CN-116485703-B - Magnetic resonance imaging apparatus, image analysis apparatus, and fluid analysis method

CN116485703BCN 116485703 BCN116485703 BCN 116485703BCN-116485703-B

Abstract

The invention provides a magnetic resonance imaging apparatus, an image analysis apparatus, and a fluid analysis method. Fluid parameters such as WSS and EL are accurately calculated using flow velocity information obtained by diffusion tensor imaging. The variance of the flow velocity distribution of the fluid is calculated using a diffusion tensor image obtained for an inspection object containing the fluid, an estimation model is set for the distribution shape of the flow velocity in the voxel, and the differential value of the flow velocity is calculated using the estimation model and the variance of the flow velocity distribution. Using the calculated differential value, a fluid parameter that characterizes the flow of the fluid is calculated.

Inventors

BITO YOSHITAKA
Yue Zhijiuhuang

Assignees

富士胶片医疗健康株式会社

Dates

Publication Date: 20260512
Application Date: 20220920
Priority Date: 20220113

Claims (13)

1. A magnetic resonance imaging apparatus, comprising: A measuring unit for performing a pulse sequence including diffusion weighted imaging of MPG pulses which are diffusion gradient magnetic fields, and obtaining measurement data, and A calculation unit that calculates a pseudo diffusion tensor of the fluid in the inspection object, which is a tensor representing information obtained by mixing the flow velocity and the diffusion, using the measurement data acquired by the measurement unit, The arithmetic unit includes: A fluid parameter calculation unit that calculates fluid parameters other than the pseudo diffusion tensor using an estimated model of the intra-voxel distribution of the pseudo diffusion tensor and the flow velocity, The fluid parameter calculating unit calculates a variance of a flow velocity distribution using the pseudo diffusion tensor, calculates a flow velocity differential vector using the calculated variance of the flow velocity distribution and the estimation model, calculates the fluid parameter based on the flow velocity differential vector, The fluid parameters calculated by the fluid parameter calculation unit include any 1 or more of wall shear stress, WSS, kinetic energy, KE, energy loss, EL, vibration shear index, OSI, and pressure gradient, PG.
2. The magnetic resonance imaging apparatus according to claim 1, wherein, The operation unit further includes an image generation unit that generates an image having the value of the fluid parameter as a pixel value, and displays the image on a display device.
3. The magnetic resonance imaging apparatus according to claim 1, wherein, The flow velocity distribution of the estimation model used by the fluid parameter calculation unit is a rectangular distribution.
4. The magnetic resonance imaging apparatus according to claim 1, wherein, The flow velocity distribution of the estimation model used by the fluid parameter calculation unit is a gaussian distribution.
5. The magnetic resonance imaging apparatus according to claim 1, wherein, The estimation model contains an index representing the deviation from the linear flow in the fluid, The calculation unit calculates the index from the pseudo diffusion tensor.
6. The magnetic resonance imaging apparatus according to claim 5, wherein, The calculation unit calculates the index from the pseudo diffusion tensor calculated for each of a plurality of diffusion times.
7. The magnetic resonance imaging apparatus according to claim 1, wherein, The measurement section collects measurement data in synchronization with the periodic body movement of the inspection object by the diffusion weighted imaging, The fluid parameter calculation unit calculates the fluid parameter by adding the information on the periodic body movement.
8. The magnetic resonance imaging apparatus according to claim 1, wherein, The measuring section performs the pulse sequence of diffusion weighted imaging to acquire complex-valued measurement data, The calculation unit calculates a flow velocity of the fluid in the inspection object using the phase information of the complex-valued measurement data, The fluid parameter calculation unit calculates the fluid parameter using the pseudo diffusion tensor, the flow rate, and the estimation model.
9. The magnetic resonance imaging apparatus according to claim 1, wherein, The measuring section performs a1 st measurement of a pulse sequence using the diffusion weighted imaging and a2 nd measurement of a pulse sequence using a phase contrast method, The arithmetic unit further includes: And a2 nd fluid parameter calculating unit that calculates the fluid parameter using the measurement data obtained in the 2 nd measurement.
10. The magnetic resonance imaging apparatus according to claim 9, wherein, The arithmetic unit further includes: And a parameter combining unit configured to combine the fluid parameter calculated by the fluid parameter calculating unit and the fluid parameter calculated by the 2 nd fluid parameter calculating unit.
11. The magnetic resonance imaging apparatus according to claim 9, wherein, The magnetic resonance imaging apparatus further includes: an input unit for receiving a condition related to a fluid to be measured, The measurement unit selectively performs the pulse sequence of the diffusion weighted imaging and the pulse sequence of the phase contrast method in accordance with the condition received by the input unit.
12. An image analysis device is characterized by comprising: a receiving unit that receives measurement data measured by the magnetic resonance imaging apparatus or a value of a pseudo diffusion tensor calculated from the measurement data, the pseudo diffusion tensor being a tensor representing information obtained by mixing a flow rate and a diffusion, and An operation unit for performing an operation on the data, Wherein when the receiving unit receives the measurement data, the computing unit calculates a pseudo diffusion tensor from the measurement data, The arithmetic unit includes: a fluid parameter calculation unit that calculates a fluid parameter that is an index indicating a characteristic of the flow of the fluid, using the value of the pseudo diffusion tensor received by the receiving unit or the calculated pseudo diffusion tensor and an estimated model of the flow velocity distribution, The fluid parameter calculation unit further includes: A variance calculating unit for calculating a variance of the flow velocity distribution based on the value of the pseudo diffusion tensor received by the receiving unit or the calculated pseudo diffusion tensor, and A differential calculation unit that calculates a differential flow velocity vector using the calculated variance of the flow velocity distribution and the estimation model, The fluid parameters calculated by the fluid parameter calculation unit include any 1 or more of wall shear stress, WSS, kinetic energy, KE, energy loss, EL, vibration shear index, OSI, and pressure gradient, PG.
13. A method for analyzing a fluid using a diffusion tensor image acquired by a magnetic resonance imaging apparatus for an object to be examined including the fluid, the method comprising: A step of calculating a variance of a flow velocity distribution of the fluid using the diffusion tensor image; A step of calculating a differential value of the flow velocity using the variance and the distribution shape of the flow velocity in the voxel, and A step of calculating a fluid parameter indicating a characteristic of the flow of the fluid using the differential value, In the step of calculating the fluid parameter, the fluid parameter including at least 1 of wall shear stress, WSS, kinetic energy, KE, energy loss, EL, vibration shear index, OSI, and pressure gradient, PG is calculated.

Description

Magnetic resonance imaging apparatus, image analysis apparatus, and fluid analysis method Technical Field The present invention relates to a magnetic resonance imaging (hereinafter abbreviated as MRI) apparatus and a technique for analyzing measurement data acquired by the MRI apparatus, and more particularly to a technique for analyzing diffusion tensor images. Background By analyzing the flow of fluid flowing in the brain or body of a person, an index effective for diagnosing various lesions can be obtained. For example, fluid parameters such as wall shear stress (WSS: WALL SHEAR STRESS), kinetic energy of fluid (KE: KINETIC ENERGY), and kinetic Energy Loss (EL) are effective indicators for detecting abnormalities in the flow of blood and cerebrospinal fluid, and various techniques for measuring and analyzing the fluid parameters have been proposed. As one of them, patent document 1 discloses a method of analyzing kinetic energy loss or the like from the obtained measurement data using a Phase Contrast (PC) method of MRI. In the PC method, the gradient magnetic field pulse for phase-releasing the NMR signal and the gradient magnetic field pulse for phase-converging the NMR signal are combined to make the phases of the signal from the stationary portion and the signal from the flowing portion different, thereby calculating the velocity of the fluid such as blood flowing in the desired region. In the technique described in patent document 1, difference information of adjacent vectors is calculated from a graph of velocity vector values of a fluid (a blood flow vector image in which the velocity vector values are defined as pixel values) obtained by the PC method, and EL or the like is calculated using the difference. Further, as an imaging method of MRI that can observe a fluid, there are Diffusion Weighted Imaging (DWI) and Diffusion Tensor Imaging (DTI). DTI is a technique for showing information indicating anisotropy of diffusion for each voxel from measurement data obtained by DWI using MPG pulses in at least 6 directions by using diffusion tensors, and is reported to be effective in observation of pseudo-random flow of cerebrospinal fluid and the like in non-patent document 1. Prior art literature Patent literature Patent document 1 JP patent No. 6467341 specification Non-patent literature Non-patent documents 1:Magnetic Resonance in Medicine 2021;86, 1369-1382 In the PC method, it is necessary to apply a phase-concentrated gradient magnetic field pulse to a phase-diffused dephased gradient magnetic field pulse at a predetermined time interval, and repeatedly perform a pulse sequence of an acquisition signal, whereby the spatial resolution of an image is relatively low. When the difference between adjacent vectors is obtained in a blood flow vector image having a low spatial resolution, the differential value of the flow velocity is calculated to be lower than the actual differential value, and there is a possibility that an error in the blood flow parameter value such as EL calculated by this calculation increases. Especially in the case of a slow fluid velocity, the error tends to be large. Disclosure of Invention The present invention addresses the problem of providing a technique for accurately calculating fluid parameters using MRI. In particular, the accuracy of fluid parameter calculation is improved for slow fluid. In order to solve the above problems, the present invention calculates a differential vector of a flow velocity using flow velocity information obtained by diffusion tensor imaging and a model of flow velocity distribution, thereby calculating a fluid parameter. Specifically, the MRI apparatus of the present invention includes a measuring unit that acquires measurement data by executing a pulse sequence including diffusion weighted imaging of MPG pulses, and a calculating unit that calculates a pseudo diffusion tensor having information on a flow velocity and diffusion of a fluid in an inspection object by using the measurement data acquired by the measuring unit, wherein the calculating unit includes a fluid parameter calculating unit that calculates fluid parameters other than the pseudo diffusion tensor by using an estimated model of the pseudo diffusion tensor and the intra-voxel distribution of the flow velocity. The image analysis device according to the present invention is an independent analysis device having a function of the calculation unit of the MRI device, and includes a reception unit that receives measurement data measured by the MRI device or a pseudo diffusion tensor value calculated from the measurement data, and a calculation unit that calculates a fluid parameter using the measurement data or the pseudo diffusion tensor value received by the reception unit, wherein the calculation unit includes a fluid parameter calculation unit that calculates a fluid parameter that is an index indicating a characteristic of a fluid flow using an estimated model of a pseudo dif