CN113317770B - Double-contrast perfusion magnetic resonance imaging method and system - Google Patents
Double-contrast perfusion magnetic resonance imaging method and system Download PDFInfo
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Abstract
The invention belongs to the technical field of magnetic resonance imaging, and discloses a perfusion magnetic resonance imaging method and a perfusion magnetic resonance imaging system with double contrast, wherein a magnetization vector is excited to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse; opening a selected layer gradient, gradually descending to zero after the selected layer gradient reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the emission of the excitation pulse to the opening of the double-echo helical gradient is called a first echo time, the time from the emission of the excitation pulse to the end of the double-echo helical gradient is called a second echo time, and finally, the image signals of the double-echo helical acquisition Dynamic Contrast Enhancement (DCE) and the dynamic magnetic sensitivity enhancement (DSC) are obtained. A dual contrast perfusion magnetic resonance imaging method is completed. The invention is capable of imaging blood flow, blood flow velocity and vessel wall permeability.
Description
Technical Field
The invention belongs to the technical field of magnetic resonance imaging, and particularly relates to a perfusion magnetic resonance imaging method and system with double contrast.
Background
Currently, blood is a tissue that circulates in the heart and blood vessel lumens. The blood can transport oxygen and nutrient substances everywhere for the body by means of the functions of transportation and storage of blood vessels, and can realize the regulation of body temperature, acid-base number and osmotic pressure in the body, thereby playing an important role in the vital activities of the human body. Blood and blood vessel abnormality can trigger and exacerbate the exacerbation of various diseases, and blood vessel normalization is one of the research hotspots in the field of regenerative medicine.
Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) are two noninvasive perfusion imaging technologies widely applied to detection of vascular permeability and blood flow, and can realize the effects of early diagnosis, grading, prognosis evaluation of treatment and the like of diseases through qualitative and quantitative indexes. However, conventional DCE-MRI is implemented with FLASH, with higher spatial resolution but lower temporal resolution. The traditional DSC-MRI adopts GRE-EPI with single emission, and has high time resolution and low spatial resolution. However, the two perfusion imaging methods can help us to obtain completely different parameters for blood and blood vessels, and play a vital role corresponding to different clinical application values. Both imaging modalities require the use of contrast agents, but gadolinium contrast agents are not only potentially nephrotoxic, but there is increasing evidence that gadolinium deposition in the brain may occur after repeated exposure. If two perfusion imaging data are acquired for a patient, two injections of magnetic resonance contrast agent are required, which greatly brings about the occurrence of side effects of the kidney and brain, and the two imaging times are long, which may be intolerable for the patient. If a perfusion imaging method and an experimental device with higher time and spatial resolution can be established, the reduction of the dosage of gadolinium contrast agent can be realized at the same time, and the research on vascular normalization can be greatly promoted.
Through the above analysis, the problems and defects existing in the prior art are as follows:
(1) Traditional DCE-MRI is implemented with FLASH, but with lower temporal resolution.
(2) Conventional DSC-MRI uses single shot GRE-EPI, but with low spatial resolution.
(3) Both traditional DCE-MRI and DSC-MRI require the use of contrast agents, but gadolinium contrast agents are potentially nephrotoxic and there is increasing evidence that gadolinium deposition in the brain may occur after repeated exposure. If two perfusion imaging data are acquired for a patient, two injections of magnetic resonance contrast agent are required, which greatly brings about the occurrence of side effects of the kidney and brain
(4) Completing DCE-MRI and DSC-MRI, imaging times are too long and may be intolerable to patients.
The difficulty of solving the problems and the defects is as follows:
the first difficulty is the technical innovation level: the traditional Cartesian acquisition is abandoned, k-space data is acquired by using a spiral, and the whole k-space can be filled by only acquiring one piece of k-space data, so that the device is different from the traditional Cartesian acquisition, and needs a plurality of acquisitions, so that the acquisition efficiency is greatly improved. Secondly, the spiral acquisition can not acquire data around the edge, and the spiral acquisition is helpful for improving the acquisition efficiency. Helping us to improve temporal resolution. Third, since the spiral trajectory does not use a phase encoding gradient, the spiral trajectory from the center of k-space may have a short echo time to improve T1 contrast. Conversely, starting from the k-space edge, rotating inwards, a longer echo time can be obtained to increase the sensitivity of T2. Facilitating dual contrast perfusion imaging. Fourth, they are generally less sensitive to motion due to the greater sampling density near the center of k-space. Helping us reduce our motion artifacts. The dual-echo spiral acquisition and two perfusion imaging are combined, the first echo completes Dynamic Contrast Enhancement (DCE), and the second echo completes dynamic magnetic sensitivity enhancement (DSC), so that imaging time is greatly shortened.
The invention completes the development of the sequence, the test of the water model, the test of the experimental animal and the post-treatment of the data, and finally realizes the establishment of the double-echo spiral acquisition sequence from nothing to nothing. In the development process of the sequence, a spherical water model is used for testing, and the optimal parameters and the optimal waveforms are adjusted, so that the difficulty is that the adjustment of the optimal parameters requires testing each of a large number of parameters, and meanwhile, the optimization of one parameter is likely to influence the selected optimal parameters. Under the condition of relatively optimal parameters, the optimal parameters and indexes are selected and selected, and the optimal conditions of all the parameters cannot be realized.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a perfusion magnetic resonance imaging method and a perfusion magnetic resonance imaging system with double contrast.
The invention is realized in that a dual contrast perfusion magnetic resonance imaging method comprises the following steps:
exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse; wherein the plane is an XY plane;
step two, adopting a system to allow the maximum gradient climbing speed to open the layer-selecting gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping;
step three, opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform;
step four, the time from the emission of the excitation pulse to the opening of the double-echo spiral gradient is called a first echo time;
fifthly, when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
and step six, obtaining image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted echo time.
Further, in the second step, the acquiring of the magnetic resonance imaging sequence includes:
opening the layer selection gradient, selecting a layer selection gradient with a turning angle of 10-90 degrees, applying the layer selection gradient in the-y axis direction, and applying the initial magnetization vector M 0 Is expressed as M by the formula of the total excitation to the transverse plane +x axis xy ＝M 0 * sin theta, where M xy Is the magnetization vector of the transverse plane, M 0 An initial magnetization vector, theta is the turning angle of the layer-selecting gradient; the maximum allowable pulse magnetic field strength of the system is B m The gyromagnetic ratio of hydrogen protons is gamma, and after the flip angle theta is selected, the pulse width P=theta/gamma B is calculated by the formula m The pulse energy, and thus the minimum time required to transmit this pulse, can be known; the excitation vector initial transverse plane components all have a phase difference along the +x axisG z For the selected layer gradient, Δz is the selected layer thickness, Δt 1 For the duration of the layer gradient after layer selection excitation, the signals within the layer are superimposed as follows: />Therefore, after the excitation of the selected layer is completed, the phase of the magnetization vector is refocused by using an in-layer wrapping gradient opposite to the gradient of the selected layer, and the signal formula in the layer is as follows: m ≡ xy dz＝∫M 0 sinθdz。
Further, in the second step, the duration of the gradient wrap-around is smaller than the duration of the layer-selecting pulse.
In the third step, the double-echo spiral gradient waveform is obtained from the designed K space track.
In the fifth step, the K-space trajectory is determined by the set field of view, resolution, bandwidth, sampling time interval, sampling density and maximum gradient climbing speed that can be achieved by the hardware facility.
Further, in step six, the step of obtaining the image signals of dual-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted echo time includes:
the first echo time is adjusted, a dynamic contrast enhancement image corresponding to the first echo time is obtained, the second echo time is adjusted, and a dynamic magnetic sensitivity enhancement image corresponding to the second echo time is obtained; wherein the first echo time is less than the second echo time.
Another object of the present invention is to provide a dual contrast perfusion magnetic resonance imaging method, comprising:
the excitation module is used for exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, and the plane is an XY plane;
the control acquisition module is used for adopting a system to allow the maximum gradient climbing speed to open the layer-selecting gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
and the processing module is used for obtaining image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted echo time.
It is a further object of the present invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:
exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse; meanwhile, a system is adopted to allow the maximum gradient climbing speed to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time; finally, the first echo time and the second echo time are adjusted, and image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) are obtained based on the adjusted echo time.
Another object of the present invention is to provide a computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:
exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse; meanwhile, a system is adopted to allow the maximum gradient climbing speed to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time; finally, the first echo time and the second echo time are adjusted, and image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) are obtained based on the adjusted echo time.
Another object of the present invention is to provide an information data processing terminal for implementing the dynamic contrast enhanced magnetic resonance imaging system.
By combining all the technical schemes, the invention has the advantages and positive effects that: according to the imaging method and system for simultaneous spiral acquisition of Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) of double echoes, under the condition of injecting a contrast agent once, encoding and reading are carried out by using a layer selection gradient and a double-echo spiral gradient, and a double-echo image is obtained through one-time scanning, so that a double-echo Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) magnetic resonance imaging signal and image with higher time and spatial resolution are obtained. Meanwhile, the invention is mainly applied to imaging of blood flow, blood flow velocity and vascular permeability, and can image the blood flow, the blood flow velocity and vascular wall permeability.
The following problems exist with current perfusion imaging, first: the imaging spatial resolution is low (3 mm x 5 mm), which results in poor quality of images and difficult identification of tiny lesions. Second,: the time resolution is low (3-6 s), because the perfusion imaging is to realize the real-time dynamic rapid monitoring and scanning of the contrast agent after the contrast agent is injected, the low time resolution also causes the problem that the imaging is insensitive to the dynamic imaging and the monitoring is inaccurate. Third,: the imaging time is long (5 min) and is difficult for the patient to tolerate. Fourth,: contrast agents are needed in perfusion imaging modes, but the problems of potential side effects and harm to kidneys and brain exist in the contrast agents.
The invention discards the traditional Cartesian acquisition, and adopts the spiral acquisition of k-space data, and as we acquire only one piece of k-space data, the whole k-space can be filled, which is different from the traditional Cartesian acquisition, and needs a plurality of acquisitions, thus greatly improving the acquisition efficiency. Secondly, the spiral acquisition can not acquire data around the edge, and the spiral acquisition is helpful for improving the acquisition efficiency. Helping us to improve temporal resolution. Third, since the spiral trajectory does not use a phase encoding gradient, the spiral trajectory from the center of k-space may have a short echo time. Conversely, starting from the k-space edge, rotating inwards, a longer echo time can be obtained to increase the sensitivity of T2. Fourth, they are generally less sensitive to motion due to the greater sampling density near the center of k-space. Helping us reduce our motion artifacts
Based on the advantages of the spiral acquisition, the double-echo spiral acquisition is changed, and the two echoes can be used for respectively carrying out dynamic contrast enhancement and dynamic magnetic sensitivity enhancement imaging while the advantages of the spiral acquisition are combined. The perfusion image with double contrast is obtained by one-time acquisition.
The meaning of solving the problems and the defects is as follows: through the optimization, parameters of perfusion imaging, such as spatial resolution can be 1mm by 5mm, temporal resolution can be 0.52s, and as double-contrast images can be obtained through one injection, the consumption of contrast agent can be reduced, and the imaging time is shortened by half. By utilizing the new sequence which is independently developed, imaging with high spatial and time resolution can be realized, accurate diagnosis of focus and early detection of diseases are facilitated, and a series of parameters of blood, interstitial and blood vessels are obtained under the noninvasive condition.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Figure 1 is a flow chart of a dynamic contrast enhanced magnetic resonance imaging method provided by an embodiment of the present invention.
Fig. 2 is a schematic diagram of a magnetic resonance imaging sequence according to an embodiment of the present invention.
FIG. 3 is a block diagram of a dual echo helical acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) imaging system provided by an embodiment of the present invention.
Fig. 4 is a block diagram of an electronic device according to an embodiment of the present invention.
Fig. 5 is a view of a beagle head image obtained from a first echo provided by an embodiment of the present invention:
fig. 6 is a view of a second echo acquisition beagle head image provided by an embodiment of the present invention:
fig. 7 is a graph showing a time-dependent change of the first echo signal and the second echo signal according to an embodiment of the present invention:
fig. 8 is a plot of Δr and Δr relaxation time versus time provided by an embodiment of the present invention:
FIG. 9 is a graph of Dynamic Contrast Enhanced (DCE) transport rate constant (Ktrans) provided by an embodiment of the present invention:
FIG. 10 is a graph of Dynamic Contrast Enhancement (DCE) partial plasma volume (vp) provided by an embodiment of the present invention:
FIG. 11 is a dynamic magnetically sensitive contrast enhanced (DSC) blood flow chart provided by an embodiment of the present invention:
FIG. 12 is a graph of dynamic magnetic sensitivity contrast enhanced (DSC) blood flow provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In view of the problems, the present invention provides a dual contrast perfusion magnetic resonance imaging method and system, and the present invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the perfusion magnetic resonance imaging method with dual contrast provided by the embodiment of the invention comprises the following steps:
s101, exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse; wherein the plane is an XY plane; the small angle here is typically 10-90;
s102, adopting a system to allow the maximum gradient climbing rate to open the layer-selecting gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; the maximum gradient climbing rate allowed by the system is used for shortening the time required by imaging and exerting the advantage of the sequence to the greatest extent;
s103, opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the preset double-echo spiral gradient waveform change can be adjusted according to an imaging object and imaging equipment;
s104, the time from the emission of the excitation pulse to the opening of the double-echo spiral gradient is called a first echo time (TE 1); the first echo time we use is typically less than 4ms;
s105, when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time (TE 2); the second echo time we use is typically less than 34.2ms;
s106, obtaining image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted echo time. The dual contrast perfusion imaging method is completed.
The technical scheme of the invention is further described below by combining the embodiments.
The method has higher spatial resolution but lower time resolution for DCE-MRI in the prior art. DSC-MRI has high time resolution and low spatial resolution. Moreover, both imaging modalities require the use of contrast agents, gadolinium contrast agents not only have potential renal toxicity, but also have more and more evidence that problems with gadolinium deposition in the brain may occur after repeated exposure.
The embodiment of the invention provides a double-contrast double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) imaging method and system, which are mainly applied to imaging of blood flow, blood flow velocity and vascular permeability and can image the blood flow, the blood flow velocity and vascular wall permeability. Exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, wherein the angle is 60 degrees, the plane is an XY plane, a system is adopted to allow a maximum gradient climbing speed to open a selected layer gradient, the maximum gradient climbing speed of the system in which the experiment is positioned is 110mT/m/ms, and the maximum gradient climbing speed is used for exerting the advantage of the system to the greatest extent and shortening the imaging time; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero, and changes according to the preset double-echo spiral gradient waveform, and the preset double-echo spiral gradient waveform in the experiment is the optimal waveform suitable for the experiment after the test; the time from the emission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time, and the first echo time used in the experiment is controlled within 4ms; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time, and the second echo time used in the experiment is controlled within 34.2ms; and obtaining imaging methods and system magnetic resonance imaging image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time. In an imaging part required by a human body, a dynamic contrast enhancement image is obtained in a first echo image; in the second echo image, a dynamic magnetic sensitivity enhanced image is obtained. Thus, the dual contrast perfusion imaging method is completed.
FIG. 1 is a flow chart of a dual-echo helical acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) imaging method provided by an embodiment of the present invention, as shown in FIG. 1, comprising:
s1, exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, wherein the plane is an XY plane;
s2, adopting a system to allow the maximum gradient climbing speed to open the layer-selecting gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
s3, obtaining an imaging method and a system magnetic resonance imaging image signal of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time.
Specifically, in step S1, a layer selection gradient is used in combination with radio frequency pulse layer selection excitation to excite a magnetization vector in a specific layer to a transverse plane, wherein the transverse plane is an XY plane, and the magnitude of the magnetization vector excited to the transverse plane is related to the flip angle of the radio frequency pulse, and is expressed as M by a formula xy ＝M 0 * sin theta, where M xy Is the magnetization vector of the transverse plane, M 0 The initial magnetization vector, θ is the flip angle of the radio frequency pulse, the initial excitation vector keeps the same phase, but the layer selection gradient adopted during layer selection excitation can lead to the magnetization vector phase dispersion of different positions in the layer direction, and the in-layer wrapping is adopted to gather the magnetization vectors in the layer back to the same phase.
In the step S2, a system is adopted to allow the maximum gradient climbing speed to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
in step S3, the first echo and the second echo time are further adjusted, and based on the adjusted echo time, image signals of dual-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) are obtained.
The present example obtains dual echo images by one scan with one injection of contrast agent by exciting magnetization vectors into the transverse plane of magnetic field space, encoding and readout using slice-selective gradients and dual echo helical gradients, resulting in dual echo Dynamic Contrast Enhanced (DCE) and dynamic magnetic sensitivity enhanced (DSC) magnetic resonance imaging signals and images of higher temporal and spatial resolution.
Based on the above example, the obtaining the dual-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) image signals by adjusting the first echo time and the second echo time specifically includes:
adjusting the first echo time and the second echo time, and acquiring a Dynamic Contrast Enhancement (DCE) image corresponding to the first echo imaging time and a dynamic magnetic sensitivity enhancement (DSC) image corresponding to the second echo imaging time, wherein the first echo imaging time is smaller than the second echo imaging time;
here, in the imaging part required by the human body, a dynamic contrast enhancement image is obtained in the first echo image; in the second echo image, a dynamic magnetic sensitivity enhanced image is obtained.
According to the embodiment of the invention, imaging images under TE1 time and TE2 time are respectively obtained by adjusting the length of the first echo time and the second echo time, and dual-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) imaging signals with higher time-space resolution are obtained.
Based on any of the above examples, the flip angle of the selected layer gradient is 10-90 degrees, and the amplitude of the selected layer gradient selects the maximum value allowed by the system.
Specifically, in the case where the magnitude value of the selected layer gradient is constant, the magnitude of the energy of the magnetization vector of the transverse plane is related to the flip angle θ of the non-selected layer gradient, and different imaging substances require magnetization vectors of different energies, so that different imaging substances can be observed by adjusting the flip angle of the non-selected layer gradient to a certain value of 10 to 90 degrees; also, the pulse amplitude selection system hardware of the slice gradient allows for a maximum value such that the slice gradient width is minimized.
The double-echo spiral gradient waveform is obtained from a designed K space track.
The K space track is determined by the set visual field, resolution, bandwidth, sampling time interval, sampling density, maximum gradient achieved by hardware facilities and maximum gradient climbing speed.
FIG. 2 is a schematic diagram of a magnetic resonance imaging sequence provided by the embodiment of the present invention, in which, as shown in FIG. 2, a layer selection gradient is opened, a layer selection gradient with a flip angle θ=10-90 degrees is selected and applied in the-y-axis direction, and an initial magnetization vector M is applied 0 Is expressed as M by the formula of the total excitation to the transverse plane +x axis xy ＝M 0 * sin theta, where M xy Is the magnetization vector of the transverse plane, M 0 The initial magnetization vector, θ, is the flip angle of the selected layer gradient. The maximum allowable pulse magnetic field strength of the system is B m The gyromagnetic ratio of hydrogen protons is gamma, and after the flip angle theta is selected, the pulse width P=theta/gamma B is calculated by the formula m The pulse energy, and thus the minimum time required to transmit this pulse, can be known. The excitation vector initial transverse plane components all have a phase difference along the +x axisG z For the selected layer gradient, Δz is the selected layer thickness, Δt 1 For the duration of the layer gradient after layer selection excitation, the signals within the layer are superimposed as follows:thus, after the excitation of the selected layer is completed, the phase of the magnetization vector will be refocused immediately by an in-layer wrapping gradient that reverses direction opposite to the gradient of the selected layer, the signal in the layer being formulated as: m ≡ xy dz＝∫M 0 sinθdz。
In order to achieve the shortest echo time, after the magnetization vector is excited, the system is adopted to allow the maximum gradient climbing rate to turn on the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the emission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time, denoted TE1; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time and is marked as TE2; after the dual echo spiral readout gradient becomes zero, acquiring a signal; the first echo time te1=4 ms and the second echo time te1=34.2 ms are set in the experiment.
In the technology, the first echo time and the second echo time are adjusted, and image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) are obtained based on the adjusted echo time.
Fig. 3 is a structural diagram of a dual-echo helical acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) imaging magnetic resonance imaging system according to an embodiment of the present invention, as shown in fig. 3, including: an excitation module 31, a control acquisition module 32 and a processing module 33; wherein:
the excitation module 31 is used for exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, wherein the plane is an XY plane;
the control acquisition module 32 is used for adopting the system to allow the maximum gradient climbing rate to turn on the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
the processing module 33 is configured to obtain an imaging method and a system magnetic resonance imaging image signal of dual-echo helical acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time.
The system provided by the embodiment of the present invention is used for executing the corresponding method, and the specific implementation manner is consistent with the implementation manner of the method, and the related algorithm flow is the same as the algorithm flow of the corresponding method, and is not repeated here.
The present example obtains dual echo images by one scan with one injection of contrast agent by exciting magnetization vectors into the transverse plane of magnetic field space, encoding and readout using slice-selective gradients and dual echo helical gradients, resulting in dual echo Dynamic Contrast Enhanced (DCE) and dynamic magnetic sensitivity enhanced (DSC) magnetic resonance imaging signals and images of higher temporal and spatial resolution.
Based on any of the above examples, the processing module 33 includes an adjustment sub-module 331, an acquisition sub-module 332, and a processing sub-module 333; wherein:
the adjusting sub-module 331 is configured to adjust the first echo time and the second echo time twice, where the first echo time is less than the second echo time; the acquiring submodule 332 is configured to acquire an image corresponding to the first echo time and an image corresponding to the second echo time; the processing sub-module 333 is configured to obtain a dual-echo Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) magnetic resonance imaging signal and image with high time and spatial resolution from the image corresponding to the first echo time and the image corresponding to the second echo time.
The imaging images under the first echo time and the second echo time are respectively obtained by adjusting the lengths of the first echo time and the second echo time, and double echo (DCE) and (DSC) magnetic resonance imaging signals with high time and spatial resolution are obtained.
Based on any of the above examples, the flip angle of the selected layer gradient in the excitation module 31 is 10-90 degrees, and the amplitude of the selected layer gradient selects the maximum value allowed by the system.
The double-echo spiral gradient waveform is obtained from a designed K space track.
The K space track is determined by the set visual field, resolution, bandwidth, sampling time interval, sampling density, maximum gradient achieved by hardware facilities and maximum gradient climbing speed.
The embodiment of the invention adjusts the position of the double-echo spiral reaching k space according to the requirement, so as to meet the research requirement and ensure the image with certain definition.
Fig. 4 illustrates a physical schematic diagram of an electronic device, as shown in fig. 4, which may include: processor 410, communication interface (Communications Interface) 420, memory 430 and communication bus 440, wherein processor 410, communication interface 420 and memory 430 communicate with each other via communication bus 440. The processor 410 may call logic instructions in the memory 430 to perform the following method:
exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, wherein the plane is an XY plane; adopting a system to allow the maximum gradient climbing rate to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time; and obtaining imaging methods and system magnetic resonance imaging image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time.
Further, the logic instructions in the memory 430 described above may be implemented in the form of software functional units and may be stored in a computer-readable storage medium when sold or used as a stand-alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In another aspect, embodiments of the present invention further provide a non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor is implemented to perform the transmission method provided in the above embodiments, for example, including: exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, wherein the plane is an XY plane; adopting a system to allow the maximum gradient climbing rate to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time; and obtaining imaging methods and system magnetic resonance imaging image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time.
5 healthy beagle dogs were given 25% mannitol intravenously (injection dose: 25 ml/kg) for the purpose of: the blood brain barrier is opened so that contrast agent can enter the brain and a magnetic resonance perfusion imaging analysis is performed. The test parameters are thatImage field size = 15 x 15cm 2 Matrix size=192×192, layer thickness=5 mm, interval=1.5 mm, first echo time (TE 1) =4 msec, second echo time (TE 2) =34.2 sec, tr=260 msec, layer number=4, number of arms of helical acquisition=16. Flip angle of T1MAP scan = 10 °, 15 °, 20 °, 25 °, 35 °. Perfusion weighted imaging uses flip angle=60, sampling point=90. The magnetic resonance contrast agent gadofoshan injection (injection dose: 0.2 mmol/kg) was injected with a power injector at time 30.
As shown in fig. 5, the first echo obtained a beagle head image:
as shown in fig. 6, the second echo obtained a beagle head image: as shown in fig. 7, the first echo and the second echo signal change curves with time:
as shown in fig. 8, Δr and Δr are relaxation time curves:
as shown in fig. 9, dynamic Contrast Enhanced (DCE) transport rate constant (Ktrans) plot:
as shown in fig. 10, dynamic Contrast Enhanced (DCE) partial plasma volume (vp) plot:
as shown in fig. 11, dynamic magnetic sensitivity contrast enhanced (DSC) blood flow map:
as shown in fig. 12, a dynamic magnetically sensitive contrast enhanced (DSC) blood flow graph.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.
Claims (9)
1. A dual contrast perfusion magnetic resonance imaging method, characterized in that the dual contrast perfusion magnetic resonance imaging method comprises the steps of:
exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse;
adopting a system to allow the maximum gradient climbing rate to open the layer selection gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping;
opening a double-echo spiral to encode and read; the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform;
the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time;
when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
obtaining image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted first echo time and second echo time;
acquisition of a magnetic resonance imaging sequence comprising:
the layer selection gradient is opened, a layer selection gradient with a turning angle of 10-90 degrees is selected and applied to the direction of the-y axis, and all initial magnetization vectors M0 are excited to the transverse plane +x axis and expressed as M by a formula xy ＝M 0 * sin theta, where M xy Is the magnetization vector of the transverse plane, M 0 An initial magnetization vector, theta is the turning angle of the layer-selecting gradient; the maximum pulse magnetic field intensity is allowed to be Bm, the gyromagnetic ratio of hydrogen protons is gamma, and after the flip angle theta is selected, the pulse energy and thus the shortest time required for transmitting the pulse can be obtained by the formula pulse width P=thetaGaBm; the excitation vector initial transverse plane components all have a phase difference along the +x axisGz is the selected layer gradient, Δz is the selected layer thickness, Δt1 is the duration of the selected layer gradient after the selected layer is excited, and then the signals in the layers are superimposed by the following formula: />So that after the excitation of the selected layer is completed,the phase of the magnetization vector is refocused by an in-layer wrapping gradient opposite to the selected layer gradient, and the in-layer signal formula is as follows: m ≡ xy dz＝∫M 0 sinθdz。
2. The dual contrast perfusion magnetic resonance imaging method of claim 1, wherein a duration of the gradient wrap is less than a duration of the slice-select pulse.
3. The dual contrast perfusion magnetic resonance imaging method of claim 1, wherein the dual echo helical gradient waveform is derived from a designed K-space trajectory.
4. A dual contrast perfusion magnetic resonance imaging method as claimed in claim 3, wherein the K-space trajectory is determined by the set field of view, resolution, bandwidth, sampling time interval, sampling density and maximum gradient achievable by hardware facilities and maximum gradient ramp rate.
5. The dual contrast perfusion magnetic resonance imaging method of claim 1, wherein the obtaining image signals of dual echo helical acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted first echo time and second echo time includes:
the first echo time is adjusted, a dynamic contrast enhancement image corresponding to the first echo time is obtained, the second echo time is adjusted, and a dynamic magnetic sensitivity enhancement image corresponding to the second echo time is obtained; wherein the first echo time is less than the second echo time.
6. A dual contrast perfusion magnetic resonance imaging system employing the method of any one of claims 1 to 5, wherein the dual contrast perfusion magnetic resonance imaging system comprises:
the excitation module is used for exciting a magnetization vector to a transverse plane of a magnetic field space by adopting a small-angle excitation pulse, and the transverse plane is an XY plane;
the control acquisition module is used for adopting a system to allow the maximum gradient climbing speed to open the layer-selecting gradient; gradually descending to zero after the gradient of the selected layer reaches the maximum allowable value of the system, and then carrying out gradient wrapping; opening a double-echo spiral to encode and read;
the amplitude of the two-dimensional double-echo spiral gradient waveform starts from zero and changes with a preset double-echo spiral gradient waveform; the time from the transmission of the excitation pulse to the opening of the double-echo helical gradient is called the first echo time; when the double-echo spiral track reaches the maximum K space radius, the double-echo spiral gradient becomes zero, and the time from the transmission of the excitation pulse to the end of the double-echo spiral gradient is called second echo time;
and the processing module is used for obtaining image signals of double-echo spiral acquisition Dynamic Contrast Enhancement (DCE) and dynamic magnetic sensitivity enhancement (DSC) by adjusting the first echo time and the second echo time and based on the adjusted first echo time and second echo time.
7. A computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the dual contrast perfusion magnetic resonance imaging method of any one of claims 1 to 5.
8. A computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the dual contrast perfusion magnetic resonance imaging method of any one of claims 1 to 5.
9. An information data processing terminal for implementing the dual contrast perfusion magnetic resonance imaging method of claim 1.
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