WO2018113518A1 - Method for monitoring temperature of tissues surrounding active implant, and magnetic resonance imaging system - Google Patents

Abstract

A method for monitoring the temperature of tissues surrounding an active implant, the method being based on the magnetic resonance temperature detection technology and using a magnetic resonance imaging (MRI) system (20); the MRI system (20) at least comprising a sequence 2 for clinical examination or scientific research or other uses and a sequence 3 for measuring temperature distribution. The method comprises the following steps: step S11, performing scan using a sequence 2, and performing the scan of a temperature measurement sequence 3 alternately in the sequence 2; and step S12, performing a safety assessment according to the scanning result of the temperature measurement sequence 3. The method can effectively monitor the radio-frequency temperature rise of a patient wearing an implantable medical device who is undergoing an MRI scan, removing potential safety risk.

Description

一种监测有源植入物周围组织温度的方法和磁共振成像***Method for monitoring tissue temperature around active implant and magnetic resonance imaging system

相关申请Related application

本申请要求2016年12月23日申请的，申请号为201611201915.4，名称为“一种监测有源植入物周围组织温度的方法和磁共振成像***”的中国专利申请的优先权，在此将其全文引入作为参考。The present application claims priority to Chinese Patent Application No. 201611201915.4, entitled "A Method for Monitoring Tissue Temperature Around Active Implants and a Magnetic Resonance Imaging System", which is hereby incorporated by reference. The full text is incorporated by reference.

技术领域Technical field

本申请涉及医疗器械相关技术领域，尤其，涉及一种基于磁共振((Magnetic Resonance,MR)测温技术的实时监测MR下有源植入物周围组织温度的方法和采用该方法的磁共振成像***。The present application relates to the technical field of medical devices, and in particular to a method for real-time monitoring of tissue temperature around an active implant under MR based on magnetic resonance (MR) temperature measurement technology and magnetic resonance imaging using the same system.

背景技术Background technique

磁共振成像技术(Magnetic Resonance Imaging,MRI)与其他成像技术(如X射线、CT等)相比，有着比较显著的优势：磁共振成像更为清晰，对软组织有很高的分辨力，而且对人体无电离辐射损伤。所以，磁共振成像技术被广泛地应用于现代医学的临床诊断之中。据估计，如今全球每年至少有6000万病例利用核磁共振成像技术进行检查。Compared with other imaging technologies (such as X-ray, CT, etc.), Magnetic Resonance Imaging (MRI) has obvious advantages: magnetic resonance imaging is clearer, has high resolution to soft tissue, and The human body has no ionizing radiation damage. Therefore, magnetic resonance imaging technology is widely used in the clinical diagnosis of modern medicine. It is estimated that at least 60 million cases are examined annually using MRI technology.

MRI工作时会有三个磁场发挥作用。一个高强度的均匀静磁场B₀,一个梯度场G以及用于激发核磁共振信号的射频(RF)磁场。具体成像过程简述如下：首先，在静磁场B₀的作用下，人体内的氢原子核沿着静磁场方向发生进动，根据Larmor定理，氢核进动频率为ω＝γB，其中ω为进动频率，γ为旋磁比，B为磁场强度；即进动的频率与磁场强度成正比。为了激发特定层面内的信号，在静磁场方向上施加梯度场G_z，使得不同层的空间位置上具有不同的磁场强度；同时施加一定频率一定带宽的射频场RF，RF信号的频率和带宽与选层空间内的Larmor频率相对应，因此只有选层方向上特定层内的组织中的氢核才能被激发，产生信号。信号被激发后开始不断衰减，通过射频磁场和梯度磁场的组合，可以使激发的核磁信号出现局部峰值，称为回波；通常在回波出现的时间前后进行信号采集。在被激发的层内，为了区分不同位置的信号，使用相位编码和频率编码梯度场对信号进行空间位置编码。在信号读出前，沿静磁场方向叠加相位编码梯度磁场(磁场梯度通常沿y轴)，持续一定时间后关闭，此时相位编码方向上不同位置信号具有不同的相位。紧接着进行频率编码，类似地在频率编码方向上施加梯度磁场(频率编码梯度方向通常沿x轴)，使得频率编码方向上，不同位置的信号具有不同的频率。经过上述空间编码过程，信号的相位和频率就包含了信号的空间位置信 息，而信号的强度反映了该位置上人体组织的解剖结构或生理状态。在频率编码的同时，开始信号采集：在N个等距时间步骤中读取磁共振信号，将得到的数据存在k空间的一行。接着重复上述过程，只需要在相位编码阶段选取不同的梯度场G_y强度，将读取的数据作为k空间的另一行存在相应的位置，直至k空间被填满。这样，总共得到一个具有N×N个数据点的数字矩阵，从中可以通过二维傅里叶变换在图像空间内构造一幅图像。There are three magnetic fields that work when MRI is working. A high-intensity uniform static magnetic field B ₀ , a gradient field G, and a radio frequency (RF) magnetic field for exciting nuclear magnetic resonance signals. The specific imaging process is briefly described as follows: First, under the action of the static magnetic field B ₀ , the hydrogen nuclei in the human body precession along the direction of the static magnetic field. According to the Larmor theorem, the precession frequency of the hydrogen nuclei is ω=γB, where ω is The dynamic frequency, γ is the gyromagnetic ratio, and B is the magnetic field strength; that is, the precession frequency is proportional to the magnetic field strength. In order to excite the signal in a specific layer, the gradient field G _z is applied in the direction of the static magnetic field so that the spatial positions of the different layers have different magnetic field strengths; at the same time, the RF field RF with a certain frequency of a certain frequency is applied, and the frequency and bandwidth of the RF signal are The Larmor frequency in the layered space corresponds, so that only the hydrogen nuclei in the tissue in a particular layer in the layering direction can be excited to generate a signal. After the signal is excited, it begins to decay. By the combination of the RF magnetic field and the gradient magnetic field, the excited nuclear magnetic signal can be locally peaked, called echo; usually, the signal is collected before and after the echo occurs. Within the layer being excited, in order to distinguish signals at different locations, the phase encoding and frequency encoding gradient fields are used to spatially encode the signals. Before the signal is read out, the phase-encoding gradient magnetic field is superimposed along the direction of the static magnetic field (the magnetic field gradient is usually along the y-axis), and is turned off after a certain period of time. At this time, the signals at different positions in the phase encoding direction have different phases. Following the frequency encoding, a gradient magnetic field is applied similarly in the frequency encoding direction (the frequency encoding gradient direction is usually along the x-axis) such that signals in different positions have different frequencies in the frequency encoding direction. After the above spatial encoding process, the phase and frequency of the signal contain spatial position information of the signal, and the strength of the signal reflects the anatomical structure or physiological state of the human tissue at the position. At the same time as frequency encoding, signal acquisition is started: the magnetic resonance signals are read in N equidistant time steps, and the resulting data is stored in one line of k space. Then repeat the above process, only need to select different gradient field G _y intensity in the phase encoding stage, and the read data exists as a corresponding position of another line of k space until the k space is filled. Thus, a total of one digital matrix with N x N data points is obtained, from which an image can be constructed in the image space by two-dimensional Fourier transform.

如果患者体内安装有植入式医疗器械(Implantable Medical Device,IMD)，例如：心脏起搏器、除颤器、迷走神经刺激器、脊髓刺激器、脑深部电刺激器等的话，MRI工作时所需使用的三个磁场可能会给患者带来很大的安全风险。其中最重要的一个隐患是植入式医疗器械在射频场中的感应发热，特别是对于那些带有细长导电结构，典型的如脑深部电刺激器延长导线和电极导线，心脏起搏器电极线。体内装有这些植入式医疗器械的患者在进行MRI扫描的时候，在细长导电结构尖端与组织接触的部位可能会出现严重的温升，这样的温升可能会对患者造成严重的伤害。然而，大部分植入IMD的患者在器械寿命周期内需要进行MRI检查，而射频磁场感应带来的安全隐患导致这部分病人被拒绝进行检查。If the patient is equipped with an implantable medical device (IMD), such as a cardiac pacemaker, a defibrillator, a vagus nerve stimulator, a spinal cord stimulator, a deep brain stimulator, etc., it is required for MRI work. The three magnetic fields used may pose a significant safety risk to the patient. One of the most important hidden dangers is the inductive heating of implantable medical devices in the RF field, especially for those with elongated conductive structures, such as deep brain electrical stimulator extension leads and electrode leads, cardiac pacemaker electrodes. line. Patients with these implantable medical devices in their body may experience severe temperature rise at the tip of the elongated conductive structure in contact with the tissue during MRI scans. Such temperature rise may cause serious injury to the patient. However, most patients with IMD implants require MRI during the life of the device, and the safety hazards associated with RF magnetic field induction have led to rejection of these patients.

射频磁场下细长导电结构的感应受热的原因是细长导电结构与射频磁场之间的耦合。细长导电结构与射频磁场之间的耦合在细长导电结构中产生感应电流，感应电流主要通过导电结构尖端与人体组织接触的部分输送到组织中，形成感生电场集中分布。人体组织电阻率较高，会产生较多的焦耳热。The reason for the induced heating of the elongated conductive structure under the RF magnetic field is the coupling between the elongated conductive structure and the RF magnetic field. The coupling between the elongated conductive structure and the radio frequency magnetic field generates an induced current in the elongated conductive structure, and the induced current is mainly transported into the tissue through the portion of the conductive structure tip that is in contact with the human tissue to form a concentrated distribution of the induced electric field. Human tissue has a higher electrical resistivity and produces more Joule heat.

射频感生电场导致的组织发热可以用生物传热公式刻画，传热公式为：The tissue heating caused by the RF induced electric field can be characterized by the bioheat transfer formula. The heat transfer formula is:

其中T为组织温度，Q为射频感应沉积的能量，S为新陈代谢产生的热量，ρ为密度，C为比热容，ω为血液的灌注率，下标b表示血液的性质，如T_b为局部血液温度。射频磁场感生的电场导致组织加热，并以生物传热规律变化。Where T is the tissue temperature, Q is the energy of RF induction deposition, S is the heat generated by metabolism, ρ is the density, C is the specific heat capacity, ω is the blood perfusion rate, and subscript b is the nature of the blood, such as T _b is the local blood. temperature. The electric field induced by the RF magnetic field causes the tissue to heat up and change in accordance with the laws of biological heat transfer.

由于射频温升最严重的地方通常发生在植入式医疗器械细长导体结构尖端，同时也受材料生物相容性、传感器尺寸、MRI下电磁干扰等因素的影响，传统的温度传感器如热电偶、热电阻等难以集成。即使能够集成，因为要在MRI下应用，也存在测量数据与外界实时交互的问题。因此目前这些植入式医疗器械植入患者体内后，进行MRI扫描的射频感应温升尚无有效的监控手段。Because the most severe RF rise is usually at the tip of the elongated conductor structure of implantable medical devices, and is also affected by factors such as material biocompatibility, sensor size, and electromagnetic interference under MRI, traditional temperature sensors such as thermocouples , thermal resistance, etc. are difficult to integrate. Even if it can be integrated, there is a problem that measurement data interacts with the outside world in real time because it is applied under MRI. Therefore, there is no effective monitoring method for the RF induction temperature rise of MRI scans after implanted medical devices are implanted in patients.

而MRI本身扫描的数据有可能可以提供一种实时、无创的温度监控途径。多种MR参数表现出了温度敏感性，利用这些温度敏感参数能够得到组织的温度变化。例如，质子共振频率会随着温度的变化而改变，利用梯度回波(GRE)序列得到的相位图也会发生改变，相位 变化与温度变化满足如下关系：The data scanned by MRI itself may provide a real-time, non-invasive temperature monitoring approach. A variety of MR parameters exhibit temperature sensitivity, and these temperature-sensitive parameters can be used to obtain tissue temperature changes. For example, the proton resonance frequency changes with temperature, and the phase map obtained with the gradient echo (GRE) sequence also changes. The change and the temperature change satisfy the following relationship:

其中，Δφ是前后两幅相位图的相位差，ΔT是前后两次图像采集时刻的温度差，α是温度相关的水分子化学键转移系数，B₀是静磁场强度，γ是旋磁比，TE是回波时间。Where Δφ is the phase difference between the two phase diagrams before and after, ΔT is the temperature difference between the two image acquisition times before and after, α is the temperature-dependent chemical transfer coefficient of water molecules, B ₀ is the static magnetic field strength, γ is the gyromagnetic ratio, TE It is the echo time.

目前MR测温已经成功的应用于射频消融损毁、聚焦超声***等方面。在这些应用中，加热源都来自外部治疗设备。MR测温法只作为一个监控方法。而针对植入式医疗器械在核磁下的射频发热，加热来自MRI扫描本身，而扫描序列各有用途，参数各不相同，与MR测温法的扫描差异很大，无法从其他用途的扫描序列中获取温度信息。At present, MR temperature measurement has been successfully applied to radiofrequency ablation damage, focused ultrasound treatment of tumors and so on. In these applications, the heating source is from an external treatment device. The MR temperature measurement method is only used as a monitoring method. For the RF fever of the implanted medical device under nuclear magnetic resonance, the heating comes from the MRI scan itself, and the scan sequence has its own use, the parameters are different, and the scan with the MR temperature measurement method is very different, and the scan sequence cannot be used from other uses. Get temperature information.

此外，植入式医疗器械中的金属导体还会因为在MRI的磁场下磁化而引起周围磁场畸变，从而导致图像伪影，使得导体附近的MRI信号丢失或严重失真。而射频感应发热在导体附近是最严重的，这也是目前MR测温法应用中的问题。In addition, metal conductors in implantable medical devices can also cause distortion of the surrounding magnetic field due to magnetization under the magnetic field of MRI, resulting in image artifacts, resulting in loss or severe distortion of the MRI signal near the conductor. Radio frequency induction heating is the most serious in the vicinity of the conductor, which is also a problem in the current application of MR temperature measurement.

因此，本申请提出一种MR测温序列与一般用途扫描穿插进行的方法及其装置，以监控带有植入式医疗器械的患者进行MRI扫描时的射频温升。进一步的，提出采用MRI图像上器械伪影以外的有效数据，利用传热规律反求其表面温度的方法及其装置。Accordingly, the present application is directed to a method and apparatus for MR temperature measurement sequences and general purpose scan interspersed to monitor radio frequency rise in MRI scans of a patient with an implantable medical device. Further, a method and a device for using the effective data other than the artifacts on the MRI image to reverse the surface temperature by using the heat transfer law are proposed.

发明内容Summary of the invention

基于此，本申请提出了一种基于MR测温的实时监测MR下金属植入物周围组织温度并给出安全评估的方法和磁共振成像***。Based on this, the present application proposes a method for real-time monitoring of tissue temperature around a metal implant under MR based on MR temperature measurement and a method for safety assessment and a magnetic resonance imaging system.

一种监测有源植入物周围组织温度的方法，该方法基于磁共振测温技术且采用一磁共振成像***；该磁共振成像***至少包括一种用于临床检查或科学研究或其他目用途的序列2和一种用于测量温度分布的序列3；该方法包括以下步骤：步骤S11，采用序列2进行扫描，并在序列2中穿插进行测温序列3的扫描；以及步骤S12，根据测温序列3的扫描结果进行安全评估。A method of monitoring tissue temperature around an active implant, the method being based on magnetic resonance thermometry and employing a magnetic resonance imaging system; the magnetic resonance imaging system comprising at least one for clinical examination or scientific research or other purposes Sequence 2 and a sequence 3 for measuring temperature distribution; the method comprises the following steps: step S11, scanning with sequence 2, and interpolating in sequence 2 for scanning of temperature measurement sequence 3; and step S12, according to measurement The scan result of the warm sequence 3 is evaluated for safety.

根据上述监测有源植入物周围组织温度的方法，所述采用序列2进行扫描，并在序列2中穿插进行测温序列3的扫描的方法包括：将序列2分割为i个部分，且每部分分别含有n₁，n₂，…，n_i个TR单元，其中，TR为序列2中两个激发脉冲间的间隔时间；在序列2的首尾以及各部分之间穿插进行序列3的扫描，且序列2每一部分与前一个和后一个序列3之间的时间间隔分别为Δt_1a、Δt_1b、Δt_2a、Δt_2b、…、Δt_ia、Δt_ib。According to the above method for monitoring the tissue temperature around the active implant, the method of scanning with sequence 2 and interspersing the sequence 2 for scanning of the temperature measurement sequence 3 comprises: dividing the sequence 2 into i parts, and each The portions respectively contain n ₁ , n ₂ , ..., n _i TR units, wherein TR is the interval between two excitation pulses in sequence 2; the sequence 3 is interspersed between the beginning and the end of sequence 2 and between the parts, And the time interval between each part of the sequence 2 and the previous one and the next sequence 3 is Δt _1a , Δt _1b , Δt _2a , Δt _2b , ..., Δt _ia , Δt _{ib , respectively} .

如上述监测有源植入物周围组织温度的方法，其中，所述时间间隔Δt_1a、Δt_1b、Δt_2a、Δt_2b、…、Δt_ia、Δt_ib均为零；且相邻序列3之间的间隔相等。A method of monitoring tissue temperature around an active implant as described above, wherein the time intervals Δt _1a , Δt _1b , Δt _2a , Δt _2b , ..., Δt _ia , Δt _ib are all zero; and between adjacent sequences 3 The intervals are equal.

如上述监测有源植入物周围组织温度的方法，其中，所述采用序列2进行扫描包括扫描 多层图像，每一层图像由一组k空间的数据重建得到，每一组k空间数据由多个TR单元的扫描产生，每个TR单元扫描产生k空间中的一行或几行数据；当n_iTR>T_slice时，选择在成像序列得到的k空间数据层间穿插进行测温选层的测温序列3扫描的方式；当n_iTR<T_slice时，或者n_iTR不是T_slice的整数倍时，选择在k空间数据行间穿插进行测温选层的测温序列3扫描的方式；其中，T_slice为序列2扫描1层所需的时间。A method for monitoring tissue temperature around an active implant as described above, wherein said scanning using sequence 2 comprises scanning a multi-layer image, each layer image being reconstructed from a set of k-space data, each set of k-space data being Scanning of a plurality of TR units is generated, and each TR unit scan generates one or several lines of data in k space; when n _i TR>T _slice , interpolating between k-space data layers obtained by the imaging sequence for temperature measurement and selection The temperature measurement sequence 3 scan mode; when n _i TR<T _slice , or n _i TR is not an integer multiple of the T _slice , the temperature measurement sequence 3 scan of the temperature selection layer is interspersed between the k-space data lines. Way; where T _slice is the time required for sequence 2 to scan 1 layer.

如上述监测有源植入物周围组织温度的方法，其中，所述在序列2的首尾以及各部分之间穿插进行序列3的扫描的方法包括：将测温序列3在序列2的扫描前的扫描得到的相位图作为参考相位图

将测温序列3第k次采集得到的相位图记作

第k次采集时的温度变化分布ΔT_map可根据式(3)求得，

其中，α是温度相关的水分子化学键转移系数，B₀是静磁场强度，γ是旋磁比，TE是回波时间。A method of monitoring tissue temperature around an active implant as described above, wherein the method of interspersing the scan of sequence 3 between the beginning and the end of sequence 2 and between the portions comprises: measuring temperature sequence 3 prior to scanning of sequence 2 Scanned phase map as reference phase map

Record the phase map obtained by the kth acquisition of the temperature measurement sequence 3 as

The temperature change distribution ΔT _map at the time of the kth acquisition can be obtained according to the formula (3).

Where α is the temperature-dependent chemical transfer coefficient of water molecules, B ₀ is the static magnetic field strength, γ is the gyromagnetic ratio, and TE is the echo time.

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S12包括以下步骤：步骤S121，确定评估区域；步骤S122，确定评估区域的温升分布；步骤S123，计算安全指标；以及步骤S124，将该安全指标与安全阈值进行比较。The method for monitoring the temperature of the tissue around the active implant as described above, wherein the step S12 comprises the following steps: step S121, determining an evaluation area; step S122, determining a temperature rise distribution of the evaluation area; and step S123, calculating a safety indicator; Step S124, comparing the security indicator with a security threshold.

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S121包括：利用边缘检测算法确定出伪影边缘；以及采用分类算法确定伪影边缘的像素点所属类型。The method for monitoring tissue temperature around an active implant as described above, wherein the step S121 comprises: determining an artifact edge by using an edge detection algorithm; and determining a type of pixel point of the artifact edge by using a classification algorithm.

如上述监测有源植入物周围组织温度的方法，其中，所述磁共振成像***还包括一种用于定位或其他与扫描用途的序列1；步骤S11之前进一步包括步骤S10，将一场漂校正装置安装在扫描部位周围的合适区域，采用序列1进行定位扫描，确定测温选层和成像选层。A method of monitoring tissue temperature around an active implant as described above, wherein the magnetic resonance imaging system further comprises a sequence 1 for positioning or other use for scanning; and step S11 further comprises step S10 to The calibration device is mounted in a suitable area around the scanning site, and sequence 1 is used for positioning scanning to determine the temperature selection layer and the imaging selection layer.

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S122包括：校正场漂引起的温度变化得到实际温度分布图像的步骤；所述校正场漂引起的温度变化得到实际温度分布图像的方法包括：在温度分布图中，每个场漂校正容器对应图像的中心区域选取若干点，将每个点的位置信息与温度变化信息存储在矩阵A(i,j,ΔT)中，用线性插值的方法求出场漂引起的伪温度变化分布图，其中计算过程通过求解超定问题

(4)，其中，[ij1]_n×3的第一列为A(:,1)，第二列为A(:,2)，第三列全是1；上述问题的超定解得到最小二乘意义下的线性插值结果z＝a·i+b·j+c，将原始温度变化分布图减去z，便得到了校正后的实际温度分布ΔT_correction，即，ΔT_correction(i,j)＝ΔT_map(i,j)-z(5)。The method for monitoring the temperature of the tissue around the active implant as described above, wherein the step S122 includes: a step of correcting a temperature change caused by the field drift to obtain an actual temperature distribution image; and correcting the temperature change caused by the field drift to obtain an actual temperature distribution The image method includes: in the temperature distribution map, each field drift correction container selects a plurality of points corresponding to a central area of the image, and stores position information and temperature change information of each point in the matrix A(i, j, ΔT), The pseudo-temperature variation profile caused by field drift is obtained by linear interpolation method, in which the calculation process solves the overdetermined problem

(4), where [ij1] the first column of _n×3 is A(:,1), the second column is A(:,2), and the third column is all 1; the overdetermined solution of the above problem is minimized The linear interpolation result z=a·i+b·j+c in the sense of squares is obtained by subtracting z from the original temperature variation profile, and the corrected actual temperature distribution ΔT _{correction is obtained} , that is, ΔT _correction (i, j) ) = ΔT _map (i, j) - z (5).

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S123包括：步骤S1231，选取伪影边缘外一定范围内的像素点温度信息作为边界条件，将每个像素点的位置信息和温 度变化信息分别存入矩阵r＝(r₁,r₂,...r_m)和p_k＝(T_k1,T_k2,...,T_km)，其中r_m表示第m个像素点的位置信息，T_km表示第m个像素点第k次测量得到的温度变化；The method for monitoring the temperature of the tissue surrounding the active implant, wherein the step S123 comprises: step S1231, selecting pixel temperature information within a certain range outside the edge of the artifact as a boundary condition, and setting the position information of each pixel. And temperature change information are stored in the matrix r = (r ₁ , r ₂ , ... r _m ) and p _k = (T _k1 , T _k2 , ..., T _km ), respectively, where r _m represents the mth pixel The position information of the point, T _km represents the temperature change obtained by the kth measurement of the mth pixel point;

步骤S1232，将第k次测量结合前k-1次测量得到的温度数据存入一个矩阵P，Step S1232, storing the temperature data obtained by combining the kth measurement and the k-1th measurement into a matrix P,

步骤S1233，通过电磁仿真，以该有源植入物导电部分-组织界面处电流密度J作为参数，以J₀＝1000作为标准热扩散模型，计算出位置在r＝(r₁,r₂,...r_m)，对应于k次扫描时刻的温度变化矩阵st_P，

其中，st_P(i,j)代表标准扩散模型中位置在r_j对应第i次扫描时刻的温度变化值，根据式ΔT＝a·J²可得到，

(8)；Step S1233, by electromagnetic simulation, taking the current density J at the conductive portion-tissue interface of the active implant as a parameter, and J ₀ =1000 as a standard thermal diffusion model, and calculating the position at r=(r ₁ , r ₂ , ... r _m), corresponding to a temperature change matrix st_P k scan time,

Where st_P(i,j) represents the temperature change value of the position in the standard diffusion model corresponding to the i-th scan time of r _{j ,} which can be obtained according to the formula ΔT=a·J ² ,

(8);

步骤S1234，令式

求导等于零便可求得极值点

的值，

Step S1234, the order

The derivative is equal to zero to find the extreme point

Value,

步骤S1235，将

带入到热扩散仿真模型st_P(i,j)，得到有源植入物表面的温度分布，从模型中提取出温升最高点的温度变化曲线；以及步骤S1236，根据所述温升最高点的温度变化曲线得到扫描时间范围内对应的热累积量和最高温升。Step S1235, will

Bringing into the thermal diffusion simulation model st_P(i,j), obtaining the temperature distribution of the active implant surface, extracting the temperature change curve of the highest temperature rise point from the model; and step S1236, according to the highest temperature rise point The temperature profile yields the corresponding thermal accumulation and the highest temperature rise over the scan time range.

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S1236中，所述热累积量通过公式(11)

计算，其中，当T(t)＞43C时，R＝0.5；当T(t)＜43C时，R＝0.25。The method for monitoring the tissue temperature around the active implant as described above, wherein in the step S1236, the heat accumulation amount passes the formula (11)

In the calculation, when T(t)>43C, R=0.5; when T(t)<43C, R=0.25.

如上述监测有源植入物周围组织温度的方法，其中，所述步骤S124包括：将计算得到的热累积量与事先设定的阈值比较，同时比较最高温升与事先设定的最高温升阈值，两者之中 任何一个超过阈值，所述数据处理单元及时向所述MR控制单元发出危险预警，自动停止MR扫描设备的扫描。The method for monitoring the temperature of the tissue around the active implant as described above, wherein the step S124 comprises: comparing the calculated heat accumulation amount with a preset threshold value, and comparing the highest temperature rise with the preset maximum temperature rise. Threshold, in between When any one exceeds the threshold, the data processing unit issues a danger warning to the MR control unit in time to automatically stop scanning of the MR scanning device.

一种磁共振成像***，其包括：一MR扫描设备，该MR扫描设备至少包括一种用于临床检查或科学研究或其他目用途的序列2和一种用于测量温度分布的序列3；一MR控制单元，该MR控制单元用于控制该MR扫描设备采用序列2和序列3进行扫描；以及一数据处理单元，该数据处理单元用于处理该测温序列3的扫描结果，其中，该磁共振成像***具有监测有源植入物周围组织温度的功能。A magnetic resonance imaging system comprising: an MR scanning device comprising at least one sequence 2 for clinical examination or scientific research or other purposes of use and a sequence 3 for measuring temperature distribution; An MR control unit for controlling the MR scanning device to scan using sequence 2 and sequence 3; and a data processing unit for processing the scan result of the temperature measurement sequence 3, wherein the magnetic The resonant imaging system has the function of monitoring the temperature of the tissue surrounding the active implant.

相较于现有技术，本申请提供的磁共振成像***监测有源植入物周围组织温度的方法可以有效监控带有植入式医疗器械的患者进行MRI扫描时的射频温升，排除安全隐患。Compared with the prior art, the magnetic resonance imaging system provided by the present application monitors the tissue temperature around the active implant, and can effectively monitor the radio frequency rise of the MRI scan of the patient with the implanted medical device, thereby eliminating the safety hazard. .

附图说明DRAWINGS

图1为本申请实施例采用的脑深部电刺激器的结构示意图。FIG. 1 is a schematic structural view of a deep brain electric stimulator used in an embodiment of the present application.

图2为本申请实施例提供的磁共振成像***的模块示意图。FIG. 2 is a schematic block diagram of a magnetic resonance imaging system according to an embodiment of the present application.

图3为本申请实施例采用的场漂校正装置的结构示意图。FIG. 3 is a schematic structural diagram of a field drift correcting device used in an embodiment of the present application.

图4为本申请实施例在序列2中间隔穿插进行测温序列3的扫描方式的示意图。FIG. 4 is a schematic diagram of a scanning manner of the temperature measurement sequence 3 interspersed in sequence 2 in the embodiment of the present application.

图5为本申请实施例在序列2中连续穿插进行测温序列3的扫描方式的示意图。FIG. 5 is a schematic diagram of a scanning manner of the temperature measurement sequence 3 continuously interspersed in the sequence 2 in the embodiment of the present application.

图6为本申请实施例采用的层间穿插进行测温序列扫描和行间穿插进行测温序列扫描的示意图。FIG. 6 is a schematic diagram of temperature sequence scanning and inter-line interleaving for temperature measurement sequence scanning according to an embodiment of the present application.

图7为本申请实施例采用的层间穿插进行测温序列扫描的方法流程图。FIG. 7 is a flow chart of a method for performing temperature measurement sequence scanning by inter-layer interleaving according to an embodiment of the present application.

图8为本申请实施例采用的行间穿插进行测温序列扫描的方法流程图。FIG. 8 is a flow chart of a method for performing temperature measurement sequence scanning by inter-line interleaving according to an embodiment of the present application.

图9为本申请实施例确定该有源植入物的伪影区域的方法流程图。9 is a flow chart of a method for determining an artifact region of an active implant in accordance with an embodiment of the present application.

图10为本申请实施例校正场漂引起的温度变化时在场漂校正容器对应图像的中心区域选取若干点的示意图。FIG. 10 is a schematic diagram of selecting a plurality of points in a central region of a corresponding image of a field drift correction container when the temperature change caused by the field drift is corrected according to an embodiment of the present application.

主要元件符号说明Main component symbol description

脑深部电刺激器                10 Deep brain stimulator 10

外部程控仪                    11 External programmer 11

脉冲发生器                    12 Pulse generator 12

延长导线                      14 Extension wire 14

刺激电极                      16 Stimulation electrode 16

电极触点                      18 Electrode contact 18

磁共振成像***                20 Magnetic resonance imaging system 20

MR扫描设备                    22 MR scanning equipment 22

MR控制单元                    24 MR control unit 24

数据处理单元                  26 Data processing unit 26

场漂校正装置                  30Field drift correction device 30

头部                          32 Head 32

容器                          34 Container 34

细绳                          36 String 36

伪影区域                      40 Artifact area 40

伪影边缘                      42 Artifact edge 42

组织信号                      44 Organizational signal 44

中心区域                      46 Central area 46

如下具体实施例将结合上述附图进一步说明本申请。The following specific embodiments will be further described in conjunction with the above drawings.

具体实施方式detailed description

本申请提供了一种基于MR测温的实时监测MR下有源植入物周围组织温度并给出安全评估的方法和和采用该方法的磁共振成像***。其中该有源植入物可以为心脏起搏器、除颤器、脑深部电刺激器、脊髓刺激器、迷走神经刺激器、肠胃刺激器或者其他类似的植入式医疗器械。本申请仅以脑深部电刺激器为例进行说明，结合附图对本申请进一步说明。The present application provides a method for real-time monitoring of tissue temperature around an active implant under MR based on MR temperature measurement and giving a safety assessment and a magnetic resonance imaging system using the same. Wherein the active implant can be a cardiac pacemaker, a defibrillator, a deep brain electrical stimulator, a spinal cord stimulator, a vagus nerve stimulator, a gastrointestinal stimulator or other similar implantable medical device. The present application is only described by taking a deep brain electrical stimulator as an example, and the present application is further described with reference to the accompanying drawings.

请参见图1，所述脑深部电刺激器10包括：一外部程控仪11以及植入体内的脉冲发生器12，延长导线14和刺激电极16组成。所述外部程控仪11控制该脉冲发生器12用于产生一定模式的电流脉冲，通过该延长导线14传到刺激电极16的电极触点18处，通过该电极触点18刺激特定核团可以达到治疗疾病的目的。但是，植入有所述脑深部电刺激器10的患者在进行MR扫描时，其细长的延长导线14和刺激电极16会像天线一样吸收电磁波能量，在电极触点18处发热，存在安全隐患。为了保证这些患者扫描MR时的安全，可以利用本申请提供的方法和***对这些患者的电极触点18周围的温度实施监控和安全评估。Referring to FIG. 1, the deep brain electrical stimulator 10 includes an external programmer 11 and a pulse generator 12 implanted in the body, and an extension lead 14 and a stimulation electrode 16. The external programmer 11 controls the pulse generator 12 for generating a pattern of current pulses that are transmitted through the extension lead 14 to the electrode contacts 18 of the stimulation electrode 16 through which stimulation of a particular core can be achieved. The purpose of treating the disease. However, when an MR scan is performed on a patient implanted with the deep brain electrical stimulator 10, the elongated extension lead 14 and the stimulating electrode 16 absorb electromagnetic energy as an antenna, and generate heat at the electrode contact 18, which is safe. Hidden dangers. To ensure the safety of these patients when scanning MR, monitoring and safety assessments of the temperature around the electrode contacts 18 of these patients can be performed using the methods and systems provided herein.

请参见图2，本申请提供的磁共振成像***20包括：一MR扫描设备22，一MR控制单元24，以及一数据处理单元26。Referring to FIG. 2, the magnetic resonance imaging system 20 provided by the present application includes an MR scanning device 22, an MR control unit 24, and a data processing unit 26.

所述MR扫描设备22主要包括产生静磁场的线圈，产生梯度场的线圈，产生射频场的线圈，适用于不同部位的射频发射接收线圈，MR扫描床以及配套的自动化电气设备。The MR scanning device 22 mainly comprises a coil for generating a static magnetic field, a coil for generating a gradient field, a coil for generating a radio frequency field, a radio frequency transmitting and receiving coil for different parts, an MR scanning bed and supporting automatic electrical equipment.

所述MR控制单元24包括MR设备控制软件以及图像重建处理软件。MR设备控制软件可以设置扫描参数，设置扫描序列。特别的，MR设备控制软件集成有一种能够实时监测被试者特定解剖区域温度变化的磁共振扫描方案。方案至少包括一种用于临床检查或科学研究或其他目用途的序列2、一种用于测量温度分布的序列3。这两种序列扫查时穿插进行。 The MR control unit 24 includes MR device control software and image reconstruction processing software. The MR device control software can set the scan parameters and set the scan sequence. In particular, the MR device control software integrates a magnetic resonance scanning protocol that is capable of monitoring the temperature changes of a particular anatomical region of the subject in real time. The protocol includes at least one sequence for clinical examination or scientific research or other purposes, and a sequence 3 for measuring temperature distribution. These two sequence scans are interspersed.

一般的，该方案还包括一种用于定位或其他与扫描用途的序列1，所述序列1扫描的目的是确定感兴趣区域，特别是确定植入物所在区域。每当受试者在MR扫描设备22中的相对位置发生变化或者MR扫描设备22的定位中心发生变化或其他可能导致感兴趣区域位置发生变化的情况出现，都需要重新扫描序列1，以重新定位感兴趣区域。一般的，所述序列1应该是每次进行磁共振检查时进行的第一个扫描序列，如果第一次序列1扫描之后，没有出现可能导致感兴趣区域位置发生变化的情况，则在之后的扫描过程中无需重复进行序列1扫描。本申请不限制序列1的参数和类型。In general, the protocol also includes a sequence 1 for localization or other use for scanning, the purpose of which is to determine the region of interest, and in particular to determine the region in which the implant is located. Whenever the relative position of the subject in the MR scanning device 22 changes or the positioning center of the MR scanning device 22 changes or other conditions that may result in a change in the position of the region of interest occur, the sequence 1 needs to be rescanned to reposition Area of interest. In general, the sequence 1 should be the first scan sequence performed each time a magnetic resonance examination is performed. If the first sequence 1 scan does not occur, the position of the region of interest may be changed, then There is no need to repeat the sequence 1 scan during the scan. This application does not limit the parameters and types of Sequence 1.

所述序列2的用途是对受试者进行检查或诊断或进行科学研究，扫描结果具有临床意义或科学价值。所述序列2的参数和类型一般由医学工作者或者设备操作人员设置，本申请对比不做限定。可以理解，由于磁共振***的射频磁场与植入式医疗器械的相互作用，在序列2的扫描过程中，在受试者的特定解剖区域可能出现温度上升，当温度上升超过一定阈值或者温度累计的热量超过安全限度，可能造成受试者局部组织损伤，威胁受试者的生命健康安全。因此有必要在序列2磁共振扫描过程中实时监测受试者特定解剖区域的温度变化。本申请提供的扫描方案是在序列2之中穿插进行测温序列3的扫描。The use of the sequence 2 is to examine or diagnose a subject or to conduct scientific research, and the result of the scan has clinical significance or scientific value. The parameters and types of the sequence 2 are generally set by a medical worker or a device operator, and the comparison of the present application is not limited. It can be understood that due to the interaction between the radio frequency magnetic field of the magnetic resonance system and the implanted medical device, during the scanning of the sequence 2, a temperature rise may occur in a specific anatomical region of the subject, when the temperature rises above a certain threshold or the temperature is accumulated. The heat exceeds the safety limit, which may cause local tissue damage in the subject, which threatens the life and safety of the subject. It is therefore necessary to monitor the temperature changes of a particular anatomical region of a subject in real time during a sequence 2 magnetic resonance scan. The scanning scheme provided by the present application is a scan of the temperature measurement sequence 3 interspersed in the sequence 2.

所述序列3是温度敏感序列，当受试者特定解剖区域内的温度发生变化时，序列3的扫描结果会出现相应的变化。根据所采用的温度敏感物理参数不同，序列3的种类有多种。例如：在采用质子共振频率作为温度敏感参数的测温方法中，测温序列的种类一般是梯度回波序列(GRE序列)。本申请不限制序列3的参数和类型。每扫描一次测温序列3，可以得到一个时间点上特定区域的温度分布。可以理解，为了测温的“实时性”，所述序列3扫描的时间间隔不应该过长，而且序列3本身的持续时间也不能过长。优选的，序列3扫描的时间间隔应控制在6分钟以内，持续时间控制在2分钟以内。进一步优选的，序列3扫描的时间间隔应控制在3分钟以内，持续时间控制在30秒以内。序列3也不应该产生较大的能量沉积。优选的，序列3的局部SAR值应小于0.4W/kg。进一步优选的，序列3的局部SAR值应小于0.1W/kg。这样能够不产生额外的能量沉积，不对患者造成额外的安全风险。实际应用中，若干次序列3的扫描应该能够忠实地反映特定区域的温度变化时间过程。可以理解，序列2之中穿插进行测温序列3的扫描，并对序列3的结果进行实时处理，可实现在磁共振扫描过程中实时监测受试者特定解剖区域的温度变化。The sequence 3 is a temperature sensitive sequence, and when the temperature within a particular anatomical region of the subject changes, the scan result of sequence 3 will change accordingly. There are many types of sequence 3 depending on the temperature-sensitive physical parameters used. For example, in the temperature measurement method using the proton resonance frequency as the temperature sensitive parameter, the type of the temperature measurement sequence is generally a gradient echo sequence (GRE sequence). This application does not limit the parameters and types of Sequence 3. Each time the temperature measurement sequence 3 is scanned, the temperature distribution of a specific area at a time point can be obtained. It can be understood that for the "real-time" of temperature measurement, the time interval of the sequence 3 scan should not be too long, and the duration of the sequence 3 itself cannot be too long. Preferably, the time interval of the sequence 3 scan should be controlled within 6 minutes, and the duration is controlled within 2 minutes. Further preferably, the time interval of the sequence 3 scan should be controlled within 3 minutes and the duration controlled within 30 seconds. Sequence 3 should also not produce large amounts of energy deposition. Preferably, the local SAR value of Sequence 3 should be less than 0.4 W/kg. Further preferably, the local SAR value of Sequence 3 should be less than 0.1 W/kg. This allows for no additional energy deposition and poses no additional safety risk to the patient. In practical applications, several sequence 3 scans should be able to faithfully reflect the temperature change time course of a particular area. It can be understood that the scanning of the temperature measuring sequence 3 is interspersed in the sequence 2, and the result of the sequence 3 is processed in real time, so that the temperature change of the specific anatomical region of the subject can be monitored in real time during the magnetic resonance scanning.

下面介绍本申请将所涉及的各项参数：The following describes the parameters involved in this application:

t1：序列1扫描的持续时间。T1: Duration of sequence 1 scan.

t2：序列2不间断扫描时的持续时间，即，假设序列2扫描中间不间断，从扫描开始到扫描结束的时间。T2: duration of sequence 2 without interruption scanning, that is, assuming that the sequence 2 scan is uninterrupted, from the start of scanning to the end of scanning.

t3：每次序列3扫描的持续时间。 T3: Duration of each sequence 3 scan.

Δt：序列3的测温间隔时间，即，从一次序列3开始扫描到下一次序列3开始扫描的时间。测温间隔Δt的选取依赖具体的扫描情形，如果涉及的扫描情形温度升高缓慢，则可以采用较长的Δt监测温度变化；但如果涉及的扫描情形温升迅速或者说温度的时间梯度大，则需要较短的测温时间间隔Δt，这样一方面能提高测温时间的分辨率，另一方面能及时反馈温度信息保证受试者安全。一般的，携带有脑深部电刺激器10的患者在3T环境下扫描时，Δt选取10秒～6分钟范围内的值，因为此时电极触点18处温升很快，为了提高测量结果的准确性，一般在较短时间间隔便测量一次，例如10秒。Δt: The temperature measurement interval time of the sequence 3, that is, the time from the start of the scanning of the sequence 3 to the start of the scanning of the next sequence 3. The selection of the temperature measurement interval Δt depends on the specific scanning situation. If the temperature of the scanning situation involved is slow, the temperature change can be monitored with a longer Δt; however, if the temperature involved in the scanning situation is rapid or the time gradient of the temperature is large, A shorter temperature measurement interval Δt is required, which can improve the resolution of the temperature measurement time on the one hand, and timely feedback temperature information to ensure the safety of the subject. In general, when a patient carrying a deep brain electrical stimulator 10 scans in a 3T environment, Δt selects a value in the range of 10 seconds to 6 minutes because the temperature rise of the electrode contact 18 is fast, in order to improve the measurement result. Accuracy is typically measured at short intervals, for example 10 seconds.

T_slice：序列2扫描1层所需的时间。T _slice : The time required for sequence 2 to scan 1 layer.

TR：序列2中的重复时间，即序列2中两个激发脉冲间的间隔时间。TR: the repetition time in sequence 2, which is the interval between two excitation pulses in sequence 2.

所述数据处理单元26装有基于MR图像信息的温度计算软件，该MR控制单元24实时地将采集重建得到的测温图像实时传到该数据处理单元26。该数据处理单元26根据测温图像计算得到感兴趣区域的温度分布，并给出此时用于评价安全性的安全指标，该安全指标可以是某一温升值，或热累积剂量值，常用43摄氏度的累积等效分钟数表征(CEM43，Cumulative Equivalent Minutes@43℃)，该安全指标可以是此时感兴趣区域的最大值、此时推算的植入物(如电极)表面最大值、推算的某一时刻后的感兴趣区域的最大值、推算的某一时刻后植入物(如电极)表面最大值等。根据程序设定的安全阈值判断此时磁共振扫描的安全性，及时反馈给MR控制单元24。如果安全指标超过阈值，则所述MR控制单元24停止所述MR扫描设备22的MR扫描，否则，继续扫描。The data processing unit 26 is equipped with temperature calculation software based on MR image information, and the MR control unit 24 transmits the acquired temperature measurement image to the data processing unit 26 in real time. The data processing unit 26 calculates the temperature distribution of the region of interest based on the temperature measurement image, and gives a safety index for evaluating safety at this time, and the safety indicator may be a certain temperature rise value or a heat cumulative dose value. The cumulative equivalent number of degrees Celsius (CEM43, Cumulative Equivalent Minutes@43 °C), which can be the maximum value of the region of interest at this time, the surface maximum of the implant (such as the electrode) estimated at this time, the estimated The maximum value of the region of interest after a certain time, the maximum value of the surface of the implant (such as the electrode) after a certain time. The safety of the magnetic resonance scan at this time is judged according to the safety threshold set by the program, and is fed back to the MR control unit 24 in time. If the safety indicator exceeds the threshold, the MR control unit 24 stops the MR scan of the MR scanning device 22, otherwise, continues the scan.

以下介绍采用本申请提供的磁共振成像***20对具有有源植入物的患者进行头部MR扫描时，实时监测MR下金属植入物周围组织温度并给出安全评估的方法。该方法包括以下步骤：In the following, a magnetic resonance imaging system 20 provided by the present application is used to perform a head MR scan of a patient with an active implant, real-time monitoring of the tissue temperature around the metal implant under MR and a method for safety assessment. The method includes the following steps:

步骤S10，采用序列1进行定位扫描，确定测温选层和成像选层；Step S10, performing sequence scanning using sequence 1 to determine temperature selection layer and imaging layer selection;

步骤S11，采用序列2进行扫描，并在序列2中穿插进行测温序列3的扫描；以及Step S11, scanning is performed using sequence 2, and scanning of temperature measurement sequence 3 is interspersed in sequence 2;

步骤S12，根据测温序列3的扫描结果进行安全评估。In step S12, the security evaluation is performed according to the scan result of the temperature measurement sequence 3.

所述步骤S10中，优选的，患者在进行MR扫描前，先将一场漂校正装置安装在扫描部位周围的合适区域，如头部四周。该场漂校正装置用于在扫描部位周围提供磁共振信号的基准参考，在分析温升时去除磁场漂移带来的影响。如图3所示。该场漂校正装置30包括：一组容器34。所述一组容器34采用非磁性材料制备。所述非磁性材料可以为尼龙，聚丙烯，有机玻璃等。所述一组容器34内装有均匀介质，例如生理盐水、琼脂凝胶、羟乙基纤维素(Hydroxy Ethyl Cellulose)凝胶等。一般的，所述均匀介质中还配有调节介质弛豫时间的物质，如CuSO₄或其他过渡金属盐，便于磁共振显像。所述容器34内的介质应保持与MR设备所在环境相同的温度。本实施例中，所述容器34为四个非磁性材料构成的塑料试管，每个试管 内装有琼脂。在安装时，可以用两根有弹性的柔软细绳36将四个试管较均匀箍在头部32四周，使四个试管的取向基本平行于刺激电极16取向，并保证电极触点18所在的测温选层包含四个试管内物质。可选择地，试管的固定方式也可以通过用可以伸缩大小的硬质架子固定。In the step S10, preferably, the patient first installs a field bleaching correction device in a suitable area around the scanning site, such as around the head, before performing the MR scanning. The field drift correction device is used to provide a reference reference for the magnetic resonance signal around the scanning site, and to remove the influence of the magnetic field drift when analyzing the temperature rise. As shown in Figure 3. The field drift correction device 30 includes a set of containers 34. The set of containers 34 are prepared from a non-magnetic material. The non-magnetic material may be nylon, polypropylene, plexiglass or the like. The set of containers 34 contains a homogeneous medium such as physiological saline, agar gel, Hydroxy Ethyl Cellulose gel or the like. Generally, the homogeneous medium is also provided with a substance that adjusts the relaxation time of the medium, such as CuSO ₄ or other transition metal salt, to facilitate magnetic resonance imaging. The medium within the container 34 should be maintained at the same temperature as the environment in which the MR device is located. In this embodiment, the container 34 is a plastic test tube composed of four non-magnetic materials, each of which is filled with agar. At the time of installation, four flexible tubes 36 can be used to evenly hoop the four tubes around the head 32 so that the orientation of the four tubes is substantially parallel to the orientation of the stimulation electrode 16 and that the electrode contacts 18 are located. The temperature measurement layer contains four in-tube materials. Alternatively, the tube can be secured by a rigid shelf that can be retracted.

一般的，扫描时先进行定位扫描序列1，大致观察感兴趣区域以及需监控的植入物所在位置。序列1可以为多个序列，用于进一步确定后续要扫描的区域。通过序列1扫描的结果，确定序列2的感兴趣区域，以及序列3需要监控的区域。以植入脑深部电刺激器***的扫描为例，通常电极触点表面温升最严重，需要重点监控，因此选取电极触点18所在的区域作为序列3的扫描区域，确定测温选层。序列2的成像选层则按照实际诊断或研究需求进行确定，这里不做限制。序列2与序列3的扫描区域与参数设置相互独立，互不干扰。可以理解，如果植入物所在位置已经提前知道，该步骤S10可以省略。In general, the scanning sequence 1 is first performed during scanning to roughly observe the region of interest and the location of the implant to be monitored. Sequence 1 can be a plurality of sequences for further determining the area to be scanned later. From the results of the sequence 1 scan, the region of interest of sequence 2, as well as the region of sequence 3 that needs to be monitored, is determined. Taking the scanning of the deep brain electric stimulator system as an example, the temperature rise of the electrode contact surface is usually the most serious, and it is necessary to focus on monitoring. Therefore, the area where the electrode contact 18 is located is selected as the scanning area of the sequence 3, and the temperature selection layer is determined. The imaging selection of sequence 2 is determined according to actual diagnostic or research needs, and no limitation is made here. The scanning area and parameter setting of sequence 2 and sequence 3 are independent of each other and do not interfere with each other. It will be appreciated that this step S10 can be omitted if the location of the implant has been known in advance.

所述步骤S11中，在序列2扫描之前，先采用测温序列3对测温选层进行一次测温扫描，得到初始温度或温度相关信息。一般的，可以使用梯度回波序列(GRE)或平面回波成像(EPI)序列作为测温序列对测温选层进行扫描，将得到的相位图作为初始的参考相位图

In the step S11, before the sequence 2 scan, the temperature measurement sequence is first used to perform temperature measurement scan on the temperature measurement layer to obtain initial temperature or temperature related information. Generally, a gradient echo sequence (GRE) or an plane echo imaging (EPI) sequence can be used as a temperature measurement sequence to scan the temperature selection layer, and the obtained phase map is used as an initial reference phase diagram.

所述在序列2扫描中穿插进行测温序列3的扫描方式如图4所示。将序列2分割为多个部分，每部分由若干个单元组成，每个单元是在一个TR时间内，包含一系列特定的射频脉冲以及梯度磁场的时序变化，并能够采集一组数据，构成序列2图像k空间的一部分。然后在序列2的首尾以及各部分之间穿插进行序列3的扫描，形成温升监控。如图4中所示，序列2由i部分组成，且每部分分别含有n₁，n₂，…，n_i个TR单元。可以理解，n₁TR+n₂TR+…+n_iTR＝t2。序列2每一部分与前一个和后一个序列3之间的时间间隔分别为Δt_1a、Δt_1b、Δt_2a、Δt_2b、…、Δt_ia、Δt_ib。特别的，如图5所示，在另一个实施例中，序列2的每一部分和序列3之间可以没有时间间隔，连续扫描。更特别的，序列3之间的间隔相等，即Δt₁＝Δt₂＝…＝Δt_i＝Δt。序列2被分割成的各部分中含有的单元数也相等，即n₁＝n₂＝…＝n_i。因为序列2的初始段可能含有与后续部分不同的匀场脉冲、翻转脉冲等，其包含的单元数也不一定是i的整数倍，因此n₁，n₂，…，n_i可以不同，Δt₁，Δt₂，…，Δt_i也可以不同。The scanning mode in which the temperature measurement sequence 3 is interspersed in the sequence 2 scan is as shown in FIG. The sequence 2 is divided into a plurality of parts, each part is composed of a plurality of units, each unit is a TR time, contains a series of specific RF pulses and a time series change of the gradient magnetic field, and can collect a set of data to form a sequence. 2 part of the image k space. A scan of sequence 3 is then interspersed between the beginning and end of sequence 2 and between the sections to form a temperature rise monitor. As shown in Fig. 4, the sequence 2 is composed of i parts, and each part contains n ₁ , n ₂ , ..., n _i TR units, respectively. It can be understood that n ₁ TR+n ₂ TR+...+n _i TR=t2. The time interval between each part of the sequence 2 and the previous and subsequent sequence 3 is Δt _1a , Δt _1b , Δt _2a , Δt _2b , ..., Δt _ia , Δt _{ib , respectively} . In particular, as shown in FIG. 5, in another embodiment, each portion of sequence 2 and sequence 3 may be scanned continuously without time intervals. More specifically, the intervals between the sequences 3 are equal, that is, Δt ₁ = Δt ₂ = ... = Δt _i = Δt. The number of cells contained in each part into which the sequence 2 is divided is also equal, that is, n ₁ = n ₂ = ... = n _i . Since the initial segment of the sequence 2 may contain shimming pulses, flipping pulses, etc. different from the subsequent portions, the number of cells included is not necessarily an integer multiple of i, so n ₁ , n ₂ , . . . , n _i may be different, Δt ₁ , Δt ₂ , . . . , Δt _i may also be different.

每次扫描完序列3都可以得到一组数据，传输至数据处理单元26进行处理，得到序列3扫描区域的温度相关信息。从第2次序列3扫描开始，每次序列3扫描的结果都可以和第1次序列3扫描的结果进行比较，并经过数据处理得到序列3扫描区域的温升分布。进而，给出此时用于评价安全性的安全指标，该安全指标可以是温升值，或热累积剂量值，常用43摄氏度的累积等效分钟数表征(CEM43，Cumulative Equivalent Minutes@43℃)，该安全指标可以是序列3扫描区域的最大值、此时推算的植入物(如电极)表面最大值、推算的某一时刻后的序列3扫描区域的最大值、推算的某一时刻后植入物(如电极)表面最大值等。根据程序设定的安全阈值判断此时磁共振扫描的安全性，及时反馈给MR控制单元24。如果安全指 标超过阈值，则所述MR控制单元24停止所述MR扫描设备22的MR扫描，否则，继续扫描。Each time the sequence 3 is scanned, a set of data can be obtained and transmitted to the data processing unit 26 for processing to obtain temperature-related information of the scan area of the sequence 3. From the second sequence of 3 scans, the results of each sequence 3 scan can be compared with the results of the first sequence 3 scan, and the temperature rise distribution of the sequence 3 scan region is obtained through data processing. Further, a safety index for evaluating safety at this time is given, which may be a temperature rise value or a thermal cumulative dose value, which is characterized by a cumulative equivalent number of minutes at 43 degrees Celsius (CEM43, Cumulative Equivalent Minutes@43 ° C), The safety indicator may be the maximum value of the scanning area of the sequence 3, the maximum surface value of the implant (such as an electrode) estimated at this time, the maximum value of the scanning area of the sequence 3 after a certain time of the estimation, and the implantation of a certain time after the calculation. The maximum value of the surface of the input (such as the electrode). The safety of the magnetic resonance scan at this time is judged according to the safety threshold set by the program, and is fed back to the MR control unit 24 in time. If safety refers to When the target exceeds the threshold, the MR control unit 24 stops the MR scan of the MR scanning device 22, otherwise, continues scanning.

图6举例表示出了序列2的分割方式。序列2可能需要扫描多层图像，每一层图像由一组k空间的数据重建得到，每一组k空间数据由多个TR单元的扫描产生，每个TR单元扫描产生k空间中的一行或几行数据。序列3可以穿插在层间，即每一层或每数层穿插一次序列3扫描。更一般的，序列2的多层图像扫描都由若干个TR单元组成。因此，序列3也可以穿插在一层图像k空间数据的行间。序列3的穿插方式可以根据n_iTR与T_slice的关系进行调节和设置。参见图7，以整个头部的轴状图扫描为例，当n_iTR>T_slice时，可以选取在成像序列得到的k空间数据层间穿插进行测温选层的测温序列3扫描的方式。假设n_iTR＝nT_slice，n为自然数。每得到n层成像图像便停止序列2的成像扫描，对测温选层进行一次测温序列3的扫描，当测温序列3扫描结束后，从上次停止的位置继续进行序列2扫描得到下一个n层成像图像后停止，然后对测温选层进行一次测温序列3的扫描，依次继续。Fig. 6 exemplifies the division of the sequence 2. Sequence 2 may need to scan a multi-layer image, each layer image is reconstructed from a set of k-space data, each set of k-space data is generated by scanning of multiple TR units, each TR unit scan producing a row in k-space or A few lines of data. Sequence 3 can be interspersed between layers, i.e., each layer or every layer is interspersed with a sequence of 3 scans. More generally, the multi-layer image scan of Sequence 2 consists of several TR units. Therefore, the sequence 3 can also be interspersed between lines of a layer of image k-space data. The interleaving of sequence 3 can be adjusted and set according to the relationship between n _i TR and T _slice . Referring to FIG. 7 , taking the axial scan of the entire head as an example, when n _i TR>T _slice , the k-space data layer obtained by the imaging sequence can be interspersed for the temperature measurement sequence of the temperature-measuring layer 3 scan. the way. Assuming n _i TR=nT _slice , n is a natural number. The imaging scan of sequence 2 is stopped every time n layers of imaged images are obtained, and the temperature measurement sequence 3 is scanned for the temperature measurement sequence 3, and after the temperature measurement sequence 3 is scanned, the sequence 2 scan is continued from the position where it was stopped last time. After an n-layer image is taken, the temperature measurement sequence 3 is scanned for the temperature measurement layer and continues.

参见图8，当n_iTR<T_slice时，或者n_iTR不是T_slice的整数倍时，需要选择在k空间数据行间穿插进行测温选层的测温序列3扫描的方式。假设成像序列的K空间共有P行，每次相位编码后采集的数据对应填到K空间的一行，即TR时间采集一行K空间数据。在成像序列的某一层的K空间采集j行后，暂停成像序列2的扫描，将K空间已经采集的数据转存到存储单元，然后开始对测温选层进行测温序列3的扫描，采集的数据实时传输到数据处理单元26获取温度分布。测温序列3扫描结束后，从第j+1行开始继续进行成像序列2扫描，采集的数据继续保存到存储单元，后续扫描过程类似。在上述扫描过程中，所述MR控制单元24实时地将采集到的数据传到所述数据处理单元26。Referring to FIG. 8, when n _i TR<T _slice , or n _i TR is not an integer multiple of T _slice , it is necessary to select a method of interpolating between k-space data lines for temperature-measurement sequence 3 scanning of the temperature-selection layer. It is assumed that the K-space of the imaging sequence has a total of P rows, and the data acquired after each phase encoding is correspondingly filled into one row of the K space, that is, a row of K-space data is acquired at the TR time. After acquiring j rows in a K-space of a certain layer of the imaging sequence, the scanning of the imaging sequence 2 is paused, the data already acquired in the K-space is transferred to the storage unit, and then the scanning of the temperature-measuring sequence 3 is started. The collected data is transmitted in real time to the data processing unit 26 to obtain a temperature distribution. After the temperature measurement sequence 3 scan ends, the imaging sequence 2 scan is continued from the j+1th line, and the collected data is continuously saved to the storage unit, and the subsequent scanning process is similar. During the above scanning process, the MR control unit 24 transmits the collected data to the data processing unit 26 in real time.

所述步骤S12中，所述数据处理单元26根据来自所述MR控制单元24的测温图像数据计算出此时温度分布情况，进而，给出此时用于评价安全性的安全指标，与事先设定的阈值比较，及时给出反馈传递到所述MR控制单元24。In the step S12, the data processing unit 26 calculates the temperature distribution at this time according to the temperature measurement image data from the MR control unit 24, and further, gives the safety index for evaluating safety at this time, and The set threshold comparison provides timely feedback to the MR control unit 24.

具体地，所述步骤S12中，所述根据测温序列3的扫描结果进行安全评估包括以下步骤：Specifically, in the step S12, the security evaluation according to the scan result of the temperature measurement sequence 3 includes the following steps:

步骤S121，确定评估区域；Step S121, determining an evaluation area;

步骤S122，确定评估区域的温升分布；Step S122, determining a temperature rise distribution of the evaluation area;

步骤S123，计算安全指标；以及Step S123, calculating a safety indicator;

步骤S124，将该安全指标与安全阈值进行比较。Step S124, comparing the security indicator with a security threshold.

所述步骤S121中，所述数据处理单元26根据序列3的数据，确定安全评估区域，主要是确定该有源植入物的伪影区域。有源植入物与生物组织的物理性质不同，主要是金属部分的磁化系数不同，导致在磁共振环境下被静磁场磁化导致周围的磁场畸变，从而造成植入物周围图像信号失真，表现为图像伪影。通常这部分区域的信号难以提取有用信息。一般的，有源植入物与磁共振的射频磁场相互作用而产生的感生电场在靠近植入物表面处最强，从而 产生的温升最高，并随着向周围热传导而逐渐降低。特别是细长导体结构的尖端，如脑深部电刺激电极触点处，更易产生温升。因此评估安全性需要确定植入物伪影周围的评估区域，尽可能靠近植入物表面温升最高处，并能从序列3的数据中提取温度信息。In the step S121, the data processing unit 26 determines the security evaluation area according to the data of the sequence 3, mainly determining the artifact area of the active implant. The physical properties of active implants are different from those of biological tissues, mainly because the magnetization coefficients of the metal parts are different, resulting in magnetization of the static magnetic field in the magnetic resonance environment, causing distortion of the surrounding magnetic field, thereby causing distortion of the image signal around the implant. Image artifacts. Often the signals in this part of the area are difficult to extract useful information. In general, the active implant interacts with the radio frequency magnetic field of magnetic resonance to produce an induced electric field that is strongest near the surface of the implant, thereby The resulting temperature rise is highest and gradually decreases as it conducts heat to the surroundings. In particular, the tip of the elongated conductor structure, such as the deep electrical stimulation electrode contacts, is more prone to temperature rise. Therefore, assessing the safety requires determining the assessment area around the implant artifacts as close as possible to the highest temperature rise of the implant surface and extracting temperature information from the data in Sequence 3.

确定过程如图9所示，利用边缘检测算法确定出伪影边缘42，优选的，可以利用canny算法，sober算法，Roberts算法确定伪影边缘42。所述伪影边缘42属于金属伪影区域40到组织信号44的过渡区，需用分类算法确定伪影边缘42像素点所属类型。优选地，可以利用贝叶斯分类算法对伪影边缘42进行分类，确定伪影边缘42所覆盖的像素点所属类别，组织信号44或者伪影区域40，这样，就从图像上把伪影区域40确定出来了。The determination process is as shown in Figure 9. The edge detection algorithm is used to determine the artifact edge 42. Preferably, the artifact edge 42 can be determined using the canny algorithm, the sober algorithm, and the Roberts algorithm. The artifact edge 42 belongs to the transition region of the metal artifact region 40 to the tissue signal 44, and the classification algorithm is used to determine the type of the pixel edge 42 artifact point. Preferably, the artifact edge 42 can be classified by using a Bayesian classification algorithm to determine the category of the pixel point covered by the artifact edge 42, the tissue signal 44 or the artifact area 40, so that the artifact area is taken from the image. 40 is determined.

所述步骤S122中，确定评估区域温升分布包括以下步骤：每次扫描完序列3，数据处理单元26接收一组数据，通过处理可以得到评估区域的温度相关信息。从第2次序列3扫描开始，每次序列3扫描的结果都可以和之前结果进行差分，得到温升分布。特别的，每次扫描和第1次序列3的扫描结果进行差分，得到相对于序列2扫描前状态的温升分布。In the step S122, determining the evaluation region temperature rise distribution includes the following steps: each time the sequence 3 is scanned, the data processing unit 26 receives a set of data, and the temperature related information of the evaluation region can be obtained through the processing. From the second sequence of 3 scans, the results of each sequence 3 scan can be differentiated from the previous results to obtain a temperature rise distribution. In particular, each scan and the scan result of the first sequence 3 are differentiated to obtain a temperature rise distribution with respect to the state before the sequence 2 scan.

所述温度相关信息依赖不同的磁共振测温方法，优选地，可以采用基于质子共振频率转移的MR测温方法得到温度分布图。测温流程包括，在实施成像序列扫描前，先进行一次测温序列3的扫描，将得到的相位图作为参考相位图

将第k次采集得到的相位图记作

第k次采集时的温度变化分布ΔT_map可根据式(3)求得，The temperature related information depends on different magnetic resonance temperature measurement methods. Preferably, the temperature distribution map can be obtained by an MR temperature measurement method based on proton resonance frequency shift. The temperature measurement process includes performing a scan of the temperature measurement sequence 3 before performing the imaging sequence scan, and using the obtained phase map as a reference phase map.

Record the phase map obtained from the kth acquisition

The temperature change distribution ΔT _map at the time of the kth acquisition can be obtained according to the formula (3).

在上述步骤中，由于磁场漂移的影响，上面求得的温度分布图可能不能准确地反映温度变化，因此，优选的，需要校正场漂引起的温度变化。如图10所示，在温度分布图中，每个场漂校正容器34对应图像的中心区域46选取若干点，将每个点的位置信息与温度变化信息存储在矩阵A(i,j,ΔT)中，用线性插值的方法求出场漂引起的伪温度变化分布图。计算过程，可以通过求解超定问题：In the above steps, the temperature profile obtained above may not accurately reflect the temperature change due to the influence of the magnetic field drift, and therefore, it is preferable to correct the temperature change caused by the field drift. As shown in FIG. 10, in the temperature profile, each field drift correction container 34 selects several points corresponding to the central area 46 of the image, and stores the position information and temperature change information of each point in the matrix A (i, j, ΔT). In the method of linear interpolation, the pseudo temperature variation profile caused by the field drift is obtained. The calculation process can be solved by solving the overdetermined problem:

其中，[i j 1]_n×3的第一列为A(:,1)，第二列为A(:,2)，第三列全是1。上述问题的超定解得到了最小二乘意义下的线性插值结果z＝a·i+b·j+c，将原始温度变化分布图减去z，便得到了校正后的实际温度分布ΔT_correction，即，Among them, the first column of [i j 1] _n×3 is A(:,1), the second column is A(:,2), and the third column is all 1. The overdetermined solution to the above problem yields the linear interpolation result z=a·i+b·j+c in the sense of least squares. The original temperature distribution profile is subtracted by z, and the corrected actual temperature distribution ΔT _{correction is obtained.} ,which is,

ΔT_correction(i,j)＝ΔT_map(i,j)-z   (5)ΔT _correction (i,j)=ΔT _map (i,j)-z (5)

所述步骤S123中，安全指标可以是温升值，或热累积剂量值，常用43摄氏度的累积等 效分钟数表征(CEM43，Cumulative Equivalent Minutes@43℃)。该安全指标可以是评估区域的最大值，即选取步骤S122中的最大值。还可以是但不限于此时推算的植入物(如电极)表面最大值、推算的某一时刻后的评估区域的最大值、推算的某一时刻后植入物(如电极)表面最大值等。In the step S123, the safety indicator may be a temperature rise value, or a thermal cumulative dose value, and the accumulation of 43 degrees Celsius is commonly used. Characterization of the number of minutes (CEM43, Cumulative Equivalent Minutes@43 ° C). The security indicator may be the maximum value of the evaluation area, that is, the maximum value in step S122 is selected. It may also be, but is not limited to, the maximum surface value of the implant (such as an electrode) estimated at this time, the maximum value of the evaluation area after a certain time of the estimation, and the maximum surface value of the implant (such as an electrode) after a certain time. Wait.

安全指标的推算方法包括根据实验得到的经验表格或经验公式，或者根据温升的传热规律，用近似拟合的方法或者数值分析的方法得到。The calculation method of the safety index includes an empirical table or an empirical formula obtained according to the experiment, or an approximate fitting method or a numerical analysis method according to the heat transfer law of the temperature rise.

由于伪影区域40内的信噪比很低，伪影区内40的温度数据不可靠，需要借助伪影区内40外面的温度反推求得伪影区域40内的温度变化。一般地，选取伪影边缘外42一定范围内的像素点温度信息作为边界条件，将每个像素点的位置信息和温度变化信息分别存入矩阵r＝(r₁,r₂,...r_m)和p_k＝(T_k1,T_k2,...,T_km)，其中r_m表示第m个像素点的位置信息，T_km表示第m个像素点第k次测量得到的温度变化。将第k次测量结合前k-1次测量得到的温度数据存入一个矩阵P，Since the signal-to-noise ratio in the artifact area 40 is very low, the temperature data in the artifact area 40 is unreliable, and the temperature variation in the artifact area 40 needs to be reversed by the temperature outside the artifact area 40. Generally, the pixel point temperature information within a certain range outside the edge of the artifact is selected as a boundary condition, and the position information and temperature change information of each pixel point are respectively stored in the matrix r=(r ₁ , r ₂ , .r _m ) and p _k =(T _k1 , T _k2 , . . . , T _km ), where r _m represents position information of the mth pixel point, and T _km represents temperature change of the kth measurement of the mth pixel point . The temperature data obtained by combining the kth measurement with the previous k-1 measurements is stored in a matrix P,

电磁仿真软件建立的热扩散仿真模型，以有源植入物导电部分-组织界面处电流密度J作为参数可以得到不同加热模式下的热扩散规律。本实施例中，以J₀＝1000作为标准热扩散模型，计算出位置在r＝(r₁,r₂,...r_m)，对应于k次扫描时刻的温度变化矩阵st_P，The thermal diffusion simulation model established by the electromagnetic simulation software can obtain the thermal diffusion law under different heating modes by using the current density J at the conductive part-tissue interface of the active implant as a parameter. In this embodiment, J ₀ =1000 is used as the standard thermal diffusion model, and the position is calculated as r = (r ₁ , r ₂ , ... r _m ), corresponding to the temperature change matrix st_P of k times of scanning,

可以理解，st_P(i,j)代表标准扩散模型中位置在r_j对应第i次扫描时刻的温度变化值。根据式ΔT＝a·J²可得到，It can be understood that st_P(i,j) represents the temperature change value of the position in the standard diffusion model corresponding to the i-th scanning time at r _j . According to the formula ΔT=a·J ² ,

此处，ΔT₁＝P,ΔT₀＝st_P，需在最小二乘意义下求得λ，即需求式 Here, ΔT ₁ =P, ΔT ₀ =st_P, λ is to be obtained in the sense of least squares, ie demand

的最小值，令上式求导等于零便可求得极值点

的值，The minimum value, so that the above formula is equal to zero, the extreme point can be obtained.

Value,

将

带入到热扩散仿真模型st_P(i,j)便得到了实验对应的热扩散模型，从模型中可以提取出温升最高点的温度变化曲线。所述温升最高点的温度变化曲线即组织界面温度变化曲线。will

Bringing into the thermal diffusion simulation model st_P(i,j), the thermal diffusion model corresponding to the experiment is obtained, and the temperature variation curve of the highest temperature rise point can be extracted from the model. The temperature change curve of the highest temperature rise point is the tissue interface temperature change curve.

进一步，根据所述组织界面温度变化曲线可以得到扫描时间范围内对应的热累积量和最高温升ΔT_max。可以理解，热损伤不仅取决于温度的高低，更重要的取决于温度持续时间，即所谓的热累积量。比较常用的热累积量模型为CEM₄₃，其计算公式为，Further, according to the tissue interface temperature change curve, a corresponding heat accumulation amount and a highest temperature rise ΔT _{max in the} scan time range can be obtained. It can be understood that the thermal damage depends not only on the temperature but also on the temperature duration, the so-called heat accumulation. The more commonly used thermal cumulant model is CEM ₄₃ , which is calculated as

其中，当T(t)＞43℃时，R＝0.5；当T(t)＜43℃时，R＝0.25。Wherein, when T(t)>43°C, R=0.5; when T(t)<43°C, R=0.25.

所述步骤S124中，将计算得到的热累积量CEM₄₃与事先设定的阈值threshold_CEM₄₃比较，同时比较最高温升ΔT_max与事先设定的最高温升阈值threshold_ΔT_max，两者之中任何一个超过阈值，所述数据处理单元26及时向所述MR控制单元24发出危险预警，自动停止MR扫描设备22的扫描。In the step S124, the calculated heat accumulation amount CEM _{43 is} compared with the threshold value threshold_CEM ₄₃ set in advance, and the highest temperature rise ΔT _{max is} compared with the preset highest temperature rise threshold value threshold_ΔT _max , either of them. When the threshold is exceeded, the data processing unit 26 issues a danger warning to the MR control unit 24 in time to automatically stop the scanning of the MR scanning device 22.

以上已经给出了本申请的多个实施方式，可以理解的是，在不偏离本公开内容精神以及范围的情况下，可以做出各种变化、替换、以及改变，这些实施方式也在本申请的保护范围内。 The various embodiments of the present application have been described above, and it is understood that various changes, substitutions and changes may be made without departing from the spirit and scope of the disclosure. Within the scope of protection.

Claims (13)

1. 一种监测有源植入物周围组织温度的方法，该方法基于磁共振测温技术且采用一磁共振成像***；该磁共振成像***至少包括一种用于临床检查或科学研究或其他目用途的序列2和一种用于测量温度分布的序列3；该方法包括以下步骤：A method of monitoring tissue temperature around an active implant, the method being based on magnetic resonance thermometry and employing a magnetic resonance imaging system; the magnetic resonance imaging system comprising at least one for clinical examination or scientific research or other purposes Sequence 2 and a sequence 3 for measuring the temperature distribution; the method comprises the steps of:

   步骤S11，采用序列2进行扫描，并在序列2中穿插进行测温序列3的扫描；以及Step S11, scanning is performed using sequence 2, and scanning of temperature measurement sequence 3 is interspersed in sequence 2;

   步骤S12，根据测温序列3的扫描结果进行安全评估。In step S12, the security evaluation is performed according to the scan result of the temperature measurement sequence 3.
2. 根据权利要求1所述的监测有源植入物周围组织温度的方法，其特征在于，所述采用序列2进行扫描，并在序列2中穿插进行测温序列3的扫描的方法包括：将序列2分割为i个部分，且每部分分别含有n₁，n₂，…，n_i个TR单元，其中，TR为序列2中两个激发脉冲间的间隔时间；在序列2的首尾以及各部分之间穿插进行序列3的扫描，且序列2每一部分与前一个和后一个序列3之间的时间间隔分别为Δt_1a、Δt_1b、Δt_2a、Δt_2b、…、Δt_ia、Δt_ib。The method for monitoring tissue temperature around an active implant according to claim 1, wherein said scanning with sequence 2 and interspersing in sequence 2 for scanning of temperature measuring sequence 3 comprises: 2 is divided into i parts, and each part contains n ₁ , n ₂ , ..., n _i TR units, where TR is the interval between two excitation pulses in sequence 2; at the beginning and end of sequence 2 and each part The scan of sequence 3 is interspersed, and the time interval between each part of sequence 2 and the previous and next sequence 3 is Δt _1a , Δt _1b , Δt _2a , Δt _2b , ..., Δt _ia , Δt _{ib , respectively} .
3. 根据权利要求2的监测有源植入物周围组织温度的方法，其特征在于，所述时间间隔Δt_1a、Δt_1b、Δt_2a、Δt_2b、…、Δt_ia、Δt_ib均为零；且相邻序列3之间的间隔相等。A method of monitoring tissue temperature around an active implant according to claim 2, wherein said time intervals Δt _1a , Δt _1b , Δt _2a , Δt _2b , ..., Δt _ia , Δt _ib are all zero; The intervals between adjacent sequences 3 are equal.
4. 根据权利要求2所述的监测有源植入物周围组织温度的方法，其特征在于，所述采用序列2进行扫描包括扫描多层图像，每一层图像由一组k空间的数据重建得到，每一组k空间数据由多个TR单元的扫描产生，每个TR单元扫描产生k空间中的一行或几行数据；当n_iTR>T_slice时，选择在成像序列得到的k空间数据层间穿插进行测温选层的测温序列3扫描的方式；当n_iTR<T_slice时，或者n_iTR不是T_slice的整数倍时，选择在k空间数据行间穿插进行测温选层的测温序列3扫描的方式；其中，T_slice为序列2扫描1层所需的时间。The method of monitoring tissue temperature around an active implant according to claim 2, wherein said scanning using sequence 2 comprises scanning a multi-layer image, each layer image being reconstructed from a set of k-space data. Each set of k-space data is generated by scanning of a plurality of TR units, each TR unit scan generating one or several rows of data in k-space; when n _i TR>T _slice , selecting a k-space data layer obtained in the imaging sequence Interpolating the temperature measurement sequence 3 of the temperature measurement layer; when n _i TR<T _slice , or n _i TR is not an integer multiple of the T _slice , interpolating between the k-space data lines for temperature measurement and selection The way the temperature measurement sequence is scanned 3; wherein the T _slice is the time required for sequence 2 to scan 1 layer.
5. 根据权利要求2所述的监测有源植入物周围组织温度的方法，其特征在于，所述在序列2的首尾以及各部分之间穿插进行序列3的扫描的方法包括：将测温序列3在序列2的扫描前的扫描得到的相位图作为参考相位图

   

   将测温序列3第k次采集得到的相位图记作

   

   第k次采集时的温度变化分布ΔT_map可根据式(3)求得，The method for monitoring tissue temperature around an active implant according to claim 2, wherein said method of interspersing the scan of sequence 3 between the beginning and the end of sequence 2 and between the portions comprises: measuring temperature sequence 3 Phase map obtained by scanning before sequence 2 as a reference phase map

   

   Record the phase map obtained by the kth acquisition of the temperature measurement sequence 3 as

   

   The temperature change distribution ΔT _map at the time of the kth acquisition can be obtained according to the formula (3).

   

   

   其中，α是温度相关的水分子化学键转移系数，B₀是静磁场强度，γ是旋磁比，TE是回波时间。Where α is the temperature-dependent chemical transfer coefficient of water molecules, B ₀ is the static magnetic field strength, γ is the gyromagnetic ratio, and TE is the echo time.
6. 根据权利要求5所述的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S12包括以下步骤：The method of monitoring tissue temperature around an active implant according to claim 5, wherein said step S12 comprises the following steps:

   步骤S121，确定评估区域； Step S121, determining an evaluation area;

   步骤S122，确定评估区域的温升分布；Step S122, determining a temperature rise distribution of the evaluation area;

   步骤S123，计算安全指标；以及Step S123, calculating a safety indicator;

   步骤S124，将该安全指标与安全阈值进行比较。Step S124, comparing the security indicator with a security threshold.
7. 根据权利要求6所述的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S121包括：利用边缘检测算法确定出伪影边缘；以及采用分类算法确定伪影边缘的像素点所属类型。The method for monitoring tissue temperature around an active implant according to claim 6, wherein the step S121 comprises: determining an artifact edge by using an edge detection algorithm; and determining a pixel point of the edge of the artifact by using a classification algorithm Type.
8. 根据权利要求7所述的监测有源植入物周围组织温度的方法，其特征在于，所述磁共振成像***还包括一种用于定位或其他与扫描用途的序列1；步骤S11之前进一步包括步骤S10，将一场漂校正装置安装在扫描部位周围的合适区域，采用序列1进行定位扫描，确定测温选层和成像选层。A method of monitoring tissue temperature around an active implant according to claim 7, wherein said magnetic resonance imaging system further comprises a sequence 1 for positioning or other use with scanning; further comprising prior to step S11 In step S10, a field drift correction device is installed in a suitable area around the scanning portion, and a sequence scan is performed using the sequence 1 to determine the temperature selection layer and the image selection layer.
9. 根据权利要求8所述的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S122包括：校正场漂引起的温度变化得到实际温度分布图像的步骤；所述校正场漂引起的温度变化得到实际温度分布图像的方法包括：在温度分布图中，每个场漂校正容器对应图像的中心区域选取若干点，将每个点的位置信息与温度变化信息存储在矩阵A(i,j,ΔT)中，用线性插值的方法求出场漂引起的伪温度变化分布图，其中计算过程通过求解超定问题The method for monitoring tissue temperature around an active implant according to claim 8, wherein said step S122 comprises: step of correcting a temperature change caused by field drift to obtain an actual temperature distribution image; said correcting field drift The method for obtaining the actual temperature distribution image includes: in the temperature distribution map, each field drift correction container selects a plurality of points corresponding to the central region of the image, and stores the position information and temperature change information of each point in the matrix A (i , j, ΔT), the linear temperature interpolation method is used to obtain the pseudo-temperature variation distribution map caused by the field drift, wherein the calculation process solves the overdetermined problem

   

   

   其中，[i j 1]_n×3的第一列为A(:,1)，第二列为A(:,2)，第三列全是1；上述问题的超定解得到最小二乘意义下的线性插值结果z＝a·i+b·j+c，将原始温度变化分布图减去z，便得到了校正后的实际温度分布ΔT_correction，即，Wherein, the first column of [i j 1] _n×3 is A(:,1), the second column is A(:,2), and the third column is all 1; the overdetermined solution of the above problem gives the least square meaning The linear interpolation result z=a·i+b·j+c, the original temperature distribution profile is subtracted by z, and the corrected actual temperature distribution ΔT _{correction is obtained} , ie,

   ΔT_correction(i,j)＝ΔT_map(i,j)-z    (5)。ΔT _correction (i, j) = ΔT _map (i, j) - z (5).
10. 根据权利要求9的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S123包括：A method of monitoring tissue temperature around an active implant according to claim 9, wherein said step S123 comprises:

    步骤S1231，选取伪影边缘外一定范围内的像素点温度信息作为边界条件，将每个像素点的位置信息和温度变化信息分别存入矩阵r＝(r₁,r₂,...r_m)和p_k＝(T_k1,T_k2,...,T_km)，其中r_m表示第m个像素点的位置信息，T_km表示第m个像素点第k次测量得到的温度变化；Step S1231: selecting pixel temperature information within a certain range outside the edge of the artifact as a boundary condition, and storing position information and temperature change information of each pixel point into the matrix r=(r ₁ , r ₂ , . . . r _m And p _k = (T _k1 , T _k2 , ..., T _km ), where r _m represents position information of the mth pixel point, and T _km represents temperature change of the kth measurement of the mth pixel point;

    步骤S1232，将第k次测量结合前k-1次测量得到的温度数据存入一个矩阵P， Step S1232, storing the temperature data obtained by combining the kth measurement and the k-1th measurement into a matrix P,

    

    

    步骤S1233，通过电磁仿真，以该有源植入物导电部分-组织界面处电流密度J作为参数，以J₀＝1000作为标准热扩散模型，计算出位置在r＝(r₁,r₂,...r_m)，对应于k次扫描时刻的温度变化矩阵st_P，Step S1233, by electromagnetic simulation, taking the current density J at the conductive portion-tissue interface of the active implant as a parameter, and J ₀ =1000 as a standard thermal diffusion model, and calculating the position at r=(r ₁ , r ₂ , ...r _m ), corresponding to the temperature change matrix st_P of k scan times,

    

    

    其中，st_P(i,j)代表标准扩散模型中位置在r_j对应第i次扫描时刻的温度变化值，根据式ΔT＝a·J²可得到，

    

    Where st_P(i,j) represents the temperature change value of the position in the standard diffusion model corresponding to the i-th scan time of r _{j ,} which can be obtained according to the formula ΔT=a·J ² ,

    

    步骤S1234，令式

    

    求导等于零便可求得极值点

    

    的值，

    

    Step S1234, the order

    

    The derivative is equal to zero to find the extreme point

    

    Value,

    

    步骤S1235，将

    

    带入到热扩散仿真模型st_P(i,j)，得到有源植入物表面的温度分布，从模型中提取出温升最高点的温度变化曲线；以及Step S1235, will

    

    Bringing into the thermal diffusion simulation model st_P(i,j), obtaining the temperature distribution of the active implant surface, and extracting the temperature change curve of the highest temperature rise point from the model;

    步骤S1236，根据所述温升最高点的温度变化曲线得到扫描时间范围内对应的热累积量和最高温升。Step S1236, obtaining a corresponding heat accumulation amount and a maximum temperature rise in the scan time range according to the temperature change curve of the highest temperature rise point.
11. 根据权利要求10所述的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S1236中，所述热累积量通过公式

    

    计算，其中，当T(t)＞43℃时，R＝0.5；当T(t)＜43℃时，R＝0.25。The method of monitoring tissue temperature around an active implant according to claim 10, wherein in said step S1236, said heat accumulation amount is passed through a formula

    

    Calculated, wherein, when T(t) > 43 ° C, R = 0.5; when T (t) < 43 ° C, R = 0.25.
12. 根据权利要求10所述的监测有源植入物周围组织温度的方法，其特征在于，所述步骤S124包括：将计算得到的热累积量与事先设定的阈值比较，同时比较最高温升与事先设定 的最高温升阈值，两者之中任何一个超过阈值，所述数据处理单元及时向所述MR控制单元发出危险预警，自动停止MR扫描设备的扫描。The method for monitoring the temperature of tissue around the active implant according to claim 10, wherein the step S124 comprises: comparing the calculated heat accumulation amount with a preset threshold value, and comparing the highest temperature rise with Set in advance The highest temperature rise threshold, either of which exceeds a threshold, the data processing unit issues a hazard warning to the MR control unit in time to automatically stop scanning of the MR scanning device.
13. 一种磁共振成像***，其包括：A magnetic resonance imaging system comprising:

    一MR扫描设备，该MR扫描设备至少包括一种用于临床检查或科学研究或其他目用途的序列2和一种用于测量温度分布的序列3；An MR scanning device comprising at least one sequence 2 for clinical examination or scientific research or other purposes of use and a sequence 3 for measuring temperature distribution;

    一MR控制单元，该MR控制单元用于控制该MR扫描设备采用序列2和序列3进行扫描；以及An MR control unit for controlling the MR scanning device to scan using sequence 2 and sequence 3;

    一数据处理单元，该数据处理单元用于处理该测温序列3的扫描结果，a data processing unit for processing the scan result of the temperature measurement sequence 3,

    其特征在于，该磁共振成像***具有监测有源植入物周围组织温度的功能，且该磁共振成像***监测有源植入物周围组织温度的方法为如权利要求1至12中任意一项所述的方法。 Characterized in that the magnetic resonance imaging system has a function of monitoring tissue temperature around the active implant, and the method of monitoring the tissue temperature around the active implant by the magnetic resonance imaging system is any one of claims 1 to 12. Said method.

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