JPH01139038A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To shorten a time and to set the capacity of a memory circuit to the necessary min. value, by generating not only the first address signal every step of scanning but also the second address signal corresponding to the bio- signal from an object to be examined and writing the data obtained from an X-ray detector at every step of scanning in the address indicated by each of the first and second address signals. CONSTITUTION:The angle of rotation of a disc 2 is detected by a rotation detector 6 and the angle signal thereof is sent to an address generating circuit 9 through an interface circuit 7. This address generating circuit 9 generates the address signal (x) corresponding to the inputted angle signal and the bio- signal of an object to be examined is amplified by a bio-signal amplifier 10. Said bio-signal is sent to a timer circuit 11 and the phase signal corresponding to the time from the predetermined phase of the bio-signal is formed and sent to an address generating circuit 12 to generate the address signal (Y) corresponding to the phase of the bio-signal. The X-ray transmission data sent to a memory 8 through the interface circuit 7 is written in the address indicated by both address signals X, Y.

Description

[Detailed description of the invention] [Industrial application field]

This invention is based on X li CT (Computed T
X-ray C, which is particularly suitable for capturing images synchronized with biological signals such as electrocardiogram signals, regarding
Regarding the T device.

[Conventional technology]

2. Description of the Related Art Conventionally, an X-ray CT apparatus has been used to capture images in synchronization with biological signals such as electrocardiographic signals. In other words, by collecting X-ray transmission data in synchronization with biological signals, extracting only data within a certain range of the phase of the biological signal, and reconstructing a tomographic image of the biological body from them, a tomographic image at that phase is obtained. be able to. In this case, in order to reconstruct the tomographic image, at least 180
Projection data from the ° direction is required. Conventionally, in order to obtain this necessary data, data is collected by performing multiple scans, and only data in a specific phase range is selected from the data and used for image reconstruction. This is called a curve scan when an image is reconstructed in synchronization with electrocardiographic signals. When collecting X-ray transmission data, information on biosignals is also added and recorded at the same time, and later, this information on biosignals is used as an index to
This is to select the line transmission data.

[Problems to be solved by the invention]

However, it is not possible to collect X-ray transmission data by simply adding information about biological signals in this way.
There is a problem in that the information regarding this biological signal must be read later and it is determined whether the data is necessary or not, which takes time. That is, in order to obtain a single image with a certain phase of biological signals, a large amount of data obtained through multiple scans must be read out one by one to make the above judgments, which takes a very long time. The present invention provides an X-ray CT apparatus that is capable of reconstructing an image of a specific phase of a biosignal immediately after data collection and recording by a required number of scans is completed, without reading information about the biosignal and making a judgment. The purpose is to provide

[Means to solve the problem]

The X@CT apparatus according to the present invention includes an X-ray generator, an X-ray detector disposed opposite to the X-ray generator across a space in which a subject is placed, and the X-ray generator and the X-ray detector. a scanning mechanism that scans a space in which the subject is placed; a first address signal generation circuit that generates a first address signal for each step of scanning;
a second address signal generation circuit that generates a second address signal in response to a biological signal from the subject;
, and a memory circuit that writes to the address specified by the second address signal.

[For production]

The X-ray generator and the X-ray detector are scanned, and the X-ray transmission data obtained from the X-ray detector at each step is stored in the memory circuit. It not only corresponds to the steps of scanning, but also corresponds to biological signals from the subject. Therefore, after data has been written to this memory circuit, if only the data at a certain address corresponding to the biosignal from the subject is read out, the data will only be for a specific phase of the biosignal. It can be used as is to reconstruct a tomographic image at a specific phase of the biological signal.

【Example】

FIG. 1 shows an embodiment in which the present invention is applied to a third generation X@CT device. In this FIG. 1, a subject (patient) 1 is inserted into a hole 21 provided in the center of a disc 2. An X-ray tube 3 and an X-ray detector 4 are arranged facing each other on the zero disc 2 with the hole 21 in between, and a data acquisition device is provided in which the output signals of each channel of the X-ray detector are input. 5 is attached. When this disk 2 is rotated around the hole 21 by a rotation drive mechanism (not shown), the X-ray tube 3
, the X-ray detector 4 and the data acquisition device 5 also rotate together, and the subject 1 is scanned with X-rays. The data acquisition device 5 collects data from the output of each channel of the X-ray detector 4 at each step (angle) of this rotation (scan) and sends it to the memory 8 via the interface circuit 7. On the other hand, the rotation angle of the disk 2 is detected by a rotation detector (for example, a rotary encoder) 6, and the angle signal is sent to an address generation circuit 9 via an interface circuit 7. This address generation circuit 9 generates an address signal (this is referred to as an X signal) corresponding to the input angle signal. Further, the biological signal of the subject 1 is amplified by the biological signal amplifier 10. When the biological signal amplifier 10 is an electrocardiograph, electrocardiographic signals are amplified. This biosignal is sent to the timer circuit 11, which generates a phase signal corresponding to the time from the predetermined phase of the biosignal, and this is sent to the address generation circuit 12, which generates an address signal corresponding to the phase of the biosignal. X signal) is generated. The X-ray transmission data outputted from the data acquisition device 5 and sent to the memory 8 via the interface circuit 7 is written to the address designated by these address signals X and Y. First, normal imaging in which imaging is not performed in synchronization with biological signals will be described. In this case, the address signal Y is not generated from the address generation circuit 12 (Y=0), and the X-ray transmission data is written exclusively to the address corresponding to the angle signal. That is, as shown in FIG. 2, for each address X corresponding to an angle, data of all channels 1, 2, . . . collected at that angle is written. Therefore, when all the data has been written to the memory 8 in this way, the stored contents are read out and
If processed by an image reconstruction device such as a back projection device (not shown), a normal tomographic image unrelated to biological signals can be obtained. Next, a case will be described in which an electrocardiographic signal is detected as a biological signal and imaging is performed in synchronization with the electrocardiographic signal. The electrocardiographic signal has a waveform as shown in FIG. 3, and one cycle from its peak to the next peak is divided into four phases A, B, C, and D. By creating a signal according to the time from the peak using the timer circuit 11, phase signals corresponding to each of the phases A to D can be obtained. Here, for convenience, disk 2 is 1
It is assumed that one scan is obtained by rotating the image by 80° (π radian), and the time required for one scan is four cycles of the electrocardiographic signal. When the first scan S1 starts, the angle is 0.
The data of all channels is output one after another from the data acquisition device 5 in predetermined angle units starting from radian and sent to the memory 8, but the address signal Y corresponds to the phase A up to the angle π/16 radian. As shown in FIG. 4, it is stored at an address corresponding to phase A. That is, the data from 0 to π/16 radians in scan S1 belongs to the phase A range, and is
SI, this data DASI is stored at an address as shown in FIG. Then, the next angle π/16
Data oast belonging to the range of phase B from radian to 2π/16 radian corresponds to the address corresponding to phase B, and data DC3t belonging to phase C from the angle 2π/16 radian to 3π/16 radian corresponds to phase C. from the angle 3π/16 radians to 4π/1
Data DDSI with a phase shift range of up to 6 radians
are written to addresses corresponding to the phase difference. In this way, data belonging to each phase range obtained in the first scan S1 DASI, I) ast, [) cst, o
ost is sequentially written up to π radians as shown in FIG. Assuming that the second scan S2 shifts the starting phase and starts from the beginning of the phase range, data DO52 belonging to the phase range from angle O radian to π/16 radian is shown in FIG. is the address corresponding to the phase difference, and data DAS2 belonging to the range of phase A from angle π/16 radian to 2π/16 radian is stored at the address corresponding to phase A, and further from angle 2π/16 radian to 3π/16 radian. Data DB belonging to phase B of
S2 is written to an address corresponding to phase B, and data DC32 belonging to a range of phase C from angle 3π/16 radians to 4π/16 radians is written to an address corresponding to phase C, respectively. In this way, by repeating the scan several times while shifting the starting phase of each scan, the blank area in Figure 4 is filled in, and A
, B, C, and D, all of the necessary data in the 180° direction has been collected. When data collection is completed in this way, if the stored contents of address A are read out in the X direction (angular direction), the necessary 1 for phase A can be obtained.
Data for 80° is immediately obtained, from which an image can be reconstructed to obtain a tomographic image at phase A. Note that when data is collected by repeating multiple scans, data for the same angle and the same biosignal phase may be obtained overlappingly. In this case, when attempting to write subsequent data, the data has already been written to the address to which it should be written, so the configuration is such that this is detected and the data is not written, or is written redundantly. In this way, the memory 8 can be stored at 180° for each phase of the biological signal.
The storage capacity can be minimized by only having a capacity of 1. By the way, in the past, since it was not known at the time of writing whether data was duplicated or not, it was necessary to record all the data obtained through multiple scans, which required an extremely large storage capacity. Although the angle signal is obtained from the rotation detector 6 in the above example, such an angle detector 6 may not be used. That is, since the rotational speed of the disk 2 is constant, it is considered that the order of data sequentially output from the data collection device 5 at fixed time intervals from the start of rotation corresponds to each angle. Therefore, the address signal may be generated by assuming that the order in which data is output from the data collection device 5 represents the angle.

【Effect of the invention】

According to the Xl1CT device of the present invention, after data collection and recording in the storage circuit is completed, it is possible to read out only the data at a specific address and use it as is to immediately reconstruct an image of a specific phase of the biological signal. This can save time. Further, it is possible to minimize the capacity of the memory circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIGS. 2 and 4 are diagrams schematically representing the relationship between memory contents and addresses, and FIG. 3 is an electrocardiographic signal waveform and its phase. 3 is a time chart showing the relationship between scanning and scanning. 1... Subject, 2... Disc, 21... Hole, 3...
・X-ray tube, 4... X-ray detector, 5... Data acquisition device, 6... Rotation detector, 7... Interface circuit, 8... Memory, 9.12... Address Generation circuit, 10... biological signal amplifier, 11... timer circuit.

Claims (1)

[Claims] (1) An X-ray generator, an X-ray detector disposed opposite to the X-ray generator across a space in which the subject is placed, and the X-ray generator and the X-ray detector a scanning mechanism that scans the space in which the image is placed, and a first address signal that generates a first address signal for each step of the scan.
a second address signal generation circuit that generates a second address signal in response to a biological signal from the subject; 1. An X equipped with a memory circuit that writes to an address specified by a second address signal.
Ray CT device.