JP2003310597A - X-ray ct system, scan method therefor, and software recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT system with which a contrast image is obtained in a suitable timing, an examination time is shortened and exposures onto an examinee body are reduced. <P>SOLUTION: The X-ray CT system is provided with an X-ray generating means for generating a first X-ray in a pre-scan mode and generating a second X-ray in a main scan mode, an X-ray detecting means for detecting a first transmitted X-ray to be radiated for a first irradiation width along a body axis by transmitting the first X-ray generated at a first scan position in the pre-scan mode through the examinee body and for detecting a second transmitted X-ray to be radiated for a second irradiation width wider than the first irradiation width along the body axis by transmitting the second X-ray generated at a second scan position in the main scan mode through the examinee body, a control means for controlling the first and second scan positions, and a display means for displaying first and second images based upon the first and second transmitted X-rays. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus capable of performing a multi-slice scan to obtain a medical image,
The present invention relates to a scanning method in the apparatus and a software recording medium that records software for implementing the method.

[0002]

2. Description of the Related Art In recent years, an X-ray CT apparatus has been known as one of apparatuses for obtaining an image of an object to be examined based on an X-ray intensity transmitted through a medical examination target such as a patient (hereinafter referred to as an object). There is. The images obtained by the X-ray CT apparatus play an important role in many medical procedures including diagnosis of diseases, treatment, surgery planning, and the like. As the latest technology by the X-ray CT apparatus, for example, imaging by a real-time image reconstruction technology or a multi-slice scanning technology is becoming popular.

In the real-time image reconstruction technique, when reconstructing an image, for example, a part of the projection data obtained for the previous image is used as a part of the projection data for the image so that the image data is collected and substantially processed. Image reconstruction processing based on the image data at the same time (real time). The projection data is data obtained by scanning a predetermined part of the subject. This scan rotates the X-ray tube and the X-ray detector around the subject while irradiating the subject with X-rays from the X-ray tube, and the X-rays transmitted through the subject are detected by the X-ray detector. It is done by getting. Even if the display time is taken into consideration by performing real-time image reconstruction processing,
It is possible to display the reconstructed image almost simultaneously (in real time) with the scanning of the image. Regarding such a real-time image reconstruction technique, for example, Patent No. 3
No. 090400 is described in detail.

By the way, in medical image diagnosis, examination using a contrast agent is also performed. By injecting a contrast agent into a subject to highlight a predetermined region (for example, a specific organ) of the subject to make it easier to recognize the region and to determine the presence or absence of a tumor in the region. I am offering it to. Such a contrast image with a contrast agent can also be obtained by an X-ray CT apparatus. However, as a practical matter, it usually takes some time from the injection of the contrast agent to the predetermined (desired) site of the contrast agent, and it is difficult to obtain an image enhanced in a more preferable form. It wasn't easy. In some cases, the contrast agent may be scanned before reaching the predetermined site, and in other cases, the contrast agent may be scanned after passing through the predetermined site.

As one of the solutions to the above problems, it may be considered to incorporate the above-mentioned real-time image reconstruction technique into the examination using the contrast agent. The following is an example of a contrast agent examination that incorporates a real-time image reconstruction technique.

First, a monitoring scan (hereinafter referred to as a prescan) is performed near the predetermined portion. This prescan is useful for monitoring that the image enhancement by the contrast agent appears near the predetermined site. When the image enhancement by the contrast agent appears in the pre-scan, an image scan (hereinafter referred to as a main scan) in the predetermined region is performed in response to the pre-scan in the predetermined region to obtain a contrast image. Since the real-time image reconstruction technique is used in the prescan, the image acquired by the scan can be displayed in substantially real time, and the image enhancement by the contrast agent can also be displayed in monitor in real time. Therefore, it is possible to easily grasp the preferable (correct) transition timing in the transition from the pre-scan to the main scan.

The above-mentioned method may have no problem in the pre-scan and the main scan by the single slice which are found in the conventional X-ray CT apparatus. However,
From another perspective, single-slice scanning is not very desirable. When the single-slice scan is performed in the main scan, the scan time is relatively long because the portion to be main-scanned is performed in a range having a certain width. As the scan time becomes longer, there is a problem that not only the entire examination time, that is, the restraint time of the subject becomes longer, but also the exposure dose of the subject increases.

As a method that can shorten the examination time and reduce the exposure to the subject, there is an image acquisition method using the multi-slice scanning technique mentioned above. The multi-slice scan is a technique that makes it possible to obtain projection data at a plurality of positions (a plurality of slices) for a subject in one scan (one rotation) (for example, Patent Document 1).
Through 3).

[0009]

[Patent Document 1] JP-A-10-127621 (for example, page 6)

[Patent Document 2] US Pat. No. 5,459,769 (for example, columns 4 and 5)

[Patent Document 3] US Pat. No. 5,612,985 (for example, columns 17 and 18)

[0010]

When the multi-slice scan is replaced with the single scan described above, the scan time and the exposure of the subject can be reduced in the main scan. On the other hand, however, the pre-scan is only for monitoring the appearance of the image enhancement by the contrast agent, and therefore does not require the multi-slice scan over a relatively wide range. In other words, performing a multi-slice scan in the pre-scan is
As compared with the case of the single scan, there arises a problem that the dose of the subject is increased.

The present invention has been made in view of the above problems, and makes it possible to obtain a contrast image at an appropriate timing in an inspection using a contrast agent, and to shorten the inspection time and reduce the inspection time as compared with the conventional method. An object of the present invention is to provide an X-ray CT apparatus capable of reducing the exposure of a specimen.

[0012]

In order to achieve the above object, an X-ray CT apparatus according to the present invention according to claim 1 generates a first X-ray in a pre-scan mode and a second X-ray in a main scan mode. X-ray generating means for generating X-rays, and a first X-ray generated in the first scan position in the pre-scan mode are transmitted through the subject so that the first X-rays along the body axis of the subject are detected. The first transmitted X-rays irradiated with the irradiation width of 1 are detected, and the second X-rays generated at the second scan position in the main scan mode are transmitted through the object to detect the object. X-ray detection means for detecting a second transmitted X-ray that is irradiated along a second irradiation width wider than the first irradiation width along the body axis of the sample;
And a control means for controlling a second scan position, a first image is displayed based on the first transmitted X-ray, and a second image is displayed.
And a display unit for displaying the second image based on the transmitted X-ray.

Further, in order to achieve the above object, a second aspect is provided.
In the X-ray CT apparatus of the present invention described in 8, an X-ray source for irradiating X-rays while rotating around the subject, and a collimator width for determining an X-ray irradiation width to the subject are provided. A collimator that can be changed in the body axis direction, a multi-row detector in which a plurality of detection elements that detect X-rays that have passed through the subject are arranged in the body axis direction, and data that collects output data of the detection elements. A data acquisition device in which a plurality of acquisition elements are arranged in the body axis direction, an execution unit that executes a scan of the subject using the X-ray source and the X-ray detector, and a CT of a region of interest of the subject Control for controlling the collimator so that the prescan for monitoring the value shifts to the main scan for scanning the imaging region of the subject and the collimator width for the prescan is narrower than the collimator width for the main scan Stage, and reconstruction for reconstructing a tomographic image of the subject based on the projection data collected by the prescan, and for performing image reconstruction of the subject based on the projection data collected by the main scan. And means.

Further, in order to achieve the above object, a scanning method of an X-ray CT apparatus according to the present invention is a method for generating a first X-ray in a prescan mode, and a first X-ray in the prescan mode. When the first X-ray generated at the scan position passes through the subject, X
Detecting a first transmitted X-ray that is emitted in a first irradiation width along the body axis of the subject of the line detector, and displaying a first image based on the first transmitted X-ray, A second X-ray is generated in the main scan mode, and the second X-ray generated at the second scan position in the main scan mode passes through the subject to cause the X-ray detector to detect the second X-ray. A second, wider than the first irradiation width, along the body axis of the subject
Of the second transmitted X-rays, the second image is displayed based on the second transmitted X-rays, and the first transmitted X-rays are displayed.
And controlling the second scan position.

Furthermore, to achieve the above object, the software recording medium of the present invention according to claim 34 can be mounted in an X-ray CT apparatus, and is executed when a scan is performed in this X-ray CT apparatus. In a software recording medium in which software for controlling an X-ray CT apparatus is recorded, first X-rays are generated in a prescan mode, and the first X-rays generated at a first scan position in the prescan mode. When the X-rays pass through the subject, the X-ray detector detects the first transmitted X-rays with a first irradiation width along the body axis of the subject, and the first transmitted X-rays are detected. The first image is displayed based on the above, and the second X-rays are generated in the main scan mode, and the second X-rays generated at the second scan position in the main scan mode are The second transmitted X-ray that is emitted to the second irradiation width wider than the first irradiation width along the body axis of the object of the X-ray detector is detected by transmitting the object. , Software for displaying a second image based on the second transmitted X-ray and controlling the first and second scan positions.

According to the present invention as described above, it is possible to obtain a contrast image at an appropriate timing in an examination using a contrast agent, and shorten the examination time and the exposure of the subject as compared with the conventional case. Is possible.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an X-ray CT according to an embodiment of the present invention.
It is a block diagram which shows the structural example of an apparatus. In the figure,
The X-ray CT apparatus is composed of a gantry section 100, a control section 101, an operation section 102, and a data processing section 103. Gantry section 1
00 is for performing imaging on the subject P. The control section 101 is for controlling the gantry section 100 and the data processing section 103, for example. The operation section 102 is used by a doctor or a radiological technologist (hereinafter referred to as an operator) to input and operate various information. Data processing section 103
Is for performing various types of data processing including image reconstruction processing.

The gantry section 100 is an X-ray tube 1, X
A line detector 2, a rotation mechanism 3, and a bed 4 are included. X-ray tube 1
Irradiates (generates) X-rays on the subject P lying on the bed 4. The X-ray detector 2 is composed of a plurality of detection elements arranged two-dimensionally. That is, in the X-ray detector 2,
A plurality of detection elements along the body axis of the subject P (hereinafter referred to as the body axis direction), and a plurality of detection elements in a direction orthogonal to the body axis direction (hereinafter referred to as the channel direction), Each is provided to form a two-dimensional array. In the following description, the detection element when viewed in the body axis direction will be described unless otherwise specified. Therefore, description of the detection element in the channel direction is omitted. The X-ray detector 2 detects the X-rays that have passed through the subject P as a result of being irradiated to the subject P from the X-ray tube 1. The detected data is output from the X-ray detector 2.
The rotating mechanism 3 holds the X-ray tube 1 and the X-ray detector 2 so as to face each other on opposite sides of the subject P. Further, the rotation mechanism 3 includes the X-ray tube 1 and the X-ray detector 2 as the subject P.
Rotate around. The rotating mechanism 3 is usually fixed at a predetermined position, but it may be movable in the body axis direction and / or the channel direction, if necessary.
The bed 4 is for the subject P to lie down for examination. The bed 4 is movable in the body axis direction and the channel direction, and is a predetermined portion (inspection portion) of the subject P in the inspection.
It is possible to position the so that it is at an appropriate position. Further, the bed 4 is also movable in the vertical direction with respect to the floor surface on which the X-ray CT apparatus is installed.

The control section 101 includes a rotation control unit 5, X
The line control unit 6, the bed control unit 7, the detector control unit 8, the scan control unit 9, and the system control unit 10 are included. The rotation control unit 5 controls the rotation mechanism 3 to rotate or end the rotation. The X-ray control unit 6 controls power supply to the X-ray tube 1 and controls X-ray irradiation under a predetermined condition. Further, the X-ray control unit 6 also controls a collimator described later to change the X-ray irradiation angle, and the X-ray transmitted through the subject P has a predetermined range of the X-ray detector 2, particularly a predetermined range in the body axis direction. The X-rays emitted from the X-ray tube 1 are restricted so that the X-rays are emitted in the width. The rotation control unit 5 or the X-ray control unit 6 controls the position of the X-ray tube 1 so that the X-ray tube 1 moves (shifts) toward the X-ray detector 2 (in the direction orthogonal to the body axis direction). You may do it. With such movement, it is possible to change the range (width) of X-ray irradiation, so that the same effect as when the collimator is controlled can be obtained.

Next, the bed control unit 7 controls the bed 4 so as to move in a three-dimensional direction. The detector control unit 8 uses the X-ray detector 2
Is controlled to change the detection timing or the like. The scan control unit 9 controls the rotation control unit 5, the X-ray control unit 6, the bed control unit 7, and the detector control unit 8 so that the above control by these control units is realized. Scan control unit 9
The data collection unit (hereinafter referred to as DAS (DATA AC
QUISITION SYSTEM) section 13) is also controlled. The control of the DAS unit 13 will be described later.
The system control unit 10 controls the entire X-ray CT apparatus. In particular, the system controller 10 controls the scan controller 9. Other control operations by the system control unit 10 will be described later.

The operation section 102 is a button switch 1
1 and an operation panel 12. The button switch 11 is connected to the system control unit 10 and is used, for example, to input a prescan end instruction. The prescan will be described later. The operation panel 12 allows information to be input by its operation. For example, the prescan position,
Pre-scan condition, main scan position, main scan condition,
Information such as the delay time from the end of prescan to the start of main scan can be input. In addition,
The delay time can be defined as the time difference between the end of the prescan and the start of the main scan. The main scan will be described later.

The data processing section 103 is the DAS.
Unit 13, memory 14, reconstruction unit 15, image memory 16,
Region of interest setting section (hereinafter, ROI (REGION OF
INTEREST) setting section) 17, CT value calculation section 18, graph generation section 19, image memory 20, adder 2
1 and the image display device 22. The DAS unit 13 includes a plurality of data collection elements (hereinafter referred to as DAS elements), and collects the data detected by the X-ray detector 2 according to the connection state between the detection element and the DAS element. The collection result depends on how the detector element is connected to the DAS element. This connection may be switched or controlled by an analog switch. The analog switch will be described later. DAS section 1
3 outputs the collected data as projection data. The memory 14 stores the projection data output from the DAS unit 13. The reconstruction unit 15 is controlled by the system control unit 10 and executes an image reconstruction process based on the projection data stored in the memory 14. By this execution, a reconstructed image (hereinafter referred to as a tomographic image) is generated.

The image reconstruction processing by the reconstruction unit 15 is executed substantially in real time with respect to the data acquisition. Here, the real-time image reconstruction as referred to in the present invention is "a plurality of directions around the subject P (for example, 360 degrees) (a sufficient number or a necessary number of directions in the image reconstruction).
The tomographic image T is reconstructed on the basis of the projection data obtained from the Configure ”. In fact, as one example of this image reconstruction, the projection data obtained at a first predetermined angle around the subject P and the projection data already collected for the previous image (the first predetermined It is conceivable to perform image reconstruction using (excluding the data of the portion corresponding to the angle).

The image memory 16 stores the image-reconstructed data as a tomographic image. The ROI setting unit 17 determines a region of interest (RO) for the tomographic image stored in the image memory 16.
Set I). The region of interest (ROI) is a region that has been determined to be noteworthy in diagnosis. The CT value calculation unit 18 calculates the average CT value in the region of interest (ROI) for each tomographic image stored in the image memory 16. The graph generation unit 19 creates a graph in which the CT value calculated for each tomographic image is displayed as a curve along the time axis. This graph is updated every time the CT value is calculated for each tomographic image.
The image memory 20 stores this graph. The adder 2
1 is a graph stored in the image memory 20
Add to the tomographic image saved in 6. The image display device 22 displays the added tomographic image and graph on its monitor. In fact, each tomographic image corresponding to each scan slice is displayed in real time with the graph. For example, as shown in FIG. 7, this graph shows CT values corresponding to each tomographic image together with past CT values.

Next, the system controller 10 will be described in detail with reference to FIG. FIG. 2 is a block diagram showing a configuration example of the system control unit 10 according to the embodiment of the present invention. As shown in the figure, the system control unit 10 includes a pre-scan control unit 31, a main scan control unit 32, and a general control unit 33. The prescan control unit 31 is connected to the button switch 11 and the operation panel 12. Further, the prescan control unit 31 may be connected to the CT value calculation unit 18. The main scan control unit 32 is connected to the operation panel 12.

The prescan controller 31 receives an instruction signal for instructing the end of prescan from the button switch 11. This instruction signal is generated, for example, in response to the operator pressing the button switch 11. The prescan control unit 31 also receives the information input on the operation panel 12. The information received by the prescan control unit 31 includes a prescan position and prescan conditions (for example, an X-ray tube current, a slice thickness, and a scan time if necessary). The pre-scan position and the pre-scan condition received by the pre-scan control unit 31 are given to the general control unit 33, and the gantry section 1 further ahead is provided.
00. As a result, the prescan is performed according to the prescan position and the prescan condition.

During the prescan, the operator observes the CT value in the graph and / or the change in the ROI of the tomographic image displayed on the image display device 22. CT
When the operator determines that the value has reached a predetermined reference value, or when the operator has determined that the contrast agent has sufficiently reached the pre-scan slice position as shown in FIG. 6, for example, the operator presses the button switch 11. Push. The button switch 11 generates an instruction signal, and in response to this instruction signal, the prescan control unit 31 notifies the general control unit 33 that the prescan should be ended. As a result, the generation of X-rays in the prescan is stopped by the X-ray tube 1. Further, the prescan control unit 31 notifies the main scan control unit 32 that the prescan has ended.

Instead of the instruction signal from the button switch 11, an alternative instruction signal may be given from the CT value calculation section 18. That is, in the case where the CT value calculation unit 18 has a function of determining whether the calculated CT value has reached a predetermined reference value and notifying the prescan control unit 31 of the fact that the CT value has reached a predetermined reference value. The prescan control unit 31
May receive the notification as an alternative instruction signal and operate similarly to the above case. In this way, if the alternative instruction signal is automatically generated (not by the operator pressing the button switch 11), the button is pressed at an appropriate timing when the operator finishes the prescan and shifts to the main scan. Even if the switch 11 is not pressed down, it is possible to avoid missing this timing. Actually, both the button switch 11 (instruction signal) and the automatic notification function (alternative instruction signal) are provided so that the operator can select either one of them according to the preference of the operator, or both. May be used together.

The main scan control unit 32 receives the information input on the operation panel 12, as with the prescan control unit 31. The information received by the main scan control unit 32 includes a main scan position and a main scan condition. The main scan position information may include the start position and the end position of the main scan. The main scan condition information may include an X-ray tube current, a slice thickness, and a delay time in the main scan. The main scan position and the main scan condition received by the main scan control unit 32 are given to the general control unit 33, and further supplied to the gantry section 100 in the future. As a result, the main scan can be performed according to the main scan position and the main scan conditions.

As described above, the delay time is the time difference between the end of the prescan and the start of the main scan. The delay time determines how long after the end of the prescan the main scan should be started. Shown.
The delay time may be decided based on the experience of the operator. Further, the delay time is the distance between the pre-scan position and the main scan position of the subject P, the inspection site,
It may vary depending on the like. Prescan control unit 3
When a predetermined delay time elapses from the notification from 1, the main scan control unit 32 notifies the general control unit 33 that the main scan should be started. As a result, the main scan is started in the gantry section 100.

The general controller 33 is connected to the scan controller 9 and the reconstruction unit 15.

FIG. 3 is a diagram showing an example of the prescan position and the main scan position according to the embodiment of the present invention. Figure 3
In, the pre-scan position PP is set on the neck of the subject P. The main scan position IP is set on the head of the subject P. As can be seen from FIG. 3, the prescan position PP is fixed at one position. The purpose of this pre-scan is to monitor whether the injected contrast agent has reached the pre-scan position (ie indicating that the contrast agent will soon reach the main scan position). Because. In the example shown in FIG.
The pre-scan position PP and the main scan start position IIP are separated by a distance d. Therefore, when the pre-scan ends at the pre-scan position PP, the bed 4 is moved along the body axis of the subject P in the foot direction of the subject P by the distance d.
You should be able to move.

FIG. 4 is a diagram showing an example of a data collection pattern according to the embodiment of the present invention. As described above, the X-ray detector 2 is composed of a plurality of detection elements arranged two-dimensionally. The number of detection elements may differ depending on the type of detector. Eight detection elements a to h of the X-ray detector 2 are shown in FIG. This means that the X-ray detector 2 includes at least eight detection elements a to h in the body axis direction. When these eight detection elements are in a usable state for detection, this is defined here as a slice width composed of eight detection elements. The detection data of the detection elements a to h is collected by the DAS unit 13. It should be noted that the data collection result will be different as described above by switching by the analog switch provided between the X-ray detector 2 and the DAS unit 13.

In FIG. 4, two adjacent detection elements (for example, detection element a and detection element b, detection element c and detection element d,
When the detection element e and the detection element f, and the detection element g and the detection element h) are bundled by switching by the analog switch, the data collection result is four segments A, B, C, and
D (pattern (i)). Each segment will use the detection data from each two detectors and will have a slice thickness twice the width of the detectors. One segment corresponds to one slice in the multi-slice scan. Therefore, in pattern (i), the X-ray acquisition is performed with a slice width of eight detection elements, the slice width includes four slices, and each slice has a slice thickness corresponding to two detection elements. It will be.

In the prescan, the next pattern (i
i) may be used. In pattern (ii), only four detection elements c to f are used for detection.
When two adjacent detection elements (for example, detection element c and detection element d, and detection element e and detection element f) are bundled by switching by an analog switch, the data collection result is composed of two segments B and C. It will be.
Each segment (slice) will have a slice thickness twice the width of one detector element. Therefore, in the pattern (ii), X-ray acquisition is performed with a slice width of four detection elements, the slice width includes two slices, and each slice has a slice thickness corresponding to two detection elements. It will be. The slice width is because the pre-scan does not require a wide range of scans, as the pre-scan is performed only to monitor the arrival of the contrast agent. Furthermore, it is also important in the sense of avoiding unnecessary exposure to the subject.

By the way, the pre-scan is often performed with X-rays weaker than the main scan. Therefore, in order to improve the image quality of the tomographic image displayed on the image display device 22, it is effective to bundle the two detection elements in the prescan. Another reason is that the contrast medium flows with blood and the arteries monitored in the ROI are often very thin, so if the image quality is poor, it may not be easily visible even if the contrast medium appears.

On the other hand, the following pattern (iii) can be applied to the main scan. In the pattern (iii), bundling of the detection elements is not performed, so the data collection result is 8
Each segment (slice) has one slice a to h and has a slice thickness equal to the width of one detection element. As a result, a wide range of scans can be performed with one rotation, and the main scan can be completed in a shorter time than when the main scan is performed under the condition of the pattern (ii). A short time scan is X of the subject P
It is also effective in reducing the radiation exposure. As described above, in the pattern (iii), the X-ray acquisition is performed with the slice width of eight detection elements, the slice width includes eight slices, and each slice has the slice thickness corresponding to one detection element. It will be.

The prescan in the pattern (ii) will be described in detail below with reference to FIG. FIG. 5 is a block diagram showing a configuration relating to X-ray detection and data acquisition in prescan according to the embodiment of the present invention. In order to make it easier to imagine having a slice thickness corresponding to the width resulting from the bundling of two detectors, the X-ray detector 2 in FIG. 5 has four detection segments DE12, DE34, DE.
56, DE78. For example,
The detection segment DE34 means that the detection elements DE3 and DE4 are bundled. As described with reference to FIG. 4, the prescan is performed by a two-slice scan. At this time, in the X-ray tube 1, X-ray irradiation is performed so that the transmitted X-rays transmitted through the subject P by the irradiated X-rays are irradiated to the detection segment DE34 and the detection segment DE56. Therefore, for example, the detected segment DE34
Corresponds to the first slice, and the detected segment DE56 corresponds to the second slice. In other words, regarding the first slice in the pre-scan, the first transmitted X-ray transmitted through the first portion of the subject P is the detection segment D.
The second transmitted X-ray detected at E34 and similarly transmitted through the second part of the subject P for the second slice is detected at the detection segment DE56.

The X-ray data detected by the detection segments DE34 and DE56 is given to the DAS section 13 via the analog switch 50. Analog switch 50 is X
The detection element D is provided between the line detector 2 and the DAS unit 13.
Switches connections or relationships between E1 to DE8 and DAS elements DAS1 to DAS8. In FIG. 5, for example,
Detection elements DE3 and D included in the detection segment DE34
E4 is a DAS element DAS4 by the analog switch 50.
Connected to. Similarly, for example, the detection segment DE5
The detection elements DE5 and DE6 included in 6 are connected to the DAS element DAS5 by the analog switch 50. DAS
The element DAS4 collects the data detected by the detection elements DE3 and DE4, and supplies the collected data to the reconstruction unit 15 for the image reconstruction processing via the memory 14. Similarly, the DAS element DAS5 collects the data detected by the detection elements DE5 and DE6, and supplies the collected data to the reconstruction unit 15 for the image reconstruction processing via the memory 14. The other DAS elements DAS1 to DAS3 and DAS elements DAS6 to DAS8 are data (X-ray tube 1
Data that is not based on X-ray irradiation (regardless of the true shadow of X-ray irradiation) may be supplied or may not be supplied. Even when supplied, the supply data may not be supplied to the reconstruction unit 15.

When the prescan is started by the X-ray detector 2, the analog switch 50, and the DAS section 13 under the above conditions, the operator starts observing the tomographic image displayed on the image display device 22. In this observation, the operator looks closely at the preset ROI. FIG. 6 is a diagram showing a display example of a tomographic image according to the embodiment of the present invention. Immediately after starting the prescan, the image display device 22 displays the tomographic image 60. In the tomographic image 60, the ROI 62 including the carotid artery 63 is set as shown on the left side of FIG. Tomographic image 6
Since 0 is in the early stage of prescan, the contrast medium injected into the subject P has not yet reached the carotid artery 63 at the slice position of prescan. Therefore, the contrast agent has not yet appeared in the carotid artery 63 of the displayed tomographic image 60. With respect to such an initial state, the tomographic image 61 is displayed on the image display device 22 after a predetermined time has elapsed from the initial state. As a result of the lapse of a predetermined time, the contrast medium injected into the subject P reaches the carotid artery 63 at the pre-scan slice position. Therefore,
The contrast agent can be confirmed in the carotid artery 63 displayed in the tomographic image 61. On the image display device 22, all the tomographic images during the pre-scan are continuously displayed in a form such as a cine mode display like a moving image.

When the tomographic image as shown in FIG. 6 is displayed, a graph showing the CT value may be displayed together with the tomographic image. Alternatively, the tomographic image and the graph may be switched so that they are independently displayed.

7 to 9 are views showing an example of transition of the contrast agent at the prescan position according to the embodiment of the present invention. As described above, the contrast agent does not appear in the carotid artery at the slice position of the prescan in the initial stage of the prescan. After that, the contrast agent gradually starts to reach the pre-scan slice position as time passes. As one mode in such a stage, it can be recognized in the graph showing the transition of the CT value in the ROI of the tomographic image at the slice position of the pre-scan as shown in FIG. 7. Since the prescan is started shortly after the injection of the contrast agent, the CT value obtained based on the tomographic image of the prescan starts to slowly rise (see FIG. 7). After that, the CT value further rises and reaches a predetermined reference value as shown in FIG. At this time, the tomographic image displayed on the image display device 22 becomes like the tomographic image 61 already shown in FIG. Providing a predetermined reference value for the CT value is useful when the prescan is set to be automatically terminated. Further, even when the automatic end is not set, setting a predetermined reference value for the CT value can help the operator in determining when to end the prescan. This predetermined reference value can be set to an appropriate value based on the operator's judgment or the like, such as setting it to a peak level. If the prescan continues at the slice position of the prescan, the CT value will follow the transition as shown in FIG. After the CT value reaches the peak, as the contrast agent passes through the pre-scan slice position and exits, it drops to the initial CT value (before the contrast agent penetrates).

According to the end of the prescan, the bed 2 or the set of the X-ray tube 1 and the X-ray detector 2 is moved to the start position of the main scan. When the scan position is changed, the slice width of the X-ray detector 2 is also switched to a wide one as shown in FIG.

FIG. 10 is a diagram showing an example of changing the X-ray irradiation width in the X-ray detector 2 according to the embodiment of the present invention. As shown in FIGS. 4 and 5, the pre-scan is performed with a first slice width narrower than that of the main scan, for example, with the first slice width corresponding to the width of four detection elements. The collimator 70 collimates the X-rays emitted from the X-ray tube 1, whereby the collimated X-rays are emitted to a width corresponding to the first slice width on the X-ray detector 2. Further, the slice thickness corresponds to the width of the two detection elements. This can be seen on the left side of FIG. On the other hand, the main scan will be recognized on the right side of the figure. Compared with the pre-scan, in the main scan, as described in the pattern (iii) of FIG. 4, the second slice width corresponding to eight detection elements is set. The collimator 70 collimates the X-ray emitted from the X-ray tube 1 with an opening wider than that in the prescan,
As a result, the collimated X-rays are emitted to a width corresponding to the second slice width on the X-ray detector 2. Further, the slice thickness corresponds to the width of one detection element.

Regarding the prescan, the X-ray detector 2 and D
An example of the connection between the AS units 13 has been described with reference to FIG. Similarly, here, regarding the main scan, an example of connection between the X-ray detector 2 and the DAS unit 13 will be described with reference to FIG. 11.
FIG. 11 is a block diagram showing a configuration relating to X-ray detection and data acquisition in the main scan according to the embodiment of the present invention.

The X-ray detector 2 has detection elements DE1 to DE8 similar to the case of FIG. However,
Here, each detector element is used for each slice, ie as one detector segment. The main scan is performed by an eight-slice scan. At this time, X-ray tube 1
Then, the transmitted X-rays transmitted through the subject P by the irradiated X-rays are eight detection elements (detection segments) DE1 to DE8.
X-ray irradiation is performed so as to irradiate the subject. Therefore, for example, the detection elements DE1 to DE8 correspond to the first slice to the eighth slice. In other words, regarding the first slice in the main scan, the first transmitted X-ray transmitted through the first portion of the subject P is detected by the detection element DE1, and similarly, regarding the second slice, Sample P
The second transmitted X-ray transmitted through the second portion of the
Detected in 2. Further, the detection elements DE3 to DE
The same can be applied to E8.

The X-ray data detected by the detection elements DE1 to DE8 is given to the DAS section 13 via the analog switch 50. The analog switch 50 is provided between the X-ray detector 2 and the DAS unit 13, and switches the connection or relationship between the detection elements DE1 to DE8 and the DAS elements DAS1 to DAS8. When switching from the prescan to the main scan, the analog switch 50 needs to switch the connection made for the prescan to the connection for the main scan. This is because in the prescan, for example, the detection elements DE3 and DE4 are bundled,
The output data was supplied to the DAS element DAS4. In FIG. 10, instead of this, the detection elements DE1 to D
E8 is connected to the DAS elements DAS1 to DAS8 by the analog switch 50, respectively. DAS element DAS
1 collects the data detected by the detector element DE1,
The collected data is supplied to the reconstruction unit 15 via the memory 14 for image reconstruction processing. Similarly, DAS element D
AS2 to DAS8 are detection elements DE2 to DE, respectively.
Data detected by the reconstructing unit 1 for image reconstruction processing via the memory 14
Supply to 5.

Under the above conditions, the main scan is started when a predetermined delay time has elapsed after the end of the prescan. However, the analog switch 50 is switched, which causes the detection elements DE1 to DE8 and DAS.
When the connection status between the elements DAS1 to DAS8 has changed, it is required to perform offset correction in order to prevent undesired noise from appearing in the tomographic image due to the effect of this connection change. For offset correction,
It is necessary to detect data by the X-ray detector 2 without performing X-ray irradiation by the X-ray tube 1. The data detected by the X-ray detector 2 is collected by the DAS unit 13, and offset correction is performed based on the data collected by the DAS unit 13. Note that this offset correction is not very effective even if it is performed before the prescan. This is because even if the bundling between the detection elements (connection between the detection elements and the DAS elements) is performed in the same manner, variations in offset will occur over time. Therefore, it is effective to perform it just before the main scan, and it is preferable to actually start the main scan after the offset correction is completed.

In the above-described embodiment of the present invention, even if the offset correction is performed in this way, the pre-scan itself is performed with a slice width narrower than that of the main scan, so that the X-ray exposure of the subject P is prevented. It is possible to reduce the amount.

By the way, in the case of performing the offset correction, the time required for the correction is not so long.
In fact, offset correction may take as little as 0.5 seconds, for example. However, ideally, it is desired to perform only the main scan originally required for the inspection, and therefore, an extra inspection time is required, and it is not necessary to perform the pre-scan for giving the patient P an extra exposure. Not very desirable as an inspection. From this point, even the above-mentioned slight time for offset correction is not very preferable. Therefore, a case where the time between the prescan and the main scan is reduced will be described with reference to FIGS. 12 and 13.

FIG. 12 is a diagram showing another modification of the X-ray irradiation width in the X-ray detector 2 according to the embodiment of the present invention. As shown in the figure, the pre-scan is performed with a first irradiation width composed of four detection segments. This first
The irradiation width of is the same as the first slice width at the time of prescan shown in FIG. Each detection segment has a slice thickness corresponding to the width of one detection element. The X-rays emitted from the X-ray tube 1 are collimated by the collimator 70, whereby the collimated X-rays are detected by the X-ray detector 2
Irradiation is performed in a width corresponding to the first irradiation width above. This can be seen on the left side of FIG. On the other hand, in the main scan, the irradiation width (second irradiation width) and slice thickness are the same as the second slice width and slice thickness described in FIG. This can be seen on the right side of FIG.

FIG. 13 is a block diagram showing another configuration relating to X-ray detection and data acquisition in prescan according to the embodiment of the present invention.

The X-ray detector 2 has detection elements DE1 to DE8 similar to the case of FIGS. 5 and 11. Here, each detection element is used for each slice, that is, as one detection segment, as in FIG. 11 described for the main scan instead of FIG. 5 described for the pre-scan. The pre-scan is performed by an 8-slice scan. At this time, in the X-ray tube 1, the irradiated X-rays are collimated by the collimator 70 at the same opening as in the case of FIG.
Only one sensing element (sensing segment), eg DE3
X-ray irradiation is performed so as to irradiate through DE6. Therefore, for example, the detection elements DE1 to DE8 correspond to the first slice to the eighth slice. However, since the detection elements DE1, DE2, DE7, and DE8 are not substantially irradiated with X-ray irradiation (there is no shadow), they do not substantially have a significant meaning. The first part that has passed through the first part of the subject P in the pre-scan
The transmitted X-rays are detected by the detection element DE3, and similarly, the second transmitted X-rays transmitted through the second portion of the subject P are detected by the detection element DE4. Further, the same can be applied to the detection elements DE5 and DE6.

The X-ray data detected by the detection elements DE1 to DE8 is given to the DAS section 13 via the analog switch 50. The analog switch 50 is provided between the X-ray detector 2 and the DAS unit 13, and switches the connection or relationship between the detection elements DE1 to DE8 and the DAS elements DAS1 to DAS8. Here, the detection elements DE1 to DE
E8 is connected to the DAS elements DAS1 to DAS8 by the analog switch 50, respectively. DAS element DAS
1 collects data from the detection element DE1 and supplies the collected data to the reconstruction unit 15 via the memory 14. Similarly, the DAS elements DAS2 to DAS8 collect data from the detection elements DE2 to DE8, respectively, and supply the collected data to the reconstruction unit 15 via the memory 14.
In the reconstruction unit 15, DAS elements DAS1, DAS2, DA
The data supplied from S7 and DAS8 are not used in the image reconstruction processing. These DAS elements DAS1, D
AS2, DAS7, DAS8 were not irradiated with X-rays (ie, were not the target of umbra) DE1, DE
This is because data is collected from 2, DE7 and DE8. The reconstruction unit 15 reconstructs a tomographic image using the data supplied from the DAS elements DAS3 to DAS6.

Separately from this, the DAS element DAS1
Even if the data is collected from the detection element DE1, the collected data may not be finally supplied to the reconstruction unit 15. Similarly, DAS elements DAS2, DAS7, DAS
8 also collects data from the detection elements DE2, DE7, and DE8, respectively, the collected data is finally reconstructed by the reconstruction unit 15
May not be supplied to As a result, the reconfiguring unit 15 causes the DAS unit 13 (the DAS elements DAS3 to DAS
A tomographic image is reconstructed based on the data supplied from S6).

The above pre-scan conditions represent that the X-ray detector 2 is irradiated with X-rays at the first irradiation width, while the pre-scan slice width corresponds to eight detection elements. There is.

When the image reconstruction processing is performed, the images are bundled by the time the images are displayed on the image display device 22. In this image bundle, the first image data reconstructed based on the data supplied from the DAS element DAS3 and the second image data reconstructed based on the data supplied from the DAS element DAS4 are combined. It is bundled as the first tomographic image data. Similarly, the third image data reconstructed based on the data supplied from the DAS element DAS5 and the DAS element DA
The fourth image data reconstructed based on the data supplied from S6 is bundled as the second tomographic image data. Thereby, the tomographic images based on the first and second tomographic image data are displayed on the image display device 22, respectively. The displayed tomographic image may have an image quality similar to that of the tomographic image displayed based on the data detection and data collection in the case of FIG.

According to the embodiment of the present invention, the data bundling is not limited to the above method. As another example of bundling data, bundling with raw data can be considered. This is the DAS element DAS1, DAS2, D described above.
Regardless of whether the data collected in AS7 or DAS8 is supplied to the reconstruction unit 15 and is not used in the image reconstruction processing, or the collected data is not even supplied to the reconstruction unit 15. , Is applicable. According to this raw data method, DAS
The data collected by the elements DAS3 and DAS4 are bundled as one data (first raw data) before the image reconstruction processing is performed in the reconstruction unit 15. Similarly, the data respectively collected in the DAS elements DAS5 and DAS6 are bundled as one data (second raw data) before the image reconstruction processing is performed in the reconstruction unit 15. As a result, the reconstruction unit 15 makes the first raw data and the second raw data respectively based on the first raw data.
And the second tomographic image are reconstructed. The reconstructed tomographic image is displayed as a tomographic image on the image display device 22. According to such a method of bundling the raw data, since the data bundling is performed using the raw data before the image reconstruction processing, the displayed tomographic image is a tomographic image displayed based on the bundling by the image data described above. It is possible to have an image quality equal to or even better than that of the image.

When the pre-scan is performed under the above conditions, the main scan is then performed. Figure 1
As shown in FIG. 3, the slice width and the slice thickness in the prescan are the same as those shown in FIG. That is, the analog switch 50 does not need to switch the connection between the detection elements DE1 to DE8 and the DAS elements DAS1 to DAS8. Therefore, the main scan can be started if a predetermined delay time elapses after the end of the prescan without performing the offset correction.

Next, the operation of the X-ray CT apparatus having the above-mentioned structure will be described with reference to FIG. FIG. 14 is a flowchart showing an example of the inspection procedure of the X-ray CT apparatus according to the embodiment of the present invention.

In FIG. 14, an examination using a contrast agent will be described as an example of the examination procedure of the X-ray CT apparatus. First, a contrast agent is injected into the subject P in order to emphasize a specific portion of the subject P in the tomographic image obtained by the X-ray CT apparatus (step S1). Immediately after the injection of the contrast agent in step S1, the pre-scanning is started so that the X-ray is irradiated to the portion of the first width of the X-ray detector 2 (for example, four detection elements in the body axis direction). (Step S
2).

The prescan is carried out while being fixed to the first position of the subject P. At that time, the same pre-scan is performed with weaker X-rays (lower X-ray intensity) than the main scan that follows. Further, the first position is a position close to the second position which is the start position of the main scan. During the prescan, the obtained tomographic image is continuously displayed on the image display device 22 in substantially real time. Further, a graph showing the CT value is also displayed on the image display device 22. The displayed CT value corresponds to the tomographic image displayed together. Under such an environment, the operator observes (monitors) the tomographic image and the CT value. During the observation, it is determined whether or not the CT value reaches or exceeds a predetermined reference value at a certain time point (step S3). The prescan does not end until the CT value reaches a predetermined reference value or exceeds the same reference value. At a certain point in time, when the CT value for a certain tomographic image reaches or exceeds a predetermined reference value, the prescan ends (step S
4). The end of the prescan may be automatically controlled by the system control unit 10 or may be performed by the operator operating (pressing) the button switch 11.

Upon completion of the prescan, the scan position is changed to the second position (step S5). When starting the main scan, it is determined whether or not the analog switch 50 needs to be switched (step S6). If the connection between the detection element and the DAS element is the same in the prescan and the main scan, that is, if the predetermined slice width and the predetermined slice thickness are common between the prescan and the main scan. In this case, the analog switch 50 does not need to switch its connection mode. However,
If either the slice width or slice thickness differs between the pre-scan and the main scan, the analog switch 5
0 switches the connection between the detection element and the DAS element (step S7). Analog switch 5 in step S7
When 0 is switched, offset correction is continuously performed without X-ray irradiation by the X-ray tube 1 (step S8).

When the offset correction is completed, or when the analog switch 50 is not switched, X
The line CT apparatus starts execution of the main scan (step S
9). This main scan is started at the second position with the X-ray intensity required for the imaging. This X-ray intensity may be higher than the X-ray intensity in the prescan. The main scan may be performed in a helical (or spiral) shape. It is assumed that the X-ray tube 1 and the X-ray detector 2 continue to rotate around the subject P from the beginning of the prescan to the end of the main scan. When the main scan is completed for a predetermined scan range of the subject P, the main scan ends.

Although the flow chart shown in FIG. 14 has been described above, the procedure flow of the X-ray CT apparatus according to the present invention is not limited to the above description of FIG. Any of the explanations given above with reference to FIG. 1 to FIG. 13 as an example according to the embodiment of the present invention can be applied in a suitable form to the process in which it can be applied.

Further, the pre-scan has been described for the case of the two-slice scan and the four-slice scan, but in the present invention, slices of any number including the single-slice scan can be used if it seems appropriate depending on the inspection situation (condition). Even the scan can be applied to the pre-scan. Needless to say, the main scan is not limited to the one described in the present embodiment.

Furthermore, the X-ray CT apparatus of the present invention is, in the above-mentioned embodiment, a recording medium capable of receiving and storing a computer program or application as a computer-readable instruction in a temporary or non-volatile manner (eg, a recording medium). RAM: RANDOM
ACCESS MEMORY). The X-ray CT apparatus further includes a hard disk drive for writing to and reading from a hard disk (as part of a control unit), a magnetic disk drive for writing to and reading from a magnetic disk, and / or an optical disk (CD, CD). -R, CD-RW, DVD, other optical devices) and an optical disk drive for writing and reading. These memories and drives,
Those of ordinary skill in the art will also appreciate that one or more of these respective media are merely examples of computer program products having computer readable instructions that, when executed, enable at least one of the embodiments of the invention. This is understandable.

As a result, even in the case of the X-ray CT apparatus which does not have the function or feature according to the embodiment of the present invention, the computer readable program can be read and executed, and the multi-slice scan or the real-time scan can be performed. As long as it is an X-ray CT device having a scanning function,
The features of the embodiment of the present invention can be enjoyed.

The embodiment of the present invention described above is merely an example described only for facilitating the understanding of the present invention, and is not a description for limiting the present invention. Therefore, the constituent elements and other elements disclosed in the above-described embodiments of the present invention can be designed and modified to their equivalents or the like without departing from the gist of the present invention. Further, any possible combinations of the same constituent elements and other elements are included in the scope of the present invention as long as the same effects as the effects obtained in the embodiments of the present invention described above can be obtained.

[0071]

According to the present invention, an X-ray C using a contrast agent is used.
Contrast images can be obtained at appropriate timing in the T examination, and the examination time can be shortened and the exposure dose of the subject can be reduced as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a system control unit according to the embodiment of the present invention.

FIG. 3 is a diagram showing an example of a pre-scan position and a main scan position according to the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a data collection pattern according to the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration related to X-ray detection and data acquisition in prescan according to the embodiment of the present invention.

FIG. 6 is a diagram showing a display example of a tomographic image according to an embodiment of the present invention.

FIG. 7 is a diagram showing a first transition example of the contrast agent at the prescan position according to the embodiment of the present invention.

FIG. 8 is a diagram showing a second transition example of the contrast agent at the prescan position according to the embodiment of the present invention.

FIG. 9 is a diagram showing a third transition example of the contrast agent at the prescan position according to the embodiment of the present invention.

FIG. 10 is a diagram showing an example of changing the X-ray irradiation width in the X-ray detector according to the embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration relating to X-ray detection and data collection in a main scan according to the embodiment of the present invention.

FIG. 12 is a diagram showing another example of changing the X-ray irradiation width in the X-ray detector according to the embodiment of the present invention.

FIG. 13 is a block diagram showing another configuration relating to X-ray detection and data acquisition in prescan according to the embodiment of the present invention.

FIG. 14 is a flowchart showing an example of an inspection procedure of the X-ray CT apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 ... X-ray tube 2 ... X-ray detector 3 ... Rotation mechanism 4 ... Sleeper 5 ... Rotation control unit 6 ... X-ray control unit 7: Sleeper control unit 8 ... Detector control unit 9 ... Scan control unit 10 ... System control unit 11 ... Button switch 12 ... Operation panel 13 ... Data collection unit 14 ... Memory 15 ... Reconstruction Department 16, 20 ... Image memory 17 ... ROI setting section 18 ... CT value calculator 19: Graph creation section 21 ... Adder 22 ... Image display device 31 ... Prescan control unit 32 ... Main scan control unit 33 ... Integrated control unit 50 ... Analog switch 70 ... Collimator

Claims (35)

[Claims] 1. X-ray generation means for generating a first X-ray in a pre-scan mode and a second X-ray in a main scan mode; and an X-ray generator generated at a first scan position in the pre-scan mode. The first transmitted X-rays that are emitted in a first irradiation width along the body axis of the subject by the transmission of the first X-rays through the subject are detected and The second X-ray generated at the scan position is transmitted through the subject to be radiated to a second irradiation width along the body axis of the subject, which is wider than the first irradiation width. X-ray detection means for detecting a second transmitted X-ray, control means for controlling the first and second scan positions, a first image is displayed based on the first transmitted X-ray, and Table displaying the second image based on the second transmitted X-ray An X-ray CT apparatus comprising: an indicating unit. 2. The control means further comprises a collimating means which is provided between the X-ray generating means and the X-ray detecting means and which collimates the first X-ray and the second X-ray. The collimating means is controlled so that the first transmitted X-rays and the second transmitted X-rays are emitted to the first irradiation width and the second irradiation width of the X-ray detection means, respectively. The X-ray CT apparatus according to claim 1, wherein the collimating width is changed. 3. The control means irradiates the first transmitted X-ray and the second transmitted X-ray to the first irradiation width and the second irradiation width of the X-ray detection means, respectively. The X-ray C according to claim 1, wherein the X-ray generation means is controlled to change the generation angle in the body axis direction.
T device. 4. When the distance between the X-ray generation means and the X-ray detection means is variable, and when this distance is a first distance, the first transmitted X-ray is the X-ray detection means. When the distance is a second distance that is longer than the first distance, the second transmitted X-ray is X
The X-ray CT apparatus according to claim 1, wherein the X-ray CT is irradiated to the second irradiation width of the line detection means. 5. The X-ray CT apparatus according to claim 1, wherein the first X-ray is weaker than the second X-ray. 6. The X-ray CT apparatus according to claim 1, wherein the number of slices per single scan in the prescan mode is smaller than the number of slices per single scan in the main scan mode. 7. The X-ray detection means has a plurality of detection elements in the body axis direction, and each scan slice in the pre-scan mode has at least two of the plurality of detection elements.
The X-ray CT apparatus according to claim 1, wherein one of them is used. 8. The X-ray detection means has a plurality of detection elements in the body axis direction, and the first irradiation width has a first number of detection elements in the body axis direction among the plurality of detection elements. The second irradiation width is higher than the first number in the body axis direction of the plurality of detection elements.
The X-ray CT apparatus according to claim 1, wherein the X-ray CT apparatus is located on the number of the detection elements. 9. A device comprising a plurality of data collecting elements, said X
Data collection means for collecting output data from the line detection means, further comprising a switch for switching the connection between the plurality of detection elements and the plurality of data collection elements, the connection is the pre-scan mode and the book 9. The same is maintained in the scan mode.
The X-ray CT apparatus described in 1. 10. A data collecting means comprising a plurality of data collecting elements for collecting output data from said X-ray detecting means, wherein a predetermined number of said data collecting elements are said data collecting elements. The X-ray CT apparatus according to claim 1, wherein the X-ray CT apparatus is commonly used in both the pre-scan mode and the main scan mode. 11. Reconstruction means for reconstructing an image based on at least a portion of the data collected by said data collection means, further comprising: remnants of the data collected by said data collection means in prescan mode. 11. The X-ray CT apparatus according to claim 10, wherein the portion is not used in the reconstruction processing by the reconstruction means. 12. The X-ray CT apparatus according to claim 1, wherein the first scan position is fixed in the body axis direction. 13. The X-ray CT apparatus according to claim 1, wherein the second scan position is movable in the body axis direction. 14. The second scan position is obtained by moving at least the X-ray generation means and the X-ray detection means from the first scan position in a body axis direction in response to a manual instruction from an operator. Claim 1 characterized by the above.
The X-ray CT apparatus described in 1. 15. The second scan position is the first scan position.
Is obtained by moving at least the X-ray generation means and the X-ray detection means in the body axis direction from the first scan position in response to the CT value of the image of FIG. X-ray C according to claim 1.
T device. 16. The CT calculated by the calculating means, further comprising a calculating means for calculating a CT value in a predetermined region of the first image, wherein the subject is injected with a contrast agent.
The X-ray CT apparatus according to claim 1, wherein when the value reaches a predetermined reference value, the scan in the prescan mode is automatically ended. 17. The control unit switches the scan position from the first scan position to the second scan position in response to the end of the scan in the prescan mode, and the scan in the main scan mode is performed in the prescan mode. 17. The X-ray CT apparatus according to claim 16, wherein the X-ray CT is started at the second scan position after a lapse of a predetermined time after the scan in. 18. The X-ray CT apparatus according to claim 1, wherein the display unit displays a CT value in a predetermined region of the first image in a prescan mode. 19. The X-ray detection means has a plurality of detection elements in the body axis direction, and in the pre-scan mode, one detection element among the plurality of detection elements within the first irradiation width is used. The first data based on detection is bundled with second data based on detection by at least one other detection element within the first irradiation width of the plurality of detection elements. X-ray CT described in
apparatus. 20. Reconstructing means for reconstructing an image based on third data obtained as a result of bundling the first data and the second data, further comprising: 20. The X-ray CT apparatus according to claim 19, wherein bundling is performed before the first data and the second data are supplied to the reconstruction unit. 21. A data collecting means comprising a plurality of data collecting elements for collecting output data from the X-ray detecting means, wherein the X-ray detecting means has a plurality of detecting elements in the body axis direction. However, at least one detection element used among the plurality of detection elements, slice thickness used in a single slice, and at least one data acquisition element used among the plurality of data acquisition elements are in a pre-scan mode and a main scan. The X-ray CT apparatus according to claim 1, wherein the X-ray CT apparatus is common between modes. 22. The number of slices per single scan in the pre-scan mode differs from the number of slices per single scan in the main scan mode by the difference between the first irradiation width and the second irradiation width. The X-ray CT according to claim 1, wherein the number is reduced by the corresponding amount.
apparatus. 23. The X-ray detection means has a plurality of detection elements in the body axis direction, and the number of detection elements used in the pre-scan mode among the plurality of detection elements is the same as that of the plurality of detection elements. The number of detection elements used in the main scan mode is smaller than the number of detection elements used in the main scan mode by an amount corresponding to a difference between the first irradiation width and the second irradiation width. X-ray CT system. 24. A data collecting means comprising a plurality of data collecting elements for collecting output data from the X-ray detecting means, wherein the X-ray detecting means has a plurality of detecting elements in the body axis direction. 2. The X-ray CT apparatus according to claim 1, wherein each of the plurality of data acquisition elements collects output data from one or more detection elements of the plurality of detection elements. 25. A data collecting means comprising a plurality of data collecting elements for collecting output data from the X-ray detecting means, and a reconstruction for reconstructing an image based on the output data collected by the data collecting means. The X-ray detection means has a plurality of detection elements in the body axis direction, and does not correspond to a detection element within the first irradiation width of the plurality of detection elements, 2. The information from one or more data collecting elements among the data collecting elements according to claim 1, which is not used as output data for image reconstruction processing by the reconstructing means in the prescan mode. X-ray CT system. 26. The apparatus further comprises input means for inputting information relating to determination of main scan conditions for the main scan mode, wherein the control means determines the main scan conditions based on the information, The X-ray CT apparatus according to claim 1, wherein a prescan condition for the prescan mode is automatically determined based on the determined main scan condition. 27. When a plurality of predetermined pre-scan conditions are prepared for the main scan condition and each of the predetermined pre-scan conditions corresponds to each of a plurality of parts of a subject, the control means determines the determination. 3. One of the plurality of predetermined pre-scan conditions corresponding to one of the plurality of regions indicated in the specified main scan condition is determined as the determined pre-scan condition.
The X-ray CT apparatus according to item 6. 28. Reconstructing means for reconstructing an image based on the detection result by the X-ray detecting means is further provided, and in the prescan mode, the reconstructing means performs a reconstruction process by a real-time reconstruction method. The X-ray CT apparatus according to claim 1, which is characterized in that. 29. An X-ray source for irradiating X-rays while rotating around a subject, and a collimator width for determining an X-ray irradiation width to the subject can be changed in a body axis direction of the subject. And a multi-row detector in which a plurality of detection elements for detecting X-rays transmitted through the subject are arranged in the body axis direction, and a data collection element for collecting output data of the detection elements is in the body axis direction. A plurality of data acquisition devices arranged in parallel, execution means for executing a scan of the subject using the X-ray source and the X-ray detector, and a prescan for monitoring a CT value of a region of interest of the subject A control unit that shifts to a main scan for scanning the imaging region of the subject and controls the collimator so that the collimator width during the pre-scan is made narrower than the collimator width during the main scan. Reconstructing means for reconstructing a tomographic image of the subject based on the projection data collected by rescan, and for reconstructing an image of the subject based on the projection data collected by the main scan. An X-ray CT apparatus characterized in that 30. A switch for switching the number of elements of the data collecting element in the body axis direction used for the data collection is further provided, and the control means sets the number of elements of the data collecting element in the pre-scan and the main scan. 30. The X-ray CT apparatus according to claim 29, which is common. 31. A setting means for setting a slice width defined by the number of slices or the number of slices × slice thickness; and a detector provided between the multi-row detector and the data acquisition device. A switch for switching the connection mode of the data acquisition element is further provided, and the control unit sets the number of slices or the slice width different between the pre-scan and the main scan by the setting unit. 30. The X-ray CT apparatus according to claim 29, wherein the connection mode is not changed between the prescan and the main scan. 32. The control means converts the output data output from the detection elements not used for the pre-scanning to the data acquisition element according to the number of slices or the slice width set by the setting means into the image reconstruction. 32. The X-ray CT apparatus according to claim 31, which is not used. 33. The control means sets the slice thickness and the use condition of the data acquisition element to be the same and makes the number of used rows of the detection element different between the pre-scan and the main scan. 30. The X-ray CT apparatus according to claim 29. 34. The first X in the prescan mode
A first line along the body axis of the subject of the X-ray detector by generating a ray and transmitting the subject by the first X-ray generated at the first scan position in the pre-scan mode. Detecting the first transmitted X-rays irradiated in the irradiation width of, and displaying a first image based on the first transmitted X-rays, generating a second X-ray in the main scan mode, The first irradiation width along the body axis of the subject of the X-ray detector when the second X-ray generated at the second scan position in the scan mode passes through the subject. Second irradiation with a wider second irradiation width
Of the transmitted X-rays, a second image is displayed based on the second transmitted X-rays, and the first and second scan positions are controlled. . 35. The X-ray CT apparatus can be mounted, and the X-ray CT apparatus is executed when a scan is performed.
A software recording medium in which software for controlling a linear CT device is recorded, wherein a first X-ray is generated in a prescan mode, and the first X-ray generated at a first scan position in the prescan mode. The X-ray detector detects a first transmitted X-ray radiated in a first irradiation width along the body axis of the subject by transmitting the X-ray detector to the first transmitted X-ray. A first image is displayed based on the first image, a second X-ray is generated in the main scan mode, and the second X-ray generated at the second scan position in the main scan mode passes through the subject. By doing so, the second irradiation width along the body axis of the subject of the X-ray detector, which is wider than the first irradiation width, is irradiated.
Software for detecting the transmitted X-rays, displaying a second image based on the second transmitted X-rays, and controlling the first and second scan positions. recoding media.