JPH0567285B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention belongs to the technical field of CT devices, and in particular,
The present invention relates to a CT apparatus that can obtain CT images of a subject part undergoing periodic body movements, such as the heart.

[Technical background of the invention and its problems]

In a conventional CT device, such as a heartbeat-coupled X-ray CT device, an X-ray CT image of a region to be examined, such as the heart, that undergoes periodic body movements is obtained in the following manner. That is, as shown in USP4182311, by intermittently rotating an X-ray tube around the body axis of a patient, for example, and emitting X-rays at a predetermined angle of rotation, for example, every 0.6°. A large number of projection data are obtained and the patient's electrocardiogram data is collected simultaneously. After completing multiple scans, select the projec- tion data at the same phase of each heartbeat from among all the proge-exion data obtained, and use the selected proj-execution data as the proge-execution data at a predetermined rotation angle. At the same time, for rotation angles for which there is no projection data, the projection data of adjacent rotation angles is supplemented by interpolation, and the resulting projection data of 360/number of rotation angles is reconstructed. By doing so, an X-ray CT image of the heart was obtained.

However, during multiple scans (required time, for example, approximately 20 seconds) of X-ray CT images obtained by the heart rate-linked X-ray CT device, the patient may be holding his or her breath.
This can be achieved on the premise that the chest is not displaced by keeping the exhalation shallow so as not to move the chest. If a patient takes a deep breath or changes their body position during imaging with a heartbeat-linked X-ray CT device, the position of the heart will change, causing artifacts in the reconstructed X-ray CT image. Spatial resolution may deteriorate.

[Object of the Invention] This invention has been made in view of the above-mentioned circumstances. During an X-ray scan to obtain an X-ray CT image,
Provides a heartbeat-linked X-ray CT device that can obtain X-ray CT images without artifacts and without deterioration of spatial resolution even when the patient takes a deep breath or changes his/her body position. The purpose is to

[Summary of the invention]

The outline of this invention for achieving the above object is as follows:
data collection means capable of collecting projection data from multiple directions of the subject multiple times in succession; heart rate detection means for detecting the heartbeat of the subject; A body movement detecting means for detecting the presence or absence, and projection data collected by the data collecting means, for each specific phase of the heartbeat detected by the heartbeat detecting means, The apparatus is characterized by further comprising a calculation means for extracting the projection data corresponding to a period in which there is no body movement detected by the body movement detection means and performing a reconstruction process.

[Embodiments of the invention]

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

The heart rate linked X-ray CT device according to the present invention has a first
It is configured as shown in the figure. In the figure, reference numeral 1 indicates an arithmetic control unit which, when an operator operates an operation console (not shown), starts the operation of each part of the device, which will be described later, and outputs a start control signal 2 to control it. After inputting various data such as the excision data 8 and the electrocardiogram signal 11 and associating them temporally, the associated data is output as scan data to an auxiliary storage device 13, which will be described later. Read out more necessary scan data and rearrange it,
It is configured to reconstruct an X-ray CT image.
Reference numeral 3 designates a frame, which is equipped with an X-ray source 5 and, upon receiving the start control signal 2, rotates the
The radiation source 5 is configured to rotate around the subject 7 . 4 is an X-ray generation control device,
Upon receiving the start control signal 2, a high voltage is applied to the X-ray source 5 at fixed time intervals in synchronization with the rotation of the gantry 3, so that the X-ray source 5 irradiates the subject 7 with X-rays. It is composed of Note that the X-ray source 5 emits X-rays toward the subject 7 in a fan shape. Reference numeral 6 indicates a detector, which is arranged opposite to the X-ray source 5 and rotates together with the X-ray source 5, or is fixedly arranged in a concentric circle outside the circular locus in which the X-ray source 5 rotates. , all the transmitted X-rays transmitted through the subject 7 at the rotation angle of the X-ray source 5 are detected, and projection data 8 is output to the arithmetic control section 1. 9 is an electrocardiocardial respiratory monitor,
An electrocardiogram signal 11 and bioelectrical impedance 12 are collected by a pair of electrodes 10 attached to the subject 7, and as shown in FIG.
By detecting the wave, an R-wave synchronization signal 11a is oscillated, and the bioimpedance 12 is separated into Z ₀ 12b and ΔZ ₀ 12a as shown in FIG. 3, and body position fluctuation is detected by Z ₀ 12b. At the same time, the body movement detection signal 12d is oscillated, and ΔZ ₀ 12a
oscillates a deep breathing detection signal 12c that detects a deep breathing, and then adds the body movement detection signal 12d and the deep breathing detection signal 12c to generate a body movement deep breathing detection signal 12.
e, and outputs a body movement deep breathing detection signal 12e to the calculation control unit 1 together with the R wave synchronization signal 11a. Reference numeral 16 denotes a display device, which is capable of displaying the X-ray CT image reconstructed by the arithmetic and control device 1 on, for example, a CRT monitor. Reference numeral 13 denotes an auxiliary storage device, which is a memory that temporarily stores scan data obtained by temporally correlating the arithmetic and control unit 1.

Next, the operation of the heartbeat linked X-ray CT apparatus having the above configuration will be described.

When an operator operates an operation console (not shown), a start control signal 2 is outputted from the calculation control 1 to other parts of the apparatus. In response to the start control signal 2, the X-ray generation control device 4 generates a high voltage, and the pedestal 3 rotates around the subject 7 by a constant rotation angle, for example, every 0.6°. Then, in synchronization with the rotation of the pedestal 3, the X-ray source 5 attached to the pedestal 3 irradiates the subject 7 with X-rays at constant time intervals at every constant rotation angle. The transmitted X-rays that have passed through the subject 7 are detected by the detector 6, and the detected data is output to the arithmetic and control unit 1 as projection data. In this way, the X-ray source 5 can, for example,
X-rays are emitted once every 0.6°, and the area around the subject 7 is
When rotated 360 degrees, data of 600 projections are collected in the arithmetic and control unit 1. However, collection of projection data is achieved not only by one rotation of the X-ray source 5, but also by rotating the X-ray source 5 around the subject 7 a predetermined number of times. Note that when the X-ray source 5 rotates once and returns to its original position, it takes a certain pause, and then projection data is collected again by the rotation of the X-ray source 5 around the subject 7.

On the other hand, the electrocardiogram/respiratory monitor 9 collects the electrocardiogram signal 11 and bioelectrical impedance 12 of the subject 3 through a pair of electrodes 10 attached to the subject 7 while the pedestal 3 is rotating. The R-wave synchronization signal 11a obtained by detecting the waves is oscillated, and a body movement deep breathing detection signal 12e is created based on the bioimpedance 12, and the electrocardiogram signal 11, the R wave synchronization signal 11a, and the body movement deep breathing are sent to the processing unit 1. A detection signal 12e is output. The arithmetic processing unit 1 temporally associates the collected total projection data 8 with the input electrocardiogram signal 11, R-wave synchronization signal 11a, and body movement deep breathing detection signal 12e, and uses the correlated data as scan data. is temporarily stored in the auxiliary storage device 13. When the collection of scan data for the predetermined number of scans is completed in this way, the arithmetic control unit 1 collects the scan data of all the scan data stored in the auxiliary storage device 13 as shown in FIG. The projection data is extracted for each phase formed by dividing the heartbeat cycle into 12 equal parts, for example, and rearranged as follows. That is, for projection data of a specific phase, for example, the second phase in the heartbeat cycle, as shown in FIG. 5, for example, as shown in FIG. The projection data that temporally corresponds to the periodic second phase 11b is extracted and set as the first scan second phase data 14a, and in the same manner, the second scan second phase data 14b and the third scan data are extracted from the second scan data. 3rd scan 2nd phase data 1 from scan data
4c, the second phase data is extracted from all the scan data and rearranged in accordance with the rotation angle of the X-ray source. Even if it is due to rearrangement,
If the second phase data for a specific rotation angle cannot be obtained, by supplementing with interpolated data 15 obtained from the second phase data for rotation angles before and after the rotation angle, data for all rotation angles with respect to the heart can be obtained. All projection data of the second phase 1
Get 4. Phase data regarding other phases can also be obtained in the same manner as described above. By reconstructing the image for each phase data for all the rotation angles obtained, an X-ray CT image for each phase of the heartbeat cycle is obtained, and this is displayed on the CRT monitor of the display device 16.

The X-ray CT image obtained as detailed above is
Since it is constructed based on the projection data obtained by excluding the projection data of subject 7 during body movements and deep breathing, there are no artifacts caused by body movements or deep breathing, and This means that the spatial resolution has improved.

Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the embodiment described above, and can be implemented with appropriate modifications within the scope of the gist of the invention.

〔Effect of the invention〕

According to this invention, even if the position of the heart changes due to the subject moving or taking a deep breath during radiation exposure, the projection data obtained when the heart position changes can be removed. Since image reconstruction is performed using the same method, CT images with excellent spatial resolution and no artifacts can be obtained. Accordingly, it is possible to provide a CT apparatus that can perform accurate medical diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the positional relationship between an electrocardiogram signal and an R wave detection signal, and FIG. 3 is a diagram showing Z ₀ and ΔZ ₀ separated from bioimpedance. Figure 4 is an explanatory diagram showing the positional relationship between body movement and deep breathing detection signals, Figure 4 is an explanatory diagram showing the equal division of the heartbeat cycle, and Figure 5 is an explanatory diagram showing the equal division of the heartbeat cycle, and Figure 5 is the extraction of data of a specific phase from all the collected scanning data. FIG. 1... Arithmetic control unit, 2... Start control signal,
3... Frame, 4... X-ray generation control device, 5... X
Radiation source, 6...Detector, 7...Subject, 8...Projection data, 9...Electrocardiogram respiratory monitor, 1
0... Electrode, 11... Electrocardiogram signal, 11a...R
Wave synchronization signal, 11b... Heartbeat cycle second phase, 12
...Biological impedance, 12e...Body movement deep breathing detection signal, 13...Auxiliary storage device, 14...All projection data of a specific phase, 15...Interpolated data.

Claims (1)

[Claims] 1. A data collection means capable of collecting projection data from multiple directions of a subject multiple times in succession by multiple scans; a heartbeat detection means for detecting the heartbeat of the subject; body movement detection means for detecting the presence or absence of body movement; and identification of at least the heartbeat detected by the heartbeat detection means among the projection data collected by the data collection means. a storage means for extracting and storing projexion data for each scan corresponding to the phase and corresponding to a period in which there is no body movement detected by the body movement detecting means; and a projexion data outputted from the storage means. 1. A tomography apparatus comprising: a calculation means for performing reconstruction processing using Yon data.