JPS60241429A - Nmr image data collection method - 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 NMR image data collection method suitable for collecting data for tomographic imaging of the heart in an NMR-CT rack apparatus.

[Background of the invention]

NMR comprising a static magnetic field generation means, a gradient magnetic field generation means, an electromagnetic wave irradiation means, and a control means for the gradient magnetic field.
- CT rack device Gating method is generally used to take tomographic images of the heart, but since the R wave-R wave interval of the electrocardiogram waveform is not constant6, the R wave-R wave after a certain time elapses from the R wave. Even when attempting to obtain intermediate tomographic images, the size of the heart at each time of data collection is not necessarily the same. For this reason, data on hearts of different sizes is collected, and a reconstructed image (tomogram) is created.
has become unclear.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances,
It is an object of the present invention to provide an NMR image data collection method that can obtain clear tomographic images of the heart.

[Summary of the invention]

The present invention provides a method for collecting NMR image data for cardiac tomography using an NMR-CT apparatus and a gate method, in which a specific gradient magnetic field is applied in advance, and the gate method is used. a reference data collection and storage means for graphically storing NMR image data of a specific cross section of the heart as reference data at a predetermined timing based on the R wave of an electrocardiogram waveform; , a reconstruction data collection means that sequentially controls the gradient magnetic field and collects the data for reconstruction at the timing of P9 feet; NMR image data is collected under the same gradient magnetic field conditions for the same cross section as at the time of collection, and when the difference between both data is less than a predetermined value when compared with the reference data, it is saved as data for reconstruction under that gradient magnetic field control state. However, when the predetermined value is exceeded, data comparison/judgment means is provided for collecting reconstruction data again in the gradient magnetic field control state, thereby obtaining a clear tomographic image of the heart.

[Embodiments of the invention]

The present invention will be described in detail below with reference to FIGS. 1 to 7. FIG. 1 is a partially cutaway perspective view showing an example of an NMR-CT apparatus to which the NMR image data acquisition method according to the present invention is applied. Coils 3 and 4 are coils for generating gradient magnetic fields, and 5 is a subject to be subjected to cardiac tomography.

In the above-described apparatus, the subject 5 is positioned in a static magnetic field generated by the coil 1. Further, the subject 5 is applied with a gradient magnetic field generated by the coils 3 and 4, and is irradiated with RF by the coil 2. In this case, the gradient direction of the gradient magnetic field and the frequency of the RF can be controlled.

In the present invention, a gating method is used in addition to the above-mentioned device, and an electrocardiographic waveform as shown in FIG. 2 is extracted from the subject 5 and used for data collection timing6.
That is, R wave 10. , 10. , 10. ...10
Time point 11 after a certain time delay 12 from n. , 11
．． , 11° . . . 11nIc Obtain control signals for the above-mentioned device and collect data.

An example of data processing from collection of NMR image data to acquisition of projection data will be outlined based on FIG. 3. Third
In the figure, it is assumed that objects 20a and 20b are located in a static magnetic field applied in a direction perpendicular to the drawing plane. To this end, a gradient magnetic field 211 is first applied, data is collected at a certain point, and, for example, the FID signal 211 of the illustrated waveform is
1 is obtained and subjected to Fourier transformation (represented by an arrow 23), graphical projection data 24 is obtained. Next, a gradient magnetic field 21 with a different inclination direction. When data is collected in the same manner as described above, for example, the FID signal 222 of the illustrated waveform is obtained.
is obtained, and by Fourier transforming this (arrow 23), illustrated projection data 242 is obtained. Thereafter, while changing the gradient direction of the gradient magnetic field, data collection and processing are repeated in the same manner as described above until the gradient magnetic field rotates 3600 times, and a large number of projection data 24. 24n is obtained, and image reconstruction is performed based on them. In the method of the present invention, the object to be imaged is a moving heart, and the size of the R wave is 10.
, 10. , 10.・10. Each time point 111, 112, 113...1 after a certain period of time (delay 12)
1n are not necessarily the same. For example, point 11.
and 114 are considered to be almost the same, or time 31
．． and I+ are considered to be different. Therefore, time 11. When the image is reconstructed using the data collected in steps 112 and 112, image blurring occurs.

Therefore, in the present invention, data of a specific cross section is collected in advance as reference data at a certain point in time, and the gradient magnetic field is controlled. Here, the imaged cross section is reconstructed while being controlled by the gradient direction of the gradient magnetic field. Immediately after each data is collected, the judgment data collected under the same gradient magnetic field conditions on the same cross-section as the reference data collection is compared with the reference data, and only when the judgment data and the reference data are the same or similar, an image is generated. It is designed to be used for reconstruction.

In this case, the NMR-CT apparatus is capable of multi-slice measurement, and in FIG. , 22 of the heart 30 at cross-section 30. , 30 degrees as the specific cross section for collecting the reference data (hereinafter referred to as the reference cross section) and the cross section to be photographed, when data is collected from there, the cross section coordinate (position) Zl.

2, ... and the frequency ω1 of the irradiation RF. ω2・
Since the relationship between ω8 and . It is sufficient to selectively irradiate the frequency ORF of ω2.

An embodiment of the method of the present invention will be described below with reference to FIG. First, an electrocardiogram waveform (see FIG. 2) is obtained from the subject 5 set as shown in FIG. 1, and an R wave, for example a ViR wave 10.
Detect (step 1oO). After the detection, after a certain time delay 12 (step 101) has elapsed, the coils 3 and 4 are used to direct the gradient direction of the gradient magnetic field in a specific direction, for example, the horizontal direction (hereinafter referred to as the reference direction) (step 101). 102), reference cross section 30 with RF frequency as ω1
．． NMR image data (hereinafter referred to as reference data) is collected (step 103).

Collected reference data record Fourier transform (step 104
) as the reference projection data and save it as the 0th data (step 105).

Next, the R wave, for example the R wave 102, is detected again (step 106), and after 12 delays (step 107), the gradient direction of the gradient magnetic field is directed to a predetermined direction by the coils 3 and 4, and this time the RF Cross section 302 to be photographed with frequency set to ω2
NMR image data (hereinafter referred to as reconstruction data) is collected (step 108). Immediately after this, the next step 10 is to determine whether or not the collected reconstruction data should be saved.
Determine from 9 to 112. In other words, υ due to coils 3 and 4
The gradient direction of the gradient magnetic field is corrected to the reference direction (step 109), and the RF frequency is set to ω, and the reference cross section 3 is
0, NMR image data (hereinafter referred to as determination data)
are collected (step 110). The collected determination data is subjected to Fourier transformation to obtain first determination projection data (step 111), and this is compared with the 0th data (reference projection data) (step 112). As a result, if the difference between both data is greater than a predetermined value, the reconstruction data is discarded (step 113);
Returning to step 117, data for reconstruction is similarly collected without changing the gradient direction of the gradient magnetic field, and it is determined whether or not to save the data (steps 106 to 112). If it is smaller than the predetermined value, the reconstruction data is saved (step 114).

Next, the gradient direction of the gradient magnetic field is changed by the coils 3 and 4 (step 115), and steps 106 to 115 are executed again. In step 116, data collection and storage for all angles in the gradient direction of the gradient magnetic field is completed. It is determined whether or not
If not completed, return to step 117 and perform steps 106-1
Repeat for 15 gold and stop when completed.

As described above, all NMR image data (first to nth reconstruction data) necessary for tomographic image reconstruction of the cross section 302 of the heart 30 of the subject 5 are collected and saved. In this case, whether or not to save the reconstruction data is determined by collecting the judgment data immediately after the data collection and comparing it with the reference data, and only if the difference between both data is smaller than a predetermined value, It is saved as data for reconstruction in the gradient direction of the gradient magnetic field.

Therefore, the saved reconstruction data is only the reconstruction data collected when the size is the same as or approximates the specific size of the heart 30 set as reference data, and the image of the unmarked cross section 302 is It will be reconfigured.

In the above embodiment, the control of the gradient magnetic field is
This was done by controlling the gradient direction of the gradient magnetic field, but it is not limited to this only; for example, [Warp method J]
(Published in 1981) NMRIMAGING (Proc.
eedings of an International
al Symposium of NuclearMa
gnetic Re5onance Imaging
) J pages 77-80).

Figure 6 shows the RF pulse and gradient magnetic field G in the warp method.
x + Gy + Gz and NMR image data (FID
FIG. 2 is a signal waveform diagram showing a signal. In other words, the warp method is
In this method, data is collected by applying an RF pulse without applying a gradient magnetic field + Gy + GZ as shown in the figure. In this case, the amplitudes of the gradient magnetic fields Gx and Gy are fixed to constant values, but the amplitude of the gradient magnetic field G2 is changed in a predetermined order every time reconstruction data is collected, for example, broken line a+b+C...
・Change in the order of.

FIG. 7 shows an example of a flowchart of the method of the present invention when controlling a gradient magnetic field using the above-mentioned warb method. Note that in this example, fcNMR image data collected without performing Fourier transformation may be stored, compared, etc.

In the illustrated embodiment, the cross section to be photographed is the reference cross section 30,
K adjacent cross section 30. Although the case where the cross section 30. Of course, it may also be the same.

〔Effect of the invention〕

As described above, the present invention uses an NMR-CT apparatus,
NM for cardiac tomography using the gate method
In the method of collecting R image data, NMR image data of a specific cross section of the heart is collected with a specific gradient magnetic field applied in advance and at a predetermined timing based on the R wave of the electrocardiogram waveform by the gating method. a reference data collection and storage means for collecting and storing reference data; and a reconstruction data collection means for collecting NMR image data of the cross section of the heart to be imaged as reconstruction data at the predetermined timing while sequentially controlling a gradient magnetic field. Immediately after each data collection by the reconstruction data collection means, NMR image data is collected on the same cross section under the same gradient magnetic field conditions as when collecting the reference data, and compared with the reference data to determine the difference between the two data. When the value is less than a predetermined value, the data is stored as reconstruction data in the gradient magnetic field control state, and when the predetermined value is exceeded, the trap collects old configuration data again in the gradient magnetic field control state. Since the NMR image data is collected using the NMR image data, the only reconstruction data that is saved is the reconstruction data that was collected at the same or approximate size as the specific size of the heart that was set as the reference data. This has the advantage that a reconstructed image (tomographic image) of the heart can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an example of an NMR-CT apparatus to which the NMR image data acquisition method according to the present invention is applied;
Figure 2 is a diagram showing an example of an electrocardiogram waveform, and Figure 3 is a diagram showing an example of an electrocardiogram waveform.
A schematic explanatory diagram of an example of data processing from collecting i-image data to obtaining projection data; Fig. 4 is a graph showing the relationship between the cross-sectional coordinates at which data is collected in the NMR-CT apparatus and the frequency of irradiation RF; Fig. 5 is a flowchart for explaining one example of the operation of the apparatus shown in FIG. 1, and FIGS. 6 and 7 are signal waveform diagrams and flowcharts for similarly explaining other examples. DESCRIPTION OF SYMBOLS 1... Static magnetic field generation coil, 2... RF irradiation coil, 3, 4... Gradient magnetic field generation coil, 5... Subject, 10, to 104... R wave, 12. ...Delay,
21. , 212... gradient magnetic field, 22. , 222・
...FID signal, 24□, 242...Projection data, 3
0: Heart, 301: Reference cross section, 302: Cross section to be photographed. Patent Applicant Hitachi Medeico Co., Ltd. Agent Patent Attorney Tadashi Akimoto Figure 7 TS2 Figure 3 Figure 4 Section

Claims (1)

[Claims] NMR comprising a static magnetic field generation means, a gradient magnetic field generation means, an electromagnetic wave irradiation means, and a control means for the gradient magnetic field.
- A method of collecting NMR image data for tomography of the heart using a CT rack and a gate method, in which an electrocardiographic waveform is collected by applying a specific gradient magnetic field in advance and using the gate method. a reference data collection and storage means for collecting and storing NMR image data of a specific cross section of the heart as reference data at a predetermined timing based on the R wave; and a gradient magnetic field is sequentially applied to the NMR image data of the target cross section of the heart. Reconstruction data collection means for collecting data as reconstruction data at the predetermined timing while controlling;
Immediately after collecting each data by the reconstruction data collecting means, NMR image data is collected on the same cross section under the same gradient magnetic field conditions as when collecting the reference data, and compared with the reference data, the difference between both data is determined by a predetermined value. and a data comparison/judgment means for storing data for reconstruction in the gradient magnetic field control state when the value is less than the predetermined value, and collecting data for reconstruction again in the gradient magnetic field control state when the predetermined value is exceeded. NMR image data collection method with special mission.