JPS59169208A - Waveform generator for nmr device - Google Patents

Abstract

PURPOSE:To obtain a waveform generator for NMR (nuclear magnetic resonance) device with which a high-speed control is possible and the control sequence or analog waveform can be simply changed, by using plural waveform memories and writing and reading control circuits. CONSTITUTION:A writing control circuit 21 writes the data given from a computer to waveform memories 22, 25, 28, 31, 34, 36 and 38 respectively. That is, the grade magnetic field signals (x), (y) and (z) and the waveform data on modulated signals are written to the memories 22, 25, 28 and 31. While the data on the control circuit for transmitting circuit, i.e. an A/D conversion signal, the control signal for transmitting gate, and the control signal for receiving gate are written to the memories 34, 36 and 38 respectively. A reading control circuit 41 reads out the contents of said waveform memories. In such a constitution, a high-speed control is possible and at the same time the control sequence or the analog waveform can be simply changed. Thus such a highly flexible waveform generator is obtained for NMR device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to nuclear magnetic resonance (nuclear magnetic resonance).
This invention relates to an improvement of a waveform generator in an NMR apparatus that uses the phenomenon of ic-resonance (hereinafter abbreviated as NMRJ) to know the distribution of specific atomic nuclei within a subject from outside the subject.

C. Prior Art] NMR is a method of obtaining chemical information using the magnetic properties of atomic nuclei. In other words, when an atomic nucleus in a static magnetic field is excited with high-frequency energy, the density of the atom and its bonding state with the magnetic field can be determined from the resonance signal (hereinafter referred to as an NMR signal) generated by the resonance phenomenon. NMR devices using this principle have recently attracted attention as diagnostic devices that provide anatomical and functional information.

In an imaging device using the NMR phenomenon as described above, it is necessary to generate various analog signal waveforms and digital signals in order to observe an object. For example, analog signal waveform and 1
Examples include x, y, and z gradient magnetic field signals for associating NMR signals with spatial position information, and modulation pulse signals for modulating high-frequency carrier waves.As digital signals, there are transmission gates to send to the transmitter. There are control signals, a reception gate signal sent to the receiving device, a D conversion control signal, etc.

FIG. 1 is a block diagram showing a conventional waveform generator for an NMR apparatus. 1 is a waveform generator whose X gradient magnetic field signal output x1 is applied to an X gradient magnetic field generating coil (hereinafter referred to as an X gradient coil; the same applies to LZ) 3 via an X gradient driver 2.

The y gradient magnetic field signal output y1 is transmitted to y via the y gradient driver 4.
applied to gradient coil 5. The two-gradient magnetic field signal output z1 is applied to the two-gradient coil 7 via the two-gradient driver 6. The modulated signal output M1 modulates the high frequency carrier wave c1 in the modulator 8, and the high frequency modulated wave is applied to the excitation coil 10 via the high frequency power amplifier 9. On/off of the high frequency power amplifier 9 is controlled by a transmission gate control signal S1. The reception gate control signal R1 is sent to the reception coil 11.
A grid amplifier 12 that amplifies the NλIR signal detected from the
The D conversion control signal T1 controls the on/off of the detector 1.
D conversion circuit 1 that converts the NMR signal detection output from 3 into D.
Controls the operations of 4. 15 is digitized NMR
This is an NMR signal output terminal that outputs a signal to a signal processing device or the like.

Conventional waveform generators include software control systems and fixed hardware systems. The software control method has the disadvantage that high-speed control is not possible because writing takes time. Fixed hardware methods include, for example, circuits that generate a harbor sine wave (a waveform that emits only one half-wave sine wave) using a trigger pulse.
It has the disadvantage that it is difficult to change the control sequence, change the analog waveform, and use for mail, and lacks flexibility.

〔the purpose〕

The present invention has been made to solve the above problems, and provides a highly flexible waveform generator for NMR equipment that can perform high-speed control and easily change control sequences and analog waveforms. The purpose is to

〔overview〕

According to the present invention, the write control circuit causes the waveform data of at least one signal among the gradient magnetic field signal, the modulation signal, and the transmitting/receiving circuit control signal from the computer to be stored in the waveform storage memory, and from the waveform storage memory. The above object can be achieved by simultaneously reading out the data of each signal waveform (by the readout control circuit).

[Explanation of Examples]

The present invention will be explained below based on the drawings.

FIG. 2 is a block diagram showing an embodiment of a waveform generator for an NMR apparatus according to the present invention. 21 is a write control circuit that writes data sent from the computer into each memory, and 22, 25, 28, and 31 are waveform memories into which the waveform data of the bx, y, z gradient signals and modulation signals are written, respectively. Memory, 23.26.29
．． 32 is a latch circuit that temporarily holds the waveform data output from the waveform storage memory 22, 25, 28.31, and 24.27.30.33 is the latch circuit 23.26.
．． 29. A DA conversion circuit for DA converting the outputs from x2. y2. z2. M2 are X and y output from the DA conversion circuit 24, 27, 30, and 33, respectively.

2 gradient signal output and modulation signal output. 34°36
, 38 is a waveform storage memory into which the data of the transmitting/receiving circuit control signal, that is, the D conversion control signal, the transmitting gate control signal, and the receiving gate control signal are written from the write control circuit 21, and 35, 37, and 39 are the waveform storing memo! j
34. A latch circuit that temporarily holds the data output from 36.38, T2. S2. R2 is this latch circuit 35.
These are a D conversion control signal, a transmission gate control signal output, and a reception gate control signal output, respectively, which are output from 37 and 39. 41 is each waveform storage memory 22, 25, 28.3 mentioned above.
The contents of 1.34.36.38 are converted to the latte circuit 23゜2.
6, a read control circuit for reading data to 29, 32, 35, 37, and 39; 40 is a memory that receives a write/read start address from the computer, is sequentially added from the write/read control circuit, and specifies a write/read address; An address register 42 is an output count register in which the number of output steps is set by the computer and informs the readout control circuit 41 of the end of output; 43 is an output count register 43 which is set by the computer to the time length of one step; This is a one-step-length pulse generation circuit that generates a step-length pulse.

The operation of the circuit configured as described above will be explained below.

0) Write operation In the write operation, waveform data sent from the computer is written to a specified address in the waveform storage memory specified by the computer. That is, first, the computer sets a write start address in the memory address register 40. The write control circuit 21 selects one waveform storage memory (for example, the waveform storage memory 22) and writes the data sent from the computer together with the write command to the address indicated by the memory address register 4o. After this, write control circuit 2
1 is automatically added to the memory address register 4o to make it a memory address ready for the next write.

Thereafter, the data sent in the same manner is written to the Ilf[ii] waveform storage memory.

(b) Read operation In the read operation, each memory is read in parallel by a start command from the converter. FIG. 3 shows an example of a time chart of read signal waveforms.

First, the computer sets the reading start address of the waveform storage memory in the memory address register 4o.

Next, the number of read steps is set in the output count register 42. Further, one step length (time per one step during reading) is set in one step length pulse generation circuit 43. Next, the contents of the waveform storage memories 22, 25, 28, 31, 34, and 36, 38 at the address indicated by the memory address register 4o are read out at the same time by a read start command from the converter, and when the data is all read out, the read control circuit 41 is closed. Latch circuit 23, 26.29.32.
At 35.37.39, a ratte pulse is output and data is latched. Next, 1 is added to the value of the memory address register 40. If the output count register 42 indicates completion, the read control circuit 41 starts the latch circuit 23.26.2.
9.32.35.37.39 Output K clear pulse and end read operation. When the output count register 42 does not indicate completion, 1 is subtracted from the output count register 42, and after waiting for one step time length according to the output from the one step length pulse generation circuit 43, the process moves to the next reading step. By repeating the same procedure, for example, a waveform like the one shown in FIG. 3 can be read out.
Gradient signal x2. y2. z2 and modulation signal M2 are outputted from the latch circuit and further sent to DA converters 24-, 27.30.3.
3, performs DA conversion to obtain an analog signal.

According to the waveform generator for an NMR apparatus configured as described above, since dedicated hardware such as a waveform storage memory is provided, a large amount of data can be read and output at high speed. Since the contents of the waveform storage memory can be rewritten as necessary, any analog or digital signal waveform can be output. Furthermore, it is easy to use part of the signal waveform (which is often actually used) by appropriately giving the read start address and the number of read steps.

Note that in the case of a signal waveform as shown in FIG. 4, the interval t□
This can also be achieved by reading from the waveform storage memory step by step only during the interval, holding the last data of the interval t1 without clearing it, and turning off the output by a command from the combinator at the end of the interval t2. . In this case, there is an advantage that memory usage can be saved.

If the waveform storage memory shown in FIG. 2 is placed in the address space of the computer during writing, the address during writing can be controlled by software.

FIG. 5 is a block diagram showing a second embodiment of the present invention.
A time memory 44 is added to the circuit shown in the figure, so that the length of one step (the duration of output data) can be made variable. In the figure, the same reference numerals are used for the same parts as in FIG. 2, and the explanation of the structure will be omitted. Regarding the write operation, data of one step length is written from the computer to the time memory 44 in the same manner as in the case of the waveform storage memory in the first embodiment. If it is desired to output the same waveform data continuously, the value of one step length written in the time memory 44 may be increased accordingly.

In the case of a read operation, when the contents of each waveform memory are latched into each latch circuit in the read operation of the first embodiment, the data of the time memory at the corresponding address is output to the one-step length pulse generation circuit. Generate a pulse with one step length. The length of one step in this case differs from that in the first embodiment, and can take a specific value (time) each time. FIG. 6 shows the same output waveform as in FIG. 5) is a time chart obtained using the method shown in FIG. Unlike the case in FIG. 3, the number of steps can be reduced by increasing the length of one step in the portion where the same output value continues, thereby saving the amount of waveform storage memory used. If you still want to change part of the time of the signal waveform sequence, you can easily do so by changing only the contents of the time memory. That is, for example, if it is desired to lengthen only the portion of step A in FIG. 6, it is sufficient to rewrite only one corresponding word in the time memory. To achieve this with a circuit that does not have time memory, it is difficult because all data (analog and digital) after the step person must be rewritten.

Note that if the time memory is omitted in the above embodiment and data of one step length is sent out sequentially from the computer, the amount of hardware can be reduced, although the speed will be slightly lower due to the intervention of software and communication.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a waveform generator for an NMR apparatus that is capable of high-speed control and has a high degree of flexibility in which control sequences and analog waveforms can be easily changed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional waveform generator for NMR equipment, FIG. 2 is a block diagram showing an embodiment of the waveform generator for NMR equipment according to the present invention, and FIGS. 3 and 4 are FIG. 2 is a time chart showing the output waveform of the device, FIG. 5 is a block diagram showing the second embodiment of the present invention, and FIG. 6 is a time chart showing the output waveform of the device in FIG. ...Write control circuit, 22.25.2B, 31
．． 34.36°38...Waveform storage memory, 41...
Readout control circuit, 44...Time memo! j, x2.
y2p z2...Gradient magnetic field signal, M2...Modulation signal, T2.82. R2... Transmission/reception circuit control signal. O I figure

Claims (2)

[Claims] (1) a waveform storage memory that stores a signal waveform of at least one of a gradient magnetic field signal, a modulation signal, and a transmitter/receiver circuit control signal; a write control circuit that writes data from a computer to the waveform storage memory; A waveform generator for an NMR apparatus, comprising a readout control circuit that simultaneously reads data of each of the signal waveforms from a waveform storage memory. (2) a waveform storage memory that stores a signal waveform of at least one of a gradient magnetic field signal, a modulation signal, and a transmission/reception circuit control signal; a write control circuit that writes data from a computer to the waveform storage memory; A waveform generator for an NMR apparatus, comprising: a readout control circuit that simultaneously reads data of each signal waveform from a waveform storage memory; and a time memory that specifies a duration of output data from the waveform storage memory.