阅读说明：本技术 一种低氧环境下动态测量氧代谢率的方法 (The method of oxygen metabolism rate is dynamically measured under a kind of low-oxygen environment ) 是由 高家红 张垚煜 于 2019-07-11 设计创作，主要内容包括：本发明涉及磁共振成像和生理参数检测领域,具体涉及一种低氧环境下动态测量氧代谢率的方法：一方面,结合动脉和静脉血中dHb对于BOLD信号的影响建立了新的模型；另一方面,建立了低氧环境下的M与正常氧环境下的M之间的关系。本发明提出的方法能够解决现有的动态测量CMRO<Sub>2</Sub>的模型不能适用于低氧环境的问题,为低氧环境下研究脑功能和脑疾病提供了新的工具。(The present invention relates to magnetic resonance imagings and physio-parameter detection field, and in particular to the method for oxygen metabolism rate is dynamically measured under a kind of low-oxygen environment: on the one hand, the influence in conjunction with dHb in artery and venous blood for BOLD signal establishes new model；On the other hand, the relationship between the M under the M and normal oxygen conditions under low-oxygen environment is established.Method proposed by the present invention is able to solve existing dynamic measurement CMRO 2 Model the problem of being not applied for low-oxygen environment, to study brain function under low-oxygen environment and cerebral disease provides new tool.)

1. dynamically measuring the method for oxygen metabolism rate under a kind of low-oxygen environment, which comprises the following steps:

(1) it obtains and corrects parameter M under user's normal oxygen conditions^norm；

(2) arterial oxygen saturation under the normal oxygen of user, quiescent condition is obtainedSvo2And brain Blood volume signals

(3) arterial oxygen saturation under user's hypoxemia, quiescent condition is obtainedSvo2Brain blood body Product signalBrain Blood oxygen level dependence signalThe variation percentage of signal of brain's blood streamWith it is low Oxygen completes arterial oxygen saturation under particular task stateBrain blood volume signals CBV^hypo, brain Blood oxygen level dependence letter Number BOLD^hypo, signal of brain's blood stream variation percentage CBF^hypo；

(4) it is calculated based on above-mentioned acquired each signal value and corrects parameter M under low-oxygen environment^hypo；

(5) based on M obtained in each signal value and step (3) acquired under above-mentioned low-oxygen environment^hypoCalculating should under low-oxygen environment Cerebral metabolism rate of oxygen of the user when completing particular task relative to quiescent condition under variation percentage δ CMRO2^hypo。

2. method as described in claim 1, which is characterized in that M in step (1)^normIn user sucking high-carbon acid gas or It is measured under conditions of hyperoxia gas or high carbon acid, high-oxygen gas mixture body.

3. method as described in claim 1, which is characterized in that the brain Blood oxygen level dependence signal, signal of brain's blood stream and brain Blood volume signals are obtained by the measurement of MRI means.

4. method as described in claim 1, which is characterized in that the Svo2 is measured by MRI means or elder generation Test knowledge acquisition.

5. method as claimed in claim 4, which is characterized in that according to priori knowledge,For 0.6-0.7,For 0.5- 0.6。

6. method as described in claim 1, which is characterized in that the arterial oxygen saturation is existed by instrument for detecting sphygmus and blood oxygen saturation The measurement of user's finger end obtains.

7. method as described in claim 1, which is characterized in that the low-oxygen environment Digital arteries blood oxygen level is lower than 90%.

8. method as described in claim 1, which is characterized in that step (4) is calculated by the following formula M^hypo:

Wherein, α is arterial blood fraction, α=0.3；β is the variable quantity of an effective lateral relaxation time of characterizationWith blood The constant of the relationship of susceptibility difference, β=1.5 between liquid and tissue.

9. method as described in claim 1, which is characterized in that step (5) is calculated by the following formula δ CMRO2^hypo:

,

Wherein, δ BOLD^hypoFor the variation percentage of brain Blood oxygen level dependence signal, δCBF^hypoFor the variation percentage of signal of brain's blood stream,δCBV^hypoFor brain blood volume letter Number variation percentage,

Technical field

The present invention relates to magnetic resonance imagings and physio-parameter detection field, and in particular to dynamically measures under a kind of low-oxygen environment The method of oxygen metabolism rate.

Background technique

The oxygen metabolism rate (CMRO2) of brain characterizes oxygen consumption of the brain tissue of unit volume within the unit time, is The important physiological parameter of brain.CMRO2 has been demonstrated and a variety of cerebral diseases (such as headstroke, brain tumor and alzheimer's disease) It is closely related.Dynamic measurement CMRO2 helps to probe into working mechanism of the brain in the task of execution.

Based on magnetic resonance imaging (MRI) technology, Davis et al. proposition is utilized in the method for traditional dynamic measurement CMRO2 Model (hereinafter referred to as " Davis model ")¹.Davis model hypothesis brain is under normal oxygen environment, in other words arterial blood Oxygen saturation (Ya) be similar to 1, the concentration of deoxyhemoglobin (dHb) is similar to 0.Brain blood volume is obtained by MRI technique (CBV) signal, brain blood flow (CBF) signal, Blood oxygen level dependence (BOLD) signal and correction parameter M, establish equation Extrapolate CMRO2 signal¹。

However, brain is in low-oxygen environment under plateau or specific cerebral disease environment, Ya is lower than 0.9 in other words.This When, Davis model is no longer applicable in, and reason has two.First, under the hypothesis of Davis model Ya~1, BOLD signal main source The concentration of dHb in venous blood changes¹, that is, have ignored the contribution of arterial blood.And under low-oxygen environment, in artery and venous blood DHb all BOLD signal is contributed.Second, M is to utilize sucking high-carbon acid gas under normal oxygen conditions in Davis model CBF rises when body, but the constant physiological phenomenon measurement of CMRO2 obtains¹.And under low-oxygen environment, which is broken, low M under oxygen environment can not be measured according to original method.

Summary of the invention

In order to solve the problems, such as that Davis model is not suitable for low-oxygen environment, the present invention is based on MRI technique, propose that one kind exists The method of CMRO2 is dynamically measured under low-oxygen environment.On the one hand, in conjunction with influence of the dHb for BOLD signal in artery and venous blood Establish new model；On the other hand, the relationship between the M under the M and normal oxygen conditions under low-oxygen environment is established.The present invention The method of proposition is able to solve the problem of Davis model is not applied for low-oxygen environment, be low-oxygen environment under research brain function and Cerebral disease provides new tool.

A kind of method dynamically measuring CMRO2 under low-oxygen environment proposed by the present invention, including following model scheme:

In following scheme, defines subscript 0, a and v and respectively represent quiescent condition, artery and vein；Subscript norm and Hypo respectively represents normal oxygen and hypoxia；Alphabetical δ representation signal is under task status relative to the percentage under quiescent condition Than, such as δ Β OLD=BOLD/BOLD₀-1。

Boxerman et al. proposes the variable quantity of effective lateral relaxation time,With the oxygen saturation (Y) in blood And the relationship between CBV is²:

Wherein A is the constant determined by field strength and sample properties；β is a characterizationBetween blood and tissue The constant of the relationship of susceptibility difference, β=1.5.

Davis et al. propose δ BOLD andBetween relationship be¹:

Wherein TE is the echo time.

In conjunction with formula (1) and (2), can obtain:

Blood is divided into arterial blood and venous blood (blood of capillary is prorated in plasma viscosity)³, Y

It can indicate are as follows:

Y=α Y_a+(1-α)Y_v, (4)

Wherein α is arterial blood fraction, α=0.3.

According to Fick's law, CMRO2, CBF and artery and vein oxygen content (C_aO₂And C_vO₂) between relationship may be expressed as:

CMRO₂=CBF (C_aO₂-C_vO₂). (5)

Wherein C_aO₂And C_vO₂It can further indicate that are as follows:

WhereinRepresent the oxygen carrying capacity of hemoglobin (Hb)；[Hb] represents the concentration of Hb；Y_aAnd Y_vIt respectively represents dynamic and static The oxygen saturation of arteries and veins blood；P_aO₂And P_vO₂Respectively represent the partial pressure of oxygen of plasma viscosity；ε represents the solubility of oxygen in blood. In formula (6) and (7), first item represents the oxygen in conjunction with Hb on the right side of equation, and Section 2 represents the oxygen of dissolution in blood Gas, the latter < < the former, therefore can be ignored.

In conjunction with formula (5), (6) and (7), can obtain:

In conjunction with formula (3), (4) and (8), can derive:

Formula (1)-(9) are suitable for normal oxygen and low-oxygen environment.

Under normal oxygen conditions, by Y_a=Y_{A, 0}=1 brings formula (9) into, can obtain

Wherein δ CBV^norm、δCBF^normWith δ BOLD^normIt can be obtained by MRI means measurement, M^normSucking can be passed through The mode measurement of high-carbon acid gas, hyperoxia gas or high carbon acid, high-oxygen gas mixture body obtains¹。

M under low-oxygen environment^hypoCan not measure to obtain by way of sucking high carbon acid, but can by formula (3) and (4) it connects:

Wherein It can be surveyed by MRI means It measures,It can be obtained by instrument for detecting sphygmus and blood oxygen saturation in the measurement of finger end.

Acquire M^hypoIt afterwards, can be by M^hypoBring formula (9) into, a kind of method for obtaining dynamically measuring CMRO2 under hypoxemia are as follows:

A kind of method dynamically measuring CMRO2 under low-oxygen environment proposed by the present invention, including following operating procedure (see Fig. 1):

(1) mode that user sucks high-carbon acid gas, hyperoxia gas or high carbon acid, high-oxygen gas mixture body measures M^norm。

(2) arterial oxygen saturation under the normal oxygen of user, quiescent condition is obtainedSvo2With brain blood volume signals

(3) arterial oxygen saturation under user's hypoxemia, quiescent condition is obtainedSvo2 Brain blood volume signalsBrain Blood oxygen level dependence signalThe variation percentage of signal of brain's blood streamWith arterial oxygen saturation under hypoxemia, completion particular task stateBrain blood volume signals CBV^hypo, brain blood Oxygen level relies on signal BOLD^hypo, signal of brain's blood stream variation percentage CBF^hypo；

(4) it is calculated based on above-mentioned acquired each signal value and corrects parameter M under low-oxygen environment^hypo；

(5) based on M obtained in each signal value and step (3) acquired under above-mentioned low-oxygen environment^hypoCalculate hypoxemia ring Variation percentage δ under cerebral metabolism rate of oxygen of the user when completing particular task is relative to quiescent condition under border CMRO2^hypo。

Further, high-carbon acid gas, the mode of hyperoxia gas or high carbon acid, high-oxygen gas mixture body are sucked in the above method Measure M^normMethod referring to Davis et al.¹, Chiarelli et al.⁴Or Gauthier et al.⁵Method.

Further, above method medium sized vein blood oxygen saturation is measured by MRI means or priori knowledge obtains (being shown in Table 1)；Arterial oxygen saturation is obtained by instrument for detecting sphygmus and blood oxygen saturation in the measurement of finger end.

Further, above method deutocerebral region δ BOLD, δ CBF and δ CBV signal are obtained by MRI means measurement.

Further, high-carbon acid gas described in step (1) is by 5%CO₂, 21%O₂And 74%N₂Composition.

Further, low-oxygen environment Digital arteries blood oxygen level described in step (2) is lower than 90%.

Detailed description of the invention

Fig. 1 is the flow chart of the invention that CMRO2 is measured under low-oxygen environment.

Fig. 2 is that CMRO2 result of variations caused by visual task compares under normal oxygen conditions and low-oxygen environment.

Specific embodiment

In the following description, a large amount of concrete details are given in order to which those skilled in the art are more thorough to the present invention The understanding at bottom.It is to be understood that disclosed herein is only a kind of representative preferred embodiment.Obviously, the present invention is simultaneously It is not limited to any specific structure described herein, function, Apparatus and method for, it is possible to have other embodiments, or It is the combination of other embodiments.Element number described in the present invention it is also contemplated that be multiple, unless explicitly limited for Odd number.In addition, to avoid other examples from obscuring with the present invention, for some technical characteristics well known in the art and carefully Section is not described.