WO2020107944A1 - 温升预测方法和装置 - Google Patents

温升预测方法和装置 Download PDF

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Publication number
WO2020107944A1
WO2020107944A1 PCT/CN2019/100406 CN2019100406W WO2020107944A1 WO 2020107944 A1 WO2020107944 A1 WO 2020107944A1 CN 2019100406 W CN2019100406 W CN 2019100406W WO 2020107944 A1 WO2020107944 A1 WO 2020107944A1
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electrode
field
temperature rise
image
specific range
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French (fr)
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万森
姜长青
丁建琦
李路明
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Tsinghua University
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Tsinghua University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems

Definitions

  • the present disclosure relates to the field of medical equipment, and in particular, to a temperature rise (temperature rise) prediction method and device.
  • IMD International Medical Device
  • DBS Deep Brain Stimulation
  • PD Parkinson’s disease
  • idiopathic tremor a chronic myeloma
  • MRI Magnetic Resonance Imaging
  • RF Radio Frequency
  • SAR Specific Absorption Rate
  • the present disclosure proposes a temperature rise prediction method for predicting the temperature rise of an electrode under a magnetic resonance imaging examination, that is, an MRI examination
  • the temperature rise prediction method includes: acquiring the MRI examining the specific range of the image around the electrode B 1; B 1 B 1 image of the image and the background in the radio frequency field of MRI compared to determine coefficients of said receiving electrode; determining the said sequence in the MRI examination to be scanned, and determines the size of the radio frequency field of the sequence, i.e., B 1 + rms; determining within the specific range of B 1 and B coefficients to the reception of the sequence 1 + rms Field; and predict the temperature rise of the electrode based on the B 1 field in the specific range.
  • the B 1 image of the background radio frequency field is any one of the following B 1 images: the specific range of B 1 without the electrode An image; and a B 1 image with a distance from the electrode outside a specific range.
  • acquiring a B 1 image of a specific range around the electrode under the MRI examination includes: acquiring B within a specific range of the tip portion of the electrode 1 image.
  • determining B 1+rms of the sequence includes: when the sequence is one, determining B 1+rms of the sequence; and in the When there are multiple sequences, the maximum value or average value of B 1+rms of multiple sequences is determined.
  • the mean square value of the ratio of the threshold value is used as the reception coefficient of the electrode, or the reciprocal of the mean square value of the ratio of the obtained ratio that is less than the second threshold value is used as the reception coefficient of the electrode, wherein the second threshold value is less than the said first threshold; and the B image B 1 field in comparison with the background radio frequency field, the B-to-average ratio of the mean square value of the field 1 and the background value of the square of the radio frequency field is calculated Is the reception coefficient of the electrode.
  • determining the B 1 field in the specific range according to the reception coefficient and B 1+rms of the sequence includes: The B 1+rms of the sequence are multiplied to determine the B 1 field in the specific range.
  • the specific range of the B 1 field for predicting the temperature rise of the electrode comprising: B of within the specific range of 1 field squaring; And predicting the temperature rise of the electrode based on the value obtained by squaring the B 1 field in the specific range.
  • the electrode is located in the implantable medical device.
  • the method before acquiring a B 1 image of a specific range around the electrode under the MRI examination, the method further includes: acquiring the position and direction of the electrode.
  • the method further includes: according to the predicted temperature of the electrode To determine whether to issue an alarm reminder.
  • the present disclosure proposes a temperature rise prediction device for predicting the temperature rise of an electrode under a magnetic resonance imaging examination, that is, an MRI examination.
  • the temperature rise prediction apparatus includes: a B 1 image acquisition unit for acquiring an image of a specific range around the electrode B at the MRI examination; receiving coefficient determining means, for the B 1 RF field image and the background in the image B of MRI contrast, To determine the receiving coefficient of the electrode; B 1+rms determination unit, used to determine the sequence to be scanned under the MRI examination, and determine the size of the RF field of the sequence, namely B 1+rms ; B 1 field The determining unit is used to determine the B 1 field in the specific range according to the receiving coefficient and B 1+rms of the sequence; and the prediction unit is used to predict the B 1 field according to the B 1 field in the specific range The temperature rise of the electrode.
  • the B 1 image of the background radio frequency field is any one of the following B 1 images: the specific range of B 1 without the electrode An image; and a B 1 image with a distance from the electrode outside a specific range.
  • the B 1 image acquisition unit is configured to: acquire a B 1 image within a specific range of the tip portion of the electrode.
  • the B 1+rms determining unit is used to: when the sequence is one, determine the B 1+rms of the sequence; and in the When there are multiple sequences, the maximum value or average value of B 1+rms of multiple sequences is determined.
  • the receiving coefficient calculation unit is used to perform any one of the following operations:
  • the B 1 field determination unit is used to: multiply the reception coefficient and B 1+rms of the sequence to determine the specific range B 1 field.
  • the prediction unit is configured to: B of within the specific range of 1 field squaring; and 1 B according to squaring field within the specific range The resulting value is used to predict the temperature rise of the electrode.
  • the electrode is located in the implantable medical device.
  • it further includes: an electrode position and direction acquisition unit, configured to acquire the position and direction of the electrode.
  • the above temperature rise prediction device further includes: an alarm unit, configured to determine whether to issue an alarm reminder according to the predicted temperature rise of the electrode.
  • the temperature rise prediction method and apparatus of the present disclosure by calculating the B 1 field of the specific range of the electrode based on the reception coefficient K and the sequence B 1+rms , and then predicting the RF induced heating situation based on the B 1 field, it is possible
  • the RF-induced heating is predicted in consideration of the shape, angle, placement position, etc. of the electrodes. Therefore, regardless of the shape, angle, placement position, etc. of the electrodes, the above-described embodiments of the present disclosure can be used to more accurately characterize RF-induced heating, thereby determining the RF-induced heating of the medical equipment equipped with electrodes under MRI examination.
  • FIG. 1 shows a flowchart of a temperature rise prediction method according to an embodiment of the present disclosure.
  • FIG. 2 shows a flowchart of a temperature rise prediction method according to another embodiment of the present disclosure.
  • FIG. 3 shows a schematic diagram of bundling the electrodes side by side with the optical fiber whose temperature is increased.
  • FIG. 4 shows a schematic diagram of a straight line obtained by fitting the value obtained by squaring the local B 1 field to the temperature rise.
  • FIG. 5 shows a schematic diagram of finite element numerical simulation for a temperature rise prediction method according to an embodiment of the present disclosure.
  • FIG. 6 shows a schematic diagram of the results of finite element numerical simulation for a temperature rise prediction method according to an embodiment of the present disclosure.
  • FIG. 7 shows a structural block diagram of a temperature rise prediction device according to an embodiment of the present disclosure.
  • FIG. 8 shows a structural block diagram of a temperature rise prediction device according to another embodiment of the present disclosure.
  • FIG. 1 shows a flowchart of a temperature rise prediction method according to an embodiment of the present disclosure.
  • the temperature rise prediction method is mainly used to predict the temperature rise of the electrode under MRI examination.
  • the temperature rise prediction method includes:
  • Step S101 Acquire a B 1 image of a specific range around the electrode under MRI examination
  • Step S102 the image and the background image B B 1 in the radio frequency field of MRI contrast to receive the K coefficient calculation electrode;
  • Step S103 Determine the sequence to be scanned under the MRI examination, and determine B 1+rms of the sequence;
  • Step S104 Determine the B 1 field within a specific range according to the reception coefficient K and B 1+rms of the sequence.
  • Step S105 Predict the temperature rise of the electrode according to the B 1 field in a specific range.
  • the first for example the patient MRI examination to obtain an image B around the electrode.
  • the electrodes are located in the implantable medical device.
  • the implantable medical device is a medical device such as a cardiac pacemaker, and can be implanted at a corresponding position in the patient's body to perform corresponding treatment on the patient or assist the normal operation of the patient's organ function.
  • the previous scan test result of the patient can also be directly obtained, whereby the B 1 image around the electrode can be obtained from the scan test result.
  • step S101 since the RF-induced heating of the electrode is mainly concentrated on the tip portion of the electrode, in step S101, the B 1 image around the tip portion of the electrode is mainly acquired.
  • the specific range may be a rectangular parallelepiped area around the electrode, and the length, width, and height of the rectangular parallelepiped area are, for example, 50 mm, 20 mm, and 20 mm, respectively.
  • the length of the rectangular parallelepiped region ranges from 10 mm to 80 mm
  • the width of the rectangular parallelepiped region ranges from 6 mm to 40 mm
  • the height of the rectangular parallelepiped region ranges from 6 mm to 40 mm, for example.
  • the specific range may be any cross section of the above-mentioned rectangular parallelepiped. The specific range is explained by way of example above, but the specific range of the present disclosure is not limited thereto, and the specific range may specifically be appropriately set according to application scenarios.
  • B 1 images within a specific range around the electrode can be acquired.
  • the acquired B 1 image can be compared with the standard interference-free image to obtain the receiving coefficient K of the electrode.
  • the standard interference-free image may be an image smaller films B by the electrodes, for example, an image in the background of MRI radio frequency field B.
  • the B 1 image of the background radio frequency field is any one of the following B 1 images: a B 1 image of a specific range without an electrode; and a range outside the specific range of the distance from the electrode B 1 image. Among them, B 1 images in a range outside this specific range are less affected by the electrodes.
  • a standard undisturbed image that is less affected by the electrodes is acquired in advance. Then, the B 1 image of the specific range acquired in the above step S101 is compared with the standard interference-free image to obtain the receiving coefficient K of the electrode.
  • the receiving coefficient K of the electrode may be calculated in the following manner.
  • the root-mean-square of the B 1 field at a position where the signal-to-noise ratio of the B 1 field around the electrode is greater than the first threshold or less than the second threshold can be used as the reception coefficient of the electrode.
  • the B 1 field in the B 1 image can be compared with the background RF field to obtain the ratio of the B 1 field to the background RF field (ie, signal-to-noise ratio), and the obtained ratio is greater than the first
  • the mean square value of the ratio of the threshold values is used as the reception coefficient K of the electrode, or the reciprocal of the mean square value of the ratio of the obtained ratio that is less than the second threshold value is used as the reception coefficient K of the electrode, where the second threshold value is smaller than the first threshold value.
  • the first threshold may be 1.2
  • the second threshold may be 0.5.
  • the specific values of the first threshold and the second threshold are not limited to this, and they may be set to other appropriate values according to specific application scenarios.
  • the receiving coefficient K of the electrode may also be calculated in the following manner. Specifically, the B 1 field in the B 1 image is compared with the background RF field to calculate the ratio of the mean square value of the B 1 field to the background RF field as the reception coefficient K of the electrode.
  • the above mentioned two specific ways to calculate the reception coefficient K those skilled in the art will be able to know, around the electrode in accordance with an image and a B image of the background B in the radio frequency field MRI examination, any There are other suitable ways to calculate the receiving coefficient K of the electrode, as long as the calculated receiving coefficient can properly reflect the influence of the shape, angle and placement position of the electrode on the RF-induced heating.
  • the shape, angle and placement of the electrode will affect the RF-induced heating of the medical device with the electrode under MRI, by comparing the B 1 image around the electrode with the standard non-interfering B 1 image, the This calculates the receiving coefficient K, which can take into account the influence of these factors on the RF-induced heating of the electrode. In this way, the reception coefficient K can be applied in subsequent steps to accurately predict RF induced heating.
  • the sequence to be scanned by the patient in this MRI examination such as the T1, T2, BOLD sequence, etc.
  • the MRI examination equipment is appropriately set to perform MRI examination on the patient according to the setting, and the size of the radio frequency field of the sequence to be scanned, that is, B 1+rms , is acquired (read out).
  • the sequence to be scanned is a situation, you may obtain the sequence B 1 + rms as required in this step B 1 + rms.
  • B 1+rms of the T1 sequence can be obtained.
  • B 1+rms of the T2 sequence can be obtained.
  • B 1+rms of the BOLD sequence can be obtained.
  • B 1+rms of these sequences can first obtain B 1+rms of these sequences separately, and then take the average or maximum value of B 1+rms in these sequences as required in this step B 1+rms .
  • B 1+rms the maximum value of B 1+rms in these sequences, that is, max(B 1+rms ), is taken as the B 1+rms required in this step, which can minimize the risk of the patient in the MRI examination.
  • B 1+rms of each sequence can also be read in advance. Then, the average and/or maximum value of B 1+rms of each sequence is stored in the memory. In this way, when the B 1+rms of the sequence needs to be obtained, the average value and/or the maximum value of the sequence can be read directly from the memory.
  • sequences such as T1 sequence, T2 sequence, and BOLD sequence and their combinations by way of example, but the present disclosure is not limited to this, the sequence may be any other sequence in the patient's body, and the scan The sequence can be any combination of any sequence.
  • the B 1 field in a specific range can be calculated according to the reception coefficient K of the electrode calculated in step S102 and the B 1+rms of the sequence obtained in step S103.
  • the temperature rise of the electrode can be predicted based on the B 1 field of the specific range calculated in step S104, thereby predicting the RF induced heating of the electrode.
  • the inventor found that there is a certain relationship between the B 1 field of the specific range of the electrode and the temperature increase of the electrode. Specifically, the square of the B 1 field in the specific range of the electrode has a linear relationship with the temperature rise of the electrode.
  • electrode B 1 field can squaring the B 1 field, and then according to the predicted value and squaring the linear relationship obtained The temperature rises, thereby predicting the RF induced heating of the electrode.
  • the electrode can be considered In the case of the shape, angle and placement position, etc., the RF induction heating is predicted. Therefore, regardless of the shape, angle, placement position, etc. of the electrodes, the above-described embodiments of the present disclosure can accurately characterize RF-induced heating, thereby determining the RF-induced heating of the medical equipment equipped with electrodes under MRI examination.
  • FIG. 2 is a flowchart illustrating a temperature rise prediction method according to another embodiment of the present disclosure.
  • the same reference numerals in FIG. 2 as those in FIG. 1 have the same meaning, and their explanation will be omitted in this embodiment.
  • the main difference between the temperature rise prediction method of this embodiment and the temperature rise prediction method of the above embodiment is that before the above step S101, the following steps may also be included:
  • Step S100 Acquire the position and direction of the electrode.
  • the patient is scanned by MRI examination, thereby locating the path position of the electrode located in the implantable medical device, and further determining the path direction of the electrode.
  • the temperature rise prediction method of this embodiment may further include the following steps after step S105:
  • Step S106 Determine whether an alarm is issued according to the predicted temperature rise of the electrode.
  • a safety threshold for the RF induction heating of the electrode it is possible to set a safety threshold for the RF induction heating of the electrode, and compare the RF induction heating of the electrode predicted in step S105 with the safety threshold.
  • the temperature rise can be used to characterize the RF-induced heat generation, and accordingly the corresponding temperature rise can be set as a safety threshold.
  • the predicted RF induced fever that is, the temperature rise is greater than or equal to the safety threshold
  • an alarm can be issued to remind the medical staff that the patient has a certain risk of performing MRI examination, so that the medical staff can terminate the MRI examination, for example.
  • the temperature rise is less than the safety threshold, it indicates that the patient can be safely subjected to MRI examination, at this time, no warning may be issued, or a reminder indicating that the MRI examination is safe may also be issued.
  • the temperature rise prediction method of this embodiment can intuitively prompt the risk of the patient in the MRI examination, thereby avoiding the harm suffered by the patient in the MRI examination as much as possible.
  • the present disclosure has explained the present disclosure with an example of predicting the temperature rise of an electrode located in an implantable medical device under MRI examination, that is, nuclear magnetic, but the present disclosure is not limited thereto, and the temperature rise prediction method of the present disclosure Electrodes in the same general medical equipment, or applied to the monopole alone. In other words, the temperature rise prediction method of the present disclosure can also predict the temperature rise of an electrode in a general medical device under nuclear magnetic field, and even predict the temperature rise of an individual electrode under nuclear magnetic field.
  • the temperature rise prediction method of the present invention will be further explained in the following experimental way.
  • FIG. 3 shows a schematic diagram of bundling the electrodes side by side with the optical fiber whose temperature is increased.
  • the agar solution was prepared by the following methods: agar was 15 g/L, CuSO 4 was 5 mmol/L, and NaCl was 1 g/L. Among them, the purpose of adding CuSO 4 is to shorten the T1 relaxation time, thereby simulating human tissue.
  • the electrodes bundled side by side perpendicular to the optical fiber so that it roughly coincides with the axis of the plastic cylinder, and adjust the height of the electrode position so that the distance between the electrode tip and the bottom surface of the plastic cylinder is about 5 cm.
  • the agar solution is slowly injected into the plastic cylinder and allowed to stand to cool and condense. Place the gel mold at room temperature for 12 hours to ensure that it reaches an equilibrium state during scanning.
  • TR (Repetition Time) 2000 ms
  • FOV (Field of View) 180 mm ⁇ 180 mm
  • slice thickness 5mm
  • slices 10
  • Sequence 2 selects the T2TSE sequence, which has a larger B 1+rms , so it can heat the electrode more effectively under the same conditions, thereby improving the signal-to-noise ratio of the result.
  • the sequence parameters are:
  • FIG. 4 shows a schematic diagram of a straight line obtained by fitting the value obtained by squaring the local B 1 field to the temperature rise. Then, the fitting analytical formula obtained from the measurement is:
  • x is the root mean square of the local B 1 field and y is the actual temperature rise.
  • the predicted temperature rise is about 6.66°C, which is less than 5% relative to the actual measured temperature of 6.35°C. That is, the temperature rise of the electrode predicted by the temperature rise prediction method according to this embodiment is very close to the actually measured temperature rise.
  • FIG. 5 shows a schematic diagram of finite element numerical simulation for a temperature rise prediction method according to an embodiment of the present disclosure.
  • An ASTM phantom is constructed to simulate the head and torso of the human body, and is located inside the center of the bird cage coil, etc., and an electrode with a diameter of 1.3 mm is located therein.
  • the four platinum iridium rings are the same as the actual DBS electrode.
  • the insulation thickness is 0.65mm, and the spiral inside the electrode is simplified as a straight line.
  • the conductivity and dielectric constant of the phantom medium were set to 0.48 s/m and 78, respectively.
  • the electrical conductivity and dielectric constant of the insulation are set to 0 and 3, respectively.
  • the origin of the coordinate is at the center of the phantom's torso. Adjust the whole body SAR without implanted phantom to 1W/kg.
  • different electrode positions and angles are simulated.
  • Electrodes with "S" curvature All bends are at least 100mm from the tip of the electrode to ensure the same range of cuboids near the tip. A point 0.3 mm away from the tip contact surface of the electrode was set as a temperature probe to evaluate the RF-induced heating.
  • the average value of the local B 1 field in the rectangular parallelepiped region near the electrode was used as a characteristic index of RF-induced heating.
  • the length, width, and height of the rectangular parallelepiped area are 50 mm, 20 mm, and 20 mm, respectively.
  • nine different electrode conditions with different shapes, angles and placement positions of electrodes were simulated.
  • the square of the average value of the local B 1 field is calculated, and the obtained value is fitted to the temperature rise of the electrode.
  • the correlation coefficient obtained by fitting is used to estimate the practicality of the local B 1 field as a representation of RF fever.
  • FIG. 6 shows a schematic diagram of the results of finite element numerical simulation for a temperature rise prediction method according to an embodiment of the present disclosure.
  • FIG. 6 a shows the local B 1 field distribution. The results show that the distribution of B 1 field is significantly affected by the shape, angle and placement of the electrode, and the distribution pattern around the electrode tip is similar.
  • the correlation between the square of the average value of the local B 1 field and the temperature increase is calculated and plotted, and the result is shown in b of FIG. 6.
  • b of FIG. 6 a strong linear correlation is shown, and the correlation coefficient R is about 0.9992, which means that even for a complex placement, the local B 1 field average is a feasible characterization index for RF-induced heating.
  • the temperature rise prediction method according to the embodiment of the present disclosure can accurately predict the RF induced heating of the electrode.
  • the temperature rise prediction device 70 is used to predict the temperature rise of the electrode under magnetic resonance imaging examination, that is, MRI examination.
  • the temperature rise prediction device 70 mainly includes: a B 1 image acquisition unit 71 for acquiring a B 1 image of a specific range around the electrode under the MRI examination; a reception coefficient calculation unit 72, B 1 B 1 image of the image and the background in the radio frequency field of MRI for comparison, to calculate the reception coefficient of the electrode; B 1 + rms determination unit 73 for determining the MRI Check the sequence to be scanned, and determine the size of the RF field of the sequence, that is, B 1+rms ; the B 1 field determination unit 74 is used to determine the value based on the reception coefficient and B 1+rms of the sequence The B 1 field in the specific range; and the prediction unit 75 for predicting the temperature rise of the electrode based on the B 1 field in the specific range.
  • the B 1 image of the background radio frequency field is any one of the following B 1 images: the B 1 image of the specific range without the electrode; and the electrode distance range outside the specified range B 1 image.
  • the B 1 image acquisition unit 71 may be used to acquire a B 1 image within a specific range of the tip portion of the electrode.
  • the B 1+rms determining unit 73 may be used to: when the sequence is one, determine the B 1+rms of the sequence; and when the sequence is multiple In this case, the maximum value or average value of B 1+rms of multiple sequences is determined.
  • the receiving coefficient calculation unit 72 is used to perform any one of the following operations: comparing the B 1 field in the B 1 image with the background RF field to obtain the B 1
  • the ratio of the field to the background RF field, and the mean square value of the ratios greater than the first threshold in the obtained ratio is used as the receiving coefficient of the electrode, or the average ratio of the ratios smaller than the second threshold in the obtained ratio
  • the reciprocal of the square value is used as the receiving coefficient of the electrode, wherein the second threshold is less than the first threshold; and the B 1 field in the B 1 image is compared with the background RF field to compare the The ratio of the mean square value of the B 1 field to the mean square value of the background radio frequency field is calculated as the reception coefficient of the electrode.
  • the B 1 field determination unit 74 is configured to multiply the reception coefficient and B 1+rms of the sequence to determine the B 1 field in the specific range.
  • the prediction unit 75 is used to: square the B 1 field in the specific range; and predict based on the value obtained by squaring the B 1 field in the specific range The temperature rise of the electrode.
  • the electrode is located in the implantable medical device.
  • the electrode can be considered In the case of the shape, angle and placement position, etc., the RF induction heating is predicted. Therefore, regardless of the shape, angle, placement position, etc. of the electrodes, the above-described embodiments of the present disclosure can accurately characterize RF-induced heating, thereby determining the RF-induced heating of the medical equipment equipped with electrodes under MRI examination.
  • FIG. 8 shows a structural block diagram of a temperature rise prediction device according to another embodiment of the present disclosure.
  • the components in FIG. 8 that are the same as those shown in FIG. 7 have the same meaning, and their explanations will be omitted here.
  • the temperature rise prediction device 80 in FIG. 8 may further include: an electrode position and direction acquisition unit 76 for acquiring the position and direction of the electrode.
  • the temperature rise prediction device 80 may further include: an alarm unit 76, configured to determine whether to issue an alarm reminder according to the predicted temperature rise of the electrode.
  • the temperature rise prediction device of this embodiment can intuitively prompt the patient's risk in the MRI examination, thereby avoiding the harm suffered by the patient in the MRI examination as much as possible.

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Abstract

一种温升预测方法和装置，用于预测电极在磁共振成像检查、即MRI检查下的温升，温升预测方法包括：获取在MRI检查下电极周围的特定范围的B1图像（S101）；将B1图像与在MRI检查下的背景射频场的B1图像进行对比，以计算电极的接收系数K（S102）；确定在MRI检查下要扫描的序列，并确定序列的射频场的大小、即B1+rms（S103）；根据接收系数K和序列的B1+rms来确定特定范围内的B1场（S104）；以及根据特定范围内的B1场来预测电极的温升（S105）。可以在考虑到电极的形状、角度和放置位置的情况下更加精确地表征RF感应发热，从而确定具备电极的医疗设备在MRI检查下的RF感应发热。

Description

温升预测方法和装置 技术领域
本公开涉及医疗设备领域，尤其涉及一种温升(温度升高)预测方法和装置。
背景技术
诸如DBS(Deep Brain Stimulation，深部脑刺激)等的IMD(Implantable Medical Device，植入式医疗设备)是一种新兴的运动障碍治疗方法。目前，IMD广泛用于PD(Parkinson’s disease，帕金森病)、肌张力障碍和特发性震颤等疾病。随着MRI(Magnetic Resonance Imaging，磁共振成像)和越来越多的植入式医疗设备的发展，使用可植入设备的MRI检查的数量正在迅速增加。然而，DBS在MRI中应用存在一定的风险，其中RF(Radio Frequency，射频)感应发热是主要潜在风险之一。
目前，SAR(Specific Absorption Rate，比吸收率)被用作表征RF感应发热的主要指标，但是不存在用于估计SAR的通用标准，并且不同MRI厂商的SAR估计方法也有所不同。另一方面，SAR的计算非常保守，对采用的序列和参数限制较大，从而导致植入诸如起搏器等的植入式医疗设备的患者无法进行常规的核磁扫描。此外，B 1+rms是用于在MRI中激发质子共振的平均RF磁场，并表征RF场的大小，并且与患者状态无关，因此目前被视为RF感应发热的新指标。然而，该指标在使用中仍然受到很多限制，这是因为B 1+rms是基于理想信号源的假设而忽略了患者对B 1场的干扰。此外，植入式医疗设备中的电极的形状、角度和放置位置等因素都可能影响RF感应发热，然而，由这些因素所产生的影响不能用SAR和B 1+rms表征。因此，利用目前的SAR和B 1+rms指标有时不能准确地表征RF感应发热。
发明内容
有鉴于此，在一个方面，本公开提出了一种温升预测方法，用于预测电极在磁共振成像检查、即MRI检查下的温升，所述温升预测方法包括：获取在所述MRI检查下所述电极周围的特定范围的B 1图像；将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以确定所述电极的接收系数；确定在所述MRI检查下要扫描的序列，并确定所述序列的射频场的大小、即B 1+rms；根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场；以及根据所述特定范围内的B 1场来预测所述电极的温升。
对于上述温升预测方法，在一种可能的实现方式中，所述背景射频场的B 1图像是以下B 1图像中任一：在无所述电极的情况下的所述特定范围的B 1图像；以及与所述电极的距离在特定范围以外的范围的B 1图像。
对于上述温升预测方法，在一种可能的实现方式中，获取在所述MRI检查下所述电极周围的特定范围的B 1图像，包括：获取所述电极的尖端部分的特定范围内的B 1图像。
对于上述温升预测方法，在一种可能的实现方式中，确定所述序列的B 1+rms包括：在所述序列为一个的情况下，确定该序列的B 1+rms；以及在所述序列为多个的情况下，确定多个序列的B 1+rms的最大值或平均值。
对于上述温升预测方法，在一种可能的实现方式中，将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以计算所述电极的接收系数包括以下方式中任一：将所述B 1图像中的B 1场与所述背景射频场进行对比以得到所述B 1场与所述背景射频场的比值，并将所得到的比值中大于第一阈值的比值的均方值作为所述电极的接收系数，或者将所得到的比值中小于第二阈值的比值的均方值的倒数作为所述电极的接收系数，其中所述第二阈值小于所述第一阈值；以及将所述B 1图像中的B 1场与所述背景射频场进行对比，以将所述B 1场的均方值与所述背景射频场的均方值的比值计算为所述电极的接收系数。
对于上述温升预测方法，在一种可能的实现方式中，根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场，包括：将所述接收系数 与所述序列的B 1+rms相乘，以确定所述特定范围内的B 1场。
对于上述温升预测方法，在一种可能的实现方式中，根据所述特定范围内的B 1场来预测所述电极的温升，包括：对所述特定范围内的B 1场求平方；以及根据对所述特定范围内的B 1场求平方所得到的值来预测所述电极的温升。
对于上述温升预测方法，在一种可能的实现方式中，所述电极位于植入式医疗设备内。
对于上述温升预测方法，在一种可能的实现方式中，在获取在所述MRI检查下所述电极周围的特定范围的B 1图像之前，还包括：获取所述电极的位置和方向。
对于上述温升预测方法，在一种可能的实现方式中，在根据所述特定范围内的B 1场来预测所述电极的温升之后，还包括：根据所预测出的所述电极的温升来判断是否发出警报提醒。
在另一方面，本公开提出了一种温升预测装置，用于预测电极在磁共振成像检查、即MRI检查下的温升，所述温升预测装置包括：B 1图像获取单元，用于获取在所述MRI检查下所述电极周围的特定范围的B 1图像；接收系数确定单元，用于将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以确定所述电极的接收系数；B 1+rms确定单元，用于确定在所述MRI检查下要扫描的序列，并确定所述序列的射频场的大小、即B 1+rms；B 1场确定单元，用于根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场；以及预测单元，用于根据所述特定范围内的B 1场来预测所述电极的温升。
对于上述温升预测装置，在一种可能的实现方式中，所述背景射频场的B 1图像是以下B 1图像中任一：在无所述电极的情况下的所述特定范围的B 1图像；以及与所述电极的距离在特定范围以外的范围的B 1图像。
对于上述温升预测装置，在一种可能的实现方式中，所述B 1图像获取单元用于：获取所述电极的尖端部分的特定范围内的B 1图像。
对于上述温升预测装置，在一种可能的实现方式中，所述B 1+rms确定单元用于：在所述序列为一个的情况下，确定该序列的B 1+rms；以及在所述序列为多个的情况下，确定多个序列的B 1+rms的最大值或平均值。
对于上述温升预测装置，在一种可能的实现方式中，所述接收系数计算单元用于进行以下操作中任一：
将所述B 1图像中的B 1场与所述背景射频场进行对比以得到所述B 1场与所述背景射频场的比值，并将所得到的比值中大于第一阈值的比值的均方值作为所述电极的接收系数，或者将所得到的比值中小于第二阈值的比值的均方值的倒数作为所述电极的接收系数，其中所述第二阈值小于所述第一阈值；以及将所述B 1图像中的B 1场与所述背景射频场进行对比，以将所述B 1场的均方值与所述背景射频场的均方值的比值计算为所述电极的接收系数。
对于上述温升预测装置，在一种可能的实现方式中，所述B 1场确定单元用于：将所述接收系数与所述序列的B 1+rms相乘，以确定所述特定范围内的B 1场。
对于上述温升预测装置，在一种可能的实现方式中，所述预测单元用于：对所述特定范围内的B 1场求平方；以及根据对所述特定范围内的B 1场求平方所得到的值来预测所述电极的温升。
对于上述温升预测装置，在一种可能的实现方式中，所述电极位于植入式医疗设备内。
对于上述温升预测装置，在一种可能的实现方式中，还包括：电极位置和方向获取单元，用于获取所述电极的位置和方向。
对于上述温升预测装置，在一种可能的实现方式中，还包括：警报单元，用于根据所预测出的所述电极的温升来判断是否发出警报提醒。
根据本公开的温升预测方法和装置，通过根据接收系数K和序列的B 1+rms来计算电极的特定范围的B 1场、然后根据该B 1场来预测RF感应发热情况，由此可以在考虑到电极的形状、角度和放置位置等的情况下预测RF感应发热。因此，无论电极的形状、角度和放置位置等如何，应用本公开的上述实施例 都可以更加精确地表征RF感应发热，从而确定具备电极的医疗设备在MRI检查下的RF感应发热。
根据下面参考附图对示例性实施例的详细说明，本公开的其它特征及方面将变得清楚。
附图说明
包含在说明书中并且构成说明书的一部分的附图与说明书一起示出了本公开的示例性实施例、特征和方面，并且用于解释本公开的原理。
图1示出根据本公开一实施例的温升预测方法的流程图。
图2示出根据本公开的另一实施例的温升预测方法的流程图。
图3示出将电极与测量温度升高的光纤并排捆绑的示意图。
图4示出将对局部B 1场求平方得到的值与温度升高进行拟合而得到的直线的示意图。
图5示出根据本公开一实施例的针对温升预测方法的有限元数值模拟的示意图。
图6示出根据本公开一实施例的针对温升预测方法的有限元数值模拟的结果的示意图。
图7示出根据本公开一实施例的温升预测装置的结构框图。
图8示出根据本公开的另一实施例的温升预测装置的结构框图。
具体实施方式
以下将参考附图详细说明本公开的各种示例性实施例、特征和方面。附图中相同的附图标记表示功能相同或相似的元件。尽管在附图中示出了实施例的各种方面，但是除非特别指出，不必按比例绘制附图。
在这里专用的词“示例性”意为“用作例子、实施例或说明性”。这里作为“示例性”所说明的任何实施例不必解释为优于或好于其它实施例。
另外，为了更好的说明本公开，在下文的具体实施方式中给出了众多的 具体细节。本领域技术人员应当理解，没有某些具体细节，本公开同样可以实施。在一些实例中，对于本领域技术人员熟知的方法、手段、元件和电路未作详细描述，以便于凸显本公开的主旨。
图1示出根据本公开一实施例的温升预测方法的流程图。其中该温升预测方法主要用于预测电极在MRI检查下的温升。如图1所示，该温升预测方法包括：
步骤S101、获取在MRI检查下电极周围的特定范围的B 1图像；
步骤S102、将该B 1图像与在MRI检查下的背景射频场的B 1图像进行对比，以计算电极的接收系数K；
步骤S103、确定在MRI检查下要扫描的序列，并确定序列的B 1+rms；
步骤S104、根据接收系数K和序列的B 1+rms来确定特定范围内的B 1场；以及
步骤S105、根据特定范围内的B 1场来预测电极的温升。
以下将具体阐述上述各步骤。
对于上述步骤S101，首先，例如对患者进行MRI检查，以获取电极周围的B 1图像。在一种可能的实现方式中，电极位于植入式医疗设备中。该植入式医疗设备是诸如为心脏起搏器等的医疗设备，并且可被植入患者体内的相应位置处，以对患者进行相应的治疗或者辅助患者器官功能的正常运行。此外，还可以直接获取之前对该患者的扫描测试结果，由此可以从该扫描测试结果中获取到电极周围的B 1图像。
在一种可能的实现方式中，由于电极的RF感应发热主要集中在电极的尖端部分，因此在步骤S101中主要获取电极的尖端部分周围的B 1图像。
在获取电极周围的B 1图像之后，从该B 1图像中提取特定范围的B 1图像(换句话说，局部B 1图像)。该特定范围可以是电极周围的长方体区域，该长方体区域的长度、宽度、高度例如分别为50mm、20mm和20mm。优选地，该长方体区域的长度的范围例如为10mm～80mm，该长方体区域的宽度的范围例如为6mm～40mm，以及该长方体区域的高度的范围例如为6mm～40mm。 此外，该特定范围还可以是上述长方体的某一个截面。以上以示例方式说明了特定范围，但是本公开的特定范围不限于此，并且该特定范围具体可以根据应用场景来适当设置。
由此，可以获取到电极周围的特定范围内的B 1图像。
对于上述步骤S102，可以将所获取到的B 1图像与标准无干扰的图像进行对比，以得到电极的接收系数K。该标准无干扰的图像可以是受电极的电影较小的B 1图像，例如是在MRI检查下的背景射频场的B 1图像。在一种可能的实现方式中，背景射频场的B 1图像是以下B 1图像中任一：在无电极的情况下的特定范围的B 1图像；以及与电极的距离在特定范围以外的范围的B 1图像。其中，在该特定范围以外的范围的B 1图像受到电极的影响较小。具体而言，在步骤S102中，预先获取受电极影响较小的标准无干扰的图像。然后，将上述步骤S101中所获取到的特定范围的B 1图像与该标准无干扰的图像进行对比，以得到电极的接收系数K。
在一种可能的实现方式中，可以利用如下方式来计算电极的接收系数K。可以将电极周围B 1场信噪比大于第一阈值或小于第二阈值的位置的B 1场均方根作为电极的接收系数。具体而言，可以将B 1图像中的B 1场与背景射频场进行对比，以得到B 1场与背景射频场的比值(即，信噪比)，并将所得到的比值中大于第一阈值的比值的均方值作为电极的接收系数K，或者将所得到的比值中小于第二阈值的比值的均方值的倒数作为电极的接收系数K，其中第二阈值小于第一阈值。例如，第一阈值可以为1.2，以及第二阈值可以为0.5。然而，第一阈值和第二阈值的具体数值不限于此，其可以根据具体的应用场景而设置成其它适当的值。
在一种可能的实现方式中，还可以利用如下方式来计算电极的接收系数K。具体而言，将B 1图像中的B 1场与背景射频场进行对比，以将B 1场的均方值与背景射频场的均方值的比值计算为电极的接收系数K。
需要说明的是，以上列举了两种计算接收系数K的具体方式，但是本领域技术人员能够知道，根据电极周围的B 1图像与在MRI检查下的背景射频场 的B 1图像，可以采用任何其它适当的方式来计算电极的接收系数K，只要所计算出的接收系数能够适当地反映电极的形状、角度和放置位置对RF感应发热的影响即可。
由于电极的形状、角度和放置位置等因素均会影响具有该电极的医疗设备在MRI检查下的RF感应发热，因此通过将电极周围的B 1图像与标准无干扰的B 1图像相比较、由此计算出接收系数K，可以考虑到这些因素对电极的RF感应发热的影响。这样，可以在后续步骤中应用接收系数K来精确地预测RF感应发热。
对于上述步骤S103，确定患者在此次MRI检查中要扫描的序列，例如T1、T2、BOLD序列等。然后，对MRI检查设备进行适当设置，以根据该设置来对患者进行MRI检查，并获取(读出)所要扫描的序列的射频场的大小，即B 1+rms。
在要扫描的序列是一个的情况下，可以获取该序列的B 1+rms作为本步骤中需要的B 1+rms。例如，在要扫描T1序列的情况下，可以获取T1序列的B 1+rms。例如，在要扫描T2序列的情况下，可以获取T2序列的B 1+rms。又如，在要扫描BOLD序列的情况下的情况下，可以获取BOLD序列的B 1+rms。
另一方面，在要扫描的序列是多个的情况下，首先可以分别获取这些序列的B 1+rms，然后取这些序列中的B 1+rms的平均值或最大值作为本步骤中需要的B 1+rms。例如，在要扫描T1序列和T2序列的情况下，可以分别获取T1序列和T2序列的B 1+rms，然后取所得到的B 1+rms的平均值或最大值作为本步骤中需要的B 1+rms。优选地，取这些序列中的B 1+rms的最大值、即max(B 1+rms)作为本步骤中需要的B 1+rms，这样可以最大限度地降低患者在MRI检查中的风险。
此外，还可以预先读取各序列的B 1+rms。然后，将各序列的B 1+rms的平均值和/或最大值存储在存储器中。这样，在需要获取序列的B 1+rms时，可以直接从存储器中读取序列的平均值和/或最大值。
需要说明的是，以上通过示例的方式列举了T1序列、T2序列和BOLD序列等几种序列以及它们的组合，但是本公开不限于此，序列可以是患者体内 的任意其它序列，并且所要扫描的序列可以是任意序列的任意组合。
由此，通过上述步骤S103，可以得到序列的B 1+rms。
对于上述步骤S104，可以根据步骤S102中所计算出的电极的接收系数K和步骤S103中所得到的序列的B 1+rms来计算特定范围的B 1场。
在一种可能的实现方式中，可以将电极的接收系数K与序列的B 1+rms相乘来计算出特定范围的B 1场(local B 1)，即local B 1＝K*B 1+rms。
对于上述步骤S105中，可以根据步骤S104中所计算出的特定范围的B 1场来预测电极的温度升高，从而预测电极的RF感应发热情况。
本发明人经过多次实验和研究发现，电极的特定范围的B 1场与电极的温度升高存在一定的关系。具体而言，电极的特定范围的B 1场的平方与电极的温度升高存在线性关系。
因此，在一种可能的实现方式中，在步骤S104中得到电极的特定范围的B 1场之后，可以对该B 1场求平方，然后根据求平方所得到的值和该线性关系来预测出温度升高，由此预测出电极的RF感应发热情况。
这样，根据上述实施例，通过根据接收系数K和序列的B 1+rms来计算电极的特定范围的B 1场、然后根据该B 1场来预测RF感应发热情况，由此可以在考虑到电极的形状、角度和放置位置等的情况下预测RF感应发热。因此，无论电极的形状、角度和放置位置等如何，应用本公开的上述实施例都可以精确地表征RF感应发热，从而确定具备电极的医疗设备在MRI检查下的RF感应发热。
图2是示出根据本公开的另一实施例的温升预测方法的流程图。图2中与图1相同的附图标记表示相同的含义，并且在本实施例中将省略其说明。
本实施例的温升预测方法与上述实施例的温升预测方法主要区别在于，在上述步骤S101之前，还可以包括以下步骤：
步骤S100、获取电极的位置和方向。
具体而言，在获取电极周围的B 1图像之前，需要先获取电极的位置和方向。例如，通过MRI检查来对患者进行扫描，由此扫描定位出位于植入式医 疗设备内的电极的路径位置，并进一步确定出该电极的路径方向。
这样，在获取到电极的位置和方向之后，可以便于获取到在MRI检查下该电极(或者该电极的尖端部分)周围部分的B 1图像。
此外，在一种可能的实现方式中，本实施例的温升预测方法在步骤S105之后，还可以包括以下步骤：
步骤S106、根据所预测出的电极的温升来判断是否发出警报提醒。
具体而言，可以针对电极的RF感应发热情况设置安全阈值，并将步骤S105中所预测出的电极的RF感应发热与该安全阈值进行比较。例如，可以用温度升高来表征RF感应发热情况，相应地可以设置相应的温度升高作为安全阈值。在所预测出的RF感应发热、即温度升高大于或等于安全阈值的情况下，可以发出警报，从而提醒医护人员该患者进行MRI检查存在一定的风险，这样医护人员例如可以终止MRI检查。另一方面，在温度升高小于安全阈值的情况下，表明可以安全地对患者进行MRI检查，这时可以不发出警告，或者也可以发出表明MRI检查安全的提醒。
需要说明的是，可以针对不同的患者设置不同的安全阈值。然而，也可以针对不同的患者设置相同的安全阈值。
这样，通过本实施例的温升预测方法，可以直观地提示患者在MRI检查中的风险，由此尽可能的避免患者在MRI检查中遭受到的危害。
需要说明的是，以上以预测位于植入式医疗设备内的电极在MRI检查、即核磁下的温升的示例来说明了本公开，但是本公开不限于此，并且本公开的温升预测方法同样一般的医疗设备内的电极、或者单独应用于单极。换句话说，通过本公开的温升预测方法，同样可以预测一般的医疗设备内的电极在核磁下的温升，甚至可以预测单独的电极在核磁下的温升。
以下将通过实验的方式来进一步阐述本发明的温升预测方法。
为了确定本公开的温升预测方法的可行性，采用体模的方法进行了验证。首先将电极与测量温度升高的光纤并排捆绑，使得光纤测温仪与电极尖端触点紧密接触。图3示出将电极与测量温度升高的光纤并排捆绑的示意图。
然后，配置琼脂溶液，配置方法为：琼脂为15g/L，CuSO 4为5mmol/L，以及NaCl为1g/L。其中，加入CuSO 4的目的是缩短T1弛豫时间，从而模拟人体组织。
然后，将并排捆绑的电极与光纤垂直悬挂，以使得其大概与塑料圆柱筒的轴线重合，并调节电极位置的高度，使电极顶端与塑料圆柱筒的底面距离约为5cm。为了防止高温使电极外层的聚氨酯管变形，在琼脂溶液的温度低于70℃之后，再将琼脂溶液缓慢注入塑料圆柱筒，并静置以待其冷却凝结。将凝胶模在室温条件下放置12小时，从而确保其在扫描时温度达到平衡状态。
之后，进行核磁实验，具体阐述如下。
将上述的琼脂模型沿着核磁共振仪的Z轴放置在体模中。然后在体模中注入凝胶，使液面达到9cm。针对核磁共振仪设置以下两种序列。序列一为B 1场测量序列，参数如下：
TR(Repetition Time，重复时间)＝2000ms，TE(Echo Time，回波时间)＝shortest(最短)，flip angle(翻转角)＝60°，FOV(Field of View，视野区域)＝180mm×180mm，slice thickness(层厚)＝5mm，slices(层数)＝10，以及dynamic scans(重复扫描次数)＝1，voxel size(体素大小)＝2.5x2.5，B 1+rms＝0.72uT(9％)。
序列二选取T2TSE序列，该序列的B 1+rms比较大，因此能够在相同的条件下对电极进行更有效的加热，从而提高结果的信噪比。该序列参数为：
TE＝90ms,flip angle＝90deg，TR＝shortest，FOV＝200×200×60，voxel size＝0.7×0.7×2，slices＝30，fast imaging mode(快速成像模式)＝TSE。
为了探究电极在不同路径形态(形状)、摆放位置、摆放角度的情况下，电极尖端的B 1场与温度升高之间的关系，设置了不同的摆放方式，如下表所示。
编号 电极位置 形态 角度
1 体模左腰部 拉直 0
2 体模左腰部 团圈 0
3 体模左腰部 直角 0
4 体模中间部分 拉直 0
5 体模中间部分 团圈 0
6 体模中间部分 拉直 30
7 体模中间部分 拉直 60
8 体模中间部分 S形 0
接着，进行数据拟合。
首先，将前7种情况局部B 1场求平方，然后与温度升高进行拟合，可以得到如图4所示的直线。图4示出将对局部B 1场求平方得到的值与温度升高进行拟合而得到的直线的示意图。然后，根据测量得到的拟合解析式为：
y＝0.2938x
其中x为局部B 1场均方根，y为实际的温升。根据第8种情况下采集得到的B 1场计算预测的温度升高约为6.66℃，这与实际测量得到的温度6.35℃接近度相对误差小于5％。也就是说，根据本实施例的温升预测方法预测出的电极的温度升高与实际测量到的温度升高非常接近。
由此可知，根据本公开的实施例的温升预测方法，可以精确地预测电极的RF感应发热情况。
以下将通过数值计算的方式来研究本公开的温升预测方法。
本研究通过有限元数值模拟。图5示出根据本公开一实施例的针对温升预测方法的有限元数值模拟的示意图。首先，构建一个八通道鸟笼线圈以产生RF场，并将RF场调整为以128MHz工作(图5的a)。构建ASTM体模以模拟人体的头部和躯干，并且位于鸟笼线圈的等的中心内部，并且直径为1.3mm 的电极位于其中。4个铂铱环与实际DBS电极相同。绝缘厚度为0.65mm，电极内部的螺旋线简化为直线。体模介质的电导率和介电常数分别设定为0.48s/m和78。绝缘的电导率和介电常数分别设定为0和3。坐标原点位于体模躯干的中心。将未植入体模的全身SAR调整为1W/kg。为了覆盖复杂的现实条件，如图5的b所示，模拟了不同的电极位置和角度。还模拟了如下的不同形状的电极(图5的c)：(i)直线放置；(ii)具有直角弯曲的电极；(iii)具有螺旋弯曲的电极；(iv)与金属外壳连接的电极；(v)具有“S”弯曲的电极。所有弯曲距离电极尖端至少100mm，以确保尖端附近的长方体范围相同。将距离电极的尖端接触面0.3mm的点设定为温度探头，以对RF感应发热进行评价。
在数据后处理中，在该研究中，如图5的d所示，电极附近的长方体区域中的局部B 1场的平均值被用作RF感应发热的表征指标。长方体区域的长度、宽度和高度分别为50mm、20mm和20mm。为了确定局部B 1作为表征指标的可行性和稳健性，模拟了电极的不同形状、角度和放置位置的9种不同电极条件。接着，计算局部B 1场平均值的平方，并将所得到的值与电极的温度升高进行拟合。通过拟合所得到的相关系数用于估计局部B 1场作为RF发热的表征的实用性。
图6示出根据本公开一实施例的针对温升预测方法的有限元数值模拟的结果的示意图。图6的a示出局部B 1场分布。结果表明，B 1场的分布受电极的形状、角度和放置位置的显着影响，而电极尖端周围的分布模式相似。接着，计算并绘制局部B 1场平均值的平方与温度升高之间的相关性，结果如图6的b所示。如图6的b所示，示出了强线性相关性，并且相关系数R约为0.9992，这意味着即使对于复杂的放置，局部B 1场平均值也是RF感应发热的可行表征指标。
由此，通过数值计算的方式，也验证了根据本公开的实施例的温升预测方法，可以精确地预测电极的RF感应发热。
图7示出根据本公开一实施例的温升预测装置的结构框图。温升预测装 置70用于预测电极在磁共振成像检查、即MRI检查下的温升。如图7所示，所述温升预测装置70主要包括：B 1图像获取单元71，用于获取在所述MRI检查下所述电极周围的特定范围的B 1图像；接收系数计算单元72，用于将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以计算所述电极的接收系数；B 1+rms确定单元73，用于确定在所述MRI检查下要扫描的序列，并确定所述序列的射频场的大小、即B 1+rms；B 1场确定单元74，用于根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场；以及预测单元75，用于根据所述特定范围内的B 1场来预测所述电极的温升。
在一种可能的实现方式中，所述背景射频场的B 1图像是以下B 1图像中任一：在无所述电极的情况下的所述特定范围的B 1图像；以及与所述电极的距离在特定范围以外的范围的B 1图像。
在一种可能的实现方式中，所述B 1图像获取单元71可以用于获取所述电极的尖端部分的特定范围内的B 1图像。
在一种可能的实现方式中，所述B 1+rms确定单元73可以用于：在所述序列为一个的情况下，确定该序列的B 1+rms；以及在所述序列为多个的情况下，确定多个序列的B 1+rms的最大值或平均值。
在一种可能的实现方式中，所述接收系数计算单元72用于进行以下操作中任一：将所述B 1图像中的B 1场与所述背景射频场进行对比以得到所述B 1场与所述背景射频场的比值，并将所得到的比值中大于第一阈值的比值的均方值作为所述电极的接收系数，或者将所得到的比值中小于第二阈值的比值的均方值的倒数作为所述电极的接收系数，其中所述第二阈值小于所述第一阈值；以及将所述B 1图像中的B 1场与所述背景射频场进行对比，以将所述B 1场的均方值与所述背景射频场的均方值的比值计算为所述电极的接收系数。
在一种可能的实现方式中，所述B 1场确定单元74用于将所述接收系数与所述序列的B 1+rms相乘，以确定所述特定范围内的B 1场。
在一种可能的实现方式中，所述预测单元75用于：对所述特定范围内的B 1场求平方；以及根据对所述特定范围内的B 1场求平方所得到的值来预测所 述电极的温升。
在一种可能的实现方式中，所述电极位于植入式医疗设备内。
根据本公开的实施例的温升预测装置70的具体实现方法详见上述实施例中所阐述的温升预测方法，这里不再赘述。
这样，根据上述实施例，通过根据接收系数K和序列的B 1+rms来计算电极的特定范围的B 1场、然后根据该B 1场来预测RF感应发热情况，由此可以在考虑到电极的形状、角度和放置位置等的情况下预测RF感应发热。因此，无论电极的形状、角度和放置位置等如何，应用本公开的上述实施例都可以精确地表征RF感应发热，从而确定具备电极的医疗设备在MRI检查下的RF感应发热。
图8示出根据本公开的另一实施例的温升预测装置的结构框图。图8中与图7所示的组件相同的组件具有相同的含义，这里将省略其说明。
如图8所示，图8中的温升预测装置80与图7中的温升预测装置70的主要区别在于，除了图7中的温升预测装置70的组件以外，所述温升预测装置80还可以包括：电极位置和方向获取单元76，用于获取所述电极的位置和方向。
在一种可能的实现方式中，所述温升预测装置80还可以包括：警报单元76，用于根据所预测出的所述电极的温升来判断是否发出警报提醒。
根据本公开的实施例的温升预测装置80的具体实现方法详见上述实施例中所阐述的温升预测方法，这里不再赘述。
这样，通过本实施例的温升预测装置，可以直观地提示患者在MRI检查中的风险，由此尽可能的避免患者在MRI检查中遭受到的危害。
以上已经描述了本公开的各实施例，上述说明是示例性的，并非穷尽性的，并且也不限于所披露的各实施例。在不偏离所说明的各实施例的范围和精神的情况下，对于本技术领域的普通技术人员来说许多修改和变更都是显而易见的。本文中所用术语的选择，旨在最好地解释各实施例的原理、实际应用或对市场中的技术的技术改进，或者使本技术领域的其它普通技术人员能理解本文披露的各实施例。

Claims (10)

  1. 一种温升预测方法，用于预测电极在磁共振成像检查、即MRI检查下的温升，其特征在于，所述温升预测方法包括：
    获取在所述MRI检查下所述电极周围的特定范围的B 1图像；
    将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以计算所述电极的接收系数；
    确定在所述MRI检查下要扫描的序列，并确定所述序列的射频场的大小、即B 1+rms；
    根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场；以及
    根据所述特定范围内的B 1场来预测所述电极的温升。
  2. 根据权利要求1所述的温升预测方法，其特征在于，所述背景射频场的B 1图像是以下B 1图像中任一：在无所述电极的情况下的所述特定范围的B 1图像；以及与所述电极的距离在特定范围以外的范围的B 1图像。
  3. 根据权利要求1所述的温升预测方法，其特征在于，获取在所述MRI检查下所述电极周围的特定范围的B 1图像，包括：
    获取所述电极的尖端部分的特定范围内的B 1图像。
  4. 根据权利要求1所述的温升预测方法，其特征在于，确定所述序列的B 1+rms包括：
    在所述序列为一个的情况下，确定该序列的B 1+rms；以及
    在所述序列为多个的情况下，确定多个序列的B 1+rms的最大值或平均值。
  5. 根据权利要求1所述的温升预测方法，其特征在于，将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以计算所述电极的接收系数包括以下方式中任一：
    将所述B 1图像中的B 1场与所述背景射频场进行对比以得到所述B 1场与所述背景射频场的比值，并将所得到的比值中大于第一阈值的比值的均方值作为所述电极的接收系数，或者将所得到的比值中小于第二阈值的比值的均方值的倒数作为所述电极的接收系数，其中所述第二阈值小于所述第一阈值； 以及
    将所述B 1图像中的B 1场与所述背景射频场进行对比，以将所述B 1场的均方值与所述背景射频场的均方值的比值计算为所述电极的接收系数。
  6. 根据权利要求1所述的温升预测方法，其特征在于，根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场，包括：
    将所述接收系数与所述序列的B 1+rms相乘，以确定所述特定范围内的B 1场。
  7. 根据权利要求1所述的温升预测方法，其特征在于，根据所述特定范围内的B 1场来预测所述电极的温升，包括：
    对所述特定范围内的B 1场求平方；以及
    根据对所述特定范围内的B 1场求平方所得到的值来预测所述电极的温升。
  8. 根据权利要求1所述的温升预测方法，其特征在于，所述电极位于植入式医疗设备内。
  9. 根据权利要求1至8中任一项所述的温升预测方法，其特征在于，在根据所述特定范围内的B 1场来预测所述电极的温升之后，还包括：
    根据所预测出的所述电极的温升来判断是否发出警报提醒。
  10. 一种温升预测装置，用于预测电极在磁共振成像检查、即MRI检查下的温升，其特征在于，所述温升预测装置包括：
    B 1图像获取单元，用于获取在所述MRI检查下所述电极周围的特定范围的B 1图像；
    接收系数计算单元，用于将所述B 1图像与在所述MRI检查下的背景射频场的B 1图像进行对比，以计算所述电极的接收系数；
    B 1+rms确定单元，用于确定在所述MRI检查下要扫描的序列，并确定所述序列的射频场的大小、即B 1+rms；
    B 1场确定单元，用于根据所述接收系数和所述序列的B 1+rms来确定所述特定范围内的B 1场；以及
    预测单元，用于根据所述特定范围内的B 1场来预测所述电极的温升。
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