operator. The setup is awaited, the output voltage of the high voltage generator is switched according to the set X-ray exposure condition, the filament is preheated, and after the preparation is completed, the tube voltage and the ligature are applied to actually start the main scan. Thus, before actually starting the main scan, tabletop movement, setup, and exposure preparation are required.

The time required for these operations is not short. Therefore, it cannot be said that the situation where the start of the main scan becomes later than the preferable timing at which the contrast agent starts to flow into the imaging range does not occur. In order to avoid such a situation, it is necessary to input the trigger of the main scan at a timing when the contrast of the blood vessel of interest is not so high in consideration of the working time. , Requires very high knowledge and experience.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the deviation of the main scan start timing by reducing the transition time from the monitor scan to the main scan of the contrast agent inflow in the X-ray computed tomography apparatus. To do.

[0006]

SUMMARY OF THE INVENTION The present invention continuously scans at a monitoring position in order to monitor at the monitoring position the inflow of a contrast agent administered to a subject placed on a top plate into the imaging range. An X-ray that executes a monitor scan operation for reconstructing and displaying a tomographic image immediately and repeatedly from the obtained projection data and a main scan operation for collecting projection data of an imaging range by a helical scan while moving the tabletop. A first computerized tomography apparatus having a first X-ray tube and a first X-ray detector
Second pair having a pair, a second X-ray tube and a second X-ray detector
A pair, a first high voltage generator for applying a DC power supply to the first X-ray tube, a second high voltage generator for applying a DC power supply to the second X-ray tube, and a first pair and a second pair. A Z shift mechanism that moves at least one of the two along a rotation axis;
An image reconstruction unit that reconstructs tomographic image data based on the output of the line detector, an image display unit that displays the reconstructed tomographic image data, a monitor scan operation in a first pair, and a main scan operation in a second pair. Each pair is executed, and the Z shift mechanism is controlled so that the distance between the first pair and the second pair is the distance between the monitoring position and the start position of the photographing range, and the approach distance of the top plate is added or subtracted. And a control unit for setting.

Further, the present invention is capable of continuously repeating scanning at the monitoring position in order to monitor at the monitoring position the inflow of the contrast medium administered to the subject placed on the tabletop into the imaging range. X-ray computed tomography apparatus for executing a monitor scan operation for instantly reconstructing and displaying a tomographic image from the projected data and a main scan operation for collecting projection data of an imaging range by a helical scan with movement of the tabletop At X
Equipped with multiple pairs of X-ray tube and X-ray detector, at least one pair is separated from other pairs by a predetermined distance in the body axis direction of the subject, and monitor scan operation is performed using at least one pair Then, execute the main scan operation using the other pair.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray computed tomography apparatus (X-ray CT apparatus) according to the present invention will be described below with reference to the accompanying drawings with reference to the accompanying drawings. The scanning method of the X-ray computed tomography apparatus is X-ray tube and X-ray tube.
Rotate / rotate type that rotates around the subject as a unit with a line detector, Stationary / rotate in which a large number of detection elements arranged in a ring shape are fixed and only the X-ray tube rotates around the subject There are various types such as types, and the present invention can be applied to any type, but here, the rotate / rotate type will be described as an example. Further, in order to reconstruct one frame of tomographic image data, one set of projection data for about 360 ° around the subject, and 180 ° + fan angle for half scan method are required. It is said that Here, the former example will be described. Note that the projection data is defined as integral data relating to the passage distance of the attenuation coefficient (or absorption coefficient) of the tissue or the like on the X-ray path.

FIG. 1 shows the configuration of the main part of the X-ray computed tomography apparatus according to this embodiment. The X-ray computed tomography apparatus of this embodiment is composed of a scan gantry 1 and a computer apparatus 2. The scan gantry 1 is a constituent element for collecting projection data relating to a subject, and the projection data is fetched by the computer device 2 and used for processing such as image reconstruction. The computer device 2 includes a real prep control unit 21, and a pre-processing unit 23, an image reconstruction unit 24, an image display unit 25, a console 26 and a memory 27, which are connected to the real prep control unit 21 via a data / control bus 28. To be done.

The subject is inserted into the scan gantry 1 while being placed on the top plate 20 of the bed 10. Sleeper 10
The top plate 20 is driven by the bed driving unit 17 and moves in the longitudinal direction thereof. Usually, the bed 10 is installed so that its longitudinal direction is parallel to a rotation axis RA (which is the same as the body axis and the Z axis) described later. The top position sensor 18 is used for the top 2
It is provided to detect the position of 0, and is composed of, for example, a rotary encoder.

The scan gantry 1 is provided with a ring-shaped rotary mount (not shown) which is driven by a mount rotary drive unit 16 and rotates about a rotation axis RA. A plurality of pairs of an X-ray tube device and an X-ray detector are mounted on this rotary mount. Here, two pairs will be described. The first pair 11, which is one of them, has a first X-ray tube device 110 and a multi-channel type first X-ray detector 113 facing the first X-ray tube device 110 mounted on a rotary mount. The second pair 12 includes a second X-ray tube device 120 and a multi-channel type second opposite to the second X-ray tube device 120.
The X-ray detector 123 is mounted on the rotary mount in such a positional relationship that its central axis intersects with the central axis of the first pair 11 at the rotation axis RA at a predetermined angle (here, assumed to be 90 °).

The first X-ray tube device 110 includes a first X-ray tube 1
11 and a first X-ray filter 112 for removing low energy components to reduce exposure. Second
Similarly, the X-ray tube device 120 also includes a second X-ray tube 121 and a second X-ray filter 122. The Z shift mechanism 13 is arranged between the rotary frame and the first X-ray tube device 110 and the first X-ray detector 113. Z shift mechanism 13
Is equipped with a structure and a power source necessary for supporting the first X-ray tube device 110 and the first X-ray detector 113 so that they can move in parallel in a direction parallel or substantially parallel to the rotation axis RA.
The first X-ray tube device 110 and the first X-ray detector 113 are moved electrically by receiving power supply from the shift mechanism drive unit 19.

Inverter type high voltage generator 1 so that power can be supplied individually to the first and second X-ray tubes 111 and 121.
Two systems of 4 and 15 are provided. High voltage generator 14, 15
In addition to a high-voltage transformer, a filament current generator, and a rectifier, each has a tube voltage switch and a filament current switch for arbitrarily or stepwise adjusting the tube voltage and filament current.

The outputs of the first and second X-ray detectors 113 and 123 are reconstructed as image data as projection data via the data acquisition units 114 and 124, a slip ring (not shown) that enables continuous rotation, and the pre-processing unit 23. It is supplied to the configuration unit 24, where it is used for reconstruction processing of tomographic image data.
The tomographic image data is displayed on the image display unit 25 and is also supplied to the real prep control unit 21 to be used for the process of determining the starting point of the timing of the start of the main scan operation as described later.

The console 26 is provided for the operator to input various information such as scan conditions as described later, and instructions such as a main scan trigger and a pre-trigger described later. In addition, the memory 27 is provided to store the input scan condition data and provide it to the real prep control unit 21 in a timely manner as the imaging sequence progresses.

The control operation relating to the imaging of the contrast agent by the real prep control unit 21 will be described below. Regarding this control operation, the real prep control unit 21 is equipped with four kinds of operation modes that can be selectively used in accordance with the instruction of the operator. These four types of operation modes will be described in order.

(First Control Operation) FIG. 2 shows the procedure of the first operation control. First, scan conditions are set via the console 26 (S1) and stored in the memory 27. As shown in FIG. 3, the scan condition includes the first pair 11
Includes a monitor scan position P1, a start position P3 of an imaging range of a main scan (helical scan) by the second pair 12, and an end position P4 thereof. The scan conditions include an X-ray condition for monitor scan (a monitor scan tube voltage and a monitor scan tube current) and a main scan X-ray condition (a main scan tube voltage and a main scan tube current). Typically, the tube voltage for the monitor scan is set to be equivalent to the tube voltage for the main scan in order to make the line quality uniform.
The monitor scan tube current is set lower than the main scan tube current in order to suppress the radiation dose. Further, the scanning conditions include a top moving speed and a scan time (a time required for one rotation) as parameters for determining the helical pitch (top moving distance per one rotation).

When the scan conditions are set, the real-prep control unit 21 determines the scan surface distance ΔD between the first pair 11 and the second pair 12 as the position P1 of the monitor scan and the start position of the photographing range of the main scan. It is calculated by adding the distance DA required for an approach run from the stopped state of the tabletop to the table moving speed at the time of helical scanning to the distance to P3 (S2). If the top moving direction is opposite, as shown in FIG. 4, the first pair 11 and the second pair 1
The inter-scan-plane distance ΔD from 2 is the distance between the position P1 of the monitor scan and the start position P3 of the imaging range of the main scan until the top reaches the top moving speed during the helical scan from the stopped state. It is calculated by subtracting the distance DA required for running.

The scan surface of the first pair 11 and the second pair 12
So that the scan planes of the Z shift mechanism drive unit 1 are separated by the calculated distance ΔD.
9 is controlled (S3), and the top plate 20 is manually operated to align the specific portion of the subject with the position P1 of the monitor scan. At this time, the second pair 12 is located at the standby position P2 in front of the top plate moving direction by the approach distance DA from the start position P3 of the imaging range of the main scan.

When the above position setting is completed, the real prep control unit 21 controls the gantry rotation drive unit 16 to start gantry rotation (S4), and the first high voltage is generated according to the X-ray condition of the monitor scan. The unit 14 is set up, and at the same time, the second high voltage generation unit 15 is also set up at this stage according to the X-ray condition of the main scan. Specifically, the tube voltage selectors of the high voltage generators 14 and 15 are set according to the monitor scan tube voltage and the main scan tube voltage, respectively, and the high voltage generators 14 and 15 are set.
The filament current selectors for controlling the tube currents of No. 1 and No. 2 are set according to the monitor scan tube current and the main scan tube current, respectively, and the first and second X-ray tubes 111, 12 are also provided.
The supply of each filament heating current to No. 1 is started to preheat the filament (S5).

After the above preparatory work is completed and the rotation of the gantry reaches a constant speed, the real prep control unit 21 starts the monitor scan (S6). That is, an irradiation trigger is supplied to the first high voltage generation unit 14 to start X-ray irradiation, and a charge accumulation / readout cycle of the first X-ray detector 113,
The signal amplification, analog-digital conversion, and data read cycle of the data collection unit 114 is started. Then, the image reconstruction unit 24 is controlled to immediately reconstruct the attenuation coefficient distribution from the projection data obtained by the monitor scan as tomographic image data, and the image is displayed on the image display unit 25 (S7). This monitor scan, image reconstruction, and display are continuously repeated until stopped at S12 described later.

The operator operates the pre-trigger of the main scan by observing the tomographic image, in particular, the degree of shading of the region of interest (the blood vessel of interest) in the tomography, and observing the timing when the degree of shading becomes high to some extent. Input via the desk 26 (S
8).

In response to the pre-trigger, the real prep control unit 21 controls the bed drive unit 17 to control the top board 20.
Movement of the Z shift mechanism drive unit 19
Is controlled to start the movement of the first pair 11 in the same direction and at the same speed as the movement of the top plate (S9). With this movement, the start position P3 of the main scan range gradually approaches the standby position (main scan position) P2 of the second pair 12. During that time, the monitor scan, the image reconstruction and the display are continued, so that the operator can see the tomographic image, especially the region of interest (the blood vessel of interest) in the tomographic image.
Observing the degree of image stain, the trigger of the main scan is input through the console 26 at an appropriate timing (S10).

In response to the trigger of the main scan, the real prep control unit 21 starts the main scan (helical scan) (S11). In other words, an irradiation trigger is supplied to the second high voltage generation unit 15 to start X-ray irradiation, and a charge accumulation / readout cycle of the second X-ray detector 123,
The signal amplification, analog-to-digital conversion, and data read cycle of the data collection unit 124 are started. The start position P3 of the main scan range is the standby position P of the second pair 12.
When the trigger for the main scan is not yet input when the number reaches 2, the real-prep control unit 21 automatically starts the main scan.

This main scan is continued until the end position P4 of the main scan range reaches the standby position P2 of the second pair 12 (S12), and the end position P4 of the main scan range is the standby position P2 of the second pair 12. Upon reaching, the realprep control unit 21 stops the main scan and the monitor scan (S13).

As described above, according to this control procedure, since the scan surface of the first pair 11 and the scan surface of the second pair 12 are preliminarily separated by the distance ΔD, the waiting time accompanying the movement of the tabletop is It is possible to reduce the time required to run the top board. Further, since the monitor scan is performed by the first pair 11 and the main scan is performed by the second pair 12, it is possible to monitor the degree of stain until just before the main scan. Furthermore, since the monitor scan and the main scan are separately performed by the first and second pairs 11 and 12, the setup of the X-ray exposure can be completed in advance according to the main scan conditions, and as a result, immediately after receiving a trigger, The main scan can be started.

(Second Control Operation) The main scan trigger was manually input in the first control operation, but the second control operation is
It realizes automation after pre-trigger input. FIG. 5 shows the procedure of the second operation control. The same steps as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. Also,
In order to supplement the explanation of the second control operation, FIG. 6 shows the time variation of the tube voltage of each of the first and second X-ray tubes 111 and 121 and the time variation of the top speed. .

In this second control operation, as the scan conditions, the position P1 of the monitor scan by the first pair 11 and the start position P of the photographing range of the main scan by the second pair 12 are set.
3, the end position P4, the X-ray condition of the monitor scan, the X-ray condition of the main scan, the tabletop moving speed and the scan time for determining the helical pitch, and the main scan starts from the monitor scan stop (pre-trigger input) The delay time DLT1 up to is set (S1 '). This delay time D
LT1 is the position P of the monitor scan by the first pair 11.
From 1 to the main scan start position P3 (the same as the scan position P3 of the second pair 12 at the time T3), it is set by assuming the time required for the contrast agent to flow with the blood flow. By setting this delay time DLT1 in advance, the operator may input a pre-trigger at the time when the degree of contrast of the tomographic image becomes the optimum level for starting the main scan, that is, from the position P1 of the monitor scan. Range start position P
It is possible to eliminate the need to intentionally delay the timing of inputting the pre-trigger in consideration of the time required for the contrast agent to flow with the blood flow up to 3.

Since the operation after the pre-trigger input is automated, the real prep control unit 21 responds to the pre-trigger input in S8, and the real prep control unit 21 operates the first high voltage generator 14 and the first X voltage generator.
The line detector 113 and the first data collection unit 114 are controlled to stop the monitor scan (S21) and eliminate unnecessary exposure.

Then, the real prep control unit 21 starts moving the top 20 at a time T2 when a time DLT2 obtained by subtracting the run-up time TA from the preset delay time has elapsed from the pre-trigger input time T1 (S22). . Top 2
At the time T3 when 0 is completed, the start position P3 of the main scan range reaches the standby position P2 of the second pair 12 (S2
3) At that point, the main scan is started (S24). Since the monitor scan has already stopped, at the time when the end position P4 of the main scan range reaches the position P2 of the second pair 12 (S12), the real prep control unit 21
The main scan is stopped (S13 ').

As described above, according to the second control operation, in addition to the effect of the first control operation, by automating after the pre-trigger input, the deviation of the main scan start timing and the individual difference are eliminated. Therefore, the main scan can be stably performed.

(Third control operation) In the first control operation, the pre-trigger and the main scan trigger are manually input, and in the second control operation, the pre-trigger is input manually. It realizes such automation. FIG. 7 shows the procedure of the third operation control. The same steps as those in FIGS. 2 and 5 are designated by the same reference numerals,
The description is omitted. Further, in FIG. 8, in order to supplement the explanation of the third control operation, the first and second X-ray tubes 111, 12 are provided.
1 shows the time change of each tube voltage, the time change of the top speed, and the time change of the average CT value of the pixels in the region of interest of the tomographic image by the monitor scan.

In this second control operation, as the scanning conditions, the position P1 of the monitor scan by the first pair 11 and the starting position P of the photographing range of the main scan by the second pair 12 are set.
3, the end position P4, the X-ray condition of the monitor scan, the X-ray condition of the main scan, the top plate moving speed and the scan time for determining the helical pitch, and the main scan starts from the position P1 of the monitor scan by the first pair 11. In addition to the time required for the contrast agent to flow with the blood flow to the position P3, in other words, the delay time DLT1 from the stop of the monitor scan (pre-trigger input) to the start of the main scan, a region of interest for automating the pre-trigger, The threshold value is set (S1 ″).

The real-prep control unit 21 extracts CT values of a plurality of pixels within a preset region of interest from the tomographic image data obtained in S7, and calculates the average value thereof (S3).
1) The calculated CT value (average value) is compared with a preset threshold value (S32). When the CT value does not exceed the threshold value, it is determined that the image-shading degree at the monitoring position P1 is too low, and CT value extraction, average value calculation, and threshold values are obtained for the sequentially obtained tomographic image data. Repeat the comparison with the value.

When the CT value exceeds the threshold value T1, it is judged that the staining degree at the monitoring position P1 is appropriate, the monitor scan is stopped (S21), and similarly to S22.
The real prep control unit 21 has a time point T2 at which a CT value exceeds a threshold value at a time point T1 at which a time DLT2 obtained by subtracting the run-up time TA from a preset delay time has elapsed.
The movement of the tabletop 20 is started (S33), and the main scan is started at the time T3 (S23) when the start position P3 of the main scan range reaches the standby position P2 of the second pair 12 (S24), When the end position P4 of the main scan range reaches the position P2 of the second pair 12 (S12), the real prep control unit 21 stops the main scan (S13).
´).

As described above, according to the third control operation, in addition to the effects of the first and second control operations, complete automation including the input of the pre-trigger can be realized.

(Fourth Control Operation) In the second and third control operations, the delay time DLT1 from the stop of the monitor scan to the start of the main scan was set in advance, but the fourth control operation sets this delay time DLT1. Realprep control unit 21
Is calculated by. 9 and 10 show the procedure of the fourth operation control. The same steps as those in FIGS. 2, 5, and 7 are designated by the same reference numerals, and the description thereof will be omitted. Further, in FIG. 11, in order to supplement the explanation of the fourth control operation, the C of the pixel in the region of interest of the tomographic image data based on the projection data collected in the first pair 11 in the monitor scan is shown.
Similarly, the time change of the average T value and the time change of the average CT value of the pixels in the region of interest of the tomographic image data based on the projection data collected in the second pair 12 in the monitor scan are shown.

In the fourth control operation, the monitor scan is performed not only on the first pair 11 but also on the second pair 12. Therefore, in S5 ′, the second high voltage generator 15 is set up together with the first high voltage generator 14 according to the X-ray condition of the monitor scan.

The real prep control unit 21 includes the first and second high voltage generators 14 and 15, the first and second X-ray detectors 113 and 123, and the first and second data acquisition units 114 and 1.
24 is controlled to start a monitor scan with both pairs 11 and 12 (S41). The tomographic image data (first tomographic image data) is reconstructed based on the projection data collected by the first data collection unit 114 by the monitor scan, and in parallel with this, the second data collection unit 124 is formed by the monitor scan.
The tomographic image data (second
The tomographic image data) is reconstructed (S42).

The real-prep control unit 21 extracts CT values of a plurality of pixels within a preset region of interest from the first tomographic image data obtained in S42, and calculates the average value (first C
T value) is calculated, and in parallel with this, CT values of a plurality of pixels in the region of interest are extracted from the second tomographic image data obtained in S42, and the average value (second CT value) is calculated (S4).
1). The calculated first CT value is compared with a preset threshold CT2 (S44).

When the first CT value does not exceed the threshold value CT2, it is judged that the image-shading degree at the monitoring position P1 is too low, and the first and second CT values are obtained for the tomographic image data obtained one after another. The calculation and comparison with the first CT value threshold are repeated, and the first and second CTs at each time are repeated.
The value is stored in the memory 27. The first CT value is the threshold value C
When T2 is exceeded, the monitor scan using both kings of the first and second pairs 11 and 12 is stopped (S45).

Then, the real-prep control unit 21 calculates the delay time DLT1 based on the temporal changes in the stored first and second CT values (S46). This delay time DLT
1 is the time required for the contrast agent to flow with the blood flow from the position P1 of the monitor scan by the first pair 11 to the main scan start position P3, in other words, the degree of contrast at the monitor position P1 is a specific value ( The time difference from when the threshold value CT2) is reached to when the same scanning depth is reached at the start position P3 of the main scan is shown. Standby position P of the second pair 12
The time change of the CT value at 2 substantially follows the time change of the CT value at the monitor position P1.
CT value (CT1) at the standby position P2 of the second pair 12 at time T12 when the CT value at 1 reaches the threshold value CT2
Can be specified, the time T11 at which the CT value at the monitor position P1 is the CT1 is extracted from the stored data, and the time width from T11 to T12 can be estimated as the delay time DLT1.

When the first CT value exceeds the threshold value CT2 at time T12 and the time DLT2 obtained by subtracting the run-up time TA from the calculated delay time DLT1 elapses, the movement of the top 20 is started (S47). ), According to the X-ray condition of the main scan, the second high voltage generator 15 is set up (S48).

When the start position P3 of the main scan range reaches the standby position P2 of the second pair 12 (S23)
Then, the main scan is started by the second pair 12 (S2
4) When the end position P4 of the main scan range reaches the position P2 of the second pair 12 (S12), the real prep control unit 21 stops the main scan (S13 ').

As described above, according to the fourth control operation, in addition to the effects of the first, second, and third control operations, the delay time D from the stop of the monitor scan to the start of the main scan is increased.
The setting of LT1 can be made unnecessary.

The present invention is not limited to the above embodiment,
Various modifications are possible.

[0047]

According to the present invention, the shift of the main scan start timing can be reduced by shortening the transition time from the monitor scan of the contrast agent inflow to the main scan.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of an X-ray computed tomography apparatus according to an embodiment of the present invention.

2 is a flowchart showing a first control operation by a real prep control unit in FIG. 1. FIG.

FIG. 3 is a diagram showing the distance between the first and second pairs in FIG. 1 when the top plate moves in the forward direction.

FIG. 4 is a diagram showing the distance between the first and second pairs in FIG. 1 when the top plate moves in the opposite direction.

5 is a flowchart showing a second control operation by the real prep control unit of FIG. 1. FIG.

FIG. 6 is a diagram showing a temporal change in the tube voltage of each of the first and second X-ray tubes and a temporal change in the moving speed of the tabletop by the bed driving unit in the second control operation of FIG. 5.

7 is a flowchart showing a third control operation by the real prep control unit of FIG.

FIG. 8 is a graph showing a change in average CT value of pixels in the region of interest in the first tomographic image by the monitor scan, and the first and second X-ray tubes in the third control operation of FIG. 7; FIG. 4 is a diagram showing a time change of the tube voltage of FIG. 10 and a time change of the moving speed of the tabletop by the bed driving unit.

9 is a flowchart showing the first half of a fourth control operation by the real prep control unit in FIG.

10 is a flowchart showing the latter half of the fourth control operation by the real prep control unit in FIG.

11 is a delay time DLT1 from the stop of the monitor scan to the start of the main scan in the fourth control operation of FIG.
FIG. 6 is a diagram for explaining the calculation method of, which is a diagram showing an average time change of CT values of each of the first and second pairs.

[Explanation of symbols]

1 ... Scan gantry, 11 ... the first pair, 110 ... First X-ray tube device, 111 ... First X-ray tube, 112 ... First X-ray diaphragm device, 113 ... First X-ray detector, 114 ... the first data collection unit, 12 ... the second pair, 120 ... second X-ray tube device, 121 ... second X-ray tube, 122 ... second X-ray diaphragm device, 123 ... second X-ray detector, 124 ... the second data collection unit, 13 ... Z shift mechanism, 14 ... a first high voltage generator, 15 ... a second high voltage generator, 16 ... Frame rotation drive unit, 17 ... bed drive, 18 ... Top plate position sensor, 19 ... Z shift drive unit, 20 ... top plate, 2 ... Computer device, 21 ... Real prep controller 22 ... Data / control bus, 23 ... Pretreatment unit, 24 ... Image reconstruction unit, 25 ... image display section, 26 ... Operation console.

Continued front page    (72) Inventor Shigeyuki Nakajima             1385 Higashiyama, Shimoishi, Otawara, Tochigi Prefecture             Toshiba Nasu factory inside F-term (reference) 4C093 AA22 AA24 BA08 BA09 BA10                       EA02 EA06 EC21 EC42 ED07                       FA34 FA45 FA52 FA54 FD09                       FF28 FF29

Claims (13)

[Claims] 1. Projection data obtained by continuously repeating scanning at the monitoring position in order to monitor at the monitoring position the inflow of the contrast medium administered to the subject placed on the top plate into the imaging range. In an X-ray computed tomography apparatus, a monitor scan operation for instantly reconstructing and displaying a tomographic image from the above and a main scan operation for collecting projection data of the imaging range by a helical scan with the movement of the tabletop are performed. A first pair having a first X-ray tube and a first X-ray detector, a second pair having a second X-ray tube and a second X-ray detector, and a DC power source applied to the first X-ray tube A first high voltage generating section, a second high voltage generating section that applies a DC power supply to the second X-ray tube, and at least one of the first pair and the second pair is the rotating shaft. A Z-shift mechanism that moves along, an image reconstruction unit that reconstructs tomographic image data based on the outputs of the first and second X-ray detectors, and an image display unit that displays the reconstructed tomographic image data. , The monitor scan operation in the first pair,
The main scan operation is executed in each of the second pairs, and the Z shift mechanism is controlled to set the distance between the first pair and the second pair between the monitoring position and the start position of the imaging range. An X-ray computed tomography apparatus, comprising: a control unit that sets a distance obtained by adding or subtracting the approaching distance of the top plate. 2. The controller sets an output voltage to the second high voltage generator and starts supplying a filament heating current to the second X-ray tube before the monitor scan operation ends. The X-ray computed tomography apparatus according to claim 1. 3. The control unit controls the first and second high voltage generating units so that the X-ray energy during the monitor scan operation is lower than the X-ray energy during the main scan operation. An X-ray computed tomography apparatus according to claim 1. 4. The X-ray computed tomography apparatus according to claim 1, wherein the control unit starts the main scan operation in response to an instruction from an operator. 5. The X-ray computed tomography apparatus according to claim 4, wherein the control unit starts moving the top plate after a predetermined time delay from the instruction. 6. The X-ray computed tomography according to claim 1, wherein the control unit determines a timing to start the main scan operation based on a CT value of tomographic image data during the monitor scan operation. Imaging device. 7. The X-ray computed tomography according to claim 6, wherein the control unit determines a timing to start the main scan operation starting from a time point when the CT value exceeds a threshold value. apparatus. 8. The X-ray computed tomography apparatus according to claim 7, wherein the control unit starts the movement of the tabletop after a predetermined time delay from the time when the CT value exceeds the threshold value. . 9. The X-ray according to claim 6, wherein the control unit extracts CT values of a plurality of pixels in a region of interest from tomographic image data at the time of the monitor scan operation and calculates an average value thereof. Computer tomography equipment. 10. The X-ray computed tomography apparatus according to claim 1, wherein the control unit starts the main scan operation while continuing the monitor scan operation. 11. The control unit controls the Z shift mechanism to move the first pair at the same speed and in the same direction as the movement of the top plate at the same time as the start of the main scan operation. The X-ray computed tomography apparatus according to claim 10. 12. The control unit collects tomographic image data with the second pair during the monitor scan operation, and based on a CT value of the tomographic image data and a temporal change in the CT value of the tomographic image data collected with the first pair. 9. The X-ray computed tomography apparatus according to claim 5, wherein the delay time is determined according to the delay time. 13. Projection data obtained by continuously repeating scanning at the monitoring position in order to monitor at the monitoring position the inflow of the contrast medium administered to the subject placed on the top plate into the imaging range. In an X-ray computed tomography apparatus, a monitor scan operation for instantly reconstructing and displaying a tomographic image from the above and a main scan operation for collecting projection data of the imaging range by a helical scan with the movement of the tabletop are performed. , X
A plurality of pairs of a tube and an X-ray detector are provided, at least one pair of which is separated from another pair by a predetermined distance in the body axis direction of the subject, and the monitor scan is performed using the at least one pair. An X-ray computed tomography apparatus, wherein the main scan operation is performed using the other pair.