Magnetic resonance angiography method and magnetic resonance imaging device

Abstract

The invention provides a magnetic resonance angiography method and magnetic resonance imaging equipment. The method comprises the following steps: for each magnetic resonance image to be generated in a magnetic resonance image sequence, sequentially generating a layer selection saturation pulse signal and N reversal pulse signals in an imaging area of at least a target object; magnetic resonance signals of tissue in the imaging region are acquired and the magnetic resonance image is generated based on the acquired magnetic resonance signals. The longitudinal magnetization directions of the blood subjected to the second reversal operation in the first time period are negative when the blood is imaged in the imaging area, and the longitudinal magnetization directions of the blood subjected to the second reversal operation in the second time period are positive when the blood is imaged in the imaging area. The display effect of the blood inflow process in the obtained magnetic resonance image sequence is clearer, and a user can be helped to determine the actual condition of blood perfusion into the blood vessel in the imaging area.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging technology, and more particularly to a magnetic resonance angiography method, a magnetic resonance imaging device, a non-volatile storage medium, and a computer program product. Background Art

[0002] Magnetic resonance imaging (MRI) is a non-invasive medical imaging technique that uses radiofrequency pulses and gradient magnetic fields to produce detailed images of the human body's internal structures. Unlike X-rays or CT scans, MRI does not use ionizing radiation, making it safer for the subject. 4D MRI technology generates a sequence of multiple MRI images over time. This sequence allows observation of continuous changes in the subject's internal tissue structure.

[0003] To improve the visibility of blood in certain areas of the imaging subject, traditional 4D MRI technology often relies on the use of contrast agents (such as gadolinium-based contrast agents). Although this approach increases the contrast of MRI images, the contrast agent may impose a metabolic burden on the kidneys of the imaging subject. In addition, the use of contrast agents also increases the cost of imaging. In other approaches, MRI images can be generated based on subtraction technology to form an MRI image sequence. Based on subtraction technology, two sets of independent imaging data sets need to be acquired to generate a single MRI image in an MRI image sequence. Therefore, the imaging process is time-consuming and has low imaging efficiency. On the one hand, this seriously affects the imaging subject's experience. On the other hand, it is difficult for the imaging subject to maintain a constant posture during the long imaging process. Changes in posture will result in poor contrast in the MRI images obtained by subtraction. Summary of the Invention

[0004] The present invention is proposed in view of the above problems. The present invention provides a magnetic resonance angiography method, a magnetic resonance angiography apparatus, a non-volatile storage medium and a computer program product.

[0005] According to one aspect of the present invention, a magnetic resonance angiography method is provided, the magnetic resonance angiography method comprising: for each magnetic resonance image to be generated in a magnetic resonance image sequence, sequentially generating a slice-selective saturation pulse signal and N inversion pulse signals in at least an imaging region of a target object, wherein the N inversion pulse signals are used to perform a first inversion operation on tissue in at least the imaging region, and perform a second inversion operation on blood in a marked region of the target object both within a first time period and when a first time preset condition is met, and within a second time period and when a second time preset condition is met, so that the longitudinal magnetization direction of the blood subjected to the second inversion operation in the first time period when imaging the imaging region is both negative, and the longitudinal magnetization direction of the blood that undergoes the second inversion operation in the second time period when the imaging area is imaged is positive, and within the cycle of generating the layer-selected saturation pulse signal and the N inversion pulse signals, there is a switching moment corresponding to the magnetic resonance image, the first time period is the time period before the switching moment in the cycle, the second time period is the time period after the switching moment in the cycle, N is a positive integer, the marking area is adjacent to the imaging area and the blood to be imaged flows into the imaging area through the marking area; the magnetic resonance signals of the tissue in the imaging area are collected, and the magnetic resonance image is generated based on the collected magnetic resonance signals; wherein, the later the position of the magnetic resonance image in the magnetic resonance image sequence is, the earlier the corresponding switching moment is in the cycle.

[0006] Illustratively, the first preset time condition includes: when N is a positive even number, after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging region, and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on tissue in at least the imaging region; or after or simultaneously with the (i+2)th inversion pulse signal from the last among the N inversion pulse signals performing the first inversion operation on tissue in at least the imaging region, and before the (i+1)th inversion pulse signal from the last among the N inversion pulse signals performs the first inversion operation on tissue in at least the imaging region, where i is a positive odd number less than or equal to N-2;

[0007] The second time preset condition includes: when N is a positive odd number, after the layer-selective saturation pulse signal performs saturation processing on the tissue in at least the imaging area, and before the first inversion pulse signal among the N inversion pulse signals performs the first inversion operation on the tissue in at least the imaging area; or after or at the same time as the j+1th inversion pulse signal from the N inversion pulse signals performs the first inversion operation on the tissue in at least the imaging area, and before the jth inversion pulse signal from the N inversion pulse signals performs the first inversion operation on the tissue in at least the imaging area, where j is a positive odd number less than or equal to N-1.

[0008] Exemplarily, within the first time period and when the first preset time condition is met, performing a second inversion operation on the blood in the marked area of ​​the target object includes:

[0009] During the first period, another inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area.

[0010] Among them, the duration period of the additional inversion pulse signal is: the period after the (i+2)th inversion pulse signal from the end performs the first inversion operation on the tissue in at least the imaging area and before the (i+1)th inversion pulse signal from the end performs the first inversion operation on the tissue in at least the imaging area, and when N is a positive even number, the period after the layer-selective saturation pulse signal performs saturation processing on the tissue in at least the imaging area and before the first inversion pulse signal performs the first inversion operation on the tissue in at least the imaging area.

[0011] Exemplarily, within the first time period and when the first preset time condition is met, performing a second inversion operation on the blood in the marked area of ​​the target object includes:

[0012] In the first time period, the second inversion operation is performed on the blood in the marked area using the (i+2)th inversion pulse signal from the end.

[0013] Illustratively, within the first time period and when the first preset time condition is met, performing the second inversion operation on the blood in the marked area of ​​the target object further includes any one of the following:

[0014] In the first time period, using the Nth inversion pulse signal among the N inversion pulse signals, a second inversion operation is performed on the blood in the marked area;

[0015] During the first time period, an additional inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area, wherein the duration of the additional inversion pulse signal is: after the Nth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the start time of signal acquisition.

[0016] Exemplarily, within the second time period and when the second preset time condition is met, performing a second inversion operation on the blood in the marked area of ​​the target object includes:

[0017] During the second period, another inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area.

[0018] Among them, the duration period of the additional inversion pulse signal is: the period after the j+1th inversion pulse signal from the end performs the first inversion operation on the tissue in at least the imaging area and before the jth inversion pulse signal from the end performs the first inversion operation on the tissue in at least the imaging area, and when N is a positive odd number, the period after the layer-selective saturation pulse signal performs saturation processing on the tissue in at least the imaging area and before the first inversion pulse signal among the N inversion pulse signals performs the first inversion operation on the tissue in at least the imaging area.

[0019] Exemplarily, within the second time period and when the second preset time condition is met, performing a second inversion operation on the blood in the marked area of ​​the target object includes:

[0020] In the second time period, the second inversion operation is performed on the blood in the marked area using the j+1th inversion pulse signal from the end.

[0021] Exemplarily, sequentially generating a slice-selective saturation pulse signal and N inversion pulse signals in at least an imaging region of a target object includes:

[0022] A layer-selected saturation pulse signal and N inversion pulse signals are sequentially generated in a background suppression area of ​​a target object, wherein the background suppression area includes an imaging area, the background suppression area and the imaging area have identical edges adjacent to the marking area, and in the flow direction of the blood to be imaged, the length of the background suppression area is greater than or equal to the maximum value of the first values, the first value includes the product of the time interval between each two adjacent target pulse signals and the blood flow velocity of the blood to be suppressed, and the target pulse signal includes the layer-selected saturation pulse signal and N inversion pulse signals.

[0023] Exemplarily, acquiring magnetic resonance signals of tissue in an imaging region and generating the magnetic resonance image based on the acquired magnetic resonance signals includes:

[0024] Based on a center-first sampling mode of K-space, magnetic resonance signals of tissues are collected in an imaging region, and data filling of the K-space is performed based on the collected magnetic resonance signals;

[0025] The magnetic resonance image is generated based on the data in the filled K-space.

[0026] Exemplarily, generating the magnetic resonance image based on the acquired magnetic resonance signals includes:

[0027] Filling the K space with data based on the acquired magnetic resonance signals;

[0028] The magnetic resonance image is generated based on the data in the filled K space through a spatiotemporal joint reconstruction algorithm.

[0029] According to another aspect of the present invention, a magnetic resonance imaging device is provided, which includes a processor and an execution device. For each magnetic resonance image to be generated in a magnetic resonance image sequence, the processor is configured to control the execution device to perform the following steps: sequentially generating a layer-selected saturation pulse signal and N inversion pulse signals in at least an imaging region of a target object, wherein the N inversion pulse signals are used to perform a first inversion operation on tissue in at least the imaging region, and performing a second inversion operation on blood in a marked region of the target object both within a first time period and when a first time preset condition is met and within a second time period and when a second time preset condition is met, so that the blood subjected to the second inversion operation in the first time period is imaged in the imaging region. The longitudinal magnetization direction of the blood is negative, and the longitudinal magnetization direction of the blood that undergoes the second inversion operation in the second time period when imaged in the imaging area is positive. Within the cycle of generating the layer-selected saturation pulse signal and the N inversion pulse signals, there is a switching moment corresponding to the magnetic resonance image. The first time period is the time period before the switching moment in the cycle, and the second time period is the time period after the switching moment in the cycle. N is a positive integer. The marking area is adjacent to the imaging area and the blood to be imaged flows into the imaging area via the marking area. The magnetic resonance signal of the tissue in the imaging area is acquired. The processor is further configured to generate the magnetic resonance image based on the acquired magnetic resonance signal. The later the position of the magnetic resonance image in the magnetic resonance image sequence is, the earlier the corresponding switching moment is in the cycle.

[0030] According to another aspect of the present invention, a non-volatile storage medium is provided, wherein program instructions are stored on the non-volatile storage medium, and the program instructions are used to execute the above-mentioned magnetic resonance angiography method when running.

[0031] According to another aspect of the present invention, a computer program product is further provided, wherein the computer program product comprises computer program instructions, and when the computer program instructions are executed by a processor, the computer program instructions are used to execute the above-mentioned magnetic resonance angiography method.

[0032] According to the above-mentioned solution of the present invention, on the one hand, the use of contrast agents is unnecessary, which is more friendly to the health of the target subject and lowers the cost. In addition, since subtraction technology is not required, the total time required for the magnetic resonance imaging process in the above-mentioned solution is shortened, significantly improving imaging efficiency and also helping to reduce the impact of changes in the target subject's posture on the imaging contrast of the magnetic resonance image. Furthermore, within a first time period and subject to the first time preset conditions, a second inversion operation can be performed on the blood in the marked area, so that the blood appears as a negative signal (i.e., the longitudinal magnetization direction is negative) when the magnetic resonance signal of the imaging area is acquired. Within a second time period and subject to the second time preset conditions, a second inversion operation can be performed on the blood in the marked area, so that the blood appears as a positive signal (i.e., the longitudinal magnetization direction is positive) when the magnetic resonance signal of the imaging area is acquired. The imaging results of blood with negative and positive signals in the magnetic resonance image are significantly different. By adjusting the switching time, the lengths of the first and second time periods can be adjusted, thereby obtaining a magnetic resonance image sequence that shows the changes in blood perfusion over time. In the magnetic resonance image sequence obtained by the above solution, the display effect of the blood inflow process of the positive signal is clearer, which is helpful for assisting the user to determine the actual situation of blood perfusion into the blood vessels in the imaging area. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features, and advantages of the present invention will become more apparent through a more detailed description of the embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings are provided 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 are not intended to limit the present invention. In the drawings, the same reference numerals generally represent the same components or steps.

[0034] Figure 1 FIG2 shows a schematic flow chart of a magnetic resonance angiography method according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram showing a process of generating a magnetic resonance image in a magnetic resonance image sequence according to one embodiment of the present invention is shown;

[0036] Figure 3 A schematic diagram showing a marking area, an imaging area, and a background suppression area according to an embodiment of the present invention is shown;

[0037] Figure 4 Schematic diagrams showing magnetic resonance images a to e according to one embodiment of the present invention;

[0038] Figure 5 A schematic diagram showing a process of generating a magnetic resonance image f according to an embodiment of the present invention;

[0039] Figure 6 A schematic diagram showing a process of generating magnetic resonance images g and h according to an embodiment of the present invention;

[0040] Figure 7 A schematic block diagram of a magnetic resonance imaging device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more apparent, exemplary embodiments of 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, and it should be understood that the present invention is not limited to 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 scope of protection of the present invention.

[0042] In order to at least partially solve the above problems, an embodiment of the present invention provides a magnetic resonance angiography method. Figure 1 FIG. 1 shows a schematic flow chart of a magnetic resonance angiography method according to an embodiment of the present invention. Figure 1 As shown, the method may include step S110 and step S120.

[0043] In step S110 , for each magnetic resonance image to be generated in a magnetic resonance image sequence, a slice-selective saturation pulse signal and N inversion pulse signals are sequentially generated in at least an imaging region of a target object.

[0044] The MRI sequence may include multiple MRI images to be generated. Once each MRI image has been generated, the user can view the MRI sequence to determine the actual blood perfusion status of the target subject's blood vessels. It will be appreciated that the MRI sequence may be a video comprising multiple MRI images.

[0045] For example, magnetic resonance imaging equipment can be used to acquire magnetic resonance signals from a target subject. The target subject can be a human subject undergoing magnetic resonance imaging. The magnetic resonance imaging equipment can include a scanner, an examination platform, and a host computer. The scanner has a space for accommodating the examination platform. The target subject can lie flat on the examination platform, which can then be moved into the space. Hydrogen atoms in the target subject's tissue are affected by the magnetic force of the main magnetic field (also known as the B0 magnetic field). From a macroscopic perspective, this can be seen as a net magnetization vector formed by several hydrogen atoms with a direction close to the Z-axis. The Z-axis direction can be the direction from the head placement area to the foot placement area on the examination platform. The head placement area can be used to place the target subject's head, and the foot placement area can be used to place the target subject's feet. When a radio frequency pulse signal (such as the slice-selective saturation pulse signal and inversion pulse signal in the embodiments of the present application) is applied to at least the imaging area of ​​the target subject, some hydrogen atoms in the application area absorb energy, transitioning from a low-energy state to a high-energy state. From a macroscopic perspective, this can be seen as a change in the direction of the net magnetization vector. After the RF pulse signal is applied, the high-energy hydrogen atoms relax, generating an electrical signal that is received by the scanner. The scanner converts the electrical signal into a digital signal and sends it to the host computer, which uses the MRI algorithm to generate an MRI image.

[0046] The imaging area of ​​the target object may be a portion of the target object's body that the user desires to observe. For example, if the user desires to observe the target object's head, the imaging area may be the target object's head area, or a portion of the head area. For another example, if the user desires to observe the target object's kidneys, the imaging area may be the target object's kidney area, or a portion of the kidney area. It is understood that the user may also select the imaging area of ​​the target object based on actual needs, and this embodiment of the present invention does not impose any limitation thereto.

[0047] The slice-selective saturation pulse signal can be used to adjust the direction of the net magnetization vector to be close to the X-axis. The X-axis can be the direction from the left hand placement area to the right hand placement area on the examination platform. The left hand placement area can be used to place the subject's left hand, and the right hand placement area can be used to place the subject's right hand. Through this process, the components of the net magnetization vector in the planes containing the X and Y axes increase. As hydrogen atoms precess, a time-varying magnetic resonance signal is generated. The Y-axis can be the vertical axis. For example, if the signal intensity of the magnetic resonance signal (hereinafter referred to as the signal) corresponding to untreated blood is considered 1 (a value greater than 0 is considered to indicate a positive longitudinal magnetization direction, which can be considered the direction of the net magnetization vector's projection on the Z-axis), and the signal intensity after applying the inversion pulse signal to the blood is considered -1 (a value less than 0 is considered to indicate a negative longitudinal magnetization direction), then ideally, the slice-selective saturation pulse signal can adjust the signal intensity of the signal generated by the tissue in the application area to 0. It is understood that the tissue in the application area may include solid tissue, such as fat and brain tissue, as well as fluid tissue, such as blood and cerebrospinal fluid. Thus, background signal suppression can be achieved through the slice-selective saturation pulse signal. It is understood that the slice-selective saturation pulse signal may include a single pulse or multiple pulses.

[0048] In one example, the layer-selective saturation pulse signal can be generated only in the imaging area. In another example, the layer-selective saturation pulse signal can also be generated in an area larger than the imaging area. The larger area at least includes the imaging area. Applying the layer-selective saturation pulse signal to a larger area can more effectively suppress the signal of solid tissue to near zero, thereby reducing its impact on the imaging quality. This can also suppress the background signal of venous blood, which flows in the opposite direction to the direction of arterial blood. In addition, it can also ensure that even if the tissue is located at the edge of the imaging area, its signal can be fully suppressed, thereby avoiding signal contamination caused by edge effects. Developers can determine the application area of ​​the layer-selective saturation pulse signal according to actual needs, and the embodiments of the present invention do not limit this. For the convenience of description, the application area of ​​the layer-selective saturation pulse signal is referred to as the background suppression area of ​​the target object.

[0049] N inversion pulse signals can be used to perform a first inversion operation on tissue in at least the imaging area. N can be a positive integer. Similar to the slice-selective saturation pulse signal, the inversion pulse signal can be generated only in the imaging area. Alternatively, the inversion pulse signal can be generated in an area larger than the imaging area. The larger area includes the imaging area. It will be understood that the application area of ​​the inversion pulse signal can be the same as or different from the application area of ​​the slice-selective saturation pulse signal. For ease of description, the following embodiments are described as an example in which the application areas of both are the same background suppression area.

[0050] From a macroscopic perspective, the above-mentioned inversion pulse signal can be used to implement a first inversion operation. The first inversion operation can be used to reverse the direction of the net magnetization vector of the tissue in the application area of ​​the inversion pulse signal. For example, through the above-mentioned first inversion operation, the direction of the above-mentioned net magnetization vector can be reversed 180 degrees. After an appropriate inversion recovery time (Inversion Time, or TI), the intensity of the net magnetization vector can be close to zero. Therefore, the above-mentioned inversion pulse signal can also be used to selectively suppress background signals. It can be understood that the above-mentioned inversion pulse signal may include a single pulse or multiple pulses. The target parameters of multiple inversion pulses (for example, pulse frequency, pulse duration, pulse intensity, etc.) may be the same.

[0051] Within the first time period and when the first time preset condition is met, a second inversion operation is performed on the blood in the marked area of ​​the target object, so that the longitudinal magnetization direction of the blood subjected to the second inversion operation within the first time period is negative when imaging in the imaging area.

[0052] The above-mentioned layer-selective saturation pulse signal and N inversion pulse signals can be generated in at least the imaging area with a specific period. The specific period is, for example, 2000 ms. For each magnetic resonance image to be generated in the magnetic resonance image sequence, the above-mentioned period can start from the start time of generation of the layer-selective saturation pulse signal and end at the start time of signal acquisition of the magnetic resonance image. Within the period of generating the layer-selective saturation pulse signal and the N inversion pulse signals, there is a conversion moment corresponding to the magnetic resonance image. The first time period is the period before the conversion moment in the period. The above-mentioned conversion moment can be any moment in the period preset by the user or developer. In the process of generating a magnetic resonance image, the radio frequency pulse signal within a period (hereinafter referred to as the period corresponding to the magnetic resonance image) can be used to generate the magnetic resonance image.

[0053] See Figure 2 , Figure 2 The figure shows a schematic diagram of the process of generating magnetic resonance images in a magnetic resonance image sequence according to one embodiment of the present invention. It is understood that the magnetic resonance image sequence may include not only magnetic resonance images a to e, but also other magnetic resonance images not shown. In this example, the positions of magnetic resonance images a to e in the magnetic resonance image sequence may be gradually moved back. Figure 2, the above-mentioned cycle may include the time periods TD (or Time Delay) 0 to TD4, a total of 5 time periods. The above-mentioned first time period may be the time period corresponding to the solid line segment in the figure (hereinafter referred to as the solid line time period). For example, in the generation process of magnetic resonance image a, the solid line time period includes the time period TD0 to TD4, then in the generation process of magnetic resonance image a, the first time period includes the time period TD0 to TD4. For another example, in the generation process of magnetic resonance image b, the solid line time period includes the time period TD2 to TD4, then in the generation process of magnetic resonance image b, the first time period includes the time period TD2 to TD4. It can be understood that the first time period may also include the above-mentioned conversion moment, which may depend on the actual needs of the developer or user. The above-mentioned first time preset condition may be determined according to the actual needs of the user or developer, and the embodiment of the present invention does not limit it here. The above-mentioned signal acquisition start time may refer to the imaging start time in the figure.

[0054] The marking region is adjacent to the imaging region and the blood to be imaged flows into the imaging region through the marking region. Figure 3 , Figure 3 Schematic diagram showing a marking area, an imaging area, and a background suppression area according to an embodiment of the present invention. Figure 3 For example, the imaging area is a portion of the target subject's brain region. In this example, the blood to be imaged is cerebral arterial blood. Since the heart, which supplies cerebral arterial blood, is located below the brain region, the area below the brain region can be used as the aforementioned marked area. Figure 3 The figure also shows an example where the imaging area is the kidney area of ​​the target object. In this example, the arterial blood to be imaged flows from the heart through the abdominal aorta into the kidney area. The heart is located above the kidney area. Therefore, in this example, the area above the kidney area can be used as the above-mentioned marked area. Similarly, Figure 3 The figure also shows an example where the imaging area is the target subject's hip region. In this example, the blood to be imaged is also arterial blood, and the area above the hip region can be used as the aforementioned marked area. The specific locations of the aforementioned marked and imaging areas can be determined by the developer or user and are not limited in this embodiment of the present invention. It is understood that the blood to be imaged can be either arterial or venous.

[0055] In the second time period and when the second preset time condition is met, a second inversion operation is performed on the blood in the marked area of ​​the target object, so that the longitudinal magnetization direction of the blood subjected to the second inversion operation in the second time period is positive when imaging in the imaging area.

[0056] The second period is the period after the transition moment in the cycle. Figure 2, the above-mentioned second time period may be the time period corresponding to the dotted line segment in the figure (hereinafter referred to as the dotted time period). For example, in the process of generating the magnetic resonance image e, the dotted time period includes the time period from TD0 to TD4, then in the process of generating the magnetic resonance image e, the second time period includes the time period from TD0 to TD4. In the process of generating the magnetic resonance image d, the dotted time period includes the time period from TD0 to TD3, then in the process of generating the magnetic resonance image d, the second time period includes the time period from TD0 to TD3. It can be understood that the second time period may include the above-mentioned conversion moment, which may depend on the actual needs of the developer or user. The above-mentioned second time preset condition may be determined according to the actual needs of the user or developer, and the embodiment of the present invention is not limited here, and the second time preset condition may be different from the first time preset condition.

[0057] For each magnetic resonance image to be generated in the magnetic resonance image sequence, the later the magnetic resonance image is in the magnetic resonance image sequence, the earlier the corresponding conversion moment is within the cycle corresponding to the magnetic resonance image. In actual scenarios, the earlier the conversion moment is within the cycle, the shorter the first period is, and the less the total amount of blood with negative longitudinal magnetization in the imaging area. If the area of ​​the imaging area remains unchanged, the total amount of blood with positive longitudinal magnetization and blood with negative longitudinal magnetization can be approximately constant. Therefore, the magnetic resonance image generated later will have a greater total amount of blood with positive longitudinal magnetization than the magnetic resonance image generated earlier. Users can observe in the magnetic resonance image sequence that the amount of blood with positive longitudinal magnetization increases over time, which can be viewed as the process of blood injection into the blood vessels.

[0058] Continue reading Figure 2 A transition moment may exist between the solid-line time period and the dashed-line time period above, dividing the two time periods. It is understood that the transition moment corresponding to the first magnetic resonance image in the magnetic resonance image sequence may not be the start time of signal acquisition for that magnetic resonance image, that is, the end time of the corresponding cycle. The transition moment corresponding to the last magnetic resonance image in the magnetic resonance image sequence may not be the start time of generation of the slice-selective saturation pulse signal, that is, the start time of the corresponding cycle. The transition moment corresponding to each magnetic resonance image may be different, and the time interval between the transition moments corresponding to adjacent magnetic resonance images may be the same. It is understood that the shorter the time interval, the greater the total number of magnetic resonance images in the magnetic resonance image sequence. The specific value of the time interval, the transition moment corresponding to the first magnetic resonance image, and the transition moment corresponding to the last magnetic resonance image can be determined by the developer or user based on actual conditions.

[0059] See Figure 4 , Figure 4 Schematic diagrams of magnetic resonance images a to e according to an embodiment of the present invention are shown. Figure 4The solid rectangle in the figure may be the background suppression area mentioned above. The dotted rectangle may be the imaging area mentioned above. The mosaic area may be the marking area mentioned above. Figure 2 and Figure 4 , in the process of generating the magnetic resonance image a, the longitudinal magnetization direction of the blood flowing into the imaging area during the period TD0 to TD4 is negative. The blood with a negative longitudinal magnetization direction is Figure 4 In the process of generating magnetic resonance image b, the longitudinal magnetization direction of the blood flowing into the imaging area during the period TD0 to TD1 is positive. Figure 4 Blood can appear as dark gray in the image. The longitudinal magnetization direction of blood flowing into the imaging region during the time period TD2 to TD4 is negative. During the generation of magnetic resonance image c, the longitudinal magnetization direction of blood flowing into the imaging region during the time period TD0 to TD2 is positive, and the longitudinal magnetization direction of blood flowing into the imaging region during the time period TD3 to TD4 is negative. During the generation of magnetic resonance image d, the longitudinal magnetization direction of blood flowing into the imaging region during the time period TD0 to TD3 is positive, and the longitudinal magnetization direction of blood flowing into the imaging region during the time period TD4 is negative. During the generation of magnetic resonance image e, the longitudinal magnetization direction of blood flowing into the imaging region during the time period TD0 to TD4 is positive. During the display of each magnetic resonance image in the magnetic resonance image sequence, the boundary between the light gray blood and the dark gray blood can be observed to continuously move along the direction of blood flow, allowing users to observe the blood flow process in the blood vessels through the magnetic resonance image sequence.

[0060] In step S120 , for each magnetic resonance image to be generated in the magnetic resonance image sequence, magnetic resonance signals of tissue in the imaging region are acquired, and the magnetic resonance image is generated based on the acquired magnetic resonance signals.

[0061] For each magnetic resonance image to be generated in a magnetic resonance image sequence, magnetic resonance signals of tissue in the imaging region may be acquired after the cycle corresponding to the magnetic resonance image has completed. In some examples, multiple preset phase encoding gradients may be sequentially applied in at least the imaging region using gradient coils in a scanner to sequentially form multiple gradient magnetic fields. Each phase encoding gradient may correspond to a row in K-space. Magnetic resonance signals acquired in the gradient magnetic field formed based on the phase gradient encoding may be filled into the row in K-space corresponding to the phase gradient encoding. The data in the filled K-space may be converted into a magnetic resonance image using an inverse Fourier transform. In one example, magnetic resonance signals corresponding to only a portion of K-space may be acquired, and then, based on the conjugate symmetry of K-space, a preset algorithm may be used to complete the unfilled space in K-space. A magnetic resonance image is then generated using the data in the fully filled K-space. It will be appreciated that if 3D imaging technology is used, the data in K-space may be acquired sequentially in blocks, but this is not a limitation in the present embodiment.

[0062] In some embodiments, various magnetic resonance imaging techniques may be used to generate magnetic resonance images, such as MP-RAGE (Magnetization Prepared Rapid Gradient Echo) imaging, GRE (Gradient Recalled Echo) imaging, FSE (Fast Spin Echo) imaging, balanced Steady State Free Processing (bSSFP), and stack-of-star golden angle imaging.

[0063] In one example, the magnetic resonance image can be processed using an image processing algorithm before being displayed. For example, the magnetic resonance image can be subjected to feature enhancement or noise suppression. In another example, a region segmentation algorithm or model can be used to determine a region of interest in the magnetic resonance image.

[0064] According to the above-mentioned solution of the embodiment of the present invention, on the one hand, no contrast agent is required, which is more friendly to the health of the target subject and lower in cost. Furthermore, no subtraction technology is required, so the total time required for the magnetic resonance imaging process in the above-mentioned solution is shortened, significantly improving imaging efficiency and also helping to reduce the impact of changes in the target subject's posture on the imaging contrast of the magnetic resonance image. Furthermore, within a first time period and subject to the first time preset conditions, a second inversion operation can be performed on the blood in the marked area, so that the blood appears as a negative signal (i.e., the longitudinal magnetization direction is negative) when the magnetic resonance signal of the imaging area is acquired. Within a second time period and subject to the second time preset conditions, a second inversion operation can be performed on the blood in the marked area, so that the blood appears as a positive signal (i.e., the longitudinal magnetization direction is positive) when the magnetic resonance signal of the imaging area is acquired. The imaging results of blood with negative and positive signals in the magnetic resonance image are significantly different. By adjusting the switching time, the lengths of the first and second time periods can be adjusted, thereby obtaining a magnetic resonance image sequence that shows the changes in blood perfusion over time. In the magnetic resonance image sequence obtained by the above solution, the display effect of the blood inflow process of the positive signal is clearer, which is helpful for assisting the user to determine the actual situation of blood perfusion into the blood vessels in the imaging area.

[0065] Exemplarily, sequentially generating a layer-selected saturation pulse signal and N inversion pulse signals in at least the imaging area of ​​the target object in step S110 may include sequentially generating a layer-selected saturation pulse signal and N inversion pulse signals in the background suppression area of ​​the target object.

[0066] The background suppression region may include the imaging region. The background suppression region and the imaging region have the same edges that are adjacent to the marking region. Figure 3 For an example in which the imaging region is the brain region, the lower edges of the background suppression region and the imaging region are the same edge, and this edge is adjacent to the marked region. For an example in which the imaging regions are the kidney region and the hip region, respectively, the upper edges of the background suppression region and the imaging region are the same edge, and this edge is adjacent to the marked region.

[0067] For ease of description, the embodiment of the present invention collectively refers to the layer-selected saturation pulse signal and the N inversion pulse signals as target pulse signals. The first value includes the product of the time interval between each two adjacent target pulse signals and the blood flow velocity of the blood to be suppressed. For example, continue to refer to Figure 2For example, the first value may include: the product of the time interval between the layer-selected saturation pulse signal and the inversion pulse signal 4 and the blood flow velocity of the blood to be suppressed, the product of the time interval between the inversion pulse signal 4 and the inversion pulse signal 3 and the blood flow velocity of the blood to be suppressed, etc. In the flow direction of the blood to be imaged, the length of the background suppression area is greater than or equal to the maximum value in the first value. Thereby, it is ensured that all signals of the blood to be suppressed that flows into the imaging area can be fully and effectively suppressed, reducing its interference with the signal of the blood to be imaged. The blood to be suppressed may be blood that the user is not concerned about. For example, in the case where the user is concerned about the flow state of the arterial blood in the brain, the above-mentioned blood to be suppressed may include the venous blood in the brain.

[0068] According to the above-described scheme of an embodiment of the present invention, a layer-selected saturation pulse signal and N inversion pulse signals can be sequentially generated within the background suppression region of the target object. The background suppression region includes the imaging region and other regions. Because the saturation pulse signal and the N inversion pulse signals have a larger range than the imaging region, background signal interference is reduced, the signal-to-noise ratio is improved, and the imaging contrast of the blood being imaged is thereby enhanced. This facilitates improved display quality of magnetic resonance images, and thus, improved display quality of magnetic resonance image sequences. Furthermore, a background suppression region of the aforementioned size also avoids artifacts in magnetic resonance images, and avoids excessive scanning times and unnecessary increases in computing resource consumption.

[0069] Exemplarily, the first time preset condition may include: when N is a positive even number, after the layer-selected saturation pulse signal performs saturation processing on tissue in at least the imaging area, and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on tissue in at least the imaging area.

[0070] Continue reading Figure 2 In this example, N equals 4. For the solid-line periods in the respective cycles of magnetic resonance images a through d, after the slice-selective saturation pulse signal saturates tissue in at least the imaging region, and before the inversion pulse signal 4 (the first inversion pulse signal in this example) performs a first inversion operation on tissue in at least the imaging region, a second inversion operation can be performed on the blood in the marked region of the target object. The additional inversion pulse signal, compared to the N inversion pulse signals, is hereinafter referred to as the first pulse signal. In this example, the first pulse signal b is used to perform the second inversion operation.

[0071] Regardless of any positive integer N, the first preset time condition may include: after or simultaneously with the (i+2)th inversion pulse signal from the N inversion pulse signals performing the first inversion operation on at least the tissue in the imaging region, and before the (i+1)th inversion pulse signal from the N inversion pulse signals performs the first inversion operation on at least the tissue in the imaging region. i is a positive odd number less than or equal to N-2.

[0072] Continue reading Figure 2 , where N is equal to 4. For the solid line periods in the respective cycles corresponding to magnetic resonance images a and b, after (or simultaneously with) inversion pulse signal 3 (the (i+2nd) inversion pulse signal from the end in this example, where i is 1) performs a first inversion operation on at least the tissue in the imaging region, and before inversion pulse signal 2 (the (i+1st) inversion pulse signal from the end in this example) performs the first inversion operation on at least the tissue in the imaging region, a second inversion operation may be performed on the blood in the marked region of the target object (in this example, the first pulse signal a is used to perform the second inversion operation).

[0073] Continue reading Figure 2 The time periods that meet the first preset time condition include time periods TD2 and TD4. If the first time period includes time periods TD2 and TD4 (e.g., magnetic resonance images a and b), the second inversion operation can be performed on the blood in the marked region during time periods TD2 and TD4. If the first time period includes time period TD4 but excludes time period TD2 (e.g., magnetic resonance images c and d), the second inversion operation can be performed on the blood in the marked region during time period TD4. Specifically, using magnetic resonance image a as an example, the longitudinal magnetization direction of the blood flowing into the imaging region between the end of the slice-selective saturation pulse signal generation and the start of the inversion pulse signal 4 is initially positive. This blood first undergoes the second inversion operation in the marked region by the first pulse signal b. Then, it undergoes the first inversion operation in the imaging region, sequentially from inversion pulse signals 4 to 1. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging region is negative. It is understood that after undergoing an inversion operation by an inversion pulse signal, the longitudinal magnetization direction of the blood can change from positive to negative or from negative to positive. For another example, the longitudinal magnetization direction of blood that flows into the imaging area between the end of inversion pulse signal 4 and the start of inversion pulse signal 3 is initially positive. Since this blood undergoes the first inversion operation of inversion pulse signals 3 to 1, the longitudinal magnetization direction of this blood when imaged in the imaging area is also negative.

[0074] The second time preset condition may include: when N is a positive odd number, after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging area, and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on tissue in at least the imaging area.

[0075] See Figure 5 As shown, Figure 5 FIG. 1 is a schematic diagram showing a process of generating a magnetic resonance image f according to an embodiment of the present invention. Figure 5 In the example where N is 3, the period corresponding to the magnetic resonance image f includes the time period TD0 to TD3. During the dashed time period, after the slice-selective saturation pulse signal saturates the tissue in at least the imaging region, and before the inversion pulse signal 3 (the first inversion pulse signal in this example) performs a first inversion operation on the tissue in at least the imaging region, a second inversion operation (in this example, the first pulse signal f is used for this second inversion operation) can be performed on the blood in the marked region of the target object.

[0076] Regardless of any positive integer N, the second preset time condition may include: after or simultaneously with the j+1th inversion pulse signal from the N inversion pulse signals performing the first inversion operation on at least the tissue in the imaging region, and before the jth inversion pulse signal from the N inversion pulse signals performs the first inversion operation on at least the tissue in the imaging region. j is a positive odd number less than or equal to N-1.

[0077] Continue reading Figure 2 , where N is equal to 4. For the dashed period in the respective cycles corresponding to magnetic resonance images b to e, after (or simultaneously with) the first inversion operation performed on at least the tissue in the imaging region by the inversion pulse signal 2 (the j+1th inversion pulse signal from the end in this example, where j may be 1 or 3 and j is 1 here as an example) and before the first inversion pulse signal from the end in this example (the jth inversion pulse signal from the end in this example) performs the first inversion operation on at least the tissue in the imaging region, a second inversion operation may be performed on the blood in the marked region of the target object (in this example, the first pulse signal c is used to perform the above-mentioned second inversion operation).

[0078] Continue reading Figure 2The time period that meets the second preset time condition includes time periods TD1 and TD3. If the second time period includes time periods TD1 and TD3 (for example, magnetic resonance images d and e), the second inversion operation can be performed on the blood in the marked area during time periods TD1 and TD3. If the second time period includes time period TD1 but excludes time period TD3 (for example, magnetic resonance images b and c), the second inversion operation can be performed on the blood in the marked area during time period TD1. Specifically, taking magnetic resonance image e as an example, the longitudinal magnetization direction of the blood that flows into the imaging area between the end of the generation of the slice-selective saturation pulse signal and the start of the generation of the inversion pulse signal 4 is initially positive. This blood undergoes the first inversion operation of the inversion pulse signals 4 to 1 in the imaging area, so the longitudinal magnetization direction of the blood when imaged in the imaging area is positive. For another example, the longitudinal magnetization direction of the blood that flows into the imaging area between the end of the generation of the inversion pulse signal 4 and the start of the generation of the inversion pulse signal 3 is initially positive. The blood first undergoes a second inversion operation in the marking area through the first pulse signal d, and then undergoes a first inversion operation in the imaging area through the inversion pulse signal 3 to 1 in sequence. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging area is also positive.

[0079] Continue reading Figure 5 In this example, the time periods that meet the second preset time condition include time periods TD1 and TD3. If the second time period includes time periods TD1 and TD3 (e.g., magnetic resonance image f), a second inversion operation can be performed on the blood in the marked region during time periods TD1 and TD3. Specifically, using magnetic resonance image f as an example, the longitudinal magnetization direction of the blood that flows into the imaging region between the end of the slice-selective saturation pulse signal generation and the start of the inversion pulse signal 3 is initially positive. This blood first undergoes the second inversion operation of the first pulse signal f in the marked region and then undergoes the first inversion operation of the inversion pulse signal 3 to 1 in the imaging region. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging region is positive. For another example, the longitudinal magnetization direction of the blood that flows into the imaging region between the end of the inversion pulse signal 3 and the start of the inversion pulse signal 2 is initially positive. This blood sequentially undergoes the first inversion operations of the inversion pulse signals 2 and 1. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging region is positive.

[0080] According to the above-described solution of the embodiment of the present invention, the first and second preset time conditions are clearly defined, ensuring that the longitudinal magnetization direction of blood undergoing the second inversion operation in the first time period is negative when imaged in the imaging area, and that the longitudinal magnetization direction of blood undergoing the second inversion operation in the second time period is positive when imaged in the imaging area. The above-described solution determines that the imaging results of blood with negative and positive signals in magnetic resonance imaging are significantly different, thereby improving the display quality of magnetic resonance images. This also facilitates the display quality of magnetic resonance image sequences.

[0081] Exemplarily, within the first time period and when the first time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may include: within the first time period, generating another inversion pulse signal (hereinafter referred to as the first pulse signal) in the marked area to perform a second inversion operation on the blood in the marked area.

[0082] The duration of the first pulse signal may be: the period after the (i+2)th inversion pulse signal from the end performs the first inversion operation on at least the tissue in the imaging area, and before the (i+1)th inversion pulse signal from the end performs the first inversion operation on at least the tissue in the imaging area.

[0083] Continue reading Figure 2 For magnetic resonance images a and b, the duration of the first pulse signal a may be: a period after the inversion pulse signal 3 (the penultimate (i+2) inversion pulse signal in this example, where i is 1 in this example) performs a first inversion operation on at least the tissue in the imaging area, and before the inversion pulse signal 2 performs a first inversion operation on at least the tissue in the imaging area.

[0084] The duration of the first pulse signal may also be: when N is a positive even number, the period after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging area, and before the first inversion pulse signal performs a first inversion operation on tissue in at least the imaging area.

[0085] Continue reading Figure 2 For magnetic resonance images a to d, the duration of the first pulse signal b may be: a period after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging region and before the inversion pulse signal 4 (the first inversion pulse signal in this example) performs a first inversion operation on tissue in at least the imaging region.

[0086] According to the above-described embodiment of the present invention, a first pulse signal can be generated in the marking region during the first time period, and a second inversion operation can be performed on the blood in the marking region using this first pulse signal. In this embodiment, the time interval between the inversion pulse signal used to perform the second inversion operation and the adjacent inversion pulse signal used to perform the first inversion operation is short, allowing for a more effective second inversion operation on the blood about to flow into the imaging region. This facilitates improved display quality of magnetic resonance images, and thereby enhances the display quality of magnetic resonance image sequences.

[0087] Illustratively, within the first time period and when the first time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may include: within the first time period, using the penultimate (i+2) inversion pulse signal to perform a second inversion operation on the blood in the marked area.

[0088] As previously described, the N inversion pulses can perform a first inversion operation on the blood in the background suppression area. The effective range of the (i+2)th inversion pulse signal from the N inversion pulses can be expanded. For example, the effective range of this inversion pulse signal can include both the marked area and the aforementioned background suppression area. In this example, the (i+2)th inversion pulse signal from the last one is used not only to perform the first inversion operation on the tissue in the background suppression area, but also to perform the second inversion operation on the blood in the marked area.

[0089] Continue reading Figure 2 Taking magnetic resonance image a as an example, the second inversion operation can be performed on the blood in the marked area using inversion pulse signal 3 (the penultimate (i+2) inversion pulse signal in this example, where i is 1). In this example, the first pulse signal a is not required.

[0090] In one example, the length of the marking region along the flow direction of the blood to be imaged is equal to a first product. The first product can be the product of the time interval between the (i+2nd) and (i+1st) inversion pulse signals and the blood velocity of the blood to be imaged. The background suppression region can be extended toward the source of the blood to be imaged by the length of the first product to expand the effective range of the (i+2nd) inversion pulse signal. For example, if the blood velocity of the blood to be imaged is 0.03 cm / millisecond and the time interval is 300 milliseconds, the first product can be 9 cm (i.e., 0.03*300). The background suppression region of the inversion pulse signal can be extended by 9 cm to utilize the (i+2nd) inversion pulse signal to pre-invert the longitudinal magnetization direction of the blood about to flow into the imaging region. It will be appreciated that the time interval between the (i+2nd) and (i+1st) inversion pulse signals can vary with i. In other words, the length of the marking region can be different for different inversion pulse signals. The above solution can flexibly configure the effective range of the inversion pulse signal based on the first product, which can avoid the marking area being too large and wasting resources.

[0091] According to the above-described solution of an embodiment of the present invention, within the first time period and if the first preset time condition is met, the second inversion operation can be performed using the penultimate (i+2) inversion pulse signal. This can reduce the total number of inversion pulse signals generated, thereby reducing the configuration cost of magnetic resonance imaging equipment and improving the adaptability of magnetic resonance angiography to different scenarios.

[0092] Exemplarily, within the first time period and when the first time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may also include: within the first time period, using the Nth inversion pulse signal among N inversion pulse signals to perform a second inversion operation on the blood in the marked area.

[0093] Continue reading Figure 2 Taking magnetic resonance image a as an example, a second inversion operation can be performed on the blood in the marked area using inversion pulse signal 1 (the Nth inversion pulse signal in this example). In actual scenarios, blood will continue to flow from the marked area to the imaging area from the time inversion pulse signal 1 is generated to the time signal acquisition begins. Therefore, a second inversion operation can also be performed on this blood to make the longitudinal magnetization direction of the blood negative. Specifically, the longitudinal magnetization direction of the blood is initially positive. After the second inversion operation of inversion pulse signal 1, the longitudinal magnetization direction of the blood when imaged in the imaging area is negative.

[0094] It will be appreciated that N can be 1. During the first time period, the second inversion operation can be performed on the blood in the marked area using the single inversion pulse signal used to perform the first inversion operation. In other words, the inversion pulse signal is used not only to perform the first inversion operation but also to perform the second inversion operation. During the second time period, the second inversion operation can be performed on the blood in the marked area after the slice-selective saturation pulse signal saturates at least the tissue in the imaging area and before the inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area. Figure 6 FIG. 1 is a schematic diagram showing a process of generating magnetic resonance images g and h according to an embodiment of the present invention. Figure 6 In the example of , for magnetic resonance image g, the first time period indicated by the solid line includes TD0 and TD1. A second inversion operation can be performed on the blood in the marked area using inversion pulse signal 1. For magnetic resonance image g, the longitudinal magnetization direction of the blood flowing into the imaging area between the start of inversion pulse signal 1 generation and the start of signal acquisition is initially positive. This blood undergoes the second inversion operation of inversion pulse signal 1 in the marked area. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging area is negative. For magnetic resonance image h, the second time period indicated by the dashed line includes TD0 and TD1. A second inversion operation can be performed on the blood in the marked area using the first pulse signal g. For magnetic resonance image h, the longitudinal magnetization direction of the blood flowing into the imaging area between the end of the slice-selective saturation pulse signal generation and the start of inversion pulse signal 1 is initially positive. This blood first undergoes the second inversion operation of the first pulse signal g in the marked area and then undergoes the first inversion operation of the inversion pulse signal 1 in the imaging area. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging area is positive.

[0095] Exemplarily, within the first time period and when the first time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may also include: within the first time period, generating another inversion pulse signal (hereinafter referred to as the first pulse signal) in the marked area to perform a second inversion operation on the blood in the marked area.

[0096] The duration of the first pulse signal is: after the Nth inversion pulse signal performs a first inversion operation on at least the tissue in the imaging region and before the signal acquisition start time.

[0097] Here Figure 2Taking the medium magnetic resonance image a as an example, after the blood in the imaging area is subjected to the first inversion operation by the inversion pulse signal 1 (the Nth inversion pulse signal in this example), a first pulse signal (not shown) is generated in the marking area. In combination with the actual scenario, from the moment when the generation of the inversion pulse signal 1 ends to the moment when the signal acquisition starts, there will still be blood flowing from the marking area to the imaging area, so the blood can also be subjected to a second inversion operation to make the longitudinal magnetization direction of the blood negative. Specifically, the longitudinal magnetization direction of the blood is initially positive. The blood has undergone the second inversion operation of the first pulse signal, so the longitudinal magnetization direction of the blood when it is imaged in the imaging area is negative.

[0098] As previously mentioned, N can be 1. During the first time period, after the tissue in at least the imaging region is subjected to the first inversion operation by a single inversion pulse signal (e.g., inversion pulse signal 1 in the above example) used to perform the first inversion operation, and before signal acquisition begins, a second inversion operation can be performed on the blood in the marking region using the first pulse signal. In this example, the longitudinal magnetization direction of the blood that flows into the imaging region between the end of generation of the inversion pulse signal and the start of signal acquisition is initially positive. This blood undergoes the second inversion operation of the first pulse signal in the marking region. Therefore, the longitudinal magnetization direction of the blood when imaged in the imaging region is negative. During the second time period, after the tissue in at least the imaging region is saturated by the slice-selective saturation pulse signal, and before the tissue in at least the imaging region is subjected to the first inversion operation by the inversion pulse signal, a second inversion operation can be performed on the blood in the marking region. The second inversion operation during the second time period can be referred to in the above description of the magnetic resonance image h, and will not be further described in detail in this embodiment of the present invention.

[0099] According to the above scheme of the embodiment of the present invention, the Nth inversion pulse signal among the N inversion pulse signals can be used to perform a second inversion operation on the blood in the marked area within the first time period and in compliance with the first time preset condition. It is also possible to generate a first pulse signal in the marked area within the first time period to perform a second inversion operation on the blood in the marked area. The duration of the first pulse signal is: after the Nth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the start time of signal acquisition. Both of the above methods can make the blood that flows from the marked area to the imaging area after the start time of generation of the Nth inversion pulse signal have a negative longitudinal magnetization direction when imaging in the imaging area. This is conducive to improving the display effect of the magnetic resonance image, and thus improving the display effect of the magnetic resonance image sequence.

[0100] Exemplarily, within the second time period and when the second time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may include: within the second time period, generating another inversion pulse signal (hereinafter referred to as the first pulse signal) in the marked area to perform a second inversion operation on the blood in the marked area.

[0101] The duration of the first pulse signal may be: a period after the j+1th inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the jth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area.

[0102] Continue reading Figure 2 For magnetic resonance images d and e, the duration of the first pulse signal c may be a period after inversion pulse signal 2 (the j+1th inversion pulse signal from the end in this example, where j may be 1 or 3 and j is 1 here as an example) performs a first inversion operation on at least the tissue in the imaging region and before inversion pulse signal 1 (the jth inversion pulse signal from the end in this example, where j is 1 here as an example) performs a first inversion operation on at least the tissue in the imaging region. The duration of the first pulse signal d may be a period after inversion pulse signal 4 (the j+1th inversion pulse signal from the end in this example, where j is 3 here as an example) performs a first inversion operation on at least the tissue in the imaging region and before inversion pulse signal 3 (the jth inversion pulse signal from the end in this example, where j is 3 here as an example) performs a first inversion operation on at least the tissue in the imaging region.

[0103] Continue reading Figure 5 In the example where N is 3. For the magnetic resonance image f, the duration of the first pulse signal e may be a period after the inversion pulse signal 2 (the j+1th inversion pulse signal from the end in this example, where j is 1 in this example) performs the first inversion operation on at least the tissue in the imaging region and before the inversion pulse signal 1 (the jth inversion pulse signal from the end in this example) performs the first inversion operation on at least the tissue in the imaging region.

[0104] The duration of the first pulse signal may also be: when N is a positive odd number, the duration of the first pulse signal may be: after the layer-selective saturation pulse signal performs saturation processing on tissue in at least the imaging area, and before the first inversion pulse signal among the N inversion pulse signals performs the first inversion operation on tissue in at least the imaging area.

[0105] Continue reading Figure 5In this example, N is 3. For a magnetic resonance image f, the duration of the first pulse signal f may be a period after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging region and before the inversion pulse signal 3 (the first inversion pulse signal in this example) performs a first inversion operation on tissue in at least the imaging region.

[0106] According to the above-described embodiment of the present invention, a first pulse signal can be generated in the marking region during the second time period, and a second inversion operation can be performed on the blood in the marking region using this first pulse signal. In this embodiment, the time interval between the inversion pulse signal used to perform the second inversion operation and the adjacent inversion pulse signal used to perform the first inversion operation is short, allowing for a more effective second inversion operation on the blood about to flow into the imaging region. This improves the display quality of magnetic resonance images, and thereby enhances the display quality of magnetic resonance image sequences.

[0107] Illustratively, within the second time period and when the second time preset condition is met, the above-mentioned second inversion operation on the blood in the marked area of ​​the target object may include: within the second time period, using the penultimate j+1 inversion pulse signal to perform a second inversion operation on the blood in the marked area.

[0108] As previously described, the N inversion pulses can perform a first inversion operation on the blood in the background suppression area. The effective range of the (j+1)th inversion pulse signal from the N inversion pulses can be expanded. For example, the effective range of this inversion pulse signal can include both the marked area and the aforementioned background suppression area. In this example, the (j+1)th inversion pulse signal from the last one not only performs the first inversion operation on the tissue in the background suppression area, but also performs the second inversion operation on the blood in the marked area.

[0109] Continue reading Figure 2 Taking magnetic resonance images d and e as an example, the second inversion operation can be performed on the blood in the marked area using inversion pulse signal 4 and inversion pulse signal 2 (the j+1th inversion pulse signal from the end in this example, where j can be 3 or 1). In this example, the first pulse signals c and d are not required.

[0110] In one example, the length of the marking region along the flow direction of the blood to be imaged is equal to the second product. The second product may be the product of the time interval between the penultimate j+1 inversion pulse signal and the penultimate j inversion pulse signal and the blood flow velocity of the blood to be imaged.

[0111] The background suppression area can be extended by the length of the second product toward the side of the source of the blood to be imaged to expand the range of action of the j+1th inversion pulse signal from the end. For example, if the blood flow velocity of the blood flow to be imaged is 0.03 cm per millisecond and the above time interval is 300 milliseconds, the second product can be 9 cm (i.e., 0.03*300). The background suppression area of ​​the inversion pulse signal can be extended by 9 cm to utilize the j+1th inversion pulse signal from the end to pre-reverse the longitudinal magnetization direction of the blood that is about to flow into the imaging area. It can be understood that the time interval between the j+1th inversion pulse signal from the end and the jth inversion pulse signal from the end can change with the change of j. In other words, the above length of the marking area can be different for different inversion pulse signals. The above scheme can flexibly configure the range of action of the inversion pulse signal based on the second product. This can avoid the marking area being too large and wasting resources.

[0112] According to the above-described solution of an embodiment of the present invention, within the second time period and if the second preset time condition is met, the penultimate (j+1) inversion pulse signal can be used to perform the second inversion operation. This can reduce the total number of inversion pulse signals generated, which helps reduce the configuration costs of the host computer and scanner, and improve the adaptability of magnetic resonance angiography to different scenarios.

[0113] Exemplarily, acquiring magnetic resonance signals of tissues in the imaging region and generating the magnetic resonance image based on the acquired magnetic resonance signals in step S120 may include: step S121a and step S122a.

[0114] In step S121a, magnetic resonance signals of tissues are acquired in the imaging region based on a center-first sampling mode of the K-space, and data filling is performed on the K-space based on the acquired magnetic resonance signals.

[0115] K space can be used to store data of magnetic resonance images in the frequency domain. In magnetic resonance imaging, the collected data can be filled into the K space, and then the data in the frequency domain can be converted into data in the spatial domain (or image domain) to obtain a magnetic resonance image. The above-mentioned center-priority sampling mode can give priority to sampling the central area in the K space. The central area in the K space is usually related to the low-frequency component in the magnetic resonance image. The low-frequency component can represent the basic structural information of the tissue in the magnetic resonance image. Therefore, the use of the center-priority sampling mode helps to quickly generate magnetic resonance images that show the real physical differences between the imaged tissues. The above-mentioned central area may include multiple rows of space located in the middle of the K space. The specific number of rows can be determined by the developer or user based on actual needs, and the embodiment of the present invention does not limit this.

[0116] Each row of data in K-space can correspond to an encoding gradient. The host computer can send the encoding gradient to the gradient coils in the scanner to generate a gradient magnetic field. Magnetic resonance signals generated by this gradient magnetic field can be acquired and populated into the K-space corresponding to the encoding gradient. In this embodiment, magnetic resonance signals can be acquired preferentially based on the encoding gradient corresponding to the central region, achieving center-priority sampling.

[0117] In step S122a, the magnetic resonance image is generated based on the data in the filled K space.

[0118] The data in K-space can be converted into data in the spatial domain through an inverse Fourier transform to obtain a magnetic resonance image. It can be understood that if K-space is a two-dimensional space, a two-dimensional magnetic resonance image can be obtained, and if K-space is a three-dimensional space, multiple two-dimensional magnetic resonance images can be obtained.

[0119] According to the above-described solution of an embodiment of the present invention, magnetic resonance signals of tissues in the imaging region can be acquired using a center-priority sampling mode in K-space. Based on the acquired magnetic resonance signals, data is then filled into the K-space. Finally, the magnetic resonance image is generated based on the data in the filled K-space. Users are generally more interested in data in the central region of K-space. Therefore, the above-described solution utilizes a center-priority sampling mode to fill the K-space, which facilitates the rapid generation of magnetic resonance image sequences that depict realistic physical differences between imaged tissues and better meets the actual needs of users.

[0120] Exemplarily, generating the magnetic resonance image based on the acquired magnetic resonance signals in step S120 may include: step S121b and step S122b.

[0121] In step S121b, data filling is performed on the K space based on the acquired magnetic resonance signals.

[0122] The embodiment of the present invention does not limit the specific method of filling the K space with data, which can be determined according to the actual needs of the developer or user. In one example, the center-first sampling mode can also be used to fill the K space with data.

[0123] In step S122b, the magnetic resonance image is generated based on the data in the filled K space by a spatiotemporal joint reconstruction algorithm.

[0124] Spatiotemporal joint reconstruction (also known as spatiotemporal joint reconstruction) algorithms can rapidly generate magnetic resonance images by undersampling data in k-space. For example, spatiotemporal joint reconstruction algorithms can be based on compressed sensing, low-rank matrix / tensor decomposition, deep learning, or golden flip angle. In one example, the spatiotemporal joint reconstruction algorithm can also generate additional magnetic resonance images based on data in populated k-space obtained at different times (e.g., data in k-space used to generate different magnetic resonance images). This can increase the total number of magnetic resonance images in a magnetic resonance image sequence, which helps improve the visual fluency of the magnetic resonance image sequence.

[0125] It is understood that the relevant contents of steps S121a and S122a can also be used in conjunction with the relevant contents of steps S121b and S122b. For example, a center-first sampling mode can be used to fill the K-space with data. A spatiotemporal joint reconstruction algorithm can then be used to undersample the data in the filled K-space to generate a magnetic resonance image.

[0126] According to the above-described solution of an embodiment of the present invention, data can be filled into the K-space based on the acquired magnetic resonance signals. A magnetic resonance image can then be generated using a spatiotemporal joint reconstruction algorithm based on the data in the filled K-space. This solution utilizes the spatiotemporal joint reconstruction algorithm to rapidly generate magnetic resonance images, thereby improving the efficiency of magnetic resonance image generation.

[0127] An embodiment of the present invention also provides a magnetic resonance imaging device. Figure 7 FIG2 shows a schematic block diagram of a magnetic resonance imaging device 200 according to an embodiment of the present invention. Figure 7 As shown, the magnetic resonance imaging apparatus 200 may include a processor 210 and an execution device 220 .

[0128] For each magnetic resonance image to be generated in the magnetic resonance image sequence, the processor 210 is configured to control the execution device 220 to perform the following steps: sequentially generate a layer-selective saturation pulse signal and N inversion pulse signals in at least the imaging area of ​​the target object. The N inversion pulse signals are used to perform a first inversion operation on the tissue in at least the imaging area. In the first time period and when the first time preset condition is met, and in the second time period and when the second time preset condition is met, a second inversion operation is performed on the blood in the marked area of ​​the target object, so that the longitudinal magnetization direction of the blood subjected to the second inversion operation in the first time period is negative when the imaging area is imaged. And the longitudinal magnetization direction of the blood subjected to the second inversion operation in the second time period is positive when the imaging area is imaged. In the period of generating the layer-selective saturation pulse signal and the N inversion pulse signals, there is a conversion moment corresponding to the magnetic resonance image,

[0129] The first time period is the time period before the switching moment in the cycle, and the second time period is the time period after the switching moment in the cycle. N is a positive integer. The marking region is adjacent to the imaging region, and the blood to be imaged flows into the imaging region through the marking region. Magnetic resonance signals of tissue in the imaging region are acquired.

[0130] The execution device 220 may include a scanner. The scanner is used to apply a main magnetic field, a radio frequency pulse signal, and acquire magnetic resonance signals. The specific functions of the scanner can be found in the description of step S110.

[0131] The processor 210 is further configured to generate the magnetic resonance image based on the acquired magnetic resonance signal. The later the position of the magnetic resonance image in the magnetic resonance image sequence is, the earlier the corresponding conversion moment is in the cycle.

[0132] Illustratively, the first preset time condition includes: when N is a positive even number, after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging region and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on tissue in at least the imaging region, or after or simultaneously with the (i+2)th to last inversion pulse signal among the N inversion pulse signals performing the first inversion operation on tissue in at least the imaging region and before the (i+1)th to last inversion pulse signal among the N inversion pulse signals performs the first inversion operation on tissue in at least the imaging region. Wherein, i is a positive odd number less than or equal to N-2.

[0133] The second preset time condition includes: when N is a positive odd number, after the slice-selective saturation pulse signal performs saturation processing on tissue in at least the imaging region and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on tissue in at least the imaging region, or after or simultaneously with the j+1th inversion pulse signal from the last of the N inversion pulse signals performing the first inversion operation on tissue in at least the imaging region and before the jth inversion pulse signal from the last of the N inversion pulse signals performs the first inversion operation on tissue in at least the imaging region. Wherein, j is a positive odd number less than or equal to N-1.

[0134] Exemplarily, within a first time period and when a first preset time condition is met, the processor 210 controls the execution device 220 to perform a second inversion operation on the blood in the marked area of ​​the target object, and is further configured to: generate another inversion pulse signal (hereinafter referred to as the first pulse signal) in the marked area within the first time period to perform the second inversion operation on the blood in the marked area. The duration of the first pulse signal is: a period after the (i+2)th inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the (i+1)th inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area, and, when N is a positive even number, a period after the slice-selective saturation pulse signal performs saturation processing on at least the tissue in the imaging area and before the first inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area.

[0135] Exemplarily, within the first time period and when the first time preset condition is met, the processor 210 controls the execution device 220 to perform a second inversion operation on the blood in the marked area of ​​the target object, and is further configured to: within the first time period, use the penultimate (i+2)th inversion pulse signal to perform a second inversion operation on the blood in the marked area.

[0136] Exemplarily, within a first time period and when a first preset time condition is met, the processor 210 controls the execution device 220 to perform a second inversion operation on the blood in the marked area of ​​the target object, and is further configured to: within the first time period, use the Nth inversion pulse signal among the N inversion pulse signals to perform the second inversion operation on the blood in the marked area. Alternatively, within the first time period, generate a first pulse signal in the marked area to perform the second inversion operation on the blood in the marked area. The duration of the first pulse signal is: after the Nth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the start of signal acquisition.

[0137] Exemplarily, within the second time period and when the second preset time condition is met, the processor 210 controls the execution device 220 to perform a second inversion operation on the blood in the marked area of ​​the target object, and is further configured to: generate a first pulse signal in the marked area within the second time period to perform the second inversion operation on the blood in the marked area. The duration of the first pulse signal is: a period after the j+1th inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the jth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area, and, when N is a positive odd number, a period after the slice-selective saturation pulse signal performs saturation processing on at least the tissue in the imaging area and before the first inversion pulse signal among the N inversion pulse signals performs the first inversion operation on at least the tissue in the imaging area.

[0138] Exemplarily, within the second time period and when the second time preset condition is met, the processor 210 controls the execution device 220 to perform a second inversion operation on the blood in the marked area of ​​the target object, and is further configured to: within the second time period, use the penultimate j+1 inversion pulse signal to perform a second inversion operation on the blood in the marked area.

[0139] Exemplarily, the processor 210 controls the execution device 220 to sequentially generate a layer-selected saturation pulse signal and N inversion pulse signals in at least the imaging region of the target object, and is further configured to sequentially generate a layer-selected saturation pulse signal and N inversion pulse signals in the background suppression region of the target object. The background suppression region includes the imaging region, and the background suppression region and the imaging region have the same edge adjacent to the marking region. Furthermore, in the flow direction of the blood to be imaged, the length of the background suppression region is greater than or equal to the maximum value among the first values. The first value comprises the product of the time interval between each two adjacent target pulse signals and the blood flow velocity of the blood to be suppressed. The target pulse signal includes the layer-selected saturation pulse signal and the N inversion pulse signals.

[0140] Exemplarily, the processor 210 controls the execution device 220 to acquire magnetic resonance signals of tissue in an imaging region, and the processor 210 generates the magnetic resonance image based on the acquired magnetic resonance signals. The processor 210 is further configured to: acquire magnetic resonance signals of tissue in the imaging region based on a center-first sampling mode of K-space, and perform data filling of the K-space based on the acquired magnetic resonance signals. The magnetic resonance image is generated based on the data in the filled K-space.

[0141] Exemplarily, the processor 210 generates the magnetic resonance image based on the acquired magnetic resonance signals and is further configured to: fill the K-space with data based on the acquired magnetic resonance signals, and generate the magnetic resonance image using a spatiotemporal joint reconstruction algorithm based on the data in the filled K-space.

[0142] According to another aspect of the present invention, a non-volatile storage medium is provided. The non-volatile storage medium stores program instructions, which, when executed by a computer or processor, cause the computer or processor to perform the corresponding steps of the magnetic resonance angiography method according to an embodiment of the present invention and implement the corresponding modules in the magnetic resonance imaging apparatus according to an embodiment of the present invention. The non-volatile storage medium may include, for example, a memory card in a smartphone, a storage component in a tablet computer, a hard disk in a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disc read-only memory (CD-ROM), a USB memory, or any combination of the foregoing non-volatile storage media.

[0143] According to another aspect of the present invention, a computer program product is provided, comprising computer program instructions, which, when executed by a computer or a processor, enable the computer or processor to perform corresponding steps of the magnetic resonance angiography method.

[0144] A person skilled in the art can understand the specific implementation scheme of the magnetic resonance imaging device and the non-volatile storage medium by reading the above description of the magnetic resonance angiography method, and for the sake of brevity, it is not repeated here.

[0145] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely illustrative and are not intended to limit the scope of the present invention. Various changes and modifications may be made therein by those skilled in the art without departing from the scope and spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as claimed in the appended claims.

[0146] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0147] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units described is merely a logical functional division. In actual implementation, other division methods may be used. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not implemented.

[0148] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0149] Similarly, it should be understood that in order to streamline the present invention and aid in understanding one or more of the various inventive aspects, in the description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this approach to the present invention should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly recited in each claim. More precisely, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with fewer features than all the features of a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0150] It will be understood by those skilled in the art that, except where mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or apparatus disclosed herein may be combined in any combination. 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.

[0151] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

[0152] The various component embodiments of the present invention may be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will appreciate that, in practice, a microprocessor or digital signal processor (DSP) may be used to implement some or all of the functions of some modules in a magnetic resonance imaging device according to an embodiment of the present invention. The present invention may also be implemented as a device program (e.g., a computer program or computer program product) for performing part or all of the methods described herein. Such a program implementing the present invention may be stored on a computer-readable medium or in the form of one or more signals. Such signals may be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0153] It should be noted that the above embodiments illustrate rather than limit the invention, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising several different elements and by means of appropriately programmed computers. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0154] The foregoing description is merely a specific embodiment of the present invention or an illustration of a specific embodiment. The scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed in the present invention are intended to be encompassed by the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A magnetic resonance angiography method, characterized in that: The method comprises: For each magnetic resonance image to be generated in the magnetic resonance image sequence, Sequentially generating a slice-selective saturation pulse signal and N inversion pulse signals in at least an imaging region of a target object, wherein the N inversion pulse signals are used to perform a first inversion operation on tissue in at least the imaging region, and performing a second inversion operation on blood in a marking region of the target object both within a first time period and when a first preset time condition is met, and within a second time period and when a second preset time condition is met, such that the longitudinal magnetization direction of the blood subjected to the second inversion operation in the first time period is negative when imaging the imaging region, and the longitudinal magnetization direction of the blood subjected to the second inversion operation in the second time period is positive when imaging the imaging region, within a period for generating the slice-selective saturation pulse signal and the N inversion pulse signals, there is a transition moment corresponding to the magnetic resonance image, the first time period is a period before the transition moment in the period, and the second time period is a period after the transition moment in the period, N is a positive integer, the marking region is adjacent to the imaging region, and the blood to be imaged flows into the imaging region via the marking region; Acquiring magnetic resonance signals of tissue in the imaging region, and generating the magnetic resonance image based on the acquired magnetic resonance signals; The later the position of the magnetic resonance image in the magnetic resonance image sequence is, the earlier the corresponding conversion moment is in the cycle.

2. The method according to claim 1, wherein The first time preset condition includes: When N is a positive even number, after the slice-selective saturation pulse signal performs a saturation process on at least the tissue in the imaging region, and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on at least the tissue in the imaging region; or after or simultaneously with the (i+2)th inversion pulse signal from the N inversion pulse signals performing a first inversion operation on at least the tissue in the imaging region, and before the (i+1)th inversion pulse signal from the N inversion pulse signals performs a first inversion operation on at least the tissue in the imaging region, wherein i is a positive odd number less than or equal to N-2; The second time preset condition includes: When N is a positive odd number, after the slice-selective saturation pulse signal performs a saturation process on at least the tissue in the imaging region, and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on at least the tissue in the imaging region; or After or simultaneously with the j+1th inversion pulse signal from the N inversion pulse signals performing the first inversion operation on the tissue in at least the imaging area, and before the jth inversion pulse signal from the N inversion pulse signals performs the first inversion operation on the tissue in at least the imaging area, where j is a positive odd number less than or equal to N-1.

3. The method according to claim 2, wherein The step of performing a second inversion operation on the blood in the marked area of ​​the target object within the first time period and when the first preset time condition is met includes: During the first period, another inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area. The duration of the additional inversion pulse signal is: a period after the (i+2)th inversion pulse signal from the end performs a first inversion operation on at least the tissue in the imaging area and before the (i+1)th inversion pulse signal from the end performs a first inversion operation on at least the tissue in the imaging area, and, when N is a positive even number, a period after the layer-selective saturation pulse signal performs saturation processing on at least the tissue in the imaging area and before the first inversion pulse signal performs a first inversion operation on at least the tissue in the imaging area.

4. The method according to claim 2, wherein The step of performing a second inversion operation on the blood in the marked area of ​​the target object within the first time period and when the first preset time condition is met includes: In the first time period, the second inversion operation is performed on the blood in the marking area using the penultimate (i+2) inversion pulse signal.

5. The method according to claim 2, wherein The performing of a second inversion operation on the blood in the marked area of ​​the target object within the first time period and when the first preset time condition is met further includes any one of the following: In a first time period, using an Nth inversion pulse signal among the N inversion pulse signals to perform a second inversion operation on the blood in the marked area; During the first time period, an additional inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area, wherein the duration of the additional inversion pulse signal is: after the Nth inversion pulse signal performs the first inversion operation on at least the tissue in the imaging area and before the start time of signal acquisition.

6. The method according to claim 2, wherein The step of performing a second inversion operation on the blood in the marked area of ​​the target object within the second time period and when a second preset time condition is met includes: During a second period, another inversion pulse signal is generated in the marking area to perform a second inversion operation on the blood in the marking area. The duration of the additional inversion pulse signal is: a period after the j+1th inversion pulse signal performs a first inversion operation on at least the tissue in the imaging area and before the jth inversion pulse signal performs a first inversion operation on at least the tissue in the imaging area, and, when N is a positive odd number, a period after the layer-selective saturation pulse signal performs saturation processing on at least the tissue in the imaging area and before the first inversion pulse signal among the N inversion pulse signals performs a first inversion operation on at least the tissue in the imaging area.

7. The method according to claim 2, wherein The step of performing a second inversion operation on the blood in the marked area of ​​the target object within the second time period and when a second preset time condition is met includes: In the second time period, the second inversion operation is performed on the blood in the marking area using the penultimate (j+1)th inversion pulse signal.

8. The method according to claim 1, wherein The sequentially generating the slice-selective saturation pulse signal and the N inversion pulse signals in at least the imaging area of ​​the target object comprises: A layer-selected saturation pulse signal and N inversion pulse signals are sequentially generated in a background suppression area of ​​the target object, wherein the background suppression area includes the imaging area, the background suppression area and the imaging area have the same edge adjacent to the marking area, and in the flow direction of the blood to be imaged, the length of the background suppression area is greater than or equal to the maximum value of the first values, the first value includes the product of the time interval between each two adjacent target pulse signals and the blood flow velocity of the blood to be suppressed, and the target pulse signal includes the layer-selected saturation pulse signal and the N inversion pulse signals.

9. The method according to claim 1, wherein The acquiring magnetic resonance signals of tissue in the imaging region and generating the magnetic resonance image based on the acquired magnetic resonance signals includes: Based on a center-first sampling mode of K space, magnetic resonance signals of tissue are collected in the imaging region, and data filling is performed on the K space based on the collected magnetic resonance signals; The magnetic resonance image is generated based on the data in the filled K-space.

10. The method according to any one of claims 1 to 9, characterized in that Generating the magnetic resonance image based on the acquired magnetic resonance signal includes: Filling the K space with data based on the acquired magnetic resonance signals; The magnetic resonance image is generated based on the data in the filled K space through a spatiotemporal joint reconstruction algorithm.

11. A magnetic resonance imaging device, characterized in that: The apparatus includes a processor and an execution device. For each magnetic resonance image to be generated in a magnetic resonance image sequence, the processor is configured to control the execution device to perform the following steps: Sequentially generating a slice-selective saturation pulse signal and N inversion pulse signals in at least an imaging region of a target object, wherein the N inversion pulse signals are used to perform a first inversion operation on tissue in at least the imaging region, and performing a second inversion operation on blood in a marking region of the target object both within a first time period and when a first preset time condition is met, and within a second time period and when a second preset time condition is met, such that the longitudinal magnetization direction of the blood subjected to the second inversion operation in the first time period is negative when imaging the imaging region, and the longitudinal magnetization direction of the blood subjected to the second inversion operation in the second time period is positive when imaging the imaging region, within a period for generating the slice-selective saturation pulse signal and the N inversion pulse signals, there is a transition moment corresponding to the magnetic resonance image, the first time period is a period before the transition moment in the period, and the second time period is a period after the transition moment in the period, N is a positive integer, the marking region is adjacent to the imaging region, and the blood to be imaged flows into the imaging region via the marking region; acquiring magnetic resonance signals of tissue in the imaging region; The processor is further configured to generate the magnetic resonance image based on the acquired magnetic resonance signals; The later the position of the magnetic resonance image in the magnetic resonance image sequence is, the earlier the corresponding conversion moment is in the cycle.

12. A non-volatile storage medium storing computer program instructions, characterized in that: When the computer program instructions are executed by a processor, the computer program instructions are used to perform the magnetic resonance angiography method according to any one of claims 1 to 10.

13. A computer program product comprising computer program instructions, characterized in that When the computer program instructions are executed by a processor, the computer program instructions are used to perform the magnetic resonance angiography method according to any one of claims 1 to 10.

Images