Transverse relaxation time constant quantitative imaging method and device and magnetic resonance imaging system

Abstract

The invention relates to the technical field of magnetic resonance quantitative imaging, and provides a transverse relaxation time constant quantitative imaging method, a transverse relaxation time constant quantitative imaging device and a magnetic resonance imaging system, which can separate a stimulated echo signal from a spin echo signal so as to obtain a T2 quantitative image which is not influenced by the stimulated echo signal. The method comprises the following steps: acquiring a first multi-echo spin echo sequence; adjusting the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence; scanning by using a second multi-echo spin echo sequence to perform transverse relaxation time constant quantitative imaging; wherein the adjustment comprises the steps of adjusting the size of at least one of a pre-dispersed phase gradient and a read-out gradient of the first multi-echo spin echo sequence, so that the size of the pre-dispersed phase gradient is not equal to half of the size of the read-out gradient; the adjustment further comprises the step of adding a pair of gradients with the same size and polarity before and after a second radio frequency pulse of the first multi-echo spin echo sequence.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic resonance quantitative imaging, and particularly to a method and device for transverse relaxation time constant quantitative imaging, a magnetic resonance imaging system, a storage medium, and a computer program product. Background Art

[0002] In transverse relaxation time constant (T2) quantitative imaging, in some scenarios, the multi-echo spin echo (ME_SE) method is used. This method has a relatively short scanning time. However, since the radiofrequency pulse cannot perfectly achieve a 180° flip angle, in the echo signals collected by this method for T2 quantitative imaging, in addition to the spin echo signals, stimulated echo signals are also mixed, which affects the accuracy of the T2 quantitative results. Summary of the Invention

[0003] Based on this, in view of the above technical problems, it is necessary to provide a method and device for transverse relaxation time constant quantitative imaging, a magnetic resonance imaging system, a storage medium, and a computer program product.

[0004] The present application provides a method for transverse relaxation time constant quantitative imaging, the method comprising:

[0005] Obtaining a first multi-echo spin echo sequence;

[0006] Adjusting the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence;

[0007] Scanning using the second multi-echo spin echo sequence for transverse relaxation time constant quantitative imaging;

[0008] wherein the adjustment includes: adjusting the magnitude of at least one of the prephasing gradient and the readout gradient in the first multi-echo spin echo sequence such that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient; the adjustment further includes: adding a pair of gradients with the same magnitude and polarity before and after the second radiofrequency pulse in the first multi-echo spin echo sequence.

[0009] In one embodiment, the method further comprises:

[0010] Adjusting the magnitude of the prephasing gradient such that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient.

[0011] In one embodiment, the adjusting the magnitude of the prephasing gradient such that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient includes:

[0012] Take half of the magnitude of the readout gradient as the adjustment standard value;

[0013] Determine the magnitude of the pre-spoiler gradient within a range less than the adjustment standard value or within a range greater than the adjustment standard value.

[0014] In one embodiment, after adjustment, the number of the pre-spoiler gradients is single or two.

[0015] In one embodiment, when the number of the pre-spoiler gradients is single after adjustment:

[0016] After adjustment, the application time of the pre-spoiler gradient is before the second radio frequency pulse;

[0017] Or, after adjustment, the application time of the pre-spoiler gradient is after the second radio frequency pulse.

[0018] In one embodiment, when the number of the pre-spoiler gradients is two after adjustment:

[0019] After adjustment, the application time of one of the two pre-spoiler gradients is before the second radio frequency pulse, and the application time of the other pre-spoiler gradient of the two pre-spoiler gradients is after the second radio frequency pulse.

[0020] In one embodiment, the adjustment further includes: adding spoiling gradients in the slice selection gradient direction, the phase encoding direction, and the readout gradient direction after the application time of the third readout gradient of the first multi-echo spin echo sequence.

[0021] This application provides a magnetic resonance imaging device, and the device includes:

[0022] A sequence acquisition module, configured to acquire a first multi-echo spin echo sequence;

[0023] A sequence adjustment module, configured to adjust the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence;

[0024] A quantitative imaging module, configured to perform transverse relaxation time constant quantitative imaging by scanning using the second multi-echo spin echo sequence;

[0025] Wherein, the adjustment includes: adjusting the magnitude of at least one of the pre-spoiler gradient and the readout gradient of the first multi-echo spin echo sequence so that the magnitude of the pre-spoiler gradient is not equal to half of the magnitude of the readout gradient; the adjustment further includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin echo sequence.

[0026] The present application provides a magnetic resonance imaging system, including a memory and a processor. The memory stores a computer program, and the processor executes the above method.

[0027] The present application provides a computer-readable storage medium, on which a computer program is stored, and the computer program is executed by a processor to perform the above method.

[0028] The present application provides a computer program product, on which a computer program is stored, and the computer program is executed by a processor to perform the above method.

[0029] After obtaining a first multi-echo spin-echo sequence, the present application adjusts the first multi-echo spin-echo sequence to obtain a second multi-echo spin-echo sequence; uses the second multi-echo spin-echo sequence for scanning to perform transverse relaxation time constant quantitative imaging; the adjustment of the first multi-echo spin-echo sequence by the present application includes: adjusting the magnitude of at least one of the pre-dephasing gradient and the readout gradient of the first multi-echo spin-echo sequence so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient, and adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin-echo sequence, whereby a plurality of spin-echo signals without mixed stimulated echo signals can be obtained, and thus a T2 quantitative image not affected by the stimulated echo signals can be obtained, improving the accuracy of the T2 quantitative result. Description of the Drawings

[0030] Figure 1 Schematic diagram of the multi-echo spin-echo sequence before adjustment in one embodiment;

[0031] Figure 2 Schematic diagram of the echo signals acquired in one embodiment;

[0032] Figure 3 Schematic diagram of the flow of the transverse relaxation time constant quantitative imaging method in one embodiment;

[0033] Figure 4 Schematic diagram of the multi-echo spin-echo sequence after adjustment in one embodiment;

[0034] Figure 5 Schematic diagram of the multi-echo spin-echo sequence after adjustment in another embodiment;

[0035] Figure 6 Schematic diagram of the multi-echo spin-echo sequence after adjustment in yet another embodiment;

[0036] Figure 7 Schematic diagram of the multi-echo spin-echo sequence after adjustment in still another embodiment;

[0037] Figure 8Schematic diagram after adjustment of a multi - echo spin - echo sequence in another embodiment;

[0038] Figure 9 Structural block diagram of a magnetic resonance imaging device in one embodiment;

[0039] Figure 10 Internal structure diagram of a processing device in one embodiment. Specific implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] Referring to "embodiments" in the present application means that specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application may be combined with other embodiments.

[0042] In the field of magnetic resonance imaging, any radio - frequency pulse has three components: 0°, 90° and 180°. Under the action of the 90° component of the radio - frequency pulse, a FID signal (free induction decay signal) will be generated; after the FID signal is acted on by the 180° component of a certain radio - frequency pulse, a spin - echo signal will be generated once; after the spin - echo signal is acted on by the 180° component of a certain radio - frequency pulse, a secondary spin - echo signal will be generated; after the secondary spin - echo signal is acted on by the 180° component of a certain radio - frequency pulse, a tertiary spin - echo signal will be generated. The above - mentioned primary spin - echo signal, secondary spin - echo signal and tertiary spin - echo signal all belong to spin - echo signals. Generating a spin - echo signal involves at least two radio - frequency pulses, that is, a spin - echo signal is generated under the action of the 90° component of one radio - frequency pulse and the 180° component of another radio - frequency pulse.

[0043] After the FID signal is acted on by the 90° components of two radio - frequency pulses, or after the spin - echo signal is acted on by the 90° components of two radio - frequency pulses, a stimulated echo signal will be generated; generating a stimulated echo signal involves at least three radio - frequency pulses, that is, a stimulated echo signal is generated under the action of the 90° components of three radio - frequency pulses.

[0044] In T2 quantitative imaging, using the multi-echo spin echo method, a first spin echo signal, a second spin echo signal, and a third spin echo signal can be acquired. An image can be formed based on the first spin echo signal, an image can be formed based on the second spin echo signal, and an image can be formed based on the third spin echo signal. These three images have different contrasts due to the different echo formation times. Based on the three images with different contrasts, a T2 quantitative image can be generated by fitting.

[0045] The following is an introduction in combination with the sequence used in the multi-echo spin echo method. In the following introduction, the sequence used in the multi-echo spin echo method can be referred to as the ME_SE sequence (multi-echo spin echo sequence).

[0046] Refer to Figure 1 , Figure 1 as the ME_SE sequence, Figure 1 shows 6 radiofrequency pulses of the sequence. In the order of the application time, these 6 radiofrequency pulses are respectively denoted as ①, ②, ③, ④, ⑤, and ⑥. Under the action of radiofrequency pulse ①, an FID signal will be generated. After the FID signal is acted on by radiofrequency pulse ②, a first spin echo signal can be generated. After the first spin echo signal is acted on by radiofrequency pulse ③, a second spin echo signal can be generated. After the second spin echo signal is acted on by radiofrequency pulse ④, a third spin echo signal can be generated. After the third spin echo signal is acted on by radiofrequency pulse ⑤, a fourth spin echo signal can be generated. After the fourth spin echo signal is acted on by radiofrequency pulse ⑥, a fifth spin echo signal can be generated, as Figure 2 shown.

[0047] After the FID signal generated by radiofrequency pulse ① is acted on by radiofrequency pulses ② and ③, a stimulated echo signal will be generated. This stimulated echo signal is generated under the action of radiofrequency pulses ①, ②, and ③, corresponding to Figure 2 the first stimulated echo shown. After the FID signal generated by radiofrequency pulse ② is acted on by radiofrequency pulses ③ and ④, a stimulated echo signal will also be generated. This stimulated echo signal is generated under the action of radiofrequency pulses ②, ③, and ④, corresponding to Figure 2 the second stimulated echo shown. After the FID signal generated by radiofrequency pulse ③ is acted on by radiofrequency pulses ④ and ⑤, a stimulated echo signal will also be generated. This stimulated echo signal is generated under the action of radiofrequency pulses ③, ④, and ⑤, corresponding to Figure 2 the third stimulated echo shown. After the FID signal generated by radiofrequency pulse ④ is acted on by radiofrequency pulses ⑤ and ⑥, a stimulated echo signal will also be generated. This stimulated echo signal is generated under the action of radiofrequency pulses ④, ⑤, and ⑥, corresponding to Figure 2The fourth stimulated echo shown. In addition, the aforementioned spin echo will also generate a stimulated echo after being affected by two radio frequency pulses, and even the aforementioned stimulated echo will generate a stimulated echo after being affected by two radio frequency pulses, which will not be elaborated here.

[0048] If the application time interval between radio frequency pulse ① and radio frequency pulse ② is denoted as t, the interval between the application time of radio frequency pulse ② and the formation time of the maximum value of a spin echo signal is also t. When the application time interval between radio frequency pulse ② and radio frequency pulse ③ is 2t, the interval between the formation time of the maximum value of a spin echo signal and the application time of radio frequency pulse ③ is t. At this time, since the secondary spin echo signal is formed by the action of radio frequency pulse ③ on the primary spin echo signal, the interval between the application time of radio frequency pulse ③ and the formation time of the maximum value of the secondary spin echo signal is also t. Since the first stimulated echo signal is generated after the FID signal generated by radio frequency pulse ① is affected by radio frequency pulses ② and ③, the interval between the application time of radio frequency pulse ③ and the formation time of the maximum value of the first stimulated echo signal is t, that is, after the application of radio frequency pulse ③, after a lapse of t, the secondary spin echo signal will form a maximum value, and the first stimulated echo signal will also form a maximum value. It can be seen that the secondary spin echo signal and the first stimulated echo signal overlap in formation time, resulting in the secondary spin echo signal and the first stimulated echo signal being mixed together. Therefore Figure 1 Echo2 shown is an echo signal formed by mixing the secondary spin echo signal and the first stimulated echo signal; similarly, the tertiary spin echo signal and the second stimulated echo signal will also be mixed together, Figure 1 Echo3 shown is an echo signal formed by mixing the tertiary spin echo signal and the second stimulated echo signal. Thus, the collected spin echo signal is mixed with the stimulated echo signal, resulting in the T2 quantitative image formed based on the spin echo signal being affected by the stimulated echo signal, affecting the T2 quantitative result.

[0049] Based on this, the present application provides a method for quantitatively imaging the transverse relaxation time constant. Based on the adjusted multi-echo spin echo sequence, the spin echo signal and the stimulated echo signal can be separated in formation time, so as to collect a spin echo signal that is not mixed with the stimulated echo signal, form a T2 quantitative image that is not affected by the stimulated echo signal, and improve the accuracy of the T2 quantitative result.

[0050] The method provided by the present application can be applied to a magnetic resonance imaging system, including Figure 3 The steps shown:

[0051] Step S301, obtaining a first multi-echo spin echo sequence.

[0052] In order to distinguish between the multi - echo spin - echo sequences before and after adjustment, the multi - echo spin - echo sequence before adjustment can be referred to as the first multi - echo spin - echo sequence, and the multi - echo spin - echo sequence after adjustment can be referred to as the second multi - echo spin - echo sequence.

[0053] The first multi - echo spin - echo sequence may include at least three radio - frequency pulses. These radio - frequency pulses have a sequential application time and can be distinguished by "first / second / third", etc. The first radio - frequency pulse is the radio - frequency pulse applied first (such as Figure 1 the radio - frequency pulse ① shown), and the second radio - frequency pulse is the radio - frequency pulse applied next (such as Figure 1 the radio - frequency pulse ② shown).

[0054] In the first multi - echo spin - echo sequence, if the application time interval between the first radio - frequency pulse and the second radio - frequency pulse is denoted as t, the application time interval between every two adjacent radio - frequency pulses starting from the second radio - frequency pulse is 2t. For example, the application time interval between the second radio - frequency pulse and the third radio - frequency pulse is denoted as 2t, and the application time interval between the third radio - frequency pulse and the fourth radio - frequency pulse is denoted as 2t.

[0055] It can be understood that in some scenarios, the flip angle of the first radio - frequency pulse in the first multi - echo spin - echo sequence can be set to 90°, and the flip angles after the first radio - frequency pulse can be set to 180°, as shown in Figure 1 and Figure 2 shown.

[0056] Step S302: Adjust the first multi - echo spin - echo sequence to obtain the second multi - echo spin - echo sequence.

[0057] Step S303: Use the second multi - echo spin - echo sequence for scanning to perform transverse relaxation time constant quantitative imaging.

[0058] Among them, the above - mentioned adjustment includes: adjusting the magnitude of at least one of the pre - dispersion gradient and the read - out gradient in the first multi - echo spin - echo sequence so that the magnitude of the pre - dispersion gradient is not equal to half of the magnitude of the read - out gradient; the adjustment also includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio - frequency pulse in the first multi - echo spin - echo sequence.

[0059] Among them, the pre - dispersion gradient is the gradient that pre - disperses the FID signal before the FID signal generated by the first radio - frequency pulse forms a spin - echo signal once. The application direction of the pre - dispersion gradient can be the slice - selection gradient direction (corresponding to Figure 1 G SS ), the phase - encoding direction (corresponding to Figure 1 G PE ) or the read - out direction (corresponding toFigure 1 of G RO ). The number of the pre-dispersed phase gradients can be single or multiple. When the number of the pre-dispersed phase gradients is single, the application time of the pre-dispersed phase gradient can be before or after the second radio frequency pulse. When it is before the second radio frequency pulse, the direction of the pre-dispersed phase gradient is the same as that of the readout gradient. When it is after the second radio frequency pulse, the direction of the pre-dispersed phase gradient is opposite to that of the readout gradient. When the number of the pre-dispersed phase gradients is multiple, the application time of some pre-dispersed phase gradients can be before the second radio frequency pulse, and some pre-dispersed phase gradients can be after the second radio frequency pulse. Similarly, the pre-dispersed phase gradients before the second radio frequency pulse have the same direction as the readout gradient, and the pre-dispersed phase gradients after the second radio frequency pulse have the opposite direction to the readout gradient.

[0060] In the first multi-echo spin echo sequence, starting from the second radio frequency pulse, there is a corresponding readout gradient after each subsequent radio frequency pulse, and the magnitudes of the readout gradients can be kept consistent.

[0061] Specifically, the magnitude of the pre-dispersed phase gradient or the readout gradient can be adjusted in the first multi-echo spin echo sequence to meet the following requirement: the magnitude of the pre-dispersed phase gradient is not equal to half of the magnitude of the readout gradient.

[0062] Compared with Figure 1 the example shown, Figure 4 the example shown adjusts the magnitude of the pre-dispersed phase gradient. In this example, the pre-dispersed phase gradient is greater than half of the readout gradient, the number of the pre-dispersed phase gradients is single, the pre-dispersed phase gradient is positive, and it is applied before the second radio frequency pulse. Since the pre-dispersed phase gradient is greater than half of the readout gradient, after scanning using the Figure 4 sequence shown, it can be made that: (1) the formation time of the primary spin echo signal is delayed, later than the central time of the readout gradient, and the interval from the formation time of the primary spin echo signal to the application time of the third radio frequency pulse becomes shorter; (2) the formation time of the secondary spin echo signal is advanced, earlier than the central time of the readout gradient; (3) the formation time of the first stimulated echo is delayed, later than the central time of the readout gradient; (4) the formation time of the tertiary spin echo signal is delayed, later than the central time of the readout gradient; (5) the formation time of the second stimulated echo is advanced, earlier than the central time of the readout gradient. Thus, the secondary spin echo signal and the first stimulated echo signal can be separated, and the tertiary spin echo signal and the second stimulated echo signal can be separated.

[0063] In Figure 4In the illustrated example, although the triple spin echo signal is separated from the second stimulated echo signal formed under the action of the second, third, and fourth radio frequency pulses, it is mixed with the stimulated echo signals formed under the action of the first, second, and fourth radio frequency pulses. Therefore, when performing T2 quantitative imaging, the T2 quantitative result will still be affected.

[0064] Based on this, the present application further adjusts on the basis of the above adjustment. The adjustment includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin echo sequence. The application direction of this pair of gradients can be the slice selection gradient direction (corresponding to Figure 1 's G SS ), the phase encoding direction (corresponding to Figure 1 's G PE ), or the readout direction (corresponding to Figure 1 's G RO ). Among this pair of gradients, the gradient applied before the second radio frequency pulse is called the first gradient, and the gradient applied after the second radio frequency pulse is called the second gradient.

[0065] After applying the first gradient, (1) Figure 4 the first stimulated echo signal shown will not be formed within the readout gradient after the third radio frequency pulse under the action of the first gradient. Therefore, there is only a double spin echo signal within the readout gradient after the third radio frequency pulse, as shown in Figure 5 ; in addition, after applying the first gradient, (2) it can make the stimulated echo signals formed under the action of the first, second, and fourth radio frequency pulses not be formed at the triple spin echo signal. Therefore, the triple spin echo signal will not be mixed with this stimulated echo signal; after applying the first gradient, in order to enable the single spin echo signal to be formed within the readout gradient, the above-mentioned second gradient can be applied.

[0066] Thus, a single spin echo signal, a double spin echo signal, and a triple spin echo signal that are not mixed with stimulated echo signals can be collected. Based on these three spin echo signals, images with different contrasts are formed, and T2 quantification is performed.

[0067] In the above-mentioned transverse relaxation time constant quantitative imaging method, after obtaining the first multi-echo spin echo sequence, the first multi-echo spin echo sequence is adjusted to obtain a second multi-echo spin echo sequence; the second multi-echo spin echo sequence is used for scanning to perform transverse relaxation time constant quantitative imaging; the adjustment of the first multi-echo spin echo sequence in this application includes: adjusting the magnitude of at least one of the pre-dephasing gradient and the readout gradient in the first multi-echo spin echo sequence so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient, and adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse in the first multi-echo spin echo sequence, whereby a plurality of spin echo signals without mixed stimulated echo signals can be obtained, and thus a T2 quantitative image not affected by the stimulated echo signal can be obtained, improving the accuracy of the T2 quantitative result.

[0068] Referring to Figure 6 , compared with Figure 5 In terms of Figure 6 In the example shown, the pre-dephasing gradient is less than half of the magnitude of the readout gradient. After scanning using the sequence shown in Figure 6 , it can be made that: (1) the formation time of the primary spin echo signal is advanced, earlier than the center time of the readout gradient, and the interval from the formation time of the primary spin echo signal to the application time of the third radio frequency pulse becomes longer; (2) the formation time of the secondary spin echo signal is delayed, later than the center time of the readout gradient; (3) the first stimulated echo will not be formed within the readout gradient after the third radio frequency pulse; (4) the formation time of the tertiary spin echo signal is advanced, earlier than the center time of the readout gradient; (5) the formation time of the second stimulated echo is delayed, later than the center time of the readout gradient; (6) the formation time of the third stimulated echo signal is advanced, earlier than the center time of the readout gradient.

[0069] In one embodiment, the method provided in this application further includes: adjusting the magnitude of the pre-dephasing gradient so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient.

[0070] In this embodiment, only the magnitude of the pre-dephasing gradient can be adjusted so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient, without adjusting the magnitude of the readout gradient, improving the processing efficiency.

[0071] Further, the adjusting the magnitude of the pre-dephasing gradient so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient includes: taking half of the magnitude of the readout gradient as the adjustment standard value; determining the magnitude of the pre-dephasing gradient within a range less than the adjustment standard value or within a range greater than the adjustment standard value.

[0072] In one embodiment, after adjustment, the number of the pre-spread phase gradients is single or two.

[0073] This application does not limit the number of the pre-spread phase gradients before adjustment, and those skilled in the art can set it according to actual needs.

[0074] After adjustment, the number of the pre-spread phase gradients can be single or two.

[0075] Further, when the number of the pre-spread phase gradients is single after adjustment: after adjustment, the application time of the pre-spread phase gradient is before the second radio frequency pulse, as Figure 5 shown; or, after adjustment, the application time of the pre-spread phase gradient is after the second radio frequency pulse, as Figure 7 shown.

[0076] Further, when the number of the pre-spread phase gradients is two after adjustment: after adjustment, the application time of one of the two pre-spread phase gradients is before the second radio frequency pulse, and the application time of the other pre-spread phase gradient of the two pre-spread phase gradients is after the second radio frequency pulse, as Figure 8 shown.

[0077] In one embodiment, the adjustment further includes: after the application time of the third readout gradient of the first multi-echo spin echo sequence, adding spoiling gradients in the slice selection gradient direction, the phase encoding direction, and the readout gradient direction.

[0078] Refer to Figure 5 , in the first multi-echo spin echo sequence, since there is no readout gradient after the first radio frequency pulse, the readout gradient after the fourth radio frequency pulse belongs to the third readout gradient in the application time sequence.

[0079] After adjusting the magnitude of at least one of the pre-spread phase gradient and the readout gradient in the first multi-echo spin echo sequence so that the magnitude of the pre-spread phase gradient is not equal to half of the magnitude of the readout gradient, and after adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse in the first multi-echo spin echo sequence, the first 3 spin echo signals (i.e., the first spin echo signal, the second spin echo signal, and the third spin echo signal) are not mixed with stimulated echo signals, and the subsequent spin echo signals are mixed with stimulated echo signals. Therefore, in this embodiment, after the application time of the third readout gradient, spoiling gradients are added in the slice selection gradient direction (corresponding to G SS ), the phase encoding direction (corresponding to G PE ), and the readout gradient direction (corresponding to G RO ) to avoid unnecessary signal residues.

[0080] It should be understood that although the steps in the flowcharts involved in the various embodiments described above are sequentially shown according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the various embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0081] In one embodiment, as Figure 9 shown, a magnetic resonance imaging device is provided, including:

[0082] A sequence acquisition module 901, configured to acquire a first multi-echo spin echo sequence;

[0083] A sequence adjustment module 902, configured to adjust the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence;

[0084] A quantitative imaging module 903, configured to perform transverse relaxation time constant quantitative imaging by scanning using the second multi-echo spin echo sequence;

[0085] Wherein, the adjustment includes: adjusting the magnitude of at least one of the pre-dephasing gradient and the readout gradient of the first multi-echo spin echo sequence so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient; the adjustment further includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin echo sequence.

[0086] In one embodiment, the device further includes an adjustment module, configured to: adjust the magnitude of the pre-dephasing gradient so that the magnitude of the pre-dephasing gradient is not equal to half of the magnitude of the readout gradient.

[0087] In one embodiment, the adjustment module is further configured to: use half of the magnitude of the readout gradient as an adjustment standard value; determine the magnitude of the pre-dephasing gradient within a range less than the adjustment standard value or within a range greater than the adjustment standard value.

[0088] In one embodiment, after adjustment, the number of the pre-dephasing gradients is single or two.

[0089] In one embodiment, when the number of the pre-dephasing gradients is single after adjustment:

[0090] After adjustment, the application time of the pre-dispersion phase gradient is before the second radio frequency pulse;

[0091] Or, after adjustment, the application time of the pre-dispersion phase gradient is after the second radio frequency pulse.

[0092] In one embodiment, after adjustment, when the number of the pre-dispersion phase gradients is two:

[0093] After adjustment, the application time of one of the two pre-dispersion phase gradients is before the second radio frequency pulse, and the application time of the other pre-dispersion phase gradient of the two pre-dispersion phase gradients is after the second radio frequency pulse.

[0094] In one embodiment, the adjustment further includes: after the application time of the third readout gradient of the first multi-echo spin echo sequence, spoiling gradients are added in the slice selection gradient direction, the phase encoding direction, and the readout gradient direction.

[0095] For the specific limitations of the magnetic resonance imaging device, reference can be made to the limitations on the transverse relaxation time constant quantitative imaging method in the above text, which will not be elaborated here. Each module in the above magnetic resonance imaging device can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in the processor in the magnetic resonance imaging system in hardware form or independent of it, or stored in the memory in the magnetic resonance imaging system in software form, so that the processor can call and execute the operations corresponding to the above modules.

[0096] In one embodiment, a magnetic resonance imaging system is provided. The magnetic resonance imaging system includes a processing device, and its internal structure diagram can be as Figure 10 shown. The processing device includes a processor, a memory, and a network interface connected through a system bus. Among them, the processor of the processing device is used to provide computing and control capabilities. The memory of the processing device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the processing device is used to store transverse relaxation time constant quantitative imaging data. The network interface of the processing device is used to communicate with an external terminal through a network connection. The processing device further includes an input / output interface. The input / output interface is a connection circuit for exchanging information between the processor and external devices, and they are connected to the processor through a bus, abbreviated as the I / O interface. When the computer program is executed by the processor, a transverse relaxation time constant quantitative imaging method is implemented.

[0097] Those skilled in the art can understand, Figure 10The structure shown is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the processing device to which the solution of this application is applied. The specific processing device may include more or fewer components than those shown in the figure, or combine some components, or have a different component arrangement.

[0098] In one embodiment, a magnetic resonance imaging system is provided, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps in the above-mentioned method embodiments are implemented.

[0099] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0100] In one embodiment, a computer program product is provided, on which a computer program is stored, and the computer program is executed by a processor to implement the steps in the above-mentioned method embodiments.

[0101] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned method embodiments can be completed by instructing relevant hardware through a computer program. The above-mentioned computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned method embodiments. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0102] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The above embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for quantitatively imaging transverse relaxation time constant, characterized in that, The method includes: Obtaining a first multi-echo spin echo sequence; Adjusting the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence; Scanning using the second multi-echo spin echo sequence for transverse relaxation time constant quantitative imaging; Wherein, the adjustment includes: adjusting the magnitude of at least one of the prephasing gradient and the readout gradient of the first multi-echo spin echo sequence so that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient; the adjustment further includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin echo sequence.

2. The method according to claim 1, characterized in that, The method further includes: Adjusting the magnitude of the prephasing gradient so that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient.

3. The method according to claim 2, characterized in that, The adjusting the magnitude of the prephasing gradient so that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient includes: Taking half of the magnitude of the readout gradient as the adjustment standard value; Determining the magnitude of the prephasing gradient within a range less than the adjustment standard value or within a range greater than the adjustment standard value.

4. The method according to any one of claims 1 to 3, characterized in that After adjustment, the number of prephasing gradients is single or two.

5. The method according to claim 4, wherein In the case where the number of prephasing gradients is single after adjustment: After adjustment, the application time of the prephasing gradient is before the second radio frequency pulse; Or, after adjustment, the application time of the prephasing gradient is after the second radio frequency pulse.

6. The method according to claim 4, characterized in that, In the case where the number of prephasing gradients is two after adjustment: After adjustment, the application time of one of the two prephasing gradients is before the second radio frequency pulse, and the application time of the other prephasing gradient of the two prephasing gradients is after the second radio frequency pulse.

7. The method according to claim 1, characterized in that, The adjustment further includes: adding spoiling gradients in the slice selection gradient direction, the phase encoding direction, and the readout gradient direction after the application time of the third readout gradient of the first multi-echo spin echo sequence.

8. A magnetic resonance imaging apparatus, characterized in that, The apparatus includes: A sequence acquisition module for obtaining a first multi-echo spin echo sequence; A sequence adjustment module for adjusting the first multi-echo spin echo sequence to obtain a second multi-echo spin echo sequence; A quantitative imaging module for scanning using the second multi-echo spin echo sequence for transverse relaxation time constant quantitative imaging; Wherein, the adjustment includes: adjusting the magnitude of at least one of the prephasing gradient and the readout gradient of the first multi-echo spin echo sequence so that the magnitude of the prephasing gradient is not equal to half of the magnitude of the readout gradient; the adjustment further includes: adding a pair of gradients with the same magnitude and polarity before and after the second radio frequency pulse of the first multi-echo spin echo sequence.

9. A magnetic resonance imaging system, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method according to any one of claims 1 to 7.

Images