JPH06254072A - Mr system - Google Patents

Abstract

PURPOSE:To provide an MR system capable of changing an interval time and outputting a switching control signal of plural RF coils when a series of sampling pulses are generated from a sampling pulse generator. CONSTITUTION:When an interval time read out of a memory 65 elapses, an interval counter 61 outputs a read-out timing signal of the next data, it is repeated until a word counter 62 counts a block end instruction from the memory 65, and when a value of the word counter 62 becomes a prescribed value, this repetition is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MR apparatus for performing imaging (MRI) or spectroscopy (MRS) using the NMR (nuclear magnetic resonance) phenomenon, and is particularly used for collecting data in the MR apparatus. To improved sampling pulse generators.

[0002]

2. Description of the Related Art A conventional sampling pulse generator of an MR device is usually composed of an interval counter 61, a word counter 62 and a controller 63 as shown in FIG. The interval counter 61 is initialized with a count value corresponding to an interval (time interval), and the word counter 62 is initialized with a count value corresponding to a word (the number of sampling points). When a start signal is input to the controller 63 from the outside (mainly a timing generator that defines a pulse sequence), the controller 63 causes the interval counter 61 to start the counting operation of the clock signal, and the interval determined by the initially set count value. Sampling pulse is generated every time. The sampling pulse is counted by the word counter 62, and when the countdown from the initial value progresses to 0, the word counter 62 sends a signal to the controller 63 and the controller 6
3 terminates the operation of the interval counter 61. Thus, the preset number of sampling pulses are generated at each preset interval time.

[0003]

However, in the conventional sampling pulse generating circuit, the interval time is constant until the generation of the initially set number of sampling pulses is completed, and the interval time is changed in the middle thereof. However, there is a problem that it is not possible to deal with the non-equidistant sampling used in the echo planar method or the like.

Further, by arranging a plurality of RF coils (antenna coils) and sequentially switching the selection of the RF coils while generating sampling pulses, R
When data is to be collected in a wide area where the F coils are arranged, it is impossible for the conventional sampling pulse generation circuit to generate the RF coil selection signal. Therefore, in such a case, conventionally, the RF generator selection control must be performed by the timing generator that defines the pulse sequence, which increases the load on the timing generator and complicates the pulse sequence. It also loses flexibility.

In view of the above, the present invention is an MR equipped with a sampling pulse generator improved so that the interval time can be changed or a switching control signal for a plurality of RF coils can be issued during generation of a series of sampling pulses. The purpose is to provide a device.

[0006]

To achieve the above object, according to the present invention, a means for generating a magnetic field, a means for radiating an RF signal, a means for receiving an NMR signal, and a received NMR signal are provided. In an MR device comprising a means for A / D converting and collecting data and a sampling pulse generating means for A / D conversion, the sampling pulse generating means includes a sampling pulse generating command, an external control signal, an interval time and a block. Storage means for storing a series of data including an end instruction, means for repeating reading of the next data when the interval time read from the storage means elapses until reading of the block end instruction, and a block A means for repeating a series of data reading up to the block end instruction until a predetermined number of end instructions are counted; It has become a feature that al configuration.

[0007]

The data of one field is formed including the sampling pulse generation command, the external control signal, the interval time and the block end command, and a plurality of these are stored. The block end command indicates that a block composed of a plurality of fields has ended. When the data of one field is read, the sampling pulse and the control signal are output in accordance with the sampling pulse generation command and the external control signal included therein, and the next pulse is output after the interval time included therein. A field read operation is performed. When the block end instruction is read, the reading from the first field is repeated again, the block end instruction is counted, and when the count value reaches a predetermined number, the repetition is ended. Data of several fields can be divided into blocks by a block end command, and the repeated use of this block prevents an increase in memory usage. Since the data of each field to be stored and the reading order thereof can be arbitrarily determined, it is possible to generate a sampling pulse of an arbitrary pattern and to cope with non-equidistant sampling and the like, and to generate plural RF coils during the generation of the sampling pulse. It is also possible to output a control signal such as a signal for switching.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a sampling pulse generator according to an embodiment of the present invention. As shown in this figure, an interval counter 61, a word counter 62 and a controller 63 are the same as in FIG. Further, it is provided with an address counter 64 and a memory 65. The count value of the interval counter 61 is initialized by the interval time information from the memory 65. The word counter 62 counts the block end command stored in the memory 65 and counts down from the initial value. The memory 65 stores information on these interval times, a block end command, and an RF coil selection code for each address, and is read by the address generated by the address counter 64.

The sampling pulse generator shown in FIG. 1 is incorporated in an MRI apparatus as shown in FIG. 2, for example. In FIG. 2, the sampling pulse generator is numbered 24. In FIG. 2, the main magnet 1
Reference numeral 1 is for generating a static magnetic field, and a gradient magnetic field is applied by a gradient magnetic field coil 12 so as to be superposed on the static magnetic field. The gradient magnetic field coil 12 has gradient magnetic fields Gx, Gy, and Gz whose magnetic field strengths are respectively inclined in the three axis directions of X, Y, and Z.
Are arranged to occur. A subject (patient) not shown is arranged in the space to which the static magnetic field and the gradient magnetic field are applied, and the RF coil 13 is attached to the subject. In this embodiment, the RF coil 13 is formed by arranging a plurality of RF coils.

The gradient magnetic field coil 21 has a gradient magnetic field power source 21.
Are connected to each other, and electric power for generating each Gx, Gy, and Gz gradient magnetic field is supplied. This gradient magnetic field power source 21 has a waveform generator 2
The waveform signal from 2 is input to control the Gx, Gy, and Gz gradient magnetic field waveforms. An RF signal is supplied to the RF coil 13 from the RF power amplifier 33, so that the subject is irradiated with the RF signal. This RF signal is R
The RF signal generated by the F signal generator 31 is AM-modulated by the modulator 32 in accordance with the waveform sent from the waveform generator 22.

The NMR signal generated by the subject is received by the RF coil 13, passes through the preamplifier 41, and the switch 44.
Sent to. The switch 44 is controlled by the RF coil selection signal from the sampling pulse generator 24. The signal from the RF coil selected by the switch 44 is sent to the phase detector 42. In the phase detector 42, the received signal is phase-detected using the RF signal from the RF signal generator 31 as a reference signal, and the detection output is sent to the A / D converter 43. A sampling pulse is input to the A / D converter 43 from the sampling pulse generator 24, and the detection output is converted into digital data according to the sampling pulse. The digital data is taken into the host computer 51.

The host computer 51 processes the captured data to reconstruct an image, and determines the timing of the entire sequence via the timing generator 23. That is, the timing generator 23 sends a timing signal to the waveform generator 22, the RF signal generator 31, the sampling pulse generator 24, etc. under the control of the host computer 51, and each waveform signal is output from the waveform generator 22. RF signal generator 3
The RF signal generation timing from 1 is determined, and the sampling pulse generation start timing from the sampling pulse generator 24 is determined. Also, the host computer 5
1 sends the waveform information to the waveform generator 22, and Gx, Gy,
The waveform, intensity, etc. of each gradient magnetic field pulse of Gz are controlled, the envelope of the RF signal irradiated to the subject from the RF coil 13 is determined, and a signal is sent to the RF signal generator 31 to determine the frequency and phase of the RF signal. Control.

The sampling pulse generator 24 is supplied from the host computer 51 with an instruction for selecting a sampling pulse of a desired pattern and a signal for setting the number of sampling pulses. The instruction to select the sampling pulse of the desired pattern is set in the address counter 64 of the sampling pulse generator 24 as an initial value. Depending on the signal that sets the number of sampling pulses, the word counter 62
The initial settings for are made.

Data having the structure shown in FIG. 3 is sequentially stored in the memory 65 as shown in FIG. 4 so that sampling pulses having a predetermined pattern are shown. Since the data of a plurality of blocks as shown in FIG. 4 are stored at different addresses, a desired pattern is selected from the plurality of patterns stored in the memory 65 by designating the start address and reading them sequentially. , A sampling pulse according to the pattern can be output.

In the data structure shown in FIG. 3, the RF coil selection codes S1 to S8, the sampling pulse generation command SPL, the block end command END, and the interval time part are 1 Field data is configured. Such data is shown in Figure 4.
As shown in FIG. Although only the set data is shown in FIG. 4, the RF coil selection code of S1 and the information indicating the interval time ta are stored in the head address, and the sampling pulse generation command SPL and the interval time are stored in the next address. The information indicating tb is stored, the RF coil selection code of S2 and the information indicating the interval time ta are stored in the third address, and the sampling pulse generation instruction SPL and the block end instruction are stored in the fourth address. END and information indicating the interval time tc are stored. From the start address to the address including this END are blocked.

After the head address of the data block shown in FIG. 4 is given from the host computer 51 to the controller 63, when the start signal is given from the timing generator 23 to the controller 63, the controller 63 is sent.
Sets the leading address in the address counter 64 as an initial value. As a result, the address counter 64 first sends the value to the memory 65 as an address. Memory 65
4 reads out the data shown in FIG. 4 and the RF coil selection code is S1.
The coil selection signal is sent to the switch 44, and the information indicating the interval time ta is read.

This interval time ta is set in the interval counter 61 as an initial value. The interval counter 61 counts the clock signal and starts counting down from the set initial value, and when it reaches 0, generates a signal to the controller 63. Then, the controller 63 increments by one from the initial value of the address counter 64. Therefore, the second data from the top of FIG. 4 stored in the next address of the memory 65 is read. Since the second data contains SPL, a sampling pulse is generated. Therefore, as shown in FIG. 5, a sampling pulse is generated after a time ta after the RF coil selection signal corresponding to S1 is issued. Since S3 is included in the third data, the RF coil selection signal corresponding to S2 is output, but the interval time is tb in the second data.
Therefore, as shown in FIG. 5, this RF coil selection signal is output after the time tb from the generation of the sampling pulse.

Next, the fourth data is read and SP
Although the sampling pulse is output corresponding to L, the interval time is ta in the third data, so as shown in FIG. 5, the time interval between the RF coil selection signal corresponding to S2 and the sampling pulse. Becomes ta.
Block end instruction END included in this fourth data
Is sent to the word counter 62 to count it down. Since the number of sampling pulses is set as an initial value in the word counter 62 from the host computer 51 via the controller 63, the word counter 62 is counted down by 1 from the initial value. Further, since the interval time is tc in the fourth data, a signal is output from the interval counter 61 to the controller 63 when the time tc has elapsed since the sampling pulse was generated. The controller 63 identifies that the word counter 62 has performed the counting operation by END, and returns the address counter 64 to the initial value at the timing of the signal from the interval counter 61.

Therefore, the reading from the beginning of the block shown in FIG. 4 again starts, and the cycle starting from the RF coil selection signal output corresponding to S1 is repeated as shown in FIG. In this way, the repeating cycle having time (2ta + tb + tc) as one cycle is sequentially performed as # 1, # 2, # 3 ,. ta is the time from the selection of the RF coil to the generation of the sampling pulse, which is the time from the switching of the switching unit 44 to the stabilization thereof. Similarly, tb is the time until the switch 44 is switched after the sampling pulse is generated. The sampling period is a sampling interval when attention is paid to a specific RF coil, and in this case, the sampling period is (2ta + tb + tc). tc is for adjusting this sampling period to a desired value.

As described above, the number of sampling points for one RF coil is set in the word counter 62 as an initial value, and since it is counted down each time END is read, only the set number of sampling points (for example, 256) is set. The above operation cycle is repeated. As a result, for example, 256 points of data are collected for each RF coil.

As described above, the data defining one of the repetition periods is divided into blocks and stored in the memory 65, and this block is repeatedly read out. Therefore, it is not necessary to store the data of all sampling points in the memory 65. As a result, the usage amount of the memory 65 can be reduced, and the preprocessing time for storing the data becomes very short.

FIG. 6 shows the contents stored in the memory 65 when non-uniform sampling is performed. In this Figure 6, RF
The coil selection code is omitted, and only the sampling pulse generation command SPL and the interval time are shown. In this case, the initial setting value of the word counter 62 is set to 1, and different interval times t1, t2, t3, ... Are stored for each sampling pulse for all sampling pulses. The sampling pulse is
The interval time t1 read as shown in FIG.
.. are sequentially generated while sequentially placing t2, t3, .... Although the use efficiency of the memory 65 is deteriorated, since the interval time can be completely determined for each sampling pulse, a completely free sampling interval can be realized.

The data structure shown in FIG. 3 is an example, and external data such as the RF coil selection code and the sampling pulse generation command are not limited to these, and additions and changes can be made.

[0024]

According to the sampling pulse generator of the MR device of the present invention, the RF is generated when the sampling pulse is generated.
It is possible to control the operation of switching the coils, avoid burdening the timing generator and the like, and avoid complicating the pulse sequence specified for the timing generator and the like. Furthermore, the degree of freedom of the sampling interval is extremely large, and it is possible to cope with any non-uniform interval sampling.

[Brief description of drawings]

FIG. 1 is a block diagram of a sampling pulse generator of an MR device according to an embodiment of the present invention.

FIG. 2 is an overall block diagram of the MRI apparatus of the same embodiment.

FIG. 3 is a diagram showing a structure of data stored in a memory of the embodiment.

FIG. 4 is a diagram showing an example of a data block stored in a memory of the same embodiment.

5 is a time chart showing the output timing in the case of FIG.

FIG. 6 is a diagram showing another example of a data block stored in the memory of the same embodiment.

7 is a time chart showing the output timing of FIG.

FIG. 8 is a block diagram of a sampling pulse generator of a conventional MR device.

[Explanation of symbols]

 11 main magnet 12 gradient magnetic field coil 13 RF coil 21 gradient magnetic field power supply 22 waveform generator 23 timing generator 24 sampling pulse generator 31 RF signal generator 32 modulator 33 RF power amplifier 41 preamplifier 42 phase detector 43 A / D conversion Device 44 Switching device 51 Host computer 61 Interval counter 62 Word counter 63 Controller 64 Address counter 65 Memory

Claims (1)

[Claims] 1. A means for generating a magnetic field, a means for irradiating an RF signal, a means for receiving an NMR signal, and a received N signal.
Means for A / D converting the MR signal to collect data;
And sampling pulse generating means for D / D conversion,
The sampling pulse generation means is a storage means in which a series of data including a sampling pulse generation command, an external control signal, an interval time and a block end command are stored, and when the interval time read from the storage means has elapsed. And a means for repeating the reading of the next data until the reading of the block end instruction, and a means for repeating a series of data reading up to the block end instruction until a predetermined number of block end instructions are counted. MR device.