WO2018082028A1 - Cartesian k-space collection method and system for three-dimensional dynamic magnetic resonance imaging - Google Patents
Cartesian k-space collection method and system for three-dimensional dynamic magnetic resonance imaging Download PDFInfo
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- the present application relates to the field of three-dimensional dynamic magnetic resonance imaging technology, and in particular, to a Cartesian k-space acquisition method and system 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.
- Three-dimensional 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 on 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 can be obtained with time. By performing data analysis on the dynamic images, a series of biological processes that reflect the occurrence and development of lesions can be obtained. Quantitative or semi-quantitative parameters of pathophysiological information are of great value for both research and diagnosis.
- Dynamic magnetic resonance imaging has been widely used in fields such as Cardiac Cine MRI, Dynamic Contrast Enhanced MRI (DCE-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.
- To the k space The data 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 uniform distribution of k-space data, 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. Sexuality is still limited by a certain dimension coding scheme. The temporal resolution of dynamic imaging is difficult to improve.
- an object of the present application is to provide a Cartesian k-space acquisition method and system suitable for three-dimensional dynamic magnetic resonance imaging, which can realize continuous acquisition of three-dimensional k-space data, so that the collected The k-space data is approximately evenly distributed in any time window, improving the temporal resolution of 3D dynamic magnetic resonance imaging and avoiding the influence of streak artifacts in the reconstructed image.
- a Cartesian k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging includes: establishing a k-space model in a three-dimensional Cartesian coordinate system, and determining The acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and the coordinates of each echo signal in a plane formed by the other two coordinate directions are Calculating 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; setting the magnetic resonance imaging system according to the time series and the coding gradient, and Acquiring k-space data that conforms to the acquisition trajectory.
- a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging includes: a modeling module for establishing a k-space model in a three-dimensional Cartesian coordinate system, and determining a model back The acquisition trajectory of the wave signal, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and the coordinates of each echo signal in the plane formed by the other two coordinate directions are determined by two-dimensional gold.
- a calculation module for 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 an acquisition module for calculating the time series and the coding gradient according to the time series
- a magnetic resonance imaging system is provided and k-space data conforming to the acquisition trajectory is acquired.
- the technical solution provided by the embodiment of the present application can collect uniform k-space data, thereby improving the time resolution of dynamic imaging, and the specific advantages are as follows:
- reconstruction speed can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
- FIG. 1 is a schematic flow chart of a Cartesian 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 flow chart of determining coordinates of a Cartesian k-space acquisition echo according to an embodiment of the present application
- FIG. 3 is a schematic flow chart of determining coordinates of a Cartesian k-space data acquisition echo according to another embodiment of the present application.
- FIG. 4 is a schematic diagram of data distribution of a Cartesian k-space collected in an embodiment of the present application
- FIG. 5 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. 6 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. 7 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
- FIG. 8 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application;
- FIG. 9 is an apparatus according to an embodiment of the present invention.
- Embodiments of the present application provide a Cartesian k-space acquisition method and apparatus for three-dimensional dynamic magnetic resonance imaging.
- FIG. 1 is a schematic flow chart of a Cartesian 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 k-space model in a three-dimensional Cartesian coordinate system, and determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, each The coordinates of the echo signal in the plane formed by the other two coordinate directions are calculated from 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 conforms to the collected trajectory.
- the three-dimensional k-space collected in this embodiment is a cube as a whole.
- the acquisition trajectory of the echo signal is: all echo signals are collected in parallel along one coordinate direction, and the coordinates of each echo signal in the plane formed by the other two coordinate directions are divided by two-dimensional golden ratio. It is calculated that the filling of the three-dimensional Cartesian k-space is finally realized by collecting the echo signals conforming to the above trajectory.
- the embodiment of the present application can adapt to the existing image reconstruction technology, avoid the influence of the stripe artifact, and the reconstruction is simple. Since the echo signals are collected in the same direction, the position of the echo signal can be determined by collecting the coordinates in the vertical plane of the direction. The acquisition position is calculated according to the two-dimensional golden ratio, which can make the collected k-space data more uniform and reconstruct a continuous three-dimensional dynamic image with high time resolution.
- the corresponding phase encoding and layer selection encoding may be calculated according to the two-dimensional golden section scaling coefficient.
- the two-dimensional golden section scale coefficients are GR 1 and GR 2 , which are obtained from the eigenvectors of the generalized Fibonacci sequence. After taking the four digits after the decimal point, GR1 ⁇ 0.4656, GR2 ⁇ 0.6823.
- the basic steps for calculating the 2D golden section scale factor are as follows:
- embodiments of the present invention are capable of providing an approximately uniform k-space distribution over any time window. This is beneficial to improve the temporal resolution of dynamic imaging and the freedom of k-space data selection during image reconstruction.
- high temporal resolution can provide more accurate physiological processes of tissue and organ, which will help to further study and diagnose the disease.
- the acquisition trajectory of the echo signal is calculated by the following steps:
- y i and z i respectively correspond to GR1, GR2, and in one embodiment of the present application, plane coordinates (y i , z i ) can be calculated according to the following formula:
- mod(a,b) is the remainder of a/b.
- the obtained yi and zi are used to set the position of the echo acquired in the i-th time in the k-space yOz plane.
- the preset cutoff condition is manually set, for example, the acquisition time is 20 minutes, or 100,000 echo signals are collected.
- the number i 0 of the initial echo acquired by the echo may be an arbitrary natural number, and the echo signal may be collected from an acquisition track at an arbitrary position to fill the k space.
- the plane coordinate (y i , z i ) may also be calculated according to the two-dimensional golden section scale coefficient by another method: assigning the calculated value of (y i , z i ) to The nearest integer grid point in the plane; the coordinates of the integer grid point are checked in a preset range; when the same coordinates are not present, the coordinates of the integer grid point are collected as the back The plane coordinate of the wave signal; if the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor. It is also possible to pre-store the plane coordinates of the echo signals calculated each time into an array; the array is called to determine the acquisition trajectory of the echo signals when the k-space data is acquired. As shown in Figure 3, the process of confirming the acquisition trajectory is as follows:
- the calculated y i and z i are assigned to integer grid points in the corresponding nearest k-space plane. If the coordinates of the grid point exist within the set continuous time window, the next two-dimensional coordinate value is continuously calculated according to the two-dimensional golden ratio until the coordinate value of the obtained integer grid point is in the set continuous time window. Does not exist inside, and then sets the coordinate value to the plane coordinate of the acquired echo.
- the set continuous time window corresponds to the k-space resolution
- the array M can be pre-calculated according to the set k-space resolution.
- the coordinate values in M can be called in order to determine the position of the phase encoding and the layer selection code corresponding to the echo acquired each time. It is worth noting that M only needs to store the former (Res y ⁇ Res z ) values, and the subsequent acquisition loop calls M.
- the calculation method of M is similar to the above method, and can be implemented by programming means, and will not be described herein.
- the magnetic resonance imaging system uses a corresponding physical gradient magnetic field in all three coordinate directions of x, y, and z. Calculating the coding gradient of the applied magnetic field required by the magnetic resonance imaging system, and calculating the coding gradient of the three directional magnetic fields to be applied in the ith acquisition according to the coordinates x i , y i , z i of the respective acquisition points on the i-th acquisition trajectory .
- the relationship between the coding gradients G x, y, z applied to the i-th acquisition and x i , y i , z i 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 i-th acquisition trajectory in k-space, corresponding to x i , y i and z i ;
- ⁇ is the gyromagnetic ratio, and
- t is the time applied by the gradient.
- a continuous three-dimensional dynamic image can be reconstructed by processing the k-space data.
- the embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional Cartesian k-space, and the under-sampling reconstruction technology can realize dynamic magnetic resonance image reconstruction with high time resolution, and can realize continuous motion. Or 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.
- FIG. 4 is two kinds of k spaces acquired by using the method of the embodiment of the present invention in the yOz plane.
- the steps 1) to 4) are referred to as method 1, and the steps 201)-207) are referred to as method 2, and the two columns (a) and (b) in FIG. 4 are successively collected using method 1 and method 2, respectively.
- the average distance of each point from all 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 each point.
- the neighborhood of each point is a circle with a radius of R centered on that point, and R is determined by: Where T is the total number of acquisitions, and Res y and Res z are the resolutions in the y and z directions, that is, the number of codes. Fig.
- FIG. 5 is a three selection mode of k-space data in dynamic magnetic resonance image reconstruction, wherein (a) is a different continuous acquisition times, that is, time windows of different lengths, (b) is a time window of different positions, and (c) is A combination of different time windows.
- Figure 6 shows the k-space data distribution uniformity comparison in different time window selection modes, including different acquisition times (a), different time window positions (b), and different time window combinations (c). Under the condition, the average distance value standard deviation of the Cartesian k-space data collected by the two methods is compared, and the number of acquisitions of (b) and (c) is 5000.
- the k-space data collected by the acquisition method proposed by the embodiment of the present invention has good uniformity in the Cartesian k-space, and the two methods proposed by the present invention are in three different k-spaces.
- the statistical standard deviation in the data selection mode is very small, close to 0, which proves that the k-space data obtained by the method of the present invention has better spatial uniformity.
- Cartesian k-space acquisition method of the embodiment of the present invention has the following advantages:
- reconstruction speed can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
- the embodiment of the present application further provides a Cartesian k-space acquisition system 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.
- the Cartesian k-space acquisition system for 3D dynamic magnetic resonance imaging solves the problem similarly to the Cartesian k-space acquisition method for 3D dynamic magnetic resonance imaging, so it is suitable for Cartesian k-space acquisition of 3D dynamic magnetic resonance imaging.
- the implementation of the system can be seen in the implementation of the Cartesian k-space acquisition method applicable to three-dimensional dynamic magnetic resonance imaging, and the repetition will not be repeated.
- 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. 7 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application.
- the system of 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 Cartesian k-space acquisition system 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 k-space model in a three-dimensional Cartesian coordinate system, and determine a collection trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals along a coordinate The directions are collected in parallel, and the coordinates of each echo signal in the plane formed by the other two coordinate directions are calculated by the two-dimensional golden ratio.
- the calculation 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 the 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 that conforms to the collected trajectory.
- FIG. 8 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application.
- the modeling module 10 further includes a computing unit 11, a meshing unit 12, a de-weighting unit 13, and a storage unit 14.
- 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 ratio coefficient is GR1, GR2, GR1 ⁇ 0.4656, and GR2 ⁇ 0.6823; the coordinates of the echo signal in two directions in the vertical plane correspond to GR1 and GR2, respectively.
- the number i0 of the initial echo may be any natural number.
- the modeling module 10 further includes a computing unit 11 that calculates the echo signal in a vertical plane yOz by the following equation when the resolution of the three-dimensional k-space is Res x ⁇ Res y ⁇ Res z and the echo signal is acquired along the x-axis direction
- mod(a,b) is the remainder of a/b.
- the meshing unit 12 is configured to assign the calculated value of (y i , z i ) to the nearest integer grid point in the plane.
- the de-weighting unit 13 is configured to check the coordinates of the integer grid points within a preset range. If the same coordinates are not present, the coordinates of the integer grid points are used as plane coordinates for acquiring the echo signals; If the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor.
- the storage unit 14 is configured to store in advance the plane coordinates of the echo signal calculated each time.
- the acquisition module 30 is further configured to call coordinates in the storage unit when acquiring k-space data to determine a collection trajectory of the echo signal.
- 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:
- reconstruction speed can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
- Embodiments of the present invention also provide a computer readable storage medium including computer readable instructions that, when executed, cause a processor to perform at least the following operations: establishing a k-space model in a three-dimensional Cartesian coordinate system, Determining an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and coordinates of each echo signal in a plane formed by the other two coordinate directions 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 that conforms to the collected trajectory.
- the embodiment of the present invention further provides an apparatus.
- the apparatus includes: a processor 901 and a memory 902 including computer readable instructions that, when executed, cause the processor to perform the following operations:
- the k-space model in the three-dimensional Cartesian coordinate system determines the acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and each echo signal is The coordinates in the plane formed by the other two coordinate directions are calculated by the two-dimensional golden ratio; 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; The time series and the coding gradient set up the magnetic resonance imaging system and acquire k-space data that conforms to the acquired trajectory.
- the embodiments of the present application can realize that the data collected in any time window is approximately evenly distributed in the three-dimensional Cartesian k-space, and the under-sampling reconstruction technology can realize dynamic magnetic resonance image reconstruction with high time resolution, and can realize continuous motion. Or dynamic imaging.
- 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 circuit ASICs with suitable combinational logic gates Programmable Gate Arrays (PGAs), Field Programmable Gate Arrays (FPGAs), etc.
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Abstract
Proposed are a Cartesian k-space collection method and system for three-dimensional dynamic magnetic resonance imaging. The method comprises: establishing a k-space model in a three-dimensional Cartesian coordinate system and determining a collection track of an echo signal in the model, wherein the collection track of the echo signal is: collecting all the echo signals along one coordinate direction in parallel, and the coordinates of each of the echo signals in a plane formed by the other two coordinate directions being obtained by the two-dimensional golden section ratio; determining, according to the collection track, a scanning time sequence and an encoding gradient required to apply a magnetic field by a magnetic resonance imaging system; setting the magnetic resonance imaging system according to the time sequence and the encoding gradient, and collecting k-space data conforming to the collection track. 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 preventing streak artifacts from being generated in image reconstruction and achieving high-temporal-resolution three-dimensional dynamic magnetic resonance imaging.
Description
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笛卡尔k空间采集方法和***。The present application relates to the field of three-dimensional dynamic magnetic resonance imaging technology, and in particular, to a Cartesian k-space acquisition method and system for three-dimensional dynamic magnetic resonance imaging.
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。三维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,对研究和诊断都有重要价值。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. Three-dimensional 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 on 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 can be obtained with time. By performing data analysis on the dynamic images, a series of biological processes that reflect the occurrence and development of lesions can be obtained. Quantitative or semi-quantitative parameters of pathophysiological information are of great value for both research and diagnosis. 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. To the k space
The data 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,由于采用了径向采集方式,因此在重建图像中容易受到条纹伪影的影响,尤其是在欠采样重建中。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 uniform distribution of k-space data, 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. Sexuality is still limited by a certain dimension coding scheme. The temporal resolution of dynamic imaging is difficult to improve. In addition, due to the radial acquisition method, it is easy to be affected by streak artifacts in reconstructed images, especially in under-sampling reconstruction. . 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笛卡尔k空间采集方法及***,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,提高三维动态磁共振成像的时间分辨率,并避免在重建图像中受到条纹伪影的影响。In order to solve the above problems in the prior art, an object of the present application is to provide a Cartesian k-space acquisition method and system suitable for three-dimensional dynamic magnetic resonance imaging, which can realize continuous acquisition of three-dimensional k-space data, so that the collected The k-space data is approximately evenly distributed in any time window, improving the temporal resolution of 3D dynamic magnetic resonance imaging and avoiding the influence of streak artifacts in the reconstructed image.
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笛卡尔k空间采集方法,包括:建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标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。In order to achieve the above object, a Cartesian k-space acquisition method suitable for three-dimensional dynamic magnetic resonance imaging proposed by the embodiments of the present application includes: establishing a k-space model in a three-dimensional Cartesian coordinate system, and determining
The acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and the coordinates of each echo signal in a plane formed by the other two coordinate directions are Calculating 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; setting the magnetic resonance imaging system according to the time series and the coding gradient, and Acquiring k-space data that conforms to the acquisition trajectory.
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笛卡尔k空间采集***,包括:建模模块,用于建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标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。To achieve the above objective, a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging proposed by the embodiment of the present application includes: a modeling module for establishing a k-space model in a three-dimensional Cartesian coordinate system, and determining a model back The acquisition trajectory of the wave signal, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and the coordinates of each echo signal in the plane formed by the other two coordinate directions are determined by two-dimensional gold. a calculation module for 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 an acquisition module for calculating the time series and the coding gradient according to the time series A magnetic resonance imaging system is provided and k-space data conforming to the acquisition trajectory is acquired.
本申请实施例提供的技术方案,能够采集均匀的k空间数据,进而提高动态成像的时间分辨率,具体优点如下:The technical solution provided by the embodiment of the present application can collect uniform k-space data, thereby improving the time resolution of dynamic 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,在笛卡尔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,并避免在重建图像中受到条纹伪影的影响。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 Cartesian 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, and the influence of streak artifacts in the reconstructed image is avoided.
2、重建速度:能够适用于常见的重建方法,重建简单,并能够使计算得到的采集坐标能够对应笛卡尔网格点,重建速度更快。2, reconstruction speed: can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
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.
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笛卡尔k空间采集方法的流程示意图;1 is a schematic flow chart of a Cartesian 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确定笛卡尔k空间采集回波坐标的流程示意图;2 is a schematic flow chart of determining coordinates of a Cartesian k-space acquisition echo according to an embodiment of the present application;
图3是本申请另一实施例的确定笛卡尔k空间数据采集回波坐标的流程示意图;3 is a schematic flow chart of determining coordinates of a Cartesian k-space data acquisition echo according to another embodiment of the present application;
图4是本申请一实施例采集到的笛卡尔k空间的数据分布情况示意图;4 is a schematic diagram of data distribution of a Cartesian k-space collected in an embodiment of the present application;
图5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;5 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6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;6 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7是本申请一实施例的适用于三维动态磁共振成像的笛卡尔k空间采集***的结构示意图;7 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application;
图8是本申请另一实施例的适用于三维动态磁共振成像的笛卡尔k空间采集***的结构示意图;8 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application;
图9是本发明实施例提供的一种设备。FIG. 9 is an apparatus according to an embodiment of the present invention.
本申请实施例提供一种用于三维动态磁共振成像的笛卡尔k空间采集方法和装置。Embodiments of the present application provide a Cartesian 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笛卡尔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 Cartesian 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,建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标由二维黄金分割比例计算得到。Step 101: Establish a k-space model in a three-dimensional Cartesian coordinate system, and determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, each The coordinates of the echo signal in the plane formed by the other two coordinate directions are calculated from 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。Step 103: Set a magnetic resonance imaging system according to the time series and the encoding gradient, and collect k-space data that conforms to the collected trajectory.
具体地,本实施例采集的三维k空间整体是一个立方体。在三维笛卡尔k空间中,回波信号的采集轨迹为:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标由二维黄金分割比例计算得到,通过采集符合上述轨迹的回波信号最终实现对三维笛卡尔k空间的填充。Specifically, the three-dimensional k-space collected in this embodiment is a cube as a whole. In the three-dimensional Cartesian k-space, the acquisition trajectory of the echo signal is: all echo signals are collected in parallel along one coordinate direction, and the coordinates of each echo signal in the plane formed by the other two coordinate directions are divided by two-dimensional golden ratio. It is calculated that the filling of the three-dimensional Cartesian k-space is finally realized by collecting the echo signals conforming to the above trajectory.
本申请实施例由于三维笛卡尔k空间不采用径向采集方式,能够适应现有的图像重建技术,避免条纹伪影的影响,且重建简单。由于回波信号沿同方向采集,通过采集方向垂直平面内的坐标即可确定回波信号的位置,平面
内的采集位置根据二维黄金分割比例计算得出,可以使采集到的k空间数据更均匀,重建得到高时间分辨率的连续三维动态图像。Since the three-dimensional Cartesian k-space does not adopt the radial acquisition mode, the embodiment of the present application can adapt to the existing image reconstruction technology, avoid the influence of the stripe artifact, and the reconstruction is simple. Since the echo signals are collected in the same direction, the position of the echo signal can be determined by collecting the coordinates in the vertical plane of the direction.
The acquisition position is calculated according to the two-dimensional golden ratio, which can make the collected k-space data more uniform and reconstruct a continuous three-dimensional dynamic image with high time resolution.
下面将以频率编码方向沿x轴方向,相位编码方向沿y轴方向,选层编码方向沿z轴方向为例对本申请的实施例进行阐述。实际应用中这三个编码方向与坐标轴的对应关系可以根据需要调整,但都属于本专利的保护范围。Hereinafter, an embodiment of the present application will be described by taking the frequency encoding direction along the x-axis direction, the phase encoding direction along the y-axis direction, and the layer-coding direction along the z-axis direction as an example. In practical applications, the correspondence between the three coding directions and the coordinate axes can be adjusted as needed, but all belong to the protection scope of this patent.
根据本申请一个实施例,可以根据二维黄金分割比例系数计算对应的相位编码和选层编码。具体地,二维黄金分割比例系数为GR1和GR2,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,GR1≈0.4656,GR2≈0.6823。计算二维黄金分割比例系数的基本步骤如下:According to an embodiment of the present application, the corresponding phase encoding and layer selection encoding may be calculated according to the two-dimensional golden section scaling coefficient. Specifically, the two-dimensional golden section scale coefficients are GR 1 and GR 2 , which are obtained from the eigenvectors of the generalized Fibonacci sequence. After taking the four digits after the decimal point, GR1 ≈ 0.4656, GR2 ≈ 0.6823. The basic steps for calculating the 2D golden section scale factor are as follows:
1.求解二维斐波那契变换矩阵的特征值;1. Solving the eigenvalues of the two-dimensional Fibonacci transformation matrix;
2.求解与对应的特征矢量d;2. Solving and corresponding feature vector d;
3.取特征矢量d中非1的两个数值作为二维黄金分割比例系数GR1和GR2,GR1≈0.4656,GR2≈0.6823。3. Take two values of non-1 in the feature vector d as the two-dimensional golden section scale coefficients GR1 and GR2, GR1≈0.4656, and GR2≈0.6823.
详细的计算方法在文献[Gao S,Zhu YC,Li S,Bao SL(2014)An optimal direction strategy of diffusion sensitive gradient mangnetic fields in magnetic resonance diffusion tensor imaging based on generalized Fibonacci sequence.Acta Physica Sinica 63]中有详细介绍,在此不再赘述。The detailed calculation method is in the literature [Gao S, Zhu YC, Li S, Bao SL (2014) An optimal direction strategy of diffusion sensitive gradient mangnetic fields in magnetic resonance diffusion tensor imaging based on generalized Fibonacci sequence. Acta Physica Sinica 63] Detailed description will not be repeated here.
基于以上,本发明实施例能够在任意时间窗内提供近似均匀的k空间分布。这有利于提高动态成像的时间分辨率,以及图像重建时k空间数据选择的自由性。在动态对比度增强磁共振成像中,高时间分辨率能够提供更精确的组织器官生理代谢过程,有利于帮助对疾病的进一步研究与诊断。Based on the above, embodiments of the present invention are capable of providing an approximately uniform k-space distribution over any time window. This is beneficial to improve the temporal resolution of dynamic imaging and the freedom of k-space data selection during image reconstruction. In dynamic contrast-enhanced magnetic resonance imaging, high temporal resolution can provide more accurate physiological processes of tissue and organ, which will help to further study and diagnose the disease.
假设k空间的分辨率为:Resx×Resy×Resz,其中Resx,Resy,Resz分别表示x,y,z方向的编码数。由于回波信号沿同方向采集,通过采集方向垂直平面内的坐标即可确定回波信号的位置,因此每次采集回波的位置均可由平面坐标中y、z两个参数确定。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y和z这两个参数。下面介绍本申请实施例的两种相位编码和选层编码在k空间中yOz平面上对应位置的计算方法。It is assumed that the resolution of k-space is: Res x × Res y × Res z , where Res x , Res y , Res z represent the number of codes in the x, y, and z directions, respectively. Since the echo signals are collected in the same direction, the position of the echo signal can be determined by collecting the coordinates in the vertical plane. Therefore, the position of each echo can be determined by the two parameters y and z in the plane coordinates. Therefore, if you want to achieve high time resolution of 3D k-space acquisition, you only need to optimize the two parameters y and z. The calculation method of the corresponding positions of the two phase codes and the layer selection codes in the k-space yOz plane in the embodiment of the present application is described below.
根据本申请的一个实施例,如图2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. 2, the acquisition trajectory of the echo signal is calculated by the following steps:
1)设第i次采集的回波信号在与之垂直平面内的平面坐标为(yi,zi),初始回波的编号为i=i0。1) Let the plane coordinate of the echo signal acquired in the i-th time in the plane perpendicular to it be (y i , z i ), and the initial echo number is i=i 0 .
2)根据二维黄金分割比例系数计算所述平面坐标(yi,zi)。2) Calculate the plane coordinates (y i , z i ) according to the two-dimensional golden section scale factor.
具体地,yi和zi分别与GR1,GR2对应,在本申请一个实施例中可根据下式计算平面坐标(yi,zi):Specifically, y i and z i respectively correspond to GR1, GR2, and in one embodiment of the present application, plane coordinates (y i , z i ) can be calculated according to the following formula:
yi=mod(i×GR1,1)×Resy,zi=mod(i×GR2,1)×Resz
y i = mod(i × GR 1 , 1) × Res y , z i = mod(i × GR 2 , 1) × Res z
或者,or,
yi=mod(i×GR2,1)×Resy,zi=mod(i×GR1,1)×Resz
y i = mod(i × GR 2 , 1) × Res y , z i = mod(i × GR 1 , 1) × Res z
其中,mod(a,b)为求a/b的余数。Among them, mod(a,b) is the remainder of a/b.
得到的yi和zi用于设定第i次采集的回波在k空间yOz平面内的位置。The obtained yi and zi are used to set the position of the echo acquired in the i-th time in the k-space yOz plane.
3)根据预设截止条件判断采集是否结束,即第i次采集的回波信号是否为采集的最后一条回波信号。3) According to the preset cutoff condition, it is judged whether the acquisition is finished, that is, whether the echo signal acquired by the i th 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.
4)若是,则采集结束,否则使i=i+1,重复1)到3)直至采集结束。4) If yes, the acquisition ends, otherwise let i=i+1, repeat 1) to 3) 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i0可以为任意自然数,能够从任意位置一条采集轨迹开始采集回波信号对k空间进行填充。According to an embodiment of the present application, the number i 0 of the initial echo acquired by the echo may be an arbitrary natural number, and the echo signal may be collected from an acquisition track at an arbitrary position to fill the k space.
在本申请的另一个实施例中,还可以通过另外一种方法根据二维黄金分割比例系数计算所述平面坐标(yi,zi):将(yi,zi)的计算值分配到该平面内最近的整数网格点上;在预设范围内对所述整数网格点的坐标进行查重;当不存
在相同坐标时,将所述整数网格点的坐标作为采集所述回波信号的平面坐标;若已存在相同坐标,则根据二维黄金分割比例系数计算平面坐标(yi+1,zi+1)。还可以将每次计算的回波信号的平面坐标预先存入数组中;在采集k空间数据时调用所述数组来确定回波信号的采集轨迹。如图3所示,确认采集轨迹的过程如下:In another embodiment of the present application, the plane coordinate (y i , z i ) may also be calculated according to the two-dimensional golden section scale coefficient by another method: assigning the calculated value of (y i , z i ) to The nearest integer grid point in the plane; the coordinates of the integer grid point are checked in a preset range; when the same coordinates are not present, the coordinates of the integer grid point are collected as the back The plane coordinate of the wave signal; if the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor. It is also possible to pre-store the plane coordinates of the echo signals calculated each time into an array; the array is called to determine the acquisition trajectory of the echo signals when the k-space data is acquired. As shown in Figure 3, the process of confirming the acquisition trajectory is as follows:
201)设定一个可以存储二维坐标的空数组M=[]。201) Set an empty array M=[] that can store two-dimensional coordinates.
202)设第i次采集的回波在k空间yOz平面内坐标为:(yi,zi)。令j=i。(初始值i=i0)202) Let the coordinates of the echo acquired in the ith time in the k-space yOz plane be: (y i , z i ). Let j=i. (Initial value i=i 0 )
203)判断i是否大于Resy×Resz。203) Determine whether i is greater than Res y × Res z .
如果是,则执行204),如果否,则执行205)。If yes, execute 204), if no, execute 205).
204)令M(i)=M(i-Resy×Resz),(yi,zi)=M(i)。进入209)。204) Let M(i)=M(i-Res y ×Res z ), (y i , z i )=M(i). Go to 209).
205)计算ry=round(mod(j×GR1,1)×Resy),rz=round(mod(j×GR2,1)×Resz)。205) Calculate r y =round(mod(j×GR 1 ,1)×Res y ), r z =round(mod(j×GR 2 ,1)×Res z ).
其中mod(a,b)为计算a/b的余数,round(c)为对c做四舍五入计算。Where mod(a,b) is the remainder of the a/b, and round(c) is the rounding of c.
206)查找M中是否存在点坐标值(ry,rz)。206) Find whether there is a point coordinate value (r y , r z ) in M.
如果不存在,执行207),如果存在,执行208)。If not, execute 207), if present, execute 208).
207)令M(i)=(ry,rz),且(yi,zi)=M(i),得到的yi和zi用于设定第i次采集的回波在k空间yOz平面内的位置。207) Let M(i)=(r y , r z ), and (y i , z i )=M(i), and obtain y i and z i for setting the echo of the ith acquisition at k The position within the space yOz plane.
208)令j=j+1。重复205)到206)。208) Let j=j+ 1. Repeat 205) to 206).
209)根据预设截止条件判断采集是否结束。209) Determine whether the acquisition ends according to the preset cutoff condition.
如果是,则结束采集,否则i=i+1,重复202)到209)直至采集结束。If yes, the acquisition is ended, otherwise i=i+1, repeat 202) to 209) until the end of the acquisition.
具体地,将计算得到的yi和zi分配到相应最近的k空间平面内的整数网格点上。如果该网格点的坐标在设定的连续时间窗内存在,则按照二维黄金分割比例继续计算下一个二维坐标值,直至得到的整数网格点的坐标值在设定的连续时间窗内不存在,然后将该坐标值设定为本次采集回波的平面坐标。优选的,设定的连续时间窗与k空间分辨率对应,数组M可以根据设
定的k空间分辨率预先计算得到。在实际扫描中每次采集回波可以按顺序调用M中的这些坐标值,确定每次采集的回波所对应的相位编码和选层编码的位置。值得注意的是,M只需存储前(Resy×Resz)个值,此后的采集循环调用M即可。M的计算方法与上述方法相近,可通过编程手段实现,在此不再赘述。Specifically, the calculated y i and z i are assigned to integer grid points in the corresponding nearest k-space plane. If the coordinates of the grid point exist within the set continuous time window, the next two-dimensional coordinate value is continuously calculated according to the two-dimensional golden ratio until the coordinate value of the obtained integer grid point is in the set continuous time window. Does not exist inside, and then sets the coordinate value to the plane coordinate of the acquired echo. Preferably, the set continuous time window corresponds to the k-space resolution, and the array M can be pre-calculated according to the set k-space resolution. Each time the echo is acquired in the actual scan, the coordinate values in M can be called in order to determine the position of the phase encoding and the layer selection code corresponding to the echo acquired each time. It is worth noting that M only needs to store the former (Res y × Res z ) values, and the subsequent acquisition loop calls M. The calculation method of M is similar to the above method, and can be implemented by programming means, and will not be described herein.
根据本申请的一个实施例,为了采集得到符合采集轨迹的k空间数据,磁共振成像***在x,y,z三个坐标方向均使用对应的物理梯度磁场。计算磁共振成像***所需施加磁场的编码梯度,可以根据第i次采集轨迹上各个采集点坐标xi,yi,zi计算第i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i次采集时所施加的编码梯度Gx,y,z与xi,yi,zi的关系可由下式描述:According to an embodiment of the present application, in order to acquire k-space data conforming to the collected trajectory, the magnetic resonance imaging system uses a corresponding physical gradient magnetic field in all three coordinate directions of x, y, and z. Calculating the coding gradient of the applied magnetic field required by the magnetic resonance imaging system, and calculating the coding gradient of the three directional magnetic fields to be applied in the ith acquisition according to the coordinates x i , y i , z i of the respective acquisition points on the i-th acquisition trajectory . The relationship between the coding gradients G x, y, z applied to the i-th acquisition and x i , y i , z i can be described by the following equation, regardless of the actual hardware conditions and the like:
其中,kx,y,z为第i次采集轨迹在k空间内的坐标,对应于xi,yi和zi;γ为旋磁比,t为梯度施加的时间。Where k x, y, z are the coordinates of the i-th acquisition trajectory in k-space, corresponding to x i , y i and z i ; γ is the gyromagnetic ratio, and t is the time applied by the gradient.
在所述根据所述编码采集相应的k空间数据之后,通过对所述k空间数据进行处理,可以重建得到连续的三维动态图像。After the corresponding k-space data is acquired according to the code, a continuous three-dimensional dynamic image can be reconstructed by processing the k-space data.
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笛卡尔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。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 Cartesian k-space, and the under-sampling reconstruction technology can realize dynamic magnetic resonance image reconstruction with high time resolution, and can realize continuous motion. Or 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.
以回波方向沿x方向、k空间分辨率为100×100×100,连续采集1000次和10000次回波为例,图4是使用本发明实施例的方法采集得到的两种k空间在yOz平面内的坐标点分布情况。将采用步骤1)-4)的记为方法1,采用步骤201)-207)的记为方法2,图4中的(a)、(b)两列分别是使用方法1和方法2连续采集1000次和10000次回波的结果。
Taking the echo direction in the x direction, k spatial resolution as 100×100×100, and continuously acquiring 1000 times and 10000 echoes as an example, FIG. 4 is two kinds of k spaces acquired by using the method of the embodiment of the present invention in the yOz plane. The distribution of coordinate points within. The steps 1) to 4) are referred to as method 1, and the steps 201)-207) are referred to as method 2, and the two columns (a) and (b) in FIG. 4 are successively collected using method 1 and method 2, respectively. The results of 1000 and 10,000 echoes.
为了评估k空间数据在yOz平面内的均匀性,可计算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所有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以该点为中心半径为R的圆域,R由下式确定:其中T为采集总次数,Resy与Resz为y和z方向的分辨率,即编码数。图5为动态磁共振图像重建中k空间数据的三种选择模式,其中(a)为不同的连续采集次数,即不同长度的时间窗,(b)为不同位置的时间窗,(c)为不同时间窗的组合。图6给出了相应不同的时间窗选择模式下的k空间数据分布均匀性对比,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(c)三种条件下两种方法采集到的笛卡尔k空间数据的平均距离值标准差对比,其中(b)和(c)的采集次数为5000。In order to evaluate the uniformity of k-space data in the yOz plane, the average distance of each point from all 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 each point. The closer the distance between all points in the neighborhood, the more uniform the distribution. The neighborhood of each point is a circle with a radius of R centered on that point, and R is determined by: Where T is the total number of acquisitions, and Res y and Res z are the resolutions in the y and z directions, that is, the number of codes. Fig. 5 is a three selection mode of k-space data in dynamic magnetic resonance image reconstruction, wherein (a) is a different continuous acquisition times, that is, time windows of different lengths, (b) is a time window of different positions, and (c) is A combination of different time windows. Figure 6 shows the k-space data distribution uniformity comparison in different time window selection modes, including different acquisition times (a), different time window positions (b), and different time window combinations (c). Under the condition, the average distance value standard deviation of the Cartesian k-space data collected by the two methods is compared, and the number of acquisitions of (b) and (c) is 5000.
由图4-6的评估结果可以看出,用本发明实施例提出的采集方法采集的k空间数据在笛卡尔k空间内均匀性很好,本发明提出的两种方法在三种不同k空间数据选择模式下的统计标准差都很小,接近于0,证明采用本发明方法得到的k空间数据具有较好的空间均匀性。It can be seen from the evaluation results of FIG. 4-6 that the k-space data collected by the acquisition method proposed by the embodiment of the present invention has good uniformity in the Cartesian k-space, and the two methods proposed by the present invention are in three different k-spaces. The statistical standard deviation in the data selection mode is very small, close to 0, which proves that the k-space data obtained by the method of the present invention has better spatial uniformity.
综上所述,本发明实施例的笛卡尔k空间采集方法具备如下优点:In summary, the Cartesian 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,在笛卡尔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,并避免在重建图像中受到条纹伪影的影响。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 Cartesian 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, and the influence of streak artifacts in the reconstructed image is avoided.
2、重建速度:能够适用于常见的重建方法,重建简单,并能够使计算得到的采集坐标能够对应笛卡尔网格点,重建速度更快。
2, reconstruction speed: can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
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笛卡尔k空间采集***,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笛卡尔k空间采集***解决问题的原理与适用于三维动态磁共振成像的笛卡尔k空间采集方法相似,因此适用于三维动态磁共振成像的笛卡尔k空间采集***的实施可以参见适用于三维动态磁共振成像的笛卡尔k空间采集方法的实施,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 Cartesian k-space acquisition system 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. The Cartesian k-space acquisition system for 3D dynamic magnetic resonance imaging solves the problem similarly to the Cartesian k-space acquisition method for 3D dynamic magnetic resonance imaging, so it is suitable for Cartesian k-space acquisition of 3D dynamic magnetic resonance imaging. The implementation of the system can be seen in the implementation of the Cartesian k-space acquisition method applicable to three-dimensional dynamic magnetic resonance imaging, and the repetition will not be repeated. 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7是本申请一实施例的适用于三维动态磁共振成像的笛卡尔k空间采集***的结构示意图。本实施例的***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7所示,该适用于三维动态磁共振成像的笛卡尔k空间采集***包括:建模模块10、计算模块20和采集模块30。FIG. 7 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to an embodiment of the present application. The system of 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. 7, the Cartesian k-space acquisition system 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用于建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标由二维黄金分割比例计算得到。Specifically, the modeling module 10 is configured to establish a k-space model in a three-dimensional Cartesian coordinate system, and determine a collection trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals along a coordinate The directions are collected in parallel, and the coordinates of each echo signal in the plane formed by the other two coordinate directions 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 calculation 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 the 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。
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 that conforms to the collected trajectory.
图8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笛卡尔k空间采集***的结构示意图。如图8所示,在图7的基础上,建模模块10还包括计算单元11、网格化单元12、去重单元13和存储单元14。FIG. 8 is a schematic structural diagram of a Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging according to another embodiment of the present application. As shown in FIG. 8, on the basis of FIG. 7, the modeling module 10 further includes a computing unit 11, a meshing unit 12, a de-weighting unit 13, and a storage unit 14.
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)设回波信号沿x轴方向采集,第i次采集的回波信号在与之垂直平面内的平面坐标为(yi,zi),初始回波的编号为i=i0;1) Set the echo signal to be collected along the x-axis direction. The plane coordinate of the echo signal acquired in the i-th time is (y i , z i ) in the plane perpendicular to it, and the initial echo number is i=i 0 ;
2)根据二维黄金分割比例系数计算平面坐标(yi,zi);2) Calculate the plane coordinates (y i , z i ) according to the two-dimensional golden section scale coefficient;
3)根据预设截止条件判断采集是否结束,即第i次采集的回波信号是否为采集的最后一条回波信号;3) judging whether the acquisition is finished according to the preset cutoff condition, that is, whether the echo signal collected by the i th is the last echo signal collected;
4)若是,则采集结束,否则使i=i+1,重复1)到3)直至采集结束。4) If yes, the acquisition ends, otherwise let i=i+1, repeat 1) to 3) until the end of the acquisition.
其中,所述二维黄金分割比例系数为GR1,GR2,GR1≈0.4656,GR2≈0.6823;所述回波信号在垂直平面内两个方向的坐标分别与GR1、GR2对应。The two-dimensional golden section ratio coefficient is GR1, GR2, GR1≈0.4656, and GR2≈0.6823; the coordinates of the echo signal in two directions in the vertical plane correspond to GR1 and GR2, respectively.
其中,所述初始回波的编号i0可以为任意自然数。The number i0 of the initial echo may be any natural number.
建模模块10还包括计算单元11,当三维k空间的分辨率为Resx×Resy×Resz,回波信号沿x轴方向采集时,通过下式计算所述回波信号在垂直平面yOz内的平面坐标(yi,zi):The modeling module 10 further includes a computing unit 11 that calculates the echo signal in a vertical plane yOz by the following equation when the resolution of the three-dimensional k-space is Res x ×Res y ×Res z and the echo signal is acquired along the x-axis direction The plane coordinates (y i , z i ) inside:
yi=mod(i×GR1,1)×Resy,zi=mod(i×GR2,1)×Resz
y i = mod(i × GR 1 , 1) × Res y , z i = mod(i × GR 2 , 1) × Res z
或者,or,
yi=mod(i×GR2,1)×Resy,zi=mod(i×GR1,1)×Resz
y i = mod(i × GR 2 , 1) × Res y , z i = mod(i × GR 1 , 1) × Res z
其中,mod(a,b)为求a/b的余数。Among them, mod(a,b) is the remainder of a/b.
网格化单元12用于将(yi,zi)的计算值分配到该平面内最近的整数网格点上。The meshing unit 12 is configured to assign the calculated value of (y i , z i ) to the nearest integer grid point in the plane.
去重单元13用于在预设范围内对所述整数网格点的坐标进行查重,若不存在相同坐标,将所述整数网格点的坐标作为采集所述回波信号的平面坐
标;若已存在相同坐标,则根据二维黄金分割比例系数计算平面坐标(yi+1,zi+1)。The de-weighting unit 13 is configured to check the coordinates of the integer grid points within a preset range. If the same coordinates are not present, the coordinates of the integer grid points are used as plane coordinates for acquiring the echo signals; If the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor.
存储单元14用于预先存储每次计算的回波信号的平面坐标。The storage unit 14 is configured to store in advance the plane coordinates of the echo signal calculated each time.
所述采集模块30还用于在采集k空间数据时调用所述存储单元中的坐标来确定回波信号的采集轨迹。The acquisition module 30 is further configured to call coordinates in the storage unit when acquiring k-space data to determine a collection trajectory of the echo signal.
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,在笛卡尔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,并避免在重建图像中受到条纹伪影的影响。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 Cartesian 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, and the influence of streak artifacts in the reconstructed image is avoided.
2、重建速度:能够适用于常见的重建方法,重建简单,并能够使计算得到的采集坐标能够对应笛卡尔网格点,重建速度更快。2, reconstruction speed: can be applied to common reconstruction methods, simple reconstruction, and can make the calculated acquisition coordinates can correspond to Cartesian grid points, the reconstruction speed is faster.
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:建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标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。
Embodiments of the present invention also provide a computer readable storage medium including computer readable instructions that, when executed, cause a processor to perform at least the following operations: establishing a k-space model in a three-dimensional Cartesian coordinate system, Determining an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and coordinates of each echo signal in a plane formed by the other two coordinate directions 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 that conforms to the collected trajectory.
本发明实施例还提供了一种设备,如图9所示,该设备包括:处理器901和包括计算机可读指令的存储器902,计算机可读指令在被执行时使处理器执行以下操作:建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标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。The embodiment of the present invention further provides an apparatus. As shown in FIG. 9, the apparatus includes: a processor 901 and a memory 902 including computer readable instructions that, when executed, cause the processor to perform the following operations: The k-space model in the three-dimensional Cartesian coordinate system determines the acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction, and each echo signal is The coordinates in the plane formed by the other two coordinate directions are calculated by the two-dimensional golden ratio; 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; The time series and the coding gradient set up the magnetic resonance imaging system and acquire k-space data that conforms to the acquired trajectory.
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笛卡尔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 Cartesian k-space, and the under-sampling reconstruction technology can realize dynamic magnetic resonance image reconstruction with high time resolution, and can realize continuous motion. 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 flowcharts or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a particular logical function or process. And the scope of the preferred embodiments of the present application includes additional implementations, in which the functions may be performed in a substantially simultaneous manner or in the reverse order depending on the functions involved, in accordance with the illustrated or discussed order. It will 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 circuit
ASICs 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)
- 一种用于三维动态磁共振成像的笛卡尔k空间采集方法,其特征在于,包括:A Cartesian k-space acquisition method for three-dimensional dynamic magnetic resonance imaging, comprising:建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标由二维黄金分割比例计算得到;The k-space model in the three-dimensional Cartesian coordinate system is established to determine the acquisition trajectory of the echo signals in the model. The trajectory of the echo signals is: all echo signals are collected in parallel along a coordinate direction, and each echo signal The coordinates in the plane formed by the other two coordinate directions are 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。A magnetic resonance imaging system is provided according to the time series and the coding gradient, and k-space data conforming to the acquisition trajectory is acquired.
- 根据权利要求1所述的方法,其特征在于,所述三维笛卡尔坐标系下的三个坐标方向分别与频率编码方向、相位编码方向、选层编码方向一一对应。The method according to claim 1, wherein the three coordinate directions in the three-dimensional Cartesian coordinate system are in one-to-one correspondence with the frequency encoding direction, the phase encoding direction, and the layer selection encoding direction, respectively.
- 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)设回波信号沿x轴频率编码方向采集,第i次采集的回波信号在与之垂直平面内的平面坐标为(yi,zi),初始回波的编号为i=i0;1) Set the echo signal to be acquired along the x-axis frequency encoding direction. The plane coordinate of the echo signal acquired in the i-th plane is (y i , z i ) in the plane perpendicular to it, and the initial echo number is i=i 0 ;2)根据二维黄金分割比例系数计算所述平面坐标(yi,zi);2) calculating the plane coordinates (y i , z i ) according to the two-dimensional golden section scale coefficient;3)根据预设截止条件判断采集是否结束,即第i次采集的回波信号是否为采集的最后一条回波信号;3) judging whether the acquisition is finished according to the preset cutoff condition, that is, whether the echo signal collected by the i th is the last echo signal collected;4)若是,则采集结束,否则使i=i+1,重复1)到3)直至采集结束。4) If yes, the acquisition ends, otherwise let i=i+1, repeat 1) to 3) until the end of the acquisition.
- 根据权利要求3所述的方法,其特征在于,所述二维黄金分割比例系数为GR1,GR2,GR1≈0.4656,GR2≈0.6823;所述回波信号在垂直平面内两个方向的坐标分别与GR1、GR2对应。The method according to claim 3, wherein the two-dimensional golden section scale coefficient is GR1, GR2, GR1 ≈ 0.4656, and GR2 ≈ 0.6823; coordinates of the echo signals in two directions in a vertical plane are respectively GR1 and GR2 correspond to each other.
- 根据权利要求4所述的方法,其特征在于,设三维k空间的分辨率 为Resx×Resy×Resz,回波信号沿x轴方向采集,则通过下式计算所述回波信号在垂直平面yOz内的平面坐标(yi,zi):The method according to claim 4, wherein the resolution of the three-dimensional k-space is Res x ×Res y ×Res z , and the echo signal is acquired along the x-axis direction, and the echo signal is calculated by the following formula Plane coordinates (y i , z i ) in the vertical plane yOz:yi=mod(i×GR1,1)×Resy,zi=mod(i×GR2,1)×Resz y i = mod(i × GR 1 , 1) × Res y , z i = mod(i × GR 2 , 1) × Res z或者,or,yi=mod(i×GR2,1)×Resy,zi=mod(i×GR1,1)×Resz y i = mod(i × GR 2 , 1) × Res y , z i = mod(i × GR 1 , 1) × Res z其中,mod(a,b)为求a/b的余数。Among them, mod(a,b) is the remainder of a/b.
- 根据权利要求3-5任一项所述的方法,其特征在于,所述根据二维黄金分割比例系数计算平面坐标(yi,zi)还包括:The method according to any one of claims 3-5, wherein the calculating the plane coordinates (y i , z i ) according to the two-dimensional golden section scale coefficient further comprises:将(yi,zi)的计算值分配到该平面内最近的整数网格点上;Assigning the calculated value of (y i , z i ) to the nearest integer grid point in the plane;在预设范围内对所述整数网格点的坐标进行查重;Checking the coordinates of the integer grid points within a preset range;当不存在相同坐标时,将所述整数网格点的坐标作为采集所述回波信号的平面坐标;When the same coordinates do not exist, the coordinates of the integer grid points are taken as plane coordinates for acquiring the echo signals;若已存在相同坐标,则根据二维黄金分割比例系数计算平面坐标(yi+1,zi+1)。If the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor.
- 根据权利要求6所述的方法,其特征在于,所述确定模型中回波信号的采集轨迹,还包括:The method according to claim 6, wherein the determining the trajectory of the echo signal in the model further comprises:将每次计算的回波信号的平面坐标预先存入数组中;The plane coordinates of the echo signal calculated each time are pre-stored in the array;在采集k空间数据时调用所述数组来确定回波信号的采集轨迹。The array is called when the k-space data is acquired to determine the acquisition trajectory of the echo signal.
- 根据权利要求3所述的方法,其特征在于,回波采集的所述初始回波的编号i0为任意自然数。The method according to claim 3, characterized in that the number i 0 of the initial echo acquired by the echo is an arbitrary natural number.
- 一种适用于三维动态磁共振成像的笛卡尔k空间采集***,其特征在于,包括:A Cartesian k-space acquisition system suitable for three-dimensional dynamic magnetic resonance imaging, comprising:建模模块,用于建立三维笛卡尔坐标系下的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:所有回波信号沿一个坐标方向平行采集,每条回波信号在另外两个坐标方向形成的平面内的坐标由二维黄金分割比例计算得到; The modeling module is configured to establish a k-space model in a three-dimensional Cartesian coordinate system, and determine an acquisition trajectory of the echo signal in the model, wherein the trajectory of the echo signal is: all echo signals are collected in parallel along a coordinate direction The coordinates of each echo signal in the plane formed by the other two coordinate directions are calculated by 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。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 that conforms to the collected trajectory.
- 根据权利要求9所述的***,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 system 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)设回波信号沿x轴频率编码方向采集,第i次采集的回波信号在与之垂直平面内的平面坐标为(yi,zi),初始回波的编号为i=i0;1) Set the echo signal to be acquired along the x-axis frequency encoding direction. The plane coordinate of the echo signal acquired in the i-th plane is (y i , z i ) in the plane perpendicular to it, and the initial echo number is i=i 0 ;2)根据二维黄金分割比例系数计算平面坐标(yi,zi);2) Calculate the plane coordinates (y i , z i ) according to the two-dimensional golden section scale coefficient;3)根据预设截止条件判断采集是否结束,即第i次采集的回波信号是否为采集的最后一条回波信号;3) judging whether the acquisition is finished according to the preset cutoff condition, that is, whether the echo signal collected by the i th is the last echo signal collected;4)若是,则采集结束,否则使i=i+1,重复1)到3)直至采集结束。4) If yes, the acquisition ends, otherwise let i=i+1, repeat 1) to 3) until the end of the acquisition.
- 根据权利要求10所述的***,其特征在于,所述二维黄金分割比例系数为GR1,GR2,GR1≈0.4656,GR2≈0.6823;所述回波信号在垂直平面内两个方向的坐标分别与GR1、GR2对应。The system according to claim 10, wherein said two-dimensional golden division ratio coefficients are GR1, GR2, GR1 ≈ 0.4656, and GR2 ≈ 0.6823; coordinates of the echo signals in two directions in a vertical plane are respectively GR1 and GR2 correspond to each other.
- 根据权利要求10所述的***,其特征在于,所述建模模块包括:The system of claim 10 wherein said modeling module comprises:计算单元,用于当三维k空间的分辨率为Resx×Resy×Resz,回波信号沿x轴方向采集时,通过下式计算所述回波信号在垂直平面yOz内的平面坐标(yi,zi):a calculation unit for calculating a plane coordinate of the echo signal in a vertical plane yOz by the following formula when the resolution of the three-dimensional k-space is Res x ×Res y ×Res z and the echo signal is acquired along the x-axis direction ( y i ,z i ):yi=mod(i×GR1,1)×Resy,zi=mod(i×GR2,1)×Resz y i = mod(i × GR 1 , 1) × Res y , z i = mod(i × GR 2 , 1) × Res z或者,or,yi=mod(i×GR2,1)×Resy,zi=mod(i×GR1,1)×Resz y i = mod(i × GR 2 , 1) × Res y , z i = mod(i × GR 1 , 1) × Res z其中,mod(a,b)为求a/b的余数。Among them, mod(a,b) is the remainder of a/b.
- 根据权利要求10-12任一项所述的***,其特征在于,所述建模模块还包括:The system of any of claims 10-12, wherein the modeling module further comprises:网格化单元,用于将(yi,zi)的计算值分配到该平面内最近的整数网格点 上;a meshing unit for assigning a calculated value of (y i , z i ) to a nearest integer grid point in the plane;去重单元,用于在预设范围内对所述整数网格点的坐标进行查重,若不存在相同坐标,将所述整数网格点的坐标作为采集所述回波信号的平面坐标;若已存在相同坐标,则根据二维黄金分割比例系数计算平面坐标(yi+1,zi+1)。The de-weighting unit is configured to check the coordinates of the integer grid point within a preset range. If the same coordinates are not present, the coordinates of the integer grid point are used as plane coordinates for acquiring the echo signal; If the same coordinates already exist, the plane coordinates (y i+1 , z i+1 ) are calculated according to the two-dimensional golden section scale factor.
- 根据权利要求10所述的***,其特征在于,所述建模模块还包括:The system of claim 10, wherein the modeling module further comprises:存储单元,用于预先存储每次计算的回波信号的平面坐标;a storage unit, configured to pre-store a plane coordinate of the echo signal calculated each time;其中,所述采集模块还用于在采集k空间数据时调用所述存储单元中的坐标来确定回波信号的采集轨迹。The collection module is further configured to call coordinates in the storage unit to determine a collection trajectory of the echo signal when acquiring k-space data.
- 根据权利要求10所述的***,其特征在于,所述初始回波的编号i0为任意自然数。 The system of claim 10 wherein said initial echo number i 0 is any natural number.
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Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102540115A (en) * | 2011-12-12 | 2012-07-04 | 中国科学院深圳先进技术研究院 | Magnetic resonance imaging method and system |
WO2012143021A1 (en) * | 2011-04-21 | 2012-10-26 | Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V. | Spatially encoded phase-contrast mri |
CN103777162A (en) * | 2012-10-19 | 2014-05-07 | 上海联影医疗科技有限公司 | Magnetic resonance imaging K space movement artifact correction parallel acquisition reconstruction method |
CN104042216A (en) * | 2014-07-01 | 2014-09-17 | 中国科学院武汉物理与数学研究所 | Fast thin layer magnetic resonance imaging method based on pre-scanning and non-uniform sampling |
CN105957117A (en) * | 2016-04-26 | 2016-09-21 | 东南大学 | Parallel magnetic resonance image reconstruction method, parallel magnetic resonance image reconstruction device, and parallel magnetic resonance imaging system |
-
2016
- 2016-11-04 WO PCT/CN2016/104667 patent/WO2018082028A1/en active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012143021A1 (en) * | 2011-04-21 | 2012-10-26 | Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V. | Spatially encoded phase-contrast mri |
CN102540115A (en) * | 2011-12-12 | 2012-07-04 | 中国科学院深圳先进技术研究院 | Magnetic resonance imaging method and system |
CN103777162A (en) * | 2012-10-19 | 2014-05-07 | 上海联影医疗科技有限公司 | Magnetic resonance imaging K space movement artifact correction parallel acquisition reconstruction method |
CN104042216A (en) * | 2014-07-01 | 2014-09-17 | 中国科学院武汉物理与数学研究所 | Fast thin layer magnetic resonance imaging method based on pre-scanning and non-uniform sampling |
CN105957117A (en) * | 2016-04-26 | 2016-09-21 | 东南大学 | Parallel magnetic resonance image reconstruction method, parallel magnetic resonance image reconstruction device, and parallel magnetic resonance imaging system |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN114114118A (en) * | 2020-08-27 | 2022-03-01 | 上海联影医疗科技股份有限公司 | Magnetic resonance image reconstruction method, magnetic resonance image reconstruction device, computer equipment and storage medium |
CN114114118B (en) * | 2020-08-27 | 2023-08-22 | 上海联影医疗科技股份有限公司 | Magnetic resonance image reconstruction method, apparatus, computer device and storage medium |
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