JP2016131836A - Blood flow profile measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for precisely measuring a blood flow profile of a blood vessel on the basis of data acquired by 3D cine PC MR, and to provide a blood flow rate measuring device that executes the method.SOLUTION: A blood flow profile measuring method includes: a step (1) of constructing a blood vessel image that visualizes a three-dimensional vascular structure, from a magnitude image of 3D cine PC MR; a step (2) of measuring a blood flow vector at each coordinate in a blood vessel within the blood vessel image from a phase image of the 3D cine PC MR; a step (3) of measuring each AWSS or OSI at boundary coordinates of vascular walls in the blood vessel image, on the basis of the blood flow vector; a step (4) of extracting a measured cross-section only consisting of the boundary coordinates, at which each AWSS is a prescribed first threshold or more or each OSI is a prescribed second threshold or less, out of the vascular walls in the blood vessel image; and a step (5) of measuring a blood flow profile in the measured cross-section.SELECTED DRAWING: Figure 3

Description

  The present invention more accurately measures a blood flow profile of blood vessels (temporal profile of blood flow velocity in a blood vessel cross section) based on data acquired by a three-dimensional cine phase contrast magnetic resonance method (3D cine PC MR). Related to the method.

  Knowing the blood flow of an organ non-invasively has great clinical significance, such as ultrasonic Doppler method, measurement method using nuclear medicine tracer, cine phase contrast method by MRI (Magnetic Resonanse Imaging), etc. Has been attempted in various ways. The cine phase contrast magnetic resonance method is a phase contrast method in which imaging is performed by discriminating between flowing blood and stationary tissue using a phase shift of an MR signal induced by a flow rate in a bipolar gradient magnetic field. Is synchronized with the electrocardiogram and images are taken at each time point of the cardiac cycle. The method includes a two-dimensional cine phase contrast magnetic resonance method for measuring in a two-dimensional section and a three-dimensional cine phase contrast method for measuring a three-dimensional blood flow vector.

  Among these measuring methods, the ultrasonic Doppler method can measure the blood flow velocity, but has a problem that the objectivity is poor and the reproducibility is somewhat poor by an observer. In addition, the nuclear medicine method has problems such as the need for intravenous injection of a radioactive tracer and exposure of patients and examination operators to ionizing radiation. In the two-dimensional cine phase contrast method, it is not possible to know an optimal measurement cross section before the start of the examination, so it is necessary to blindly set a large number of cross sections on the measurement blood vessel. These restrictions prevent the spread of organ vascular blood flow measurement by these methods.

  With the data measured by the three-dimensional cine phase contrast method and the blood flow analysis application, it is possible to quantify the blood flow velocity and flow rate in the blood vessel region to be analyzed, and to analyze the flow line, the shear stress of the blood vessel wall, and the like. In the three-dimensional cine phase contrast method, unlike the two-dimensional cine phase contrast method, an arbitrary measurement cross section can be set after data collection, so that more accurate blood flow can be measured retrospectively. Furthermore, there is an advantage that the spatial resolution is high and the imaging of complex blood vessels is excellent (see, for example, Non-Patent Document 1). On the other hand, the three-dimensional cine phase contrast method has a problem that it is easily affected by the turbulent flow generated in the blood vessel because the imaging time is long. For this reason, for example, depending on the selected measurement cross section, there is a problem that the measurement flow rate greatly fluctuates due to the influence of turbulent flow and the measurement result becomes inaccurate (for example, see Non-Patent Document 2).

Markl, et al., 'Time-Resolved Three-Dimensional Phase-Contrast MRI', JOURNAL OF MAGNETIC RESONANCE IMAGING, 2003, vol.17, p.499-506. Ishikawa, et al., ‘Hemodynamic assessment in a child with renovascular hypertension using time-resolved three-dimensional cine phase-contrast MRI.’, JOURNAL OF MAGNETIC RESONANCE IMAGING, 2014 Feb 24, DOI: 10.1002 / jmri.24522

  An object of the present invention is to provide a method for more accurately measuring a blood flow profile of a blood vessel based on data acquired by 3D cine PC MR, and a blood flow measurement device that implements the method. .

The present invention provides the following blood flow profile measuring method and blood flow measuring device.
[1] (1) A step of constructing a blood vessel image depicting a three-dimensional blood vessel structure from a magnitude image acquired by a three-dimensional cine phase contrast magnetic resonance method;
(2) measuring a blood flow vector at each coordinate in the blood vessel in the blood vessel image from a phase image acquired by a three-dimensional cine phase contrast magnetic resonance method;
(3) measuring a time-average wall shear stress or a vibration shear index at a boundary coordinate of a blood vessel wall in the blood vessel image based on the blood flow vector;
(4) Among the blood vessel walls in the blood vessel image, a measurement cross section consisting only of boundary coordinates whose time average wall shear stress is equal to or greater than a predetermined first threshold value or whose vibration shear index is equal to or smaller than a predetermined second threshold value. Extracting the
(5) measuring a blood flow profile in the measurement cross section;
A method for measuring a blood flow profile.
[2] In the step (4), a measurement cross section including only boundary coordinates in which the inter-average wall shear stress is not less than the first threshold and the vibration shear index is not more than the second threshold is extracted. [1] The method for measuring a blood flow profile.
[3] In the step (4), a plurality of measurement cross sections are extracted,
The blood flow profile measurement method according to [1] or [2], wherein the step (5) is performed on one arbitrarily selected from a plurality of extracted measurement cross sections.
[4] The blood flow profile measurement method according to any one of [1] to [3], wherein the blood vessel image is obtained by reconstructing a three-dimensional blood vessel structure from the magnitude image by a maximum intensity projection method. .
[5] The blood flow profile measurement method according to any one of [1] to [4], wherein the first threshold value is a numerical value within a range of 0.2 to 0.8 Pa.
[6] The blood flow profile measurement method according to any one of [1] to [5], wherein the second threshold value is a numerical value within a range of 0.2 to 0.4.
[7] The method for measuring a blood flow profile according to any one of [1] to [6], wherein the blood flow volume in the measurement cross section is measured based on the blood flow profile measured in the step (5).
[8] The blood flow profile measurement method according to [7], wherein the blood flow volume in the measurement cross section is a blood flow volume per heartbeat in the measurement cross section.
[9] A data acquisition unit that acquires a magnitude image and a phase image acquired by a three-dimensional cine phase contrast magnetic resonance method;
A memory for storing a magnitude image and a phase image acquired by the data acquisition unit, a first threshold value set for a measurement value of a time average wall shear stress, and a second threshold value set for a measurement value of a vibration shear index. And
A control unit for measuring a blood flow profile and a blood flow volume based on the magnitude image, the phase image, the first threshold value, and the second threshold value stored in the storage unit;
A blood flow profile and a measurement section for measuring blood flow, a blood flow profile, and a display unit for displaying the blood flow,
The control unit is
A blood vessel image constructing unit that constructs a blood vessel image depicting a three-dimensional blood vessel structure from the magnitude image of the storage unit;
A blood flow vector measurement unit that measures a blood flow vector at each coordinate in the blood vessel in the blood vessel image from the phase image of the storage unit and the blood vessel image constructed by the blood vessel image construction unit;
From the blood flow vector obtained by the blood flow vector measurement unit and the blood vessel image constructed by the blood vessel image construction unit, the time average wall shear stress and the vibrational shear index at the boundary coordinates of the blood vessel wall in the blood vessel image are measured. An AWS / OSI measurement unit;
Among the blood vessel walls in the blood vessel image, the time-average wall shear stress is not less than the first threshold stored in the storage unit, or the vibration shear index is not more than the second threshold stored in the storage unit. A measurement cross-section extraction unit that extracts a measurement cross-section consisting only of boundary coordinates,
A blood flow measurement device including a blood flow profile and a blood flow measurement unit that measures a blood flow in the measurement cross section extracted by the measurement cross section extraction unit.

  The blood flow profile measuring method and the blood flow measuring device according to the present invention can measure the blood flow profile and the blood flow more accurately based on the magnitude image and phase image data acquired by the 3D cine PC MR. it can.

It is a figure showing one mode of composition of a blood flow rate measuring device concerning the present invention. It is a figure which shows the function structure of the control part which the blood flow rate measuring apparatus which concerns on this invention has. It is a flowchart which shows the process sequence of the control part which the blood flow rate measuring apparatus which concerns on this invention has. In Example 1, it is the blood vessel image which displayed the measured value of OSI on the blood vessel surface lightly. In Example 1, it is the blood vessel image which displayed the measured value of AWSS on the blood vessel surface lightly. In Example 1, it is the figure which showed the flow velocity curve (vertical axis: average flow velocity (cm / second), horizontal axis: time (second)) in the measurement cross sections AD.

  The phase contrast magnetic resonance method is a method in which MRI imaging is performed by applying a gradient magnetic field to the imaging section, and the motion velocity distribution of water molecules can be estimated from the phase difference of proton precession. In the three-dimensional phase contrast magnetic resonance method, the phase contrast magnetic resonance method is a three-dimensional imaging method. Specifically, a phase gradient is measured as a signal difference by applying a bipolar gradient magnetic field in the XYZ axis directions. For this reason, each pixel of the phase image acquired from the phase data in the XYZ-axis directions has data on the direction of blood flow and the magnitude of blood flow velocity at the pixel. On the other hand, by stacking magnitude images acquired by the three-dimensional phase contrast magnetic resonance method (morphological images in which blood vessels and the like are depicted by signal intensity), a blood vessel image in which the blood vessel shape is depicted three-dimensionally is obtained. Therefore, by superimposing the layered phase images with the blood vessel image obtained from the magnitude image, information on blood flow velocity distribution (blood flow vector (blood flow vector at any spatial position in the blood vessel) is obtained. Direction and speed)).

  As for the blood flow rate, the flow rate and flow velocity periodically change within one heartbeat due to the pulsation of the heart. For this reason, in particular, when the blood vessel for which blood flow is to be obtained is an aorta or a distribution artery, it is preferable to obtain the blood flow per heartbeat. 3D cine PC MR is a method in which a three-dimensional phase contrast magnetic resonance method is continuously imaged over time along the cardiac cycle of an electrocardiogram, and velocity vectors (blood flow vectors) of all spatiotemporal regions within the imaging range. Can be measured. The 3D cine PC MR is also referred to as 4D flow MR because three-dimensional blood flow information is obtained in each cardiac time phase of one heartbeat.

  The blood flow profile and blood flow volume of the target blood vessel can be measured from information on the blood flow vector, but when the target blood vessel has turbulent flow such as vortex flow, the measured flow rate fluctuates greatly, and the measurement result is inferior. Be accurate. For this reason, in order to measure a more accurate blood flow profile and blood flow volume, it is preferable to set the measurement cross section in a region of the target blood vessel where turbulence does not occur.

  For example, from the information of the blood flow vector in each spatial coordinate (each pixel) in the blood vessel in each cardiac time phase of one heartbeat, the blood flow streamline image is superimposed on the blood vessel image and directly viewed, thereby Among them, a turbulent flow is not generated, and a measurement cross section can be set in a portion where a laminar flow is generated. However, when the measurement cross section is set by visual observation, the fine turbulence is easily overlooked, and the difference between the measurers may be increased.

  A blood flow profile measuring method according to the present invention is a method of measuring a blood flow profile of a target blood vessel based on data acquired by 3D cine PC MR, and a blood vessel cross-section for measuring a blood flow profile, In this method, the target blood vessel is set in a region where the time-averaged wall shear stress (AWSS) is not too low or the oscillating shear index (OSI) is not too high. In a blood vessel in which turbulent flow occurs, AWSS tends to be low and OSI tends to be high. For this reason, by setting the measurement cross section of the blood vessel for measuring the blood flow profile to avoid the region where the AWSSS is low or the region where the OSI is high, the blood flow profile is stable in the portion where the blood flow profile is stable. Since the flow rate can be measured, more accurate blood flow can be measured.

  In the blood flow profile measurement method according to the present invention, the blood flow profile and the blood flow volume are measured based on the data acquired by the 3D cine PC MR, but the flow path is simulated in CFD (Computational Fluid Dynamics) analysis. Even in this case, the blood flow profile and the blood flow measurement cross section can be set by avoiding the region where the AWSS is low or the region where the OSI is high in the blood vessel wall.

That is, the blood flow profile measuring method according to the present invention includes the following steps (1) to (5).
(1) a step of constructing a blood vessel image depicting a three-dimensional blood vessel structure from a magnitude image acquired by 3D cine PC MR;
(2) measuring a blood flow vector at each coordinate in the blood vessel in the blood vessel image from the phase image acquired by 3D cine PC MR;
(3) measuring AWSS or OSI at the boundary coordinates of the blood vessel wall in the blood vessel image based on the blood flow vector;
(4) extracting from the blood vessel wall in the blood vessel image a measurement cross section consisting only of boundary coordinates in which AWSS is equal to or larger than a predetermined first threshold or OSI is equal to or smaller than a predetermined second threshold;
(5) A step of measuring a blood flow profile in the measurement cross section.

  The 3D cine PC MR for acquiring the magnitude image used in the step (1) and the phase image used in the step (2) can apply a bipolar gradient magnetic field, and can be applied over time according to a preset sequence. Using an MRI system capable of imaging the blood vessel, it can be carried out in a conventional manner so that the target blood vessel for measuring the blood flow profile is included in the imaging range. Such MRI systems include, for example, “Signa Advantage Exit 1.5T”, “Signa HDxt 3.0T”, “Discovery MR750 3.0T”, “Discovery MR750w 3.0T” (manufactured by GEHC), “MAGNETOM”. Verio 3T "(manufactured by SIEMENS)," Ingenia 3.0T "," Ingenia 1.5T "," Achieva 1.5T "(manufactured by Philips Electronics) and the like. Before performing imaging by 3D cine PC MR, it is preferable to perform a two-dimensional cine phase contrast magnetic resonance method in advance to determine VENC (velocity encoding).

  The magnitude image used in step (1) may be an image taken without using a contrast agent, or may be an image taken using a contrast agent. Examples of the contrast agent include gadolinium or a derivative thereof.

  In addition, the construction of a blood vessel image for rendering a three-dimensional blood vessel structure from a magnitude image uses an image processing method used for construction of a blood vessel image such as various MIPs (maximum intensity projection). It can be carried out. The boundary coordinates of the blood vessel wall in the constructed blood vessel image can be determined by various image analysis methods used for image segmentation processing such as a threshold method and a region expansion method.

  The phase image used in the step (2) is preferably a phase image captured by applying a bipolar gradient magnetic field in the XYZ axis directions. By superimposing the phase image of the bipolar gradient magnetic field in each direction and further superimposing it on the blood vessel image obtained in step (1), the blood flow vector at each spatial coordinate in the blood vessel is measured. The blood flow vector is expressed as, for example, an X-axis direction component, a Y-axis direction component, and a Z-axis direction component. The obtained blood flow vector can be visualized using an image processing method used for blood flow velocity distribution analysis such as phase velocity mapping.

  Next, as step (3), based on the blood flow vector obtained in step (2) and the blood vessel image obtained in step (1), AWSS or OSI at the boundary coordinates of the blood vessel wall is measured. AWSS and OSI can be calculated by a commonly used blood flow analysis application such as a blood flow analysis processing system “GT Flow” (manufactured by GyroTool).

  When blood with a viscosity μ flows in a blood vessel of radius r, blood near the blood vessel wall is dragged by the viscosity and the blood flow becomes slower than the center. Therefore, the velocity distribution of the blood flow produces a velocity gradient in the radial direction r from the flow axis. The wall shear stress (WSS) is expressed by the following formula (1) from the blood flow velocity u and the radius r of the blood vessel, AWSS is calculated by the following formula (2), and OSI is calculated by the following formula (3).

  After step (3), as step (4), among the blood vessel walls in the blood vessel image, a measurement cross section consisting only of boundary coordinates where AWSS is not less than the first threshold value or OSI is not more than the second threshold value. To extract. The measurement cross section is set perpendicular to the target blood vessel. Only one measurement cross section may be extracted for the target blood vessel, or two or more measurement cross sections may be extracted.

  The first threshold value is set for the measured value of AWSS, and the measured value of AWSS is a boundary value for distinguishing a region where turbulent flow is generated from other laminar flow regions. The second threshold value is set for the OSI measurement value, and is a boundary value for distinguishing the OSI measurement value from the region where the turbulent flow is generated and the other region. In the present invention, a measurement cross section having a smaller influence of turbulent flow can be extracted, and therefore, a measurement cross section including only boundary coordinates in which AWSS is equal to or higher than the first threshold and OSI is equal to or lower than the second threshold is extracted. Is preferred.

  The first threshold value and the second threshold value are the imaging conditions of the magnitude image and phase image used for the analysis, the type of target blood vessel for measuring the blood flow profile, the part in the living body, the type of the animal having the target blood vessel, the disease state, etc. Can be set as appropriate. For example, since there is a tendency for turbulent flow to occur at a portion where a blood vessel is branched or a portion where the blood vessel is bent greatly, the first threshold value and the second threshold value are excluded from the blood vessel branch portion and the bent portion, respectively. Can be set to be. Moreover, it can also be determined based on experience so that the part where turbulent flow is generated is removed from the streamline analysis of blood flow. For example, the first threshold value can be a numerical value in the range of 0.2 to 0.8 Pa, for example, and is preferably a numerical value in the range of 0.2 to 0.4 Pa. Moreover, as a 2nd threshold value, it can be set as the numerical value below 0.4, for example, it is preferable to set it as the numerical value within the range of 0.1-0.4, and the range of 0.1-0.3 It is more preferable that the value be within the range.

  The 1st threshold value and the 2nd threshold value should just be set before process (4), may be preset before performing process (3), and were obtained at process (3). You may set based on the measured value of AWSS or OSI. For example, the first quartile value (25% of the measured values are arranged in ascending order) or the second quartile value (the measured value is small) in all the blood vessel walls in the constructed blood vessel image. Arranged in order, the 50% value and the median value) can be used as the second threshold value. Similarly, the first quartile value and the second quartile value of the measured values of AWSS in all blood vessel walls in the constructed blood vessel image can be set as the second threshold value.

  For example, the blood vessel surface in the blood vessel image may be color-coded according to the OSI measurement value or the AWSS measurement value, and the measurement cross section may be extracted using the color of the blood vessel surface as an index. For example, by creating an OSI grayscale image in which the blood vessel surface in the blood vessel image is color-coded according to the magnitude of the OSI measurement value so that the color becomes darker as the OSI measurement value increases, the OSI measurement value is obtained. It can be visualized. The measurement cross section is set in a light color region where the OSI is equal to or less than the second threshold among the target blood vessels in the OSI gray image. In addition, the blood vessel surface in the blood vessel image is color-coded by binarization processing in which a region where the measured value of OSI is less than or equal to the second threshold is white and a region where the OSI exceeds the second threshold is color-coded to a color other than white. When an image is created, a measurement cross section is extracted from an area where the blood vessel wall is white. Similarly, for AWSSS, a measurement cross section can be extracted based on an image color-coded according to the magnitude of the AWSWS measurement value.

  Finally, as step (5), the blood flow profile in the measurement cross section extracted in step (4) is measured. The blood flow profile is measured based on the blood flow velocity at each cardiac phase in the measurement cross section. The blood flow velocity is the sum of the magnitudes of the components in the direction perpendicular to the measurement cross section of the blood flow vector at each pixel in the measurement cross section (that is, the direction parallel to the blood vessel).

  Based on the blood flow profile measured in the step (5), the blood flow volume in the measurement cross section can be measured. In the present invention, the blood flow volume per heartbeat in the measurement cross section or the blood flow volume obtained by dividing the blood flow volume per heartbeat by the time of one heartbeat is measured. Specifically, the area under the curve (AUC) of the blood flow profile curve is the blood flow volume per heartbeat. You may obtain | require in a measurement cross section as a product of the average blood flow velocity of a perpendicular direction to the said measurement cross section, and the area of the said measurement cross section. In addition, the blood flow profile in the measurement cross section, the blood flow volume per one heartbeat, and the like can be measured by a commonly used blood flow analysis application such as “GT Flow” (manufactured by GyroTool).

  In the step (4), when a plurality of measurement cross sections are extracted, the blood flow profile may be measured for all the extracted measurement cross sections, and 1 arbitrarily selected from the plurality of extracted measurement cross sections. The blood flow profile may be measured for one. The selection of one measurement cross-section for measuring a blood flow profile from a plurality of measurement cross-sections may be performed based on OSI measurement values or AWSS measurement values, or may be performed based on other indicators such as blood vessel shape. . For example, the measurement cross section having the smallest OSI maximum value of the boundary coordinates of the blood vessel wall constituting the measurement cross section can be selected as the measurement cross section for measuring the blood flow profile. In addition, since turbulent flow is likely to occur in relatively thin blood vessels, curved portions, and branch portions, one measurement cross section for measuring a blood flow profile is selected from measurement cross sections extracted from other than these portions. It is preferable. For example, a measurement cross section that is in the main trunk before branching and that is not in the curved portion but in a portion having a certain running distance from the branching portion can be selected as the measurement cross section for measuring the blood flow profile.

  The blood flow profile measurement method according to the present invention includes a data acquisition unit that acquires a magnitude image and a phase image acquired by 3D cine PC MR, a magnitude image and a phase image acquired by the data acquisition unit, and a first threshold value. And a storage unit that stores the second threshold value, and a control unit that measures a blood flow profile and a blood flow rate based on the magnitude image, the phase image, the first threshold value, and the second threshold value stored in the storage unit The present invention can also be implemented using a blood flow measuring device including a blood flow profile and a measurement cross section for measuring the blood flow, a blood flow profile, and a display unit for displaying the blood flow. One mode of the blood flow measuring device is shown in FIG. As shown in FIG. 1, the blood flow measuring device 1 includes a control unit 2, a data acquisition unit 3, a storage unit 4, and a display unit 5.

  The control unit 2 includes a calculation unit such as a CPU, and is a processing unit that controls the blood flow measurement device 1 and operates according to a program stored in the storage unit 4. Based on the data of 3D cine PC MR acquired by the data acquisition unit 3, the control unit 2 extracts a measurement cross section for measuring the blood flow profile and the blood flow volume from the target blood vessel, and measures the blood flow profile and the blood flow volume. The measured results are shown on the display unit 5.

  The data acquisition unit 3 is a processing unit that acquires a magnitude image and a phase image acquired by 3D cine PC MR. In addition, electrocardiogram data can be acquired from the data acquisition unit 3. The data acquired by the data acquisition unit 3 is stored in the storage unit 4 under the control of the control unit 2. The data acquisition unit 3 may be directly connected to an MRI apparatus capable of performing 3D cine PC MR.

  The storage unit 4 is a processing unit that stores the magnitude image and phase image acquired by the data acquisition unit 3, the first threshold value, and the second threshold value. As the first threshold value and the second threshold value, preset values may be inputted and stored in the storage unit 4, and those set based on the result of calculation by the control unit 2 are stored in the storage unit 4. May be. The image data generated by the control unit 2 and the calculation result by the control unit 2 are also stored. The storage unit 4 is configured using a nonvolatile storage device such as a magnetic hard disk or a semiconductor storage device, and also operates as a work memory of the control unit 2.

  The display unit 5 is a processing unit that displays image data stored in the storage unit 4 and various types of information such as calculation results by the control unit 2. The display unit 5 is configured using a display device such as a liquid crystal display panel or an organic EL display panel.

  FIG. 2 is a diagram illustrating a functional configuration of the control unit 2. The control unit 2 includes a blood vessel image construction unit 21, a blood flow vector measurement unit 22, an AWSS / OSI measurement unit 23, a measurement cross section extraction unit 24, and a blood flow rate measurement unit 25. FIG. 3 shows the control unit 2 until the magnitude image and the phase image acquired by the 3D cine PC MR are stored in the storage unit 4 via the data acquisition unit 3 and the blood flow profile and the blood flow rate are measured. It is a flowchart which shows a process sequence. Steps S1 to S5 in FIG. 3 (steps (1) to (5) of the blood flow profile measuring method according to the present invention) are operations performed by the control unit 2, respectively.

  First, the blood vessel image construction unit 21 reads out a magnitude image from the storage unit 4, and constructs a blood vessel image that renders a three-dimensional blood vessel structure from the magnitude image (step S1). For the constructed blood vessel image, the boundary coordinates of the blood vessel wall are also determined. The boundary coordinates of the blood vessel wall can be determined by various image analysis methods used for image segmentation processing, such as a threshold method and a region expansion method. The constructed blood vessel image and the boundary coordinates of the blood vessel wall are stored in the storage unit 4 in association with the used magnitude image. Next, the blood flow vector measurement unit 22 reads the blood vessel image constructed by the phase image and the blood vessel image construction unit 21 from the storage unit 4, and measures the blood flow vector at each coordinate in the blood vessel in the blood vessel image (step S2). ). The blood flow vector at each measured coordinate is stored in the storage unit 4 in association with the used blood vessel image.

  Next, the AWSS / OSI measurement unit 23 uses the blood flow vector of each coordinate obtained by the blood flow vector measurement unit 22 and the blood vessel image constructed by the blood vessel image construction unit 21 to determine the boundary coordinates of the blood vessel wall in the blood vessel image. Measure the AWSS and OSI at step S3. The measurement of AWSS and OSI by the AWSS / OSI measurement unit 23 can be performed, for example, in the same manner as a blood flow analysis application conventionally used for the measurement of AWSS and OSI. The measured AWSS and OSI at each boundary coordinate are stored in the storage unit 4 in association with the used blood vessel image and blood flow vector.

  Subsequently, the measurement cross-section extraction unit 24 reads out the blood vessel image from the storage unit 4, the measured value of AWSS and the first threshold value or the measured value of OSI and the second threshold value at the boundary coordinates of each blood vessel wall, From the blood vessel wall in the blood vessel image, a measurement cross section consisting only of boundary coordinates in which the measured value of AWSS is equal to or greater than the first threshold value or the measured value of OSI is equal to or smaller than the second threshold value is extracted (step S4). Only one measurement cross section may be extracted, or two or more measurement cross sections may be extracted. The extracted measurement cross section is stored in the storage unit 4 in association with the used blood vessel image, the AWSSS measurement value, and / or the OSI measurement value.

  When the first threshold value and the second threshold value are not set in advance and are set from the measured values of AWSS and OSI obtained in step S3, the control unit 2 further includes a threshold value setting unit, and step S3 Then, before step S4, the threshold value setting unit sets the first threshold value or the second threshold value based on the measured value of AWSS or the measured value of OSI (not shown). For example, the threshold setting unit can calculate the first quartile value and the second quartile value of all the OSI measurement values measured in step S3, and set this as the second threshold value. Similarly, the threshold setting unit can calculate the first quartile value and the second quartile value of all the AWSS measurement values measured in step S3, and can set this as the first threshold value.

  The measurement cross section extracted in step S4 can be displayed on the display unit 5 together with the blood vessel image under the control of the control unit 2. It is preferable that the blood vessel wall surface of the blood vessel image is displayed in a color-coded manner according to OSI or AWSSS measurement values. For example, by dividing the OSI measurement value from the minimum value to the maximum value into N equal parts and assigning and displaying different colors for each division (for example, display of shades depending on the magnitude of the measurement value), the OSI of the measurement cross section can be changed. It can be displayed that it is below the second threshold.

  After step S4, the blood flow measuring unit 25 measures the blood flow profile and the blood flow in the measurement cross section extracted by the measurement cross section extracting unit 24 (step S5). Specifically, a blood flow profile is created based on the blood flow velocity at each cardiac phase in the measurement cross section, and the area under the curve of the blood flow profile curve is defined as the blood flow volume per heartbeat. The blood flow profile and the blood flow measurement in the measurement cross section by the blood flow measurement unit 25 are, for example, a blood flow analysis application conventionally used for measuring the blood flow profile and the blood flow in the blood vessel cross section set in the target blood vessel. The same can be done.

  When a plurality of measurement cross sections are extracted in step S4, the blood flow profile and the blood flow volume may be measured for all the extracted measurement cross sections, and only one measurement cross section selected from the extracted measurement cross sections is measured. A blood flow rate or the like may be measured. Selection of one measurement cross section for measuring a blood flow profile and blood flow volume from a plurality of measurement cross sections may be performed based on the measured value of OSI or the measured value of AWSS obtained in step 3, or selected according to other indicators. May be. For example, the blood flow profile and blood flow volume can be measured by selecting the measurement cross section having the smallest OSI maximum value of the boundary coordinates of the blood vessel wall constituting the measurement cross section. The measured blood flow profile and blood flow volume are stored in the storage unit 4 in association with the used blood vessel image and the measurement cross section.

  The blood flow volume of the target blood vessel obtained by the blood flow volume measurement unit 25 is displayed on the display unit 5 under the control of the control unit 2. A blood flow profile curve with the vertical axis representing blood flow velocity and the horizontal axis representing time (cardiac phase) may also be displayed together with the measured blood flow. In addition, the measured blood flow profile and blood flow volume can be displayed together with the measurement cross section extracted in step 4.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Example 1]
An abdominal artery of a human subject (a healthy 29-year-old male) was imaged by 3D cine PC MR, and a blood flow profile and a blood flow were measured from the obtained data.
The 3D cine PC MR was imaged using “Discovery MR750 3.0T” (manufactured by GEHC). Imaging conditions were as follows.

TR (ms) / TE (ms) / FA (degree) / NEX: 7.0-7.1 / 3.3-3.4 / 8/1,
field of view (cm): 32,
matrix: 256 × 256,
slice thickness (mm): 1.25
locs / slab: 8,
phases: 19,
projection: 10000,
velocity encoding (VENC) (cm / s): 100-200,
Imaging time (min): 10.

The magnitude image obtained by 3D cine PC MR was subjected to MIP processing, and the obtained MIP image was subjected to region expansion to determine the boundary coordinates of the vessel wall, thereby reconstructing a three-dimensional vessel structure.
Next, the blood flow analysis processing system “GT Flow” (manufactured by GyroTool) analyzes the obtained blood vessel model image (blood vessel image) and the phase image data obtained by 3D cine PC MR, and the blood vessels in the blood vessel image are analyzed. AWSS and OSI at the wall boundary coordinates were measured.

  FIG. 4 shows a blood vessel image in which the OSI measurement value is displayed on the blood vessel surface in a light and shaded manner so that the color becomes darker as the value increases, and the measurement value of AWSS is also displayed on the blood vessel surface. FIG. 5 shows blood vessel images displayed so as to be dark and light. As shown in FIG. 4, the portion where the blood vessel is branched or bent is dark in color, and the measured value of OSI is larger. Further, as shown in FIG. 5, the color of the portion where the blood vessel is branched or bent is relatively light, and the measured value of AWSS is relatively small.

  Among the blood vessels in this blood vessel image, the blood vessels branching from the abdominal artery running up and down are set as target blood vessels, and the blood flow profile and the blood flow volume for measuring the blood flow volume are set at four locations of the target blood vessels. The measurement sections A to D (A to D in FIGS. 4 and 5) were sequentially formed from the proximal portion. Table 1 shows the maximum value of OSI and the minimum value of AWSS in the boundary coordinates of the blood vessel wall of each measurement section. The value of OSI was lower at the distal measurement cross section.

  With respect to all measurement cross sections, the average flow velocity (s / second) was measured by “GT Flow”, and a blood flow profile curve (flow velocity curve) with the average flow velocity on the vertical axis and time (second) on the horizontal axis was created. The flow velocity curve of each measurement cross section is shown in FIG. As a result, the blood flow velocity drops to near 0 s / second at 0.833 seconds in the flow velocity curve of the measurement cross section A and 0.722 seconds in the flow velocity curve of the measurement cross section B. It was suggested that occurred. In the flow velocity curve of the measurement cross section C, an excessive decrease in the blood flow velocity was not observed, but the peak flow velocity was slower than that of the measurement cross section D. That is, the flow velocity curve of the measurement cross section D having the smallest OSI maximum value and the largest AWSSS minimum value is closest to the normal pattern, and blood flow in the measurement cross sections A to C is measured by measuring the blood flow volume of the cross section. It was found that more accurate blood flow can be measured than measuring the flow rate. Actually, when streamline analysis was performed, strong turbulent flow was observed in the measurement cross sections A and B, but no turbulent flow was observed in the measurement cross section D (not shown). In addition, the blood flow volume per heartbeat in the measurement cross section D can be calculated by obtaining the area of the measurement cross section in the AUC of this flow velocity curve.

DESCRIPTION OF SYMBOLS 1 ... Blood flow rate measuring apparatus, 2 ... Control part, 3 ... Data acquisition part, 4 ... Memory | storage part, 5 ... Display part, 21 ... Blood-vessel image construction part, 22 ... Blood flow vector measurement part, 23 ... AWSS / OSI measurement part 24 ... Measurement cross-section extraction unit, 25 ... Blood flow measurement unit.

Claims (9)

(1) constructing a blood vessel image for depicting a three-dimensional blood vessel structure from a magnitude image acquired by a three-dimensional cine phase contrast magnetic resonance method;
(2) measuring a blood flow vector at each coordinate in the blood vessel in the blood vessel image from a phase image acquired by a three-dimensional cine phase contrast magnetic resonance method;
(3) measuring a time-average wall shear stress or a vibration shear index at a boundary coordinate of a blood vessel wall in the blood vessel image based on the blood flow vector;
(4) Among the blood vessel walls in the blood vessel image, a measurement cross section consisting only of boundary coordinates whose time average wall shear stress is equal to or greater than a predetermined first threshold value or whose vibration shear index is equal to or smaller than a predetermined second threshold value. Extracting the
(5) measuring a blood flow profile in the measurement cross section;
A method for measuring a blood flow profile.   In the step (4), a measurement cross section consisting only of boundary coordinates whose inter-average wall shear stress is not less than the first threshold and whose vibration shear index is not more than the second threshold is extracted. The blood flow profile measurement method described. In the step (4), a plurality of measurement cross sections are extracted,
The blood flow profile measurement method according to claim 1 or 2, wherein the step (5) is performed for one arbitrarily selected from the plurality of extracted measurement cross sections.   The blood vessel profile measurement method according to any one of claims 1 to 3, wherein the blood vessel image is obtained by reconstructing a three-dimensional blood vessel structure from the magnitude image by a maximum intensity projection method.   The blood flow profile measurement method according to any one of claims 1 to 4, wherein the first threshold value is a numerical value within a range of 0.2 to 0.8 Pa.   The blood flow profile measurement method according to any one of claims 1 to 5, wherein the second threshold value is a numerical value within a range of 0.2 to 0.4.   Furthermore, based on the blood flow profile measured in the said process (5), the blood flow rate in the said measurement cross section is measured, The blood flow profile measuring method as described in any one of Claims 1-6.   The blood flow profile measurement method according to claim 7, wherein the blood flow volume in the measurement cross section is a blood flow volume per heartbeat in the measurement cross section. A data acquisition unit for acquiring a magnitude image and a phase image acquired by a three-dimensional cine phase contrast magnetic resonance method;
A memory for storing a magnitude image and a phase image acquired by the data acquisition unit, a first threshold value set for a measurement value of a time average wall shear stress, and a second threshold value set for a measurement value of a vibration shear index. And
A control unit for measuring a blood flow profile and a blood flow volume based on the magnitude image, the phase image, the first threshold value, and the second threshold value stored in the storage unit;
A blood flow profile and a measurement section for measuring blood flow, a blood flow profile, and a display unit for displaying the blood flow,
The control unit is
A blood vessel image constructing unit that constructs a blood vessel image depicting a three-dimensional blood vessel structure from the magnitude image of the storage unit;
A blood flow vector measurement unit that measures a blood flow vector at each coordinate in the blood vessel in the blood vessel image from the phase image of the storage unit and the blood vessel image constructed by the blood vessel image construction unit;
From the blood flow vector obtained by the blood flow vector measurement unit and the blood vessel image constructed by the blood vessel image construction unit, the time average wall shear stress and the vibrational shear index at the boundary coordinates of the blood vessel wall in the blood vessel image are measured. An AWS / OSI measurement unit;
Among the blood vessel walls in the blood vessel image, the time-average wall shear stress is not less than the first threshold stored in the storage unit, or the vibration shear index is not more than the second threshold stored in the storage unit. A measurement cross-section extraction unit that extracts a measurement cross-section consisting only of boundary coordinates,
A blood flow measurement device including a blood flow profile and a blood flow measurement unit that measures a blood flow in the measurement cross section extracted by the measurement cross section extraction unit.