JP5877000B2 - MRI equipment - Google Patents

Description

  The present invention relates to a quantification method capable of analyzing the amount of plasma leaked into an extravascular space (a liquid in which blood cells are excluded from blood components), the amount of plasma in the surrounding tissue itself, the amount of blood, and the like from contrast-enhanced MR images.

  Blood volume (BV) and blood flow (BF) information in the tumor and its surroundings are important for prior evaluation and differential diagnosis of surgical operations and radiation therapy for tumors such as meningiomas. Currently, in order to obtain these blood perfusion information, diagnostic imaging method using MR imaging device by administration of gadolinium-containing contrast agent, diagnostic imaging method using CT imaging device by administration of iodine-containing contrast agent, An image diagnostic method using a PET device by administration of a tracer (a radiopharmaceutical prepared by a cyclotron) is used.

  In these diagnoses, a predetermined cross-section including a lesion is repeatedly imaged at regular time intervals, and a series of image data obtained by this is analyzed for each pixel to first obtain a BV and then create a BF map A perfusion inspection method is generally performed (Patent Document 1).

JP 2006-130141 A

  However, the perfusion examination method using the MR or CT apparatus described above has a drawback that BV and BF can be obtained only in normal brain tissue. In other words, only in normal brain tissue where the blood-brain barrier (BBB) is not destroyed, there is no leakage of contrast medium (dissolved in plasma) into the extravascular space, and relatively accurate BV and BF can be obtained. However, when the BBB is destroyed (such as a brain tumor or stroke), the contrast agent leaks into the extravascular space, and BV and BF are underestimated. On the other hand, since imaging using a PET device uses a relatively large tracer (human red blood cells bound to carbon monoxide labeled with a radioisotope), bleeding (red blood cells) even if the BBB is destroyed. As long as the tracer does not leak out of the blood vessel), relatively accurate BV and BF evaluation is possible without the tracer leaking into the extravascular space. However, because radiopharmaceuticals are handled, it is necessary to strictly manage the exposure doses of subjects and surgeons, and PET devices are not widely used compared to MR imaging devices, and the facilities that can be used are limited. End up.

  It is an object of the present invention to provide an apparatus and a method capable of easily and relatively accurately obtaining blood perfusion information by a dynamic MR contrast agent test that is not based on a conventional perfusion test method.

  The above object is achieved by the invention described below.

(A) a magnetic field generator that applies a magnetic field to the imaging space where the subject is located;
A pulse transmitter for irradiating the imaging space with a high-frequency pulse;
A receiver for receiving an echo signal obtained from the subject by irradiation of a high-frequency pulse by the pulse transmitter;
A blood flow information calculation unit for calculating blood flow information of the subject using the echo signal;
An image data generator for reconstructing an image based on the blood flow information;
A display device for displaying the image reconstructed by the image data generation unit;
Have
The pulse transmitter emits a radio frequency pulse before and after injection of the contrast agent, and the receiver obtains a first echo signal and a second echo signal before and after the injection of the contrast agent, The blood flow information calculation unit calculates the change ΔR2 * (t of the lateral relaxation rate at the elapsed time t after the injection of the contrast agent, which is obtained from the signal intensities of the first echo signal and the second echo signal before and after the injection of the contrast agent. ) Based on the MR image (MRI) device configured to calculate the blood volume (BV) in the blood vessel and the leakage amount (LV) to the outside of the blood vessel as the blood flow information.

(B) the MRI apparatus of the present invention;
A chemical injection device for injecting a contrast medium into the subject to obtain an echo signal from the subject by the MRI device;
With MRI system.

(C) A magnetic field generator for applying a magnetic field to the imaging space where the subject is located, a pulse transmitter for irradiating the imaging space with a high frequency pulse, and an echo signal obtained from the subject by irradiation of the high frequency pulse by the pulse transmitter A blood flow information calculation unit that calculates blood flow information of the subject using the echo signal, an image data generation unit that reconstructs an image based on the blood flow information, and the image data A display device for displaying the image reconstructed by the generation unit, and an operating method of the MRI apparatus,
The pulse transmitter irradiates a radio frequency pulse before and after injection of a contrast agent;
The receiver obtains a first echo signal and a second echo signal for each before and after injection of a contrast agent;
The blood flow information calculation unit changes the lateral relaxation rate ΔR2 * (elapsed time t after contrast medium injection obtained from the signal intensities of the first echo signal and the second echo signal before and after the contrast medium injection. t) based on the blood flow information, calculating the blood volume in the blood vessel and the leakage amount outside the blood vessel,
A method of operating an MRI apparatus, including:

(D) A magnetic field generator that applies a magnetic field to the imaging space where the subject is located, a pulse transmitter that irradiates the imaging space with a high-frequency pulse, and an echo signal obtained from the subject by irradiation of the high-frequency pulse by the pulse transmitter A blood flow information calculation unit that calculates blood flow information of the subject using the echo signal, an image data generation unit that reconstructs an image based on the blood flow information, and the image data A display device for displaying the image reconstructed by the generation unit, and a computer program for an MRI apparatus,
Irradiating the pulse transmitter with a radio frequency pulse before and after injection of a contrast agent;
Causing the receiver to acquire a first echo signal and a second echo signal for each before and after injection of a contrast agent;
Changes in lateral relaxation rate ΔR2 * (elapsed time t after contrast medium injection obtained from the signal strengths of the first echo signal and the second echo signal before and after injection of the contrast medium in the blood flow information calculation unit. t), based on the blood flow information, calculating the blood volume in the blood vessel (BV) and the leakage amount outside the blood vessel (LV),
A computer program for an MRI apparatus, including:

  (E) An information storage medium storing the computer program of the present invention.

  A BV map image and an LV map image having a very high correlation with an image obtained by a PET examination can be obtained by a dynamic contrast agent examination which is not a conventional perfusion examination method using an MRI apparatus. In addition, since these map images can be created without using the PET examination, it is possible to minimize the physical burden on the subject, such as exposure due to radiation irradiation.

1 is a schematic diagram of an MRI system according to an embodiment of the present invention. It is a perspective view which shows the injection | pouring head of the MRI system shown in FIG. 1 with the syringe with which it is mounted | worn. It is a functional block diagram of the MRI system shown in FIG. Assuming that the BV value measured with the PET device is the gold standard (accurate reference value among all), the BV value measured with the MR device using the method of the present invention and the conventional perfusion test method are used. 6 is a graph comparing the BV value measured by the MR apparatus.

  Referring to FIG. 1, an MRI system 1000 having an MRI apparatus 300 and a chemical liquid injector 100 according to an embodiment of the present invention is shown. The MRI apparatus 300 controls the operation of the imaging unit 301 that executes the imaging operation and the imaging unit 301, and reconstructs image data based on the magnetic resonance signal obtained from the imaging unit 301 and displays it as a tomographic image. An imaging control unit 302.

  The chemical solution injection device 100 includes an injection head 110 and an injection control unit 101 electrically connected to the injection head 110 by a cable (not shown). Injection control unit 101 has a main operation panel, a touch panel, and the like. As shown in FIG. 2, the injection head 110 can detachably mount two syringes 200C and 200P each having a cylinder 221 and a piston 222, respectively.

  Each of the syringes 200C and 200P is filled with a chemical solution to be injected into the subject. An extension tube 230 having a distal end branched into two and an injection needle (not shown) connected to the distal end is connected to the nozzle portion 221b at the distal end of the syringes 200C and 200P, and the injection needle is punctured into the blood vessel of the subject. By doing this, it will be in the state which can inject | pour into the test subject the chemical | medical solution with which syringe 200C, 200P was filled. The chemical solutions filled in the syringes 200C and 200P may both be the same or different from each other. Normally, the syringe 200C is filled with an MRI contrast agent (gadolinium preparation), and the other syringe 200P is filled with physiological saline.

  A syringe receiver 120 for holding two syringes 200 </ b> C and 200 </ b> P is provided at the distal end portion of the injection head 110. The syringe receiver 120 includes two recesses 120a that receive the cylinders 221 of the syringes 200C and 200P, and two cylinder holding members 121 and 122 that hold the flanges at the ends of the cylinders 221 received in the recesses 120a.

  In order to advance and retract the pistons 222 of the syringes 200C and 200P held by the injection head 110, two piston drive mechanisms 130 that are driven independently of each other are provided corresponding to the syringes 200C and 200P. . The piston drive mechanism 130 has a drive motor (not shown) and a motion conversion mechanism (not shown) that converts the rotational output of the drive motor into a linear motion. As such a piston drive mechanism 130, since a well-known mechanism generally used in a chemical liquid injector can be used, detailed description thereof is omitted here.

  As a mechanism for holding the syringes 200C and 200P of the injection head 110 to the head main body 113 and the piston drive mechanism 130, a known mechanism generally used for this type of injection device can be adopted.

  FIG. 3 shows a functional block diagram of the MRI system shown in FIG.

  As shown in FIG. 3, the injection control unit 101 of the chemical injection device 100 is an interface (I / F) between the control unit 141, the input device 142, the display device 143, the injection condition calculation unit 146, and the MRI apparatus 300. 147.

  The input device 142 corresponds to the above-described main operation panel and touch panel, and receives various settings of the chemical liquid injector 100 and data input for determining chemical liquid injection conditions. The display device 143 corresponds to the touch panel described above, and displays a setting screen, a data input screen, a screen representing an operation state, and the like of the chemical liquid injector 100. Thus, in this embodiment, the touch panel has both the function of the input device 142 and the function of the display device 143. The injection condition calculation unit 146 calculates the injection condition of the chemical based on the data input from the input device 142 or the like. The control unit 141 controls the operation of the piston drive mechanism 130 of the injection head 110 so that the chemical solution is injected according to the injection condition obtained by the injection condition calculation unit 146, or causes the display device 143 to display a predetermined image. The overall operation of the chemical liquid injector 100 is controlled.

  The control unit 141 and the injection condition calculation unit 146 can be configured by a computer unit. The computer unit includes a CPU, a ROM, a RAM, and the like, and fulfills the functions of the control unit 141 and the injection condition calculation unit 146 when the CPU executes various processes according to a computer program installed in the RAM, for example.

  On the other hand, the MRI apparatus 300 includes the imaging unit 301 and the imaging control unit 302 as described above.

  The imaging unit 301 is emitted from a subject by a magnetic field generator that applies a predetermined magnetic field to an imaging space where the subject is located, a pulse transmitter 330 that irradiates the space with a high-frequency pulse, and irradiation of a high-frequency pulse by the pulse transmitter 330. And a receiver 340 for receiving a nuclear magnetic resonance signal (echo signal).

  The magnetic field generator includes a static magnetic field generator 310 that applies a static magnetic field to the imaging space, and a gradient magnetic field generator 320 that applies a gradient magnetic field to the static magnetic field applied by the static magnetic field generator 310. As the static magnetic field generator 310, a permanent magnet or a superconducting magnet can be used. The magnetic field intensity generated by the static magnetic field generator 310 may be the same as the magnetic field intensity in a normal MRI apparatus used clinically, and can be, for example, about 0.2 to 3.0 T (Tesla). The gradient magnetic field generator 320 can be, for example, a gradient magnetic field coil that generates a gradient magnetic field when electric power is supplied.

  The imaging control unit 302 includes an interface (I / F) 400 between the control unit 350, the blood flow information calculation unit 360, the image data generation unit 370, the input device 380, the display device 390, and the drug solution injector 100. ing.

  The blood flow information calculation unit 360 is based on the nuclear magnetic resonance signal received by the receiver 340, and blood flow information such as blood flow volume and blood leakage from the blood vessel to surrounding tissues at the site irradiated with the high frequency pulse of the subject. Is calculated. The image data generation unit 370 reconstructs image data based on the nuclear magnetic resonance signal received by the receiver 340 and the blood flow information data obtained by the blood flow information calculation unit 360. The input device 380 accepts input of data related to various settings and imaging conditions of the MRI apparatus 300. The display device 390 displays a setting screen of the MRI apparatus 300, various information regarding imaging, image data reconstructed by the image data generation unit 370, and the like. The control unit 350 controls the operation of the static magnetic field generator 310, the gradient magnetic field generator 320, and the pulse transmitter 330 based on the data input from the input device 380, and the display device 390 based on the image data reconstructed with the image data. The overall operation of the MRI apparatus 300 such as display control is controlled.

  The blood flow information calculation unit 360, the image data generation unit 370, and the control unit 350 can be configured by a computer unit. The computer unit includes a CPU, a ROM, a RAM, and the like. For example, the blood flow information calculation unit 360, the image data generation unit 370, and the control unit 350 are executed by the CPU according to a computer program installed in the RAM. Fulfills the function.

In the present invention, the MRI apparatus 300 is a double echo SPGR (Spoiled) that is a GRE (Gradient Echo) sequence for collecting double echoes (first echo and second echo) by one excitation.
The imaging operation by the GRASS) pulse sequence method is executed before and after the injection of the contrast agent. The blood flow information calculation unit 360 uses the blood volume (BV) and blood vessels in the blood vessel lumen as blood flow information based on the signals acquired from the first echo and the second echo before and after the injection of the contrast agent. Calculate the amount of blood leakage (LV).

  Hereinafter, calculation of blood flow information by the blood flow information calculation unit 360 will be described by taking a case of diagnosing a brain tumor as an example.

  It is known that the following relational expression holds between the scan parameter based on the SPGR pulse sequence method and the signal intensity S.

式（１）において、
ｋ＝スケーリングファクタ
ｐ＝プロトン密度
TR＝繰り返し時間
TE＝エコー時間
T1＝組織のT1値（縦緩和時間）
T2*＝組織のT2*値（見かけの横緩和時間）
α＝フリップ角
を意味する。

In equation (1),
k = scaling factor p = proton density
TR = repetition time
TE = Echo time
T1 = T1 value of the tissue (longitudinal relaxation time)
T2 * = T2 * value of the tissue (apparent lateral relaxation time)
α = Flip angle.

  Consider a case where MRI (or echo signal) is acquired before and after injection of a contrast agent using one echo (single echo). T1 value of the tissue before contrast agent injection (T = 0) is T1 (0), and T1 value of the tissue after time t (actual unit is msec) from the start of contrast agent injection is T1 (t) Then, the T2 * value of the tissue also changes from T2 * (0) to T2 * (t) before and after the injection of the contrast agent. On the other hand, in Expression (1), TR, TE, and α are fixed values set by the MRI apparatus 300, and therefore do not change before and after the injection of the contrast agent. Moreover, k and p are values peculiar to the tissue, and these also do not change before and after the injection of the contrast agent.

  Therefore, if the signal intensity S is changed from S (0) to S (t) by the injection of the contrast agent, it can be said that this change in signal intensity S is due to T1 and T2 *. However, it reflects T1 intravascular space, BBB permeability, and extravascular space information, and it is necessary to obtain only intravascular information in order to determine the true tumor blood volume.

  In the case of single echo (that is, the number of acquisitions of the echo signal with the repetition time TR is 1), S (0) and S (t) are

と表される。式（２）および（３）から、造影剤の注入前後でのエコー信号強度の変化率S(t)/S(0) が計算できる。

It is expressed. From equations (2) and (3), the rate of change S (t) / S (0) of the echo signal intensity before and after the injection of the contrast agent can be calculated.

  Now, consider the following formulas (4) to (6),

これら式（４）〜（６）を、式（２）および（３）から得られるエコー信号強度の変化率 S(T)/S(0) に代入すると、

Substituting these equations (4) to (6) into the rate of change S (T) / S (0) of the echo signal intensity obtained from equations (2) and (3),

となる。

It becomes.

  Since the lateral relaxation rate R2 * = 1 / T2 *, substituting this into equation (7) and transforming the resulting equation,

となる。

It becomes.

The change in R2 * before and after the injection of the contrast agent after time t has elapsed since the start of the injection of the contrast agent is
ΔR2 * (t) = R2 * (t) −R2 * (0)
By substituting this into equation (8),

が得られる。

Is obtained.

  Here, it is assumed that the injected contrast agent does not leak out of the blood vessel. It is considered that the longitudinal relaxation time (T1) of the tissue changes only when the contrast medium leaks into the third space or stroma existing outside the blood vessel. Therefore, if the contrast agent does not leak out of the blood vessel, no change should be observed in T1 (t), and T1 (t) = T1 (0). In this case, since B = C = 1 from the equations (5) and (6), the second term and the third term on the right side of the equation (9) are zero, and therefore the equation (9) is

となる。この式（１０）は、ΔR2*情報が、造影剤の注入前後でのエコー信号強度の変化率S(t)/S(0) のみで決まることを意味する。

It becomes. This equation (10) means that ΔR2 * information is determined only by the rate of change S (t) / S (0) of the echo signal intensity before and after the injection of the contrast agent.

  Also, from equation (10), the rate of change of the echo signal intensity is

と表すことができる。エコー時間TEが一定であることを考慮すれば、式（１１）より、エコー信号強度の変化率S(t)/S(0)は、ΔR2*(t) のみに依存することがわかる。この場合、造影剤は血管外へ漏出していないので、エコー信号強度S(t)に変化を与える物理的な要因、あるいは造影効果を与える要因があるとすれば、それは血管内の造影剤しかないと考えることができる。つまり、ΔR2*(t) は、血管内の造影剤が関与したパラメータであるといえる。

It can be expressed as. Considering that the echo time TE is constant, it can be seen from the equation (11) that the rate of change S (t) / S (0) of the echo signal intensity depends only on ΔR2 * (t). In this case, since the contrast agent does not leak out of the blood vessel, if there is a physical factor that changes the echo signal intensity S (t) or a factor that gives a contrast effect, it is only the contrast agent in the blood vessel. I can think of it not. That is, ΔR2 * (t) can be said to be a parameter related to the contrast agent in the blood vessel.

  Considering that S (0) is also a constant value, ΔR2 * (t) is the susceptibility in the blood vessel (which is closely related to the size of the space where the contrast medium in the blood vessel spreads), that is, the blood vessel. It can be said that information related to the inner space is given.

  Next, consider a case where a part of the contrast medium leaks out of the blood vessel.

  Equation (9)

と変形する。ΔR2*(t) は、上述したとおり血管内空間の情報を扱っているといえるので、式（１２）の右辺第１項は血管内空間に関する情報を扱っていると考えられる。従って、残りの第２項および第３項が全体として、BBBおよび血管外空間の両方に関する情報、すなわち血管外への漏出に関する情報を扱っていると考えられる。

And deformed. Since it can be said that ΔR2 * (t) handles information on the intravascular space as described above, the first term on the right side of the equation (12) is considered to handle information on the intravascular space. Therefore, it is considered that the remaining second and third terms as a whole handle information relating to both the BBB and the extravascular space, that is, information relating to leakage outside the blood vessel.

  Here, the echo signal intensity S (TE1) when the echo time is extremely short like the first echo is considered.

  In this case, assuming that TE → 0, equation (12) is

となる。式（１３）は、ΔR2*(t) の項が存在しないので、第１エコーから得られるエコー信号の変化率は S(t)/S(0) は、血管内空間よりも、主にBBBおよび血管外空間に関する情報、すなわち血管外への漏出に関する情報を反映していることが分かる。

It becomes. In equation (13), since the term ΔR2 * (t) does not exist, the rate of change of the echo signal obtained from the first echo is S (t) / S (0) is mainly BBB rather than the intravascular space. It can also be seen that information relating to the extravascular space, that is, information relating to leakage outside the blood vessel is reflected.

  Next, consider the echo signal intensity S (TE1) due to the first echo (echo time TE = 5 msec) and the echo signal intensity S (TE2) due to the second echo (echo time TE = 22 msec).

  First, let us consider the determination of ΔR2 * (t) from echo signal intensities S (TE1) and S (TE2) before and after injection of contrast agent. Assume that the baseline signal intensity S0 (TE1) at the first echo time TE1 and the baseline signal intensity S0 (TE2) at the second echo time TE2 are acquired before the injection of the contrast agent (t = 0 msec). S0 (TE1) and S0 (TE2) are obtained from equation (1)

で表すことができる。

Can be expressed as

  Next, it is assumed that the signal intensity St (TE1) at the first echo time TE1 and the signal intensity St (TE2) at the second echo time TE2 are acquired after the elapse of time t (msec) from the start of contrast agent injection. St (TE1) and St (TE2) are obtained from equation (1)

で表すことができる。

Can be expressed as

  Here, the following signal ratio r is considered.

式（１４）〜（１７）を式（１８）に代入して簡単にまとめると、

Substituting the formulas (14) to (17) into the formula (18) and summing them up briefly,

となる。
1/T2*(t)−1/T2*(0) =Δ1/T2*(t) =ΔR2*(t)、
ΔR2*(t) = R2*(t)−R2*(0)、
であるので、式（１９）は、

It becomes.
1 / T2 * (t) −1 / T2 * (0) = Δ1 / T2 * (t) = ΔR2 * (t),
ΔR2 * (t) = R2 * (t) −R2 * (0),
Therefore, equation (19) is

となる。式（２０）より、信号比rは、T1 に関する情報を全く含まず、また、 (TE2-TE1)が固定値であることを考慮すれば、R2*(0) とR2*(t) のみに依存していることがわかる。

It becomes. From equation (20), the signal ratio r does not contain any information about T1, and considering that (TE2-TE1) is a fixed value, only R2 * (0) and R2 * (t) It turns out that it depends.

In equation (20), taking the logarithm of both sides,

となる。信号比ｒは式（１８）で定義されることから、これを式（２１）に代入すると、

It becomes. Since the signal ratio r is defined by the equation (18), if this is substituted into the equation (21),

となる。

It becomes.

From equation (22), signal intensities S0 (TE1) and S0 (TE2) that can be obtained from the two echo times TE1 and TE2 respectively before the contrast agent injection, and two echo times TE1 and TE2 that can be obtained after the contrast agent injection, respectively. Signal strength
From St (TE1) and St (TE2), it can be seen that ΔR2 * (t) when the contrast medium leaks out of the blood vessel can be obtained.

  As described above, since ΔR2 * (t) reflects information on the intravascular space, the capacity of the intravascular space can be obtained by integrating ΔR2 * (t). It can be considered that the volume of the intravascular space is theoretically the same as the amount of blood flowing therethrough. Therefore, if the blood volume is BV (Blood Volume),

で表される。なお、脳の血液量について考える場合は、BVの代わりに脳血液量CBV（Cerebral Blood Volume）を用いる。

It is represented by When considering the blood volume in the brain, the brain blood volume CBV (Cerebral Blood Volume) is used instead of BV.

  In equation (23), the integration range is ideally 0 (zero) → infinity, but is actually the imaging time ts. Further, since Equation (23) reflects only the information on the intravascular space, it can be physically interpreted that the dynamic T1 effect (leakage to the outside of the blood vessel) is corrected. If ΔR2 * (t) in equation (22) is expressed as ΔR2 * (t) (T1c), equation (23) becomes

と表すことができる。

It can be expressed as.

On the other hand, the echo signal intensity S (TE2) acquired only from the second echo time TE2 includes all elements of the intravascular space, BBB permeability, and extravascular space (leakage). ΔR2 * (t) in this case can be expressed as ΔR2 * (t) (T1u) because the dynamic T1 effect (leakage outside the blood vessel) can be physically interpreted as being uncorrected. From the echo signal intensity S (TE1) acquired at the first echo time TE1, information on BBB permeability and extravascular space (leakage) is mainly obtained. In this case, ΔR2 * (t) is expressed as ΔR2 * (t) (1 ^st echo).

  Here, equation (12) is transformed

と表すと、ΔR2*(t)(T1u) およびΔR2*(t)(1^st echo) は、式（２５）においてD=S(t)/S(0)と置き換えて、

, ΔR2 * (t) (T1u) and ΔR2 * (t) (1 ^st echo) are replaced with D = S (t) / S (0) in equation (25),

と表すことができる。

It can be expressed as.

Note that ΔR2 * (t) (1 ^st echo) is mainly only for obtaining information on BBB permeability and extravascular space, and is not without any information on intravascular space, so ΔR2 * (t Note that) (T1c) is not simply determined by subtracting ΔR2 * (t) (1 ^st echo) from ΔR2 * (t) (T1u).

  The phrase “the contrast medium leaks from the inside of the blood vessel to the outside of the blood vessel” means that “the contrast medium concentration and the amount of the contrast medium in the blood vessel are decreased”. Expressing this in terms of MR signal strength, ΔR2 * (t) (T1u) when the contrast agent leaks out of the blood vessel and the contrast agent concentration in the blood vessel diminishes. It is lower than ΔR2 * (t) (T1c) in the absence. In other words, between the two

の関係が成り立つ。

The relationship holds.

  The reduced amount is considered to reflect the amount of contrast medium leaked out of the blood vessel. Therefore, if the amount leaked per unit time is Leak (t), Leak (t) is

で求めることができる。式（２９）において、ΔR2*(t)(T1c) およびΔR2*(t)(T1u) は、それぞれ式（２２）および式（２６）で与えられるとおりである。また、式（２６）においては、前述したように D=S(t)/S(0) であり、ＢおよびＣはそれぞれ式（５）および（６）で置き換えたとおりであるので、これらを式（２９）に代入すれば、Leak(t) は、

Can be obtained. In Expression (29), ΔR2 * (t) (T1c) and ΔR2 * (t) (T1u) are as given by Expression (22) and Expression (26), respectively. In the equation (26), as described above, D = S (t) / S (0), and B and C are respectively replaced by the equations (5) and (6). Substituting into equation (29), Leak (t) becomes

で表すこともできる。

It can also be expressed as

  Also, if the total amount leaked is LV, LV can be integrated with Leak (t) over time, so

で求めることができる。

Can be obtained.

  In the above, the leakage of the contrast agent was considered. However, since the contrast agent moves with the blood and reflects the blood flow, the above-described study on the contrast agent can be applied to the blood as it is, and therefore the expression (29 ) To (31) may be considered as expressions for blood.

  The calculation of blood flow information based on the echo signal emitted by the irradiation of the high frequency pulse has been described above. The blood flow information calculation unit 360 calculates the blood volume BV in the blood vessel and the blood leakage amount LV to the outside of the blood vessel using the equations (24) and (31), respectively.

  The blood flow information calculation unit 360 executes this processing for all the pixels, and the data of the blood volume BV in the blood vessel and the blood leakage amount LV obtained from all the pixels is obtained as the image data generation unit 370. Sent to.

  Next, the operation of the above-described MRI system will be described.

  Prior to the injection of the contrast agent by the drug solution injector 100, the MRI apparatus 300 performs an imaging operation according to the double echo SPGR pulse sequence method. In this imaging operation, the pulse transmitter 330 emits a high-frequency pulse, and the receiver 340 acquires an echo signal based on the first echo and the second echo. The imaging conditions can be, for example, that the first echo time TE1 is 5 msec, the second echo time TE2 is 22 msec, and the repetition time is 3000 msec.

  Next, injection of the contrast medium into the subject by the chemical solution injection device 100 is executed. When injecting the contrast agent, the extension tube extension tube 230 is connected to the tips of the syringes 200C and 200P in advance, and the injection needle at the tip of the extension tube 230 is punctured by the subject.

  The conditions for injecting the contrast agent by the chemical solution injection device 100 may be the same as those in the normal MRI examination. For example, the injection amount of the contrast agent is 0.2 ml per 1 kg of the body weight of the subject, and the injection speed is 1-2 ml / sec. Can do. The injection rate of the contrast agent may be constant or may be changed over time. Furthermore, only the contrast agent may be injected, or after the injection of the contrast agent, physiological saline may be injected and the contrast agent may be boosted with physiological saline, or the contrast agent may be diluted with physiological saline and injected. May be.

  The injection amount and the injection speed may be programmed in advance in the chemical solution injection device 100, or may be set each time by the operator. When a syringe with an ID tag is used, an injection condition is given to the ID tag as part of the contrast agent information, and this ID tag can be a tag reader that can be an accessory device of the drug solution injector 100. By reading out (not shown), the injection condition can be set in the chemical injection device 100.

  When a predetermined time elapses after the start of the injection of the contrast agent, the imaging operation according to the double echo SPGR pulse sequence method by the MRI apparatus 300 is executed again. The imaging conditions can be the same as the imaging conditions before the injection of the contrast agent, and echo signals based on the first echo and the second echo are acquired again by this imaging.

  A series of operations such as the imaging operation before contrast agent injection, the subsequent contrast agent injection operation, and the imaging operation again after a predetermined time has elapsed from the start of contrast agent injection are performed by one or more operators using the MRI apparatus 300 and the chemical solution. This can be performed by operating the injection device 100 individually, but can also be performed automatically if the MRI device 300 and the chemical solution injection device 100 are connected to each other so that signals can be transmitted and received.

  The echo signal acquired by the imaging operation before and after the injection of the contrast agent is sent from the receiver 340 to the blood flow information calculation unit 360. The blood flow information calculation unit 360 images the blood volume in the blood vessel and the blood leakage amount outside the blood vessel based on the above-described mathematical expressions using the sent echo signal and a part of the imaging conditions. Calculate for each pixel.

  All data calculated by the blood flow information calculation unit 360 is sent to the image data generation unit 370. The image data generation unit 370 reconstructs the data sent from the blood flow information calculation unit 360 to create a blood volume map and a leakage amount map, and the image obtained by the image data generation unit 370 is displayed on the display device 390. Is done.

  Fig. 4 shows the BV value measured by the MR device using the method of the present invention and the conventional perfusion, assuming that the BV value measured by the PET device is the gold standard (accurate standard value among all). The graph which compared with the BV value measured with MR apparatus using the inspection method is shown.

  From FIG. 4, it can be said that the CBV obtained by the MRI apparatus is closer to the CBV obtained by the PET apparatus by using the double echo method (according to the present invention) than the conventional perfusion examination method.

  As described above, according to the present embodiment, it is possible to obtain a CBV map image and an LV map image having a very high correlation with an image obtained by a PET examination even if an MRI apparatus is used. As a result, CBV maps and LV maps can be created, for example, prior to surgical procedures on tumor patients, to predict blood content of the tumor and leakage of blood to the surrounding area of the tumor. The surgeon can consider in advance appropriate treatments that minimize the risk based on the prediction of the blood content of the tumor and the amount of blood leakage to the surrounding site. In addition, if radiotherapy is scheduled, if the blood volume at the site to be treated is large, the success rate of radiotherapy will decrease and there are cases where alternative medicine must be performed. Can also be grasped before treatment. And the ability to create these maps without relying on a PET test is a huge advantage in that it eliminates the need to manage the subject's exposure and minimizes the physical burden on the subject. .

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea of the present invention.

  For example, in the above-described embodiment, the diagnosis of a brain tumor has been described as an example. However, the present invention is not limited to the brain, and can be any part of the whole body. Further, regarding the types of lesions to be diagnosed, various lesions such as infections, abscesses and hematomas can be diagnosed using the present invention as long as the lesions can cause abnormalities in blood flow. it can.

  The operation of the MRI apparatus 300 described above can be controlled according to a computer program, and the computer program for such an MRI apparatus 300 irradiates the pulse transmitter 330 with a high-frequency pulse before and after the injection of the contrast agent. And causing the receiver 340 to acquire the first echo signal and the second echo signal before and after the injection of the contrast agent, and causing the blood flow information calculation unit 360 to before and after the injection of the contrast agent. Based on the change ΔR2 * (t) in the lateral relaxation rate at the elapsed time t after the injection of the contrast agent, obtained from the signal intensities of the first echo signal and the second echo signal, blood volume in the blood vessel as blood flow information And calculating the amount of leakage to the outside of the blood vessel.

  The MRI apparatus 300 has an information storage medium such as a ROM or an HDD, and the computer program can be stored in the information storage medium. The computer program can be provided in a form stored in an information storage medium such as a CD-ROM, a DVD, or a USB memory, and can be installed updatable on the information storage medium included in the MRI apparatus 300.

DESCRIPTION OF SYMBOLS 100 Chemical liquid injection apparatus 101 Injection control unit 110 Injection head 130 Piston drive mechanism 141 Control part 142 Input device 143 Display device 146 Injection condition calculating part 147 Interface 200C, 200P Syringe 300 MRI apparatus 301 Imaging unit 302 Imaging control unit 310 Static magnetic field generator 330 Pulse Transmitter 340 Receiver 350 Control Unit 360 Blood Flow Information Calculation Unit 370 Image Data Generation Unit 380 Input Device 390 Display Device 400 Interface 1000 MRI System

Claims (8)

A magnetic field generator for applying a magnetic field to the imaging space where the subject is located;
A pulse transmitter for irradiating the imaging space with a high-frequency pulse;
A receiver for receiving an echo signal obtained from the subject by irradiation of a high-frequency pulse by the pulse transmitter;
A blood flow information calculation unit for calculating blood flow information of the subject using the echo signal;
An image data generator for reconstructing an image based on the blood flow information;
A display device for displaying the image reconstructed by the image data generation unit;
Have
The pulse transmitter emits a radio frequency pulse before and after injection of the contrast agent, and the receiver obtains a first echo signal and a second echo signal before and after the injection of the contrast agent, The blood flow information calculation unit obtains the change ΔR2 * (t of the lateral relaxation rate at the elapsed time t after the injection of the contrast agent, which is obtained from the signal intensities of the first echo signal and the second echo signal before and after the injection of the contrast agent. ) To calculate the blood volume in the blood vessel and the leakage amount to the outside of the blood vessel as the blood flow information. The blood flow information calculation unit is configured such that the echo time of the first echo signal is TE1, the echo time of the second echo signal is TE2, and the baseline signal intensity of the echo time TE1 before contrast agent injection is S0 (TE1), baseline signal intensity of the echo time TE2 before contrast medium injection S0 (TE2), the signal strength before Symbol echo time TE1 that put the elapsed time after injection of contrast agent t St (TE1), after contrast injection When the signal intensity of the echo time TE2 at the elapsed time t is St (TE2), ΔR2 * (t) (T1c) which is the change ΔR2 * (t) of the lateral relaxation rate reflecting only the information in the blood vessel With the following formula

The MRI apparatus according to claim 1, which is obtained by:
  The MRI according to claim 2, wherein the blood flow information calculation unit calculates the blood volume in the blood vessel by integrating the change ΔR2 * (t) (T1c) of the lateral relaxation rate obtained by the calculation formula. apparatus. When the blood flow information calculation unit sets ΔR2 * (t) (T1u) as the change ΔR2 * (t) in the lateral relaxation speed based on the echo signal acquired from only the second echo, Amount LV, the following formula

The MRI apparatus according to claim 3, which is calculated by: An MRI apparatus according to any one of claims 1 to 4,
A chemical injection device for injecting a contrast medium into the subject to obtain an echo signal from the subject by the MRI device;
With MRI system. A magnetic field generator that applies a magnetic field to an imaging space where the subject is located, a pulse transmitter that transmits a high-frequency pulse to the imaging space, and an echo signal obtained from the subject by the transmission of the high-frequency pulse by the pulse transmitter A receiver, a blood flow information calculation unit that calculates blood flow information of the subject using the echo signal, an image data generation unit that reconstructs an image based on the blood flow information, and the image data generation unit A display device for displaying the reconstructed image, and a method of operating an MRI apparatus,
The pulse transmitter emits high frequency pulses before and after injection of a contrast agent;
The receiver obtains a first echo signal and a second echo signal for each before and after injection of a contrast agent;
The blood flow information calculation unit changes the lateral relaxation rate ΔR2 * (elapsed time t after contrast medium injection obtained from the signal intensities of the first echo signal and the second echo signal before and after the contrast medium injection. t) based on the blood flow information, calculating the blood volume in the blood vessel and the leakage amount outside the blood vessel,
A method of operating an MRI apparatus, including: A magnetic field generator for applying a magnetic field to an imaging space where the subject is located, a pulse transmitter for irradiating the imaging space with a high frequency pulse, and an echo signal obtained from the subject by irradiation of the high frequency pulse by the pulse transmitter A receiver, a blood flow information calculation unit that calculates blood flow information of the subject using the echo signal, an image data generation unit that reconstructs an image based on the blood flow information, and the image data generation unit A display device for displaying the reconstructed image; and a computer program for an MRI apparatus comprising:
Irradiating the pulse transmitter with a radio frequency pulse before and after injection of a contrast agent;
Causing the receiver to acquire a first echo signal and a second echo signal for each before and after injection of a contrast agent;
Changes in lateral relaxation rate ΔR2 * (elapsed time t after contrast medium injection obtained from the signal strengths of the first echo signal and the second echo signal before and after injection of the contrast medium in the blood flow information calculation unit. t) based on the blood flow information, calculating the blood volume in the blood vessel and the leakage amount outside the blood vessel,
A computer program for an MRI apparatus, including:   An information storage medium in which the computer program according to claim 7 is stored.

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