WO2020211135A1 - Quantitative myocardial magnetic resonance imaging method and device, and storage medium - Google Patents

Abstract

Provided is a quantitative myocardial magnetic resonance imaging method, comprising: insofar as a flip angle of a data collection radio-frequency pulse is equal to a first flip angle, collecting first image signals until k-spaces can be filled with same, wherein the first flip angle is less than a first threshold value (S310); insofar as the flip angle of the data collection radio-frequency pulse is equal to a second flip angle, collecting, after preparation pulses with different pulse parameters are used to complete the preparation of magnetization vectors, at least two image signals that can fill the k-spaces, wherein the second flip angle is greater than a second threshold value but is less than a third threshold value, and the second threshold value is greater than the first threshold value (S320); according to all the image signals, a pulse parameter of a preparation pulse corresponding to each image signal, and the first flip angle and the second flip angle, determining a magnetic resonance quantitative parameter (S330); and generating a quantitative myocardial magnetic resonance image according to the magnetic resonance quantitative parameter (S340). The method increases the speed of quantitative myocardial magnetic resonance imaging, and has a strong universality. Further disclosed are a corresponding magnetic resonance imaging device and a storage medium.

Description

Quantitative myocardial magnetic resonance imaging method, equipment and storage medium Technical field

The invention relates to the field of medical imaging, and more specifically to a quantitative myocardial magnetic resonance imaging method, equipment and storage medium.

Background technique

Magnetic resonance imaging technology uses nuclear magnetic resonance to image the human body and is already a common medical imaging examination method.

The quantitative myocardial magnetic resonance imaging technology developed in recent years directly measures the basic physical parameters of magnetic resonance to achieve quantitative myocardial tissue evaluation. Basic physical parameters such as T ₁ (spin lattice relaxation time, or called longitudinal relaxation time) and T ₂ (spin-spin relaxation time, or called transverse relaxation time). These two are the time constants that describe the recovery of the longitudinal magnetization vector and the decay process of the transverse magnetization vector. The physical parameters of magnetic resonance are determined by the composition and structure of biological tissues and the strength of the magnetic field. Under a certain magnetic field strength, different organizations have specific physical parameter values. When the biological tissue changes, the physical parameter values will also change accordingly. Therefore, these physical parameter values can be used as characteristic parameters to identify the characteristics of myocardial tissue.

In the existing quantitative myocardial magnetic resonance imaging technology, the weighting of different physical parameters is achieved by using preparation pulses such as inversion pulses and saturation pulses, thereby obtaining multiple physical parameter weighted sampling points. The physical parameters are determined by fitting these sampling points according to the recovery and attenuation of physical parameters.

The steady-state magnetization vector is the anchor point for physical parameter recovery and the key point for determining physical parameters. The steady-state magnetization vector refers to a signal without any signal disturbance or weighting, that is, the magnetization vector that can be reached if the physical parameter recovery time is infinite. In the prior art, the steady-state magnetization vector is usually obtained by waiting for sufficient recovery time (idle time). Therefore, the process of waiting for the recovery of physical parameters is usually the most time-consuming part of quantitative myocardial magnetic resonance imaging technology. Taking into account the constraints of scanning time, such as breath-holding sequence will be restricted by breath-holding time, free breathing sequence needs to balance the scanning time with the above-mentioned waiting for the physical parameters to approach the steady-state time; a trade-off must be made between the degree of magnetization vector recovery and the scanning time.

In addition, another outstanding feature of the steady-state magnetization vector is the uncertainty of its recovery time. If the recovery time is set to several heart beats, it will inevitably be significantly affected by changes in heart rate. If the recovery time is set to a few seconds, since it is finally realized by an integer multiple of the heart rate converted from the real-time heart rate, there is still the problem of inconsistency between the steady-state magnetization vectors that need to be repeatedly obtained, which indirectly reflects the difference in heart rate. Impact. If you want to further reduce the sensitivity to heart rate differences, you have to set a longer recovery time, which will inevitably further reduce the scanning efficiency.

Therefore, there is an urgent need for a new quantitative myocardial magnetic resonance imaging method to at least partially solve the above problems.

Summary of the invention

The present invention is proposed in consideration of the above-mentioned problems.

According to one aspect of the present invention, there is provided a quantitative myocardial magnetic resonance imaging method, including:

In the first cardiac beat, when the flip angle of the data acquisition radio frequency pulse is equal to the first flip angle, the first image signal used to generate the first image is collected until the first image signal can fill the first image signal. The k-space corresponding to the image, wherein the first flip angle is less than or equal to a first threshold;

In the case that the flip angle of the data acquisition radio frequency pulse is equal to the second flip angle, after the preparation pulses with different pulse parameters are used to complete the preparation of the magnetization vector, the data collected for generating at least two images can respectively fill the at least two At least two image signals of k-space corresponding to the images, wherein the second flip angle is greater than a second threshold and less than a third threshold, and the second threshold is greater than the first threshold;

Determine the magnetic resonance quantitative parameters according to all the image signals, the pulse parameters of the preparation pulse corresponding to each image signal, the first flip angle and the second flip angle; and

A quantitative myocardial magnetic resonance image is generated according to the magnetic resonance quantitative parameter.

Exemplarily, the value range of the first threshold is 1 to 5 degrees.

Exemplarily, the pulse parameter includes the delay time between the preparation pulse and the time of data collection or the time length of the preparation pulse.

Exemplarily, the preparation pulse is a saturation pulse, and the acquisition of at least two image signals that can respectively fill up the k-space corresponding to the at least two images and used to generate the at least two images respectively includes:

In the m1th heartbeat, after using the saturation pulse with a delay time of Tsat _m1 , the control acquisition based on the respiratory navigation signal is used to generate the m1th image signal of the m1th image, where Tsat _{m1 is} not equal to the saturation pulse corresponding to other image signals The delay time of m1 is an integer not equal to 1;

In the m2th heartbeat, after using the saturation pulse with a delay time of Tsat _m2 , the control acquisition based on the respiratory navigation signal is used to generate the m2th image signal of the m2th image, where Tsat _{m2 is} not equal to the saturation pulse corresponding to other image signals The delay time of m2 is an integer not equal to 1 and m1.

Exemplarily, the collecting at least two image signals that can respectively fill up the k-space corresponding to the at least two images and are used to generate the at least two images respectively further includes:

In the m′th heartbeat, after using the saturation pulse with a delay time of Tsat _m1 or Tsat _m2 , the control based on the respiratory navigation signal is used to generate an image corresponding to the saturation pulse and can be refilled and saturated. The image signal of the k-space corresponding to the image corresponding to the pulse, m'is an integer not equal to 1, m1, and m2.

Exemplarily, the determining the magnetic resonance quantitative parameter includes determining the magnetic resonance quantitative parameter T ₁ according to the following formula,

Among them, IMG _i and Tdel _i respectively represent the delay time of the i-th image signal and its corresponding saturation pulse, FAi represents the flip angle corresponding to the i-th image signal, A represents the proton density to be determined, i=1, m1, m2, wherein the delay time of the first image signal IMG saturation pulse corresponding to _{a 1} Tdel is infinite.

Exemplarily, the Tsat _m1 is 90% to 100% of the maximum time interval Tmax allowed by the system, and the Tsat _m2 is 35% to 75% of the Tmax.

Illustratively, the preparation pulse is an inversion pulse or pulses T ₂ weighting.

Exemplarily, the data collection radio frequency pulse is a destruction gradient echo sequence, a balanced steady-state free precession sequence, a spin echo sequence or a plane echo sequence.

Exemplarily, in each heartbeat, before collecting the image signal in the heartbeat, a fat pressure operation is performed.

According to another aspect of the present invention, there is also provided a device for quantitative myocardial magnetic resonance imaging, including a processor and a memory, wherein computer program instructions are stored in the memory, and the computer program instructions are executed by the processor. It is used to execute the above quantitative myocardial magnetic resonance imaging method during operation.

According to another aspect of the present invention, there is also provided a storage medium on which program instructions are stored, and the program instructions are used to execute the above quantitative myocardial magnetic resonance imaging method during operation.

According to the quantitative myocardial magnetic resonance imaging method, device and storage medium of the embodiments of the present invention, steady-state magnetization vector data is collected when the flip angle of the data collection radio frequency pulse is small. Therefore, without waiting in the idle heartbeat, the steady-state magnetization vector data collection can be completed. Significantly improve the efficiency of data collection, and thus the imaging speed of quantitative myocardial magnetic resonance images. In addition, the quantitative myocardial magnetic resonance imaging scheme can be applied to various applications that need to collect steady-state magnetization vector data.

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, it can be implemented in accordance with the content of the description, and in order to make the above and other objectives, features and advantages of the present invention more obvious and understandable. In the following, specific embodiments of the present invention are specifically cited.

Description of the drawings

By describing the embodiments of the present invention in more detail with reference to the accompanying drawings, the above and other objectives, features and advantages of the present invention will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings, the same reference numerals generally represent the same components or steps.

Fig. 1 and Fig. 2 respectively show magnetization vector evolution curves corresponding to different heart rates in the data collection process of a small flip angle according to an embodiment of the present invention;

Fig. 3 shows a schematic flowchart of a quantitative myocardial magnetic resonance imaging method according to an embodiment of the present invention;

Fig. 4 shows a schematic diagram of an imaging sequence according to an embodiment of the present invention;

Figure 5a shows a 3D image of the left ventricle T ₁ of the present invention according to one embodiment;

Figure 5b shows the image of the image in the second row and third column of Figure 5a along the dotted line of view; and

5c shows a histogram in Figure 5a of _a 3D left ventricular myocardium value T.

detailed description

In order to make the objectives, technical solutions and advantages of the present invention more obvious, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. It should be understood that the present invention is not limited by the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present invention.

As mentioned earlier, the acquisition of steady-state magnetization vectors is an indispensable part of quantitative myocardial magnetic resonance imaging. It can be understood that the data acquisition RF pulse will cause the net magnetization vector to deviate from the main magnetic field direction. The angle at which the net magnetization vector deviates from the direction of the main magnetic field under the action of the data acquisition radio frequency pulse can be called the flip angle of the data acquisition radio frequency pulse. In the data acquisition operation, the flip angle of the data acquisition radio frequency pulse determines the size of the signal that can be collected, that is, the projection size of the magnetization vector on the plane (x-y plane) perpendicular to the direction of the main magnetic field. If the magnetization vector before the flip is the same, the larger the flip angle, the larger the projection on the x-y plane, and the larger the collected signal. The smaller the projection in the original parallel direction of the main magnetic field, the longer it takes to restore the steady-state magnetization vector. Therefore, when the flip angle of the data acquisition RF pulse is small, although the signal that can be collected is small, the magnetization vector returns to the steady state faster.

Fig. 1 and Fig. 2 respectively show the evolution curves of magnetization vectors corresponding to different heart rates during the data collection process with a small flip angle according to an embodiment of the present invention. Under particular, FIG. 1 and FIG. 2 shows a small flip angle acquired RF pulse in T ₁ is typical of normal myocardium value 3T 1550ms and the data (e.g., 2 degrees), 7 consecutive magnetization vectors within heartbeat Evolution curve. Among them, the abscissa is the number of heart beats, and the ordinate is the percentage of the current magnetization vector to the steady-state magnetization vector. As shown in Figure 1 and Figure 2, when the heart rate is less than 90 beats per minute, the magnetization vector can be restored to more than 95% of the steady-state magnetization vector during the data collection process of continuous heart beats. When the heart rate exceeds 90 beats per minute or even as high as 120 beats per minute, the magnetization vector can still recover to more than 96% of the steady-state magnetization vector during the data collection process with every other heart beat. Therefore, data collection with a small flip angle can meet the demand for steady-state magnetization vector collection in quantitative myocardial magnetic resonance imaging methods.

The quantitative myocardial magnetic resonance imaging method according to the embodiment of the present invention uses the above-mentioned principle to collect steady-state magnetization vector data under the condition that the data collection radio frequency pulse generates a small flip angle. The data acquisition operation with a small flip angle has very little disturbance to the magnetization vector. After data collection is completed, the magnetization vector can quickly return to a steady state within one or two heart beats, so as to realize the collection of steady-state magnetization vector data of continuous heart beats.

The quantitative myocardial magnetic resonance imaging method according to the embodiment of the present invention can be applied to a two-dimensional quantitative myocardial imaging method. It can realize segmented data collection, improve spatial resolution and avoid the influence of heart rate variability. This method can also be applied to the three-dimensional quantitative myocardial magnetic resonance imaging method, and can greatly improve the scanning efficiency. In addition, the method can also be applied to other applications that need to collect steady-state magnetization vectors, such as three-dimensional free-breathing quantitative parameter T ₁ and T ₂ combined imaging technology.

FIG. 3 shows a schematic flowchart of a quantitative myocardial magnetic resonance imaging method 300 according to an embodiment of the present invention. As shown in FIG. 3, a quantitative myocardial magnetic resonance imaging method 300 includes the following steps.

In step S310, in the first cardiac beat, when the flip angle of the data collection radio frequency pulse is equal to the first flip angle, collect a first image signal for generating a first image until the first image signal can fill all In the k-space corresponding to the first image, the first flip angle is less than or equal to a first threshold.

It can be understood that the signal acquisition operation can be based on the control of the ECG gating signal and the respiratory navigation signal.

The signal acquisition operation can be based on an electrocardiogram (ECG). The electrocardiogram can be obtained by attaching electrodes to the surface of the subject's chest skin and using an electrocardiogram monitoring device. In an electrocardiogram, the time interval between two R waves is called the beat (Beat), that is, the cardiac cycle. The next heart beat can be determined by detecting the R wave. Each image signal in the imaging sequence is collected in a cardiac beat. It can be understood that the image signal is used to generate a corresponding magnetic resonance image.

In each heartbeat, according to the ECG gating signal, determine the time to collect the image signal. Since image signal acquisition needs to be performed when the heart is relatively stationary, such as a moment in the end of diastole to obtain optimal heart motion compensation, there is only a small period of time in each cardiac beat suitable for data acquisition. After the time period Ttrigger has elapsed since the R peak, the image signal starts to be collected. The electrocardiogram gating technology can make the collected image signal less interfered by heart movement. It can be understood that the time period Ttrigger can be set by the scanner based on experience, and it can be 100-800 ms.

According to the embodiment of the present invention, the image signal is also collected based on the control of the respiratory navigation signal. By monitoring the change of the position of the thoracic diaphragm with the breathing movement, the position of the heart with the breathing movement can be estimated indirectly. It is expected that the acquired image signal is acquired when the thoracic diaphragm is in the desired position.

A respiratory navigation signal (NAV) is collected during a short period of time before the time period Ttrigger begins to elapse from the R peak of the ECG gated signal. According to the respiratory navigation signal, it is determined whether the current moment meets the predetermined condition, that is, whether the thoracic diaphragm is at the desired position at the current moment. In one example, after acquiring the respiratory navigation signal, the image signal is acquired. According to the collected respiratory navigation signal, it is determined whether the collected image signal meets the requirements of respiratory motion compensation, that is, it is determined whether the image signal collected in the heartbeat is valid. Therefore, it is decided whether to re-execute the acquisition operation or skip to the next signal acquisition operation. In the subsequent imaging processing, only valid image signals are used, and invalid image signals are ignored. In another example, after the respiratory navigation signal (NAV) is collected, it is determined whether the current moment meets the predetermined condition according to the respiratory navigation signal. In the case that it is determined that the current moment meets the predetermined condition according to the respiratory navigation signal, the image signal acquisition operation is performed until the signal acquisition operation of this step is completed.

Using respiratory navigation technology, subjects can breathe freely during quantitative myocardial magnetic resonance imaging. It also expands the imaging field of view and improves the spatial resolution of the image.

Optionally, the data collection radio frequency pulse used to collect the data is spoiled gradient echo (SPGR), balanced steady state free precession (bSSFP), spin echo sequence (Spin Echo, SE) or Planar Echo Sequence (EPI), any radio frequency pulse that can be used for magnetic resonance imaging. According to needs, a suitable data reading method is preferably adopted, which can significantly reduce the requirement for the uniformity of the magnetic field intensity during the imaging process, so that the solution can be applied to a high-field (such as 3T) magnetic resonance system.

In the first cardiac beat and in the case where the flip angle of the data acquisition radio frequency pulse is equal to the first flip angle, the first image signal used to generate the first image is collected until the first image signal can fill the corresponding first image k-space. The first flip angle may be preset, which is less than the first threshold. Optionally, the first threshold may be 1 degree to 5 degrees. In one embodiment, the first flip angle ranges from 1 degree to 5 degrees. As mentioned earlier, the value of the flip angle of the data acquisition RF pulse has an impact on both the size of the acquired signal and the recovery time of the magnetization vector. The first threshold is in the above-mentioned value range and can take into account the above two factors. That is, it can ensure that the acquired signal is sufficient to generate a quantitative myocardial magnetic resonance image, and it can ensure that the recovery time of the magnetization vector is short. As a result, while ensuring the imaging quality, the imaging speed, accuracy and precision are improved.

As mentioned above, when the flip angle of the data acquisition radio frequency pulse is small, it is possible to collect steady-state magnetization vector data in continuous heartbeats, without the need for idle heartbeats to wait for the magnetization vector to recover. In the embodiment of the present invention, when the flip angle of the data collection radio frequency pulse is small, the steady state magnetization vector data—the first image signal is collected.

The k-space is the data space where the acquisition operation is performed. The k-space can be divided into several segments. The image signal used to fill each segment can be collected in one cardiac beat. The image signals collected by several heartbeats can be combined to fill the complete k-space for image reconstruction. Here, the heartbeat that collects the first image signal is collectively referred to as the first heartbeat, which may be one or more heartbeats. The first image signals collected by all the first heartbeats jointly fill up the k-space corresponding to the first image. Thus, the first image can be reconstructed using the first image signal.

Step S320, in the case that the flip angle of the data acquisition radio frequency pulse is equal to the second flip angle, after the preparation pulses with different pulse parameters are used to complete the preparation of the magnetization vector, the data collected for generating at least two images, which can respectively fill the At least two image signals of the k-space corresponding to the at least two images, wherein the second flip angle is greater than a second threshold and less than a third threshold, and the second threshold is greater than the first threshold.

Similar to acquiring the first image signal, the image signal acquisition in this step S320 may also be based on the control of the ECG gating signal and the respiratory navigation signal. For brevity, I won't repeat them here.

In this step, the selection of the flip angle of the data acquisition pulse can comprehensively consider the acquisition speed, signal-to-noise ratio, and sensitivity to many factors such as motion and magnetic field uniformity. The second flip angle can be preset based on the consideration of the above factors. The second flip angle is greater than the second threshold and less than the third threshold. It can be understood that the magnetization vector weighted by the physical parameter is collected in this step, rather than the steady-state magnetization vector. In order to collect a more ideal magnetization vector, the second threshold is greater than or even far greater than the first threshold. In other words, the second flip angle is greater than the first flip angle.

In one example, SPGR is used under 3T magnetic field strength, and the flip angle of the data collection radio frequency pulse can take any value between 15-20 degrees. SPGR has an inherent T ₁ weighting characteristic according to its flip angle. SPGR is insensitive to the inhomogeneity of the magnetic field, has no memory effect, and basically does not have a preparation process approaching a steady state. It is more suitable for situations where data collection needs to be completed in segments, that is, it is more suitable for three-dimensional data scanning.

In another example, using bSSFP under 3T magnetic field strength, the flip angle of the data acquisition RF pulse can be higher, for example, any value between 30-40 degrees.

Quantitative myocardial magnetic resonance imaging needs to obtain multiple different parameter weighted image signals corresponding to the same anatomical structure of the subject, that is, corresponding to sampling points at different recovery times on the physical parameter recovery curve. It will be appreciated, may include a physical parameter MRI _{T 1,} T _2, T 1rho _T 2rho and the like. Taking the physical parameter T ₁ as an example, it is usually necessary to collect several different T ₁ weighted image signals. These T ₁ weighted image signals and the steady-state magnetization vector image signal collected in step S310 are used to fit a complete T ₁ recovery curve. , To obtain T ₁ value. Therefore, in this step, by adjusting the pulse parameters of the preparation pulse, the magnetization vectors corresponding to different weighting parameters are obtained after the preparation pulses with different pulse parameters are used to complete the preparation of the magnetization vector, that is, the magnetization vector used for data acquisition. Thus, at least two image signals corresponding to different weighting parameters are collected.

To achieve quantitative myocardial magnetic resonance imaging with relatively high resolution, each image signal acquisition may require multiple heart beats to complete. Specifically, for an image signal used to generate an image corresponding to a certain weighting parameter, multiple heartbeats may be required to collect, so that the collected image signal can fill up the k-space corresponding to the image.

Even if low-resolution imaging technology is used, that is, the above-mentioned image signal acquisition used to generate the image corresponding to a certain weighting parameter is completed in a single heartbeat, due to the demand of quantitative calculation, multiple heartbeats are still needed to obtain different parameters Weighted image signal.

In an example, the signal acquisition operation in this step S320 may acquire multiple imaging sequences in a cyclic manner. Once in each cycle, an imaging sequence is acquired. Each imaging sequence includes at least two image signals, and the two image signals respectively correspond to different parameter weights, that is, acquired after preparing pulses with different pulse parameters. Repeat the acquisition of the above-mentioned imaging sequence until the acquired image signals can fill the respective corresponding k-space.

In another example, the image signal corresponding to a certain parameter weight is first collected until the image signal can fill its corresponding k-space; then image signals corresponding to other parameter weights are also collected separately until each can fill its corresponding K-space. In this example, the acquisition of the image signal corresponding to a parameter weight can be completed in a continuous heartbeat.

It can be understood that the aforementioned step S310 and step S320 may use parallel sampling technology and any other k-space down-sampling technology.

In step S330, the quantitative magnetic resonance parameters are determined according to all the image signals collected in steps S310 and S320, the pulse parameters of the preparation pulse corresponding to each image signal, the first flip angle and the second flip angle. As mentioned earlier, before acquiring each image signal, a preparation pulse can be applied. The weight of physical parameters can be changed by applying preparation pulses of different pulse parameters. The quantitative parameters of magnetic resonance are determined by fitting image signals corresponding to different parameter weights. Various data fitting methods can be used to determine the physical parameters, which are not limited in the embodiment of the present invention.

Step S340, generating a quantitative myocardial magnetic resonance image according to the magnetic resonance quantitative parameters determined in step S330. Those of ordinary skill in the art can understand the specific implementation of this step, and will not be repeated here for brevity.

According to the above-mentioned imaging method 300 of the embodiment of the present invention, the steady-state magnetization vector data is collected when the flip angle of the data collection radio frequency pulse is small. Thus, without waiting in the idle heartbeat, the acquisition of steady-state magnetization vector data can be completed. Significantly improves the collection efficiency of magnetization vector data, thereby increasing the imaging speed of quantitative myocardial magnetic resonance images. Correspondingly, the aforementioned imaging method 300 can also improve the accuracy, precision, and temporal and spatial resolution of quantitative cardiac magnetic resonance imaging. In addition, the quantitative myocardial magnetic resonance imaging scheme can be applied to various applications that need to collect steady-state magnetization vector data, and has strong universality.

FIG 4 shows a quantitative T ₁ cardiac magnetic resonance imaging sequences according to one embodiment of the present invention. In this embodiment, the preparation pulse used is a saturation pulse. It can be understood that this is only an example, not a limitation of the present invention. For example, preparation pulses may also be any suitable pulse signal inversion pulse or pulses, etc. T ₂ weighting. In each heartbeat shown in FIG. 4, based on the control of the ECG gating signal and the respiratory navigation signal, after the time period Ttrigger has elapsed since the R peak, different signal acquisition operations are performed. The image signal acquisition process is the k-space filling process in magnetic resonance imaging.

As shown in FIG. 4, in the first cardiac beat, when the flip angle (FA) of the data collection radio frequency pulse is equal to 2 degrees, the first image signal IMG _{1 that is} judged to meet the predetermined condition at the current moment is collected according to the respiratory navigation signal. The first image signal IMG ₁ is a steady-state image signal. In this first heart beat, no preparation pulse was used.

In the first heartbeat, it can be determined that the current moment meets the predetermined conditions according to the respiratory navigation signal. In one example, before the first heartbeat, there are heartbeats in which it is determined that the current moment does not meet the predetermined condition according to the respiratory navigation signal. Therefore, optionally, before the first heartbeat, the following operations are further included: in a heartbeat, if it is determined that the current time does not meet the predetermined condition according to the breathing navigation signal, wait for the next heartbeat to perform the judgment again based on the breathing navigation signal Operate and execute the corresponding image signal acquisition operation of the current heartbeat according to the judgment result. For the convenience of description, it is said that the heartbeat that does not meet the predetermined conditions at the current moment according to the respiratory navigation signal is called A heartbeat. In A heartbeat, no image signal acquisition is performed. In the next heartbeat of A heartbeat, it is again judged whether the current moment meets the predetermined conditions according to the breathing navigation signal. If it still does not meet, then continue to wait. Until a certain heartbeat is judged according to the breathing navigation signal that the current moment meets the predetermined condition, the heartbeat is the first heartbeat. As described above, in the first cardiac beat, when it is determined that the current moment meets the predetermined condition according to the respiratory navigation signal, the first image signal IMG _{1 is} collected. In another example, the image signal may be collected in the A heartbeat before the first heartbeat. It is only judged based on the breathing navigation signal that the current moment does not meet the predetermined conditions, that is, the image signal collected in the A heartbeat is invalid. At this time, the image signal is reacquired until the first image signal IMG _{1 that is} judged to meet the predetermined condition at the current moment according to the respiratory navigation signal is collected.

It can be understood that there may be multiple first heart beats, such as N, where N is an integer greater than one. Among the multiple first heart beats, collect the first image signals IMG ₁ respectively used to fill different segments of the k-space corresponding to the first image, until the collected first image signal IMG ₁ can fill the k -space.

After acquiring the first image signal, IMG ₁ , in the case that the flip angle (FA) of the data acquisition radio frequency pulse is equal to 15 degrees, the acquisition can fill at least two images (3 in this embodiment) respectively corresponding to At least two image signals of the k-space used to generate the at least two images respectively. The specific process is detailed as follows.

In the m1-th heartbeat, where m1 is an integer not equal to 1, and when the flip angle of the data acquisition radio frequency pulse is equal to the second flip angle, the saturation pulse SAT with a delay time of Tsat _m1 is first used. As shown in FIG. 4, the delay time of the saturation pulse is the time interval between the saturation pulse and the moment when the image signal is acquired. Tsat _{m1 is} not equal to the delay time of the saturation pulse corresponding to other image signals. After the saturation pulse SAT with a delay time of Tsat _m1 is used, the control acquisition based on the respiratory navigation signal is used to generate the m1-th image signal IMG _m1 .

Similar to the m1th heartbeat, in the m2th heartbeat, where m2 is an integer that is not equal to 1 and m1, after using the saturation pulse with a delay time of Tsat _m2 , and the control acquisition based on the breathing navigation signal is used to generate the m2th image The m2 image signal IMG _m2 . Tsat _{m2 is} not equal to the delay time of the saturation pulse corresponding to other image signals.

Similar to the m1th heartbeat, in the m3th heartbeat, where m3 is an integer that is not equal to 1, m1 and m2, after using the saturation pulse with a delay time of Tsat _m3 , and the control acquisition based on the breathing navigation signal is used to generate the first The m3 image signal IMG _m3 of the m3 image. Tsat _{m3 is} not equal to the delay time of the saturation pulse corresponding to other image signals.

Optionally, as shown in FIG. 4, the signal acquisition operation of the m1-th heartbeat may be repeated multiple times (for example, N times) until the m1-th image signal IMG _m1 can fill up the k-space corresponding to the m1-th image. After the acquisition of the m1th image signal is completed, the signal acquisition operation of the m2th heartbeat is repeated multiple times (for example, N times) until the m2th image signal IMG _m2 can fill up the k-space corresponding to the m2th image. After the acquisition of the m2 image signal IMG _{m2 is} completed, the signal acquisition operation of the m3 heart beat is repeated multiple times (for example, N times) until the m3 image signal IMG _m3 can fill the k-space corresponding to the m3 image.

Alternatively, the m1-th image signal IMG _m1 , the m2-th image signal IMG _m2, and the m3-th image signal IMG _{m3 may} be regarded as one imaging sequence. Acquire multiple such imaging sequences in a cyclic manner. In other words, in the m1-th heartbeat, first collect the m1-th image signal IMG _m1 ; then in the m2-th heartbeat, collect the m2-th image signal IMG _m2 ; in the m3-th heartbeat, collect the m3-th image signal IMG _m3 . Thus, the acquisition of an imaging sequence is completed. The acquisition process of the foregoing imaging sequence is repeated until the m1 image signal IMG _m1 , the m2 image signal IMG _m2, and the m3 image signal IMG _m3 can respectively fill the corresponding k-space.

At heartbeat m1, m2-m3 heart beat and the heart beat, pulse with saturated realized T ₁ weighting. Among them, the delay time of the saturation pulse is different, and the weight of T ₁ is different. Therefore, in these three different heartbeats, corresponding sampling points are obtained. The delay time of the saturation pulse can be any value from the minimum time interval allowed by the system to the maximum time interval allowed by the system. It will be appreciated, in this embodiment, three different collected here a T ₁ weighted image signal. Alternatively, it may be collected only two or more than three T ₁ weighted image signal.

Optionally, the delay time Tsat _m1 of the saturation pulse in the m1-th cardiac beat is 90% to 100% of the maximum time interval Tmax allowed by the system. The sum of the length of time occupied by the signal operation (for example, the breathing navigation signal NAV) during the time period Ttrigger and the hardware response delay time can be determined first. Then calculate the difference between the time period Ttrigger and the sum, which is the maximum time interval Tmax allowed by the system. The delay time Tsat _m2 of the saturation pulse in the m2 heartbeat is 35% to 75% of the maximum time interval Tmax allowed by the system. In the embodiment shown in FIG. 4, Tsat _m1 is equal to Tmax, Tsat _m2 is equal to Tmax*3/4, and Tsat _m3 is equal to Tmax*1/2. Tmax, the longer the recovery time of the magnetization vector, also can be used for forming an image signal is stronger, the larger the ratio (SNR) of image signals obtained, the greater the weight of the weight of ₁ T. Using the above range of values for Tsat _m1 and Tsat _m2 can make the sampling points more reasonable distribution, so that the T1 value can be accurately estimated even when only a few sampling points are obtained. In addition, the above-mentioned value range also makes the longitudinal magnetization vector that can be used for data reading relatively large, thereby improving the signal-to-noise ratio of the signal, and obtaining an original weighted image of better quality.

Similar to the first heartbeat, before one or more of the m1th heartbeat, the m2th heartbeat, and the m3th heartbeat, there may be a heartbeat during which it is determined that the current moment does not meet the predetermined condition based on the respiratory navigation signal. Optionally, in the signal acquisition operation, before one or more of the m1th heartbeat, the m2th heartbeat, and the m3th heartbeat, the following operations are further included: in a heartbeat, the current time is not in accordance with the respiratory navigation signal. In the case of predetermined conditions, the image signal is collected and the collected image signal is invalidated, and the next heartbeat is waited to perform the judgment operation based on the respiratory navigation signal again and execute the corresponding image signal acquisition operation of the current heartbeat according to the judgment result. Alternatively, in a heartbeat, if it is determined that the current moment does not meet the predetermined condition based on the respiratory navigation signal, no image signal is collected. Wait for the next heartbeat and make a judgment based on the breathing navigation signal again in the next heartbeat, and perform corresponding operations according to the judgment result.

In the above-mentioned signal acquisition operation, image signals with different T ₁ weights (IMG _m1 , IMG _m2 and IMG _m3 ) are collected in the m1-th heartbeat, the m2-th heartbeat and the m3-th heartbeat respectively. It can be understood that the above sequence of the m1-th heartbeat to the m3th heartbeat is only an example, and is not a limitation of the present invention. These 3 heartbeats can be executed in any order without affecting the effect of the technical solution of the present application.

Optionally, the above-mentioned signal acquisition operation further includes at least one of the following operations: in the case where the flip angle (FA) of the data acquisition radio frequency pulse is equal to 15 degrees, the delay time is Tsat _m1 and Tsat _{m2 in the} m′th heartbeat. Or after the saturation pulse of Tsat _m3 , based on the control of the respiratory navigation signal, the image signal used to generate the image corresponding to the saturation pulse and capable of refilling the k-space corresponding to the image corresponding to the saturation pulse is collected again, m ′ Is an integer not equal to 1, m1, m2, and m3. For brevity, the image signal collected in the m'th heartbeat is called the m'th image signal. This operation is repeated heartbeat of m1, m2-m3 heartbeat or the heartbeat of the operation, thereby obtaining a T ₁ weighted the same sampling point. Finally, the parameter T _{1 is} determined based on all the collected m'th image signals and other image signals.

In one example, in the m′th heartbeat, after using the saturation pulse with a delay time of Tsat _m1 , the m1 image signal IMG _m1 corresponding to the saturation pulse is controlled based on the respiratory navigation signal to be collected again. Finally, the parameter T _{1 is} determined according to all the collected m1 image signals and other image signals. In the above example, all input signal models of the m1-th image signal IMG _m1 collected in the m1-th heartbeat and the m′th heartbeat are fitted to determine the parameter T ₁ .

The effect of the above technical solution is equivalent to averaging the noise of the sampling point (for example, the m1-th image signal IMG _m1 ), thereby reducing the fitting deviation. In short, the signal acquisition operation can be improved calculation accuracy of the parameters T _1, thereby improving image quality.

In the above embodiment, it is described that the preparation pulse is a saturation pulse and the image signal with different T ₁ weights is collected by changing its pulse parameter—delay time. It can be understood that in different specific applications, this can also be achieved by using other pulse parameters for preparing the pulse. For example, the length of time to prepare the pulse.

Through the above-mentioned optimized imaging sequence, the above-mentioned T ₁ quantitative myocardial magnetic resonance imaging method 300 has high scanning efficiency and unlimited imaging resolution, and can obtain T ₁ quantitative myocardial magnetic resonance images with strong accuracy and precision.

As shown in FIG. 4, before the image signals (IMG ₁ , IMG _m1 , IMG _m2 , and IMG _m3 ) are acquired in the signal acquisition operation, the fat pressure operation (FS) may be performed separately. The liposuction operation helps to reduce breathing artifacts and significantly improves image quality.

According to an embodiment of the present invention, the parameter T ₁ can be determined according to the delay time Tsati, the first flip angle and the second flip angle of the i-th image signal and the preparation pulse corresponding to the i-th image signal, where i=1, m1, m2. And when i=1, Tsat1 used for data fitting is infinite.

In an example, the parameter T ₁ is determined according to the following formula,

Among them, IMG _i and Tdeli are respectively the delay time of the i-th image signal obtained by the signal acquisition operation and its corresponding saturation pulse. FAi represents the flip angle corresponding to the i-th image signal. A represents the proton density to be determined. T ₁ and A are unknown in this formula. The two can be determined by fitting according to the above parameters. According to this formula, the parameter T ₁ can be determined more accurately, thereby generating a more accurate T ₁ quantitative myocardial magnetic resonance image.

It can be understood that when more image signals, such as IMG _m3 , are collected in the above-mentioned signal collection operation, then i in the above-mentioned formula can also be equal to m3.

FIG 5a shows _an image of the 3D image of the left ventricle from the same T ₁ of a subject with one embodiment of the present invention and the T. Fig. 5b shows the image of the image in the second row and third column in Fig. 5a along the dotted line of view. In Figure 5c shows a histogram in Figure 5a of _a 3D left ventricular myocardium value T.

The data in Figure 5a comes from healthy subjects. As shown in the histogram shown in Fig. 5c, the numerical distribution of the parameter T ₁ presents a normal distribution. Therefore, the quantitative myocardial magnetic resonance image generated according to the embodiment of the present invention ideally reflects the state of the subject's myocardial tissue.

According to yet another aspect of the present invention, a device for quantitative myocardial magnetic resonance imaging is also provided. The system includes a processor and memory. The memory stores computer program instructions for implementing each step in the method for quantitative myocardial magnetic resonance imaging according to an embodiment of the present invention. The processor is configured to run computer program instructions stored in the memory to execute corresponding steps of the quantitative myocardial magnetic resonance imaging method according to the embodiment of the present invention.

According to another aspect of the present invention, there is also provided a storage medium on which program instructions are stored, and when the program instructions are run by a computer or a processor, the computer or the processor executes the embodiments of the present invention. The corresponding steps of the quantitative myocardial magnetic resonance imaging method are used to implement the corresponding modules in the quantitative myocardial magnetic resonance imaging apparatus according to the embodiment of the present invention. The storage medium may include, for example, the storage component of a tablet computer, a hard disk of a personal computer, a read only memory (ROM), an erasable programmable read only memory (EPROM), a portable compact disk read only memory (CD-ROM), USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more computer-readable storage media.

In the instructions provided here, a lot of specific details are explained. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and technologies are not shown in detail, so as not to obscure the understanding of this specification.

Similarly, it should be understood that in order to simplify the present invention and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure , Or in its description. However, the method of the present invention should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly stated in each claim. To be more precise, as reflected in the corresponding claims, the point of the invention is that the corresponding technical problems can be solved with features less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are thus explicitly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

Those skilled in the art can understand that in addition to mutual exclusion between the features, any combination of all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and any method or device disclosed in this manner can be used. Processes or units are combined. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments means that they are within the scope of the present invention. Within and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

It should be noted that the word "comprising" does not exclude the presence of elements or steps not listed in the claims. The use of the words first, second, and third does not indicate any order. These words can be interpreted as names. The characters one, two, and three are equivalent to the corresponding numbers 1, 2, 3, etc. respectively. Therefore, the first, second, and third, etc., are the same as the corresponding first, second, and third, etc., respectively.

The above are only specific implementations or descriptions of specific implementations of the present invention. The protection scope of the present invention is not limited thereto. Any person skilled in the art can easily fall within the technical scope disclosed by the present invention. Any change or replacement should be included in the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (12)

1. A quantitative myocardial magnetic resonance imaging method includes:

   In the first cardiac beat, when the flip angle of the data acquisition radio frequency pulse is equal to the first flip angle, the first image signal used to generate the first image is collected until the first image signal can fill the first image signal. The k-space corresponding to the image, wherein the first flip angle is less than or equal to a first threshold;

   In the case that the flip angle of the data acquisition radio frequency pulse is equal to the second flip angle, after the preparation pulses with different pulse parameters are used to complete the preparation of the magnetization vector, the data collected for generating at least two images can respectively fill the at least two At least two image signals of k-space corresponding to the images, wherein the second flip angle is greater than a second threshold and less than a third threshold, and the second threshold is greater than the first threshold;

   Determine the magnetic resonance quantitative parameters according to all the image signals, the pulse parameters of the preparation pulse corresponding to each image signal, the first flip angle and the second flip angle; and

   A quantitative myocardial magnetic resonance image is generated according to the magnetic resonance quantitative parameter.
2. The method according to claim 1, wherein the value range of the first threshold is 1 to 5 degrees.
3. The method of claim 1, wherein the pulse parameter includes a delay time between the preparation pulse and the time of data collection or the time length of the preparation pulse.
4. The method according to claim 1, wherein the preparation pulse is a saturation pulse, and the acquisition can respectively fill up the k-space corresponding to the at least two images and is used to generate the at least two images. The at least two image signals include:

   In the m1th heartbeat, after using the saturation pulse with a delay time of Tsat _m1 , the control acquisition based on the respiratory navigation signal is used to generate the m1th image signal of the m1th image, where Tsat _{m1 is} not equal to the saturation pulse corresponding to other image signals The delay time of m1 is an integer not equal to 1;

   In the m2th heartbeat, after using the saturation pulse with a delay time of Tsat _m2 , the control acquisition based on the respiratory navigation signal is used to generate the m2th image signal of the m2th image, where Tsat _{m2 is} not equal to the saturation pulse corresponding to other image signals The delay time of m2 is an integer not equal to 1 and m1.
5. The method according to claim 4, wherein the collecting at least two image signals that can respectively fill up the k-space corresponding to the at least two images and used to generate the at least two images respectively further comprises:

   In the m′th heartbeat, after using the saturation pulse with a delay time of Tsat _m1 or Tsat _m2 , the control based on the respiratory navigation signal is used to generate an image corresponding to the saturation pulse and can be refilled and saturated. The image signal of the k-space corresponding to the image corresponding to the pulse, m'is an integer not equal to 1, m1, and m2.
6. The method according to claim 4, wherein said determining the magnetic resonance quantitative parameter comprises determining the magnetic resonance quantitative parameter T ₁ according to the following formula,

   

   Among them, IMG _i and Tdel _i respectively represent the delay time of the i-th image signal and its corresponding saturation pulse, F4i represents the flip angle corresponding to the i-th image signal, A represents the proton density to be determined, i=1, m1, m2, wherein the delay time of the first image signal IMG saturation pulse corresponding to _{a 1} Tdel is infinite.
7. The method according to any one of claims 4 to 6, wherein the Tsat _m1 is 90% to 100% of the maximum time interval Tmax allowed by the system, and the Tsat _m2 is 35% to 75% of the Tmax.
8. The method according to claim 1, wherein said pulse is an inversion pulse preparation or T ₂ weighting pulses.
9. The method of claim 1, wherein the data acquisition radio frequency pulse is a destroyed gradient echo sequence, a balanced steady state free precession sequence, a spin echo sequence, or a plane echo sequence.
10. 8. The method of claim 1, wherein, in each heartbeat, before collecting the image signal in the heartbeat, a fat pressure operation is performed.
11. A device for quantitative myocardial magnetic resonance imaging, comprising a processor and a memory, wherein computer program instructions are stored in the memory, and the computer program instructions are used to execute as claimed in claims 1 to 10. Quantitative myocardial magnetic resonance imaging method as described in any one of 10.
12. A storage medium storing program instructions on the storage medium, and the program instructions are used to execute the quantitative myocardial magnetic resonance imaging method according to any one of claims 1 to 10 during operation.

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