JPS6185932A - Nuclear magnetic resonance imaging system corresponding to arrhythmia - 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 [Field of Application of the Invention] The present invention relates to an imaging method that uses nuclear magnetic resonance to obtain moving images of the heart, and in particular to an imaging method that uses nuclear magnetic resonance to obtain moving images of the heart, and in particular, to obtain a moving image of the heart at high speed and with a high S/N ratio without depending on the presence or absence of arrhythmia. The present invention relates to an imaging method for obtaining dynamic images.

[Background of the invention]

Conventionally, when imaging the heart with an imaging device that uses nuclear magnetic resonance, images of a specific state of the heart are obtained by measuring the nuclear magnetic resonance signals necessary for image reconstruction in synchronization with the electrocardiogram waveform. Ta. In such an imaging device, the necessary data is 1
Since the number of signals is very high (approximately 80 to 256), each signal measurement requires waiting time of at least one cycle of the heartbeat, so it takes a lot of time to obtain the series of data necessary for image reconstruction. Was. Furthermore, if the measurement signals were to be averaged to improve the S/N of the reconstructed image, it would take several times as much time, which would cause great pain to the subject. Furthermore, if an arrhythmia is included in the electrocardiogram, it is expected that the No. 48 signal from the magnetocardiogram will be measured in a state different from the original state, which will cause deterioration of the reconstructed image.

Furthermore, since a trigger signal for starting signal measurement is required, special processing and equipment such as differentiation of the electrocardiogram waveform and generation of the trigger signal are required.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an imaging method that obtains dynamic images of the heart at high speed and with a high S/N ratio, regardless of the presence or absence of arrhythmia.

[Summary of the invention]

Therefore, in the present invention, one image is converted into one cycle of heartbeat (
The heart can be imaged continuously at arbitrary timing using a high-speed imaging method that can take images in a sufficiently short time compared to 0.8 seconds (approximately 0.8 seconds).
i (hereinafter referred to as phase) is estimated. Then, the S/N ratio of the image in each phase is improved by taking a countable average of a set of images included in the same phase as the divided phases. The imaging time for one image is sufficiently small compared to one cycle of the heartbeat, so even if the number of times of image addition and averaging in each phase is increased, it is still possible to achieve high S in a sufficiently short time compared to the projection reconstruction method or the two-dimensional Fourier transform method. /N ratio images can be obtained, and even if the heart to be imaged has arrhythmia, the ig
9 will never deteriorate. A dynamic image of the heart can be obtained by arranging the images of the heart for each phase obtained in this manner in the order of temporal change in phase.

Further, according to the present invention, since imaging is performed at an arbitrary timing, a trigger signal for starting imaging is not required.

Therefore, there is no need for any particular processing or device for generating a redrigger signal that differentiates an electrocardiogram waveform. This also requires that there be no characteristic changes in the electrocardiogram waveform to determine when to generate the trigger signal.

Therefore, with the method according to the present invention, it is possible to image a heart having any electrocardiographic waveform.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an NMR imaging apparatus used in practicing the present invention. The object to be imaged is always exposed to a uniform and stable magnetic field generated by the static magnetic field coil 1.

The static magnetic field power supply 2 is for supplying power to the static magnetic field coil. G.

Gradient magnetic field coils 3, G, gradient magnetic field coils 4, and G8 gradient magnetic field coils 5 select slices of the object to be imaged.

In order to store positional information within the imaged object, gradient magnetic fields in the spatial X-axis, y-axis, and Z-axis directions are generated. The gradient magnetic field power supply 6 is for supplying power to these gradient magnetic field coils. The high-frequency magnetic field irradiation coil 7 is used to excite nuclear spins in the object to be imaged, and the high-frequency magnetic field pulse irradiated from this coil is given a signal by the central processing bag w13 and sent to the A/D converter 14. A
After being subjected to /D conversion, the signal is amplified to an appropriate amplitude by an amplifier 9. The nuclear magnetic resonance signal generated when the excited nuclear spins undergo free induction decay motion is detected by the signal detection probe 8, amplified to an appropriate amplitude by the amplifier 10, and further A/D converted by the A/D converter 14. After being converted into D, it is taken into the central processing bag W13 and subjected to various processing. A timing sequencer 11 controls the timing of applying each gradient magnetic field, the timing of irradiating a high-frequency magnetic field, and the timing of detecting a nuclear magnetic resonance signal, and this is further controlled by a central processing unit 13.

In addition to the timing sequencer 11, the central processing unit 13 generates the above-mentioned high-frequency magnetic field pulse signal, performs various processing on sampled nuclear magnetic resonance signals, reconstructs images, monitors electrocardiographic waveforms, and the like. The display 12 is used to display the image reconstructed by the central processing unit and its lot number type information. The electrocardiograph 15 is used to know the timing at which the heart is imaged, and the timing information is input to the central processing unit 13.

In this embodiment, the phases of the heart to be imaged are divided in advance, and the images are continuously captured at arbitrary timings, and at the same time, images included in the same phase as the wt-transformed image are sequentially added. After all imaging is completed, images are averaged according to the number of times images are added for each phase.

FIG. 2 is a diagram showing the flow of procedures when implementing the present invention. In the embodiment of the present invention, a case will be explained in which the echo Plechie method is used as a high-speed imaging method.
It is possible to capture an image in about 30 seconds.

In step 2-1, one cycle of an electrocardiogram waveform obtained from the heart to be imaged by the electrocardiograph 15 is divided into, for example, five phases as shown in FIG.

Let these divided phases be 4th digit 1, phase 2, . . . phase 5.

In step 2-2, the heart is imaged at an arbitrary timing using the echo prechi method, and the electrocardiograph 15 checks whether the imaged timing belongs to phase 1 to phase 5.
The determination is made by interpreting information about the timing of imaging inputted to the central processing unit from . For example, in FIG. 3, timing t belongs to phase 5.

In step 2-3, the image taken in step 2-2 is added to the already taken images of the same phase.

By repeating steps 2-2 and 2-3 N times, the N captured images are classified into phases from phase 1 to phase 5, and images are added for each phase. In Fig. 3, images captured at timing t1 are countably averaged to form an image with phase 5, and similarly, images taken at timings 2, t7, and t are countably averaged, and each phase is 31 phase 1 image. The image captured at timing t4 becomes an image of phase 4 as it is.

In step 2-4, the added images are averaged by the number of additions for each phase. By averaging the images for each phase in steps 2-2 and 2-4 above, the S/N ratio of the obtained image is improved.

In step 2-5, the images for each phase obtained as described above are arranged in the order of the time course of the phases and displayed on the display 12.
A dynamic image of the heart is obtained by displaying the images in sequence or by sequentially displaying the images in sequence in the order of the time course of the phase.

In another embodiment of the present invention, images of the heart were continuously performed at arbitrary timings, and images were taken for each machine image. The images and the timing at which they were captured are stored, and after all imaging is completed, the captured images are classified into each position and the images are averaged for each phase. FIG. 4 shows the flow of procedures for implementing this embodiment.

In step 4-1, the heart is imaged at any timing using the echobreech method, and at the same time, the electrocardiograph 15
The timing of imaging is determined based on the electrocardiogram waveform inputted to the central processing unit 13 from the CPU 13.

In step 4-2, both the image captured in step 4-1 and information regarding the determined timing of imaging are stored in a storage medium attached to the central processing unit I\13.

By repeating step 4-1 and step 4-2 N times, the storage medium stores N images each captured at an arbitrary timing and information regarding the timing at which the image was captured.

In step 4-3, one cycle of the electrocardiographic waveform obtained from the heart to be imaged through the electrocardiograph 15 is divided into m phases, and each phase is phase 19, phase 2, . . . phase m, and m phases.・In step 4-4, step 4-1 and step 4-2
N images taken at arbitrary timings and stored in the storage medium are also stored. Based on the information about the timing of imaging, the images are classified into m divided phases in step 4-3. Then, a set of images in each phase classified into the same phase is added and averaged. This averaging improves the S/N ratio of the image at each phase.

In step 4-5, the images for each phase obtained as described above are arranged in order of the time course of the phases and displayed on the display 1.
A dynamic image of the heart can be obtained by displaying the images on the display 12 or by displaying the images on the display 12 by sequentially interchanging the images in the order of the time course of the phase.

According to this embodiment, all information regarding captured images and timing of imaging is stored, and steps 4-3 to 4-5 can be repeated for various phase divisions.

In yet another embodiment of the present invention, especially when the heart to be imaged has an arrhythmia, both a dynamic image of the heart during the arrhythmia interval and a dynamic image of the heart during the arrhythmia interval are simultaneously obtained. be.

FIG. 6 is a diagram showing the flow of procedures when implementing this embodiment. In step 4-3', the electrocardiogram waveform obtained from the heart to be imaged through the electrocardiograph 15 is classified into those in the arrhythmia interval and those in the arrhythmia interval, as shown in FIG. One period of the electrocardiogram waveform in the section is n pieces,
Split into two phases. In the example of FIG. 5, one cycle of the electrocardiographic waveform in the arrhythmia section is divided into five phases, and one cycle of the electrocardiographic waveform in the arrhythmia section is divided into four phases.

In step 4-4', as shown in FIG. . Based on the information about the timing of the imaging, the phases are divided into n phases in the divided arrhythmia section and two phases in the arrhythmia section divided in step 4-3'. In the example shown in Figure 5, the imaging timing is as follows. From tl3, tl, garat's,
tl. The images taken from t to 9 are classified as images of the arrhythmia interval into one of phases 1 to 5.

Also, from timing t13 to 4, from tl7, and so on.

The captured image is divided into any one of phases 6 to 9 as images of the arrhythmia section. Then, a set of images in each phase classified into the same phase is added and averaged. This averaging improves the S/N ratio of the image at each phase.

In step 4-5', the images for each phase obtained as described above are displayed on the display 12 by arranging the images in the arrhythmia interval and the images in the arrhythmia interval independently in the order of time elapsed, or By sequentially replacing the images in the order of time and displaying them on the display 12, dynamic images in the arrhythmia section and dynamic images in the arrhythmia section of the heart are independently obtained.

〔Effect of the invention〕

According to the present invention, moving objects other than the heart, such as the stomach, lungs, blood vessels, etc., can be imaged at high speed and with a high S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the apparatus used to carry out the present invention;
FIG. 2 is a diagram showing the quick flow of implementing the present invention;
FIG. 3 is performed during the implementation of the present invention. FIG. 4 is a diagram showing the classification of imaging timing into each phase of an electrocardiographic waveform; FIG. 4 is a diagram showing a quick flow when implementing another embodiment of the present invention;
FIG. 5 shows the steps taken in carrying out another embodiment of the invention.
A diagram showing the classification of each phase edge of the electrocardiographic waveform at the imaging timing especially when the heart of the object to be imaged has a suspicious pulse. FIG. 6 shows a quick flow when implementing still another embodiment of the present invention. FIG. 1... Static magnetic field coil, 2... Static magnetic field power supply, 3, 4
゜5...G, GA, G8 gradient magnetic field coil, 6...
Gradient magnetic field power source, 7...High frequency magnetic field irradiation coil, 8...
...Signal detection probe, 9.10...Amplifier, 11
... timing sequencer, 12 ... display, 13 ... central processing unit, 14 ... A/D converter,
15... Electrocardiogram 2nd (2) 3rd port

Claims (1)

[Claims] 1. A nuclear magnetic resonance imaging apparatus having a static magnetic field, a gradient magnetic field, a high-frequency magnetic field generator, a nuclear magnetic resonance signal receiving probe, a central processing unit, and an electrocardiograph, which continuously images the heart. The electrocardiogram waveform is measured together with the electrocardiogram, the electrocardiogram is analyzed to estimate what state of the heart the imaged heart image is in, and the sets of images included in the same state are averaged. A nuclear magnetic resonance imaging method for arrhythmia that is characterized by obtaining dynamic images of the heart by arranging images corresponding to temporal changes in the state of the heart. 2. The state of the heart is estimated by using a device that detects changes in the velocity of blood vessels in blood vessels or changes in blood pressure instead of the electrocardiograph, as described in claim 1. magnetic resonance imaging method for arrhythmia.