JPH01299489A - Emission ct apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform high-degree diagnosis, by providing a synchronized signal register which generates an output signal every time the predetermined number of external synchronized signals reach. CONSTITUTION:A trigger wave which is generated in synchronization with a wave R of an electrocardiographic complex outputted from an electrocardiograph 21 which is applied on a person to be examined is inputted 1. In a synchronized signal register 3b, the inputted trigger waves are counted. An output signal is generated for the every predetermined number, e.g., 10 waves. A measuring signal generator 5a generates a measuring signal whose pulse width is in the predetermined range of the phase for the trigger wave every time when a trigger wave inputted from an external synchronization signal input terminal 1. In a data memory 6, the number of the detected signals is stored at the appropriate positions in a memory space. They are the original data. The picked up original data are displayed on the display devices such as a character display monitor, an image display monitor and image display color monitor.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to X-ray CT (Computed CT).
aph) device, scintillation camera, positron emission CT (Posj tron Ell1)
issj, on ComputedTomograp
h) Emission CT of equipment, etc.
The present invention relates to a positron emission CT device having a scanning system suitable for obtaining good images by performing measurements in synchronization with external signals such as electrocardiographic pulses.

[Prior art] Conventionally, among positron CT devices, positron emission CT devices collect data in synchronization with the diastole or systole of the heart, and reproduce images of organs at each time. May be configured. In order to prevent image deterioration due to respiratory movement of various organs, not just the heart, data may be collected in synchronization with breathing.

The original data in a positron emission CT device is basically projection data in all directions (angles) within the tomographic plane.
taken evenly from That is, the positron emission CT apparatus uses a position detection type (p.

5ition) Measurement is performed by rotating the detector 180° or 360° within the tomographic plane. Positron emission CT with ring-shaped detector array
In the device, the detector array is, for example, wobbled in order to obtain projection data with a sampling density of 172 or less of the detector's intrinsic spatial resolution according to Nyquist's theorem.

The movement or scanning of the stiffness is performed over one or more cycles as necessary to complete the sampling;
As uniform a sampling as possible is obtained. However, in the wobbling process, sampling non-uniformity that is inherently periodic appears, but since this non-uniformity always shows a certain regularity, it can be corrected after the data is collected, and the problem can be corrected. doesn't happen.

On the other hand, heartbeat and breathing periodically deform the related organs. However, by repeatedly collecting data on these organs only at specific times (phases) within the cycle, we can remove blurred images due to movement and determine the shape of the organs at that phase. There are attempts to obtain For example, as shown in Figure 3, if you collect data only in the first half of the ECG by separating the interval between the R wave and the next R wave by half, you can obtain an image of the systolic phase 1 and 0 a of the heart. By collecting data in the second half, an image of the diastolic LOb can be obtained.

When trying to collect data of a specific phase synchronized with an external signal using a positron emission CT device that requires the above-mentioned scanning, an inconvenient phenomenon occurs. Considering a hypothetical condition like this, the scanning method of a rotating detector type positron emission CT device rotates at a constant speed from a sampling angle of O'' to 360° in 6 seconds and simultaneously performs measurements.
After a pause of 0°5 seconds, measurements are taken while rotating at a constant speed from 360° to O'' in 6 seconds, followed by a pause of 0°5 seconds, and this scanning is repeated thereafter. Let us consider a case where this device reconstructs an image of the systolic phase of the heart from data acquired in synchronization with cardiac IBR waves. Heartbeat is 1
Beats/second, and the systolic period is 0.5 seconds. 72 hypothetical conditions are shown in FIG. Under this condition, if a total of 811I is repeated for 0.5 seconds corresponding to the systolic period in synchronization with the heartbeat, data only for the systolic period can be collected. On the other hand, looking at what kind of scanning was done during the 31st measurement,
0°・~30", 606~90°, 120'~1.80
Although a total of 'A [1] is performed at sampling angles of ',..., 30'' to 60'', 90' to 1
．． 20', 150' to 180', -----)
No measurements have been taken between these sampling angles, and the projection data for these sampling angles will be missing.

Reverse rotation does not change the above situation because there is a rest period of 005 seconds before the detector begins to rotate in reverse. By partially missing the projection data in this way,
The quality of the reconstructed image is significantly degraded.

Even in a type of scanning such as wobbling scanning that improves the sampling density of each projection data, locally unmeasured portions occur in each projection data, which similarly degrades the reconstructed image.

In reality, in addition to this phenomenon, the heartbeat cycle is not necessarily constant, and furthermore, heartbeats that are completely out of periodicity, such as an irregular door, may occur, which complicates the problem.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, sufficient consideration was not given to the relationship between the external synchronization signal and scanning synchronization, and as a result, there was a problem in that sampling was locally lacking and the reconstructed image deteriorated. .

The present invention has been made to solve the above problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique that can eliminate local sampling loss in an emission CT apparatus and create an excellent reconstructed image of an organ whose phase is synchronized with an external synchronization signal.

The above and other unique and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, one aspect of the present invention is to provide an emission CT device that collects data by scanning a detector system unit using a drive motor, and a synchronization signal register that generates an output signal every time a predetermined number of external synchronization signals arrive. ,
a drive motor control circuit that receives the output signal and executes one-step scanning; and a measurement signal generator that generates a measurement signal having a pulse width corresponding to a predetermined phase range for each of the external synchronization signals. and a game that allows the period detection signal during which the measurement signal is generated to pass through and to be stored at an appropriate location in the data memory.
The main feature is that it is equipped with a smart circuit.

[Effect]

According to the above-mentioned means, each time an external synchronization signal is inputted to the synchronization measurement control device, the measurement signal generator generates a measurement phase signal specifying the time at which the synchronization hand 61q should be moved, and controls the gate circuit. open. Detection No. 01 from the detector passes through the gate circuit only during a specific phase period in which the measurement phase signal exists, and is stored in an appropriate position on the original data memory according to the information of the detection position signal accompanying the detection signal.

Once a predetermined number of said external synchronization signals have been input, a synchronization signal register in the scanning system sends an output signal to the drive motor control circuit and the scanning mechanism moves the detector array to the next scan step.

In this way, each scanning step is performed one after another for a certain period of time.
(Pulse width of measurement phase signal) x (number of external synchronization signals arriving within one step) J measurement data are accumulated. Therefore, sampling is performed for the same amount of time at all sampling points without any gaps, and image reconstruction is not hindered. As a result, it is possible to eliminate one local sampling defect and create an excellent reconstructed image of the organ whose phase is synchronized with the external synchronization signal.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

Note that throughout the description of the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

[Example I]

FIG. 1 is a plot diagram showing a schematic configuration of the main parts of a positron emission CT apparatus according to Example 2 of the present invention, and FIG. 2 is a schematic diagram showing the overall configuration of a positron emission CT apparatus according to Example I of the present invention. FIG.

The positron emission CT apparatus of Example I has a second
As shown in the figure, it consists of a detector system section I, a scanning device section (2), a bed section (2), a signal processing device section (2), an image processing device section (2), and an operation console section (2).

The detector of the detector system unit ② uses two ring-shaped detectors, for example.

As shown in FIGS. 1 and 2, the scanning device section (2) includes:
It consists of a scanning control device 3 and a scanning device 4. The scanning control device 3 consists of a synchronizing signal register 3a having an external synchronizing signal input terminal 1 as an input terminal, and a drive control circuit 3b receiving the output No. 1 of the synchronizing signal register 3a. The scanning device 4 consists of a drive motor 4a and a scanning mechanism 4b, and the drive motor 4a operates every time an output signal is generated from the drive motor control circuit 3b to drive the scanning mechanism 4b. The apparatus section I (second time) is moved from one scan step to the next step and then stopped.

In the signal processing device section (2), a synchronous measurement control device 5 is provided between the measurement data input terminal 2 and the data memory 6, into which the output of the detector system device section 1 (detection position information has already been determined) is input. , the operation is controlled by an external synchronization signal together with the scanning control bag [3].

On the other hand, the synchronous measurement 1l17IJ control device 5 includes a measurement signal generator 5a whose input terminal is the external synchronous signal input terminal 1.

The output measurement signal is used as a gate signal, and the output signal from the signal preprocessing circuit 2A converts the output signal from the detector or the detected position information of the signal into coordinates regarding the cross-sectional plane of the object (these are referred to as detection signals). gate circuit 5 whose input terminal is the measurement data input terminal 2 that inputs
Note that there may be a plurality of gate circuits 51) depending on the number of phases for which synchronous measurement is performed.

The gate circuit 5b is connected to a data memory 6 (consisting of two memories 6d) that accumulates and stores collected original data7.The external synchronization signal is, for example, a signal collected by an electrocardiograph 21. Uses electrocardiogram waveforms.

The image processing unit (2) is connected to a coincidence circuit 7 to which signals are input from the signal processing unit (2), a computer 8 that performs image processing, etc., a high-speed arithmetic circuit 9, a positive I to long data analysis device filOd, etc. communication interface 10
c. Peripheral device control circuit 12 and device control circuit 13 for controlling the magnetic disk 11, such as magnetic tape 12a, optical disk 12b, dot matrix printer 12r, etc.
It consists of a display circuit 14.

The operator console section (2) includes an operator console control circuit 15. which roughly controls the device control circuit 13. It consists of a keyboard 16 with a trackball, an external memory 17 such as a floppy disk, a monochrome monitor 18 for displaying characters, and a color monitor 19 for displaying images. Additionally, a multi-format camera 20 is provided as an option.

Next, the scanning operation of the detector system unit I of the positron emission CT apparatus of the present embodiment (2) will be explained.

1 and 2, the external synchronization signal input terminal 1 is connected to a trigger wave generated in synchronization with the R wave of the electrocardiogram waveform output from the electrocardiograph 21 applied to the subject. (for example, shaped into a rectangular wave) is input (see FIG. 3). The synchronizing signal register 3a counts the input trigger waves and generates an output signal every predetermined number, for example, every 10 trigger waves. When the output signal is input to the drive motor control circuit 3b, the drive motor control circuit 3b controls the scanning device 4.
After the scanning mechanism 4b operates the drive motor 4a to move the detector system bag [1 by one scan step, the drive motor 4a is stopped to prepare for the next scan.

The scanning for one step may be performed by using the drive motor 4a as a step motor and applying a predetermined number of drive pulse currents necessary for scanning one step to the drive motor 4a. 4 may be provided with a scanning device encoder, and the encoder output may be used to feed back "fill" to the drive motor control circuit 3b at the completion of 1-step scanning to stop the scanning.

Furthermore, the measurement signal generator 5a has an external synchronization signal input terminal 1.
Each time the trigger wave is input, a measurement signal whose pulse width is a predetermined phase range with respect to the trigger wave is generated. For example, when you want to collect data on both the systolic and diastolic phases of the heart, you can use two measurement signals (1) and 2 (2) as shown in Figure 3.
) to occur.

This measurement signal is used as a gate signal to output only a phase signal of the detection signal input to the gate circuit 5b to the data memory 6 (6a,). Data memory 6 (6a)
The detection position information included in the detection signal is restored and the number of arrivals of the detection signal is stored at an appropriate position in the memory space, and these become original data.

Measurement is performed in this manner, and when all steps of scanning, ie, one cycle, are completed, or when N synchronizations are completed, measurement is aborted and data collection ends.

The original data collected in this way is measured for the same amount of time at every step of the scan, that is, (pulse width of a fixed measurement signal determined in advance) x (number of scans N), so the measurement data at each step is are not missing or taken unevenly. therefore,
No factors occur that degrade the quality of the reconstructed image compared to a stationary object.

The collected original data is sent to the signal processing unit IV, where it is formatted into a predetermined signal, and then sent to the image processing unit (■) where the image is reconstructed. It is displayed on a display device such as a color monitor 19.

In addition, the reconstructed image data is stored on a floppy disk 1.
7 is stored.

[Example ■]

FIG. 4 is a block diagram showing a schematic configuration of the main parts of a positive I-ron emission CT apparatus according to Example 2 of the present invention.

The positron emission CT apparatus of this embodiment (■) has a fourth
As shown in the figure, the synchronous measurement control device 5 shown in FIG.
In addition, a cycle start timer 5c and a buffer memory 5d attached to the gate circuit 5b are added. The period measurement timer 5c receives the trigger wave from the measurement data input terminal 2, and measures the interval between two successive trigger waves. On the other hand, the buffer memory 5d temporarily stores detection signals that arrive within the measurement time of one heartbeat, and upon arrival of the next trigger signal, transfers the data to the data memory 6, and is then reset to prepare for the next measurement.

Particularly in the case of subjects with heart abnormalities, arrhythmia often occurs, resulting in an electrocardiogram that differs markedly from a normal state, and one cycle of the electrocardiogram fluctuates greatly. Arrhythmia often lasts two or more heartbeat cycles, and when an arrhythmia occurs, it is desirable to discard data measured within that cycle.

Therefore, when the output of the period subchamber timer 5C deviates from the upper or lower limit of the predetermined period, it is determined that an arrhythmia has occurred, and the information on the buffer memory 5d is reset without being transferred to the data memory 6. At the same time, the count value of the trigger wave counted by the synchronization signal register 3a is decreased by one (minus 1).
However, at this time, the judgment as to whether or not it is necessary to perform the process of decrementing by one (minus one) must always be made before the synchronization signal register 3a generates the output signal. In this way, data when an arrhythmia occurs can be removed.

[Example ■]

FIG. 5 is a block diagram showing a schematic configuration of the main parts of a positron emission CT apparatus according to Example 2 of the present invention.

The positron emission CT apparatus of this embodiment (2) has a fifth
As shown in the figure, the period measurement timer 5c in the embodiment
A heartbeat cycle storage memory 22 is added that stores and stores the output of the heartbeat, that is, the heartbeat cycle.

From the data stored in the heartbeat cycle storage memory 22 in this way, the average value of the heartbeat cycle within an appropriately determined time period is determined. This can be easily done by adding the measured cycles and dividing by the number of accumulated cycle data, and can be easily performed using a normal digital circuit. The upper and lower limits of the period of the period measurement timer are set based on the average value of the obtained heartbeat period. For example, set the upper limit to twice the average value,
The lower limit is set to 0.5 times the average value.

By resetting the upper and lower limits of the cycle of the cycle measurement timer 5c at appropriate intervals in this manner, it is possible to appropriately correct long-term fluctuations in the heartbeat of the subject.

With normal positron emission CT equipment, one scan
The number of steps included in a cycle is often about 16 or 32. In the above embodiment I, each 1-step is 1
0 Heart rate is measured by opening and stopping, scanning is 16X], 0
=160 heartbeats or 32X10=320 heartbeats to complete one cycle. Therefore, if the first half correction is performed for each scan period, a sufficient number of heartbeat data can be obtained to obtain the average value of the heartbeat cycle, and the measurement signal generator 5
If the pulse width of the measurement signal generated by a, that is, the measurement phase, is set to be proportional to the average value of the heartbeat cycle, the deviation in the measurement phase due to long-term fluctuations in heart rate can be corrected, and the measurement phase can be adjusted at each scanning step. It is advantageous to be able to make the measurement time involved equal across all steps. It goes without saying that the same effect can also be obtained by averaging the heartbeat cycle every multiple scans.

[Example ■]

FIG. 6 is a block diagram showing a schematic configuration of the main parts of a positron emission CT apparatus according to Example 2 of the present invention.

The positron emission CT apparatus of this embodiment (■) has a sixth
As shown in the figure, the scanning device i! is constructed in such a way that the time required to move the detector system part I by one step is equal to the average value of the heartbeat cycle. 30. This can be realized, for example, by replacing the drive motor 4a shown in FIG. 1 with a pulse motor 3Qa and setting the repetition frequency of the motor drive pulse current so as to be inversely proportional to the average value of the heartbeat cycle.

By setting in this way, measurement continues even during the scan, the measurement data of the systole is measured at the step of the scan start plane, and the measurement data of the diastole is measured at the step after the end of the scan.
In other words, it can be handled as a measurement in the next step, and errors in the sampling position caused by this can be kept small. A similar effect can be applied even when there are more measurement phases; for example, in the case of simultaneous four-phase measurement, the first two phases are assigned to the pre-scanning step, and the latter two phases are assigned to the post-scanning step. obtained by

In this embodiment (2), the average value of the heartbeat cycle is not actually measured, but may be a predetermined constant value. Although there is some error in the sampling position when doing this.

Sampling is done in this one step by the detector system equipment part■
This is because the error can be ignored if the unit is the movement of the position.

As can be seen from the above description, the above-mentioned Example ①.

According to n, m, rv, in a positron emission CT device, an image of a subject in a phase synchronized with an external synchronization signal of an electrocardiogram can be reproduced without any deterioration due to partial deletion of sampling. Since the data can be collected in a manner that can be configured, it is possible to provide an image without blur accompanying the movement of the moving subject's organ in each phase. This allows more advanced diagnosis to be performed.

The present invention has been specifically explained above using examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

For example, the present invention is not limited to the positron emission CT apparatus of the embodiment described above, but can be applied to all emission CT apparatuses such as X-ray CT neck wearers and scintillation cameras to which the principles of the present invention can be applied. Further, in the above embodiment, an example was explained in which an electrocardiogram was used as an external synchronization signal, but biological signals such as respiration, myoelectricity, etc. may be used as necessary.

〔Effect of the invention〕

As described above, according to the present invention, an emission CT apparatus can reconstruct an image of a subject in a phase synchronized with an external synchronization signal without any deterioration due to partial deletion of sampling. Since data can be collected at the same time, images (images) without blur caused by the movement of the moving subject organ in each phase can be obtained.
can be provided. This enables more advanced diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of the main parts of a positron emission CT apparatus according to an embodiment (2) of the present invention. FIG. 2 is a block diagram showing a schematic configuration of the entire positron emission CT apparatus according to an embodiment (2) of the present invention. Block diagram; FIG. 3 is the cardiac motion status and signal waveforms such as heart waves in the embodiment shown in FIG. 1; FIG. 4 is a schematic configuration of the main parts of the positron emission CT apparatus of embodiment H of the present invention. FIG. 5 is a block diagram showing a schematic configuration of the main parts of the positron emission CT apparatus according to the embodiment (2) of the present invention, and FIG. 6 is a block diagram showing the main parts of the positron emission CT apparatus according to the embodiment (2) of the present invention. FIG. 7 is an explanatory diagram for explaining problems with the conventional positron emission CT % setting. In the figure, 1...external synchronization signal input terminal, 2...measurement data input terminal, 3...scanning control device, 4, 30...
Running: U device, 5... Synchronous measurement control device, 6... Data memory, 21... Electrocardiograph, 22... Memory for storing heartbeat cycle, 30a... pulse motor.

Claims (5)

[Claims] (1) In an emission CT device that collects data by scanning a detector system unit with a drive motor, a synchronization signal register that generates an output signal every time a predetermined number of external synchronization signals arrive; a drive motor control circuit that receives the signal and executes one step scanning; and a measurement signal generator that generates a measurement signal having a pulse width corresponding to a predetermined phase range for each of the external synchronization signals. , and a gate circuit that allows the period detection signal during which the measurement signal is generated to pass and is stored in an appropriate position in a data memory. (2) a synchronization measurement timer that measures the time interval between two consecutive external synchronization signals and generates a signal when the measured value deviates from predetermined upper and lower limit values of the time interval; A buffer memory prefixed to the data memory whose contents are cleared when a signal arrives, and similarly, when the signal arrives, the number of external synchronization signals counted in the synchronization signal register is reduced by one, and the The emission CT according to claim 1, further comprising means for suspending output to the drive motor control circuit.
Device. (3) a memory for adding and storing the time interval of the external synchronization signal which is the output of the period measurement timer; a means for calculating the average value of the time interval of the external synchronization signal from the contents of the memory; 3. The emission CT apparatus according to claim 2, further comprising means for setting upper and lower limits of the time interval of the period measurement timer in accordance with the average value. (4) The emission CT apparatus according to claim 3, further comprising means for calculating the average value of the time intervals of the external synchronization signal every at least one period of scanning. (5) Claim 1 is characterized by comprising a scanning device and a drive motor control device that complete one step of detector movement during scanning in a time close to the time interval of an external synchronization signal. emission CT device.