WO2021072640A1 - 化学交换特征定量方法及设备 - Google Patents

化学交换特征定量方法及设备 Download PDF

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WO2021072640A1
WO2021072640A1 PCT/CN2019/111267 CN2019111267W WO2021072640A1 WO 2021072640 A1 WO2021072640 A1 WO 2021072640A1 CN 2019111267 W CN2019111267 W CN 2019111267W WO 2021072640 A1 WO2021072640 A1 WO 2021072640A1
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cest
signal
theoretical
chemical exchange
saturation pulse
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PCT/CN2019/111267
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English (en)
French (fr)
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吴垠
刘洁
郑海荣
刘新
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深圳先进技术研究院
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Publication of WO2021072640A1 publication Critical patent/WO2021072640A1/zh

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    • 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
    • G01R33/483—NMR imaging systems with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy
    • G01R33/485—NMR imaging systems with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy based on chemical shift information [CSI] or spectroscopic imaging, e.g. to acquire the spatial distributions of metabolites

Definitions

  • This application relates to the field of biomedical engineering, in particular to a method and equipment for chemical exchange of specific quantities.
  • CEST imaging is a kind of magnetic resonance molecular imaging method, based on the chemical exchange of exchangeable protons and water molecules in the endogenous or exogenous CEST contrast agent, which can obtain the organism non-invasively
  • Micro-level information such as tissue energy metabolism, acid-base environment, and contrast agent content has important research value and application potential in disease identification, diagnosis, and evaluation.
  • CEST contrast agents include the body's own metabolites and exogenous contrast agents; among them, the representative endogenous CEST contrast agents include protein, creatine, glucose, etc., which can reflect cell composition, acid-base environment, energy metabolism and intake, etc.
  • Important information: Exogenous CEST contrast agents are mainly derived from synthetic compounds.
  • CEST contrast agent imaging includes asymmetry analysis method, three-point method, high-order polynomial fitting method and so on.
  • these methods need to find a reference signal when calculating the CEST effect, and the reference signal easily contains other CEST effects, so when calculating the CEST signal reflecting the strength of the CEST effect, it is susceptible to other CEST effects, which leads to a variety of CEST contrast agents.
  • the quantitative accuracy of chemical exchange features is low.
  • the embodiments of the present application provide a chemical exchange feature quantitative method and device, which can solve the problem of low quantitative accuracy of the chemical exchange feature of the CEST contrast agent in the prior art.
  • the embodiments of the present application provide a chemical exchange characteristic quantitative method, which includes: collecting the measured signal intensity of each CEST signal of a plurality of chemical exchange saturation transfer CEST contrast agents to be detected in a target object; wherein the CEST signal is Generated when a saturation pulse is applied to the resonance frequency of the CEST contrast agent under preset conditions; based on the quantitative range of theoretical chemical exchange characteristics corresponding to each CEST contrast agent, multiple signal intensity theories corresponding to the respective CEST signal of each CEST contrast agent are calculated
  • the theoretical value of the signal intensity of each CEST signal is the same as the saturation pulse parameter, resonance frequency and the actual measured value of the signal intensity when calculating the theoretical value of the signal intensity; the CEST signal corresponding to each CEST contrast agent
  • the measured signal intensity value of the signal intensity is matched with the corresponding multiple theoretical signal intensity values, and the theoretical chemical exchange characteristic corresponding to the signal intensity theoretical value with the highest matching degree is quantified as the quantitative result of the chemical exchange characteristic of the CEST contrast agent.
  • the method before collecting the measured signal intensity values of the respective CEST signals of the various chemical exchange saturation transfer CEST contrast agents to be detected in the target object, the method further includes:
  • the parameter in the effective imaging range is the saturation pulse parameter; determine the saturation pulse parameter range of the saturation pulse according to the effective imaging range of all CEST contrast agents; Among them, the saturation pulse parameter in the saturation pulse parameter range belongs to the effective imaging range of each CEST contrast agent.
  • the preset conditions are:
  • At least one saturation pulse is applied in sequence, and each saturation pulse parameter is randomized within the set saturation pulse parameter range.
  • the acquisition of the measured signal intensity values of the respective CEST signals of the various chemical exchange saturation transfer CEST contrast agents to be detected in the target object includes: according to the resonance frequencies of the various CEST contrast agents , Determine the frequency range of the saturation pulse to be applied; among them, the frequency in the frequency range of the saturation pulse covers the resonance frequency of each CEST contrast agent; select multiple frequencies from the frequency range of the saturation pulse, and the multiple frequencies include each CEST contrast agent
  • the saturation pulse is applied at each of the multiple frequencies under preset conditions, the measured value of the signal strength of the CEST signal corresponding to each frequency is collected; the measured value of the signal strength of the CEST signal corresponding to each frequency , Extract the measured value of the signal intensity of the CEST signal corresponding to the resonance frequency of each CEST contrast agent as the measured value of the signal intensity of the CEST signal of the CEST contrast agent.
  • quantifying the magnetization transfer effect of the target object to obtain a quantitative result of the chemical exchange characteristics of the magnetization transfer effect includes:
  • the calculation of multiple theoretical signal strength values corresponding to the magnetization transfer signal includes:
  • the second generation condition corresponding to the magnetization transfer signal includes the information far away from free water and the resonance frequency of all CEST contrast agents, and the corresponding saturation pulse parameters when the saturation pulse is applied; determine the theoretical chemical exchange characteristics of the magnetization transfer signal Quantitative range: Based on the quantification of different theoretical chemical exchange characteristics in the quantitative range of theoretical chemical exchange characteristics, multiple theoretical values of signal intensity corresponding to the magnetization transfer signal generated under the second generation condition are calculated.
  • the saturation pulse parameter includes any one or a combination of more than one of pulse intensity, duration, flip angle, and duty cycle.
  • an embodiment of the present application provides a chemical exchange feature quantification device, including:
  • the first acquisition module is used to acquire the measured signal intensity values of the respective CEST signals of the various chemical exchange saturation transfer CEST contrast agents to be detected in the target object; wherein, the CEST signal is in accordance with the preset conditions on the resonance frequency of the CEST contrast agent Generated when a saturation pulse is applied; the first calculation module is used to calculate multiple theoretical values of signal intensity corresponding to the respective CEST signal of each CEST contrast agent based on the quantitative range of theoretical chemical exchange characteristics corresponding to each CEST contrast agent; where, each The theoretical value of the signal intensity of each CEST signal is the same as the saturation pulse parameter and resonance frequency corresponding to the actual value of the signal intensity when calculating the theoretical value of the signal intensity; the first matching module is used to assign each CEST contrast agent to its corresponding saturation pulse parameter and resonance frequency.
  • the measured signal intensity value of the CEST signal is matched with its corresponding multiple theoretical signal intensity values, and the theoretical chemical exchange characteristic corresponding to the signal intensity theoretical value with the highest matching degree is quantified as the quantitative result of the chemical exchange characteristic of the CEST contrast
  • the chemical exchange characteristic quantitative device further includes:
  • the first setting module is used to determine the effective imaging range of each CEST contrast agent according to the chemical exchange characteristics of each CEST contrast agent; the parameters in the effective imaging range are saturated pulse parameters; the second setting module is used to determine the effective imaging range of each CEST contrast agent
  • the effective imaging range of the contrast agent determines the saturation pulse parameter range of the saturation pulse; among them, the saturation pulse parameter in the saturation pulse parameter range belongs to the effective imaging range of each CEST contrast agent.
  • the preset condition is that at least one saturation pulse is applied in sequence, and each saturation pulse parameter is randomized within the set saturation pulse parameter range.
  • the first collection module includes:
  • the frequency range setting unit is used to determine the frequency range of the saturation pulse to be applied according to the resonance frequency of a variety of CEST contrast agents; wherein the frequency in the frequency range of the saturation pulse covers the resonance frequency of each CEST contrast agent; frequency selection unit , Used to select multiple frequencies from the frequency range of the saturation pulse, the multiple frequencies include the resonance frequency of each CEST contrast agent; the first acquisition sub-unit is used to apply preset conditions on each of the multiple frequencies When the pulse is saturated, the measured value of the signal intensity of the CEST signal corresponding to each frequency is collected; the extraction unit is used to extract the CEST corresponding to the resonance frequency of each CEST contrast agent from the measured value of the signal intensity of the CEST signal corresponding to each frequency The measured signal intensity of the signal is taken as the measured signal intensity of the CEST signal of the CEST contrast agent.
  • chemical exchange characteristic quantitative device further includes:
  • the quantification module is used to quantify the magnetization transfer effect of the target object, and obtain the quantitative results of the chemical exchange characteristics of the magnetization transfer effect;
  • the first calculation module includes:
  • the first acquisition unit is used to acquire the first generation condition corresponding to the CEST signal of each CEST contrast agent, the first generation condition includes the resonance frequency of the CEST contrast agent and the corresponding saturation pulse parameter when the saturation pulse is applied;
  • the first determination unit Used to determine the quantitative range of theoretical chemical exchange characteristics of each CEST contrast agent;
  • the first calculation subunit is used to quantify different theoretical chemical exchange characteristics based on the quantitative range of theoretical chemical exchange characteristics, and quantify chemical exchange characteristics using the magnetization transfer effect As a result, multiple theoretical values of signal strength corresponding to the CEST signal generated under the first generation condition are calculated.
  • the quantization module includes:
  • the second acquisition module is used to acquire the actual measured value of the signal intensity of the magnetization transfer signal collected when the saturation pulse is applied according to the preset conditions at the resonance frequency of the free water and all CEST contrast media.
  • the second calculation module is used to The quantitative range of the theoretical chemical exchange characteristics of the magnetization transfer signal is calculated, and the multiple theoretical values of the signal intensity corresponding to the magnetization transfer signal are calculated; among them, the saturation pulse parameters and resonance frequency corresponding to the signal intensity of the magnetization transfer signal are calculated with the generated magnetization
  • the second matching module is used to match the actual measured value of the signal strength of the magnetization transfer signal with its corresponding multiple theoretical signal strength values to match the degree of match
  • the theoretical chemical exchange characteristic quantification corresponding to the highest theoretical value of the signal intensity is the quantitative result of the chemical exchange characteristic of the magnetization transfer effect of the target object.
  • the second calculation module includes:
  • the second acquisition unit is used to acquire the second generation condition corresponding to the magnetization transfer signal, the second generation condition includes the information far away from free water and the resonance frequency of all CEST contrast agents, and the corresponding saturation pulse parameters when the saturation pulse is applied;
  • the determination unit is used to determine the theoretical chemical exchange characteristic quantitative range of the magnetization transfer signal;
  • the second calculation subunit is used to quantify different theoretical chemical exchange characteristics in the theoretical chemical exchange characteristic quantitative range, and calculate the generated under the second generation condition Multiple theoretical values of signal intensity corresponding to the magnetization transfer signal.
  • this application provides a chemical exchange characteristic quantification device, including a memory, a processor, and computer-readable instructions stored in the memory and running on the processor.
  • the processor implements the first The quantitative method of chemical exchange characteristics described in the aspect.
  • the present application provides a computer-readable storage medium that stores computer-readable instructions, and the computer-readable instructions implement the chemical exchange feature quantification method described in the first aspect when the computer-readable instructions are executed by a processor.
  • this application provides a computer-readable instruction product, when the computer-readable instruction product runs on a chemical exchange feature quantification device, the chemical exchange feature quantification device executes the chemical exchange feature quantification method described in the first aspect A step of.
  • the actual signal intensity value of the CEST signal of each CEST contrast agent is calculated.
  • the theoretical value of the signal intensity is calculated, the actual measurement value of the signal intensity is the same as the acquisition environment at the time of acquisition, that is, the saturation pulse parameter and the resonance frequency are the same. Therefore, based on the quantitative range of theoretical chemical exchange characteristics, multiple theoretical signal strength values corresponding to the measured signal strength can be calculated; the theoretical signal strength value is calculated under the same acquisition environment as the actual measured signal strength value. Value, the one-to-many matching method is adopted to make the measured value of signal strength have a more accurate matching result.
  • the chemical exchange characteristic quantification process of this application does not need to select a reference signal and is not easily affected by other chemical exchange effects, so that the theoretical chemical exchange characteristic quantification corresponding to the matching result can more accurately represent the actual chemical exchange specific amount, so this application is effective This improves the accuracy of chemical exchange for a specific amount.
  • Fig. 1 is a schematic flow chart of a chemical exchange feature quantification method provided by an embodiment of the present application
  • Figure 2 is a schematic diagram of the CEST signal generated after a saturation pulse is applied
  • FIG. 3 is a schematic flowchart of S101 provided by an embodiment of the present application.
  • FIG. 4 is a schematic flowchart of S102 provided by an embodiment of the present application.
  • FIG. 5 is a schematic flowchart of quantifying the magnetization transfer effect of a target object provided by an embodiment of the present application
  • FIG. 6 is a schematic flowchart of calculating multiple theoretical signal strength values corresponding to a magnetization transfer signal provided by an embodiment of the present application
  • FIG. 7 is a variation curve of multiple measured signal strength values of the CEST signal calculated in an embodiment of the present application as a function of the saturation pulse sequence number;
  • Fig. 8 is a variation curve of the measured value of the signal intensity of the CEST signal collected by an embodiment of the present application with the sequence number of the saturation pulse;
  • FIG. 9 is a matching result of the change curve in FIG. 8 with multiple change curves in FIG. 7;
  • FIG. 10 is a structural block diagram of a chemical exchange feature quantification device provided by an embodiment of the present application.
  • FIG. 11 is a structural block diagram of the first acquisition module in an embodiment of the present application.
  • Fig. 12 is a structural block diagram of a first calculation module in an embodiment of the present application.
  • FIG. 13 is a structural block diagram of a quantization module in an embodiment of the present application.
  • Fig. 14 is a schematic diagram of a chemical exchange feature quantification device provided by an embodiment of the present application.
  • the term “if” can be construed as “when” or “once” or “in response to determination” or “in response to detecting “.
  • the phrase “if determined” or “if detected [described condition or event]” can be interpreted as meaning “once determined” or “in response to determination” or “once detected [described condition or event]” depending on the context ]” or “in response to detection of [condition or event described]”.
  • CEST Chemical Exchange Saturation Transfer quantification is a CEST contrast agent in the target object to be imaged using saturation pulses, such as protein, glucose, creatine, etc., for pre-saturation, and the CEST contrast agent will exchange at a certain rate Chemical exchange occurs with the surrounding water molecules, thereby affecting the signal intensity of free water; by using imaging sequences to collect CEST signals reflecting the strength of the CEST effect, the chemical exchange characteristics of the CEST contrast agent can be quantified.
  • saturation pulses such as protein, glucose, creatine, etc.
  • saturation pulses are applied to a variety of CEST contrast agents present in a target object to quantify the chemical exchange characteristics of the CEST contrast agent.
  • the target object refers to an object containing a CEST contrast agent inside, such as biological tissue.
  • the skull of the organism is the target object.
  • an embodiment of the present application provides a chemical exchange feature quantification method.
  • the execution subject of the chemical exchange feature quantification method in this embodiment is a chemical exchange feature quantification device, and the chemical exchange feature quantification device may be a server. , It can also be a terminal device.
  • the quantitative methods of chemical exchange characteristics include:
  • the saturation pulse is used to pre-saturate the CEST contrast agent to collect the measured signal intensity of the CEST signal.
  • the CEST contrast agent can be an endogenous CEST contrast agent or an exogenous CEST contrast agent.
  • the preset conditions for applying the saturation pulse There is a corresponding relationship between the preset conditions for applying the saturation pulse and the strength of the collected CEST signal.
  • Saturation pulses are applied to each CEST contrast agent at its corresponding resonance frequency according to preset conditions. When multiple saturation pulses are applied, multiple measured signal strength values of the CEST signal for each CEST contrast agent can be obtained.
  • Figure 2 shows a schematic diagram of the CEST signal generated after the saturation pulse is applied; after the saturation pulse is applied, the CEST signal is collected, and the measured signal strength of the CEST signal can be obtained.
  • the preset condition is a condition under which the saturation pulse is applied, and may include the number of times the saturation pulse is applied and/or saturation pulse parameters.
  • saturation pulse parameters there are many important saturation pulse parameters in CEST quantification, including pulse intensity, duration, flip angle, duty cycle, etc.; one or more of them can be selected according to actual needs. For example, in this embodiment, two saturation pulse parameters of pulse intensity ⁇ 1 and duration T s are selected.
  • the preset condition is that at least one saturation pulse is applied in sequence, and each saturation pulse parameter is randomized within the set saturation pulse parameter range.
  • each saturation pulse is sequentially applied, and the measured signal intensity of the CEST signal detected after each application of the saturation pulse is collected.
  • the specific saturation pulse parameter selection in this embodiment uses a randomization method, that is, the saturation pulse parameter range is set first, and the value of the saturation pulse parameter is randomly selected in the saturation pulse parameter range before the saturation pulse is applied, and the value of the saturation pulse parameter is selected according to the selected saturation pulse.
  • the value of the parameter applies a saturation pulse.
  • the value of the saturation pulse parameter can also be set to a fixed value according to actual requirements.
  • the first (when the saturation pulse parameter is one type) or the first group (when the saturation pulse parameter is more than one type) is randomly generated first, and the recording is based on the saturation pulse parameter.
  • the measured value of the signal strength of the CEST signal detected after the first saturation pulse is applied; then the second or second set of saturation pulse parameters are randomly generated and the saturation pulse is applied according to the saturation pulse parameters, and the signal of the detected CEST signal is recorded Intensity measured value; and so on, before each saturation pulse is applied, the saturation pulse parameter is randomly selected within the selected saturation pulse parameter range, and then the saturation pulse is applied according to the saturation pulse parameter until all n saturation pulses are applied After that, the measured signal intensity values of n CEST signals at the resonance frequency of the CEST contrast agent and within the set saturation pulse parameter range can be obtained.
  • S102 Based on the quantitative range of theoretical chemical exchange characteristics corresponding to each CEST contrast agent, calculate multiple theoretical signal intensity values corresponding to the respective CEST signals of each CEST contrast agent; wherein the theoretical signal intensity value of each CEST signal is calculated during calculation
  • the corresponding saturation pulse parameter and resonance frequency are the same as the saturation pulse parameter and resonance frequency corresponding to the actual measured value of the signal strength.
  • the quantitative range of the theoretical chemical exchange characteristics of the CEST contrast agent refers to the possible quantitative range of the chemical exchange characteristics of the CEST contrast agent.
  • the range can be determined by prior knowledge, for example, through previous test data or by querying data.
  • the chemical exchange characteristic may be a chemical exchange rate and/or concentration, etc.; when the chemical exchange rate and concentration are selected for the chemical exchange characteristic, the quantitative range of the theoretical chemical exchange characteristic refers to the chemical exchange rate range and concentration range.
  • the resonance frequency is F1; in the preset condition, n saturation pulses are set to be applied, and the set saturation pulse parameter range is: pulse intensity ⁇ 0 ⁇ a , duration T s0 ⁇ T b .
  • the quantitative range of theoretical chemical exchange characteristics of the CEST contrast agent is: chemical exchange rate range K, concentration range c.
  • the first to nth saturation pulses are applied to the resonance frequency F1, and the randomly selected saturation pulse parameters (pulse intensity, duration) are: ( ⁇ 1 , T s1 ), ( ⁇ 2 , T s2 )...( ⁇ n , T sn ), where ⁇ 1 , ⁇ 2 ,... ⁇ n ⁇ ( ⁇ 0 ⁇ a ), T s1 , T s2 ,...T sn ⁇ (T s0 ⁇ T sb ). Then the measured signal intensity values of the first to nth CEST signals collected are CEST acq1 , CEST acq2 ... CEST acqn respectively .
  • the first chemical exchange rate and the first concentration (K 1 , c 1 ), when calculating the theoretical value of the signal intensity of the first to n CEST signals respectively
  • the resonance frequency F1 of the CEST contrast agent, and the saturation pulse parameters ( ⁇ 1 , T s1 ), ( ⁇ 2, T s2 )...( ⁇ n , T sn ) when the measured signal strength values of 1 to n CEST signals are collected are taken as Calculating conditions, calculating the theoretical values of the signal intensity of the 1st to nth CEST 1 ideal1 , CEST 1 ideal2 ...CEST 1 idealn .
  • the first theoretical value of signal strength CEST 1 ideal1 is calculated using parameters: [(K 1 ,c 1 ), F1, ( ⁇ 1 , T s1 )]; the second theoretical value of signal strength CEST 1 ideal2
  • the parameters used in the calculation are: [(K 1 ,c 1 ), F1, ( ⁇ 2 , T s2 )]...the theoretical value of the nth signal strength CEST 1 idealn
  • the parameters used in the calculation are: [(K 1 ,c 1 ), F1, ( ⁇ n , T sn )].
  • the parameters for calculating the theoretical value of the signal intensity of the first to n CEST signals are [(K 1 ,c 2 ), F1, ( ⁇ 1 , T s1 )], [(K 1 ,c 2 ), F1, ( ⁇ 2 , T s2 )]...[(K 1 ,c 2 ), F1, ( ⁇ n ,T sn )], correspondingly calculate 1 ⁇ n
  • Two theoretical signal strength values CEST 2 ideal1 , CEST 2 ideal2 ... CEST 2 idealn are [(K 1 ,c 2 ), F1, ( ⁇ 1 , T s1 )]].
  • the theoretical value of the signal intensity corresponding to the first to nth CEST signal can be calculated in sequence for each theoretical chemical exchange feature. Since each theoretical chemical exchange characteristic quantification can correspond to a theoretical value of signal intensity, a number of theoretical chemical exchange characteristic quantifications are selected from the quantitative range of theoretical chemical exchange characteristics, and the theoretical calculation can be obtained for a CEST contrast agent. Multiple theoretical values of signal strength corresponding to the measured value of signal strength.
  • the measured signal intensity of the CEST signal of each CEST contrast agent is matched with a plurality of corresponding theoretical signal intensity values; for example, the CEST signal is recorded after n saturation pulses are applied.
  • N measured signal strength values of CEST acq1 , CEST acq2 , CEST acq3 ..., CEST acqn among the multiple theoretical signal strength values corresponding to these n measured signal strength values, look for the measured values CEST acq1 , CEST acq2 , CEST acq3 ..., CEST acqn n theoretical values with the highest matching degree CEST ideal1 , CEST ideal2 , CEST ideal3 ...CEST idealn , the corresponding theoretical chemical exchange characteristics of these n theoretical values in the calculation process quantify the magnetization transfer effect of the target object Quantification of chemical exchange characteristics.
  • the actual measured value of the signal intensity of the CEST signal of each CEST contrast agent is matched with the corresponding multiple theoretical signal intensity values, and the theoretical chemical exchange characteristic quantification corresponding to the matching result is the quantitative result of the chemical exchange characteristic of each CEST contrast agent.
  • the embodiments of this application are directed to the actual measured value of the signal intensity of the CEST signal of each CEST contrast agent.
  • the theoretical value of the signal intensity is calculated, the actual measured value of the signal intensity is the same as the acquisition environment at the time of acquisition, that is, the saturation pulse parameter and the resonance frequency are the same. Therefore, based on the quantitative range of theoretical chemical exchange characteristics, multiple theoretical signal strength values corresponding to the actual measured signal strength can be calculated; because the theoretical signal strength value is calculated under the same acquisition environment as the actual measured signal strength value. Value, the one-to-many matching method is adopted to make the measured value of signal strength have a more accurate matching result.
  • the chemical exchange characteristic quantification process of this application does not need to select a reference signal, so it is not easily affected by other chemical exchange effects, so that the theoretical chemical exchange characteristic quantification corresponding to the matching result can more accurately represent the actual chemical exchange specific amount, so it is effective Improved the accuracy of chemical exchange of specific amounts.
  • S100-1 and S100-2 may also be included before S101:
  • S100-1 Determine the effective imaging range of each CEST contrast agent according to the chemical exchange characteristics of each CEST contrast agent; the parameters in the effective imaging range are saturation pulse parameters.
  • the chemical exchange characteristics of the CEST contrast agent may be, for example, chemical exchange rate and/or concentration.
  • the effective imaging range is an effective range applied to the saturation pulse parameters of the CEST contrast agent, within this range, the CEST contrast agent has a better imaging effect.
  • the effective imaging range of each CEST contrast agent can be determined by experiment, that is, for different saturation pulse parameters, perform the imaging experiment of the CEST contrast agent separately, and then select a saturation pulse parameter range with better imaging effect according to the imaging effect , As the effective imaging range of the CEST contrast agent. It can also be determined by prior knowledge, for example, by querying existing data for the CEST contrast agent's customary saturation pulse parameter range as the effective imaging range.
  • S100-2 Determine the saturation pulse parameter range of the saturation pulse according to the effective imaging range of all the CEST contrast agents; wherein the saturation pulse parameter in the saturation pulse parameter range belongs to the effective imaging range of each CEST contrast agent.
  • the saturation pulse parameters in the selected saturation pulse parameter range should belong to the effective imaging range of all CEST contrast agents at the same time, so that when the saturation pulse is applied, the randomly selected saturation pulse can be used in different CEST contrast agents.
  • the resonance frequency meets the imaging requirements of the CEST contrast agent.
  • the corresponding saturation pulse parameter ranges are also two, that is, the saturation pulse parameter corresponding to the pulse intensity Range and the saturation pulse parameter range corresponding to the duration.
  • saturation pulse parameters that is, select the two saturation pulse parameters of pulse intensity and duration as an example.
  • the CEST contrast agent with a slower needle chemical exchange rate (10-100Hz) its effective imaging range can be: saturation pulse The intensity is 0.5-4.0 ⁇ T, the duration is 30-100ms, and the representative CEST contrast agents are -NH, etc.; for the CEST contrast agents with a faster exchange rate (500-1500Hz), the effective imaging range can be: saturation pulse Intensity>2.0 ⁇ T, duration ⁇ 50ms, representative CEST contrast agents include -OH and so on.
  • the range of saturation pulse parameters can be selected: saturation pulse intensity 0.5-5 ⁇ T, duration 10-100ms.
  • the selection of saturation pulse parameters in CEST imaging is often based on experience, and the parameters remain constant during the data acquisition process. Only a single CEST contrast agent can be effectively quantified each time. On the one hand, it is difficult to obtain the best The CEST effect, on the other hand, is difficult to effectively quantify multiple CEST contrast agents with different chemical exchange characteristics at the same time.
  • the effective imaging range of each CEST contrast agent is first determined, and on this basis, the saturation pulse parameter range is determined.
  • the saturation pulse frequency is changed with the set step length, and the saturation pulse can be applied on the resonance frequency of each CEST contrast agent in turn, so that different CEST contrast agents can be quantified simultaneously; and according to CEST
  • the CEST data collected within the saturation pulse parameter range determined by the chemical exchange characteristics of the contrast agent can better obtain the CEST effect.
  • S101 can include S1011 ⁇ S1014.
  • a set frequency range is used and multiple frequencies are selected, and saturation pulses are applied to each frequency.
  • the measured signal intensity of each CEST contrast agent corresponding to the measured signal intensity of each CEST signal is extracted from the measured signal intensity of all CEST signals. The details are as follows:
  • S1011 Determine the frequency range of the saturation pulse to be applied according to the resonance frequency of a variety of CEST contrast agents; wherein the frequency in the frequency range of the saturation pulse covers the resonance frequency of each CEST contrast agent.
  • the frequency range corresponding to the resonance frequency of each CEST contrast agent is combined with the frequency range of the main magnetic field, and the result is taken as the frequency range of the saturation pulse.
  • the frequency range thus determined covers the resonance of each CEST contrast agent. frequency.
  • frequency offset is often used to describe frequency. There is a conversion relationship between frequency offset and frequency, specifically:
  • f represents the resonance frequency of the CEST contrast agent or the frequency of applying a saturation pulse
  • f 0 is the reference frequency.
  • the resonance frequency of water is used as the reference frequency.
  • the resonance frequency deviation of the endogenous CEST contrast agent relative to water molecules is usually -4 ⁇ 4ppm. If the frequency deviation of the main magnetic field is in the range of -1 ⁇ 1ppm, the frequency deviation range of the saturation pulse can be selected- 5 ⁇ 5ppm.
  • the simultaneous detection of three CEST contrast agents in biological tissues amino (-NH, 3.5ppm), amino (-NH 2 , 2ppm), and glutamate (3ppm) are taken as examples.
  • the frequency deviation range corresponding to the resonance frequency deviation of this CEST contrast agent is 2 ⁇ 3.5ppm.
  • the frequency deviation range of the saturation pulse can be selected from 1 ⁇ 4.5ppm. After the frequency offset range is determined, the frequency offset range is converted into frequency through Equation 1, and the frequency range is obtained.
  • S1012 Select multiple frequencies from the frequency range of the saturation pulse, and the multiple frequencies include the resonance frequency of each CEST contrast agent.
  • the step size should be selected so that the divided frequencies include the resonance frequency of each CEST contrast agent. Take frequency offset as an example:
  • the CEST contrast agent to be detected is amino (-NH, 3.5 ppm), amino (-NH 2 , 2 ppm), There are three kinds of glutamate (3ppm), and the resonance frequency deviation is 3.5ppm, 2ppm, 3ppm, and the frequency deviation step size can be selected as 0.5ppm; that is, the frequency deviation step size meets the comparison of multiple CESTs to be detected
  • the resonance frequency offset of the agent is divided, the multiple frequency offsets after division can meet the requirements of covering the resonance frequency of each CEST contrast agent.
  • the offset step size and frequency offset are converted into frequency according to Equation 1, that is, the step size and the divided frequency are obtained.
  • the measured value of the signal strength of the CEST signal corresponding to the frequency can be detected. It is explained by dividing the frequency range into multiple frequencies [f1, f2, f3,...], and applying n sets of saturation pulses to each frequency.
  • S1014 Extract the measured signal intensity of the CEST signal corresponding to the resonance frequency of each CEST contrast agent from the measured signal intensity value of the CEST signal corresponding to each frequency as the measured signal intensity value of the CEST signal of the CEST contrast agent.
  • the measured value of the signal strength of the CEST signal detected when the saturation pulse is applied with the same resonance frequency is extracted , which is the measured value of the signal intensity of the CEST signal of the CEST contrast agent.
  • n CEST acq measured values of the CEST signal extracted from the CEST contrast agent there are also n CEST acq measured values of the CEST signal extracted from the CEST contrast agent. These n measured values reflect the signal intensity of the CEST signal of the CEST contrast agent. With the change of n saturation pulse parameters.
  • this embodiment adopts the above-mentioned first to set the frequency range, and then select multiple frequencies within the frequency range. Collect the measured signal intensity values at each frequency separately, and extract the measured signal intensity value of the CEST signal of each CEST contrast agent from all the measured signal intensity values. This method can be near the resonance frequency of each CEST contrast agent.
  • the magnetization transfer (MT) effect of free water is relatively strong, which interferes with the CEST signal.
  • S1-102 is executed after S101.
  • S102 may specifically include S1021 to S1023:
  • S1021 Obtain a first generation condition corresponding to the CEST signal of each CEST contrast agent, where the first generation condition includes the resonance frequency of the CEST contrast agent and the corresponding saturation pulse parameters when the saturation pulse is applied.
  • the first generation condition is the condition corresponding to when the actual signal strength value of the CEST signal is collected in S101.
  • the preset conditions include the saturation pulse parameter range, and the saturation pulse parameter corresponding to the saturation pulse is randomized within the set saturation pulse parameter range when collecting the actual measured value of the signal strength; for example, in the above example, the first saturation pulse is applied after the acquisition
  • the first generation condition of the received CEST signal is the resonance frequency F 1 of the CEST contrast agent and the saturation pulse parameters: pulse intensity ⁇ 1 and duration T s .
  • the quantitative range of the theoretical chemical exchange characteristics of the CEST contrast agent amino group can be: the chemical exchange rate range is 50-500 Hz, and the concentration range is 100-1000 mM.
  • the Bloch equation of the three-chemical exchange pool is used when calculating the multiple theoretical signal intensity values corresponding to the CEST signal.
  • the three chemical exchange pool Bloch equation refers to the free water and magnetization transfer MT Bloch equation; for example, for the CEST signal collected after the first saturation pulse is applied, through this equation, the quantitative result of the chemical exchange characteristics of the magnetization transfer effect is used, the first The resonance frequency F1 in the generation conditions and the saturation pulse parameters: pulse intensity ⁇ 1 and duration T s can be calculated to obtain multiple theoretical signal intensity values when quantifying the different theoretical chemical exchange characteristics of the CEST contrast agent.
  • the Bloch equation of the three-chemical exchange pool takes into account the effects of free water and magnetization transfer. Therefore, the direct saturation effect and magnetization transfer effect of own water can be effectively excluded when the theoretical value of the signal intensity of the CEST signal is used, so that the calculation result of the theoretical value is more accurate.
  • a CEST signal dictionary set of each CEST contrast agent can be further established to save multiple measured signal strength values of each CEST signal to facilitate the subsequent matching process .
  • S1-102 may also include: S1-1021 to S1-1023:
  • the resonance frequency deviation of free water is 0ppm.
  • the three CEST contrast agents listed in this example amino (-NH, 3.5ppm), amino (-NH 2 , 2ppm), and glutamate (3ppm) resonance
  • the frequency deviation range is 2 ⁇ 3.5ppm. Therefore, the resonance frequency deviation of 10ppm is far enough from the resonance frequency of free water and CEST contrast agent. Therefore, it is possible to apply a saturation pulse to the resonance frequency corresponding to the resonance frequency deviation of 10ppm. Satisfy the quantitative demand for obtaining the chemical exchange characteristics of the magnetization transfer effect.
  • the resonance frequency at 10 ppm is already a relatively far resonance frequency, which meets the needs of most CEST contrast agents for quantification of the chemical exchange characteristics of the magnetization transfer effect in general. It should be noted that the enumeration here is only illustrative and not restrictive; other resonance frequencies such as 8 ppm, 9 ppm, 11 ppm, etc. can also be selected for the application of the saturation pulse.
  • “Far away” can be understood as selecting the largest resonance frequency value among the resonance frequencies of all CEST contrast agents, adding f to the value of the resonance frequency offset corresponding to this value, and the obtained resonance frequency offset corresponding to The resonance frequency can be understood as the resonance frequency far away from the free water and the CEST contrast agent; where f can be a natural number, for example, its value is >2ppm.
  • a saturation pulse is applied to the target object according to preset conditions.
  • the preset condition here is the same as the preset condition in S101, that is, at least one saturation pulse is applied in sequence, and each saturation pulse parameter is randomized within the set saturation pulse parameter range.
  • the saturation pulse parameter range can also be the same as in S101.
  • Saturation pulses are applied at the determined resonance frequency, the saturation pulse parameters of each saturation pulse are randomized within the set saturation pulse parameter range, and the measured signal strength MT acq of the magnetization transfer signal generated after the saturation pulse is collected.
  • the measured signal strength values of multiple magnetization transfer signals can be correspondingly collected.
  • the number of saturation pulses applied to the acquisition of the magnetization transfer signal is the same as that of the acquisition of the CEST signal, that is, the actual measured signal strength of n magnetization transfer signals are finally collected.
  • the theoretical calculation method is used to determine multiple theoretical values of the signal intensity of the magnetization transfer signal when different theoretical chemical exchange characteristics are quantified.
  • the chemical exchange characteristics may be chemical exchange rate and/or concentration, etc.
  • the quantitative range of the theoretical chemical exchange characteristics refers to the chemical exchange rate range and concentration range.
  • the quantitative range of the theoretical chemical exchange characteristics of the magnetization transfer signal can be determined by prior knowledge, for example, by past test data or by querying data.
  • the resonance frequency far away from free water and all CEST contrast agents is determined to be F2.
  • n saturation pulses are set to be applied, and the set saturation pulse parameter range is : Pulse intensity ⁇ 0 ⁇ a , duration T s0 ⁇ T sb .
  • the quantitative range of the theoretical chemical exchange characteristics of the magnetization transfer signal is: the chemical exchange rate range K', and the concentration range c'.
  • K' a in the concentration range of c ' equal intervals select b concentrations c '1, c' 2 ... c 'b, the chemical exchange rate, the concentration co may constitute a ⁇ b combinations (K' 1, c '1 ), (K' 1, c '2 ), (K' 1 ,c' 3 )...(K' a ,c' b ), that is, a ⁇ b quantitative theoretical chemical exchange characteristics.
  • the first to nth saturation pulses are applied to the resonance frequency F2, and the randomly selected saturation pulse parameters (pulse intensity, duration) are: ( ⁇ ' 1 , T's1 ), ( ⁇ ' 2 , T's2 ) ... ( ⁇ 'n, T' sn), wherein, ⁇ '1, ⁇ ' 2 , ... ⁇ 'n ⁇ ( ⁇ 0 ⁇ ⁇ a), T' s1, T 's2, ... T' sn ⁇ (T s0 ⁇ T sb ). Then the measured signal intensity values of the first to nth magnetization transfer signals collected are MT acq1 , MT acq2 ... MT acqn respectively .
  • the parameters used in the calculation of the first theoretical value of signal strength MT 1 ideal1 are: [(K' 1 ,c' 1 ), F2, ( ⁇ ' 1 ,T' s1 )]; the second theoretical value of signal strength
  • the parameters used in the calculation of the value MT 1 ideal2 are: [(K' 1 ,c' 1 ), F2, ( ⁇ ' 2 ,T' s2 )]...the nth theoretical value of signal strength MT 1 idealn used in the calculation
  • the parameters of is: [(K' 1 ,c' 1 ), F2, ( ⁇ ' n , T'sn )].
  • the parameters for calculating the theoretical value of the signal intensity of the first to n CEST signals are [(K' 1 ,c' 2 ), F2, ( ⁇ '1, T' s1) ], [(K '1, c' 2), F2, ( ⁇ '2, T' s2)] ... [(K '1, c' 2), F2, ( ⁇ ' n , T'sn )], correspondingly calculated 1 ⁇ n theoretical signal strength values MT 2 ideal1 , MT 2 ideal2 ...MT 2 idealn .
  • the theoretical value of the signal intensity corresponding to the first to nth magnetization transfer signals for each theoretical chemical exchange feature can be calculated in sequence. Since each theoretical chemical exchange characteristic quantification can correspond to a theoretical value of signal intensity, a number of theoretical chemical exchange characteristic quantifications are selected from the quantitative range of theoretical chemical exchange characteristics, and the theoretical calculation can be obtained for a magnetization transfer signal. Multiple theoretical values of signal strength corresponding to the measured value of signal strength.
  • n signals of the magnetization transfer signal are recorded after n saturation pulses are applied.
  • the measured intensity values are MT acq1 , MT acq2 , MT acq3 ..., MT acqn .
  • the theoretical chemical exchange characteristic quantification corresponding to these n theoretical values in the calculation process is the quantification of the chemical exchange characteristic of the magnetization transfer effect of the target object.
  • the theoretical chemical exchange quantitative characteristic (K 'i, c' j ) is the result of quantitative chemical exchange wherein magnetization transfer effect of the target object .
  • the method of calculating the theoretical value of the signal strength of the magnetization transfer signal is adopted, so that for each measured value of the signal strength of the magnetization transfer signal, there are multiple corresponding theoretical signal strength values; because these theoretical values are based on The theoretical chemical exchange characteristic quantitative range is calculated under the same resonance frequency and saturation pulse parameters as the actual measured value. Therefore, the actual measured value can accurately find the theoretical value with the highest matching degree, thereby making the magnetization transfer effect quantitative result More precise. You can select more quantitative values in the quantitative range of theoretical chemical exchange characteristics to calculate more theoretical values of signal intensity to further improve the accuracy of the quantitative results of the magnetization transfer effect.
  • S1-1022 may also include S1-10221 to S1-10223:
  • S1-10221 Obtain a second generation condition corresponding to the magnetization transfer signal.
  • the second generation condition includes the information about the distance from free water and the resonance frequencies of all CEST contrast agents, and the corresponding saturation pulse parameters when the saturation pulse is applied.
  • the second generation condition is the corresponding condition when collecting the actual measured value of the signal intensity of the magnetization transfer signal in S1-10221.
  • the preset conditions include the saturation pulse parameter range, and the saturation pulse parameter corresponding to the saturation pulse is randomized within the set saturation pulse parameter range when collecting the actual measured value of the signal strength; for example, in the above example, the first saturation pulse is applied after the acquisition the magnetization transfer signal, generating a second condition away from the resonance frequency of free water and all the CEST contrast agent is F2 of, saturation and pulse parameters: pulse intensity ⁇ '1, the duration T' s.
  • the quantitative range of the theoretical chemical exchange characteristic of the magnetization transfer signal is obtained from previous experimental data.
  • the range of the chemical exchange rate K is set to 5-100 Hz, and the concentration c The range is 2-30M.
  • the dual chemical exchange cell Bloch equation is used when calculating multiple theoretical signal strength values corresponding to the magnetization transfer signal.
  • the double chemical exchange cell Bloch equation refers to the free water and magnetization transfer MT Bloch equation; for example, for the magnetization transfer signal collected after the first saturation pulse is applied, through this equation, the resonance frequency in the second generation condition is F2, and saturated pulse parameters: pulse intensity ⁇ '1, the duration T' s, to obtain a plurality of calculated signal strength of theory of the chemical characteristics of different switching signals magnetization transfer quantitative theory.
  • a magnetization transfer signal dictionary set can be further established to save multiple measured signal strength values of each magnetization transfer signal to facilitate the subsequent matching process.
  • Figure 7 shows multiple theoretical values of signal intensity of the CEST signal of a CEST contrast agent.
  • the saturation pulse number is used as the abscissa axis in Fig. 7, and the theoretical values of the CEST signal intensity corresponding to different saturation pulses are connected in sequence to obtain the quantitative analysis of different theoretical chemical exchange characteristics.
  • the corresponding theoretical value of signal strength varies with the number of the saturation pulse.
  • there are 8 change curves in total that is, there are 8 change curves of the theoretical value of the signal intensity corresponding to a specific amount of theoretical chemical exchange.
  • the curve in Fig. 8 is matched in Fig. 7, and the theoretical chemical exchange characteristic quantification corresponding to each theoretical value of the signal intensity in the change curve with the highest degree of matching is the quantification of the chemical exchange characteristic of the CEST contrast agent. It can be seen from the matching result in FIG. 9 that the method of the embodiment of the present application has a high degree of matching.
  • the magnetization transfer effect is quantified.
  • the influence of the magnetization transfer effect on the calculation environment is eliminated, so that the calculated theoretical value of the signal strength is more accurate.
  • the magnetization transfer effect can be accurately quantified in this application, so the magnetization transfer effect can be effectively removed and further improved The accuracy of the quantitative results is improved.
  • Mapping the quantitative results of the chemical exchange characteristics of each CEST contrast agent in a pseudo-color map, etc., can obtain the simultaneous quantitative imaging results of each CEST contrast agent.
  • Fig. 10 shows a chemical exchange characteristic quantification device provided by the present application.
  • the modules included in the chemical exchange characteristic quantification device in this embodiment are used to execute the respective corresponding to Fig. 1, Fig. 3 to Fig. 6 in the above method embodiment.
  • the chemical exchange characteristic quantitative device includes:
  • the first acquisition module 1 is used to acquire the measured signal intensity values of the respective CEST signals of the various chemical exchange saturation transfer CEST contrast agents to be detected in the target object; wherein the CEST signal is preset at the resonance frequency of the CEST contrast agent Condition is generated when saturation pulse is applied;
  • the first calculation module 2 is used to calculate multiple theoretical values of signal intensity corresponding to the respective CEST signal of each CEST contrast agent based on the quantitative range of theoretical chemical exchange characteristics corresponding to each CEST contrast agent; wherein, the signal of each CEST signal
  • the saturation pulse parameter and resonance frequency corresponding to the theoretical value of intensity during calculation are the same as the saturation pulse parameter and resonance frequency corresponding to the measured value of the signal intensity;
  • the first matching module 3 is used to match the measured signal intensity value of the CEST signal corresponding to each CEST contrast agent with its corresponding multiple theoretical signal intensity values, and exchange the theoretical chemical values corresponding to the theoretical signal intensity values with the highest matching degree Feature quantification is used as the quantitative result of chemical exchange feature of CEST contrast agent.
  • the chemical exchange characteristic quantitative device further includes:
  • the first setting module is used to determine the effective imaging range of each CEST contrast agent according to the chemical exchange characteristics of each CEST contrast agent; the parameter in the effective imaging range is the saturation pulse parameter;
  • the second setting module is used to determine the saturation pulse parameter range of the saturation pulse according to the effective imaging range of all CEST contrast agents; wherein, the saturation pulse parameter in the saturation pulse parameter range belongs to the effective imaging range of each CEST contrast agent.
  • the preset condition is that at least one saturation pulse is applied in sequence, and each saturation pulse parameter is randomized within the set saturation pulse parameter range.
  • the first collection module 1 includes:
  • the frequency range setting unit 11 is used to determine the frequency range of the saturation pulse to be applied according to the resonance frequency of a variety of CEST contrast agents; wherein, the frequency in the frequency range of the saturation pulse covers the resonance frequency of each CEST contrast agent;
  • the frequency selection unit 12 is configured to select multiple frequencies from the frequency range of the saturation pulse, and the multiple frequencies include the resonance frequency of each CEST contrast agent;
  • the first collection subunit 13 is used to collect the actual measured value of the signal strength of the CEST signal corresponding to each frequency when the saturation pulse is applied at each of the multiple frequencies according to the preset condition;
  • the extraction unit 14 is used to extract the measured signal intensity of the CEST signal corresponding to the resonance frequency of each CEST contrast agent from the measured signal intensity of the CEST signal corresponding to each frequency as the measured signal intensity of the CEST signal of the CEST contrast agent value.
  • chemical exchange characteristic quantitative device further includes:
  • the quantification module 4 is used to quantify the magnetization transfer effect of the target object, and obtain the quantitative result of the chemical exchange characteristic of the magnetization transfer effect;
  • the first calculation module 2 includes:
  • the first acquisition unit 21 is configured to acquire the first generation condition corresponding to the CEST signal of each CEST contrast agent, the first generation condition includes the resonance frequency of the CEST contrast agent and the corresponding saturation pulse parameter when the saturation pulse is applied;
  • the first determining unit 22 is used to determine the quantitative range of theoretical chemical exchange characteristics of each CEST contrast agent
  • the first calculation subunit 23 is used to quantify different theoretical chemical exchange characteristics in the quantitative range of theoretical chemical exchange characteristics, and calculate the amount corresponding to the CEST signal generated under the first generation condition by using the quantitative result of the chemical exchange characteristic of the magnetization transfer effect. A theoretical value of signal strength.
  • the quantization module 4 includes:
  • the second acquisition module 41 is configured to acquire the actual measured value of the signal intensity of the magnetization transfer signal collected when the saturation pulse is applied according to the preset conditions at the resonance frequency of the free water and all the CEST contrast agents;
  • the second calculation module 42 is used to calculate a plurality of theoretical signal strength values corresponding to the magnetization transfer signal based on the theoretical chemical exchange characteristic quantitative range of the magnetization transfer signal; wherein the corresponding saturation value is calculated when the theoretical value of the signal strength of the magnetization transfer signal is calculated
  • the pulse parameters and resonance frequency are the same as the saturation pulse parameters and resonance frequency corresponding to the actual measured value of the signal strength of the magnetization transfer signal;
  • the second matching module 43 is used to match the measured signal intensity of the magnetization transfer signal with its corresponding multiple theoretical signal intensity values, and quantify the theoretical chemical exchange characteristic corresponding to the theoretical value of the signal intensity with the highest matching degree as the magnetization of the target object Quantitative results of the chemical exchange characteristics of the transfer effect.
  • the second calculation module includes:
  • the second acquisition unit is used to acquire the second generation condition corresponding to the magnetization transfer signal, the second generation condition includes the information far away from free water and the resonance frequency of all CEST contrast agents, and the corresponding saturation pulse parameters when the saturation pulse is applied;
  • the second determining unit is used to determine the quantitative range of the theoretical chemical exchange characteristic of the magnetization transfer signal
  • the second calculation subunit is used to calculate multiple theoretical values of signal intensity corresponding to the magnetization transfer signal generated under the second generation condition based on different theoretical chemical exchange characteristic quantification in the theoretical chemical exchange characteristic quantification range.
  • an embodiment of the present application further provides a chemical exchange feature quantification device 5.
  • a chemical exchange feature quantification device 5 As shown in FIG. 14, it includes a memory 52, a processor 51, and a computer readable stored in the memory 52 and running on the processor. Instruction 53, the processor 51 executes the computer-readable instruction 53 to implement the aforementioned chemical exchange feature quantification method, for example, S101 to S103 shown in FIG. 1.
  • the computer-readable instructions 53 may also be divided into one or more modules/units, and the one or more modules/units are stored in the memory 52 and executed by the processor 51 to complete the application.
  • One or more modules/units may be a series of computer-readable instruction instruction segments capable of completing specific functions, and the instruction segments are used to describe the execution process of the computer-readable instructions 53 in the chemical exchange characteristic quantification device 5, for example, a computer may
  • the read instruction 53 can be divided into a first collection module, a first calculation module, and a first matching module. For the functions of each module, refer to the description in the foregoing system, and will not be repeated.
  • the implementation of this application provides a computer-readable storage medium, the computer-readable storage medium stores computer-readable instructions, and when the computer-readable instructions are executed by a processor, the above-mentioned chemical exchange characteristic quantitative method is realized, for example, as shown in FIG. 1 S101 to S103.
  • the integrated module/unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium.
  • this application implements all or part of the processes in the above-mentioned embodiments and methods, and can also be completed by instructing relevant hardware through computer-readable instructions.
  • the computer-readable instructions can be stored in a computer-readable storage medium. When the computer-readable instructions are executed by the processor, they can implement the steps of the foregoing method embodiments.
  • the computer-readable instruction includes computer-readable instruction code, and the computer-readable instruction code may be in the form of source code, object code, executable file, or some intermediate forms.
  • Computer-readable media may include: any entity or device capable of carrying computer-readable instruction codes, recording media, U disks, mobile hard disks, magnetic disks, optical disks, computer storage, read-only memory (ROM, Read-Only Memory), random access Access memory (RAM, Random Access Memory), electric carrier signal, telecommunications signal, software distribution medium, etc. It should be noted that the content contained in computer-readable media can be appropriately added or deleted in accordance with the requirements of the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to the legislation and patent practice, computer-readable media does not include Electric carrier signal and telecommunications signal.
  • the embodiment of the present application also provides a computer-readable instruction product.
  • the chemical exchange feature quantification device executes the above-mentioned chemical exchange feature quantification method, for example, as shown in FIG. 1 S101 to S103 shown.

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Abstract

一种化学交换特征定量方法及设备，该方法对于多种CEST对比剂的CEST信号的信号强度实测值，基于各CEST对比剂的理论化学交换特征定量范围，分别计算在与信号强度实测值相同的饱和脉冲参数、共振频率下对应的信号强度理论值，将匹配度最高的理论值对应的理论化学交换特征定量作为CEST对比剂的化学交换特征定量结果。该化学交换特征定量过程无需选择参照信号，不易受到其他化学交换效应的影响，由此使得匹配结果对应的理论化学交换特征定量能更准确地代表实际的化学交换特征定量，有效地提高了化学交换特征定量的准确率。

Description

化学交换特征定量方法及设备 技术领域
本申请涉及生物医学工程领域，具体涉及一种化学交换特定量方法及设备。
背景技术
化学交换饱和转移(Chemical Exchange Saturation Transfer,CEST)成像是一种磁共振分子影像手段，基于内源性或外源性CEST对比剂中可交换质子与水分子的化学交换作用，可无创获取生物体组织能量代谢、酸碱环境、对比剂含量等微观层面信息，在疾病的识别、诊断、评估中具有重要的研究价值和应用潜力。CEST对比剂，包括机体自身代谢物质及外源性对比剂；其中，代表性的内源性CEST对比剂包括蛋白质、肌酸、葡萄糖等，可反映细胞构成、酸碱环境、能量代谢及摄取等重要信息；外源性CEST对比剂主要来源于人工合成的化合物。
在CEST对比剂成像过程中，由于自由水的直接饱和效应和磁化转移(MT)效应相对较强，干扰CEST对比剂的信号，导致CEST对比剂的化学交换特征(如化学交换速率、浓度等)同步定量结果准确率相对较低。针对该问题相关技术中在CEST对比剂成像时常用的方法包括非对称性分析法、三点法、高阶多项式拟合法等。然而，这些方法在计算CEST效应时需要寻找参照信号，而参照信号易包含其他CEST效应，故在计算反映CEST效应强弱的CEST信号时易受到其他CEST效应的影响，从而导致多种CEST对比剂化学交换特征定量准确率较低。
发明内容
本申请的实施例提供一种化学交换特征定量方法及设备，可以解决现有技术中CEST对比剂的化学交换特征定量准确率低的问题。
为了解决上述技术问题，本申请实施例采用的技术方案是：
第一方面本申请实施例提供了一种化学交换特征定量方法，包括：采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，CEST信号在对CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号 强度实测值对应的饱和脉冲参数、共振频率相同；将每种CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为CEST对比剂的化学交换特征定量结果。
可选地，采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值之前，还包括：
根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；有效成像范围中的参数为饱和脉冲参数；根据所有CEST对比剂的有效成像范围，确定饱和脉冲的饱和脉冲参数范围；其中，饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
示例性的，预设条件为：
依次施加至少一个饱和脉冲，每个饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
在第一方面的一种可能实现的方式中，采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值，包括：根据多种CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；从饱和脉冲的频率范围中选择多个频率，多个频率包含各CEST对比剂的共振频率；在多个频率中的每个频率上按预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；从每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为CEST对比剂的CEST信号的信号强度实测值。
进一步地，基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值之前，还包括：
量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果；基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值，包括：获取每种CEST对比剂的CEST信号对应的第一生成条件，第一生成条件包括CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；确定每种CEST对比剂的理论化学交 换特征定量范围；基于理论化学交换特征定量范围中不同的理论化学交换特征定量，利用磁化转移效应的化学交换特征定量结果计算在第一生成条件下生成的CEST信号所对应的多个信号强度理论值。
在第一方面的一种可选的实现方式中，量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果，包括：
获取在远离自由水和所有CEST对比剂的共振频率上，按照预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；基于磁化转移信号的理论化学交换特征定量范围，计算磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同；将磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为目标物体的磁化转移效应的化学交换特征定量结果。
进一步地，基于磁化转移信号的理论化学交换特征定量范围，计算磁化转移信号对应的多个信号强度理论值，包括：
获取磁化转移信号对应的第二生成条件，第二生成条件包括远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；确定磁化转移信号的理论化学交换特征定量范围；基于理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
可选地，饱和脉冲参数包括：脉冲强度、持续时间、翻转角、占空比中的任一种或一种以上的组合。
第二方面，本申请实施例提供了一种化学交换特征定量装置，包括：
第一采集模块，用于采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，CEST信号在对CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；第一计算模块，用于基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲 参数、共振频率相同；第一匹配模块，用于将每种CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为CEST对比剂的化学交换特征定量结果。
可选地，化学交换特征定量装置还包括：
第一设定模块，用于根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；有效成像范围中的参数为饱和脉冲参数；第二设定模块，用于根据所有CEST对比剂的有效成像范围，确定饱和脉冲的饱和脉冲参数范围；其中，饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
进一步地，预设条件为：依次施加至少一个饱和脉冲，每个饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
可选地，第一采集模块包括：
频率范围设定单元，用于根据多种CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；频率选择单元，用于从饱和脉冲的频率范围中选择多个频率，多个频率包含各CEST对比剂的共振频率；第一采集子单元，用于在多个频率中的每个频率上按预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；提取单元，用于从每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为CEST对比剂的CEST信号的信号强度实测值。
进一步地，化学交换特征定量装置还包括：
量化模块，用于量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果；
第一计算模块包括：
第一获取单元，用于获取每种CEST对比剂的CEST信号对应的第一生成条件，第一生成条件包括CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；第一确定单元，用于确定每种CEST对比剂的理论化学交换特征定量范围；第一计算子单元，用于基于理论化学交换特征定量范围中不同的理论化学交换特征定量，利用磁化转移效应的化学交换特征定量结果计算在第一生成条 件下生成的CEST信号所对应的多个信号强度理论值。
可选地，量化模块包括：
第二采集模块，用于获取在远离自由水和所有CEST对比剂的共振频率上，按照预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；第二计算模块，用于基于磁化转移信号的理论化学交换特征定量范围，计算磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同；第二匹配模块，用于将磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为目标物体的磁化转移效应的化学交换特征定量结果。
进一步地，第二计算模块包括：
第二获取单元，用于获取磁化转移信号对应的第二生成条件，第二生成条件包括远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；第二确定单元，用于确定磁化转移信号的理论化学交换特征定量范围；第二计算子单元，用于基于理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
第三方面，本申请提供了一种化学交换特征定量设备，包括存储器、处理器以及存储在存储器中并可在处理器上运行的计算机可读指令，处理器执行计算机可读指令时实现第一方面所述的化学交换特征定量方法。
第四方面，本申请提供了一种计算机可读存储介质，计算机可读存储介质存储有计算机可读指令，计算机可读指令被处理器执行时实现第一方面所述的化学交换特征定量方法。
第五方面，本申请提供了一种计算机可读指令产品，当计算机可读指令产品在化学交换特征定量设备上运行时，使得化学交换特征定量设备执行第一方面所述的化学交换特征定量方法的步骤。
本申请实施例与现有技术相比存在的有益效果是：
本申请的实施例中针对于每一个CEST对比剂的CEST信号的信号强度实测 值，在信号强度理论值进行计算时与信号强度实测值在采集时的采集环境，即饱和脉冲参数、共振频率相同，因此基于理论化学交换特征定量范围，可以计算出多个与信号强度实测值对应的信号强度理论值；信号强度理论值是在与信号强度实测值采集时相同的采集环境下计算得到的多个值，采用一对多的匹配方式使得信号强度实测值能有更准确的匹配结果。本申请的化学交换特征定量过程无需选择参照信号，不易受到其他化学交换效应的影响，由此使得匹配结果对应的理论化学交换特征定量能更准确地代表实际的化学交换特定量，故本申请有效地提高了化学交换特定量的准确率。
可以理解的是，上述第二方面至第五方面的有益效果可以参见上述第一方面中的相关描述，在此不再赘述。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1是本申请一个实施例提供的化学交换特征定量方法流程示意图；
图2是施加饱和脉冲后产生CEST信号的示意图；
图3是本申请的一个实施例提供的S101的流程示意图；
图4是本申请的一个实施例提供的S102的流程示意图；
图5是本申请的一个实施例提供的量化目标物体的磁化转移效应的流程示意图；
图6是本申请的一个实施例提供的计算磁化转移信号对应的多个信号强度理论值的流程示意图；
图7是本申请的一个实施例中计算得到的CEST信号的多个信号强度实测值随饱和脉冲序号的变化曲线；
图8是本申请的一个实施例采集的CEST信号的信号强度实测值随饱和脉冲序号的变化曲线；
图9是图8中的变化曲线在图7中多个变化曲线的匹配结果；
图10是本申请实施例提供的一种化学交换特征定量装置的结构框图；
图11是本申请的一个实施例中第一采集模块的结构框图；
图12是本申请的一个实施例中第一计算模块的结构框图；
图13是本申请的一个实施例中量化模块的结构框图；
图14是本申请的一个实施例提供的化学交换特征定量设备的示意图。
具体实施方式
以下描述中，为了说明而不是为了限定，提出了诸如特定系统结构、技术之类的具体细节，以便透彻理解本申请实施例。然而，本领域的技术人员应当清楚，在没有这些具体细节的其它实施例中也可以实现本申请。在其它情况中，省略对众所周知的系统、装置、电路以及方法的详细说明，以免不必要的细节妨碍本申请的描述。
应当理解，当在本申请说明书和所附权利要求书中使用时，术语“包括”指示所描述特征、整体、步骤、操作、元素和/或组件的存在，但并不排除一个或多个其它特征、整体、步骤、操作、元素、组件和/或其集合的存在或添加。
还应当理解，在本申请说明书和所附权利要求书中使用的术语“和/或”是指相关联列出的项中的一个或多个的任何组合以及所有可能组合，并且包括这些组合。
如在本申请说明书和所附权利要求书中所使用的那样，术语“如果”可以依据上下文被解释为“当...时”或“一旦”或“响应于确定”或“响应于检测到”。类似地，短语“如果确定”或“如果检测到[所描述条件或事件]”可以依据上下文被解释为意指“一旦确定”或“响应于确定”或“一旦检测到[所描述条件或事件]”或“响应于检测到[所描述条件或事件]”。
在本申请说明书中描述的参考“一个实施例”或“一些实施例”等意味着在本申请的一个或多个实施例中包括结合该实施例描述的特定特征、结构或特点。由此，在本说明书中的不同之处出现的语句“在一个实施例中”、“在一些实施例中”、“在其他一些实施例中”、“在另外一些实施例中”等不是必然都参考相同的实施例，而是意味着“一个或多个但不是所有的实施例”，除非是以其他方式另外特别强调。术语“包括”、“包含”、“具有”及它们的变形都意味着“包括但不限于”，除非是以其他方式另外特别强调。
为了说明本申请技术方案，下面通过具体实施例来进行说明。
应理解，下述实施例中各步骤的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
化学交换饱和转移(Chemical Exchange Saturation Transfer,CEST)定量是一种利用饱和脉冲对待成像的目标物体中CEST对比剂，例如蛋白质、葡萄糖、肌酸等进行预饱和，CEST对比剂会以一定的交换速率和周围的水分子发生化学交换，从而影响自由水的信号强度；通过采用成像序列采集反映CEST效应强弱的CEST信号，即可进行CEST对比剂化学交换特征定量。
本申请的实施例中对目标物体中存在的多种CEST对比剂施加饱和脉冲进行CEST对比剂化学交换特征定量，目标物体是指内部含有CEST对比剂的物体，例如生物体组织。示例性的，需要对生物体的颅部内的CEST对比剂进行化学交换特征定量时，生物体的颅部即为目标物体。
如图1所示，本申请的一个实施例提供了一种化学交换特征定量方法，本实施例中的化学交换特征定量方法的执行主体为化学交换特征定量设备，化学交换特征定量设备可以是服务器，也可以是终端设备，化学交换特征定量方法包括：
S101，采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，CEST信号在对CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生。
本申请的实施例中，利用饱和脉冲对CEST对比剂进行预饱和以采集CEST信号的信号强度实测值。在每个CEST对比剂对应的共振频率上按预设条件施加饱和脉冲，即可采集到该CEST对比剂的CEST信号的信号强度实测值。其中，CEST对比剂可以是内源性CEST对比剂或外源性CEST对比剂。施加饱和脉冲的预设条件与采集到的CEST信号的强弱存在对应关系，当依次施加多个不同预设条件的饱和脉冲时，可对应采集到多个CEST信号的信号强度实测值。分别针对每一个CEST对比剂在其对应的共振频率上按照预设条件施加饱和脉冲，当施加多个饱和脉冲时，可得到针对于每一个CEST对比剂的CEST信号的多个信号强度实测值。
请一并参阅图2，图2展示出了施加饱和脉冲后产生CEST信号的示意图；在施加饱和脉冲后，采集CEST信号，即可得到CEST信号的信号强度实测值。
在一种可选的实现方式中，施加饱和脉冲进行CEST对比剂的预饱和之前，首先设定好饱和脉冲施加的预设条件。预设条件是饱和脉冲施加所遵循的条件，可以包括饱和脉冲施加的次数和/或饱和脉冲参数等。其中，在CEST定量中有多个重要的饱和脉冲参数，包括脉冲强度、持续时间、翻转角、占空比等；可以根据实际需要选择其中一种或一种以上的组合。例如，本实施例中选择脉冲强度ω 1、持续时间T s这两个饱和脉冲参数。
可选地，在一个具体的示例中，预设条件为依次施加至少一个饱和脉冲，每个饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
即，在每一个CEST对比剂的共振频率上，依次施加至少一个饱和脉冲，并采集每次施加饱和脉冲之后探测到的CEST信号的信号强度实测值。本实施例中具体的饱和脉冲参数选取利用随机化的方法，即先设定好饱和脉冲参数范围，施加饱和脉冲之前先在饱和脉冲参数范围中随机选取饱和脉冲参数的值，按照选取的饱和脉冲参数的值施加饱和脉冲。在其他的示例中，饱和脉冲参数的值也可以根据实际需求设定为固定值。
例如在一个CEST对比剂的共振频率选择施加n个饱和脉冲，则CEST信号的信号强度实测值的采集过程为：
照预设条件中的饱和脉冲参数范围首先随机产生第一个(当饱和脉冲参数为一种时)或第一组(当饱和脉冲参数为一种以上时)饱和脉冲参数，记录按照该饱和脉冲参数施加第一个饱和脉冲后探测到的CEST信号的信号强度实测值；然后随机产生第二个或第二组饱和脉冲参数并按照该饱和脉冲参数施加饱和脉冲，记录探测到的CEST信号的信号强度实测值；以此类推，在每个饱和脉冲施加之前，先在选定的饱和脉冲参数范围内随机选择饱和脉冲参数，然后再按照该饱和脉冲参数施加饱和脉冲，直至n个饱和脉冲全部施加完，即可得到在该CEST对比剂的共振频率上及设定的饱和脉冲参数范围内的n个CEST信号的信号强度实测值。
S102，基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲参数、共振频率相同。
CEST对比剂的理论化学交换特征定量范围，是指该CEST对比剂可能的化学交换特征定量范围，该范围可通过先验知识确定，例如通过以往的试验数据，或通过查询资料的方式来确定。其中，化学交换特征可以是化学交换速率和/或浓度等；在化学交换特征选择化学交换速率和浓度时，理论化学交换特征定量范围指化学交换速率范围和浓度范围。
基于CEST对比剂对应的理论化学交换特征定量范围，在与CEST信号的信号强度实测值采集时相同的饱和脉冲参数、共振频率条件下，可计算多个与CEST信号对应的信号强度理论值。例如，可利用理论化学交换特征定量范围中不同的理论化学交换特征定量进行计算，针对于一个理论化学交换特征定量，通过理论计算的方式可得到一个信号强度理论值；那么将范围中的多个理论化学交换特征定量分别计算信号强度理论值，即可得到对应于CEST信号的多个信号强度理论值。由于针对一个CEST信号可探测到一个信号强度实测值，因此信号强度理论值与信号强度实测值存在多对一的对应关系。
当针对于每个CEST对比剂施加多个饱和脉冲而采集多个CEST信号时，在计算每个CEST信号的对应的多个信号强度理论值过程中，首先从CEST对比剂的理论化学交换特征定量范围中选取多个理论化学交换特征定量，按照取出的化学交换特征定量，依次计算在每个化学交换特征定量下，每个CEST信号的信号强度理论值。
例如，对于一个CEST对比剂，其共振频率为F1；预设条件中，设定施加n个饱和脉冲，设定的饱和脉冲参数范围是：脉冲强度ω 0～ω a、持续时间T s0～T b。该CEST对比剂的理论化学交换特征定量范围为：化学交换速率范围K，浓度范围c。在理论化学交换特征定量范围中选择多个理论化学交换特征定量，例如在化学交换速率范围K中等间隔选取p个化学交换速率K 1、K 2…K p，在浓度范围c中等间隔选取q个浓度c 1、c 2…c q，则化学交换速率、浓度共可以构成p×q个组合(K 1,c 1)、(K 1,c 2)、(K 1,c 3)…(K p,c q)，也即p×q个理论化学交换特征定量。
在采集该CEST对比剂的CEST信号的信号强度实测值时：
在共振频率F1上施加第1至第n个饱和脉冲，随机选择的饱和脉冲参数(脉冲强度,持续时间)分别为：(ω 1，T s1)、(ω 2，T s2)…(ω n，T sn)，其中，ω 1,ω 2,…ω n∈(ω 0～ω a)，T s1,T s2,…T sn∈(T s0～T sb)。则采集到的第1个至第n个CEST信号的信号强 度实测值分别为CEST acq1、CEST acq2…CEST acqn。
在计算该CEST对比剂的CEST信号的多个信号强度理论值时：
对于第1个理论化学交换特征定量，本例中为第1个化学交换速率和第1个浓度(K 1,c 1)，计算第1～n个CEST信号的信号强度理论值时，分别将CEST对比剂的共振频率F1，以及采集1～n个CEST信号的信号强度实测值时的饱和脉冲参数(ω 1，T s1)、(ω 2，T s2)…(ω n，T sn)作为计算条件，计算得到第1～n个信号强度理论值CEST 1 ideal1、CEST 1 ideal2…CEST 1 idealn。即，第1个信号强度理论值CEST 1 ideal1在计算时所用的参量为：[(K 1,c 1)、F1、(ω 1，T s1)]；第2个信号强度理论值CEST 1 ideal2在计算时所用的参量为：[(K 1,c 1)、F1、(ω 2，T s2)]…第n个信号强度理论值CEST 1 idealn在计算时所用的参量为：[(K 1,c 1)、F1、(ω n，T sn)]。
通过以上方法，计算得到了针对于第1个理论化学交换特征定量的n个CEST信号的n个信号强度理论值。
对于第2个理论化学交换特征定量(K 1,c 2)，计算第1～n个CEST信号的信号强度理论值的参量分别为[(K 1,c 2)、F1、(ω 1，T s1)]、[(K 1,c 2)、F1、(ω 2，T s2)]…[(K 1,c 2)、F1、(ω n，T sn)]，对应计算出1～n个信号强度理论值CEST 2 ideal1、CEST 2 ideal2…CEST 2 idealn。
按照相同的方法，可依次计算每一个理论化学交换特征定量对应第1至第n个CEST信号的信号强度理论值。由于每一个理论化学交换特征定量均可对应计算出一个信号强度理论值，则从理论化学交换特征定量范围中选取多个理论化学交换特征定量后，针对于一个CEST对比剂通过理论计算可得到与其信号强度实测值对应的多个信号强度理论值。
S103，将每种CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为CEST对比剂的化学交换特征定量结果。
可选地，利用点乘最大化原则等算法，将每一个CEST对比剂的CEST信号的信号强度实测值与对应的多个信号强度理论值进行匹配；例如，施加n个饱和脉冲后记录CEST信号的n个信号强度实测值为CEST acq1、CEST acq2、CEST acq3…、CEST acqn，在对应于这n个信号强度实测值的多个信号强度理论值中，寻找与实测值CEST acq1、CEST acq2、CEST acq3…、CEST acqn匹配度最高的n个理论值CEST ideal1、 CEST ideal2、CEST ideal3…CEST idealn，这n个理论值在计算过程中对应的理论化学交换特征定量即为目标物体的磁化转移效应的化学交换特征定量。
例如，在S102计算时所采用的理论化学交换特征定量中，第m个理论化学交换特征定量(K i,c j)∈[(K 1,c 1)、(K 1,c 2)、(K 1,c 3)…(K q,c q)]所对应的n个理论值CEST m ideal1、CEST m ideal2、CEST m ideal3…CEST m idealn与n个信号强度实测值CEST ideal1、CEST ideal2、CEST ideal3、…、CEST idealn的匹配程度最高，则理论化学交换特征定量(K i,c j)即为CEST对比剂的化学交换特征定量结果。
对每个CEST对比剂的CEST信号的信号强度实测值均与对应的多个信号强度理论值进行匹配，匹配结果对应的理论化学交换特征定量即为每个CEST对比剂的化学交换特征定量结果。
本申请的实施例针对于每一个CEST对比剂的CEST信号的信号强度实测值，在信号强度理论值进行计算时与信号强度实测值在采集时的采集环境，即饱和脉冲参数、共振频率相同，因此基于理论化学交换特征定量范围，可以计算出多个与信号强度实测值对应的信号强度理论值；由于信号强度理论值是在与信号强度实测值采集时相同的采集环境下计算得到的多个值，采用一对多的匹配方式使得信号强度实测值能有更准确的匹配结果。本申请的化学交换特征定量过程无需选择参照信号，因此不易受到其他化学交换效应的影响，由此使得匹配结果对应的理论化学交换特征定量能更准确地代表实际的化学交换特定量，故有效地提高了化学交换特定量的准确率。
在一个示例中，S101之前还可以包括S100-1和S100-2：
S100-1，根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；所述有效成像范围中的参数为饱和脉冲参数。
示例性的，CEST对比剂的化学交换特征可以是例如化学交换速率和/或浓度等。有效成像范围即为针对于该CEST对比剂的饱和脉冲参数施加的一个有效范围，在该范围内，CEST对比剂具有较好的成像效果。各CEST对比剂的有效成像范围可通过实验来确定，即针对于不同的饱和脉冲参数，分别进行CEST对比剂的成像实验，然后根据成像效果来选定一个具有较好成像效果的饱和脉冲参数范围，作为该CEST对比剂的有效成像范围。还可以通过先验知识进行确定，例如通过查询已有资料中该CEST对比剂成像时惯用的饱和脉冲参数范围作为有 效成像范围。
S100-2，根据所有所述CEST对比剂的有效成像范围，确定所述饱和脉冲的饱和脉冲参数范围；其中，所述饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
在S100-2中，选定的饱和脉冲参数范围中的饱和脉冲参数，应该同时属于所有CEST对比剂的有效成像范围，这样在施加饱和脉冲时，随机选择的饱和脉冲可在不同的CEST对比剂的共振频率上满足该CEST对比剂的成像要求。
需要说明的是，当饱和脉冲参数选择一种以上的组合时，例如选择脉冲强度ω 1、持续时间T s时，所对应的饱和脉冲参数范围也是两个，即对应于脉冲强度的饱和脉冲参数范围以及对应于持续时间的饱和脉冲参数范围。
以饱和脉冲参数选择两种，即选择脉冲强度、持续时间这两种饱和脉冲参数为例，如针化学交换速率较慢(10-100Hz)的CEST对比剂，其有效成像范围可以是：饱和脉冲强度为0.5-4.0μT，持续时间为30-100ms，代表性的CEST对比剂有-NH等；而针对交换速率较快(500-1500Hz)的CEST对比剂，其有效成像范围可以是：饱和脉冲强度>2.0μT，持续时间<50ms，代表性的CEST对比剂有-OH等。该示例中，饱和脉冲参数范围可以选择：饱和脉冲强度0.5～5μT，持续时间10～100ms。
现有技术中，CEST成像中饱和脉冲参数的选取往往由经验而来，且在数据采集过程中其参数保持恒定，每次仅能对单一CEST对比剂实施有效定量，一方面较难获取最佳CEST效应，另一方面，又难以同时对具备不同化学交换特性的多种CEST对比剂实施有效定量。本申请的实施例中，根据CEST对比剂的化学交换特征，首先确定各CEST对比剂的有效成像范围，在此基础上确定饱和脉冲参数范围。在进行CEST定量时，以设定的步长改变饱和脉冲频率，可依次在每个CEST对比剂的共振频率上进行饱和脉冲的施加，由此可对不同CEST对比剂进行同步定量；且依据CEST对比剂化学交换特征确定的饱和脉冲参数范围内采集的CEST数据能更好地获取CEST效应。
请参阅图3，在一种可能的实现方式中，S101可以包括S1011～S1014，该示例中采用设定频率范围并从中选取多个频率，在每个频率上均施加饱和脉冲，从探测到的所有的CEST信号的信号强度实测值中提取每个CEST对比剂对应的 CEST信号的信号强度实测值，具体如下：
S1011，根据多种CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率。
可选地，将各CEST对比剂的共振频率对应的频率范围与主磁场的频率范围求并集，将结果作为饱和脉冲的频率范围，由此确定的频率范围中即涵盖各CEST对比剂的共振频率。作为一种通用的表述习惯，常采用频率偏移对频率进行说明。频率偏移和频率之间存在换算关系，具体为：
频率偏移＝(f-f 0)×10 6/f 0ppm    式1
式1中，f表示CEST对比剂的共振频率或施加饱和脉冲的频率，f 0为参考频率，例如采用水的共振频率作为参考频率。
例如，内源性CEST对比剂相对于水分子的共振频率偏移通常在-4～4ppm，若主磁场的频率偏移在-1～1ppm范围内，则饱和脉冲的频率偏移范围可以选择-5～5ppm。
本实施例中，以同时探测生物体组织内的三种CEST对比剂：氨基(-NH，3.5ppm)、胺基(-NH 2，2ppm)、谷氨酸盐(3ppm)为例，这三种CEST对比剂的共振频率偏移对应的频率偏移范围为2～3.5ppm，在主磁场频率偏移为-1～1ppm时，饱和脉冲的频率偏移范围可选择1～4.5ppm。确定频率偏移范围之后，通过式1将频率偏移范围转换成频率，即得到频率范围。
S1012，从饱和脉冲的频率范围中选择多个频率，多个频率包含各CEST对比剂的共振频率。
在确定饱和脉冲的频率范围后，以合适的步长对频率范围进行划分。其中步长的选取应该满足使得划分后的多个频率包含各CEST对比剂的共振频率。以频率偏移为例进行说明：
在饱和脉冲的频率偏移范围1～4.5ppm内，选择适当的频率偏移步长，例如待探测的CEST对比剂为氨基(-NH，3.5ppm)、胺基(-NH 2，2ppm)、谷氨酸盐(3ppm)三种，共振频率偏移分别为3.5ppm、2ppm、3ppm，则可以选择频率偏移步长为0.5ppm；即频率偏移步长满足被待探测的多种CEST对比剂的共振频率偏移整除时，即可满足划分后的多个频率偏移满足涵盖各个CEST对比剂共振频率的要求。将偏移步长、频率偏移按照式1转换成频率，即得到步长以及 划分后的频率。
S1013，在多个频率中的每个频率上按预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值。
在每个频率上按照预设条件施加饱和脉冲后，均可以探测到对应于该频率的CEST信号的信号强度实测值。以将频率范围划分成多个频率[f1,f2,f3,…]，每个频率上施加n组饱和脉冲进行说明。
首先在第一个频率f1上施加饱和脉冲，施加之前先在设定的饱和脉冲参数范围内随机化选择饱和脉冲参数，按照选择的饱和脉冲参数施加饱和脉冲，即可探测到在该频率上的第一个CEST信号的信号强度实测值。同样是在该频率上，再次随机化选择饱和脉冲参数，按照随机化后的饱和脉冲参数施加饱和脉冲，探测到该频率上的第二个CEST信号的信号强度实测值；按照同样的方法，直至n个饱和脉冲均施加完毕之后，得到所有针对于第一个频率f1的n个CEST信号的信号强度实测值。在其他的频率f2,f3,…都依照此方法，即可得到每个频率对应的CEST信号的信号强度实测值。
S1014，从每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为CEST对比剂的CEST信号的信号强度实测值。
由于设定的频率范围中的频率涵盖每个CEST对比剂的共振频率，所以针对一个CEST对比剂，通过提取出与其共振频率相同的饱和脉冲施加频率时所探测到的CEST信号的信号强度实测值，即为该CEST对比剂的CEST信号的信号强度实测值。
因为每个频率上施加的饱和脉冲是n组，故提取出的CEST对比剂的CEST信号的实测值CEST acq也有n个，这n个实测值反映出了该CEST对比剂的CEST信号的信号强度随n个饱和脉冲参数的变化情况。
由于在CEST信号的信号强度实测值采集时可能存在主磁场偏移，实际采集的频率点会有偏差，故本实施例采用上述首先设定频率范围，然后将在频率范围内选择多个频率，在每个频率上分别采集信号强度实测值，在从所有信号强度实测值中提取每个CEST对比剂的CEST信号的信号强度实测值的方法，该方法可在每个CEST对比剂的共振频率附近采集多个频率点的数据，然后采用水饱和移 位(water saturation shift referencing,WASSR)校正法等方法进行主磁场校正以获取频率校正后各CEST对比剂的CEST信号的信号强度实测值；校正后的实测值具有更高的准确性，后续的处理过程采用的是校正后的CEST信号的信号强度实测值。
在进行CEST对比剂化学交换特征定量过程中，自由水的磁化转移(Magnetization Transfer，MT)效应相对较强，干扰CEST信号。
在一个可选的示例中，为避免MT效应对CEST信号强度的影响，S102之前，还包括：
S1-102，量化所述目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果。
其中，S1-102在S101之后执行。
基于上述磁化转移效应的化学交换特征定量结果，如图4所示，S102可以具体包括S1021～S1023：
S1021，获取每种CEST对比剂的CEST信号对应的第一生成条件，第一生成条件包括CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数。
第一生成条件，即S101中采集CEST信号的信号强度实测值时对应的条件。在S101中采集CEST信号的信号强度实测值时，需要在CEST对比剂的共振频率上按照预设条件施加饱和脉冲。其中预设条件中包含饱和脉冲参数范围，采集信号强度实测值时饱和脉冲对应的饱和脉冲参数在设定的饱和脉冲参数范围内随机化；例如上述示例中，对于第1个饱和脉冲施加后采集到的CEST信号，第一生成条件为CEST对比剂的共振频率F 1，以及饱和脉冲参数：脉冲强度ω 1、持续时间T s。
S1022，确定每种CEST对比剂的理论化学交换特征定量范围。
可选地，采用以往的实验数据来确定每种CEST对比剂的理论化学交换特征定量范围。例如，根据以往的实验数据，CEST对比剂氨基(-NH，3.5ppm)的理论化学交换特征定量范围可以是：化学交换速率范围50-500Hz，浓度范围100-1000mM。
S1023，基于理论化学交换特征定量范围中不同的理论化学交换特征定量，利用磁化转移效应的化学交换特征定量结果计算在第一生成条件下生成的CEST 信号所对应的多个信号强度理论值。
可选地，在一个实施例中，计算CEST信号对应的多个信号强度理论值时利用三化学交换池Bloch方程。其中，三化学交换池Bloch方程是指自由水、磁化转移MT Bloch方程；例如对于第1个饱和脉冲施加后采集的CEST信号，通过该方程，利用磁化转移效应的化学交换特征定量结果、第一生成条件中的共振频率F1，以及饱和脉冲参数：脉冲强度ω 1、持续时间T s，可计算得到对于对于CEST对比剂的不同理论化学交换特征定量时的多个信号强度理论值。
三化学交换池Bloch方程考虑了自由水和磁化转移效应，因此在CEST信号的信号强度理论值时可有效地排除自有水的直接饱和效应和磁化转移效应，使得理论值的计算结果更加精准。
可选地，根据计算得到的CEST信号的信号强度的理论值，可进一步建立每一个CEST对比剂的CEST信号字典集以保存每一个CEST信号的多个信号强度实测值，以便于后续的匹配过程。
请参阅图5，作为一个具体的示例，如图5所示，S1-102还可以包括：S1-1021～S1-1023：
S1-1021，获取在远离自由水和所有CEST对比剂的共振频率上，按照预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值。
其中，远离自由水和所有CEST对比剂的共振频率，例如选择共振频率偏移为10ppm处。自由水的共振频率偏移为0ppm，本实施例中列举的三种CEST对比剂：氨基(-NH，3.5ppm)、胺基(-NH 2，2ppm)、谷氨酸盐(3ppm)的共振频率偏移范围为2～3.5ppm，因此10ppm的共振频率偏移相对于自由水和CEST对比剂的共振频率已足够远，故在10ppm的共振频率偏移处所对应的共振频率上施加饱和脉冲可以满足获取磁化转移效应的化学交换特征定量的需求。10ppm处的共振频率已经是一个比较远的共振频率，满足一般情况下多数CEST对比剂进行磁化转移效应的化学交换特征定量的需求。需要说明的是，此处的列举只是示意性的，不是限制性的；也可以选择8ppm、9ppm、11ppm等其他共振频率进行饱和脉冲的施加。“远离”，可以理解成是在所有CEST对比剂的共振频率中，选择最大的一个共振频率值，在这个值对应的共振频率偏移的数值上加f，得到的共振频率偏移所对应的共振频率即可理解为远离自由水和CEST对比剂的共 振频率；其中f可以是一个自然数，例如其取值>2ppm。
在确定好上述远离自由水和所有CEST对比剂的共振频率后，按照预设条件对目标物体施加饱和脉冲。这里的预设条件与S101中预设条件相同，即依次施加至少一个饱和脉冲，每个饱和脉冲参数在设定的饱和脉冲参数范围内随机化。其中，饱和脉冲参数范围也可以与S101中相同。
在确定的共振频率上施加饱和脉冲，每个饱和脉冲的饱和脉冲参数在设定的饱和脉冲参数范围内随机化，采集施加饱和脉冲后产生的磁化转移信号的信号强度实测值MT acq。饱和脉冲的数量与采集的磁化转移信号的数量存在对应关系，当依次施加多个饱和脉冲时，可对应采集到多个磁化转移信号的信号强度实测值。本实施例中，采集磁化转移信号时与采集CEST信号施加饱和脉冲数量一致，即最终采集到n个磁化转移信号的信号强度实测值。
S1-1022，基于磁化转移信号的理论化学交换特征定量范围，计算磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同。
该步骤中，通过理论计算的方法确定磁化转移信号在不同理论化学交换特征定量时的多个信号强度理论值。其中，化学交换特征可以是化学交换速率和/或浓度等，在化学交换特征选择化学交换速率和浓度时，理论化学交换特征定量范围指化学交换速率范围和浓度范围。磁化转移信号的理论化学交换特征定量范围可以通过先验知识确定，例如通过以往的试验数据，或通过查询资料的方式来确定。
基于磁化转移信号的理论化学交换特征定量范围，在与磁化转移信号的信号强度实测值采集时相同的饱和脉冲参数、共振频率条件下，可计算多个与磁化转移信号对应的信号强度理论值。例如，可利用理论化学交换特征定量范围中不同的理论化学交换特征定量进行计算，针对于一个磁化转移信号的理论化学交换特征定量，通过理论计算的方式可得到一个信号强度理论值；那么将范围中的多个理论化学交换特征定量分别计算信号强度理论值，即可得到对应于磁化转移信号的多个信号强度理论值。由于针对一磁化转移信号可探测到一个信号强度实测值，因此信号强度理论值与信号强度实测值存在多对一的对应关系。
当针对于目标物体施加多个饱和脉冲而采集了多个磁化转移信号时，在计算每个磁化转移信号的对应的多个信号强度理论值过程中，首先从磁化转移信号的理论化学交换特征定量范围中选取多个理论化学交换特征定量，按照取出的化学交换特征定量，依次计算在每个化学交换特征定量下，每个磁化转移信号的信号强度理论值。
例如，在采集磁化转移信号的信号强度实测值时确定的远离自由水和所有CEST对比剂的共振频率为F2，预设条件中，设定施加n个饱和脉冲，设定的饱和脉冲参数范围是：脉冲强度ω 0～ω a、持续时间T s0～T sb。磁化转移信号的理论化学交换特征定量范围为：化学交换速率范围K’，浓度范围c’。在理论化学交换特征定量范围中选择多个理论化学交换特征定量，例如在化学交换速率范围K’中等间隔选取a个化学交换速率K’ 1、K’ 2…K’ a，在浓度范围c’中等间隔选取b个浓度c’ 1、c’ 2…c’ b，则化学交换速率、浓度共可以构成a×b个组合(K’ 1,c’ 1)、(K’ 1,c’ 2)、(K’ 1,c’ 3)…(K’ a,c’ b)，也即a×b个理论化学交换特征定量。
在采集磁化转移信号的信号强度实测值时：
在共振频率F2上施加第1至第n个饱和脉冲，随机选择的饱和脉冲参数(脉冲强度,持续时间)分别为：(ω’ 1，T’ s1)、(ω’ 2，T’ s2)…(ω’ n，T’ sn)，其中，ω’ 1,ω’ 2,…ω’ n∈(ω 0～ω a)，T’ s1,T’ s2,…T’ sn∈(T s0～T sb)。则采集到的第1个至第n个磁化转移信号的信号强度实测值分别为MT acq1、MT acq2…MT acqn。
在计算磁化转移信号对应的多个信号强度理论值时：
对于第1个理论化学交换特征定量，本例中为第1个化学交换速率和第1个浓度(K’ 1,c’ 1)，计算第1～n个磁化转移信号的信号强度理论值时，分别将共振频率F2，以及采集1～n个磁化转移信号的信号强度实测值时的饱和脉冲参数(ω’ 1，T’ s1)、(ω’ 2，T’ s2)…(ω’ n，T’ sn)作为计算条件，计算得到第1～n个信号强度理论值MT 1 ideal1、MT 1 ideal2…MT 1 idealn。即，第1个信号强度理论值MT 1 ideal1在计算时所用的参量为：[(K’ 1,c’ 1)、F2、(ω’ 1，T’ s1)]；第2个信号强度理论值MT 1 ideal2在计算时所用的参量为：[(K’ 1,c’ 1)、F2、(ω’ 2，T’ s2)]…第n个信号强度理论值MT 1 idealn在计算时所用的参量为：[(K’ 1,c’ 1)、F2、(ω’ n，T’ sn)]。
通过以上方法，计算得到了针对于第1个理论化学交换特征定量的n个磁化转移信号的n个信号强度理论值。
对于第2个理论化学交换特征定量(K’ 1,c’ 2)，计算第1～n个CEST信号的信号强度理论值的参量分别为[(K’ 1,c’ 2)、F2、(ω’ 1，T’ s1)]、[(K’ 1,c’ 2)、F2、(ω’ 2，T’ s2)]…[(K’ 1,c’ 2)、F2、(ω’ n，T’ sn)]，对应计算出1～n个信号强度理论值MT 2 ideal1、MT 2 ideal2…MT 2 idealn。
按照相同的方法，可依次计算每一个理论化学交换特征定量对应第1至第n个磁化转移信号的信号强度理论值。由于每一个理论化学交换特征定量均可对应计算出一个信号强度理论值，则从理论化学交换特征定量范围中选取多个理论化学交换特征定量后，针对于一个磁化转移信号通过理论计算可得到与其信号强度实测值对应的多个信号强度理论值。
S1-1023，将磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为目标物体的磁化转移效应的化学交换特征定量结果。
可选地，利用点乘最大化原则等算法，将磁化转移信号的信号强度实测值与对应的多个信号强度理论值进行匹配；例如，施加n个饱和脉冲后记录磁化转移信号的n个信号强度实测值为MT acq1、MT acq2、MT acq3…、MT acqn，在磁化转移信号字典集中存储的对应于这n个信号强度实测值的多个信号强度理论值中，寻找与实测值MT acq1、MT acq2、MT acq3…、MT acqn匹配度最高的n个理论值，这n个理论值在计算过程中对应的理论化学交换特征定量即为目标物体的磁化转移效应的化学交换特征定量。
例如，在S1-1022计算时采用的理论化学交换特征定量中，第k个理论化学交换特征定量(K’ i,c’ j)∈[(K’ 1,c’ 1)、(K’ 1,c’ 2)、(K’ 1,c’ 3)…(K’ a,c’ b)]所对应的n个理论值MT k ideal1、MT k ideal2、MT k ideal3…MT k idealn与n个信号强度实测值MT acq1、MT acq2、MT acq3…、MT acqn匹配度最高，则理论化学交换特征定量(K’ i,c’ j)即为目标物体的磁化转移效应的化学交换特征定量结果。
本申请的实施例中，采用计算磁化转移信号的信号强度理论值的方法，使得对于每一个磁化转移信号的信号强度实测值，都有多个对应的信号强度理论值；由于这些理论值是基于理论化学交换特征定量范围、并且在与实测值采集时相同的共振频率和饱和脉冲参数条件下计算得出的，故实测值可精确地找到匹配度最高的理论值，从而使得磁化转移效应定量结果更加精确。可以在理论化学交换特 征定量范围中选择更多的定量值计算更多的信号强度理论值，以进一步提升磁化转移效应定量结果的精确程度。
在一个可选的示例中，如图6所示，S1-1022还可以包括S1-10221～S1-10223：
S1-10221，获取磁化转移信号对应的第二生成条件，第二生成条件包括远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数。
第二生成条件，即S1-10221中采集磁化转移信号的信号强度实测值时对应的条件。在S1-10221中采集磁化转移信号的信号强度实测值时，需要确定在远离自由水和所有CEST对比剂的共振频率，并按照预设条件施加饱和脉冲。其中预设条件中包含饱和脉冲参数范围，采集信号强度实测值时饱和脉冲对应的饱和脉冲参数在设定的饱和脉冲参数范围内随机化；例如上述示例中，对于第1个饱和脉冲施加后采集到的磁化转移信号，第二生成条件为远离自由水和所有CEST对比剂的共振频率为F2，以及饱和脉冲参数：脉冲强度ω’ 1、持续时间T’ s。
S1-10222，确定磁化转移信号的理论化学交换特征定量范围；
该示例中，磁化转移信号的理论化学交换特征定量范围通过以往的试验数据得到，示例性的，磁化转移信号的理论化学交换特征定量范围中，化学交换速率K范围设置为5-100Hz，浓度c范围2-30M。
S1-10223，基于理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
可选地，在一个实施例中，计算磁化转移信号对应的多个信号强度理论值时利用双化学交换池Bloch方程。其中，双化学交换池Bloch方程是指自由水、磁化转移MT Bloch方程；例如对于第1个饱和脉冲施加后采集的磁化转移信号，通过该方程，利用第二生成条件中的共振频率为F2，以及饱和脉冲参数：脉冲强度ω’ 1、持续时间T’ s，可计算得到对于磁化转移信号的不同理论化学交换特征定量时的多个信号强度理论值。
可选地，根据计算得到磁化转移信号的信号强度的理论值，可进一步建立磁化转移信号字典集以保存每一个磁化转移信号的多个信号强度实测值，以便于后续的匹配过程。
如图7所示，图7中展示出了一个CEST对比剂的CEST信号的多个信号强 度理论值。为了更加直观地看到信号强度理论值的变化情况，图7中以饱和脉冲序号作为横坐标轴，将不同饱和脉冲对应的CEST信号强度的理论值依次连接，即得到了不同理论化学交换特征定量所对应的信号强度理论值随饱和脉冲序号的变化曲线。图7的示例中，共有8条变化曲线，即有8个理论化学交换特定量对应的信号强度理论值变化曲线。如图8所示，为CEST信号的实测值随饱和脉冲序号的变化曲线。如图9所示，将图8中的曲线在图7中进行匹配，匹配度最高的一条变化曲线中各个信号强度理论值对应的理论化学交换特征定量即CEST对比剂的化学交换特征定量。从图9的匹配结果可以看出，本申请实施例的方法有很高的匹配程度。
本申请的实施例中对磁化转移效应进行了定量，在进行CEST信号的信号强度理论值计算过程中，消除了磁化转移效应对计算环境的影响，从而使得计算得到的信号强度理论值是在更为贴近目标物体真实环境下得出的，相比于传统方法依赖参考信号的准确性的局限，本申请中由于能够对磁化转移效应进行准确量化，因此能有效地去除磁化转移效应，进一步地提升了定量结果的准确率。
将每个CEST对比剂的化学交换特征定量结果以伪彩图等方式制图，即可得到各CEST对比剂的同步定量成像结果。
图10示出了本申请提供的一种化学交换特征定量装置，本实施例中的化学交换特征定量装置包含的各模块用于执行上述方法实施例中图1、图3～图6各自对应的实施例，具体实现过程可参阅上述实施例的相关描述，此次不赘述。化学交换特征定量装置包括：
第一采集模块1，用于采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，CEST信号在对CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；
第一计算模块2，用于基于每种CEST对比剂对应的理论化学交换特征定量范围，计算每种CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲参数、共振频率相同；
第一匹配模块3，用于将每种CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理 论值对应的理论化学交换特征定量作为CEST对比剂的化学交换特征定量结果。
可选地，化学交换特征定量装置还包括：
第一设定模块，用于根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；有效成像范围中的参数为饱和脉冲参数；
第二设定模块，用于根据所有CEST对比剂的有效成像范围，确定饱和脉冲的饱和脉冲参数范围；其中，饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
进一步地，预设条件为：依次施加至少一个饱和脉冲，每个饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
可选地，如图11所示，第一采集模块1包括：
频率范围设定单元11，用于根据多种CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；
频率选择单元12，用于从饱和脉冲的频率范围中选择多个频率，多个频率包含各CEST对比剂的共振频率；
第一采集子单元13，用于在多个频率中的每个频率上按预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；
提取单元14，用于从每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为CEST对比剂的CEST信号的信号强度实测值。
进一步地，化学交换特征定量装置还包括：
量化模块4，用于量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果；
如图12所示，第一计算模块2包括：
第一获取单元21，用于获取每种CEST对比剂的CEST信号对应的第一生成条件，第一生成条件包括CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
第一确定单元22，用于确定每种CEST对比剂的理论化学交换特征定量范围；
第一计算子单元23，用于基于理论化学交换特征定量范围中不同的理论化学交换特征定量，利用磁化转移效应的化学交换特征定量结果计算在第一生成条件下生成的CEST信号所对应的多个信号强度理论值。
可选地，如图13所示，量化模块4包括：
第二采集模块41，用于获取在远离自由水和所有CEST对比剂的共振频率上，按照预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；
第二计算模块42，用于基于磁化转移信号的理论化学交换特征定量范围，计算磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同；
第二匹配模块43，用于将磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为目标物体的磁化转移效应的化学交换特征定量结果。
进一步地，第二计算模块包括：
第二获取单元，用于获取磁化转移信号对应的第二生成条件，第二生成条件包括远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
第二确定单元，用于确定磁化转移信号的理论化学交换特征定量范围；
第二计算子单元，用于基于理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
需要说明的是，上述模块/单元之间的信息交互、执行过程等内容，由于与本申请方法实施例基于同一构思，其具体功能及带来的技术效果，具体可参见方法实施例部分，此处不再赘述。
请参阅图14，本申请实施例进一步提供一种化学交换特征定量设备5，如图14所示，包括存储器52、处理器51以及存储在存储器52中并可在处理器上运行的计算机可读指令53，处理器51执行计算机可读指令53时实现上述化学交换特征定量方法，例如，图1所示的S101至S103。
计算机可读指令53也可以被分割成一个或多个模块/单元，一个或者多个模 块/单元被存储在存储器52中，并由处理器51执行，以完成本申请。一个或多个模块/单元可以是能够完成特定功能的一系列计算机可读指令指令段，该指令段用于描述计算机可读指令53在化学交换特征定量设备5中的执行过程，例如，计算机可读指令53可以被分割为第一采集模块、第一计算模块、第一匹配模块，各模块的功能参见前述系统中的描述，不再赘述。
本申请的实施提供了一种计算机可读存储介质，计算机可读存储介质存储有计算机可读指令，计算机可读指令被处理器执行时实现上述化学交换特征定量方法，例如，图1所示的S101至S103。
集成的模块/单元如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本申请实现上述实施例方法中的全部或部分流程，也可以通过计算机可读指令来指令相关的硬件来完成，计算机可读指令可存储于一计算机可读存储介质中，该计算机可读指令在被处理器执行时，可实现上述各个方法实施例的步骤。其中，计算机可读指令包括计算机可读指令代码，计算机可读指令代码可以为源代码形式、对象代码形式、可执行文件或某些中间形式等。计算机可读介质可以包括：能够携带计算机可读指令代码的任何实体或装置、记录介质、U盘、移动硬盘、磁碟、光盘、计算机存储器、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、电载波信号、电信信号以及软件分发介质等。需要说明的是，计算机可读介质包含的内容可以根据司法管辖区内立法和专利实践的要求进行适当的增减，例如在某些司法管辖区，根据立法和专利实践，计算机可读介质不包括电载波信号和电信信号。
本申请的实施例还提供了一种计算机可读指令产品，当计算机可读指令产品在化学交换特征定量设备上运行时，使得化学交换特征定量设备执行上述化学交换特征定量方法，例如，图1所示的S101至S103。
以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围，均应包含在本申请的保护范围之内。

Claims (24)

  1. 一种化学交换特征定量方法，其特征在于，包括：
    采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，所述CEST信号在对所述CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；
    基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲参数、共振频率相同；
    将每种所述CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述CEST对比剂的化学交换特征定量结果。
  2. 根据权利要求1所述的化学交换特征定量方法，其特征在于，所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值之前，还包括：
    根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；所述有效成像范围中的参数为饱和脉冲参数；
    根据所有所述CEST对比剂的有效成像范围，确定所述饱和脉冲的饱和脉冲参数范围；其中，所述饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
  3. 根据权利要求1或2所述的化学交换特征定量方法，其特征在于，所述预设条件为：
    依次施加至少一个饱和脉冲，每个所述饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
  4. 根据权利要求1所述的化学交换特征定量方法，其特征在于，所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值，包括：
    根据多种所述CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，所述饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；
    从所述饱和脉冲的频率范围中选择多个频率，所述多个频率包含各CEST对比剂的共振频率；
    在所述多个频率中的每个频率上按所述预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；
    从所述每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为所述CEST对比剂的CEST信号的信号强度实测值。
  5. 根据权利要求1所述的化学交换特征定量方法，其特征在于，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值之前，还包括：
    量化所述目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果；
    相应地，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值，包括：
    获取每种所述CEST对比剂的CEST信号对应的第一生成条件，所述第一生成条件包括所述CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定每种所述CEST对比剂的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，利用所述磁化转移效应的化学交换特征定量结果计算在所述第一生成条件下生成的CEST信号所对应的多个信号强度理论值。
  6. 根据权利要求5所述的化学交换特征定量方法，其特征在于，所述量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果，包括：
    获取在远离自由水和所有CEST对比剂的共振频率上，按照所述预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；
    基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值 时所对应的饱和脉冲参数、共振频率相同；
    将所述磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述目标物体的磁化转移效应的化学交换特征定量结果。
  7. 根据权利要求6所述的化学交换特征定量方法，其特征在于，所述基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值，包括：
    获取所述磁化转移信号对应的第二生成条件，所述第二生成条件包括所述远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定所述磁化转移信号的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在所述第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
  8. 根据权利要求1、2、4至7中任一权利要求所述的化学交换特征定量方法，其特征在于，所述饱和脉冲参数包括：脉冲强度、持续时间、翻转角、占空比中的任一种或一种以上的组合。
  9. 一种化学交换特征定量设备，包括存储器、处理器以及存储在所述存储器中并可在所述处理器上运行的计算机可读指令，其特征在于，所述处理器执行计算机可读指令时实现以下步骤：
    采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，所述CEST信号在对所述CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；
    基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲参数、共振频率相同；
    将每种所述CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述CEST对比剂的化学交换特征定量结果。
  10. 根据权利要求9所述的化学交换特征定量设备，其特征在于，在所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值之前，所述处理器执行计算机可读指令时还实现以下步骤：
    根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；所述有效成像范围中的参数为饱和脉冲参数；
    根据所有所述CEST对比剂的有效成像范围，确定所述饱和脉冲的饱和脉冲参数范围；其中，所述饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
  11. 根据权利要求9或10所述的化学交换特征定量设备，其特征在于，所述预设条件为：
    依次施加至少一个饱和脉冲，每个所述饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
  12. 根据权利要求9所述的化学交换特征定量设备，其特征在于，所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值，包括：
    根据多种所述CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，所述饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；
    从所述饱和脉冲的频率范围中选择多个频率，所述多个频率包含各CEST对比剂的共振频率；
    在所述多个频率中的每个频率上按所述预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；
    从所述每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为所述CEST对比剂的CEST信号的信号强度实测值。
  13. 根据权利要求9所述的化学交换特征定量设备，其特征在于，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值之前，所述处理器执行计算机可读指令时还实现以下步骤：
    量化所述目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定 量结果；
    相应地，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值，包括：
    获取每种所述CEST对比剂的CEST信号对应的第一生成条件，所述第一生成条件包括所述CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定每种所述CEST对比剂的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，利用所述磁化转移效应的化学交换特征定量结果计算在所述第一生成条件下生成的CEST信号所对应的多个信号强度理论值。
  14. 根据权利要求13所述的化学交换特征定量设备，其特征在于，所述量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果，包括：
    获取在远离自由水和所有CEST对比剂的共振频率上，按照所述预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；
    基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同；
    将所述磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述目标物体的磁化转移效应的化学交换特征定量结果。
  15. 根据权利要求14所述的化学交换特征定量设备，其特征在于，所述基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值，包括：
    获取所述磁化转移信号对应的第二生成条件，所述第二生成条件包括所述远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定所述磁化转移信号的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在所述第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
  16. 根据权利要求9、10、12至15任一项所述的化学交换特征定量设备，其特征在于，所述饱和脉冲参数包括：脉冲强度、持续时间、翻转角、占空比中的任一种或一种以上的组合。
  17. 一种计算机可读存储介质，计算机可读存储介质存储有计算机可读指令，其特征在于，计算机可读指令被处理器执行时实现如下步骤：
    采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值；其中，所述CEST信号在对所述CEST对比剂的共振频率上按预设条件施加饱和脉冲时产生；
    基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值；其中，每个CEST信号的信号强度理论值在计算时对应的饱和脉冲参数、共振频率与其信号强度实测值对应的饱和脉冲参数、共振频率相同；
    将每种所述CEST对比剂各自对应的CEST信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述CEST对比剂的化学交换特征定量结果。
  18. 根据权利要求17所述的计算机可读存储介质，其特征在于，所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值之前，还包括：
    根据各CEST对比剂的化学交换特征，确定各CEST对比剂的有效成像范围；所述有效成像范围中的参数为饱和脉冲参数；
    根据所有所述CEST对比剂的有效成像范围，确定所述饱和脉冲的饱和脉冲参数范围；其中，所述饱和脉冲参数范围中的饱和脉冲参数属于各CEST对比剂的有效成像范围。
  19. 根据权利要求17或18所述的计算机可读存储介质，其特征在于，所述预设条件为：
    依次施加至少一个饱和脉冲，每个所述饱和脉冲参数在设定的饱和脉冲参数范围内随机化。
  20. 根据权利要求17所述的计算机可读存储介质，其特征在于，所述采集目标物体中待探测的多种化学交换饱和转移CEST对比剂各自的CEST信号的信号强度实测值，包括：
    根据多种所述CEST对比剂的共振频率，确定待施加的饱和脉冲的频率范围；其中，所述饱和脉冲的频率范围中的频率涵盖各CEST对比剂的共振频率；
    从所述饱和脉冲的频率范围中选择多个频率，所述多个频率包含各CEST对比剂的共振频率；
    在所述多个频率中的每个频率上按所述预设条件施加饱和脉冲时，采集每个频率对应的CEST信号的信号强度实测值；
    从所述每个频率对应的CEST信号的信号强度实测值中，提取每个CEST对比剂的共振频率对应的CEST信号的信号强度实测值作为所述CEST对比剂的CEST信号的信号强度实测值。
  21. 根据权利要求17所述的计算机可读存储介质，其特征在于，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值之前，还包括：
    量化所述目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果；
    相应地，所述基于每种所述CEST对比剂对应的理论化学交换特征定量范围，计算每种所述CEST对比剂各自的CEST信号对应的多个信号强度理论值，包括：
    获取每种所述CEST对比剂的CEST信号对应的第一生成条件，所述第一生成条件包括所述CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定每种所述CEST对比剂的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，利用所述磁化转移效应的化学交换特征定量结果计算在所述第一生成条件下生成的CEST信号所对应的多个信号强度理论值。
  22. 根据权利要求17所述的计算机可读存储介质，其特征在于，所述量化目标物体的磁化转移效应，得到磁化转移效应的化学交换特征定量结果，包括：
    获取在远离自由水和所有CEST对比剂的共振频率上，按照所述预设条件施加饱和脉冲时，采集的磁化转移信号的信号强度实测值；
    基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值；其中，在计算磁化转移信号的信号强度理论值时所对应的饱和脉冲参数以及共振频率，与生成磁化转移信号的信号强度实测值时所对应的饱和脉冲参数、共振频率相同；
    将所述磁化转移信号的信号强度实测值与其对应的多个信号强度理论值进行匹配，将匹配度最高的信号强度理论值对应的理论化学交换特征定量作为所述目标物体的磁化转移效应的化学交换特征定量结果。
  23. 根据权利要求22所述的计算机可读存储介质，其特征在于，所述基于所述磁化转移信号的理论化学交换特征定量范围，计算所述磁化转移信号对应的多个信号强度理论值，包括：
    获取所述磁化转移信号对应的第二生成条件，所述第二生成条件包括所述远离自由水的信息和所有CEST对比剂的共振频率，以及施加饱和脉冲时对应的饱和脉冲参数；
    确定所述磁化转移信号的理论化学交换特征定量范围；
    基于所述理论化学交换特征定量范围中不同的理论化学交换特征定量，计算在所述第二生成条件下生成的磁化转移信号所对应的多个信号强度理论值。
  24. 根据权利要求17、18、20至23任一项所述的计算机可读存储介质，其特征在于，所述饱和脉冲参数包括：脉冲强度、持续时间、翻转角、占空比中的任一种或一种以上的组合。
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