JP2005013768A - X-ray CT system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly improve inspection efficiency as compared with a single-tube X-ray CT apparatus.
In an X-ray CT apparatus for reconstructing a CT image of a subject based on projection data obtained by scanning the subject, a first X-ray source for exposing X-rays and the subject are provided. A first imaging system having a first detector for detecting transmitted X-rays; a second X-ray source for exposing X-rays; and a first X-ray for detecting X-rays transmitted through the subject. A second imaging system having two detectors, energy of X-rays emitted from the first X-ray tube of the first imaging system, and irradiation from a second X-ray tube of the second imaging system And control means for scanning the same position of the subject with different X-ray energy.
[Selection] Figure 1

Description

The present invention relates to an X-ray CT apparatus having a plurality of X-ray sources and an X-ray detector corresponding to each X-ray source.

In recent years, with the development of medical diagnostic apparatuses, CT apparatuses that take tomographic images of any part of a subject have come to be used. Also, in recent years, in order to shorten tomographic imaging, a helical scan that scans the periphery of the subject in a spiral, calculates the data of each slice position by interpolation processing, and reconstructs the slice image based on this The method is in practical use.

In the conventional helical scan CT apparatus, as shown in FIGS. 9A, 9B, and 9C, a single tube 71 moves along a trajectory 76 around a patient (subject) 70 on a bed 75 that can move in the body axis direction. In this way, the beam 72 is rotated in a spiral manner.

However, in the conventional helical scan CT apparatus,
(1) Since there is one tube, it is not possible to scan a plurality of locations at a certain time.
(2) Only one scanning condition can be scanned at a time.
(3) When the heat capacity of the optical system is full, you must wait until it cools down. Also, it takes time to replace the substitute optical system when it fails.
(4) Although it is necessary to scan in a short time before the contrast agent is left, scanning is not possible in a short time because there is only one tube.
(5) Since there is only one tube, it is not possible to scan a wide range in a certain time.
There was an inconvenience.

The present invention has been made in view of the above inconveniences, and an object of the present invention is to improve inspection efficiency over a single-tube X-ray CT apparatus.

In order to achieve the above object, the present invention provides a first X-ray that exposes X-rays in an X-ray CT apparatus that reconstructs a CT image of the subject based on projection data obtained by scanning the subject. A first imaging system having a radiation source and a first detector for detecting X-rays transmitted through the subject;
A second imaging system having a second X-ray source for exposing X-rays and a second detector for detecting X-rays transmitted through the subject; and a first of the first imaging system Control means for scanning the same position of the subject by making the X-ray energy irradiated from the X-ray tube different from the X-ray energy irradiated from the second X-ray tube of the second imaging system; It is characterized by comprising.

According to the present invention, by imaging the same part with two or more types of X-ray energy,
Since an image for each energy can be obtained, the inspection efficiency can be improved as compared with a single-tube CT apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to the present invention.

The X-ray CT apparatus shown in the drawing includes three tubes (X-ray tubes) 3-1, 3-2, and 3-3 that can be rotated independently or in conjunction with each other at intervals parallel to each other. Corresponding three sets of detectors 4-1, 4-2, 4-3, and three sets of data for collecting projection data detected by each detector and making it easy to process Collection units 5-1, 5-2, 5-3,
Rotation control unit 7 for controlling the rotation of tube 3-1, 3-2, 3-3 and detector 4-1, 4-2, 4-3 and tube 3-1, 3-2, 3-3 And an optical system position control unit 8 for controlling the distance between the two (a broken line portion) 2.

The X-ray CT apparatus further includes an X-ray control unit 6 that controls the X-ray dose irradiated by the tubes 3-1, 3-2, and 3-3, a bed driving unit 10 that drives the bed 11, and a bed driving unit 10. A controller 9 for controlling the CPU, a central control unit (CPU) 12, a monitor 13 connected to the central control unit 6 via a bus (not shown), a keyboard 14 as a scanning condition input device, an internal memory 15, and collected data And a magnetic disk 16 for storing image data.

The central control unit 12 controls the X-ray control unit 6, the rotation control unit 7, the optical system position control unit 8, the controller 9, and an image reconstruction device (not shown), and controls the entire X-ray CT apparatus of this embodiment. It governs the operation. The X-ray control unit 6 controls X-rays for each X-ray tube (tube) under the control of the central control unit 12. Then, an X-ray tube (for example, the X-ray dose exposed by the tube 3-1 and other X-rays)
The amount of X-rays exposed by the tube (for example, the tube 3-2) can be made different.

The rotation control unit 7 controls the rotation of each X-ray tube and / or detector under the control of the central control unit 12, and the set of X-ray tubes and detectors is set by the rotation control unit 7 to other X-ray tubes and detectors. It can be rotated independently of the set of detectors. The optical system position control unit 8 controls the movement of each X-ray tube and detector in the bed direction (the body axis direction of the patient (subject)) under the control of the central control unit 12. Specifically, an X-ray tube (tube) is set at the scanning start position, and the X-ray tube 3
1 and 3-2 and 3-3, which X-ray tube is moved in the direction of the bed (positive direction or negative direction) and how much speed is controlled. The controller 9 drives the bed driving unit 10 under the control of the central control unit 12 to move the bed 1 in the body axis direction of the patient.

FIG. 2 is a block diagram showing the configuration of each control unit shown in FIG. 1, and the central control unit 12 refers to the scanning condition list 17 shown in FIG. 1 and determines the X-ray control unit for each tube based on the scanning conditions. 6, a command (signal) is sent to the rotation control unit 7, the optical system position control unit 8, and the controller 9, and the control units 6, 7, 8, 9 are controlled and the control units 6, 7, 8 are controlled. 9 and detector 4-1.
4-2, 4-3 (for example, the rotation angle, the position (interval) of the optical system, the position of the bed, the X-ray transmission amount from each detector, etc.) 7, 8, and 9 are feedback-controlled. Based on the feedback control, the control units 6, 7, 8, and 9 perform the X-ray generation amount of each X-ray source, the rotation and movement of the tube and the detector, and the movement control of the bed. The rotation and movement of the tube and the detector have a rotation drive device (not shown) and a movement device (not shown) for each set of detectors corresponding to each tube, and the rotation control 7 and the optical system. Driven independently or in conjunction with each other based on a drive signal from the control unit 8.

The scanning condition list 17 is normally stored in the magnetic disk 16, and when the X-ray CT apparatus 1 is activated, the scanning condition list 17 is read from the magnetic disk 16 into the internal memory 15 and referenced by the central control unit 12. The 17 conditions can be changed, added / registered, and deleted from the keyboard 14. In this case, since the scanning condition list 17 is displayed on the monitor 13 in the form shown in FIG. 2, the operator can easily input the scanning conditions. The scanning condition list 17 stores scanning conditions for each tube, and a unique number is assigned to the tube in advance, and this number cannot be changed. Reference numeral 17 in FIG. 2 shows an example of the scanning condition list. The first line shows a state graph of the first tube 3-1 (for example, this tube is used ... 1; not used ... 2 ; Value indicating tube state such as failure ... 3), X-ray conditions (X-ray voltage and current)
, Conditions (information) such as the amount of rotation of the tube and detector (angle), and the amount of movement of the tube and detector are stored. The second row contains the second tube 3-2. Is the status flag, X-ray condition (X-ray voltage and current) of the third tube 3-3 and the n-th tube 3-n in the n-th row, the rotation speed of the tube and the detector, Conditions (information) such as the movement amount of the tube and the detector are stored. As an example of driving operation of the X-ray generation source, tube, and detector based on the scanning condition list, for example, the central control unit scans the first tube 3-1 from the scanning condition list “state = 1; 120 KV; 50 mA; 1 rps; 2
When “mmps” is read and a command (signal) based on the scanning condition is sent to the control units 6, 7, and 8, the X-ray control unit 6 sets the supply voltage to the X-ray generation source of the tube 3-1 to 120 KV, The X-ray generation amount is controlled by setting the current to 50 mA, and the rotation control unit 7 rotates the tube 3-1 and the detector 4-1 so that the rotation speed of the tube 3-1 and the detector 4-1 is 1 rps. A drive control signal is sent to the apparatus, and the optical system position control unit 8 moves the tube 3-1 and the detector 4-1 so that the moving amount of the tube 3-1 and the detector 4-1 is 2 mmps ( A drive control signal is sent to (not shown).

In the present embodiment, the X-ray CT apparatus 1 performs a helical scan on the subject, and a data reconstruction device (not shown) detects the detectors 4-1, 4-2, 4-3 and the position data of the bed 10 in the body axis direction are taken in, and based on the taken-in data, a set of interpolation data at an arbitrary slice position by interpolation processing (see Japanese Patent Laid-Open No. Hei 2-21129). And image reconstruction is performed based on the set of interpolation data.

In the present embodiment, when an error occurs during scanning of the tube, for example, if an error occurs in the X-ray part of the first tube (tube 3-1), the error occurs in the tube 3-1. X
The line control unit 6 discriminates from the status bits and sends a status (status) bit to the central control unit 12. The status bit includes a tube unique number and a bit flag indicating the tube status. The central control unit 12 checks the status bit and sends a use prohibition code for the tube 3-1 to the rotation control unit 7 and the optical system position control unit 8. The rotation control unit 7 and the optical system position control unit 8 send a drive stop signal to the rotation driving device and the moving device of the tube 3-1 and the detector 4-1. The central control unit 12 is a tube 3-
After confirming that all the movements of 1 have stopped, the scanning condition of the first tube 3-1 is sent to another tube that is not currently used, and that tube is moved to the tube 3-1. Use instead.

The effects of this embodiment will be described below.
(B) Helical dynamic scan is possible.
Helical scan is a method of scanning a subject in a spiral shape, and can scan a wide range quickly. Further, any portion within the scanned range can be converted into an image. On the other hand, in dynamic scanning, it is possible to observe and photograph changes over time in a scanning position by continuously scanning a certain position. According to the CT apparatus of the present embodiment, when the range d is helically scanned by a plurality (three in the figure) of the tubes 31a to 31c as shown in FIG. 3A, as shown in FIG. In addition, changes with time of the images at the respective positions P1 to P4 can be seen. That is, helical dynamic scan is possible.

Further, when creating a difference image using helical dynamic scanning and observing the change of the contrast agent over time, the trajectories of the respective tubes 31a to 31c need to be equalized as shown in FIG.
About this, it can set easily from the relationship between the space | interval of the tube 31a-31c, and the feed rate of a subject. To determine how many seconds later the same part of the subject is scanned, the tube 3
It can be determined by the interval 1a to 31c and the mounting angle of the tube balls 31a to 31c. Further, by shifting the mounting angles of the tube balls 31a to 31c, as shown in FIG.
The interval h of 1c can be made narrower than the width of the tube itself. That is, for example, when the radius of the tube is 100 [mm], the interval between the tubes is at least 20 unless the mounting angle is set.
Although 0 [mm] is required, this interval can be set to 0 [mm] or more by attaching an attachment angle.

If such a helical dynamic scan is used, a cine display 34 can be displayed along the change over time in a three-dimensional image as shown in FIG. This display is expected to be effectively used, for example, in the field of neurosurgery.

(B) The same range can be scanned at approximately the same time under multiple shooting conditions.
For example, if a subject (patient) 40 is simultaneously scanned from above and from the side by two sets of optical systems 41 and 42 as shown in FIG. 6A, a top-bottom (top) as shown in FIG. -Bot
tom) images and right-left image scanograms can be obtained. In addition, scanning in which the rotation speed of the beam and the optical system is changed for each optical system can be performed almost simultaneously in the same range. As a result, the scanning can be performed under different scanning conditions before the contrast agent is washed away. In addition, the patient throughput is improved and the burden on the patient is reduced. Further, it is possible to save the trouble of scanning again when it is desired to scan under different conditions or when photographing fails. This is particularly effective in research that requires scanning under various conditions.

(C) A plurality of parts can be simultaneously photographed under scanning conditions corresponding to the parts.
Simultaneously, a plurality of parts can be scanned under a scanning condition corresponding to the part. This is more effective, for example, in the case of group screening. In this case, for example, in FIG. 7, the tube 51 can scan the chest and the tube 52 can scan the abdomen. These scans can be performed at the same time by setting the scanning conditions according to the region, so that accurate diagnosis can be made, X-ray exposure can be minimized, and the scanning time per person is short. That's it.

(D) Even when a used tube is no longer usable, it can be switched to another tube.
The main cause of downtime of conventional devices is tube failure. However, in this embodiment, since there are a plurality of tube balls, a tube tube that is not used can be used as a spare when the capacity of the tube is full or when the tube is broken. For this reason, although it becomes impossible to perform an inspection that requires the use of all the tubes at the same time, the inspection can be continued using the remaining tubes. Therefore, there is no downtime due to a failure of the tube, and an emergency inspection can always be handled.

(E) A certain range can be scanned in a shorter time than before.
FIG. 8A shows a conventional helical scan in which a helical scan is performed with one tube, and the time for one scan in this case is t. On the other hand, FIG. 8B shows a case where the same part is scanned with two tubes according to the present invention, and the scanning time in this case is 1 / 2t. As described above, when scanning is performed with n optical systems according to the present invention, photographing can be performed in the conventional 1 / n time. This is more effective when scanning must be performed within a short time, such as when a contrast medium is injected.

(F) Spatial resolution can be improved.
When the same range is imaged within a certain period of time, imaging is performed with a plurality of optical systems, so that scanning can be performed densely and the spatial resolution in the direction along the body axis can be improved.

(G) A dual energy scan can be performed.
If two or more tubes use different X-ray energies, dual energy scanning can be easily performed.

That is, by imaging the same part with two or more types of X-ray energy, an image for each energy can be obtained. By using these images, an image representing the electron distribution density, the degree of Compton scattering, and the photoelectric effect can be obtained by calculation. These are useful information for estimating the elemental composition of the subject. Since the ratio of Compton scattering intensity and photoelectric effect intensity differs for each element, X-ray absorption is determined by these two scattering effects and the density of the substance.

The present embodiment is not limited to the above-described embodiment. For example, as shown in FIG. 10A, scanning may be performed with a plurality of (three in the figure) gantry 65 to 67 arranged in parallel. . In such a configuration, the interval between the X-ray tubes cannot be reduced to a certain extent, but FIG.
As shown to (B), each gantry 65-67 can be tilted.

The conceptual diagram of the X-ray CT apparatus which is one Embodiment of CT apparatus based on this invention. FIG. 2 shows a configuration diagram of a control unit and an example of a scanning condition list in the embodiment of FIG. 1. A partial view A shows an example of a helical dynamic scan, a partial view B shows a plurality of head images taken over time by the helical dynamic scan, and a partial view C shows a three-dimensional image by the helical dynamic scan along the time-dependent change. An example of a cine display is shown. An example in which the tube is aligned with the helical trajectory of the helical scan is shown. The example which shifted the attachment angle of each tube is shown. Partial view A shows an example in which the same range is scanned at approximately the same time under a plurality of imaging conditions, and partial view B shows the resulting image. An example in which another part is simultaneously scanned under a scanning condition corresponding to the part is shown. Partial view A shows a conventional helical scan in which a spiral scan is performed with one tube, and partial view B shows a case where the same part is scanned with two tubes according to the present invention. Partial view A is a perspective view showing an example of scanning by a conventional helical scan CT apparatus, partial view B is a side view, and partial view C is a view seen from a gantry. An example of photographing using a plurality of gantry is shown.

Explanation of symbols

1 X-ray CT system (CT system)
2 gantry 3-1, 3-2, 3-3 tube 4-1, 4-2, 4-3 detector 11 bed 10 bed driving unit 12 control unit

Claims (1)

X for reconstructing a CT image of the subject based on projection data obtained by scanning the subject
In line CT equipment,
A first imaging system having a first X-ray source for exposing X-rays and a first detector for detecting X-rays transmitted through the subject;
A second imaging system having a second X-ray source for exposing X-rays and a second detector for detecting X-rays transmitted through the subject;
The X-ray energy irradiated from the first X-ray tube of the first imaging system is different from the X-ray energy irradiated from the second X-ray tube of the second imaging system, and An X-ray CT apparatus comprising control means for scanning the same position of a subject.