JPS5937935A - X-ray ct apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an X-ray system that connects an X@CT device, particularly an electrocardiograph, etc., to obtain an image of a certain section of the heartbeat. C
This relates to the T device.

[Technical background of the invention]

For example, an X-ray CT device includes an X-ray source that emits fan-shaped fan beam X-rays along a planned plane and with a spread angle that is flat and includes the object, and a planned interval between the X-ray source and the object. X-ray detection having a one-dimensional positional resolution corresponding to an angle with respect to the nine directions of the fan-shaped spread, which is constructed by arranging a plurality of radiation detection elements facing each other in parallel in the direction of the spread of the fan beam X1fJ. The apparatus is rotated and scanned integrally relative to the object in the same direction with respect to the arrangement position of the object, and a large number of X-ray projection data from multiple directions of the object obtained by this rotational scanning are Based on this, an image of a fan beam X-ray transmission cross section of the object is reconstructed by a computer-based image reconstruction processing means that forms a tomographic image based on the X-ray transmittance distribution of the object.

A fan beam X-ray with a wide spread 9 is used, the object is included within the width of the fan beam X-ray, and the X-ray source and radiation detector are rotated and scanned relative to the object. A CT system that uses X-rays to obtain X-ray projection data is called 3rd generation CT.
There are various methods such as □ generation, second generation, and fourth generation.

By the way, in the third generation CT apparatus, conventionally, when obtaining a tomographic image of an organ that moves rapidly like a kite, CT
Since it takes several seconds to several seconds to collect the X-ray projection data necessary to reconstruct one image of the device, the electrocardiographic waveform of the subject and the X-ray projection data are collected separately. , This was later compared and the X-ray projection data of a certain section of one heartbeat was extracted and used for image reconstruction.
By synchronizing the electrocardiogram waveform with a certain timing pulse, the rotational scanning speed of the CT apparatus was controlled.

However, in the former case, X in any section during one heartbeat
In order to collect enough line projection data for image reconstruction, one rotational scan (ordinary one screen) is insufficient, and rotational examination for multiple rotations is required. In other words, the heart rate cycle is roughly equivalent to one revolution of the CT machine! Since the movement occurs at a much faster cycle than the time required for rotational scanning, the X-ray projection data corresponding to a desired heartbeat interval is obtained by one rotational scan, and the total X-ray projection data obtained is approximately one pole. It's just a department.

Therefore, in reconstruction, insufficient angular direction and reverse projection data appear, and it becomes necessary to repeat rotational scanning many times to obtain this data. , Therefore, for this method,
In addition to taking longer time to collect data, there is a lot of wasted radiation exposure for the subject, so 5 is not a good idea because it means reducing the amount of exposure to harmful X-rays.

In the latter case, the X-ray projection angle is gradually changed according to the heartbeat movement.

Although unnecessary exposure to radiation will be eliminated, the time required to collect data will become extremely long.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and provides an X-ray CT apparatus that can efficiently collect X-ray projection data of any section during a heartbeat, and that can suppress the exposure dose to a minimum. That is, in order to achieve the above object, the present invention aims to:
1-The entire electric signal is collected using a rotational scan or an equivalent acquisition cycle when emitting X-rays, and the average heartbeat cycle of the subject is known, and from this, the desired heart rate obtained with one rotational scan is obtained. Obtain the five projection angles of the X-ray projection data of the phase interval, and further calculate the number of rotational scans required to collect the X-ray projection data of the entire projection angle range. Based on the heartbeat cycle necessary to obtain the rotation scan start timing for each rotation scan, rotation scans are performed for the determined number of rotation scans, and X-ray projection data is collected.

[Embodiments of the invention]

An embodiment of the present invention will now be described with reference to the drawings.

The figure is a professional diagram showing the configuration of this device, 1 is the subject, 2 is a flat Xr with a width that includes the subject 1.
1. An X-ray tube that emits fan-shaped fan beam X-rays Xf. ?
is a radiation detector which is opposed to a human X-ray tube 2 through a subject l, and has a plurality of radiation detection elements arranged in parallel in the spreading direction of fan beam X-rays Xf, and the X-ray tube 2 and the radiation detector 3 is held by a rotation support mechanism (not shown) and is configured to rotate integrally around the cast position of the subject 1. 4 is an electrocardiograph for extracting the electrocardiogram waveform of the subject 1; 5 is each Xfs of the radiation detector 3;
This is a data acquisition unit that converts the X-ray detection output from the detection element into a digital signal, and also converts the output of the electrocardiogram 1114 into a digital signal and outputs the digital signal. 6 is an X-ray control/generation unit that sets values such as tube voltage and tube current to be applied to the X# tube 2, and also generates a high voltage corresponding to the set value and applies it to the X-ray tube 2; 7 is an X-ray control/generation unit of the CT apparatus; A control console for inputting various commands and data, 8 a system control unit that controls the entire system according to commands from the control console 2, and 9 operating the rotation support mechanism in response to control signals from the system control unit 8. 1o is a computer that receives the digital signal data output from the data collection unit 5 and performs arithmetic processing to reconstruct an image; 11 is an image display device that displays the reconstructed image, etc.; be.

Next, the operation of this apparatus having the above configuration will be explained. When the operator operates the control console 7 to issue a data collection command, this command is sent to the system control unit 8, and the system control unit 8Fi.

An X-ray exposure command is given to the X-ray control/generation section 6, and a command to start rotation scanning control of the rotation support mechanism is given to the mechanism control section 9. As a result, the X-ray control/generation unit 6 generates a high voltage (~[, and applies it to the X-ray tube 2, and the X-ray tube 2 emits fan beam X-rays Xf. The rotation of the mechanism is controlled.

In a normal X@CT device, the X-ray tube 2 and the radiation detector 3 are integrally moved around the position of the subject 1 by means of a rotating support mechanism while irradiating the beam with a beam of X-rays Xf. is rotated and scanned, thereby Xa projections are made from all directions on the fan beam X@Xf transmission section of the subject 1, and the radiation detector 3 detects the transmitted X# intensity.

However, in the apparatus of the present invention, the electrocardiographic signals of the subject 1 are extracted by all members 14 at this time, and the electrocardiographic signals are inputted to the data collection unit 5 together with the outputs of each X-ray detection element of the radiation detector 3. The signals are converted into digital signals by A/D conversion and then input to the computer 1o.

Data is collected at a predetermined angle with respect to the tomographic plane of subject J, using fan beam X #! This is done by controlling the data collection unit 5 using a control signal from the system control unit 8 every time the projection angle of Xf changes. Based on the data of the electrocardiogram signal, it is possible to determine which phase of the heartbeat it is in.

By the way, the time required for rotational scanning for one sighting is several seconds at most.
However, since the heartbeat cycle is faster than this, the X-ray projection data corresponding to a certain phase interval of the heartbeat is the 8th line obtained by one rotational movement, and the projection depth is at the very end. The projection angle is often insufficient to obtain partial/complete reconstruction and images.

Therefore, it is necessary to repeat rotational scanning several times to collect X-ray projection data for the missing pitch angle.
,.

In this case, when I repeated the single rotation scan several times, the X-ray shadow data at a certain angle overlapped, which caused some missing data. A complete reconstructed image cannot be obtained with the foot.

Therefore, the following functions have been added to this device. That is, in the first rotational scan, the electrocardiographic signal data of the electrocardiogram i+ 4 and the subject 1 are collected at the same acquisition cycle and speed as when collecting the X-ray projection data without irradiating the fan beam X-rays Xf. , find the average heartbeat cycle t of the patient who is the subject. In this case, it is also possible to obtain electrocardiographic signals for a period corresponding to the rotational scan without necessarily performing rotational scanning.
is required.

This is performed by the data collection unit 5 under the control of the system control unit 8.
The computer 10 collects digital data of electrocardiographic signals and provides the data to the computer 10.

Next, depending on the time width of a fraction of one heartbeat, that is, which phase interval of the heartbeat cycle is determined, the X-rays at each projection angle necessary for image reconstruction of the heart in that interval are determined. Determine the number of rotational scans required to collect projection data.

This is determined by the computer 10 based on the above t. The desired phase interval in the heartbeat cycle is set by the operator using the control console 7. Then, this setting value can be changed from the control console 7 to the user 1.
0, 6t is determined, and the required number of rotational scans is determined. Furthermore, based on the obtained average heartbeat cycle t, the start timing of each rotational scan for obtaining X-ray projection data in different projection angle directions of the heart in the desired phase interval is also determined for each rotational scan.

When the above calculation is completed, the computer 10Fi performs X-ray exposure control and data collection so that X-ray projection data and electrocardiographic signals are collected at the rotation scan start timing corresponding to each rotation scan for the number of rotation scans obtained. 5 and mechanism control section 9 to automatically perform rotational scanning.

In this way, when the required number of rotational scans are completed, the computer 10 has obtained projection data of the desired phase section from all angular directions necessary for image reconstruction.

Therefore, the computer 10 selects the projection data of the desired phase interval from among all the collected projections and reconstructs the image. The reconstructed image is then displayed on the image display device 1111C.

In this way, the electrocardiographic signal is collected in advance by rotational scanning or an equivalent collection cycle without emitting X-rays, and the average heartbeat cycle of the subject is determined. Find the projection angle at which XSa shadow data can be obtained for each phase interval, find the rotational scanning equivalent necessary to collect X-ray projection data for all projection angles, and calculate the heart rate required to obtain X-ray projection data for all sleeve shadow angles. The rotation scan start timing for each rotation scan based on the cycle is determined, and the rotation scan is performed for the number of rotation scans determined above at this determined rotation scan start timing, and the X-ray projection data is collected, making it the most efficient. It is possible to collect X-ray projection data from all projection angle directions necessary for image reconstruction in any phase interval during heartbeat, and to obtain reconstructed images with good image quality. Become. Moreover, unnecessary X@ exposure can be kept to a minimum, and the exposure dose can be changed as appropriate without changing the gist of the present invention, without being limited to the embodiments described above and shown in the drawings. For example, in a third-generation CT device that uses pulsed X-rays, if only one section of one heartbeat is required, this method can be used to Since the collection timing of the X-ray projection data is known in advance, by controlling the X-ray exposure using the computer in accordance with the collection timing, it is possible to emit X-rays only at that time. In addition to being able to obtain the effect of reducing radiation exposure, it is also possible to efficiently perform image reconstruction processing without collecting wasteful X-ray projection data.

In addition to third-generation CT devices, the present invention also applies to fourth-generation CT devices in which the X-ray detector has a ring shape surrounding the subject and the X-ray source rotates and scans along the inside of the X-ray detector. It can be implemented and modified as appropriate.

Furthermore, the electrocardiographic signals collected in advance can be repeated multiple times to improve accuracy, rather than being limited to one rotational scan.

Furthermore, if the number of rotation scans required to obtain all projection data increases, the operator can specify an arbitrary number of rotation scans, and the optimal rotation scan timing can be set for the specified number of times. It is also possible.

〔Effect of the invention〕

As detailed above, the present invention includes an X-ray source that emits fan beam X-rays along a predetermined plane and having a predetermined fan-like spread angle, and a predetermined interval between the X-ray sources. a detector that faces the object and detects the intensity of the X-rays with a one-dimensional positional resolution corresponding to the angles in the multiple directions of the fan-shaped spread; The detector is arranged so that the object is contained therein, and the detector obtains X-ray projection data of the object, and substantially directs the fan beam X-rays from the X-ray source to the object perpendicular to the plane and toward the object. Collect X-ray projection data of the subject from multiple directions within the plane obtained only by relative rotation of the fan beam X-rays by rotating the fan beam X-rays relative to each other about an axis at a certain position, and collect this projection data. In a CT apparatus that performs image reconstruction processing to obtain a tomographic image based on the X-ray transmittance distribution of the subject along the plane, means for detecting electrocardiographic information of the subject is provided, and a means for detecting electrocardiographic information of the subject is provided. The average heartbeat period of the subject within the time required for the relative rotation of the fan beam X-rays is determined, and the calculated average heartbeat period is obtained by the relative rotation of the fan beam X-rays of - times. means for determining a projection angle at which X-ray projection data for a desired heartbeat phase interval can be obtained; means for determining the relative number of rotations of fan beam X-rays necessary to collect X-ray projection data for a projection angle range that is greater than the projection angle; means for determining the fan beam X-ray relative rotation start timing for each rotation based on the heartbeat cycle necessary to obtain X-ray projection data for the missing projection angle; The number of rotations determined by Tsumugi at the start timing,
A means for controlling the collection of X-ray projection data is provided, and the average heartbeat period in one 7-am X-ray relative rotation period is determined by referring to the electrocardiographic signal of the subject, and from this, one rotation period is determined. X@ of the phase interval which is the new home of the heart obtained by
Find the projection angle at which projection data can be obtained, and then find the necessary number of 7-beam X-ray relative rotations necessary to collect X-ray projection data in a projection angle range that adds up to this. Determine the rotation start timing for each rotation based on the heartbeat cycle necessary to obtain angular X-ray projection data, and at each rotation start timing determined, the determined number of rotations,
Since the X-ray projection data is collected by performing relative rotation of the fan beam
In addition, since the rotation start timing is controlled for each rotation to avoid insufficient angular X-ray projection data, artifacts caused by insufficient X-ray projection data can be prevented. We are now able to provide an X-ray CT system with excellent features such as eliminating the occurrence of this problem and obtaining high-quality reconstructed images.

[Brief explanation of the drawing]

The figure is a professional diagram showing one embodiment of the present invention. 1... Subject, 2... X-ray source, 3... X-ray detector, 4... Electrocardiograph, 5... Data collection unit, 6... X
Line control/generation unit, 7... Control console, 8
...System control section, 9...Structure control section, 10...
- Computer, 11... Image display device.

Claims (1)

[Claims] X41. an X-ray source, facing the X-ray source at a predetermined distance; The intensity of the X-rays is determined by the direction of the fan-shaped spread and the 6-dimensional position resolution corresponding to 0 angle 1 is also detected. The object is arranged so that it is included in the fan-shaped spread of 9 angles of the line, and the detector obtains the X and line projection data of the object, and in fact, qualitatively fan beam X-rays from a radiation source are rotated relative to the object pair around an axis that is perpendicular to the plane and located at the object position, and the front surface is obtained only by the relative rotation of the fan beam X-rays; OXS projection data is collected from various angles of the subject book in a trivial plane, and this projection data is reconstructed as an image.Acid treatment is performed to determine the X-ray transmittance distribution along the plane of the subject. In the CT apparatus for obtaining tomography, a means for detecting the electrocardiographic information of the subject is provided, and the average heartbeat cycle of the subject is determined by using the electrocardiographic information of the subject. In the □ relative rotation of the Fanby AX-ray described above before the period and the C times, □1□ The obtained i of the X-projection detector between the desired center and the case phase d, ,
ffi', means for calculating reflection angle, total projection angle range □
Means for calculating the relative number of rotations of the fan i-me necessary to collect the X-ray projection data of the □, and the heart rate 1tC11 necessary to obtain the total i-angle OX-ray projection data; s soft' % times □ Every dipping fan beam □ Means for determining the X-ray relative rotation start timing, the determined number of rotations at the determined rotation start timing for each rotation based on the electrocardiographic information,
XIII! The 'X@CT apparatus is equipped with means for controlling the collection of projection data and electrocardiographic information.