WO2018082026A1 - Spherical k-space collection method and apparatus for three-dimensional dynamic magnetic resonance imaging - Google Patents

Spherical k-space collection method and apparatus for three-dimensional dynamic magnetic resonance imaging Download PDF

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WO2018082026A1
WO2018082026A1 PCT/CN2016/104665 CN2016104665W WO2018082026A1 WO 2018082026 A1 WO2018082026 A1 WO 2018082026A1 CN 2016104665 W CN2016104665 W CN 2016104665W WO 2018082026 A1 WO2018082026 A1 WO 2018082026A1
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echo signal
acquisition
spherical
magnetic resonance
space
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PCT/CN2016/104665
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French (fr)
Chinese (zh)
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朱艳春
李硕
杨洁
谢耀钦
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深圳先进技术研究院
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging

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  • the present application relates to the field of three-dimensional dynamic magnetic resonance imaging technology, and in particular, to a spherical k-space acquisition method and apparatus for three-dimensional dynamic magnetic resonance imaging.
  • Magnetic Resonance Imaging uses nuclear magnetic resonance to excite the spin nuclei in the human body and then receives the electromagnetic signals released by the spin nuclei to reconstruct human tissue image information. It has no radiation, multi-contrast imaging and soft tissue. The advantages of high contrast have become an important tool for clinical medical examination.
  • the data acquired during the magnetic resonance imaging process is called k-space data. All the data are composed of k-space.
  • the acquired trajectory is called k-space trajectory. Reconstruction of k-space data can obtain magnetic resonance images.
  • Dynamic magnetic resonance imaging is a technique for tracking and imaging the dynamic physiological processes of human tissues and organs (such as heart beat, drug metabolism, etc.) by magnetic resonance imaging. This technique performs continuous and repeated scanning of a specific imaging space.
  • a series of time-dependent k-space data is obtained. By filtering and reconstructing these data, a set of dynamic images with time can be obtained. By analyzing the data of the dynamic images, a series of biological and pathological phenomena reflecting the occurrence and development of the lesion can be obtained. Quantitative or semi-quantitative parameters of physiological information. Dynamic magnetic resonance imaging has been widely used in fields such as Cardiac Cine MRI, Dynamic Contrast Enhanced MRI (DCE-MRI).
  • DCE-MRI Dynamic Contrast Enhanced MRI
  • the temporal resolution is low due to the limitation of the acquisition time of the three-dimensional k-space data.
  • organ imaging with approximate periodic motion such as three-dimensional imaging of cardiac films
  • multiple motion cycle repeat acquisition and retrospective reconstruction methods can be used to improve temporal resolution, it is difficult to guarantee acquisition in any time window due to the limitation of the acquisition scheme.
  • the k-space data to arrive is approximately evenly distributed.
  • Current 3D dynamic magnetic resonance imaging acquisition methods are obtained by repeatedly acquiring some or all of the k-space data, such as three-dimensional Cartesian acquisition and three-dimensional radial acquisition.
  • the three-dimensional Cartesian acquisition method realizes the coding in two dimensions by layer selection gradient coding and phase coding, and then realizes the data acquisition in the third dimension by frequency coding, thereby realizing the filling of the three-dimensional k-space.
  • the three-dimensional radial acquisition method achieves the filling of the three-dimensional k-space by simultaneously encoding and collecting the three layers of the selected layer, the phase and the frequency.
  • reconstructing a set of 3D motion images requires repeated acquisition of all or a large amount of 3D k-space data, so the time resolution is low, and the image reconstruction requires the selection of k-space data within a specific time window, and a time is collected. The window is then collected for the next time window to ensure that the magnetic resonance data of the k-space is evenly distributed, so the freedom of image reconstruction is limited.
  • a Cartesian and radial hybrid acquisition method which uses radial acquisition in the plane and Cartesian acquisition in the direction of the selected gradient. Although the acquisition time can be reduced to some extent by undersampling, the k-space data is uniform.
  • Sex is still limited by a certain dimension coding scheme, and the temporal resolution of dynamic imaging is difficult to improve.
  • most of the existing dynamic magnetic resonance imaging techniques achieve dynamic imaging by reconstructing data from post-screening and recombination, so it is generally difficult to obtain continuous dynamic images.
  • an object of the present application is to provide a spherical k-space acquisition method and apparatus suitable for three-dimensional dynamic magnetic resonance imaging, which can realize continuous acquisition of three-dimensional k-space data, so that the acquired k Spatial data is approximately evenly distributed in any time window, enabling dynamic continuous 3D magnetic resonance imaging with high temporal resolution.
  • a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging includes: establishing a spherical k-space model, and determining an acquisition trajectory of an echo signal in the model, wherein the echo
  • the trajectory of the signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the sphere, or a full-echo signal of the diameter of the passing sphere, the elevation angle and azimuth of the echo signal acquisition trajectory Calculated from the two-dimensional golden ratio; according to the collection track Determining a time series of the magnetic resonance scan, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; setting the magnetic resonance imaging system according to the time series and the coding gradient, and acquiring a k-space data filling device conforming to the collected trajectory Said spherical k space.
  • a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging includes: a modeling module for establishing a spherical k-space model, and determining an acquisition trajectory of an echo signal in the model, wherein, the acquisition trajectory of the echo signal is: within the spherical shape, collecting a radius-shaped half-echo signal from the center of the sphere to the spherical surface, or a full-echo signal of a diameter of the passing center, an echo signal
  • the elevation angle and the azimuth angle of the acquisition trajectory are calculated by the two-dimensional golden ratio;
  • the calculation module is configured to determine the time series of the magnetic resonance scan according to the collected trajectory, and calculate the coding gradient of the applied magnetic field required by the magnetic resonance imaging system;
  • the acquisition module And for setting a magnetic resonance imaging system according to the time series and the coding gradient, and acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
  • the technical solution provided by the embodiment of the present application can obtain approximately uniform k-space data at any time, thereby achieving continuous dynamic three-dimensional imaging and realizing dynamic imaging with high time resolution.
  • the specific advantages are as follows:
  • the k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
  • FIG. 1 is a schematic flow chart of a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
  • FIG. 2 is a schematic diagram of an echo line for collecting a half echo signal according to an embodiment of the present application
  • FIG. 3 is a schematic diagram of an echo line for collecting a full echo signal according to an embodiment of the present application
  • FIG. 4 is a schematic flow chart of spherical k-space data acquisition according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of data distribution of a spherical k-space collected in an embodiment of the present application.
  • FIG. 6 is a schematic diagram of three selection modes of a k-space time window in dynamic magnetic resonance image reconstruction according to an embodiment of the present application
  • FIG. 7 is a schematic diagram of k-space data uniformity comparison in different time window selection modes according to an embodiment of the present application.
  • FIG. 8 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
  • FIG. 9 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application.
  • FIG. 10 is an apparatus according to an embodiment of the present invention.
  • Embodiments of the present application provide a spherical k-space acquisition method and apparatus for three-dimensional dynamic magnetic resonance imaging.
  • FIG. 1 is a schematic flow chart of a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application. As shown in Figure 1, the method includes:
  • Step 101 Establish a spherical k-space model, and determine a trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: a radius-shaped half-echo from the center of the sphere to the spherical surface within the sphere Signal, or, the full-echo signal of the diameter of the passing center, the elevation angle ⁇ and azimuth of the echo signal acquisition trajectory Calculated by the two-dimensional golden ratio.
  • Step 102 Determine a time series of the magnetic resonance scan according to the collected trajectory, and calculate a coding gradient of the applied magnetic field required by the magnetic resonance imaging system.
  • Step 103 Set a magnetic resonance imaging system according to the time series and the encoding gradient, and collect k-space data that matches the collected trajectory to fill the spherical k-space.
  • the three-dimensional k-space collected by the embodiment is a sphere as a whole.
  • the direction of the echo is acquired each time, that is, the elevation angle ⁇ and azimuth of the acquired trajectory
  • the two-dimensional golden ratio ⁇ 1 , ⁇ 2 can be respectively calculated, and then the time series of the magnetic resonance scan is determined according to the collected trajectory, and the coding gradient of the applied magnetic field required by the magnetic resonance imaging system is calculated, and then according to the scan time series and
  • the coding gradient writing software program is input into the magnetic resonance imaging system, and the echo signal conforming to the above-mentioned acquisition trajectory can be collected to realize the filling of the three-dimensional spherical k-space. This can make the collected k-space data more uniform and improve the time resolution of dynamic imaging.
  • the two-dimensional golden section scale coefficients are ⁇ 1 and ⁇ 2 , which are obtained according to the eigenvectors of the generalized Fibonacci sequence. After taking the four digits after the decimal point, ⁇ 1 ⁇ 0.6823 and ⁇ 2 ⁇ 0.4656.
  • the elevation angle ⁇ of the echo signal is calculated according to ⁇ 1 , the direction angle Calculated according to ⁇ 2 , or, the elevation angle ⁇ is calculated according to ⁇ 2 , the direction angle Calculated according to ⁇ 1 .
  • the embodiment of the present invention can realize continuous acquisition of three-dimensional k-space, and can obtain an approximately uniform k-space distribution in any acquisition time window, which greatly improves the freedom of selection when reconstructing data, and combines under-sampling reconstruction technology. Dynamic magnetic resonance image reconstruction with high time resolution is available for clinical application needs.
  • the present invention proposes two different acquisition embodiments based on full echo acquisition and half echo acquisition, respectively.
  • the spherical k-space acquisition trajectory of the three-dimensional dynamic magnetic resonance imaging in the embodiment of the present invention is as shown in FIG. 2 and FIG. 3, and the overall acquisition space is a sphere, and ⁇ n and The elevation angle and azimuth angle of the nth acquisition echo signal line are respectively indicated.
  • the magnetic resonance imaging system uses a physical gradient magnetic field in all three coordinate directions of x, y, and z.
  • the spherical k-space acquisition trajectory proposed by the present invention can be arbitrarily rotated with three physical gradient magnetic fields in the magnetic resonance imaging system in practical applications, and all belong to the protection scope of the patent.
  • a signal acquired for a half echo (eg, acquiring an FID signal: free induction decay (FID) is the simplest form of signal in magnetic resonance imaging (MRI)), as shown in FIG. 2
  • FID free induction decay
  • FIG. 2 As shown in the figure, each acquisition echo line starts from the center of the three-dimensional spherical k-space and is collected outward in the radial direction of the ball.
  • the full echo signal acquired by the spherical k-space is shown by the diameter of the sphere in FIG. 3, and each acquired echo is collected from the spherical point through the center of the sphere, and the collected trajectory is a ball. Root diameter.
  • the acquisition matrix of the three-dimensional k-space is: R x ⁇ R y ⁇ R z , where R x , R y , R z represent the number of codes in the x, y, and z directions, respectively.
  • different acquisition schemes can be used respectively.
  • the acquisition trajectory of the echo signal is calculated by the following steps:
  • the elevation angle and the azimuth angle are calculated by:
  • ⁇ n arccos(2mod(n ⁇ 1 ,1)-1)
  • the echo signal is a full-echo signal of a diameter
  • its elevation angle and azimuth angle are calculated by:
  • ⁇ n arccos(mod(n ⁇ 1 ,1))
  • the elevation angle and the azimuth angle are calculated by:
  • ⁇ n arccos(2mod(n ⁇ 1 ,1)-1)
  • arccos(i) is the inverse cosine of i
  • mod(a,b) is the remainder of a/b.
  • r 0, 1, ..., R, where r from 0 to R represents the respective acquisition points on the half-echo line;
  • r -R, -R+1, ..., R, where r from -R to R represents the individual acquisition points on the full echo line.
  • the preset cutoff condition is manually set, for example, the acquisition time is 20 minutes, or 100,000 echo signals are collected.
  • the number n 0 of the initial echo acquired by the echo may be an arbitrary natural number, and the spherical k-space can be filled by collecting uniform k-space data from a track at an arbitrary position.
  • the coding gradient of the applied magnetic field required by the magnetic resonance imaging system is calculated, and the required application at the nth acquisition can be calculated according to the coordinates x n , y n , z n of each collection point on the nth acquisition trajectory.
  • the coding gradient of the magnetic field in three directions.
  • the relationship between the coding gradients G x, y, z applied to the nth acquisition and x n , y n , z n can be described by the following equation, regardless of the actual hardware conditions and the like:
  • k x, y, z are the coordinates of the nth acquisition trajectory in k-space, corresponding to x n , y n and z n ;
  • ⁇ is the gyromagnetic ratio, and the time during which the t gradient is applied.
  • the k-space data is processed to reconstruct a continuous dynamic image.
  • the embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional spherical k-space, thereby facilitating the improvement of the temporal resolution of the dynamic imaging.
  • the uniformity of the k-space data collected by the method of the embodiment of the present application is evaluated by a specific simulation experiment.
  • the k-space resolution is 100 ⁇ 100 ⁇ 100, and the k-space acquisition is a half-echo signal as an example.
  • the case of the full echo signal is similar, and will not be described again.
  • the 500-time half-echo is continuously collected in the three-dimensional spherical k-space, and the distribution of the acquired spherical k-space data on the spherical surface is shown in Fig. 5.
  • the average distance between each point on the sphere and all the points in its neighborhood can be calculated, and then the standard deviation of all these distance values is counted.
  • the standard deviation is closer to 0, indicating that each point is adjacent to it.
  • Figure 6 shows three selection modes of k-space time window in dynamic magnetic resonance image reconstruction, where (a) is a time window of different length, (b) is a time window of different positions, and (c) is a time of different combinations. window.
  • Figure 7 shows the k-space data uniformity comparison in different time window selection modes, including different acquisition times (a), different time window positions (b), and different time window combination times (c).
  • the k-space data collected by the acquisition method of the embodiment of the present invention has good uniformity in the three-dimensional spherical k-space, and the statistical standard deviations in the three different time window selection modes are close to zero, which proves
  • the k-space data obtained by the method of the invention has better spatial uniformity.
  • the spherical k-space acquisition method of the embodiment of the present invention has the following advantages:
  • the k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
  • the embodiment of the present application further provides a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging, which can be used to implement the method described in the above embodiments, as described in the following embodiments. Since the principle of solving the problem of the spherical k-space acquisition device suitable for 3D dynamic magnetic resonance imaging is similar to the spherical k-space acquisition method suitable for 3D dynamic magnetic resonance imaging, it is suitable for the implementation of spherical k-space acquisition device for 3D dynamic magnetic resonance imaging. See the implementation of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging, and the details are not repeated here.
  • unit or “module” may implement a combination of software and/or hardware of a predetermined function.
  • apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.
  • FIG. 8 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application.
  • the device in this embodiment may be configured as a logical component that implements a corresponding function, or may be an electronic device that runs a corresponding functional software.
  • the spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging includes: a modeling module 10, a calculation module 20, and an acquisition module 30.
  • the modeling module 10 is configured to establish a spherical k-space model, and determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: in the spherical shape, the collection is from the center of the sphere to the spherical surface.
  • the radius of the half-echo signal, or the diameter of the full echo signal of the spherical center, the elevation angle and azimuth of the echo signal acquisition trajectory are calculated by the two-dimensional golden ratio.
  • the calculating module 20 is configured to determine a time series of the magnetic resonance scan according to the collected trajectory, and calculate a coding gradient of an applied magnetic field required by the magnetic resonance imaging system;
  • the acquisition module 30 is configured to set the magnetic resonance imaging system according to the time series and the coding gradient, and acquire k-space data conforming to the collected trajectory to fill the spherical k-space.
  • FIG. 9 is a schematic structural view of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application.
  • the modeling module 10 further includes a first calculating unit 11, a second calculating unit 12, and a third calculating unit 13.
  • the modeling module 10 is further configured to determine a collection trajectory of the echo signal by the following steps:
  • the two-dimensional golden section scale coefficient is ⁇ 1 and ⁇ 2 , ⁇ 1 ⁇ 0.6823, ⁇ 2 ⁇ 0.4656; the elevation angle ⁇ of the echo signal is calculated according to ⁇ 1 , the direction angle Calculated according to ⁇ 2 , or, the elevation angle ⁇ is calculated according to ⁇ 2 , the direction angle Calculated according to ⁇ 1 .
  • the number n 0 of the initial echo may be any natural number.
  • the modeling module 10 further includes a first calculating unit 11 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a half-echo signal originating from the center of the sphere:
  • ⁇ n arccos(2mod(n ⁇ 1 ,1)-1)
  • arccos(i) is the inverse cosine of i
  • mod(a,b) is the remainder of a/b.
  • the modeling module 10 further includes a second calculating unit 12 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
  • ⁇ n arccos(mod(n ⁇ 1 ,1))
  • arccos(i) is the inverse cosine of i
  • mod(a,b) is the remainder of a/b.
  • the modeling module 10 further includes a third calculating unit 13 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
  • ⁇ n arccos(2mod(n ⁇ 1 ,1)-1)
  • arccos(i) is the inverse cosine of i
  • mod(a,b) is the remainder of a/b.
  • the device of the embodiment can realize continuous acquisition of three-dimensional k-space data and improve the time resolution of three-dimensional dynamic magnetic resonance imaging, and the specific advantages are as follows:
  • the k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
  • Embodiments of the present invention also provide a computer readable storage medium comprising computer readable instructions, when executed, causing a processor to perform at least the following operations: establishing a spherical k-space model, determining echoes in the model a collecting trajectory of the signal, wherein the trajectory of the echo signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the spherical shape, or a full-echo signal of a diameter of the passing center Elevation angle ⁇ and azimuth of the echo signal acquisition trajectory Calculated by a two-dimensional golden section ratio; determining a time series of the magnetic resonance scan according to the collected trajectory, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; and setting the magnetic resonance imaging system according to the time series and the coding gradient, And acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
  • An embodiment of the present invention further provides an apparatus, as shown in FIG. 10, comprising: a processor 101 and a memory 102 including computer readable instructions that, when executed, cause the processor to perform the following operations: a spherical k-space model for determining a trajectory of an echo signal in the model, wherein the trajectory of the echo signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the sphere, or Diameter-like full echo signal passing through the center of the sphere, elevation angle ⁇ and azimuth of the echo signal acquisition trajectory Calculated by a two-dimensional golden section ratio; determining a time series of the magnetic resonance scan according to the collected trajectory, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; and setting the magnetic resonance imaging system according to the time series and the coding gradient, And acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
  • the embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional cylindrical k-space, and the low-resolution dynamic magnetic resonance image reconstruction can be realized by the under-sampling reconstruction technology, and continuous motion can be realized. Or dynamic imaging.
  • Any process or method description in the flowchart or otherwise described herein can be understood to represent an executable instruction that includes one or more steps for implementing a particular logical function or process. Modules, segments or portions of code, and the scope of the preferred embodiments of the application includes additional implementations, which may not be in the order shown or discussed, including in a substantially simultaneous manner or in reverse order depending on the functionality involved. To perform the functions, this should be understood by those skilled in the art to which the embodiments of the present application pertain.
  • portions of the application can be implemented in hardware, software, firmware, or a combination thereof.
  • multiple steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system.
  • a suitable instruction execution system For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques well known in the art: having logic gates for implementing logic functions on data signals. Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

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Abstract

Proposed are a spherical k-space collection method and apparatus for three-dimensional dynamic magnetic resonance imaging. The method comprises: establishing a spherical k-space model and determining a collection track code of an echo signal in the model, wherein the echo signal is: in the sphere, a radial half-echo signal from a spherical centre to a spherical surface, or a diametral full-echo signal through the spherical centre, and an elevation angle θ and an azimuth angle φ of the echo signal are obtained by means of calculation according to the two-dimensional golden section ratio; and inputting the collection track code into a magnetic resonance imaging system, and collecting k-space data for filling the spherical k-space model according to the collection track code. The method can achieve the continuous collection of three-dimensional k-space data, and make the collected k-space data be approximately and uniformly distributed within any time window, thereby being able to achieve continuous three-dimensional dynamic image reconstruction and high-temporal-resolution three-dimensional dynamic magnetic resonance imaging.

Description

用于三维动态磁共振成像的球形k空间采集方法和装置Spherical k-space acquisition method and device for three-dimensional dynamic magnetic resonance imaging 技术领域Technical field
本申请涉及三维动态磁共振成像技术领域，尤其涉及一种用于三维动态磁共振成像的球形k空间采集方法和装置。The present application relates to the field of three-dimensional dynamic magnetic resonance imaging technology, and in particular, to a spherical k-space acquisition method and apparatus for three-dimensional dynamic magnetic resonance imaging.
背景技术Background technique
磁共振成像(Magnetic Resonance Imaging，MRI)是利用核磁共振现象，激发人体中的自旋核，然后接收自旋核子释放的电磁信号，重建出人体组织图像信息，具有无辐射，多对比度成像和软组织对比度高等优点，目前已经成为临床医学检查的一种重要工具。磁共振成像过程中采集得到的数据叫k空间数据，所有数据整体组成k空间，所用的采集轨迹叫k空间轨迹，对k空间数据进行重建可以得到磁共振图像。动态磁共振成像是利用磁共振成像方法对人体组织器官的动态生理过程(如心脏跳动，药物代谢等)进行跟踪成像的一种技术，该技术通过对一特定的成像空间进行连续重复的扫描，得到一系列与时间相关的k空间数据，通过对这些数据筛选重建可以得到一组随时间变化的动态图像，通过对动态图像做数据分析可以获得一系列反映病变发生、发展过程中生物学和病理生理学信息的定量或半定量参数。动态磁共振成像技术已经广泛应用于如心脏电影磁共振成像(Cardiac Cine MRI)，动态对比度增强磁共振成像(Dynamic Contrast Enhanced MRI，DCE-MRI)等领域。Magnetic Resonance Imaging (MRI) uses nuclear magnetic resonance to excite the spin nuclei in the human body and then receives the electromagnetic signals released by the spin nuclei to reconstruct human tissue image information. It has no radiation, multi-contrast imaging and soft tissue. The advantages of high contrast have become an important tool for clinical medical examination. The data acquired during the magnetic resonance imaging process is called k-space data. All the data are composed of k-space. The acquired trajectory is called k-space trajectory. Reconstruction of k-space data can obtain magnetic resonance images. Dynamic magnetic resonance imaging is a technique for tracking and imaging the dynamic physiological processes of human tissues and organs (such as heart beat, drug metabolism, etc.) by magnetic resonance imaging. This technique performs continuous and repeated scanning of a specific imaging space. A series of time-dependent k-space data is obtained. By filtering and reconstructing these data, a set of dynamic images with time can be obtained. By analyzing the data of the dynamic images, a series of biological and pathological phenomena reflecting the occurrence and development of the lesion can be obtained. Quantitative or semi-quantitative parameters of physiological information. Dynamic magnetic resonance imaging has been widely used in fields such as Cardiac Cine MRI, Dynamic Contrast Enhanced MRI (DCE-MRI).
在这类动态磁共振成像技术中，由于受到三维k空间数据采集时间的限制，时间分辨率较低。在近似周期性运动的器官成像，如心脏电影三维成像中，虽然可以采用多运动周期重复采集和回顾性重建方法来提高时间分辨率，但受到采集方案的限制，很难保证任意时间窗内采集到的k空间数据都近似均匀分布。 In this type of dynamic magnetic resonance imaging technology, the temporal resolution is low due to the limitation of the acquisition time of the three-dimensional k-space data. In organ imaging with approximate periodic motion, such as three-dimensional imaging of cardiac films, although multiple motion cycle repeat acquisition and retrospective reconstruction methods can be used to improve temporal resolution, it is difficult to guarantee acquisition in any time window due to the limitation of the acquisition scheme. The k-space data to arrive is approximately evenly distributed.
目前的三维动态磁共振成像采集方法都是重复采集部分或者全部k空间数据得到的，比如三维笛卡尔采集和三维径向采集。三维笛卡尔采集方法是通过选层梯度编码和相位编码实现两个维度上的编码，然后通过频率编码实现第三维度上的数据采集，以此实现对三维k空间的填充。三维径向采集方法通过对选层，相位和频率三个方向同时编码采集实现对三维k空间的填充。对于这两类方法，重建一组三维动态图像需要重复采集全部或大量的三维k空间数据，因此时间分辨率较低，且图像重建时需要选择特定时间窗内的k空间数据，采集完一个时间窗再进行下一个时间窗采集，以保证k空间的磁共振数据均匀分布，因此图像重建的自由性受到限制。此外还有笛卡尔和径向混合采集方法，该方法在平面内采用径向采集，在选层梯度方向采用笛卡尔采集，虽然通过欠采样采集可以一定程度上降低采集时间，但是k空间数据均匀性仍然受到某一维度编码方案的限制，动态成像的时间分辨率难以提高。此外，现有动态磁共振成像技术大多是通过对后期筛选重组的数据重建来实现动态成像的，因此一般很难获得连续的动态图像。Current 3D dynamic magnetic resonance imaging acquisition methods are obtained by repeatedly acquiring some or all of the k-space data, such as three-dimensional Cartesian acquisition and three-dimensional radial acquisition. The three-dimensional Cartesian acquisition method realizes the coding in two dimensions by layer selection gradient coding and phase coding, and then realizes the data acquisition in the third dimension by frequency coding, thereby realizing the filling of the three-dimensional k-space. The three-dimensional radial acquisition method achieves the filling of the three-dimensional k-space by simultaneously encoding and collecting the three layers of the selected layer, the phase and the frequency. For these two methods, reconstructing a set of 3D motion images requires repeated acquisition of all or a large amount of 3D k-space data, so the time resolution is low, and the image reconstruction requires the selection of k-space data within a specific time window, and a time is collected. The window is then collected for the next time window to ensure that the magnetic resonance data of the k-space is evenly distributed, so the freedom of image reconstruction is limited. In addition, there is a Cartesian and radial hybrid acquisition method, which uses radial acquisition in the plane and Cartesian acquisition in the direction of the selected gradient. Although the acquisition time can be reduced to some extent by undersampling, the k-space data is uniform. Sex is still limited by a certain dimension coding scheme, and the temporal resolution of dynamic imaging is difficult to improve. In addition, most of the existing dynamic magnetic resonance imaging techniques achieve dynamic imaging by reconstructing data from post-screening and recombination, so it is generally difficult to obtain continuous dynamic images.
发明内容Summary of the invention
为解决现有技术中的上述问题，本申请的一个目的在于提出一种适用于三维动态磁共振成像的球形k空间采集方法和装置，可以实现三维k空间数据的连续采集，使采集到的k空间数据在任意时间窗内都近似均匀分布，实现高时间分辨率的动态连续三维磁共振成像。In order to solve the above problems in the prior art, an object of the present application is to provide a spherical k-space acquisition method and apparatus suitable for three-dimensional dynamic magnetic resonance imaging, which can realize continuous acquisition of three-dimensional k-space data, so that the acquired k Spatial data is approximately evenly distributed in any time window, enabling dynamic continuous 3D magnetic resonance imaging with high temporal resolution.
为达到上述目的，本申请实施例提出的适用于三维动态磁共振成像的球形k空间采集方法，包括：建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角与方位角由二维黄金分割比例计算得到；根据所述采集轨 迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。In order to achieve the above object, a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging proposed by the embodiment of the present application includes: establishing a spherical k-space model, and determining an acquisition trajectory of an echo signal in the model, wherein the echo The trajectory of the signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the sphere, or a full-echo signal of the diameter of the passing sphere, the elevation angle and azimuth of the echo signal acquisition trajectory Calculated from the two-dimensional golden ratio; according to the collection track Determining a time series of the magnetic resonance scan, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; setting the magnetic resonance imaging system according to the time series and the coding gradient, and acquiring a k-space data filling device conforming to the collected trajectory Said spherical k space.
为达到上述目的，本申请实施例提出的适用于三维动态磁共振成像的球形k空间采集装置，包括：建模模块，用于建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，采集由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角与方位角由二维黄金分割比例计算得到；计算模块，用于根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；采集模块，用于根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。In order to achieve the above object, a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging proposed by the embodiment of the present application includes: a modeling module for establishing a spherical k-space model, and determining an acquisition trajectory of an echo signal in the model, Wherein, the acquisition trajectory of the echo signal is: within the spherical shape, collecting a radius-shaped half-echo signal from the center of the sphere to the spherical surface, or a full-echo signal of a diameter of the passing center, an echo signal The elevation angle and the azimuth angle of the acquisition trajectory are calculated by the two-dimensional golden ratio; the calculation module is configured to determine the time series of the magnetic resonance scan according to the collected trajectory, and calculate the coding gradient of the applied magnetic field required by the magnetic resonance imaging system; the acquisition module And for setting a magnetic resonance imaging system according to the time series and the coding gradient, and acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
本申请实施例提供的技术方案，能够在任一时刻采集得到近似均匀的k空间数据，进而可以实现连续动态的三维成像，实现高时间分辨率的动态成像，具体优点如下：The technical solution provided by the embodiment of the present application can obtain approximately uniform k-space data at any time, thereby achieving continuous dynamic three-dimensional imaging and realizing dynamic imaging with high time resolution. The specific advantages are as follows:
1、均匀性方面：可以实现任意长度时间窗内、任意位置时间窗内、任意组合时间窗内采集的数据，在三维球形k空间内都近似均匀分布。因此，在进行图像重建时数据的选择具有较高的自由性，通过适当的图像重建方法可以获得具有较高时间分辨率的动态影像。1. Uniformity: It can realize the data collected in any length time window, in any position time window, and in any combination time window, which is approximately evenly distributed in the three-dimensional spherical k space. Therefore, the selection of data has a high degree of freedom in image reconstruction, and a dynamic image with higher temporal resolution can be obtained by an appropriate image reconstruction method.
2、适用范围方面：分别提出了适用于全回波采集和半回波采集的k空间采集方法，都可以实现近似均匀的k空间分布，因此既可应用在采集全回波信号的序列(如稳态自由进动序列等)，也可应用在采集半回波信号的序列(如超短回波时间序列等)，应用范围广。2. Scope of application: The k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
3、应用方面：有利于对动态生理过程进行三维磁共振成像(如动态对比度增强磁共振成像，DCE-MRI)，还有利于对近似周期性运动的器官进行三维磁共振成像(如心脏，胃，肺等)。 3. Application: It is beneficial to perform three-dimensional magnetic resonance imaging (such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on dynamic physiological processes, and also facilitates three-dimensional magnetic resonance imaging of organs with approximate periodic motion (such as heart, stomach). , lungs, etc.).
本申请附加的方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本申请的实践了解到。The aspects and advantages of the present invention will be set forth in part in the description which follows.
附图说明DRAWINGS
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings to be used in the embodiments or the prior art description will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present application, and other drawings can be obtained according to the drawings without any creative work for those skilled in the art.
图1是本申请一实施例的适用于三维动态磁共振成像的球形k空间采集方法的流程示意图；1 is a schematic flow chart of a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
图2是本申请一实施例的采集半回波信号的回波线示意图；2 is a schematic diagram of an echo line for collecting a half echo signal according to an embodiment of the present application;
图3是本申请一实施例的采集全回波信号的回波线示意图；3 is a schematic diagram of an echo line for collecting a full echo signal according to an embodiment of the present application;
图4是本申请一实施例的球形k空间数据采集的流程示意图；4 is a schematic flow chart of spherical k-space data acquisition according to an embodiment of the present application;
图5是本申请一实施例采集到的球形k空间的数据分布情况示意图；FIG. 5 is a schematic diagram of data distribution of a spherical k-space collected in an embodiment of the present application; FIG.
图6是本申请一实施例的动态磁共振图像重建中k空间时间窗的三种选择模式的示意图；6 is a schematic diagram of three selection modes of a k-space time window in dynamic magnetic resonance image reconstruction according to an embodiment of the present application;
图7是本申请一具体实施例的相应不同的时间窗选择模式下的k空间数据均匀性对比示意图；7 is a schematic diagram of k-space data uniformity comparison in different time window selection modes according to an embodiment of the present application;
图8是本申请一实施例的适用于三维动态磁共振成像的球形k空间采集装置的结构示意图；8 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
图9是本申请另一实施例的适用于三维动态磁共振成像的球形k空间采集装置的结构示意图；9 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application;
图10是本发明实施例提供的一种设备。FIG. 10 is an apparatus according to an embodiment of the present invention.
具体实施方式 Detailed ways
本申请实施例提供一种用于三维动态磁共振成像的球形k空间采集方法和装置。Embodiments of the present application provide a spherical k-space acquisition method and apparatus for three-dimensional dynamic magnetic resonance imaging.
为了使本技术领域的人员更好地理解本申请中的技术方案，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都应当属于本申请保护的范围。The technical solutions in the embodiments of the present application are clearly and completely described in the following, in which the technical solutions in the embodiments of the present application are clearly and completely described. The embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without departing from the inventive scope shall fall within the scope of the application.
图1是本申请一实施例提出的适用于三维动态磁共振成像的球形k空间采集方法的流程示意图。如图1所示，该方法包括：FIG. 1 is a schematic flow chart of a spherical k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application. As shown in Figure 1, the method includes:
步骤101，建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角θ与方位角
Figure PCTCN2016104665-appb-000001
由二维黄金分割比例计算得到。Step 101: Establish a spherical k-space model, and determine a trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: a radius-shaped half-echo from the center of the sphere to the spherical surface within the sphere Signal, or, the full-echo signal of the diameter of the passing center, the elevation angle θ and azimuth of the echo signal acquisition trajectory
Figure PCTCN2016104665-appb-000001
Calculated by the two-dimensional golden ratio.
步骤102，根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度。Step 102: Determine a time series of the magnetic resonance scan according to the collected trajectory, and calculate a coding gradient of the applied magnetic field required by the magnetic resonance imaging system.
步骤103，根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。Step 103: Set a magnetic resonance imaging system according to the time series and the encoding gradient, and collect k-space data that matches the collected trajectory to fill the spherical k-space.
具体地，本实施例采集的三维k空间整体是一个球体。在三维球形k空间中，每次采集回波的方向即采集轨迹的仰角θ和方位角
Figure PCTCN2016104665-appb-000002
可以分别由二维黄金分割比例γ1，γ2计算得到，然后根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度，然后根据扫描时间序列及编码梯度编写软件程序输入到磁共振成像***，即可采集符合上述采集轨迹的回波信号实现对三维球形k空间的填充。这样可以使采集到的k空间数据更均匀，提高动态成像的时间分辨率。 Specifically, the three-dimensional k-space collected by the embodiment is a sphere as a whole. In the three-dimensional spherical k-space, the direction of the echo is acquired each time, that is, the elevation angle θ and azimuth of the acquired trajectory
Figure PCTCN2016104665-appb-000002
The two-dimensional golden ratio γ 1 , γ 2 can be respectively calculated, and then the time series of the magnetic resonance scan is determined according to the collected trajectory, and the coding gradient of the applied magnetic field required by the magnetic resonance imaging system is calculated, and then according to the scan time series and The coding gradient writing software program is input into the magnetic resonance imaging system, and the echo signal conforming to the above-mentioned acquisition trajectory can be collected to realize the filling of the three-dimensional spherical k-space. This can make the collected k-space data more uniform and improve the time resolution of dynamic imaging.
进一步地，二维黄金分割比例系数为γ1和γ2，是根据广义斐波那契数列的特征向量得到的，取小数点后四位后，γ1≈0.6823和γ2≈0.4656。所述回波信号的仰角θ依据γ1计算，方向角
Figure PCTCN2016104665-appb-000003
依据γ2计算，或者，仰角θ依据γ2计算，方向角
Figure PCTCN2016104665-appb-000004
依据γ1计算。Further, the two-dimensional golden section scale coefficients are γ 1 and γ 2 , which are obtained according to the eigenvectors of the generalized Fibonacci sequence. After taking the four digits after the decimal point, γ 1 ≈ 0.6823 and γ 2 ≈ 0.4656. The elevation angle θ of the echo signal is calculated according to γ 1 , the direction angle
Figure PCTCN2016104665-appb-000003
Calculated according to γ 2 , or, the elevation angle θ is calculated according to γ 2 , the direction angle
Figure PCTCN2016104665-appb-000004
Calculated according to γ 1 .
基于以上，本发明实施例可以实现三维k空间的连续采集，并且在任意采集时间窗内都可以得到近似均匀的k空间分布，大大提高了重建数据时的选择自由性，同时结合欠采样重建技术可以实现高时间分辨率的动态磁共振图像重建，适用于临床的应用需求。Based on the above, the embodiment of the present invention can realize continuous acquisition of three-dimensional k-space, and can obtain an approximately uniform k-space distribution in any acquisition time window, which greatly improves the freedom of selection when reconstructing data, and combines under-sampling reconstruction technology. Dynamic magnetic resonance image reconstruction with high time resolution is available for clinical application needs.
进一步地，本发明分别提出了基于全回波采集和基于半回波采集两种不同的采集实施例。本发明实施例中的三维动态磁共振成像的球形k空间采集轨迹如图2和图3所示，整体采集空间为一个球形，图中θn和
Figure PCTCN2016104665-appb-000005
分别表示第n次采集回波信号线的仰角和方位角。为了得到任意层面的空间信息，磁共振成像***在x，y，z三个坐标方向均使用物理梯度磁场。本发明提出的球形k空间采集轨迹在实际应用中可以与磁共振成像***中的三个物理梯度磁场任意旋转对应，都属于本专利的保护范围。Further, the present invention proposes two different acquisition embodiments based on full echo acquisition and half echo acquisition, respectively. The spherical k-space acquisition trajectory of the three-dimensional dynamic magnetic resonance imaging in the embodiment of the present invention is as shown in FIG. 2 and FIG. 3, and the overall acquisition space is a sphere, and θ n and
Figure PCTCN2016104665-appb-000005
The elevation angle and azimuth angle of the nth acquisition echo signal line are respectively indicated. In order to obtain spatial information of any level, the magnetic resonance imaging system uses a physical gradient magnetic field in all three coordinate directions of x, y, and z. The spherical k-space acquisition trajectory proposed by the present invention can be arbitrarily rotated with three physical gradient magnetic fields in the magnetic resonance imaging system in practical applications, and all belong to the protection scope of the patent.
在本申请的一个实施例中，针对半回波采集的信号(如采集FID信号：自由感应衰减(free induction decay,FID)是磁共振成像(MRI)中最简单的信号形式)，如图2中所示，每次采集回波线从三维球形k空间中心开始，沿球的径向方向向外采集。In one embodiment of the present application, a signal acquired for a half echo (eg, acquiring an FID signal: free induction decay (FID) is the simplest form of signal in magnetic resonance imaging (MRI)), as shown in FIG. 2 As shown in the figure, each acquisition echo line starts from the center of the three-dimensional spherical k-space and is collected outward in the radial direction of the ball.
在本申请的另一个实施例中，球形k空间采集的全回波信号如图3中球体直径所示，每次采集的回波从球面一点开始穿过球心采集，采集轨迹为球的一根直径。In another embodiment of the present application, the full echo signal acquired by the spherical k-space is shown by the diameter of the sphere in FIG. 3, and each acquired echo is collected from the spherical point through the center of the sphere, and the collected trajectory is a ball. Root diameter.
无论是全回波采集还是半回波采集，在球形k空间中，每次采集回波的方向均可由θ和
Figure PCTCN2016104665-appb-000006
两个参数确定。因此，设计适用于高时间分辨率的三维动 态磁共振球形k空间采集方案只需优化θ和
Figure PCTCN2016104665-appb-000007
这两个参数。因此如果要实现高时间分辨率的三维k空间采集，只需优化θ和
Figure PCTCN2016104665-appb-000008
这两个参数。Whether it is full echo acquisition or half echo acquisition, in the spherical k-space, the direction of each acquisition echo can be determined by θ and
Figure PCTCN2016104665-appb-000006
Two parameters are determined. Therefore, designing a three-dimensional dynamic magnetic resonance spherical k-space acquisition scheme for high temporal resolution requires only optimization of θ and
Figure PCTCN2016104665-appb-000007
These two parameters. So if you want to achieve high time resolution 3D k-space acquisition, just optimize θ and
Figure PCTCN2016104665-appb-000008
These two parameters.
假定三维k空间的采集矩阵为：Rx×Ry×Rz，其中Rx，Ry，Rz分别表示x，y，z方向的编码数。在三维球形k空间中，Rx＝Ry＝Rz＝2R。针对半回波采集和全回波采集，可分别采用不同的采集方案。It is assumed that the acquisition matrix of the three-dimensional k-space is: R x × R y × R z , where R x , R y , R z represent the number of codes in the x, y, and z directions, respectively. In the three-dimensional spherical k space, R x = R y = R z = 2R. For half-echo acquisition and full echo acquisition, different acquisition schemes can be used respectively.
根据本申请的一个实施例，如图4所示，回波信号的采集轨迹通过以下步骤计算：According to an embodiment of the present application, as shown in FIG. 4, the acquisition trajectory of the echo signal is calculated by the following steps:
1)设定第n次采集的回波信号在球坐标系下对应的参数为：仰角θn与方位角
Figure PCTCN2016104665-appb-000009
初始回波的编号为n＝n0。1) Set the echo signal of the nth acquisition to correspond to the parameters in the spherical coordinate system: elevation angle θ n and azimuth angle
Figure PCTCN2016104665-appb-000009
The initial echo number is n=n 0 .
2)根据二维黄金分割比例系数，计算第n次采集的回波信号的仰角θn与方位角
Figure PCTCN2016104665-appb-000010
2) Calculate the elevation angle θ n and azimuth of the echo signal acquired for the nth time according to the two-dimensional golden section scale factor
Figure PCTCN2016104665-appb-000010
具体地，当所述回波信号是由球心出发的半回波信号时，通过下式计算其仰角和方位角：Specifically, when the echo signal is a half-echo signal originating from the center of the sphere, the elevation angle and the azimuth angle are calculated by:
θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
Figure PCTCN2016104665-appb-000011
Figure PCTCN2016104665-appb-000011
当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：When the echo signal is a full-echo signal of a diameter, its elevation angle and azimuth angle are calculated by:
θn＝arccos(mod(n·γ1,1))θ n =arccos(mod(n·γ 1 ,1))
Figure PCTCN2016104665-appb-000012
Figure PCTCN2016104665-appb-000012
或者，根据本申请另一实施例，通过下式计算其仰角和方位角：Alternatively, according to another embodiment of the present application, the elevation angle and the azimuth angle are calculated by:
θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
Figure PCTCN2016104665-appb-000013
Figure PCTCN2016104665-appb-000013
其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
3)根据θn和
Figure PCTCN2016104665-appb-000014
计算第n次采集的回波信号上的各个采集点在笛卡尔坐标系下的坐标xn,yn,zn： 3) According to θ n and
Figure PCTCN2016104665-appb-000014
Calculate the coordinates x n , y n , z n of the respective acquisition points on the echo signal acquired in the nth time in the Cartesian coordinate system:
Figure PCTCN2016104665-appb-000015
Figure PCTCN2016104665-appb-000015
Figure PCTCN2016104665-appb-000016
Figure PCTCN2016104665-appb-000016
zn＝r·cos(θn)z n =r·cos(θ n )
对于半回波信号：r＝0,1,...,R，其中r从0到R表示半回波线上各个采集点；For half-echo signals: r = 0, 1, ..., R, where r from 0 to R represents the respective acquisition points on the half-echo line;
对于全回波信号：r＝-R,-R+1,...,R，其中r从-R到R表示全回波线上各个采集点。For full echo signals: r = -R, -R+1, ..., R, where r from -R to R represents the individual acquisition points on the full echo line.
4)根据预设截止条件判断采集是否结束，即第n次采集的回波信号是否为采集的最后一条回波信号。4) According to the preset cutoff condition, it is judged whether the acquisition is finished, that is, whether the echo signal acquired in the nth time is the last echo signal collected.
其中，预设的截止条件由人为设定，例如是采集时间为20分钟，或者，采集10万次回波信号等。The preset cutoff condition is manually set, for example, the acquisition time is 20 minutes, or 100,000 echo signals are collected.
5)若是，则采集结束，否则使n＝n+1，重复1)到4)直至采集结束。5) If yes, the acquisition ends, otherwise let n=n+1, repeat 1) to 4) until the end of the acquisition.
根据本申请的一个实施例，上述回波采集的所述初始回波的编号n0可以为任意自然数，能够从任意位置一条轨迹开始采集均匀的k空间数据对球形k空间进行填充。According to an embodiment of the present application, the number n 0 of the initial echo acquired by the echo may be an arbitrary natural number, and the spherical k-space can be filled by collecting uniform k-space data from a track at an arbitrary position.
根据本申请的一个实施例，计算磁共振成像***所需施加磁场的编码梯度，可以根据第n次采集轨迹上各个采集点坐标xn，yn，zn计算第n次采集时所需施加的三个方向磁场的编码梯度。在不考虑实际硬件条件等限制时，第n次采集时所施加的编码梯度Gx,y,z与xn，yn，zn的关系可由下式描述：According to an embodiment of the present application, the coding gradient of the applied magnetic field required by the magnetic resonance imaging system is calculated, and the required application at the nth acquisition can be calculated according to the coordinates x n , y n , z n of each collection point on the nth acquisition trajectory. The coding gradient of the magnetic field in three directions. The relationship between the coding gradients G x, y, z applied to the nth acquisition and x n , y n , z n can be described by the following equation, regardless of the actual hardware conditions and the like:
Figure PCTCN2016104665-appb-000017
Figure PCTCN2016104665-appb-000017
其中，kx,y,z为第n次采集轨迹在k空间内的坐标，对应于xn，yn和zn；γ为旋磁比，t梯度施加的时间。Where k x, y, z are the coordinates of the nth acquisition trajectory in k-space, corresponding to x n , y n and z n ; γ is the gyromagnetic ratio, and the time during which the t gradient is applied.
在所述根据所述编码采集相应的k空间数据之后，对所述k空间数据进行处理，重建得到连续的动态图像。 After the corresponding k-space data is collected according to the code, the k-space data is processed to reconstruct a continuous dynamic image.
本申请实施例可以实现在任意时间窗内采集的数据在三维球形k空间内都近似均匀分布，因此有利于提高动态成像的时间分辨率。下面通过具体模拟实验评估采用本申请实施例的方法采集到的k空间数据的均匀性。The embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional spherical k-space, thereby facilitating the improvement of the temporal resolution of the dynamic imaging. The uniformity of the k-space data collected by the method of the embodiment of the present application is evaluated by a specific simulation experiment.
以k空间分辨率为100×100×100，k空间采集的是半回波信号为例进行阐述，全回波信号的情况与此类似，不再赘述。在三维球形k空间内连续采集500次半回波，采集的球形k空间的数据在球面上的分布情况如图5所示。The k-space resolution is 100×100×100, and the k-space acquisition is a half-echo signal as an example. The case of the full echo signal is similar, and will not be described again. The 500-time half-echo is continuously collected in the three-dimensional spherical k-space, and the distribution of the acquired spherical k-space data on the spherical surface is shown in Fig. 5.
为了评估k空间数据均匀性，可计算球面上每个点与之邻域内所有点的平均距离，然后统计所有这些距离值的标准差，标准差越趋近于0，表示每个点与之邻域内点之间的距离越相近，即表示分布越均匀。每个点的邻域范围为在球面上以该点为中心，立体角为Ω＝4π2/T的球面圆域，其中T为采集总次数。图6所示为动态磁共振图像重建中k空间时间窗的三种选择模式，其中(a)为不同长度的时间窗，(b)为不同位置的时间窗，(c)为不同组合的时间窗。图7给出了相应不同的时间窗选择模式下的k空间数据均匀性对比，包括不同的采集次数(a)、不同的时间窗位置(b)以及不同的时间窗组合次数(c)三种条件下三维球形k空间数据分布均匀性对比，其中(b)和(c)的采集次数为5000。In order to evaluate the k-space data uniformity, the average distance between each point on the sphere and all the points in its neighborhood can be calculated, and then the standard deviation of all these distance values is counted. The standard deviation is closer to 0, indicating that each point is adjacent to it. The closer the distances between points in the domain, the more uniform the distribution. The neighborhood of each point is a sphere circle centered on the sphere at the point and the solid angle is Ω=4π 2 /T, where T is the total number of acquisitions. Figure 6 shows three selection modes of k-space time window in dynamic magnetic resonance image reconstruction, where (a) is a time window of different length, (b) is a time window of different positions, and (c) is a time of different combinations. window. Figure 7 shows the k-space data uniformity comparison in different time window selection modes, including different acquisition times (a), different time window positions (b), and different time window combination times (c). The uniformity of the distribution of the three-dimensional spherical k-space data under the condition, wherein the number of acquisitions of (b) and (c) is 5000.
由以上评估结果可以看出，本发明实施例的采集方法采集的k空间数据在三维球形k空间内均匀性很好，在三种不同时间窗选择模式下的统计标准差均接近于0，证明采用本发明的方法得到的k空间数据具有较好的空间均匀性。It can be seen from the above evaluation results that the k-space data collected by the acquisition method of the embodiment of the present invention has good uniformity in the three-dimensional spherical k-space, and the statistical standard deviations in the three different time window selection modes are close to zero, which proves The k-space data obtained by the method of the invention has better spatial uniformity.
综上所述，本发明实施例的球形k空间采集方法具备如下优点：In summary, the spherical k-space acquisition method of the embodiment of the present invention has the following advantages:
1、均匀性方面：可以实现任意长度时间窗内、任意位置时间窗内、任意组合时间窗内采集的数据，在三维球形k空间内都近似均匀分布。因此，在进行图像重建时数据的选择具有较高的自由性，通过适当的图像重建方法可以获得具有较高时间分辨率的动态影像。 1. Uniformity: It can realize the data collected in any length time window, in any position time window, and in any combination time window, which is approximately evenly distributed in the three-dimensional spherical k space. Therefore, the selection of data has a high degree of freedom in image reconstruction, and a dynamic image with higher temporal resolution can be obtained by an appropriate image reconstruction method.
2、适用范围方面：分别提出了适用于全回波采集和半回波采集的k空间采集方法，都可以实现近似均匀的k空间分布，因此既可应用在采集全回波信号的序列(如稳态自由进动序列等)，也可应用在采集半回波信号的序列(如超短回波时间序列等)，应用范围广。2. Scope of application: The k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
3、应用方面：有利于对动态生理过程进行三维磁共振成像(如动态对比度增强磁共振成像，DCE-MRI)，还有利于对近似周期性运动的器官进行三维磁共振成像(如心脏，胃，肺等)。3. Application: It is beneficial to perform three-dimensional magnetic resonance imaging (such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on dynamic physiological processes, and also facilitates three-dimensional magnetic resonance imaging of organs with approximate periodic motion (such as heart, stomach). , lungs, etc.).
基于同一发明构思，本申请实施例还提供了一种适用于三维动态磁共振成像的球形k空间采集装置，可以用于实现上述实施例所描述的方法，如下面的实施例所述。由于适用于三维动态磁共振成像的球形k空间采集装置解决问题的原理与适用于三维动态磁共振成像的球形k空间采集方法相似，因此适用于三维动态磁共振成像的球形k空间采集装置的实施可以参见适用于三维动态磁共振成像的球形k空间采集装置的实施，重复之处不再赘述。以下所使用的，术语“单元”或者“模块”可以实现预定功能的软件和/或硬件的组合。尽管以下实施例所描述的装置较佳地以软件来实现，但是硬件，或者软件和硬件的组合的实现也是可能并被构想的。Based on the same inventive concept, the embodiment of the present application further provides a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging, which can be used to implement the method described in the above embodiments, as described in the following embodiments. Since the principle of solving the problem of the spherical k-space acquisition device suitable for 3D dynamic magnetic resonance imaging is similar to the spherical k-space acquisition method suitable for 3D dynamic magnetic resonance imaging, it is suitable for the implementation of spherical k-space acquisition device for 3D dynamic magnetic resonance imaging. See the implementation of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging, and the details are not repeated here. As used hereinafter, the term "unit" or "module" may implement a combination of software and/or hardware of a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.
图8是本申请一实施例的适用于三维动态磁共振成像的球形k空间采集装置的结构示意图。本实施例的装置可以为实现相应功能的逻辑部件构成，也可以为运行有相应功能软件的电子设备。如图8所示，该适用于三维动态磁共振成像的球形k空间采集装置包括：建模模块10、计算模块20和采集模块30。FIG. 8 is a schematic structural diagram of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application. The device in this embodiment may be configured as a logical component that implements a corresponding function, or may be an electronic device that runs a corresponding functional software. As shown in FIG. 8, the spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging includes: a modeling module 10, a calculation module 20, and an acquisition module 30.
具体地，建模模块10用于建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，采集由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角与方位角由二维黄金分割比例计算得到。 Specifically, the modeling module 10 is configured to establish a spherical k-space model, and determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: in the spherical shape, the collection is from the center of the sphere to the spherical surface. The radius of the half-echo signal, or the diameter of the full echo signal of the spherical center, the elevation angle and azimuth of the echo signal acquisition trajectory are calculated by the two-dimensional golden ratio.
计算模块20用于根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；The calculating module 20 is configured to determine a time series of the magnetic resonance scan according to the collected trajectory, and calculate a coding gradient of an applied magnetic field required by the magnetic resonance imaging system;
采集模块30用于根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。The acquisition module 30 is configured to set the magnetic resonance imaging system according to the time series and the coding gradient, and acquire k-space data conforming to the collected trajectory to fill the spherical k-space.
图9所示是本申请另一实施例的适用于三维动态磁共振成像的球形k空间采集装置的结构示意图。如图9所示，在图8的基础上，建模模块10还包括第一计算单元11、第二计算单元12和第三计算单元13。FIG. 9 is a schematic structural view of a spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application. As shown in FIG. 9, on the basis of FIG. 8, the modeling module 10 further includes a first calculating unit 11, a second calculating unit 12, and a third calculating unit 13.
具体地，所述建模模块10还用于通过以下步骤确定回波信号的采集轨迹：Specifically, the modeling module 10 is further configured to determine a collection trajectory of the echo signal by the following steps:
1)设第n次采集的回波信号在球坐标系下对应的参数为：仰角θn与方位角
Figure PCTCN2016104665-appb-000018
初始回波的编号为n＝n0；1) Let the corresponding parameters of the echo signal acquired in the nth time in the spherical coordinate system be: elevation angle θ n and azimuth angle
Figure PCTCN2016104665-appb-000018
The initial echo number is n=n 0 ;
2)根据二维黄金分割比例系数，计算第n次采集的回波信号的仰角θn与方位角
Figure PCTCN2016104665-appb-000019
2) Calculate the elevation angle θ n and azimuth of the echo signal acquired for the nth time according to the two-dimensional golden section scale factor
Figure PCTCN2016104665-appb-000019
3)根据θn和
Figure PCTCN2016104665-appb-000020
计算第n次采集的回波信号上的各个采集点在笛卡尔坐标系下的坐标xn,yn,zn；3) According to θ n and
Figure PCTCN2016104665-appb-000020
Calculating the coordinates x n , y n , z n of the respective acquisition points on the echo signal acquired in the nth time in a Cartesian coordinate system;
4)根据预设截止条件判断采集是否结束，即第n次采集的回波信号是否为采集的最后一条回波信号；4) judging whether the acquisition is finished according to the preset cutoff condition, that is, whether the echo signal acquired in the nth time is the last echo signal collected;
5)若是，则采集结束，否则使n＝n+1，重复1)到4)直至采集结束。5) If yes, the acquisition ends, otherwise let n=n+1, repeat 1) to 4) until the end of the acquisition.
其中，所述二维黄金分割比例系数为γ1和γ2，γ1≈0.6823，γ2≈0.4656；所述回波信号的仰角θ依据γ1计算，方向角
Figure PCTCN2016104665-appb-000021
依据γ2计算，或者，仰角θ依据γ2计算，方向角
Figure PCTCN2016104665-appb-000022
依据γ1计算。Wherein, the two-dimensional golden section scale coefficient is γ 1 and γ 2 , γ 1 ≈ 0.6823, γ 2 ≈ 0.4656; the elevation angle θ of the echo signal is calculated according to γ 1 , the direction angle
Figure PCTCN2016104665-appb-000021
Calculated according to γ 2 , or, the elevation angle θ is calculated according to γ 2 , the direction angle
Figure PCTCN2016104665-appb-000022
Calculated according to γ 1 .
其中，所述初始回波的编号n0可以为任意自然数。The number n 0 of the initial echo may be any natural number.
建模模块10还包括第一计算单元11，用于当所述回波信号是由球心出发的半回波信号时，通过下式计算其仰角和方位角： The modeling module 10 further includes a first calculating unit 11 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a half-echo signal originating from the center of the sphere:
θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
Figure PCTCN2016104665-appb-000023
Figure PCTCN2016104665-appb-000023
其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
建模模块10还包括第二计算单元12，用于当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：The modeling module 10 further includes a second calculating unit 12 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
θn＝arccos(mod(n·γ1,1))θ n =arccos(mod(n·γ 1 ,1))
Figure PCTCN2016104665-appb-000024
Figure PCTCN2016104665-appb-000024
其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
建模模块10还包括第三计算单元13，用于当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：The modeling module 10 further includes a third calculating unit 13 for calculating the elevation angle and the azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
Figure PCTCN2016104665-appb-000025
Figure PCTCN2016104665-appb-000025
其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
本实施例的装置可以实现三维k空间数据的连续采集，提高三维动态磁共振成像的时间分辨率，具体体现为如下优点：The device of the embodiment can realize continuous acquisition of three-dimensional k-space data and improve the time resolution of three-dimensional dynamic magnetic resonance imaging, and the specific advantages are as follows:
1、均匀性方面：可以实现任意长度时间窗内、任意位置时间窗内、任意组合时间窗内采集的数据，在三维球形k空间内都近似均匀分布。因此，在进行图像重建时数据的选择具有较高的自由性，通过方法可以获得具有较高时间分辨率的动态影像。1. Uniformity: It can realize the data collected in any length time window, in any position time window, and in any combination time window, which is approximately evenly distributed in the three-dimensional spherical k space. Therefore, the selection of data during image reconstruction has a high degree of freedom, and a dynamic image with higher temporal resolution can be obtained by the method.
2、适用范围方面：分别提出了适用于全回波采集和半回波采集的k空间采集方法，都可以实现近似均匀的k空间分布，因此既可应用在采集全回波信号的序列(如稳态自由进动序列等)，也可应用在采集半回波信号的序列(如超短回波时间序列等)，应用范围广。2. Scope of application: The k-space acquisition method for full echo acquisition and half-echo acquisition is proposed respectively, which can achieve an approximately uniform k-space distribution, so it can be applied to the sequence of acquiring full echo signals (such as The steady-state free precession sequence, etc.) can also be applied to the sequence of collecting half-echo signals (such as ultra-short echo time series, etc.), and has a wide application range.
3、应用方面：有利于对动态生理过程进行三维磁共振成像(如动态对比度增强磁共振成像，DCE-MRI)，还有利于对近似周期性运动的器官进行三维磁共振成像(如心脏，胃，肺等)。 3. Application: It is beneficial to perform three-dimensional magnetic resonance imaging (such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on dynamic physiological processes, and also facilitates three-dimensional magnetic resonance imaging of organs with approximate periodic motion (such as heart, stomach). , lungs, etc.).
本发明实施例还提供了一种包括计算机可读指令的计算机可读存储介质，该计算机可读指令在被执行时使处理器至少执行以下操作：建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角θ与方位角
Figure PCTCN2016104665-appb-000026
由二维黄金分割比例计算得到；根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。Embodiments of the present invention also provide a computer readable storage medium comprising computer readable instructions, when executed, causing a processor to perform at least the following operations: establishing a spherical k-space model, determining echoes in the model a collecting trajectory of the signal, wherein the trajectory of the echo signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the spherical shape, or a full-echo signal of a diameter of the passing center Elevation angle θ and azimuth of the echo signal acquisition trajectory
Figure PCTCN2016104665-appb-000026
Calculated by a two-dimensional golden section ratio; determining a time series of the magnetic resonance scan according to the collected trajectory, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; and setting the magnetic resonance imaging system according to the time series and the coding gradient, And acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
本发明实施例还提供了一种设备，如图10所示，该设备包括：处理器101和包括计算机可读指令的存储器102，计算机可读指令在被执行时使处理器执行以下操作：建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角θ与方位角
Figure PCTCN2016104665-appb-000027
由二维黄金分割比例计算得到；根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。An embodiment of the present invention further provides an apparatus, as shown in FIG. 10, comprising: a processor 101 and a memory 102 including computer readable instructions that, when executed, cause the processor to perform the following operations: a spherical k-space model for determining a trajectory of an echo signal in the model, wherein the trajectory of the echo signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the sphere, or Diameter-like full echo signal passing through the center of the sphere, elevation angle θ and azimuth of the echo signal acquisition trajectory
Figure PCTCN2016104665-appb-000027
Calculated by a two-dimensional golden section ratio; determining a time series of the magnetic resonance scan according to the collected trajectory, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system; and setting the magnetic resonance imaging system according to the time series and the coding gradient, And acquiring k-space data conforming to the collected trajectory to fill the spherical k-space.
本申请实施例可以实现在任意时间窗内采集的数据在三维圆柱形k空间内都近似均匀分布，结合欠采样重建技术可以实现高时间分辨率的动态磁共振图像重建，并且可以实现连续的运动或动态成像。The embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional cylindrical k-space, and the low-resolution dynamic magnetic resonance image reconstruction can be realized by the under-sampling reconstruction technology, and continuous motion can be realized. Or dynamic imaging.
需要说明的是，在本申请的描述中，术语“第一”、“第二”等仅用于描述目的，而不能理解为指示或暗示相对重要性。此外，在本申请的描述中，除非另有说明，“多个”的含义是两个或两个以上。It should be noted that in the description of the present application, the terms "first", "second" and the like are used for descriptive purposes only, and are not to be construed as indicating or implying relative importance. Further, in the description of the present application, the meaning of "a plurality" is two or more unless otherwise stated.
流程图中或在此以其他方式描述的任何过程或方法描述可以被理解为，表示包括一个或更多个用于实现特定逻辑功能或过程的步骤的可执行指令的 代码的模块、片段或部分，并且本申请的优选实施方式的范围包括另外的实现，其中可以不按所示出或讨论的顺序，包括根据所涉及的功能按基本同时的方式或按相反的顺序，来执行功能，这应被本申请的实施例所属技术领域的技术人员所理解。Any process or method description in the flowchart or otherwise described herein can be understood to represent an executable instruction that includes one or more steps for implementing a particular logical function or process. Modules, segments or portions of code, and the scope of the preferred embodiments of the application includes additional implementations, which may not be in the order shown or discussed, including in a substantially simultaneous manner or in reverse order depending on the functionality involved. To perform the functions, this should be understood by those skilled in the art to which the embodiments of the present application pertain.
应当理解，本申请的各部分可以用硬件、软件、固件或它们的组合来实现。在上述实施方式中，多个步骤或方法可以用存储在存储器中且由合适的指令执行***执行的软件或固件来实现。例如，如果用硬件来实现，和在另一实施方式中一样，可用本领域公知的下列技术中的任一项或他们的组合来实现：具有用于对数据信号实现逻辑功能的逻辑门电路的离散逻辑电路，具有合适的组合逻辑门电路的专用集成电路，可编程门阵列(PGA)，现场可编程门阵列(FPGA)等。It should be understood that portions of the application can be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques well known in the art: having logic gates for implementing logic functions on data signals. Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.
本技术领域的普通技术人员可以理解实现上述实施例方法携带的全部或部分步骤是可以通过程序来指令相关的硬件完成，所述的程序可以存储于一种计算机可读存储介质中，该程序在执行时，包括方法实施例的步骤之一或其组合。One of ordinary skill in the art can understand that all or part of the steps carried by the method of implementing the above embodiments can be completed by a program to instruct related hardware, and the program can be stored in a computer readable storage medium. When executed, one or a combination of the steps of the method embodiments is included.
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不一定指的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施例或示例中以合适的方式结合。In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means a specific feature described in connection with the embodiment or example. A structure, material or feature is included in at least one embodiment or example of the application. In the present specification, the schematic representation of the above terms does not necessarily mean the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.
尽管上面已经示出和描述了本申请的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本申请的限制，本领域的普通技术人员在本申请的范围内可以对上述实施例进行变化、修改、替换和变型。 While the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are illustrative and are not to be construed as limiting the scope of the present application. The embodiments are subject to variations, modifications, substitutions and variations.

Claims (15)

  1. 一种用于三维动态磁共振成像的球形k空间采集方法，其特征在于，包括：A spherical k-space acquisition method for three-dimensional dynamic magnetic resonance imaging, comprising:
    建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采集轨迹的仰角θ与方位角
    Figure PCTCN2016104665-appb-100001
    由二维黄金分割比例计算得到；    Establishing a spherical k-space model to determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: a radius-shaped half-echo signal from the center of the sphere to the spherical surface within the sphere, or The full-echo signal of the diameter of the passing sphere, the elevation angle θ and the azimuth of the echo signal acquisition trajectory
    Figure PCTCN2016104665-appb-100001
    Calculated from the two-dimensional golden ratio;
    根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；Determining a time series of the magnetic resonance scan according to the collected trajectory, and calculating a coding gradient of the applied magnetic field required by the magnetic resonance imaging system;
    根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。A magnetic resonance imaging system is arranged according to the time series and the coding gradient, and k-space data corresponding to the acquisition trajectory is acquired to fill the spherical k-space.
  2. 根据权利要求1所述的方法，其特征在于，所述回波信号的采集轨迹的计算方法，包括以下步骤：The method according to claim 1, wherein the method for calculating the acquisition trajectory of the echo signal comprises the following steps:
    1)设第n次采集的回波信号在球坐标系下对应的参数为：仰角θn与方位角
    Figure PCTCN2016104665-appb-100002
    初始回波的编号为n＝n0；    1) Let the corresponding parameters of the echo signal acquired in the nth time in the spherical coordinate system be: elevation angle θ n and azimuth angle
    Figure PCTCN2016104665-appb-100002
    The initial echo number is n=n 0 ;
    2)根据二维黄金分割比例系数，计算第n次采集的回波信号的仰角θn与方位角
    Figure PCTCN2016104665-appb-100003
    2) Calculate the elevation angle θ n and azimuth of the echo signal acquired for the nth time according to the two-dimensional golden section scale factor
    Figure PCTCN2016104665-appb-100003
    3)根据θn和
    Figure PCTCN2016104665-appb-100004
    计算第n次采集的回波信号上的各个采集点在笛卡尔坐标系下的坐标xn,yn,zn；    3) According to θ n and
    Figure PCTCN2016104665-appb-100004
    Calculating the coordinates x n , y n , z n of the respective acquisition points on the echo signal acquired in the nth time in a Cartesian coordinate system;
    4)根据预设的截止条件判断采集是否结束，即第n次采集的回波信号是否为采集的最后一条回波信号；4) judging whether the acquisition is finished according to a preset cutoff condition, that is, whether the echo signal acquired in the nth time is the last echo signal collected;
    5)若是，则采集结束，否则使n＝n+1，重复1)到4)直至采集结束。5) If yes, the acquisition ends, otherwise let n=n+1, repeat 1) to 4) until the end of the acquisition.
  3. 根据权利要求2所述的方法，其特征在于，所述二维黄金分割比例系数为γ1和γ2，γ1≈0.6823，γ2≈0.4656；所述回波信号的仰角θ依据γ1计算，方向角
    Figure PCTCN2016104665-appb-100005
    依据γ2计算，或者，仰角θ依据γ2计算，方向角
    Figure PCTCN2016104665-appb-100006
    依据γ1计算。     The method according to claim 2, wherein said two-dimensional golden section scale coefficients are γ 1 and γ 2 , γ 1 ≈ 0.6823, γ 2 ≈ 0.4656; and an elevation angle θ of said echo signal is calculated according to γ 1 Direction angle
    Figure PCTCN2016104665-appb-100005
    Calculated according to γ 2 , or, the elevation angle θ is calculated according to γ 2 , the direction angle
    Figure PCTCN2016104665-appb-100006
    Calculated according to γ 1 .
  4. 根据权利要求3所述的方法，其特征在于，当所述回波信号是由球心出发的半回波信号时，通过下式计算其仰角和方位角：The method according to claim 3, wherein when the echo signal is a half-echo signal originating from a center of the sphere, the elevation angle and the azimuth angle are calculated by:
    θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
    Figure PCTCN2016104665-appb-100007
    Figure PCTCN2016104665-appb-100007
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  5. 根据权利要求3所述的方法，其特征在于，当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：The method according to claim 3, wherein when the echo signal is a full-echo signal of a diameter, the elevation angle and the azimuth angle are calculated by:
    θn＝arccos(mod(n·γ1,1))θ n =arccos(mod(n·γ 1 ,1))
    Figure PCTCN2016104665-appb-100008
    Figure PCTCN2016104665-appb-100008
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  6. 根据权利要求3所述的方法，其特征在于，当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：The method according to claim 3, wherein when the echo signal is a full-echo signal of a diameter, the elevation angle and the azimuth angle are calculated by:
    θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
    Figure PCTCN2016104665-appb-100009
    Figure PCTCN2016104665-appb-100009
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  7. 根据权利要求2所述的方法，其特征在于，所述初始回波的编号n0为任意自然数。The method according to claim 2, wherein the number n 0 of the initial echo is an arbitrary natural number.
  8. 根据权利要求2所述的方法，其特征在于，所述计算磁共振成像***所需施加磁场的编码梯度，进一步包括：The method according to claim 2, wherein said calculating a coding gradient of a magnetic field to be applied by the magnetic resonance imaging system further comprises:
    根据第n次采集轨迹上的各个采集点在笛卡尔坐标系下的坐标xn,yn,zn计算第n次采集时所需施加的三个方向磁场的编码梯度。The coding gradient of the three directional magnetic fields to be applied at the nth acquisition is calculated according to the coordinates x n , y n , z n of the respective acquisition points on the nth acquisition trajectory in the Cartesian coordinate system.
  9. 一种适用于三维动态磁共振成像的球形k空间采集装置，其特征在于，包括：A spherical k-space acquisition device suitable for three-dimensional dynamic magnetic resonance imaging, comprising:
    建模模块，用于建立球形的k空间模型，确定模型中回波信号的采集轨迹，其中，所述回波信号的采集轨迹为：在所述球形内，采集由球心到球面的半径状的半回波信号，或者，过球心的直径状的全回波信号，回波信号采 集轨迹的仰角与方位角由二维黄金分割比例计算得到；a modeling module, configured to establish a spherical k-space model, and determine a trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: within the spherical shape, collecting a radius from the center of the sphere to the spherical surface The half-echo signal, or the full-echo signal of the diameter of the passing center, the echo signal The elevation and azimuth of the set trajectory are calculated from the two-dimensional golden ratio;
    计算模块，用于根据所述采集轨迹确定磁共振扫描的时间序列，并计算磁共振成像***所需施加磁场的编码梯度；a calculation module, configured to determine a time series of the magnetic resonance scan according to the collected trajectory, and calculate a coding gradient of an applied magnetic field required by the magnetic resonance imaging system;
    采集模块，用于根据所述时间序列和编码梯度设置磁共振成像***，并采集符合所述采集轨迹的k空间数据填充所述球形k空间。And an acquisition module, configured to set a magnetic resonance imaging system according to the time series and the coding gradient, and acquire k-space data conforming to the collected trajectory to fill the spherical k-space.
  10. 根据权利要求9所述的装置，其特征在于，所述建模模块具体用于通过以下步骤确定回波信号的采集轨迹：The apparatus according to claim 9, wherein the modeling module is specifically configured to determine an acquisition trajectory of the echo signal by the following steps:
    1)设第n次采集的回波信号在球坐标系下对应的参数为：仰角θn与方位角
    Figure PCTCN2016104665-appb-100010
    初始回波的编号为n＝n0；    1) Let the corresponding parameters of the echo signal acquired in the nth time in the spherical coordinate system be: elevation angle θ n and azimuth angle
    Figure PCTCN2016104665-appb-100010
    The initial echo number is n=n 0 ;
    2)根据二维黄金分割比例系数，计算第n次采集的回波信号的仰角θn与方位角
    Figure PCTCN2016104665-appb-100011
    2) Calculate the elevation angle θ n and azimuth of the echo signal acquired for the nth time according to the two-dimensional golden section scale factor
    Figure PCTCN2016104665-appb-100011
    3)根据θn和
    Figure PCTCN2016104665-appb-100012
    计算第n次采集的回波信号上的各个采集点在笛卡尔坐标系下的坐标xn,yn,zn；    3) According to θ n and
    Figure PCTCN2016104665-appb-100012
    Calculating the coordinates x n , y n , z n of the respective acquisition points on the echo signal acquired in the nth time in a Cartesian coordinate system;
    4)根据预设的截止条件判断采集是否结束，即第n次采集的回波信号是否为采集的最后一条回波信号；4) judging whether the acquisition is finished according to a preset cutoff condition, that is, whether the echo signal acquired in the nth time is the last echo signal collected;
    5)若是，则采集结束，否则使n＝n+1，重复1)到4)直至采集结束。5) If yes, the acquisition ends, otherwise let n=n+1, repeat 1) to 4) until the end of the acquisition.
  11. 根据权利要求9所述的装置，其特征在于，所述二维黄金分割比例系数为γ1和γ2，γ1≈0.6823，γ2≈0.4656；所述回波信号的仰角θ依据γ1计算，方向角
    Figure PCTCN2016104665-appb-100013
    依据γ2计算，或者，仰角θ依据γ2计算，方向角
    Figure PCTCN2016104665-appb-100014
    依据γ1计算。    The apparatus according to claim 9, wherein said two-dimensional golden section scale coefficients are γ 1 and γ 2 , γ 1 ≈ 0.6823, γ 2 ≈ 0.4656; and an elevation angle θ of said echo signal is calculated according to γ 1 Direction angle
    Figure PCTCN2016104665-appb-100013
    Calculated according to γ 2 , or, the elevation angle θ is calculated according to γ 2 , the direction angle
    Figure PCTCN2016104665-appb-100014
    Calculated according to γ 1 .
  12. 根据权利要求11所述的装置，其特征在于，所述建模模块包括：The apparatus of claim 11 wherein said modeling module comprises:
    第一计算单元，用于当所述回波信号是由球心出发的半回波信号时，通过下式计算其仰角和方位角：a first calculating unit, configured to calculate an elevation angle and an azimuth angle by the following formula when the echo signal is a half echo signal originating from a center of the sphere:
    θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
    Figure PCTCN2016104665-appb-100015
    Figure PCTCN2016104665-appb-100015
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。 Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  13. 根据权利要求11所述的装置，其特征在于，所述建模模块还包括：The apparatus according to claim 11, wherein the modeling module further comprises:
    第二计算单元，用于当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：a second calculating unit, configured to calculate an elevation angle and an azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
    θn＝arccos(mod(n·γ1,1))θ n =arccos(mod(n·γ 1 ,1))
    Figure PCTCN2016104665-appb-100016
    Figure PCTCN2016104665-appb-100016
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  14. 根据权利要求11所述的装置，其特征在于，所述建模模块还包括：The apparatus according to claim 11, wherein the modeling module further comprises:
    第三计算单元，用于当所述回波信号是直径状的全回波信号时，通过下式计算其仰角和方位角：a third calculating unit, configured to calculate an elevation angle and an azimuth angle by the following formula when the echo signal is a full-echo signal of a diameter:
    θn＝arccos(2mod(n·γ1,1)-1)θ n =arccos(2mod(n·γ 1 ,1)-1)
    Figure PCTCN2016104665-appb-100017
    Figure PCTCN2016104665-appb-100017
    其中，arccos(i)为求i的反余弦值，mod(a,b)为求a/b的余数。Among them, arccos(i) is the inverse cosine of i, and mod(a,b) is the remainder of a/b.
  15. 根据权利要求10所述的装置，其特征在于，所述初始回波的编号n0为任意自然数。 The apparatus according to claim 10, wherein said initial echo number n 0 is an arbitrary natural number.
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