CN111521963B - Method for automatically adapting and outputting gradient waveform rate and magnetic resonance system - Google Patents
Method for automatically adapting and outputting gradient waveform rate and magnetic resonance system Download PDFInfo
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- CN111521963B CN111521963B CN202010371159.XA CN202010371159A CN111521963B CN 111521963 B CN111521963 B CN 111521963B CN 202010371159 A CN202010371159 A CN 202010371159A CN 111521963 B CN111521963 B CN 111521963B
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- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
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- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
Abstract
The invention discloses a method and a magnetic resonance system for automatically adapting and outputting gradient waveform rate, which are applied to the technical field of computers and aim at the problem that the gradient waveform signal rate of magnetic resonance sequence design in the prior art can not be flexibly configured according to magnetic resonance application, the invention matches the gradient waveform rate of nuclear magnetic resonance sequence design into the conversion rate of an analog-to-digital converter of a gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface with a digital gradient amplifier, when the gradient waveform rate of nuclear magnetic resonance sequence design is realized, is not constrained by the internal operating rate of the field programmable logic device of the gradient waveform signal generator, and meanwhile, the technical effect of the restraint of the conversion rate of an analog-to-digital converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface with the digital gradient amplifier is avoided.
Description
Technical Field
The invention belongs to the technical field of computers, and particularly relates to a technology capable of automatically adapting gradient waveform signal rate in nuclear magnetic resonance imaging.
Background
Nuclear magnetic resonance is a commonly used imaging examination technique in modern medicine. The nuclear magnetic resonance system comprises a magnet system, a gradient system, a radio frequency system, a signal acquisition system, an image reconstruction system and the like. The gradient system is used for providing linearity for the nuclear magnetic resonance system to meet requirements, and a gradient magnetic field capable of being switched on and off rapidly is superposed on a main magnetic field to realize space positioning of imaging voxels. The gradient system comprises a gradient waveform generator, a gradient amplifier, a gradient coil and the like.
In a magnetic resonance imaging system, accurate positioning of spatial position information of each voxel of a subject is important to obtain accurate image information. At present, a magnetic resonance imaging system generates a three-axis gradient waveform through a gradient waveform generator, and then drives a three-dimensional gradient coil after amplifying the three-axis gradient waveform through a gradient amplifier, so as to realize the spatial positioning of each voxel of a detected body.
The gradient waveform generator is used for outputting three-axis gradient signals. In the gradient waveform generator, there are two implementations: one of the general techniques is to convert a digital gradient signal into an analog gradient signal by using a digital-to-analog converter for output, and then output the analog gradient signal to a gradient amplifier; another common technique is that the gradient waveform generator has no digital-to-analog converter, and directly transmits the gradient waveform data to the gradient amplifier via a digital communication protocol interface, and the gradient amplifier receives the digital gradient waveform data. Both techniques are currently used in the field of nuclear magnetic resonance.
In the first general technique, the gradient waveform generator integrates a digital-to-analog converter, wherein the slew rate of the digital-to-analog converter is fixed at the beginning of the design. In the second general technique, the gradient waveform generator has no digital-to-analog converter, and directly transmits gradient waveform data to the digital gradient amplifier via the digital communication protocol interface, the digital gradient amplifier receives the digital gradient waveform data, and the digital communication protocol generally fixes the rate of the gradient waveform signal at the beginning of the design. The gradient waveform signal rate of existing magnetic resonance sequence designs cannot be flexibly set according to the magnetic resonance application, and is also generally passively limited by the gradient waveform signal rate constraint of the gradient waveform generator.
The patent with application number 201910084627.2 discloses a resampling filter and a filtering method, and the embodiment discloses a resampling filter and a filtering method, and the method can include: shunting input data according to a set filtering function to obtain N pieces of shunting data; wherein the filtering function comprises an N-fold interpolation filtering function or an N-fold decimation filtering function; performing multiply-add processing on the shunting data to obtain output data; selecting all output data and the sum of all output data according to a set filtering function to obtain intermediate data; and sampling the intermediate data according to the sampling frequency corresponding to the filtering function to obtain the re-sampled filtering data. The patent does not consider remainder processing of intermediate data.
Patent application No. 200610011592.2 discloses a resampling method for a digital signal, which is used to down-sample an input pixel sequence O with a length of W1 and output a pixel sequence R with a length of W2, where W1 > W2, and is characterized in that when W1 pixels in the sequence O are input step by step in resampling, X1 averages S1 pixels as one pixel of the output sequence R, X2 averages S2 pixels as one pixel of the output sequence R, and obtains the pixel sequence R, where X1 ═ W1% W1% W2, X2 ═ W2-X2, S2 ═ Ceil (W2/W2), S2 ═ Floor (W2/W2), Ceil represents upward rounding operation, Floor () represents downward rounding operation, and S2 = S2 + 2 represents a left operation. The method of the invention can reduce the calculated amount and the memory space and flexibly realize the resampling of the digital signal. This patent only roughly considers two ways of processing the remainders of each pixel value, rounded up and rounded down, for each pixel value of a sequence R of length W2.
When the above 2 patents are used for rate resampling or rate re-matching, the processing of the remainder of each intermediate data or pixel point after resampling is not accurately considered, so that the ideal gradient waveform area of the sequence design has an error with the actually-sent gradient waveform area, and the error of three-dimensional space positioning is caused.
Disclosure of Invention
In order to solve the problem that the gradient waveform signal rate designed by a magnetic resonance sequence in the prior art cannot be flexibly configured according to the application of magnetic resonance, the invention provides a method and a device for automatically adapting and outputting the gradient waveform signal rate and a magnetic resonance system; the invention adds the remainder of the current point after rate re-matching to the accumulator of the next point. Moreover, the nuclear magnetic resonance gradient system adopts a two-stage rate re-matching structure.
The technical scheme adopted by the invention is as follows: a method of automatically adapting a gradient waveform signal rate to an output, comprising: the automatic adaptation of the internal operation unit rate of the field programmable logic device of the gradient waveform generator and the gradient waveform signal rate designed by the nuclear magnetic resonance sequence is carried out; and automatically adapting the internal operation rate of the field programmable logic device of the gradient waveform generator to the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of the single-axis gradient waveform signal of the digital communication interface with a digital gradient amplifier;
the automatic adaptation of the internal operation unit rate of the field programmable logic device of the gradient waveform generator and the gradient waveform signal rate designed by the nuclear magnetic resonance sequence specifically comprises the following steps: mapping one period T2 of an internal operation unit of a field programmable logic device of the gradient waveform generator to two adjacent point interval periods T1 of gradient waveform signals designed by a plurality of nuclear magnetic resonance sequences; converting the gradient waveform value in two adjacent point interval periods T1 of the gradient waveform signals designed by the nuclear magnetic resonance sequence into a gradient area, and finally converting the gradient area into the amplitude of the gradient waveform signal of one period T2 of the internal operation unit of the field programmable logic device of the gradient waveform generator;
the automatic adaptation of the internal operation rate of the field programmable logic device of the gradient waveform generator to the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface with a digital gradient amplifier is specifically as follows: mapping one period T3 of the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier to one period T2 of an internal operation unit of a field programmable logic device of a plurality of gradient waveform generators; the amplitude values of the gradient waveform signals in the period T2 of the internal operation unit of the field programmable logic device of the gradient waveform generators are converted into gradient areas, and finally converted into the conversion rate of a digital-to-analog converter or the amplitude values of the gradient waveform signals in the period T3 of the interface unit for digital communication with the digital gradient amplifier.
The automatic adaptive output device based on the gradient waveform signal rate sequentially comprises: gradient waveform signal unit designed by nuclear magnetic resonance sequence, internal operation unit of field programmable logic device of gradient waveform generator, digital-to-analog converter conversion rate or digital communication interface unit with digital gradient amplifier;
the gradient waveform signal unit designed by the nuclear magnetic resonance sequence at least comprises a register module;
the internal operation unit of the field programmable logic device of the gradient waveform generator sequentially comprises: the device comprises a register reading module, a first accumulator and a first gradient waveform filter;
the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier sequentially comprises: a gradient waveform resampling module, a second accumulator, a second gradient waveform filter, a digital-to-analog converter or a digital gradient amplifier communication protocol interface.
In the current T2 period, the register reading module continuously reads the register stored by the gradient waveform signal designed by the nuclear magnetic resonance sequence according to the minimum time precision of the internal operation unit of the field programmable logic device of the gradient waveform generator; the first accumulator accumulates the amplitude of the gradient signal according to the reading result of the register reading module; the first gradient waveform filter divides the value obtained by the accumulator by the total reading times of the register reading module in the T2 period and takes the integer as the amplitude value of the output gradient waveform signal in the current T2 period; the first gradient waveform filter divides the value obtained by the first accumulator by the total reading times of the register reading module in the T2 period to obtain a remainder as an initial accumulated value of the first accumulator in the next T2 period.
The first accumulator accumulates the amplitude of the gradient signal according to the reading result of the register reading module; the specific process is as follows: and accumulating the amplitude values according to the times of the gradient waveform signals read by the register reading module, wherein the sum of the read times of the gradient waveform signals with different amplitude values is equal to T2 divided by the result of the minimum time precision of the internal operation unit of the field programmable logic device of the gradient waveform generator.
In the current T3 period, if the amplitude of the gradient waveform output by the gradient waveform filter is unchanged all the time, the gradient waveform resampling module directly transmits the amplitude of the gradient waveform output by the gradient waveform filter to a digital-to-analog converter or a digital gradient amplifier communication protocol interface; if the amplitude of the gradient waveform output by the gradient waveform filter changes, the gradient waveform resampling module continuously reads the gradient waveform signal output by the first gradient waveform filter at the conversion rate of a digital-to-analog converter or with the minimum time precision of a digital communication interface unit of a digital gradient amplifier; the second accumulator accumulates the amplitude of the gradient waveform signal according to the reading result of the gradient waveform resampling module; the second gradient waveform filter divides the value obtained by the second accumulator by the total reading times of the gradient waveform resampling module in the T3 period, and the division result is rounded as the amplitude value of the gradient waveform signal which is output to the digital-to-analog converter or the digital gradient amplifier communication protocol interface module in the current T3 period; the second gradient waveform filter divides the value obtained by the second accumulator by the total reading times of the gradient waveform resampling module in the T3 period to obtain a remainder which is used as the initial accumulated value of the second accumulator in the next T3 period.
The second accumulator accumulates the amplitude of the gradient waveform signal according to the reading result of the gradient waveform resampling module; the specific process is as follows: the amplitude values are accumulated according to the times of the gradient waveform signals read by the gradient waveform resampling module, and the sum of the read times of the gradient waveform signals with different amplitude values is equal to T3 divided by the conversion rate of the digital-to-analog converter or the minimum time precision of the digital communication interface unit with the digital gradient amplifier.
A nuclear magnetic resonance system adopts the method to automatically adapt the gradient waveform signal rate.
The gradient waveform adaptation method is mainly applied to a gradient waveform generator of nuclear magnetic resonance; the nuclear magnetic resonance system comprises a magnet system, a gradient system, a radio frequency system, a signal acquisition system, an image reconstruction system and the like. The gradient system is composed of a gradient waveform generator, a gradient amplifier and a gradient coil. The gradient waveform generator consists of 2 parts: the internal operation unit of the field programmable logic device, the digital-to-analog converter conversion rate or the digital communication interface unit with the digital gradient amplifier.
The invention has the beneficial effects that: the nuclear magnetic resonance sequence design gradient waveform rate is matched into the digital-to-analog converter conversion rate of the gradient waveform signal generator or the single-axis gradient waveform signal data transmission rate of the digital communication interface with the digital gradient amplifier, so that the gradient area precision actually output by the digital-to-analog converter of the gradient waveform signal generator or the digital communication interface with the digital gradient amplifier is consistent with the gradient waveform area designed by the nuclear magnetic resonance sequence;
meanwhile, the nuclear magnetic resonance sequence design gradient waveform does not need to concern the internal operation rate of a field programmable logic device of the gradient waveform signal generator, the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface with a digital gradient amplifier and other hardware indexes; the internal operation rate of the field programmable logic device of the gradient waveform signal generator can be automatically adapted to the rate of the gradient waveform signals designed by different nuclear magnetic resonance sequences;
the invention realizes the technical effect that the nuclear magnetic resonance sequence is not restricted by the internal operation rate of the field programmable logic device of the gradient waveform signal generator when designing the gradient waveform rate, and simultaneously, the digital-to-analog converter conversion rate of the gradient waveform signal generator or the uniaxial gradient waveform signal data transmission rate of a digital communication interface with a digital gradient amplifier are not restricted, thereby ensuring that the nuclear magnetic resonance sequence has considerable flexibility when designing the gradient waveform.
Drawings
FIG. 1 is a block diagram of an implementation of rate conversion and auto-matching of gradient waveform signals according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating the rate matching from T1 to T2 when T1 is smaller than T2 according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating the rate matching from T1 to T2 when T1 is equal to or greater than T2 according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating rate matching from T2 to T3 according to an embodiment of the present invention;
Detailed Description
In order to facilitate the understanding of the technical contents of the present invention by those skilled in the art, the present invention will be further explained with reference to the accompanying drawings.
Because the area of the magnetic resonance gradient waveform is required to have high precision and needs to be consistent with the area of the upper layer design theory gradient waveform, the invention accumulates the remainder of the current point after the rate is re-matched into the accumulator of the next point. Moreover, the invention discloses a two-stage rate re-matching structure aiming at a gradient system of nuclear magnetic resonance.
The rate of the gradient waveform signal generator of the invention relates to the rate of 3 layers, and the corresponding reciprocal is the period time of the corresponding layer; the method comprises the following steps from top to bottom:
the gradient waveform signal rate designed by the nuclear magnetic resonance sequence has the period T1, namely the interval time of two adjacent points;
the internal operation rate of the field programmable logic device of the gradient waveform signal generator is T2;
the digital-to-analog converter slew rate of the gradient waveform signal generator or the data transfer rate of the single-axis gradient waveform signal interfacing with the digital gradient amplifier in digital communication has a period T3.
As shown in fig. 1, from the functional division, the internal operation unit of the field programmable logic device of the gradient waveform generator sequentially comprises a register reading module, a first accumulator, and a first gradient waveform filter; the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier sequentially comprises: a gradient waveform resampling, a second accumulator, a second gradient waveform filter, and a digital-to-analog converter or digital gradient amplifier communication protocol interface;
from top to bottom: the gradient waveform designed by the nuclear magnetic resonance sequence is transmitted to the register reading module through the gradient waveform register; the next stage functional unit of the register reading module is respectively a first accumulator, a first gradient waveform filter, a gradient waveform resampling, a second accumulator, a second gradient waveform filter, a digital-to-analog converter or a digital gradient amplifier communication protocol interface.
In the embodiment of the invention, the internal operation rate of the field programmable logic device of a gradient waveform generator is automatically matched with the gradient waveform signal rate designed by a nuclear magnetic resonance sequence; the specific process is as follows: because the size of the gradient is calculated by the area of the output gradient and has no great relation with the size of the instantaneous gradient value, by utilizing the principle, the invention maps one period of the internal operation of the field programmable logic device of the gradient waveform generator to two adjacent point interval periods of the gradient waveform signals designed by a plurality of nuclear magnetic resonance sequences; the gradient waveform values in two adjacent point interval periods of the gradient waveform signals designed by a plurality of nuclear magnetic resonance sequences are converted into gradient areas, and then the gradient areas are converted into the amplitude of the gradient waveform signal of one period of internal operation of the field programmable logic device of the gradient waveform generator.
The automatic adaptation mode from the internal operation rate of the field programmable logic device of the gradient waveform generator to the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface with a digital gradient amplifier is consistent with the principle of automatic adaptation from the gradient waveform signal rate designed by a nuclear magnetic resonance sequence to the internal operation rate of the field programmable logic device of the gradient waveform generator: mapping one period T3 of the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier to one period T2 of an internal operation unit of a field programmable logic device of a plurality of gradient waveform generators; the amplitude values of the gradient waveform signals in the period T2 of the internal operation unit of the field programmable logic device of the gradient waveform generators are converted into gradient areas, and finally converted into the conversion rate of a digital-to-analog converter or the amplitude values of the gradient waveform signals in the period T3 of the interface unit for digital communication with the digital gradient amplifier.
T1 is the interval period of two adjacent points of gradient waveform signal designed by nuclear magnetic resonance sequence, T2 is the internal operation period of field programmable logic device of a gradient waveform generator. tick1 is the minimum time precision of the internal arithmetic unit of the field programmable logic device of the gradient waveform generator, T2 equals 2^ n tick1 time lengths. The length of T1 can be flexibly set according to sequence application. The minimum value of the power exponent n of 2^ n is constrained by the operation cycle of an algorithm of an internal operation unit of a field programmable logic device of a gradient waveform generator, the algorithm is mainly used for calculating a gradient pre-emphasis amplitude value and B0 compensation frequency, the algorithm needs to carry out recursive operation on 64 groups of time parameters and amplitude parameters fitted by gradient eddy currents at most, 4 operation cycles (4 ticks 1) are occupied for average operation on each group of time parameters and amplitude parameters, and then 64 groups of parameter operation need to at least 256 ticks 1, namely 2^8 ticks 1. Thus, n has a minimum value of 8.
If T1 is smaller than T2, as shown in fig. 2, taking 3 gradient waveform data (amplitude values a, B, and C, respectively) sent in sequence received within a T2 time period as an example, the register reading module continuously reads the register in which the gradient waveform amplitude value designed by the nmr sequence is located with the time period of tick1, and assuming that the waveform amplitude value with amplitude value a is read n1 times and the waveform amplitude value with amplitude value B is read n2 times, the number of times of reading the waveform amplitude value with amplitude value C is 2^ n-n1-n 2. The operations performed in the accumulator 1 are: the cumulative gradient waveform area over the T2 time period was A n1+ B n2+ C (2 n-n1-n 2). The gradient waveform filter 1 performs the operation: (A x n1+ B x n2+ C (2 x n-n1-n2))/2 x n, the integral part of the operation result of the gradient waveform filter 1 is the gradient waveform amplitude value which the gradient waveform filter 1 should output to the gradient waveform resampling module at the current T2 cycle time, and is named as Amp _ T2; the remainder part of the operation result of the gradient waveform filter 1 is used as the initial accumulation value of the accumulator 1 for the next T2 cycle.
If T1 is greater than or equal to T2, as shown in fig. 3, the register reading module continuously reads the register where the gradient waveform amplitude value designed by the nmr sequence is located in the time period of tick1, wherein the time period of T1 corresponds to 2 to 3T 2 cycles. If the register in which the gradient waveform amplitude value is located has not changed in the period T2, in the period T2, the gradient waveform amplitude value that the gradient waveform filter 1 should output to the gradient waveform resampling module at each period T2 is equal to the gradient waveform amplitude value designed by the nmr sequence. If the register where the gradient waveform amplitude value designed by the nuclear magnetic resonance sequence is located is changed in the period T2, and before and after the register where the gradient waveform amplitude value is located is changed, the register where the gradient waveform amplitude value with the amplitude value A is located is read n1 times, and then the register where the gradient waveform amplitude value B is located is read 2^ n-n1 times. The operations performed in the accumulator 1 are: the cumulative gradient waveform area over the T2 time period is A n1+ B (2 n-n 1). The gradient waveform filter 1 performs the operation: (A x n1+ B (2^ n-n1))/2^ n, the integral part of the operation result of the gradient waveform filter 1 is the gradient waveform amplitude value Amp _ T2 which the gradient waveform filter 1 should output to the gradient waveform resampling module at the current T2 cycle time; the remainder part of the operation result of the gradient waveform filter 1 is used as the initial accumulation value of the accumulator 1 for the next T2 cycle.
The digital-to-analog converter slew rate of the gradient waveform signal generator or the data transfer rate of the single-axis gradient waveform signal interfacing with the digital gradient amplifier has a period of T3, and in general implementation T3 is generally less than T2. tick2 is the digital-to-analog converter slew rate or minimum time accuracy of the digital communication interface unit with the digital gradient amplifier, T3 equals 2^ m tick2 time lengths.
As shown in fig. 4, the gradient waveform resampling module constantly reads the gradient waveform data of the output of the gradient waveform filter 1 with a time period of tick 2. If the gradient waveform amplitude value data of the output of the gradient waveform filter 1 has not changed in the period T3, the gradient waveform resampling directly transmits the gradient waveform amplitude value data of the output of the gradient waveform filter 1 to the digital-to-analog converter or the digital gradient amplifier communication protocol interface in the period T3. If the gradient waveform amplitude value data output by the gradient waveform filter 1 changes in the period T3, and the sequence gradient waveform amplitude value with the amplitude value A is read m1 times before and after the gradient waveform amplitude value data output by the gradient waveform filter 1 changes, then the sequence gradient waveform amplitude value B is read 2^ m-m1 times. The operations performed in the accumulator 2 are: the cumulative gradient waveform area over the current T3 time period is A m1+ B (2 m-m 1). The gradient waveform filter 2 performs the operation: (A × m1+ B ^ m-m1))/2^ m, the integral part of the operation result executed by the gradient waveform filter 2, namely the gradient waveform amplitude value which is required to be output to a digital-to-analog converter or a digital gradient amplifier communication protocol interface module by the gradient waveform filter 2 in the current T3 period is named as Amp _ T3; the gradient waveform filter 2 performs an operation to take the remainder part as the initial accumulated value of the accumulator 2 for the next T3 cycle.
The prior art has 2 processing modes for remainder: throwing away; rounding up or rounding down, the processing of the remainder is always in error. The invention adds the remainder of the current point after rate re-matching into the accumulator of the next point, so that the gradient area of the gradient waveform generator is completely consistent with the gradient waveform area designed by a sequence designer, thereby positioning the three-dimensional gradient space more accurately.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (7)
1. A method for automatically adapting a gradient waveform signal rate to an output, comprising: the automatic adaptation of the internal operation unit rate of the field programmable logic device of the gradient waveform generator and the gradient waveform signal rate designed by the nuclear magnetic resonance sequence is carried out; the internal operation rate of the field programmable logic device of the gradient waveform generator is automatically adapted to the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface of a digital gradient amplifier;
the automatic adaptation of the internal operation unit rate of the field programmable logic device of the gradient waveform generator and the gradient waveform signal rate designed by the nuclear magnetic resonance sequence specifically comprises the following steps: mapping one period T2 of an internal operation unit of a field programmable logic device of the gradient waveform generator to two adjacent point interval periods T1 of gradient waveform signals designed by a plurality of nuclear magnetic resonance sequences; converting the gradient waveform value in two adjacent point interval periods T1 of the gradient waveform signals designed by the nuclear magnetic resonance sequence into a gradient area, and finally converting the gradient area into the amplitude of the gradient waveform signal of one period T2 of the internal operation unit of the field programmable logic device of the gradient waveform generator;
the automatic adaptation of the rate of an internal operation unit of the field programmable logic device of the gradient waveform generator to the conversion rate of a digital-to-analog converter of the gradient waveform signal generator or the data transmission rate of a single-axis gradient waveform signal of a digital communication interface unit with a digital gradient amplifier is specifically as follows: mapping one period T3 of the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier to one period T2 of an internal operation unit of a field programmable logic device of a plurality of gradient waveform generators; the amplitude values of the gradient waveform signals in the period T2 of the internal operation unit of the field programmable logic device of the gradient waveform generators are converted into gradient areas, and finally converted into the conversion rate of a digital-to-analog converter or the amplitude values of the gradient waveform signals in the period T3 of the interface unit for digital communication with the digital gradient amplifier.
2. The method of claim 1, wherein the apparatus for automatically adapting gradient waveform signal rate comprises: gradient waveform signal unit designed by nuclear magnetic resonance sequence, internal operation unit of field programmable logic device of gradient waveform generator, digital-to-analog converter conversion rate or digital communication interface unit with digital gradient amplifier;
the gradient waveform signal unit designed by the nuclear magnetic resonance sequence at least comprises a register module;
the internal operation unit of the field programmable logic device of the gradient waveform generator sequentially comprises: the device comprises a register reading module, a first accumulator and a first gradient waveform filter;
the digital-to-analog converter conversion rate or digital communication interface unit with the digital gradient amplifier sequentially comprises: a gradient waveform resampling module, a second accumulator, a second gradient waveform filter, a digital-to-analog converter or a digital gradient amplifier communication protocol interface.
3. The method of claim 2, wherein the register reading module continuously reads the register storing the gradient waveform signal of the nuclear magnetic resonance sequence design according to the minimum time precision of the internal operation unit of the field programmable logic device of the gradient waveform generator in the current T2 cycle; the first accumulator accumulates the amplitude of the gradient signal according to the reading result of the register reading module; the first gradient waveform filter divides the value obtained by the accumulator by the total reading times of the register reading module in the T2 period and takes the integer as the amplitude value of the output gradient waveform signal in the current T2 period; the first gradient waveform filter divides the value obtained by the first accumulator by the total reading times of the register reading module in the T2 period to obtain a remainder as an initial accumulated value of the first accumulator in the next T2 period.
4. The method of claim 3, wherein the first accumulator accumulates the amplitude of the gradient signal according to the reading result of the register reading module; the specific process is as follows: and accumulating the amplitude values according to the times of the gradient waveform signals read by the register reading module, wherein the sum of the read times of the gradient waveform signals with different amplitude values is equal to T2 divided by the result of the minimum time precision of the internal operation unit of the field programmable logic device of the gradient waveform generator.
5. The method of claim 4, wherein during the current T3 period, if the amplitude of the gradient waveform output by the gradient waveform filter is constant, the gradient waveform resampling module directly transmits the amplitude of the gradient waveform output by the gradient waveform filter to the DAC or DPMA communication protocol interface; if the amplitude of the gradient waveform output by the gradient waveform filter changes, the gradient waveform resampling module continuously reads the gradient waveform signal output by the first gradient waveform filter at the conversion rate of a digital-to-analog converter or with the minimum time precision of a digital communication interface unit of a digital gradient amplifier; the second accumulator accumulates the amplitude of the gradient waveform signal according to the reading result of the gradient waveform resampling module; the second gradient waveform filter divides the value obtained by the second accumulator by the total reading times of the gradient waveform resampling module in the T3 period, and the division result is rounded as the amplitude value of the gradient waveform signal which is output to the digital-to-analog converter or the digital gradient amplifier communication protocol interface module in the current T3 period; the second gradient waveform filter divides the value obtained by the second accumulator by the total reading times of the gradient waveform resampling module in the T3 period to obtain a remainder which is used as the initial accumulated value of the second accumulator in the next T3 period.
6. The method of claim 5, wherein the second accumulator accumulates the amplitude of the gradient waveform signal according to the read result of the gradient waveform resampling module; the specific process is as follows: the amplitude values are accumulated according to the times of the gradient waveform signals read by the gradient waveform resampling module, and the sum of the read times of the gradient waveform signals with different amplitude values is equal to T3 divided by the conversion rate of the digital-to-analog converter or the minimum time precision of the digital communication interface unit with the digital gradient amplifier.
7. A nuclear magnetic resonance system, wherein the gradient waveform signal rate is automatically adapted by a method of automatically adapting the gradient waveform signal rate output according to any one of claims 1 to 6.
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