CN113671427B - Magnetic resonance elastography displacement acquisition method and system - Google Patents

Abstract

The invention provides a magnetic resonance elastography displacement acquisition method and system, and relates to the technical field of magnetic resonance imaging. The method includes: step S1: setting an external driver, setting an external triggering drive and frequency, and applying a certain frequency to a detection object The shearing wave generates propagation of the shearing wave in the applied object; Step S2: Motion coding is performed on the shearing wave, and the image information of the displacement of the shearing wave in the detection object changes with time and space is collected. The invention can solve the collection of sampling points of different motion phases of periodic displacement in elastic imaging, and better realize flexible recording and motion coding of periodic displacement.

Description

Magnetic resonance elastography displacement acquisition method and system

technical field

The present invention relates to the technical field of magnetic resonance imaging, in particular, to a method and system for acquiring displacement of magnetic resonance elastography.

Background technique

Magnetic Resonance Imaging (MRI) has become one of the most important clinical diagnostic methods at present due to its excellent soft tissue contrast, multiple functional imaging methods and no radiation damage. Magnetic Resonance Elastography (MRE), as a new type of non-invasive imaging method, uses a special magnetic resonance technique to provide information about tissue elasticity by evaluating the propagation of mechanical waves in the tissue, which can be displayed intuitively. And quantify the elasticity of the internal tissue of the human body, and to image the elasticity of the tissue, making "image palpation" possible, in breast cancer detection, liver cirrhosis staging, atherosclerotic plaque, muscle damage, brain disease detection, radiofrequency ablation, etc. Treatment and monitoring are important.

The invention patent with publication number CN103349551B discloses a magnetic resonance elastography method and system, including: step a: sending a trigger pulse signal through a magnetic resonance imaging device; step b: detecting the frequency of the trigger pulse signal through an external excitation device, and The vibration frequency of the external excitation device is set according to the frequency of the trigger pulse signal, wherein the set vibration frequency of the external excitation device is synchronized with the vibration frequency of the magnetic resonance imaging device; step c: triggering the external excitation device to the object by the magnetic resonance imaging device The measured object outputs the signal and obtains the elastic image of the measured object.

The invention patent with publication number CN102782518B discloses a magnetic resonance elastography, which includes applying mechanical vibration to an object to be examined with a vibration period (T) to generate mechanical waves in the object. A motion-sensitive magnetic resonance acquisition sequence is issued at repetition times TR to acquire magnetic resonance signals from the subject. This acquisition sequence includes applying one or more phase encoding steps within individual repetition times. The repetition time multiplied by the number of phase codes within a repetition time is not equal to an integer multiple of the phase period. Thereby, a magnetic resonance image of the waveform is reconstructed from the magnetic resonance signals collected in the sample space generated by the phase of the mechanical vibration and the phase encoding.

The feature described in the above patent is the current mainstream acquisition method of MRE scanning. The reason why the required TR×phase sampling number≠n×T period is that it is necessary to use this method to obtain the phase offset under the condition of continuous vibration, so as to record the period. sports. If TR x number of phase samples = n x T cycles, the cycle shift cannot be recorded. This kind of displacement coding acquisition method needs to adjust the starting time point of the motion-sensitive gradient, and cooperate with the acquired external periodic motion to generate a motion phase shift. The disadvantage is that the compilation of the acquisition sequence is complicated, and the gradient change of the magnetic resonance imaging equipment is relatively high.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the present invention provides a magnetic resonance elastography displacement acquisition method and system.

According to a magnetic resonance elastography displacement acquisition method and system provided by the present invention, the solution is as follows:

In a first aspect, a magnetic resonance elastography displacement acquisition method is provided, the method comprising:

Step S1: set an external driver, and set an external trigger drive and frequency, apply shear fluctuations of a certain frequency to the detection object, and generate shear fluctuation propagation in the applied object;

Step S2: Motion coding is performed on the shear wave, and image information of the displacement of the shear wave in the detection object changes with time and space is collected.

Preferably, the step S1 includes:

Step S1.1: the operation of the driver is controlled by the vibration controller, and the trigger signal for starting vibration is realized by an external trigger, which can be the trigger set in the magnetic resonance elastography scan sequence, or other external triggers;

Step S1.2: For the acquisition of shear fluctuation displacement at different cycle time points, it is determined by the time point when the drive starts to vibrate after being triggered;

Step S1.3: for the hardware response time delay, the external vibration frequency can be increased by any frequency increment within the range of 0.0001-0.1 Hz.

Preferably, the triggering time point for starting the vibration in the step S1.2 can be any time point in the collected motion cycle, and is determined by the position of the collected motion cycle phase sampling point.

Preferably, the acquisition of magnetic resonance elastography signals in the step S2 includes:

Step S2.1: adding a motion-sensitive gradient MEG to the imaging sequence to encode the motion displacement; the motion-sensitive gradient frequency is consistent or inconsistent with the vibration frequency of the driver;

Step S2.2: for the acquisition of a period of periodic displacement, n phase acquisition points are required, the entire magnetic resonance elastography acquisition includes n consecutive time sequence modules, and each time sequence module acquires a specific motion phase acquisition point;

Step S2.3: If the start time of the motion sensitive gradient MEG is used as the relative time reference point, and the appearance time point of the external trigger point is changed by adding different delay times, the external trigger point will trigger the external driver to generate continuous external vibration, and the external trigger point will The different time points of the trigger point lead to different start times of external vibrations, so that different displacement phase collection points are collected; during the collection process, the product of the repetition time TR and the number of applied motion sensitive gradient MEG steps is an integer of the collection vibration period times.

Preferably, the step S2.1 includes: the loading direction of the motion-sensitive gradient MEG is any one or several of multiple gradient directions, wherein the gradient directions include slice selection, phase encoding and frequency encoding; the imaging sequence is: Any existing imaging sequence.

Preferably, the step S2.2 includes: the imaging sequences in each timing module are basically similar, and the only difference is that the time points when the external trigger points appear are different, and the scanning sequence is set by the magnetic resonance controller to satisfy the requirements in step S1. External trigger signal generation, and control of sweep gradients and RF pulses.

In a second aspect, a magnetic resonance elastography displacement acquisition system is provided, the system comprising:

Module M1: Set the external driver, and set the external trigger drive and frequency, apply shear fluctuation of a certain frequency to the detection object, and generate shear fluctuation propagation in the applied object;

Module M2: Motion coding is performed on the shearing wave, and image information of the displacement of the shearing wave in the detection object changes with time and space is collected.

Preferably, the module M1 includes:

Module M1.1: The work of the driver is controlled by the vibration controller, and the trigger signal to start vibration is realized by an external trigger, which can be the trigger set in the magnetic resonance elastography scan sequence, or other external triggers;

Module M1.2: For the acquisition of shear fluctuation displacement at different cycle time points, it is determined by the time point when the drive starts to vibrate;

Module M1.3: For the hardware response time delay, the external vibration frequency can be increased by any frequency increment within the range of 0.0001-0.1Hz.

Preferably, the triggering time point at which the vibration starts in the module M1.2 can be any time point in the collected motion period, and is determined by the position of the collected motion period phase sampling point.

Preferably, the acquisition of magnetic resonance elastography signals in the module M2 includes:

Module M2.1: The motion-sensitive gradient MEG is added to the imaging sequence to encode the motion displacement; the motion-sensitive gradient frequency is consistent or inconsistent with the vibration frequency of the driver;

Module M2.2: For the acquisition of a period of periodic displacement, n phase acquisition points are required, and the entire magnetic resonance elastography acquisition includes n consecutive time series modules, each time series module collects a specific motion phase acquisition point;

Module M2.3: If the start time of the motion sensitive gradient MEG is used as the relative time reference point, and the appearance time point of the external trigger point is changed by adding different delay times, the external trigger point will trigger the external drive to generate continuous external vibration, and the external The different time points of the trigger point lead to different start times of external vibrations, so that different displacement phase collection points are collected; during the collection process, the product of the repetition time TR and the number of applied motion sensitive gradient MEG steps is an integer of the collection vibration period times.

Compared with the prior art, the present invention has the following beneficial effects:

1. By using the method of changing the vibration start time point of the external driver, the collection of sampling points of different motion phases of the periodic displacement in elastography is solved, and the flexible recording and motion encoding of the periodic displacement are better realized;

2. In the present invention, the periodic change of the motion sensitive gradient of the acquisition sequence does not need to be interrupted, and the sequence has good portability. The acquired motion phase offset is realized by triggering an external driver, and the motion sensitive gradient does not need to cooperate with the external periodic motion for phase offset.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

Fig. 1 is the schematic diagram of the overall scheme of the present invention;

FIG. 2 is a schematic diagram of timing and triggering of displacement acquisition in magnetic resonance elastography.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

Embodiments of the present invention provide a method and system for displacement acquisition of magnetic resonance elastography. Referring to FIG. 1 , first, an external driver is set, and an external trigger drive and frequency are set to apply shear fluctuations of a certain frequency to the detection object, Produces the propagation of shear fluctuations in the applied object.

Specifically, the operation of the driver is controlled by the vibration controller, and the trigger signal for starting vibration is realized by an external trigger, which can be the trigger set in the magnetic resonance elastography scan sequence, or other external triggers.

The acquisition of shear fluctuation displacement at different cycle time points is determined by the time point when the driver starts to vibrate after the trigger. The triggering time point for starting vibration can be any time point in the collected motion cycle, and is determined by the position of the collected motion cycle phase sampling point.

For possible hardware response time delay, the external vibration frequency can be increased by any small frequency increment within the range of 0.0001-0.1Hz to ensure stable and continuous vibration triggering.

Secondly, motion coding is carried out on the shear wave, and the image information of the displacement of the shear wave in the detection object changes with time and space is collected.

Magnetic resonance elastography signal acquisition includes: adding motion-sensitive gradient MEG to the imaging sequence to encode motion displacement; the motion-sensitive gradient frequency and the vibration frequency of the driver can be consistent or inconsistent. The loading direction of the motion-sensitive gradient MEG can be any one or several of the three gradient directions (slice selection, phase encoding, and frequency encoding). The imaging sequence can be any existing imaging sequence, such as gradient echo, spin echo, EPI sequence, and the like.

The acquisition of a period of displacement requires n phase acquisition points. The entire magnetic resonance elastography acquisition includes n consecutive time series modules, and each time series module collects a specific motion phase acquisition point.

The imaging sequences in each timing module are basically similar. The only difference is the time point when the external trigger point appears. The scanning sequence is set by the magnetic resonance controller to satisfy the generation of the external trigger signal in step S1, and for the scanning gradient and RF Pulse control.

If the start time of the motion sensitive gradient MEG is used as the relative time reference point, and the appearance time point of the external trigger point is changed by adding different delay times, the external trigger point will trigger the external driver to generate continuous external vibration, and the time point of the external trigger point Different start times of external vibrations cause different displacement phase acquisition points; in the acquisition process, the product of each repetition time TR and the number of applied motion-sensitive gradient MEG steps is an integer multiple of the acquisition vibration period.

Next, the present invention will be described in more detail.

Referring to FIG. 2 , assuming that n phase acquisition points are required to acquire a period of cyclic displacement, the entire magnetic resonance elastography acquisition will include n consecutive time sequence modules, each time sequence module acquires a specific motion phase acquisition point. The imaging sequences in each timing module are basically similar, the only difference is the time point when the external trigger point appears. If the start time of the motion sensitive gradient MEG is used as the relative time reference point, the appearance time point of the external trigger point can be changed by adding different delay times. The external trigger point will trigger the external driver to generate continuous external vibration. Different time points of the external trigger point cause different external vibration start times, so different displacement phase acquisition points can be collected. In the acquisition process, each repetition time TR is an integer multiple of the external vibration period.

Embodiments of the present invention provide a magnetic resonance elastography displacement acquisition method and system. The proposed acquisition method is to cooperate with the discontinuous periodic vibration of an electromagnetic driver, and cooperate with the external trigger of the acquisition sequence to realize the periodic vibration matched with the phase encoding, thereby recording the recording. Therefore, the acquisition method of the present invention requires TR×phase sampling number=n×T period, and the main advantage is that the periodic change of the motion-sensitive gradient of the acquisition sequence does not need to be interrupted, and the sequence portability is good; the acquired motion phase shift By triggering an external driver, motion-sensitive gradients do not need to be phase-shifted with external periodic motion.

Those skilled in the art know that, in addition to implementing the system provided by the present invention and its various devices, modules and units in the form of purely computer-readable program codes, the system provided by the present invention and its various devices can be implemented by logically programming the method steps. , modules, and units realize the same function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system provided by the present invention and its various devices, modules and units can be regarded as a kind of hardware components, and the devices, modules and units included in it for realizing various functions can also be regarded as hardware components. The device, module and unit for realizing various functions can also be regarded as both a software module for realizing the method and a structure within a hardware component.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essential content of the present invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily, provided that there is no conflict.

Claims (8)

1. A displacement acquisition method for magnetic resonance elastography is characterized by comprising the following steps:

step S1: setting an external driver, setting external trigger drive and frequency, applying shear fluctuation with certain frequency to a detection object, and generating the propagation of the shear fluctuation in the application object;

step S2: carrying out motion coding on the shearing fluctuation, and acquiring image information of displacement of the shearing fluctuation in the detection object along with time and space changes;

the step S2 of acquiring magnetic resonance elastography signals includes:

step S2.1: adding a motion sensitive gradient MEG into an imaging sequence to encode motion displacement; the motion sensitive gradient frequency is consistent with or inconsistent with the vibration frequency of the driver;

step S2.2: the method comprises the steps that n phase acquisition points are needed for acquisition of a period of displacement, the whole magnetic resonance elastography acquisition comprises n continuous time sequence modules, and each time sequence module acquires a specific motion phase acquisition point;

step S2.3: if the starting time of the motion sensitive gradient MEG is taken as a relative time reference point, the occurrence time point of the external trigger point is changed by adding different time delay time, the external trigger point can trigger an external driver to generate continuous external vibration, the starting time of the external vibration is caused to be different due to different time points of the external trigger point, and thus different displacement phase acquisition points are acquired; during acquisition, the product of the repetition time TR and the number of applied motion sensitive gradient MEG steps is an integer multiple of the acquisition vibration period.

2. The magnetic resonance elastography displacement acquisition method as claimed in claim 1, wherein said step S1 includes:

step S1.1: the work of the driver is controlled by a vibration controller, and the trigger signal for starting vibration is realized by external trigger, which can be set in a magnetic resonance elastography scanning sequence or other external triggers;

step S1.2: aiming at the collection of the shearing fluctuation displacement at different cycle time points, the time point of starting vibration after the triggering of the driver is determined;

step S1.3: the external vibration frequency can be increased by any frequency increment in the range of 0.0001-0.1Hz according to the hardware response time delay.

3. The method according to claim 2, wherein the triggering time point for starting oscillation in step S1.2 can be any time point in the acquired motion cycle, and is determined by the position of the phase sampling point in the acquired motion cycle.

4. A magnetic resonance elastography displacement acquisition method according to claim 3, characterized in that said step S2.1 comprises: the loading direction of the motion sensitive gradient MEG is any one or more of a plurality of gradient directions, wherein the gradient directions comprise layer selection, phase encoding and frequency encoding; the imaging sequence is any existing imaging sequence.

5. A magnetic resonance elastography displacement acquisition method according to claim 3, wherein said step S2.2 comprises: the imaging sequences in each time sequence module are substantially similar, the only difference being the point in time at which the external trigger point occurs, and the scan sequence is set by the magnetic resonance controller to satisfy the external trigger signal generation and control of the scan gradients and RF pulses in step S1.

6. A magnetic resonance elastography displacement acquisition system, comprising:

module M1: setting an external driver, setting an external trigger drive and frequency, applying a certain frequency of shear fluctuation to a detection object, and generating the propagation of the shear fluctuation in the application object;

module M2: carrying out motion coding on the shearing fluctuation, and acquiring image information of displacement of the shearing fluctuation in the detection object along with time and space changes;

the magnetic resonance elastography signal acquisition in the module M2 comprises:

module M2.1: adding a motion sensitive gradient MEG into an imaging sequence to encode motion displacement; the motion sensitive gradient frequency is consistent with or inconsistent with the vibration frequency of the driver;

module M2.2: the method comprises the following steps that n phase acquisition points are needed for acquisition of a period of displacement, the whole magnetic resonance elastography acquisition comprises n continuous time sequence modules, and each time sequence module acquires a specific motion phase acquisition point;

module M2.3: if the starting time of the motion sensitive gradient MEG is taken as a relative time reference point, the occurrence time point of the external trigger point is changed by adding different time delay time, the external trigger point can trigger the external driver to generate continuous external vibration, and the starting time of the external vibration is different due to different time points of the external trigger point, so that different displacement phase acquisition points are acquired; during acquisition, the product of the repetition time TR and the number of applied motion sensitive gradient MEG steps is an integer multiple of the acquisition vibration period.

7. The magnetic resonance elastography displacement acquisition system of claim 6, wherein the module M1 comprises:

module M1.1: the work of the driver is controlled by a vibration controller, and a trigger signal for starting vibration is realized by external trigger, which can be set trigger in a magnetic resonance elastography scanning sequence or other external triggers;

module M1.2: aiming at the collection of the shearing fluctuation displacement at different cycle time points, the time point of starting vibration after the triggering of the driver is determined;

module M1.3: the external vibration frequency can be increased by any frequency increment in the range of 0.0001-0.1Hz for the hardware response time delay.

8. The system according to claim 7, wherein the triggering time point of the module M1.2 to start oscillation can be any time point in the acquired motion cycle, and is determined by the position of the acquired phase sampling point of the motion cycle.

Images