JP2022048875A - Magnetic resonance imaging device - Google Patents

Abstract

To generate information on an interaction derived from biological information such as a ventricular-vascular interaction by a non-invasive method based on a magnetic resonance signal.SOLUTION: A magnetic resonance imaging device in an embodiment includes: an acquisition unit for acquiring first information on the shape of an organ of a subject and second information on the flow of fluid input to and output from the organ simultaneously with a plurality of time phases on the basis of magnetic resonance signals collected by imaging the subject; and an analysis unit for generating diagnosis support information indicating an interaction between the first information and the second information by using the first information and the second information.SELECTED DRAWING: Figure 6

Description

The embodiments disclosed herein and in the drawings relate to a magnetic resonance imaging apparatus.

Physiological changes that reflect interactions such as myocardial behavior, valve behavior in the heart, ventricular volume, and blood flow into and out of the ventricle are called venticular-vascular interactions. This is important information for understanding the pathophysiology of heart diseases such as valve abnormalities.

As a conventional method for obtaining a ventricular vascular integration relationship, a Pressure-Volume loop diagram as an analysis result based on the measurement results of pressure (Pressure) and volume (Volume) of a ventricle (for example, the left ventricle) is known. The Pressure-Volume loop diagram is a method that can obtain a ventricular vascular integration relationship with high reliability. However, in order to create a Pressure-Volume loop diagram, a highly invasive examination such as inserting a device such as a catheter into the heart and measuring the pressure in the ventricle is required.

On the other hand, the magnetic resonance imaging device excites the nuclear spin of a subject placed in a static magnetic field with a high frequency (RF: Radio Frequency) signal of Larmor frequency, and the magnetic resonance signal (MR) generated from the subject with the excitation. (Magnetic Resonance) An image pickup device that reconstructs a signal to generate an image. The magnetic resonance imaging device can collect magnetic resonance signals from a subject non-invasively.

Japanese Unexamined Patent Publication No. 2016-129662

One of the problems to be solved by the embodiments disclosed in the present specification and the drawings is to be able to generate information on interactions derived from biological information such as ventricular vascular integration relations by a non-invasive method based on a magnetic resonance signal. Is to. However, the problems to be solved by the embodiments disclosed in the present specification and the drawings are not limited to the above problems. The problem corresponding to each effect by each configuration shown in the embodiment described later can be positioned as another problem.

The magnetic resonance imaging apparatus of one embodiment has the first information regarding the morphology of the organ of the subject and the flow of fluid input / output to / from the organ based on the magnetic resonance signal collected by imaging the subject. The interaction between the first information and the second information is performed by using the acquisition unit that acquires the two information at the same time and in a plurality of time phases, and the first information and the second information. It is equipped with an analysis unit that generates the indicated diagnostic support information.

The block diagram which shows the whole structure example of the magnetic resonance imaging apparatus which concerns on embodiment. The first figure explaining the concept of a Pressure-Volume loop diagram. The second figure explaining the concept of the Pressure-Volume loop diagram. The figure which shows the concept of the left ventricle volume and the left ventricle flow rate acquired by the magnetic resonance imaging apparatus of this embodiment. A diagram illustrating the concept of a Volume-Flow loop diagram. The figure which shows the detailed configuration example of the magnetic resonance imaging apparatus which concerns on this embodiment. The flowchart which shows the operation example of the magnetic resonance imaging apparatus which concerns on this embodiment. The figure explaining the concept of simultaneous multi-slice collection performed by the magnetic resonance imaging apparatus of this embodiment. The figure which shows an example of the pulse sequence used in the magnetic resonance imaging apparatus of this embodiment. Operational conceptual diagram showing that a plurality of slice cross sections are excited by a multi-band excitation pulse. The figure which shows the concept of the process which obtains the left ventricular volume for each time phase. The figure which shows the concept of the process which calculates the flow rate of the blood flowing into a left ventricle and the flow rate of the blood flowing out from a left ventricle for each cardiac phase. The figure explaining the processing concept which generates diagnostic support information from the volume of the left ventricle and the change of the left ventricle flow rate for each cardiac time phase. The figure explaining the processing concept which acquires the cardiac time phase information from the time change of the volume of the left ventricle and the time change of the flow rate. The figure explaining the processing concept of changing the direction of a slice cross section when it flows into the left ventricle and when it flows out.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(First Embodiment)
FIG. 1 is a block diagram showing the overall configuration of the magnetic resonance imaging apparatus 1 according to the first embodiment. The magnetic resonance imaging device 1 of the embodiment includes a magnet stand 100, a control cabinet 300, a console 400, a sleeper 500, and the like.

The magnet stand 100 and the sleeper 500 are usually arranged in a shield room. On the other hand, the control cabinet 300 is arranged in a room called a machine room, for example, and the console 400 is arranged in an operation room. The control cabinet 300 and the console 400 are collectively referred to as a scanner 600.

The magnet mount 100 includes a static magnetic field magnet 10, a gradient magnetic field coil 11, a WB (Whole Body) coil 12, and the like, and these components are housed in a cylindrical housing. The sleeper 500 has a sleeper main body 50 and a sleeper top plate 51. Further, the magnetic resonance imaging device 1 has an RF coil 20 arranged close to the subject. In the following description, the RF coil 20 will be described as one of the components of the magnetic resonance imaging device 1, but the RF coil 20 may not be included in the configuration of the magnetic resonance imaging device 1. In this case, although the RF coil 20 is not included in the configuration of the magnetic resonance imaging device 1, the RF coil 20 and the magnetic resonance imaging device 1 are configured to be connectable to each other. More specifically, the RF coil 20 and the bed top plate 51 of the magnetic resonance imaging device 1 are configured to be connectable to each other.

The control cabinet 300 includes a gradient magnetic field power supply 31 (31x for X-axis, 31y for Y-axis, 31z for Z-axis), an RF receiver 32, an RF transmitter 33, and a sequence controller 34.

The static magnetic field magnet 10 of the magnet mount 100 has a substantially cylindrical shape, and generates a static magnetic field in a bore (a space inside the cylinder of the static magnetic field magnet 10) which is an imaging region of a subject (for example, a patient). The static magnetic field magnet 10 has a built-in superconducting coil, and the superconducting coil is cooled to an extremely low temperature by liquid helium. The static magnetic field magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power supply (not shown) to the superconducting coil in the excitation mode, and then shifts to the permanent current mode to generate a static magnetic field power supply. Is separated. Once transitioned to the permanent current mode, the static magnetic field magnet 10 continues to generate a large static magnetic field for a long period of time, for example, one year or more. The static magnetic field magnet 10 may be configured as a permanent magnet.

The gradient magnetic field coil 11 also has a substantially cylindrical shape and is fixed inside the static magnetic field magnet 10. The gradient magnetic field coil 11 is composed of three gradient magnetic field coils for the X-axis, the Y-axis, and the Z-axis. Each gradient magnetic field coil is supplied with a gradient magnetic field current from a gradient magnetic field power source (31x, 31y, 31z) to generate a gradient magnetic field in the X-axis, Y-axis, and Z-axis directions and apply it to the subject.

The bed body 50 of the bed 500 can move the bed top plate 51 in the vertical direction and the horizontal direction, and moves the subject placed on the bed top plate 51 to a predetermined height before imaging. After that, at the time of photographing, the sleeper top plate 51 is moved in the horizontal direction to move the subject into the bore.

The WB coil 12 is fixed to the inside of the gradient magnetic field coil 11 in a substantially cylindrical shape so as to surround the subject. The WB coil 12 transmits an RF pulse transmitted from the RF transmitter 33 toward the subject, while receiving a magnetic resonance signal (that is, an MR signal) emitted from the subject by the excitation of hydrogen nuclei.

The RF coil 20 receives the MR signal emitted from the subject at a position close to the subject. The RF coil 20 includes, for example, a plurality of element coils. The RF coil 20 has various types such as for the head, for the chest, for the spine, for the lower limbs, or for the whole body, depending on the imaging site of the subject. Then, a plurality of RF coils 20 can be placed on the subject at the same time. FIG. 1 illustrates a state in which the RF coil 20 for the chest is placed.

The RF transmitter 33 transmits an RF pulse to the WB coil 12 based on the instruction from the sequence controller 34. The coil selection circuit 36 selects the MR signal received by the WB coil 12 or the MR signal received by the RF coil 20, and transmits the MR signal to the RF receiver 32. The RF receiver 32 detects the MR signal received by the WB coil 12 or the RF coil 20, digitizes the detected MR signal, and sends the raw data obtained by digitizing the detected MR signal to the sequence controller 34.

The sequence controller 34 scans the subject by driving the gradient magnetic field power supply 31, the RF transmitter 33, and the RF receiver 32, respectively, under the control of the console 400. Then, when the sequence controller 34 scans and receives the raw data from the RF receiver 32, the sequence controller 34 sends the raw data to the console 400.

The sequence controller 34 includes a processing circuit (not shown). This processing circuit is composed of, for example, a processor that executes a predetermined program and hardware such as an FPGA (Field Programmable Gate Array) and an ASIC (Application Specific Integrated Circuit).
The console 400 is configured as a computer having a processing circuit 40, a storage circuit 41, a display 42, and an input device 43.

The storage circuit 41 is a storage medium including an external storage device such as an HDD (Hard Disk Drive) or an optical disk device in addition to a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage circuit 41 stores various information and data, and also stores various programs executed by the processor included in the processing circuit 40.

The display 42 is a display device such as a liquid crystal display panel, a plasma display panel, or an organic EL panel. The input device 43 is, for example, a mouse, a keyboard, a trackball, a touch panel, or the like, and includes various devices for an operator to input various information and data.

The processing circuit 40 is, for example, a circuit including a CPU and a dedicated or general-purpose processor. The processor realizes various functions described later by executing various programs stored in the storage circuit 41. The processing circuit 40 may be configured by hardware such as FPGA (field programmable gate array) or ASIC (application specific integrated circuit). Various functions described later can also be realized by these hardware. Further, the processing circuit 40 can also realize various functions by combining software processing by a processor and a program and hardware processing.

With each of these components, the console 400 controls the entire magnetic resonance imaging device 1. The processing circuit 40 causes the sequence controller 34 to perform scanning based on the input imaging conditions, while reconstructing the image based on the raw data input from the sequence controller 34, that is, the digitized MR signal. The reconstructed image is displayed on the display 42 or stored in the storage circuit 41.

Before going into a more detailed description of the configuration and operation of the magnetic resonance imaging apparatus 1 of the embodiment, a brief description of the Pressure-Volume loop diagram conventionally used for diagnosing a heart disease is described, and the magnetism of the present embodiment is described. The Volume-Flow loop diagram used in the resonance imaging device 1 will be described.

As mentioned above, physiological changes that reflect interactions such as myocardial behavior, valve behavior in the heart, ventricular volume, and blood flow into and out of the ventricle are venticular-vascular interactions. ), Which is important information for understanding the pathophysiology of heart diseases such as valve abnormalities. As a conventional method for obtaining a ventricular vascular integration relationship, a Pressure-Volume loop diagram as an analysis result based on the measurement results of pressure (Pressure) and volume (Volume) of a ventricle (for example, the left ventricle) is known. The Pressure-Volume loop diagram is, for example, a diagram in which the pressure and volume of the left ventricle are plotted for one core cycle on the two-dimensional coordinates of volume on the horizontal axis and pressure on the vertical axis.

2 and 3 are diagrams illustrating the concept of the Pressure-Volume loop diagram. FIG. 2A is a diagram schematically showing the inside of the heart, and FIGS. 2B and 3A are diagrams showing an example of a Pressure-Volume loop diagram. Fresh blood drained from the left and right lungs is pumped from the left ventricle through the mitral valve to the left ventricle during diastole and from the left ventricle through the aortic valve to parts of the body during systole.

The Pressure-Volume loop diagram shown in FIGS. 2 (b) and 3 (a) shows the mutual relationship between pressure and volume in the left ventricle within one cycle of the heartbeat as a loop-shaped locus along the cardiac time phase. It is a representation figure.

The mitral valve closes at the time phase "A" on the Pressure-Volume loop diagram. At this time, the aortic valve is also closed. During the period from phase "A" to phase "B", the myocardium contracts around the left ventricle with both the mitral and aortic valves closed. Therefore, this period is a period of isovolumetric contraction in which the pressure in the ventricle increases while the volume of the ventricle is almost constant.

The aortic valve opens in phase "B". The mitral valve remains closed. During the period from phase "B" to phase "C", the myocardium of the left ventricle continues to contract, so that blood in the left ventricle is drained from the aortic valve and the volume of the left ventricle decreases. During this period, the pressure in the left ventricle remains almost high. In phase "C", most of the blood in the left ventricle is expelled from the vena cava valve. The period from time phase "A" to time phase "C" corresponds to systole.

The aortic valve closes at time phase "C". The mitral valve remains closed. During the period from phase "C" to phase "D", the myocardium relaxes around the left ventricle with both the aortic and mitral valves closed. Therefore, this period is a period of isotropic relaxation in which the pressure in the ventricle decreases while the volume of the ventricle is almost constant.

The mitral valve opens at the time phase "D". The aortic valve remains closed. During the period from time phase "D" to time phase "A", the left ventricle dilates with the mitral valve open. This causes blood to flow from the left atrium through the mitral valve into the left ventricle, increasing the volume of the left ventricle. During this period, the pressure in the left ventricle maintains a low value. The period from time phase "C" to time phase "A" corresponds to diastole.

By observing the Pressure-Volume loop diagram, it is possible to accurately grasp the pathophysiology of heart diseases such as valve abnormalities. For example, an abnormality in the mitral valve or aortic valve results in a decrease in the amount of blood flowing into the left ventricle or a decrease in the amount of blood flowing out of the left ventricle. As a result, the amount of blood exhaled from the left ventricle, that is, the cardiac output, is reduced. The decrease in cardiac output will be reflected in the Pressure-Volume loop diagram as a decrease in the width in the volume direction, and the shape of the Pressure-Volume loop diagram will change compared to normal. Therefore, the pathological condition of heart disease such as valve abnormality can be diagnosed from the shape of the Pressure-Volume loop diagram.

As described above, since the diagnosis using the Pressure-Volume loop diagram is useful, it is a method generally used in the past. However, although the volume of the ventricle can be obtained from a medical image such as an ultrasound image, a highly invasive examination performed by inserting a device such as a catheter into the heart is required to measure the pressure. It becomes.

Therefore, in the magnetic resonance imaging device 1 of the present embodiment, a flow rate that can be measured non-invasively is used instead of the conventional pressure as an index showing the ventricular vascular integration relationship. Then, in the magnetic resonance imaging apparatus 1 of the present embodiment, it is possible to generate a Volume-Flow loop diagram similar to the Pressure-Volume loop diagram by using the flow rate and the volume of the ventricle.

In the magnetic resonance imaging device 1 of the present embodiment, information on the morphology of the organ of the subject (first information) and a fluid input to / from the organ are input / output based on the magnetic resonance signal collected by imaging the subject. Information (second information) regarding the flow of the above is acquired at the same time and in a plurality of time phases. Here, the ventricle or the left ventricle is an example of an organ, and in addition to this, for example, a brain or a kidney can also be an example of an organ targeted by the present embodiment. Then, the volume of these organs can be information (first information) regarding the morphology of the organs.

In addition, the flow rate and speed of blood flowing into and out of the ventricle or the left ventricle, or the flow rate and speed of cerebrospinal fluid input and output to the brain are also information regarding the flow of fluid input and output to the organ (second information). Can be.

However, in the following, as an example of information on the morphology of the organ of the subject (first information), the volume of the left ventricle will be described as an example, and as an example of information on the flow of liquid input to and from the organ (second information). , The flow rate of blood input to and from the left ventricle will be described as an example.

FIG. 4 is a diagram showing the concepts of the left ventricular volume and the left ventricular flow rate acquired by the magnetic resonance imaging apparatus 1 of the present embodiment. As shown in FIG. 4A, the magnetic resonance imaging apparatus 1 collects MR signals by non-invasively imaging the heart for each cardiac phase, and based on the collected MR signals, the volume of the left ventricle. Then, the flow rate of blood flowing into the left ventricle and the flow rate of blood flowing out of the left ventricle are calculated for each cardiac phase.

Here, the unit of volume of the left ventricle is customarily expressed in mL (milliliter). The flow rate of blood in the left ventricle is the sum of the amount of blood flowing into the left ventricle through the mitral valve per unit time and the amount of blood flowing out of the left ventricle through the aortic valve per unit time. Yes, the unit is, for example, mL / s (milliliter / sec). In the following, the sign of the flow rate of blood flowing into the left ventricle is represented by a plus, and the sign of the flow rate of blood flowing out of the left ventricle is represented by a minus. good.

The upper part of FIG. 4B schematically shows the time change of the left ventricular volume, and the middle part of FIG. 4B schematically shows the time change of the left ventricular flow rate for one cycle of the cardiac time phase. The lower part of FIG. 4B shows, for example, a typical time change of an electrocardiographic waveform measured by an electrocardiograph in association with the time axis of a graph of left ventricular volume and left ventricular flow rate. be.

The period from time phase "A" to time phase "C" corresponds to systole. During this period, the myocardium around the left ventricle contracts. The mitral valve is closed in the time phase "A", and both the mitral valve and the aortic valve are closed from the time phase "A" to the time phase "B". Therefore, during this period, the volume of the left ventricle becomes almost constant near the maximum value, and the flow rate of the left ventricle becomes almost zero. On the other hand, the aortic valve opens in the time phase "B". As a result, blood in the left ventricle drains from the aortic valve. Therefore, as the volume of the left ventricle decreases, the flow rate of the left ventricle changes significantly to the negative side.

The period from time phase "C" to time phase "A" corresponds to diastole. During this period, the myocardium around the left ventricle relaxes. The aortic valve is closed in the time phase "C", and both the mitral valve and the aortic valve are closed from the time phase "C" to the time phase "D". Therefore, during this period, the volume of the left ventricle becomes almost constant near the minimum value, and the flow rate of the left ventricle becomes almost zero. The mitral valve opens at the time phase "D". As a result, blood flows from the left atrium into the left ventricle through the mitral valve. Therefore, as the volume of the left ventricle increases, the flow rate of the left ventricle changes to the positive side.

The magnetic resonance imaging apparatus 1 of the present embodiment collects MR signals by continuously imaging a subject in a plurality of time phases, and from the collected MR signals, an example is shown in the upper and middle stages of FIG. 4 (b). The left ventricular volume and the left ventricular flow rate are obtained for each phase.

The time variation of the left ventricular volume and the left ventricular flow rate shown in FIG. 4 (b) reflects the interaction of the behavior of the myocardium, the behavior of the valve in the heart, the volume of the ventricle, the flow rate of blood flowing into and out of the ventricle, and the like. It indicates a physiological change, and as described above, it is also called a venticular-vascular interaction.

On the other hand, it is also possible to generate a Volume-Flow loop diagram as shown in FIG. 5 from the time change of the left ventricular volume and the left ventricular flow rate. In the Volume-Flow loop diagram, one axis (for example, X-axis) is represented by the left ventricular volume, and the other axis (for example, Y-axis) is represented by the left ventricular flow rate. The time variation of the left ventricular flow rate is plotted along the flow of the time phase.

The Volume-Flow loop diagram makes it possible to more accurately grasp the ventricular and vascular integration relationship, and thus it is possible to provide useful diagnostic support information. For example, as illustrated in FIG. 5 (b), the volume-flow loop diagram of a normal subject and the volume-flow loop diagram of a subject having a heart disease are clearly different. For example, in a subject suffering from mitral valve stenosis (MS: Mitral Stenosis) or aortic valve stenosis (AS: Aorta Stenosis), the Stroke Volume decreases, so that in one cardiac cycle. The difference between the maximum and minimum values of the left ventricular volume becomes small. In other words, the width of the Volume-Flow loop diagram in the volume axis direction becomes smaller. Further, in mitral valve stenosis and aortic valve stenosis, the positions of the centers of gravity of the loops in the Volume-Flow loop diagram are different from each other as illustrated in FIG. 5 (b).

In this way, since the volume-flow loop diagram reflects the physiological changes in the heart, it is possible to estimate not only the presence or absence of heart disease but also the type of heart disease from the shape of the volume-flow loop diagram. be.

FIG. 6 is a diagram showing a detailed configuration of the magnetic resonance imaging apparatus 1 according to the present embodiment, and particularly focuses on the above-mentioned left ventricular volume, left ventricular flow rate, and function of generating a Volume-Flow loop diagram. It is a block diagram which shows the function configuration example. Further, FIG. 7 is an overall flowchart showing an operation example of the magnetic resonance imaging device 1 focusing on the left ventricular volume, the left ventricular flow rate, and the function of generating the Volume-Flow loop diagram.

As shown in FIG. 6, the processing circuit 40 of the console 400 includes a multi-slice / multi-time phase image generation function 402 including an imaging condition setting function 401, a morphological image generation function 403, and a velocity image generation function 404, and an organ volume (left ventricle). Volume) calculation function 405, flow rate calculation function 406, and analysis function 407 are realized. Each of these functions is realized, for example, by the processor included in the processing circuit 40 executing a predetermined program stored in the storage circuit 41. The operation of each of these functions will be described with reference to the overall flowchart of FIG. 7 and the operation explanatory diagrams of FIGS. 8 to 13.

First, in step ST100 of FIG. 7, the imaging conditions are set. The processing of step ST100 is performed by the imaging condition setting function 401 of FIG. The pulse sequence included in the imaging conditions set in step ST100 is a pulse sequence that collects MR signals from a plurality of slices, and is preferably a pulse sequence that simultaneously collects MR signals from a plurality of slices from the viewpoint of high-speed data collection. That is, it is a pulse sequence that enables simultaneous multi-slice collection.

Further, the imaging conditions set in step ST100 are simultaneous multi-slice collection and multi-time phase collection in which MR signals are continuously collected over a plurality of core time phases. Further, the pulse sequence included in the imaging conditions set in step ST100 includes first information regarding the morphology of the organ of the subject, for example, second information regarding the volume of the left ventricle and the flow of liquid input to and from the organ of the subject. For example, it is a pulse sequence that can simultaneously collect the left ventricular flow rate.

FIG. 8 is a diagram illustrating the concept of simultaneous multi-slice collection performed by the magnetic resonance imaging apparatus 1 of the present embodiment. In the imaging conditions set in step ST100, a plurality of slices are set as the imaging cross section so as to cover a part of the left atrium of the subject and a three-dimensional space including the entire left ventricle. For example, as illustrated in FIG. 8, a plurality of slice cross sections orthogonal to the axis (so-called left ventricular long axis) connecting the center of the mitral valve and the apex of the heart (the tip of the left ventricle) are set.

At least one of the slice sections is set near the mitral valve, which is the inlet of blood to the left ventricle, and the aortic valve, which is the outlet of blood from the left ventricle. In the example shown in FIG. 8, the slice cross section _SLA corresponds to this. The slice cross section SL _A is a slice cross section set for measuring the left ventricular flow rate. _As will be described later, a morphological image and a velocity image are generated from the MR signal collected from the slice cross section SLA. Then, from the morphological image and velocity image of the slice cross section _SLA , the left ventricular flow rate flowing into the left ventricle through the mitral valve and the left ventricular flow rate flowing out from the left ventricle through the aortic valve are calculated.

The other slice sections are set to generally cover the left ventricle. In the example shown in FIG. 8, three slice cross sections SL _B 1, SL _B 2, and SL _B 3 correspond to this. As will be described later, a morphological image of each slice cross section is generated from MR signals collected from the slice cross sections SL _B 1, SL _B 2, and SL _B 3, and the volume of the left ventricle is calculated.

FIG. 9 is an example of a PSD (Pulse Sequence Diagram) showing an example of a pulse sequence used in the magnetic resonance imaging apparatus 1 of the present embodiment. The pulse sequence exemplified in FIG. 9 is a high-speed GRE (Gradient Echo) system pulse sequence accompanied by a phase contrast (PC: Phase Contrast) method. The pulse sequence illustrated in FIG. 9 is also a pulse sequence based on a multi-band excitation method that simultaneously excites a plurality of slice sections of an organ by exciting the organ with an excitation pulse in which a plurality of frequency components are mixed.

The first stage of the PSD shown in FIG. 9 shows an RF pulse. In the second stage, the gradient magnetic field _GSS for slice selection is shown, and the gradient magnetic field of the positive electrode bipolar pulse PC (+) and the gradient magnetic field of the negative electrode bipolar pulse PC (−) for phase contrast are shown. The bipolar pulse PC (+) and PC (−) of the positive electrode and the negative electrode are applied in the same direction as the gradient magnetic field _GSS for slice selection.

The gradient magnetic field _GPE for phase encoding is shown in the third stage of the PSD. The phase encoding amount applied immediately after the positive electrode bipolar pulse PC (+) and the phase encoding amount applied immediately after the negative electrode bipolar pulse PC (−) are set to the same value. The fourth stage of the PSD shows the lead-out gradient magnetic field _Gro , and the fifth stage shows the MR signal read by the lead-out gradient magnetic field _Gro .

The MR signal corresponding to one phase encoding amount is collected by the portion surrounded by the broken line of the square. A velocity image and a morphological image can be generated by using 2N MR signals from the phase encoding (1) to the phase encoding (N).

For example, a first phase image generated by reconstructing N MR signals corresponding to the positive electrode bipolar pulse PC (+) and N MR signals corresponding to the negative electrode bipolar pulse PC (-) are displayed. A velocity image can be generated by differentiating from the second phase image generated by reconstruction. Further, a morphological image can be generated from an amplitude image generated by reconstructing N MR signals corresponding to a bipolar pulse of either a positive electrode or a negative electrode.

Further, as shown in the uppermost stage of FIG. 9, the pulse sequence from the phase encode (1) to the phase encode (N) is performed a plurality of times within one cardiac cycle (for example, the period between the R wave and the next R wave). By repeating, velocity images and morphological images over a plurality of cardiac time phases can be generated over time (that is, along the time phase).

Further, in the magnetic resonance imaging apparatus 1 of the present embodiment, the excitation pulse is a single pulse from phase encoding (1) to phase encoding (N) by using a multi-band excitation pulse in which a plurality of frequency components are mixed. By applying the sequence, it is possible to generate a velocity image and a morphological image of a plurality of slice cross sections.

FIG. 10 is an operation conceptual diagram showing that a plurality of slice cross sections are excited by a multi-band excitation pulse. For example, as shown in the lower left part of FIG. 10, by synthesizing the excitation pulses having four center frequencies f1 to f4, the multiband excitation pulse shown in the upper left part of FIG. 10 is generated. By applying such a multi-band excitation pulse together with the slice selective magnetic field _GSS to the organ of the subject, for example, the region including the left ventricle, the application direction of the slice selective magnetic field _GSS as shown in the right part of FIG. A plurality of slice cross sections orthogonal to (for example, four slice cross sections from the slice cross section SL1 to the slice cross section SL4) can be excited at the same time.

MR signals collected from a plurality of slice sections excited at the same time are separated into signals of each slice section by using a parallel imaging algorithm such as the SENSE (Sensitivity encoding) method.

Returning to FIG. 7, in step ST102 of FIG. 7, the subject is imaged under the imaging conditions including the pulse sequence described above, and MR signals are collected for each cardiac phase over a plurality of cardiac phases. Further, in step ST104, a morphological image is generated in each slice cross section of the left ventricle for each cardiac time phase based on the collected MR signal.

Further, in step ST106, the volume of the left ventricle is calculated for each cardiac phase from a plurality of morphological images of the left ventricle. The process of step ST106 is a process performed by the morphological image generation function 403 and the organ volume (left ventricular volume) calculation function 405 of FIG.

FIG. 11 is a diagram showing the concept of a process for obtaining the left ventricular volume for each time phase (process corresponding to step ST104 and step ST106 in FIG. 7). Left ventricular volume is calculated using morphological images of multiple slice cross sections set to cover almost the entire area of the left ventricle.

The number of slice cross sections is not particularly limited, but for example, as illustrated in the left figure of FIG. 11, three slice cross sections of slice cross section SL _B 1, slice cross section SL _B 2, and slice cross section SL _B 3 are shown. Generates a morphological image of. As shown in the upper right part of FIG. 11, these morphological images are generated along a plurality of cardiac time phases, for example, from the time phase (1) to the time phase (N).

In the morphological image of each slice cross section, a short axis cross section of the left ventricle (an axis connecting the center of the mitral valve and the apex of the heart, that is, a cross section orthogonal to the long axis of the left ventricle) is depicted. Therefore, from the morphological image of each slice cross section, the area of the short axis cross section of the left ventricle (S1 (n), S2 (n), S3 (n)) is set for each time phase (n) (n = 1 to N). Can be calculated.

On the other hand, since the distance in the long axis direction of the left ventricle of each slice cross section is known depending on the imaging conditions to be set, the volume of the left ventricle (from the area of each short axis cross section of the left ventricle and the distance of each short axis cross section, Volume) can be calculated. The figure shown in the lower right part of FIG. 11 schematically shows the change of the left ventricular volume calculated as described above along the time phase.

Returning to FIG. 7, in step ST108, a morphological image and a velocity image of the slice cross section in the vicinity of the inlet and outlet to the left ventricle are generated. Then, the flow rate of blood flowing into the left ventricle and the flow rate of blood flowing out of the left ventricle are calculated for each cardiac phase. The process of step ST108 is a process performed by the velocity image generation function 404 and the flow rate calculation function 406 of FIG.
The morphological image generation function 403 and the speed image generation function 404 are functions included in the multi-slice / multi-time phase image generation function 402.

FIG. 12 is a diagram illustrating the processing concept of step ST108. Based on the MR signal collected from the slice cross section _SLA set near the mitral valve and the aortic valve, the velocity image _SLA and the morphological image _SLA are displayed for each cardiac phase (for example, as shown in the upper right part of FIG. 12). , For each cardiac time phase from time phase (1) to time phase (N)).

In the velocity image _SLA , the magnitude of the velocity of blood flowing into and out of the left ventricle through the mitral valve or the aortic valve is visualized as a pixel value. The velocity of the blood depicted in the velocity image _SLA is a value obtained by the phase contrast method, and the spatial distribution of the velocity components in the direction orthogonal to the slice cross section is obtained with positive and negative signs. For example, in each velocity image for each phase, the velocity component of the blood flowing into the left ventricle through the mitral valve is a positive velocity spatial distribution, and the blood flowing out of the left ventricle through the aortic valve. The velocity component is depicted as a spatial distribution of negative velocities.

On the other hand, in each morphological image _SLA , the shape of the mitral valve or the aortic valve that changes with each phase is depicted. Further, in step ST108, the diameter area of the mitral valve or the aortic valve is obtained for each time phase from the shape of the mitral valve or the aortic valve in the morphological image _SLA , and the diameter area of the mitral valve and the blood passing through the mitral valve are obtained. The flow rate of blood flowing into the left ventricle through the mitral valve is calculated for each phase by the product of the velocity (or the spatial distribution of the velocity and the integration of the radial area). Similarly, the flow of blood flowing out of the left ventricle through the aortic valve by the product of the diameter area of the aortic valve and the velocity of blood passing through the aortic valve (or the spatial distribution of velocity and the integration of the radial area). Is calculated for each time phase. The figure shown in the lower right part of FIG. 12 schematically shows the change of the left ventricular flow rate calculated as described above along the time phase.

Returning to FIG. 7, in step ST110, diagnostic support information is generated from the changes in the volume of the left ventricle and the flow rate of blood flowing into and out of the left ventricle for each cardiac phase. .. For example, as diagnostic support information, the volume-flow loop diagram described above is generated from the changes in the volume and flow rate of the left ventricle for each cardiac phase. The processing of step ST110 is performed by the analysis function 407 of FIG.

FIG. 13 is a diagram showing a processing concept of step ST110. As mentioned above, in the Volume-Flow loop diagram, one cycle of the heartbeat is set in two-dimensional coordinates in which one axis (for example, the X axis) is represented by the left ventricular volume and the other axis (for example, the Y axis) is represented by the left ventricular flow rate. It is a plot of the time change of the left ventricular volume and the left ventricular flow rate in the time phase flow. Volume by plotting the volume of the left ventricle calculated in step ST106 and the flow rate of the left ventricle calculated in step ST108 in the above two-dimensional coordinates along the flow of the time phase. -Flow loop diagram is generated.

As illustrated in the right figure of FIG. 13, it is known that the shape of the Volume-Flow loop diagram differs between a normal heart without heart disease and an abnormal heart with heart disease. Further, as described above, depending on the type of heart disease, for example, depending on the type of heart disease such as mitral valve stenosis (MS: Mitral Stenosis) and aortic valve stenosis (AS: Aorta Stenosis), Volume-Flow loop. It is also known that the shape of the diagram is different.

In step ST112 of FIG. 7, the diagnostic support information generated in step ST110 is displayed on the display 42. The above-mentioned Volume-Flow loop diagram (figure exemplified in FIG. 13B) may be displayed as diagnostic support information, replaced with the Volume-Flow loop diagram, or in addition to the Volume-Flow loop diagram. , A diagram showing a time change of the volume of the left ventricle and a time change of the flow rate of the left ventricle (a diagram exemplified in FIG. 13A) may be displayed as diagnostic support information.

The Volume-Flow loop diagram and information on the temporal changes in the volume and flow rate of the left ventricle are information on interactions derived from biological information such as ventricular vascular integration, and are useful for diagnosing heart disease. This is useful information. Since the magnetic resonance imaging device 1 of the present embodiment can acquire such information non-invasively, it provides a heart disease test with less burden on the patient as compared with the conventional invasive method using a catheter or the like. be able to.

(Other embodiments)
FIG. 14 is a diagram illustrating a first example of another embodiment. Up to this point, users such as doctors have generated a Volume-Flow loop diagram from changes in the volume and flow rate of the left ventricle over time, and displayed the generated Volume-Flow loop diagram on the display 42. We have described embodiments that can provide useful diagnostic support information.

On the other hand, useful information other than the Volume-Flow loop diagram can be generated from the time change of the volume and the flow rate of the left ventricle. The volume and flow rate of the left ventricle reflect the physiological changes caused by the interaction between the behavior of the myocardium and the valve in the heart and the flow rate of blood flowing into and out of the ventricle. Is. Therefore, as shown in the upper part of FIG. 14B, the cardiac time phase information can be acquired from the time change of the volume of the left ventricle and the time change of the flow rate. For example, to obtain the transition time from systole to diastole or the transition time from diastole to systole with high accuracy from the time change of volume of the left ventricle and the time change of flow. In addition, it is possible to obtain more detailed changes in the cardiac time phase inside each of systole and diastole.

Further, it is also possible to generate a synchronization signal used for electrocardiographic synchronization imaging based on the acquired cardiac time phase information. According to this method, since the synchronization signal can be obtained without using an electrocardiograph, it is not necessary to attach an electrode to the patient, and the burden on the patient can be reduced. Further, noise caused by the application of the RF pulse or the gradient magnetic field of the magnetic resonance imaging device 1 does not overlap with the electrode or the cable extending from the electrode. Therefore, it is possible to generate a highly accurate synchronization signal that is not affected by noise at a desired timing in the cardiac phase.

FIG. 15 is a diagram illustrating a second example of another embodiment. In the above-described embodiment, the velocity image and the morphological image are generated from a plurality of slice cross sections set in the same orientation. For example, the orientation of the plurality of slice sections was set by having the plurality of slice sections orthogonal to the axis connecting the center of the mitral valve and the apex of the heart. According to this setting, the direction of the velocity of the blood flowing into the left ventricle through the mitral valve is substantially the same as the application direction of the bipolar pulse PC (+) and PC (−) in the phase contrast method. Therefore, the velocity of blood flowing into the left ventricle through the mitral valve can be accurately measured.

However, the direction of the velocity of blood flowing out of the left ventricle through the aortic valve does not match the direction of application of the bipolar pulse PC (+) and PC (-). Therefore, the rate of blood flowing out of the left ventricle through the aortic valve may be measured lower than the actual rate.

Therefore, in the second example of the other embodiment, as illustrated in FIGS. 15 (a) and 15 (b), in the first cardiac cycle, the orientation of each slice cross section is set to the center of the mitral valve and the apex of the heart. Set in the direction orthogonal to the axis connecting the parts (slice direction (α)), and calculate the flow rate of blood flowing into the left ventricle through the mitral valve from the velocity image and morphological image of the slice cross section _SLA .

On the other hand, in the second cardiac cycle, the orientation of each slice cross section is set in the direction orthogonal to the axis connecting the center of the aortic valve and the apex of the heart (slice direction (β)), and the speed image of the slice cross section _SLA is set. From the morphological image, the flow rate of blood flowing out of the left ventricle through the aortic valve is calculated.

As described above, when measuring the flow rate of blood flowing into the left ventricle and when measuring the flow rate of blood flowing out of the left ventricle, the blood flowing into the left ventricle can be obtained by changing the direction of the slice cross section. , Both flow rates of blood flowing out of the left ventricle can be accurately measured.

According to at least one embodiment described above, information on interactions derived from biological information such as ventricular vascular integration relationships can be generated by a non-invasive method based on a magnetic resonance signal.

The scanner in the description of the embodiment is an example of the image pickup unit in the description of the claims. Further, the imaging condition setting function in the description of the embodiment is an example of the setting unit in the description of the claims. Further, in the description of the embodiment, the scanner, the imaging condition setting function, the multi-slice / multi-time phase image generation function, the morphological image generation function, the velocity image generation function, the organ volume (left ventricle volume) calculation function, and the flow rate calculation function. Is an example of the acquisition unit in the description of the scope of claims. Further, the analysis function in the description of the embodiment is an example of the analysis unit in the description of the claims.

Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 Magnetic resonance imaging device 12 WB coil 20 RF coil 34 Sequence controller 40 Processing circuit 42 Display 401 Imaging condition setting function 402 Multi-slice / multi-time phase image generation function 403 Morphological image generation function 404 Speed image generation function 405 Organ volume (left ventricle) Volume) Calculation function 406 Flow rate calculation function 407 Analysis function

Claims (14)

Based on the magnetic resonance signal collected by imaging the subject, the first information regarding the morphology of the organ of the subject and the second information regarding the flow of the fluid input / output to the organ can be simultaneously and plurally used. The acquisition part to be acquired in the time phase of
An analysis unit that uses the first information and the second information to generate diagnostic support information indicating the interaction between the first information and the second information.
A magnetic resonance imaging device. The acquisition unit
A setting unit for setting imaging conditions for acquiring the first information and the second information at the same time and in a plurality of time phases.
An imaging unit that images the subject according to the set imaging conditions and collects the magnetic resonance signal.
To prepare
The magnetic resonance imaging apparatus according to claim 1. The setting unit sets a pulse sequence capable of collecting the magnetic resonance signal from a plurality of slice cross sections of the organ, and can detect the velocity of the fluid input / output to / from the organ.
The imaging unit applies the set pulse sequence to the subject and collects the magnetic resonance signal.
The magnetic resonance imaging apparatus according to claim 2. The pulse sequence is based on a phase contrast method that detects the velocity of a fluid.
The magnetic resonance imaging apparatus according to claim 3. The pulse sequence is based on a multi-band excitation method that simultaneously excites a plurality of slice sections of the organ by exciting the organ with an excitation pulse in which a plurality of frequency components are mixed, and detects the fluid velocity. Based on the phase contrast method,
The magnetic resonance imaging apparatus according to claim 3. The pulse sequence is a high-speed GRE system.
The magnetic resonance imaging apparatus according to any one of claims 3 to 5. The acquisition unit acquires the volume inside the organ as the first information, and at least one of the flow rate of the fluid flowing into the inside of the organ and the flow rate of the fluid flowing out from the inside of the organ is used as the second information. get,
The magnetic resonance imaging apparatus according to claim 1 or 2. The acquisition unit
The volume of the organ was calculated based on the morphological images of the cross sections of the plurality of slices of the organ.
The flow rate of the fluid flowing into the inside of the organ is calculated from the inflow area obtained from the morphological image of the slice cross section near the inlet to the inside of the organ and the velocity obtained from the velocity image of the slice cross section near the inflow. Calculate and
The flow rate of the fluid flowing out from the inside of the organ is calculated from the outlet area obtained from the morphological image of the slice cross section near the outlet and the velocity obtained from the velocity image of the slice cross section near the outlet. calculate,
The magnetic resonance imaging apparatus according to any one of claims 3 to 6. The volume and the flow rate are calculated for each of a plurality of time phases.
The magnetic resonance imaging apparatus according to claim 8. The analysis unit generates the diagnosis support information by associating the first information with the second information acquired at the same time as the acquisition time of the first information for each of a plurality of time phases.
The magnetic resonance imaging apparatus according to any one of claims 1 to 9. The analysis unit plots the calculated volume and the calculated flow rate in two-dimensional coordinates where one axis is the volume and the other axis is the flow rate along a plurality of time phases. Generate a Flow loop diagram,
The magnetic resonance imaging apparatus according to any one of claims 7 to 9. The organ is the heart and the fluid is the blood that enters and exits the heart.
The magnetic resonance imaging apparatus according to any one of claims 1 to 11. The organ is the heart and the fluid is the blood that enters and exits the heart.
The analysis unit sequentially calculates the volume and the flow rate in chronological order, and acquires information on the cardiac time phase based on at least one of the calculated data of the volume and the flow rate.
The magnetic resonance imaging apparatus according to any one of claims 7 to 9. The organ is the heart and the fluid is the blood that enters and exits the heart.
The analysis unit sequentially calculates the volume and the flow rate in chronological order, and generates a synchronization signal necessary for electrocardiographic synchronization imaging based on at least one of the calculated data of the volume and the flow rate.
The magnetic resonance imaging apparatus according to any one of claims 7 to 9.

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