JPH0966041A - Nuclear magnetic resonance inspection instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an electrocardiographic synchronism pulse sequence with TR automatically set in relation with a pulse only by inputting desired contrast. SOLUTION: A computer 51 monitors the output of an electro-cardiographic sensor 13, finds an electrocardiographic cycle and finds the TR required for the separately inputted desired contrast. Further, among cycles satisfying the condition that the interger multiple of the electrocardiographic cycle exceeds the TR, the shortest cycle is found by the computer 51, and the electrocardiographic synchronism pulse substantially matched with this cycle is extracted and defined as a trigger signal for starting the pulse sequence.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear magnetic resonance examination apparatus for performing imaging or spectroscopy measurement by utilizing a nuclear magnetic resonance phenomenon (MR phenomenon), and particularly to measurement in synchronization with the motion of the heart of a subject. The present invention relates to a nuclear magnetic resonance inspection apparatus.

[0002]

2. Description of the Related Art Conventionally, in a nuclear magnetic resonance examination apparatus, a measurement pulse sequence is performed in synchronization with the motion of the heart of a subject to collect data (electrocardiographic synchronized imaging method). In this case, in order to obtain a desired T2-weighted image, it is necessary to lengthen TR (repetition time), that is, the pulse sequence is synchronized with several heartbeats instead of being synchronized with each heartbeat. Must be set to start. For example, when TR = 3 (seconds) is required to obtain a desired T2-weighted image and when an electrocardiographic gated imaging is performed on a subject whose heart rate (per minute) is 60. The pulse sequence will be set to start every three heartbeats.

This setting is actually performed as follows. Required TR for subjects with heart rate of 60
Since the time of is about 3 heartbeats, TR: [Heart Ra] is calculated based on the calculation of 60 (heartbeat) / 3 (heartbeat) = 20.
te 20]. When such a setting is made, the same electrocardiographic synchronized imaging as when the subject's heart rate per minute is 20 is performed. In other words, the trigger signal obtained from the electrocardiographic waveform (occurs once per heartbeat, so in this case 60 times per minute)
1 as if it occurred every 0 minutes (3 seconds)
Only those that occur before and after the / 20 minute interval are taken, which triggers the pulse sequence.

[0004]

However, when the TR is set in association with the heartbeat as in the conventional case, the heartbeat rate which is different for each subject is actually measured, and the one heartbeat period becomes several seconds. Is calculated, and the number of heartbeats that are longer than TR that can obtain a desired contrast is calculated, and it must be set, which is very troublesome.

In view of the above, the present invention has improved the nuclear magnetic field so that the TR associated with the heartbeat is automatically set and the electrocardiographic synchronization pulse sequence is performed only by inputting the desired contrast. An object is to provide a resonance inspection device.

[0006]

To achieve the above object, in a nuclear magnetic resonance examination apparatus according to the present invention, means for generating a static magnetic field and means for generating a gradient magnetic field so as to be superposed on the static magnetic field. An RF transmitting means, an RF receiving means, a means for controlling these to perform a measurement pulse sequence, a means for inputting a desired contrast, a means for obtaining TR according to the contrast, and an electrocardiographic measuring means. , A means for obtaining an electrocardiographic synchronization pulse corresponding to a predetermined time phase of the measured electrocardiographic signal, and a period which is an integral multiple of the measured electrocardiographic period and which exceeds the above-obtained TR And a means for extracting the electrocardiographic synchronization pulse that substantially matches this cycle as a trigger signal of the measurement pulse sequence. There.

When the desired contrast is input, the TR required for it is obtained. On the other hand, the electrocardiographic signal is measured and the electrocardiographic synchronization pulse corresponding to the predetermined time phase is obtained.
Therefore, a cycle obtained by multiplying the electrocardiographic cycle by an integer is considered, and the shortest one is obtained from those satisfying the condition that this cycle exceeds TR. An electrocardiographic synchronization pulse that substantially matches this cycle is extracted from the electrocardiographic synchronization pulse. If the extracted electrocardiographic synchronization pulse is used as a trigger signal for starting the measurement pulse sequence, it is possible to automatically synchronize the measurement pulse sequence with the electrocardiographic signal while ensuring the required TR.

[0008]

Next, embodiments of the present invention will be described in detail with reference to the drawings. A nuclear magnetic resonance inspection apparatus according to the present invention is configured as shown in FIG. In FIG. 1, the magnet assembly 11 includes a main magnet for generating a static magnetic field, and a gradient coil for generating gradient magnetic fields Gx, Gy, Gz superimposed on the static magnetic field. A subject 61 placed on an examination table 62 is inserted into the space to which the static magnetic field and the gradient magnetic field are applied. The subject 61 is irradiated with an RF pulse and the NM generated by the subject 61 is emitted.
An RF coil 12 for receiving the R signal is attached. Further, an electrocardiographic sensor 13 for measuring an electrocardiographic waveform is attached to the subject 61.

A magnetic field control circuit 21 is provided as a circuit for supplying a gradient magnetic field current to the gradient coil of the magnet assembly 11. A waveform signal from the waveform generation circuit 53 is sent to the magnetic field control circuit 21. In the waveform generating circuit 53, information on each pulse waveform of the gradient magnetic fields Gx, Gy, Gz is set in advance from the computer 51. A waveform signal is generated from the waveform generation circuit 53 at a timing instructed by the sequence controller 52 and is sent to the magnetic field control circuit 21 to generate gradient magnetic fields Gx, Gy, and Gz each having a pulse of a predetermined waveform. become.

The RF signal generated by the RF oscillation circuit 31 is sent to the amplitude modulation circuit 32, which becomes a carrier signal,
Amplitude modulation is performed according to the waveform signal sent from the waveform generation circuit 53. The RF signal after the amplitude modulation is amplified through the RF power amplifier 33 and then applied to the RF coil 12. The oscillation frequency of the RF oscillation circuit 31 is controlled by the computer 51. Information on the waveform of the modulation signal is given from the computer 51 to the waveform generation circuit 53 in advance. The timing of the waveform generation circuit 53 and the RF oscillation circuit 31 is determined by the sequence controller 52.

NMR received by RF coil 12
The signal is sent to a phase detection circuit 42 via a preamplifier 41 and is subjected to phase detection. The RF signal from the RF oscillation circuit 31 is sent as a reference signal for this phase detection. The signal obtained by the phase detection is sampled at a predetermined sampling timing by the A / D converter 43 controlled by the sequence controller 52 and converted into digital data. The data obtained from the A / D converter 43 is taken into the computer 51, and an image is reconstructed from the collected digital data.

This computer 51 has a console 5
4, a keyboard 55 and a mouse 56 are connected. The keyboard 55, the mouse 56, etc. are used to input an imaging sequence, imaging parameters, and the like. The computer 51 includes the electrocardiographic sensor 13 described above.
Is input, and the electrocardiographic waveform is displayed and monitored on the display device of the console 54.

The imaging sequence is designated by operating the keyboard 55, the mouse 56, etc.
When the contrast is input, the computer 51 calculates the TR required to obtain the T2 contrast. T
The relationship between R and T2 contrast is as shown in FIG. 2, and the computer 51 uses this relationship to obtain the required TR.
(This will be referred to as TRx).

From the electrocardiographic waveform taken from the electrocardiographic sensor 13 into the computer 51, an electrocardiographic synchronizing pulse is generated as shown in FIG. This ECG sync pulse is
It is designed to generate at the timing by capturing the R wave of the electrocardiographic waveform. The average value of the pulse interval (cycle of one heartbeat) a of this electrocardiographic synchronization pulse is obtained, and n is a positive integer, and a is multiplied by n. A short (smallest n) a · n is sought. a · n ≧ TRx Then, the period a ·
Those with a period that substantially matches n are retrieved.

Here, “substantially” means that a slight deviation is allowed, and for example, a deviation of about 15% with respect to the cycle a · n is allowed. That is, as shown in FIG. 3, a pulse selection gate signal having a pulse width of 15% of a · n is created, and the electrocardiographic synchronization pulse is gated by this pulse selection gate signal as shown in FIG. An electrocardiographic synchronization pulse having a cycle substantially matching a · n is extracted. The extracted electrocardiographic sync pulse is used as a trigger signal for starting the imaging sequence.

Note that such signal processing can of course be performed by hardware such as a pulse waveform generating circuit and a gate circuit, but here it is performed by software in the computer 51. Further, the operation of extracting an electrocardiographic synchronization pulse that substantially agrees with the cycle a · n after allowing a slight deviation has been described above by the pulse selection gate signal or the concept of gating with the pulse selection gate signal. Is for the sake of clarity and need not be limited to these concepts.

[0017]

As described above, according to the nuclear magnetic resonance examination apparatus of the present invention, the TR in units of the electrocardiographic cycle is automatically set according to the desired contrast, and the measurement pulse sequence is It is performed in synchronization with the electrocardiographic signal for each TR. Therefore, the operator does not need to perform the operation of obtaining the heartbeat cycle for each subject or setting TR based on the heartbeat cycle by presetting the desired contrast. Therefore, with a very simple operation, it is possible to obtain images with stable contrast for subjects having different heart rates.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a nuclear magnetic resonance inspection apparatus according to the present invention.

FIG. 2 is a graph showing the relationship between TR and T2 contrast.

FIG. 3 is a waveform diagram for explaining the operation.

FIG. 4 is a conceptual diagram for explaining an operation.

[Explanation of symbols]

 Reference Signs List 11 magnet assembly 12 RF coil 13 electrocardiographic sensor 21 magnetic field control circuit 31 RF oscillation circuit 32 amplitude modulation circuit 33 RF power amplifier 41 preamplifier 42 phase detection circuit 43 A / D converter 51 computer 52 sequence controller 53 waveform generation circuit 54 Console 55 Keyboard 56 Mouse 61 Subject 62 Examination table

Claims (1)

[Claims] 1. A means for generating a static magnetic field, a means for generating a gradient magnetic field so as to be superimposed on the static magnetic field, an RF transmitting means, an RF receiving means, and means for controlling them to perform a measurement pulse sequence. A means for inputting a desired contrast, a means for obtaining TR according to the contrast, an electrocardiographic measuring means, and means for obtaining an electrocardiographic synchronization pulse according to a predetermined time phase of the measured electrocardiographic signal, It is a cycle obtained by multiplying the measured electrocardiographic cycle by an integer, and the shortest cycle among those satisfying the condition that the calculated TR is exceeded is obtained, and the electrocardiographic synchronization pulse substantially matching the cycle is obtained. A means for taking out as a trigger signal of the measurement pulse sequence, a nuclear magnetic resonance examination apparatus.