WO2020034676A1

WO2020034676A1 - Myocardial quantitative magnetic resonance imaging method and device, and storage medium

Info

Publication number: WO2020034676A1
Application number: PCT/CN2019/086400
Authority: WO
Inventors: 丁海艳; 郭瑞; 罗建文
Original assignee: 清华大学
Priority date: 2018-08-14
Filing date: 2019-05-10
Publication date: 2020-02-20
Also published as: CN109091145B; CN109091145A

Abstract

Disclosed are a myocardial quantitative magnetic resonance imaging method and device, and a storage medium. The method comprises: every other recovery time period, executing an image signal collection operation under the control of an electrocardiograph gating signal and a respiratory navigation signal; determining a parameter T1 according to a collected image signal and a delay time of a saturation pulse corresponding thereto; and generating a myocardial quantitative magnetic resonance image according to the parameter T1. The method can complete scanning when a subject breathes freely, without suspending breathing. In addition, an imaging field of view is allowed to be further extended, and a spatial resolution is improved. Furthermore, the internal registration of an original image is realized by means of performing complete interleaving segmented collection between all sampling points in a k-space, without subsequently performing additional image processing.

Description

Myocardial quantitative magnetic resonance imaging method, equipment and storage medium

Technical field

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

Background technique

MRI imaging of the human body using the phenomenon of MRI has been a common medical imaging examination.

The basic physical parameter T ₁ (spin lattice relaxation time, or longitudinal relaxation time) of nuclear magnetic resonance is a time constant describing the recovery of the longitudinal magnetization vector. T _{1 is} determined by the composition of the biological tissue and the existing structure and the magnetic field strength. Under a certain magnetic field strength, different tissues have specific T ₁ values. When biological tissues change, T ₁ also changes. Therefore, T ₁ can be used as a characteristic parameter to identify the characteristics of myocardial tissue.

The myocardial T ₁ quantitative magnetic resonance imaging technology developed in recent years directly measures the basic physical parameter T ₁ of magnetic resonance to achieve quantitative myocardial tissue evaluation.

In the existing techniques for quantitative cardiac T ₁ imaging of the myocardium, most of the compensation of breathing motion during scanning is performed by holding the breath. This technique requires more T ₁ weighted sampling points to be able to image and is sensitive to heart rate changes. The breath-holding requirement restricts the further improvement of imaging resolution and cannot be used for subjects with breath-holding difficulties (this is more common in patients with heart disease). Respiratory navigation can be used to break the breath-holding limit, and saturation saturation pulses can be used to achieve T ₁ weighting, which can reduce the dependence on heart rate changes. However, the existing techniques using respiratory navigation operations need to collect more sampling points. Therefore, there are problems of long scanning time and mismatch between different sampling points. In addition, the signal-to-noise ratio of some T ₁ weighted sampling points is relatively low, which affects the final T ₁ fitting quality. If the number of sampling points is reduced, the original weighted image must be filtered before fitting the parameters. It is even necessary to perform motion correction (such as registration) between the original weighted images to eliminate the negative impact of myocardial motion on imaging.

Therefore, a new myocardial quantitative magnetic resonance imaging technology is urgently needed to solve the above problems at least in part.

Summary of the Invention

The present invention has been made in consideration of the above problems.

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

Every recovery period, under the control of ECG gating signals and respiratory navigation signals, at least the following signal acquisition operations are performed:

In the first heartbeat, when it is determined according to the breathing navigation signal that the current moment meets a predetermined condition, collect a first image signal;

In the second heartbeat, after a saturation pulse with a delay time of Tsat2 is used, and when the current moment is determined to meet a predetermined condition according to the breathing navigation signal, a second image signal is acquired;

In the third heartbeat, a third image signal is acquired after a saturation pulse with a delay time of Tsat3 is used, and the current moment is determined to meet a predetermined condition based on the breathing navigation signal, where Tsat3- ≠ Tsat2;

Determine the parameter T ₁ according to the i-th image signal and the delay time Tsati of the saturation pulse corresponding to the i-th image signal, where i = 1, 2, 3, and when i = 1, Tsati is infinite;

A quantitative magnetic resonance image of the myocardium is generated based on the parameter T ₁ .

According to another aspect of the present invention, there is also provided a device for quantitative cardiac magnetic resonance imaging, including a processor and a memory, wherein the memory stores computer program instructions, and the computer program instructions are received by the processor. Runtime is used to perform the myocardial quantitative magnetic resonance imaging method described above.

According to still another aspect of the present invention, a storage medium is further provided, and program instructions are stored on the storage medium, and the program instructions are used to execute the foregoing myocardial quantitative magnetic resonance imaging method when running.

The myocardial quantitative magnetic resonance imaging method, device, and storage medium according to the embodiments of the present invention can complete a scan without the subject having to breathe out while the subject is breathing freely. It also allows to further expand the imaging field of view and improve the spatial resolution. In addition, the k-space is used to completely interleave segmented acquisitions between sampling points, thereby achieving the inherent registration of the original image without the need for additional image processing in the later stages.

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 according to the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more comprehensible. In the following, specific embodiments of the present invention are enumerated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will become more apparent by describing the embodiments of the present invention in more detail with reference to the accompanying drawings. The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the description. They are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation on the present invention. In the drawings, the same reference numbers generally represent the same components or steps.

FIG. 1 shows a schematic flowchart of a myocardial quantitative magnetic resonance imaging method according to an embodiment of the present invention;

FIG. 2 shows a quantitative image of parameter T ₁ according to an embodiment of the present invention;

Figure 3 shows an imaging sequence according to an embodiment of the invention;

FIG. 4 shows a T ₁ estimation curve according to an embodiment of the present invention;

FIG. 5 shows a first image signal to a third image signal of the same layer of heart in a short-axis perspective of a subject collected according to an embodiment of the present invention and a quantitative image of parameter T ₁ obtained by fitting;

FIG. 6 shows an imaging sequence according to another embodiment of the present invention;

Figure 7a shows a 3D image of the left ventricle T ₁ of the present invention according to one embodiment;

7b show an image of the image shown in FIG. 7a T ₁ at the major axis of viewing angle;

T ₁ image shown in FIG. 7c shows a histogram of Figure 7a in the left ventricle T _1; and

FIG. 8 shows a quantitative image of the parameter T ₁ after shortening the contrast agent using T ₁ according to an embodiment of the present invention.

detailed description

In order to make the objectives, technical solutions, and advantages of the present invention more obvious, an exemplary embodiment 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 paying any creative effort should fall within the protection scope of the present invention.

According to an embodiment of the present invention, a method for quantitative cardiac magnetic resonance imaging is provided. This method is a 3D free breathing quantitative myocardial parameter T ₁ imaging technique. This technology uses breathing navigation technology to achieve compensation for breathing movements. Through the use of saturation pulses, combined with sufficient T ₁ recovery time to obtain the ideal steady state magnetization vector, it is not sensitive to heart rate changes, and can achieve higher T ₁ fitting accuracy. The k-space staggered segmented acquisition method is used to achieve the intrinsic self-registration of the original image, without the need for post-processing such as registration and filtering of the original image, and without parameter correction. It can be used for high field strength (3T) 3D myocardial quantitative parameters T ₁ accurate measurement.

FIG. 1 shows a schematic flowchart of a myocardial quantitative magnetic resonance imaging method 100 according to an embodiment of the present invention. As shown in FIG. 1, the myocardial quantitative magnetic resonance imaging method 100 includes the following steps.

In step S110, a signal acquisition operation is performed under the control of the ECG gating signal and the respiratory navigation signal every recovery period.

This signal acquisition operation can acquire multiple imaging sequences in a cyclic manner. Every cycle, an imaging sequence is acquired. Each imaging sequence includes multiple image signals. In one example, each imaging sequence includes 3 image signals. k-space is the data space for magnetic resonance acquisition. Each time the image signal acquisition of an imaging sequence is completed, a segmented filling of k-space in magnetic resonance imaging is achieved. The imaging sequence needs to be acquired cyclically several times in order to fill the complete k-space for reconstruction of the image. It can be understood that the parallel sampling technique and the k-space down-sampling technique in any other manner can be adopted.

The signal acquisition operation is based on an electrocardiogram (ECG). The ECG can be obtained by attaching electrodes to the surface of the subject's chest skin and by using an ECG monitoring device. In an electrocardiogram, the time interval between two R waves is called a beat, which is the cardiac cycle. The next heartbeat can be determined by detecting the R wave. Each image signal in the imaging sequence is acquired separately during a cardiac cycle. In the above example where the imaging sequence includes three image signals, three heartbeats are needed to complete the signal acquisition.

There is an image signal in the imaging sequence that allows the longitudinal magnetization vector to fully recover to a steady state. For simplicity of description, it is referred to as a steady-state image signal for short. In order to enable the longitudinal magnetization vector to be completely recovered after the acquisition operation of the previous imaging sequence, before the acquisition of the steady-state image signal, a recovery period is set, such as n idle heartbeats, or called recovery heartbeats. During this recovery period, no image signal is collected and no operation is performed that may disturb the recovery process of the magnetization vector.

The aforementioned number of idle heart beats n can be determined according to the length of time that the magnetization vector is allowed to recover and the subject's heart rate. The time length N (seconds) that allows the magnetization vector to be restored can be set by the user in real time online, which indirectly determines the time position of the steady-state image signal on the T ₁ estimation curve. The larger N is, the more the magnetization vector is recovered. Therefore, more ideal steady-state data can be obtained, which is beneficial to improving the accuracy of the parameter T ₁ . However, the larger N, the longer the scanning time required for imaging. Therefore, it is necessary to set N based on both the scanning efficiency and the accuracy of the steady state value. In one example, the magnetic field strength is 3T, and the minimum idle time can be set to 6 seconds (ie, N = 6). This can guarantee the recovery of more than 95% of the magnetization vector. If the magnetic field intensity is 1.5T, or after the use of contrast agents shorten T _1, N can be reduced accordingly. By setting the time length N that allows the magnetization vector to recover instead of the number of idle heartbeats n in real time, it is possible to strip the association with the change in heart rate while ensuring that the signal returns to a steady state.

According to an embodiment of the present invention, the number of idle heart beats n ≧ N / (60 / HR), wherein the subject's heart rate is HR (heartbeat / minute), and the length of time allowed for the magnetization vector to recover is N seconds. Optionally, n takes the smallest integer greater than or equal to N / (60 / HR). The number of idle heartbeats determined by this formula can ensure that the magnetization vector can be fully recovered. Furthermore, the accuracy of the generated quantitative myocardial magnetic resonance images is guaranteed.

In each heartbeat, the time of acquiring the image signal is determined according to the ECG gating signal. After the time period Ttrigger has elapsed since the R peak, image signals are collected. The moment when the image signal is expected to be collected is the moment when the heart is relatively still, such as a moment at the end of the diastole. The ECG gating technology can make the acquired image signals less disturbed by cardiac motion. It can be understood that the time period Tgrigger can be set by the scanner according to experience.

According to an embodiment of the present invention, in each heartbeat, it is also determined whether to acquire an image signal according to a breathing navigation signal. By monitoring changes in the position of the pectoralis diaphragm with breathing motion, it is possible to indirectly estimate changes in the position of the heart with breathing motion. In the embodiment of the present invention, the respiratory navigation signal is collected within a short period of time (NAV) before the time period Trigrigger starts from the R peak of the ECG gating signal. According to the breathing navigation signal, it is determined whether the current time meets a predetermined condition, that is, whether the position of the pectoralis diaphragm at the current time is at a desired position. Therefore, it is judged whether the image signal collected after the time period Trigrigger of the ECG gated signal starts to meet the requirements of respiratory motion compensation, that is, whether the image signal collected in the heartbeat is valid. Respiratory navigation technology is used to allow subjects to breathe freely during quantitative myocardial magnetic resonance imaging. It also expands the imaging field of view and improves the spatial resolution of the image.

Step S120, the delay time in accordance with the image signal acquired in step S110 respectively corresponding to saturation pulse to determine the parameters T _1. Before acquiring an image signal, a saturation pulse can be applied. The weight of the parameter T ₁ can be changed by applying saturation pulses of different delay times. For a heartbeat without applying a saturation pulse, the delay time corresponding to the image signal acquired in the heartbeat can be set to an infinite saturation pulse. The use of a saturation pulse reduces the dependence of the image signal on changes in heart rate.

In this step, different signal models can be used to fit the parameter T ₁ based on the sampling points (ie, image signals).

Step S130, the step S120 in accordance with the determined parameter T ₁ generating a magnetic resonance image of myocardial quantitative. In this step, a quantitative magnetic resonance image of the myocardium can be generated according to the parameter T ₁ obtained by the fitting operation. Figure 2 shows an embodiment of the present invention, three parameters of a subject from _a T quantitative image. For each subject, choose a layer from the apex, heart, and heart base as the representative image.

According to the above-mentioned imaging method 100 of the embodiment of the present invention, for the subject's heart motion and breathing motion, compensation for the above motion is achieved through ECG gating and breathing navigation, thereby ensuring that the image signals are in the same breathing state and Collected on cardiac exercise cycles. The scan can be done while the subject is breathing freely without the need to hold his breath. It also allows to further expand the imaging field of view and improve the spatial resolution. In addition, in the above-mentioned imaging method 100, k-space is used to acquire samples in a completely staggered and segmented manner between sampling points, thereby realizing the intrinsic registration of the original image and eliminating the need for additional image processing at a later stage.

Figure 3 shows an imaging sequence according to an embodiment of the invention. It can be understood that a plurality of such imaging sequences are obtained in a circular manner in the embodiment of the present invention. In each imaging sequence, a total of 3 image signals were acquired. Within each heartbeat, under the control of the ECG gating signal and the respiratory navigation signal, different signal acquisition operations are performed to obtain an image sequence. The image signal acquisition process is the k-space filling process in magnetic resonance imaging.

As shown in FIG. 3, in the first heartbeat, when it is determined that the current time meets a predetermined condition according to the breathing navigation signal, a first image signal IMG _{1 is} collected. The first image signal IMG ₁ is a value in which the longitudinal magnetization vector is sufficiently restored to a steady state. That is, the first image signal IMG ₁ is the above-mentioned steady-state image signal.

Within this first heartbeat, no saturation pulse is used. It may be provided corresponding to a first image signal IMG _delay time infinity saturation pulse, i.e. Tsat1 is infinite.

It can be understood that, within the first heartbeat, it is determined according to the breathing navigation signal that the current time meets a predetermined condition. Prior to the first heartbeat, there may be a heartbeat during which the current moment is determined not to meet the predetermined conditions based on the breathing navigation signal. Therefore, optionally, in the signal acquisition operation, before the first heartbeat, the following operation is further included: in one 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 repeat A judgment operation is performed according to the breathing navigation signal, and a corresponding image signal acquisition operation of the current heartbeat is performed according to the judgment result. For the convenience of description, the heartbeat during which the current moment does not meet the predetermined conditions according to the breathing navigation signal is referred to as the A heartbeat. In A heartbeat, no image signal acquisition is performed. In the next heartbeat of the A heartbeat, it is determined again whether the current time meets a predetermined condition according to the breathing navigation signal. If it still does not match, then continue to wait. Until a certain heartbeat determines that the current time meets a predetermined condition according to the breathing navigation signal, the heartbeat is the first heartbeat. As described above, in the first heartbeat, when it is determined that the current time meets a predetermined condition according to the breathing navigation signal, the first image signal IMG _{1 is} acquired.

In the above scheme, in the A heartbeat before the first heartbeat, no image signal is collected. Therefore, it can be ensured that the magnetization vector collected in the first heartbeat is a value in its equilibrium state.

In the second heartbeat, a saturation pulse SAT with a delay time Tsat2 is used first. The saturation pulse can zero the magnetization vector. As shown in FIG. 3, the delay time of the saturation pulse is the time interval between the saturation pulse and the time when the image signal is collected. After using the saturation pulse SAT with a delay time of Tsat2, the second image signal IMG ₂ is acquired in a case where it is determined that the current time meets a predetermined condition according to the respiratory navigation signal.

Similar to the second heartbeat, in the third heartbeat, a third image signal IMG ₃ is acquired after a saturation pulse with a delay time of Tsat3 is used and the current time is determined to meet a predetermined condition based on the breathing navigation signal. Among them, Tsat3 ≠ Tsat2.

In the second and third heartbeats, T ₁ weighting is achieved using saturation pulses. Among them, the delay time of the saturation pulse is different, and the weight of T ₁ is different. Thus, one sampling point was obtained in each of the two heartbeats. 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.

Optionally, the delay time Tsat2 of the saturation pulse in the second heartbeat is 35% to 70% of the maximum time interval Tmax allowed by the system. The sum of the length of time occupied by the signal operation (eg, the respiratory navigation signal NAV) and the hardware response delay time during the Ttrigger period 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 Tsat3 of the saturation pulse in the third heartbeat is 90% to 100% of the maximum time interval Tmax allowed by the system. According to an embodiment of the present invention, Tsat2 is Tmax / 2, and Tsat3 is equal to Tmax. 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. FIG. 4 shows a T ₁ estimation curve according to this embodiment. Among them, the horizontal axis represents the delay time of the saturation pulse, the vertical axis represents the normalized longitudinal magnetization vector (Mz) that can be used for data reading, and the steady state value of the longitudinal magnetization vector when Mz = 1. Also shown in FIG. 4 are sampling points IMG ₁ , IMG ₂ and IMG ₃ obtained in the first, second and third heartbeats, respectively. Tsat2 and Tsat3 use the above range of values to make the sampling points more reasonably distributed, so that the T ₁ value can be accurately estimated even when only a small number of sampling points are obtained. In addition, the above-mentioned value range also makes the longitudinal magnetization vector that can be used for data reading larger, thereby improving the signal-to-noise ratio of the signal and obtaining a better quality original weighted image.

Similar to the first heartbeat, before the second and / or third heartbeat, there may be a heartbeat during which it is determined that the current moment does not meet the predetermined condition according to the breathing navigation signal. Optionally, in the signal acquisition operation, before the second and / or third heartbeat, the following operation is further included: in one heartbeat, when it is determined that the current moment does not meet a predetermined condition according to the respiratory navigation signal, the image signal is collected and The acquired image signal is set to invalid, and the next heartbeat is waited to perform the judgment operation again according to the breathing navigation signal and the corresponding image signal acquisition operation of the current heartbeat is performed according to the judgment result. If misjudgment occurs, the acquired image signal can be used as raw data. This ensures the completeness of the imaging data.

Taking the second heartbeat as an example, it is assumed that, before the second heartbeat, there is a heartbeat during which it is determined that the current time does not meet the predetermined condition according to the breathing navigation signal, which is referred to as the B heartbeat for short. In the next heartbeat of the B heartbeat, it is determined again whether the current time meets a predetermined condition according to the breathing navigation signal. If it still does not match, then acquire the image signal and disable the acquired image signal, and continue to wait for the next heartbeat. Until a certain heartbeat determines that the current time meets a predetermined condition according to the breathing navigation signal, the heartbeat is a second heartbeat. As described above, in the second heartbeat, the second image signal IMG ₂ is acquired after a saturation pulse with a delay time of Tsat2 is used and the current time is determined to meet a predetermined condition based on the respiratory navigation signal.

In the above signal acquisition operation, image signals (IMG ₁ , IMG _2, and IMG ₃ ) with different T ₁ weights are acquired. FIG. 5 shows IMG ₁ , IMG _2, and IMG ₃ of the heart from a short-axis perspective of the collected subject according to one embodiment of the present invention (for each of IMG ₁ , IMG _2, and IMG ₃ Select a layer from the apex, the heart, and the heart base as the representative images) and quantify the images based on the parameters T ₁ obtained by fitting these images. The image signals IMG ₁ , IMG ₂ and IMG _{3 are} acquired cyclically. That is, after completing the IMG ₃ acquisition of the third heartbeat, return to the first heartbeat. Then, the above process is repeated. In other words, during the imaging process, the above-mentioned imaging sequence is repeatedly acquired until the filling of all segments of the k-space in the magnetic resonance imaging is completed. It can be understood that the sequence of the first heartbeat to the third heartbeat is merely an example, and is not a limitation on the present invention. These three heartbeats can be performed in any order without affecting the effect of the technical solution of the present application.

As mentioned earlier, a steady-state image signal is acquired in the first heartbeat. In order to enable the longitudinal magnetization vector to be completely recovered from the last image signal acquisition (IMG ₃ ), a recovery time period is set before the first heartbeat. During this recovery period, no image signal is acquired. Optionally, during this recovery period, only the respiratory navigation signal NAV is collected to ensure the continuity of the respiratory navigation signal. As a result, interference with the parameter setting of the NAV and the flexibility it provides is avoided. This further ensures that the breathing navigation signal NAV accurately controls the signal acquisition operation to obtain a more accurate image signal.

Through the optimized imaging sequence, the imaging method 100 has high scanning efficiency and unlimited imaging resolution. Therefore, only a few sampling points are needed, for example, only the above three sampling points of IMG ₁ , IMG ₂ and IMG ₃ can accurately measure the 3D myocardial quantitative parameter T ₁ without additional filtering data processing. Reducing the number of sampling points, the direct technical effect is to shorten the scanning time during imaging.

It can be understood that the above-mentioned collected image signals (IMG ₁ , IMG ₂ and IMG ₃ ) can utilize various suitable data reading methods. The data reading method includes, but is not limited to, gradient echo, echo echo imaging (Echo-Planar Imaging, EPI), and spin echo (Spin Echo). Preferably, the data reading method adopts spoiled gradient echo (SPGR), balanced Steady state free precession (bSSFP), and gradient spin echo (Grase) techniques. The adoption of these preferred data reading methods can significantly reduce the requirements of the magnetic field intensity uniformity during the imaging process, so that this solution can be applied to high-field (such as 3T) magnetic resonance systems.

Fig. 6 shows an imaging sequence according to another embodiment of the invention. The imaging sequence shown in FIG. 6 is similar to the imaging sequence shown in FIG. 3. For the sake of brevity, the same parts in the two imaging sequences will not be described again. As shown in FIG. 6, before the image signals (IMG ₁ , IMG _2, and IMG ₃ ) are acquired in the signal acquisition operation, a liposuction operation (FS) may be performed separately. Liposuction helps reduce respiratory artifacts and significantly improves imaging quality.

According to an embodiment of the present invention, the parameter T ₁ may be determined according to the i-th image signal and the saturation pulse delay time Tsati of the i-th image signal, where i = 1, 2, 3. And when i = 1, Tsat1 used for data fitting is infinite.

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

Among them, i = 1, 2, 3. S _i and Tsati are respectively the ith image signal obtained by the signal acquisition operation and the delay time of its corresponding saturation pulse. S ₀ is a theoretical image signal when the magnetization vector is in an equilibrium state. S ₀ and T ₁ are unknown in this formula. Both can be determined from IMG ₁ , IMG ₂ and IMG ₃ . According to this formula, the parameter T ₁ can be determined more accurately, thereby generating a more accurate image.

7a and 7b show the images in the major axis angle according to the 3D _image T ₁ of the left ventricle from the same image of a subject of the present invention and the embodiment of the T. Figure 7c shows a histogram of FIG. 7a left ventricular myocardium T ₁ as a whole.

FIG. 8 shows an image of the quantification of the parameter T ₁ from two subjects according to one embodiment of the invention. These images were acquired 15 minutes after the two subjects used the T ₁ shortening contrast agent Gd-DTPA (0.15 mmol / kg, Magnevist, Bayer Pharma AG, Germany). These images are selected from the apex, the heart, and the heart. In this embodiment, because the measured T ₁ value of the myocardium is significantly shortened by the contrast agent, and the recovery process of the magnetization vector is relatively fast, the recovery time period before the acquisition of the steady-state image signal (IMG ₁ ) can be set to 3 seconds.

The data in Figures 2, 5, 7, and 8 are from healthy subjects. As shown in the histogram shown in Fig. 7c, the numerical parameters T according to the present invention obtained by rendering _a normal distribution. Moreover, the standard deviation of the value of the parameter T ₁ is small. Therefore, the myocardial quantitative magnetic resonance image generated according to the embodiment of the present invention ideally reflects the state of the myocardial tissue of the subject.

Optionally, the above-mentioned signal acquisition operation further includes at least one of the following operations: within the f1 heartbeat, after using a saturation pulse with a delay time of Tsatf1, and acquiring a condition that the current time meets a predetermined condition according to the breathing navigation signal, For image signals, Tsatf1 is not equal to the delay time of saturation pulses corresponding to other image signals, and f1 is an integer not equal to 1, 2, and 3. For example, one image signal may be acquired in each of the fourth heartbeat and the fifth heartbeat. This operation is similar to the above-mentioned operation of collecting IMG ₂ and IMG _3. For brevity, details are not described herein again. With this operation, the sampling points are increased.

It can be understood that the above-mentioned determination parameter T _{1 is} also based on the f1-th image signal and Tsatf1. Therefore, more accurate parameters T ₁ can be obtained by more sampling points participating in the fitting.

Optionally, the signal acquisition operation further includes at least one of the following operations: in the f2 heartbeat, after using a saturation pulse with a delay time of Tsat2 or Tsat3, and in determining that the current moment meets a predetermined condition according to the breathing navigation signal A second image signal or a third image signal corresponding to the saturation pulse is acquired again, and f2 is an integer not equal to 1, 2, and 3. It can be understood that if the f1th image signal is also acquired in the imaging method, f2 is not equal to f1. This operation is an operation of repeating the second heartbeat or the third heartbeat, thereby obtaining sampling points with the same T ₁ weight. In one example, within the sixth heartbeat, after using a saturation pulse with a delay time of Tsat2, and after determining that the current time meets a predetermined condition based on the respiratory navigation signal, a second image signal corresponding to the saturation pulse is acquired again. In the seventh heartbeat, after using a saturation pulse with a delay time of Tsat3, and after determining that the current time meets a predetermined condition based on the breathing navigation signal, a third image signal corresponding to the saturation pulse is acquired again. Finally, the parameter T _{1 is} determined from all the acquired second image signals and / or all the third image signals. In the above example, the second image signal collected in the second heartbeat, the sixth heartbeat, and the third image signal collected in the third heartbeat, the seventh heartbeat are all input to the signal model to fit the parameter T ₁ .

The effect of the above technical solution is equivalent to averaging the noise of the sampling point (for example, the second image signal), thereby reducing the fitting bias. In short, the above-mentioned signal acquisition operation can improve the calculation accuracy of the parameter T ₁ , thereby improving the image quality.

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

According to still another aspect of the present invention, a storage medium is further provided, and program instructions are stored on the storage medium, and when the program instructions are executed by a computer or a processor, the computer or the processor executes an embodiment of the present invention. Corresponding steps of the method of myocardial quantitative magnetic resonance imaging and used to implement the corresponding modules in the apparatus for myocardial quantitative magnetic resonance imaging according to an embodiment of the present invention. The storage medium may include, for example, a storage part 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 description provided here, numerous specific details are explained. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of the specification.

Similarly, it should be understood that, in order to streamline the invention and help understand one or more of the various aspects of the invention, in describing the exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, diagram, , Or in its description. However, the method of the present invention should not be construed to reflect the intention that the claimed invention requires more features than those explicitly recited in each claim. Rather, as reflected by the corresponding claims, the invention is that the corresponding technical problem can be solved with features that are less than all the features of a single disclosed embodiment. Thus, the claims following a specific embodiment are hereby explicitly incorporated into this specific embodiment, wherein each claim itself is a separate embodiment of the present invention.

Those skilled in the art can understand that, in addition to the mutual exclusion of features, all combinations of all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and any method or device so disclosed can be adopted in any combination. Processes or units are combined. Each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments and not other features, the combination of features of different embodiments is meant to be 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 other than those listed in a claim. The use of the words first, second, and third does not imply any order. These words can be interpreted as names.

The above description is only a specific embodiment of the present invention or a description of the specific embodiment, and the protection scope of the present invention is not limited to this. Any person skilled in the art can easily make the invention within the technical scope disclosed by the present invention. Any change or replacement is considered to be covered by 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

A method for myocardial quantitative magnetic resonance imaging, including:

Every recovery period, under the control of ECG gating signals and respiratory navigation signals, at least the following signal acquisition operations are performed:

In the first heartbeat, when it is determined according to the breathing navigation signal that the current moment meets a predetermined condition, collect a first image signal;

In the second heartbeat, after a saturation pulse with a delay time of Tsat2 is used, and when the current moment is determined to meet a predetermined condition according to the breathing navigation signal, a second image signal is acquired;

In the third heartbeat, a third image signal is acquired after a saturation pulse with a delay time of Tsat3 is used, and the current moment is determined to meet a predetermined condition based on the breathing navigation signal, where Tsat3- ≠ Tsat2;

Determine the parameter T 1 according to the i-th image signal and the delay time Tsati of the saturation pulse corresponding to the i-th image signal, where i = 1, 2, 3, and when i = 1, Tsati is infinite;

A quantitative magnetic resonance image of the myocardium is generated based on the parameter T 1 .
The method of claim 1, wherein the signal acquisition operation further comprises at least one of the following operations:

In the f1 heartbeat, after using a saturation pulse with a delay time of Tsatf1 and determining that the current time meets a predetermined condition according to the breathing navigation signal, the f1 image signal is collected, where Tsatf1 is not equal to the saturation pulse corresponding to other image signals Delay time, f1 is an integer not equal to 1, 2 and 3;

Wherein, the determination parameter T 1 is further based on the f1-th image signal and the Tsatf1.
The method of claim 1, wherein the signal acquisition operation further comprises at least one of the following operations:

In the f2 heartbeat, after using a saturation pulse with a delay time of Tsat2 or Tsat3, and after determining that the current time meets a predetermined condition according to the breathing navigation signal, the second image signal or the third image signal corresponding to the saturation pulse is acquired again , F2 is an integer not equal to 1, 2 and 3.
The method according to claim 1, wherein in the signal acquisition operation, before the first heartbeat, the method further comprises the following operations:

In a heartbeat, when it is judged that the current time does not meet the predetermined conditions according to the respiratory navigation signal, it waits for the next heartbeat to perform the judgment operation again according to the respiratory navigation signal and perform the corresponding image signal acquisition operation of the current heartbeat according to the judgment result.
The method according to claim 1 or 4, wherein, in the signal acquisition operation, before the second heartbeat and / or the third heartbeat, the method further comprises the following operations:

In a heartbeat, when it is determined that the current time does not meet the predetermined conditions according to the breathing navigation signal, acquire an image signal and invalidate the acquired image signal, and wait for the next heartbeat to perform the judgment operation again based on the breathing navigation signal and The corresponding image signal acquisition operation of the current heartbeat is performed according to the judgment result.
The method of claim 1, wherein the acquiring the first image signal, the acquiring the second image signal, and the acquiring the third image signal utilize a damaged gradient echo, a balanced steady-state free precession, or a gradient spin loop Wave data read mode.
The method according to claim 1, wherein, in the signal acquisition operation, before the acquisition of the first image signal, the acquisition of the second image signal, and the acquisition of the third image signal, respectively, performing a liposuction operation .
The method of claim 1, wherein:

The Tsat3 is 90% to 100% of the maximum time interval Tmax allowed by the system, and the Tsat2 is 35% to 70% of the Tmax.
The method according to claim 1, wherein the recovery period includes n heartbeats, where n is a smallest integer greater than or equal to N / (60 / HR), and N is a length of time that allows the magnetization vector to be recovered, and the unit is Second, HR is the heart rate, and the unit is heartbeat / minute.
The method according to claim 1, wherein said determining comprises determining parameters of the parameter T 1 T 1 according to the formula,

Among them, S 0 is the signal of the longitudinal magnetization vector in the equilibrium state, S i and Tsati are respectively the delay time of the i-th image signal and its corresponding saturation pulse, i = 1, 2, 3.
A device for myocardial quantitative magnetic resonance imaging, including a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the computer program instructions are used to execute claims 1 to The method of quantitative myocardial magnetic resonance imaging according to any one of 10 items.
A storage medium stores program instructions on the storage medium, and the program instructions are used to execute the myocardial quantitative magnetic resonance imaging method according to any one of claims 1 to 10 when running.