JP7668115B2 - Magnetic resonance imaging device and program - Google Patents

Description

The embodiments disclosed in this specification and the drawings relate to a magnetic resonance imaging device and a program.

Conventionally, in a magnetic resonance imaging (MRI) device, positioning imaging (hereinafter referred to as preparatory imaging) is performed to determine the imaging area before imaging of a diagnostic image of a subject (hereinafter referred to as main imaging). In addition, in order to reduce the effects of tissue movement due to breathing, breath-hold imaging may be performed during preparatory imaging and main imaging, in which imaging is performed while the patient holds their breath. For example, because the lungs and liver move several centimeters with each breath, breath-hold imaging may be performed when performing an abdominal examination.

However, if the subject's breath-holding timing differs between the planned and actual imaging, there is a risk that the desired image will not be obtained due to differences in tissue position during the actual imaging compared to the planned imaging.

JP 2019-213860 A

One of the problems that the embodiments disclosed in this specification and the drawings attempt to solve is correcting positional deviations during breath-hold imaging. However, the problems that the embodiments disclosed in this specification and the drawings attempt to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems.

The magnetic resonance imaging apparatus according to the embodiment includes a first detection unit, an acquisition unit, a second detection unit, and a correction unit. The first detection unit detects a reference part serving as an index of the imaging position from a positioning image for determining the imaging position of the actual imaging. The acquisition unit acquires the relative positional relationship between the imaging position and the reference part. After capturing the positioning image, the second detection unit detects the position of the reference part from a linear partial image including the reference part captured prior to the actual imaging. The correction unit corrects the imaging position during the actual imaging based on the relative positional relationship between the imaging position and the reference part acquired by the acquisition unit and the positional relationship of the reference parts detected by the first detection unit and the second detection unit.

FIG. 1 is a block diagram showing an example of a magnetic resonance imaging apparatus according to an embodiment. FIG. 2 is a diagram showing an example of a positioning image in which a reference part and a first imaging region imaged by the magnetic resonance imaging apparatus according to the embodiment are depicted. FIG. 3 is a diagram showing an example of a positioning image in which a second imaging region imaged by the magnetic resonance imaging apparatus according to the embodiment is depicted. FIG. 4 is a diagram showing an example of the upper edge of the liver detected on a line profile imaged by the magnetic resonance imaging apparatus according to the embodiment. FIG. 5 is a flowchart illustrating an example of processing executed by the magnetic resonance imaging apparatus according to the embodiment.

Below, an embodiment of a magnetic resonance imaging apparatus and a program will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of a magnetic resonance imaging (MRI) device 100 according to an embodiment. As shown in FIG. 1, the magnetic resonance imaging device 100 includes a static magnetic field magnet 101, a static magnetic field power supply (not shown), a gradient magnetic field coil 103, a gradient magnetic field power supply 104, a bed 105, a bed control circuit 106, a transmission coil 107, a transmission circuit 108, a reception coil 109, a reception circuit 110, a sequence control circuit 120, and a computer system 130.

Note that the configuration shown in FIG. 1 is merely an example. For example, the sequence control circuit 120 and each part in the computer system 130 may be configured as appropriate to be integrated or separated. In addition, the magnetic resonance imaging apparatus 100 does not include a subject P (e.g., a human body).

The X-axis, Y-axis, and Z-axis shown in FIG. 1 constitute an apparatus coordinate system specific to the magnetic resonance imaging apparatus 100. For example, the Z-axis direction coincides with the axial direction of the cylinder of the gradient coil 103 and is set along the magnetic flux of the static magnetic field generated by the static magnetic field magnet 101.

The Z-axis direction is the same as the longitudinal direction of the bed 105, and is also the same as the head-to-tail direction of the subject P placed on the bed 105. The X-axis direction is set along the horizontal direction perpendicular to the Z-axis direction. The Y-axis direction is set along the vertical direction perpendicular to the Z-axis direction.

The static magnetic field magnet 101 is a magnet formed in a hollow, approximately cylindrical shape, and generates a static magnetic field in the internal space. The static magnetic field magnet 101 is, for example, a superconducting magnet, and is excited by receiving a current from a static magnetic field power supply.

The static magnetic field power supply supplies a current to the static magnetic field magnet 101. As another example, the static magnetic field magnet 101 may be a permanent magnet, in which case the magnetic resonance imaging apparatus 100 may not include a static magnetic field power supply. Also, the static magnetic field power supply may be provided separately from the magnetic resonance imaging apparatus 100.

The gradient magnetic field coil 103 is a hollow coil formed in a roughly cylindrical shape, and is disposed inside the static magnetic field magnet 101. The gradient magnetic field coil 103 is formed by combining three coils corresponding to the mutually orthogonal X, Y, and Z axes.

These three coils are individually supplied with current from the gradient magnetic field power supply 104 to generate gradient magnetic fields whose magnetic field strength changes along the X, Y, and Z axes. The gradient magnetic field power supply 104 also supplies current to the gradient magnetic field coil 103 under the control of the sequence control circuit 120.

The bed 105 includes a top plate 105a on which the subject P is placed, and under the control of the bed control circuit 106, the top plate 105a is inserted into the imaging port with the subject P, such as a patient, placed on it. Under the control of the computer system 130, the bed control circuit 106 drives the bed 105 to move the top plate 105a in the longitudinal direction and the vertical direction.

The transmitting coil 107 excites any region of the subject P by applying a high-frequency magnetic field. The transmitting coil 107 is, for example, a whole-body type coil that surrounds the entire body of the subject P. The transmitting coil 107 receives an RF pulse from the transmitting circuit 108, generates a high-frequency magnetic field, and applies the high-frequency magnetic field to the subject P. The transmitting circuit 108 supplies an RF pulse to the transmitting coil 107 under the control of the sequence control circuit 120.

The receiving coil 109 is disposed inside the gradient coil 103 and receives magnetic resonance signals (hereinafter referred to as MR (Magnetic Resonance) signals) emitted from the subject P due to the influence of a high-frequency magnetic field. When the receiving coil 109 receives an MR signal, it outputs the received MR signal to the receiving circuit 110.

In FIG. 1, the receiving coil 109 is configured to be provided separately from the transmitting coil 107, but this is only an example and is not limited to this configuration. For example, a configuration in which the receiving coil 109 also serves as the transmitting coil 107 may be adopted.

The receiving circuit 110 performs analog-to-digital (AD) conversion on the analog MR signal output from the receiving coil 109 to generate MR data. The receiving circuit 110 also transmits the generated MR data to the sequence control circuit 120. Note that the AD conversion may be performed within the receiving coil 109. The receiving circuit 110 is also capable of performing any signal processing other than AD conversion.

The sequence control circuit 120 drives the gradient magnetic field power supply 104, the transmission circuit 108, and the reception circuit 110 based on sequence information transmitted from the computer system 130 to image the subject P. Here, the sequence information is information that defines the procedure for performing imaging.

The sequence information defines the strength of the current supplied by the gradient magnetic field power supply 104 to the gradient magnetic field coil 103 and the timing of supplying the current, the strength of the RF pulse supplied by the transmission circuit 108 to the transmission coil 107 and the timing of applying the RF pulse, and the timing of detecting the MR signal by the reception circuit 110. The sequence information differs depending on the range of the area of the body of the subject P to be imaged.

The sequence control circuit 120 may be implemented by a processor or may be implemented by a combination of software and hardware.

Furthermore, when the sequence control circuit 120 drives the gradient magnetic field power supply 104, the transmission circuit 108, and the reception circuit 110 to image the subject P, and receives MR data from the reception circuit 110, it transfers the received MR data to the computer system 130.

The computer system 130 performs overall control of the magnetic resonance imaging apparatus 100 and generates MR images. As shown in FIG. 1, the computer system 130 includes a network interface 131, a memory circuit 132, a processing circuit 135, an input interface 133, and a display 134.

The NW interface 131 communicates with the sequence control circuit 120 and the bed control circuit 106. For example, the NW interface 131 transmits sequence information to the sequence control circuit 120. The NW interface 131 also receives MR data from the sequence control circuit 120.

The memory circuitry 132 stores various types of information. For example, the memory circuitry 132 stores MR data received by the NW interface 131, k-space data arranged in k-space by the processing circuitry 135 described below, and image data generated by the processing circuitry 135. The memory circuitry 132 also stores, for example, the relative positional relationship between a reference part and the first imaging region described below.

The memory circuit 132 is, for example, a semiconductor memory element such as a random access memory (RAM), a flash memory, a hard disk, or an optical disk.

The input interface 133 accepts various instructions and information input from the operator. The input interface 133 can be realized, for example, by a trackball, a switch button, a mouse, a keyboard, a touchpad that performs input operations by touching the operation surface, a touchscreen that integrates a display screen and a touchpad, a non-contact input circuit that uses an optical sensor, and a voice input circuit.

The input interface is connected to the processing circuit 135, converts input operations received from the operator into electrical signals, and outputs the electrical signals to the processing circuit 135. Note that in this specification, the input interface is not limited to those equipped with physical operating parts such as a mouse and keyboard.

For example, an example of an input interface also includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the computer system 130 and outputs this electrical signal to a control circuit.

Under the control of the processing circuitry 135, the display 134 displays a GUI (Graphical User Interface) for accepting input of imaging conditions, magnetic resonance images generated by the processing circuitry 135, and the like. The display 134 is, for example, a display device such as a liquid crystal display.

The processing circuitry 135 performs overall control of the magnetic resonance imaging apparatus 100. In more detail, the processing circuitry 135 includes, as an example, an imaging processing function 135a, a determination function 135b, a detection function 135c, an acquisition function 135d, a display control function 135e, and a correction function 135f.

The determination function 135b is an example of a determination unit. The detection function 135c is an example of a first detection unit. The detection function 135c is also an example of a second detection unit. The acquisition function 135d is an example of an acquisition unit. The correction function 135f is an example of a correction unit.

Here, for example, each of the processing functions of the processing circuit 135, that is, the imaging processing function 135a, the determination function 135b, the detection function 135c, the acquisition function 135d, the display control function 135e, and the correction function 135f, is stored in the memory circuit 132 in the form of a program executable by a computer. The processing circuit 135 is a processor.

For example, the processing circuitry 135 realizes the functions corresponding to each program by reading the programs from the storage circuitry 132 and executing them. In other words, after each program has been read, the processing circuitry 135 has the functions shown in the processing circuitry 135 of FIG. 1.

In FIG. 1, the processing functions performed by the image capture function 135a, the determination function 135b, the detection function 135c, the acquisition function 135d, the display control function 135e, and the correction function 135f are described as being realized by a single processor, but the processing circuit 135 may be configured by combining multiple independent processors, and each processor may execute a program to realize the functions.

In addition, in FIG. 1, a single memory circuit 132 is described as storing a program corresponding to each processing function, but multiple memory circuits may be distributed and the processing circuit 135 may read out the corresponding program from each individual memory circuit.

The imaging processing function 135a controls each part of the magnetic resonance imaging apparatus 100 to capture magnetic resonance images. For example, the imaging processing function 135a generates sequence information, collects MR data, generates k-space data, and generates magnetic resonance images.

More specifically, the imaging processing function 135a generates sequence information that defines the imaging procedure according to the type of magnetic resonance image to be imaged and the imaging area, and transmits the generated sequence information to the sequence control circuit 120 via the NW interface 131. The sequence control circuit 120 executes various pulse sequences based on the sequence information generated by the imaging processing function 135a.

The imaging processing function 135a also collects MR data converted from MR signals emitted from the subject P by executing various pulse sequences from the sequence control circuit 120 via the NW interface 131.

The imaging processing function 135a also arranges the collected MR data according to the phase encoding amount and frequency encoding amount imparted by the gradient magnetic field. The MR data arranged in k-space is called k-space data. The k-space data is stored in the memory circuitry 132.

The imaging processing function 135a also generates a magnetic resonance image based on the k-space data stored in the memory circuitry 132. For example, the imaging processing function 135a generates a magnetic resonance image by performing reconstruction processing such as a Fourier transform on the k-space data. The imaging processing function 135a stores the generated magnetic resonance image in, for example, the memory circuitry 132.

In this embodiment, the imaging processing function 135a performs imaging of a magnetic resonance image for positioning (hereinafter also referred to as a positioning image) before the actual imaging. The positioning image is also called a plan image, a locator image, or a scout image, and is an image used for positioning the imaging slice in the actual imaging (an image for determining the imaging position of the actual imaging). The actual imaging is imaging of a magnetic resonance image for diagnosis.

In this embodiment, the positioning image is a magnetic resonance image capturing an area including the liver of the subject P. Note that since the position of the liver inside the body of the subject P moves (shifts) several centimeters with breathing, the positioning image is captured in a breath-holding state in which the subject P stops breathing.

The positioning image may be a three-dimensional image or a two-dimensional multi-slice image. The positioning image may be a coarse image with fewer pixels than the diagnostic magnetic resonance image. Alternatively, the positioning image may be a high-resolution three-dimensional magnetic resonance image. In this case, the diagnostic three-dimensional magnetic resonance image may also serve as the positioning image.

In addition, in this embodiment, the diagnostic magnetic resonance images captured in this imaging are two-dimensional magnetic resonance images used to diagnose the liver and gallbladder of subject P. More specifically, in this embodiment, three types of diagnostic two-dimensional magnetic resonance images are captured in this imaging: an axial image (body axis cross-sectional image), a sagittal image (sagittal cross-sectional image), and a coronal image (coronal cross-sectional image).

Note that diagnostic magnetic resonance images do not have to include all of the axial, sagittal, and coronal images, but may include at least one of them.

The determination function 135b determines the first imaging target region to be the subject of the main imaging. The determination function 135b determines the first imaging region based on, for example, the target tissue to be imaged (the liver and gallbladder in this embodiment) detected from the positioning image. As a method for detecting the target tissue from the positioning image, a known method such as template matching, deep learning, or other machine learning method can be adopted.

If the decision function 135b receives input for correcting the imaging area for this imaging from the operator before the first imaging area is finalized, the decision function 135b decides the first imaging area based on the input content. The decision function 135b may also manually accept input of the first imaging area from the operator and decide the first imaging area based on the input content.

Then, the imaging processing function 135a generates sequence information based on the first imaging area determined by the determination function 135b and corrected by the correction function 135f described below, and performs the actual imaging.

Furthermore, the determination function 135b determines the imaging position of an image for positional deviation correction, which is to be captured prior to the actual imaging after capturing the positioning image. For example, the determination function 135b determines the imaging area of a linear coronal image (hereinafter also referred to as a line profile) parallel to the body axis that represents the relationship between position and brightness value, based on a reference part (described later) detected from the positioning image by the detection function 135c (described later). The line profile is an example of a partial image.

The line profile may be a coarse image with fewer pixels than a diagnostic magnetic resonance image. The length of the line profile in the long axis direction is not particularly important and can be set to any length. Note that since the line profile is intended to check the positional fluctuation of the reference site, it is preferable that the length be such that the reference site can be included even if the reference site moves to the maximum extent due to breathing.

When the determination function 135b receives input for modifying the second imaging area before the second imaging area to be subjected to line profile imaging is determined, the determination function 135b determines the second imaging area based on the modified content.

The determination function 135b may also receive input of the second imaging area and determine the second imaging area based on the input.

Then, the imaging processing function 135a generates sequence information based on the second imaging area determined by the determination function 135b, and performs line profile imaging before the main imaging.

The detection function 135c detects the position of a reference site that serves as an index of the imaging position from the positioning image. Specifically, the detection function 135c detects the boundary position of the tissue (organ) shown in the positioning image as the reference site. For example, when the first imaging region is the liver, the detection function 135c detects the upper edge of the liver corresponding to the boundary position between the liver and the lungs as the boundary position. Note that in this embodiment, the detection function 135c detects the upper end of the liver as the boundary position. Here, the upper end of the liver refers to the part of the upper edge of the liver that is closest to the head side. Below, an example in which the upper end of the liver is used as the reference site will be described, but the reference site to be detected is not limited to this.

As a method for detecting the tissue boundary position from the positioning image, for example, an image processing method such as template matching can be adopted. In this case, for example, the memory circuitry 132 stores a template image. The detection function 135c detects an image area on the positioning image in which the tissue boundary position is depicted based on the template image read from the memory circuitry 132.

Specifically, when the first imaging region is the liver, the detection function 135c detects the region in which the boundary position between the liver and the lungs is depicted as the upper edge of the liver.

Furthermore, the method for detecting the upper edge of the liver from the positioning image is not limited to template matching. For example, the detection function 135c can adopt a deep learning or other machine learning method as a method for detecting the upper edge of the liver from the positioning image. In this case, the detection function 135c detects the upper edge of the liver of the subject P from the positioning image by inputting the positioning image into the learned model stored in the memory circuitry 132.

The trained model may be a model that has been trained by associating a magnetic resonance image with an image region on the magnetic resonance image in which the upper edge of the liver is depicted, and is functionalized to output information indicating the boundary of the target tissue (upper edge of the liver) by inputting a positioning image. The trained model is generated by deep learning or other machine learning methods.

The detection function 135c may also receive input from the operator specifying an area on the positioning image, and detect the area specified by the operator as the upper edge of the liver.

The detection function 135c also detects the position of the reference site from the line profile. Specifically, the detection function 135c detects the position of the upper edge of the liver included in the line profile. A specific method for detecting the position of the upper edge of the liver from the line profile will be described later.

Then, the detection function 135c detects a change in the position of the upper edge of the liver based on the position of the upper edge of the liver in the positioning image and the position of the upper edge of the liver in the line profile.

The acquisition function 135d acquires the relative positional relationship between the imaging position during actual imaging, which is set based on the positioning image, and the reference site on the positioning image. For example, the acquisition function 135d acquires the relative positional relationship between the upper edge of the liver detected by the detection function 135c and the first imaging area determined by the determination function 135b. The acquisition function 135d stores information indicating the acquired relative positional relationship, for example, in the memory circuitry 132.

The display control function 135e controls the display of a display related to a magnetic resonance image. For example, the display control function 135e causes the display 134 to display a display indicating the first imaging area determined by the determination function 135b on the positioning image. Also, for example, the display control function 135e causes the display 134 to display a display prompting the operator to input whether or not to confirm the first imaging area determined by the determination function 135b.

Also, for example, the display control function 135e causes the display 134 to display a display indicating the imaging area of the line profile determined by the determination function 135b on the positioning image.Also, for example, the display control function 135e causes the display 134 to display a display prompting the operator to input whether or not to confirm the imaging area of the line profile determined by the determination function 135b.

The correction function 135f corrects the first imaging area during the actual imaging based on the relative positional relationship between the reference part acquired by the acquisition function 135d and the first imaging area, and the positional relationship of the reference part detected by the detection function 135c from each of the positioning image and the line profile.

Specifically, the correction function 135f calculates the amount of change in the position of the reference part on the positioning image based on the position of the reference part detected from each of the positioning image and the line profile. Then, the correction function 135f moves the first imaging area by the calculated amount of change while maintaining the relative positional relationship between the first imaging area acquired by the acquisition function 135d and the reference part, based on the position of the reference part detected from the line profile.

More specifically, the correction function 135f calculates the amount of change (vector) in the Z-axis direction from the position of the reference part acquired from the positioning image and the position of the reference part detected from the line profile. Then, the correction function 135f moves the first imaging area backward on the Z axis by the amount of change, while maintaining the relative positional relationship between the first imaging area and the reference part, based on the position of the reference part detected from the line profile. This causes the first imaging area to shift in accordance with the position of the reference part that shifts with breathing.

An example of the correction process for the first imaging area will be specifically described below with reference to Figs. 2 to 4. Fig. 2 shows an example of a positioning image in which the reference part and the first imaging area are depicted.

First, the imaging processing function 135a captures a positioning image while the subject P is holding his/her breath. Next, the determination function 135b determines the first imaging area. Once the first imaging area is determined, the display control function 135e draws the first imaging area IP on the positioning image 134a and displays it on the display 134.

Although not shown, at this time, the display control function 135e displays a screen that prompts the operator to input whether or not to confirm the first imaging area. When the detection function 135c receives a confirmation input from the operator, it detects the upper end of the upper edge of the liver from the positioning image 134a.

When the detection function 135c detects the upper end of the upper edge of the liver, the display control function 135e displays a part of the upper edge of the liver as the reference site RS on the display 134. Note that the part of the upper edge of the liver may be the upper end.

Although not shown, at this time, the display control function 135e displays a screen that prompts the operator to input whether or not to confirm the position of the reference part. When the acquisition function 135d receives a confirmation input from the operator, it acquires the relative positional relationship between the upper end of the upper edge of the liver on the positioning image 134a and the first imaging region. The acquisition function 135d stores the acquired relative positional relationship in the memory circuitry 132.

Next, the determination function 135b determines a linear region including the upper end portion RS of the upper edge of the liver on the positioning image 134a as the second imaging region.

Figure 3 is a diagram showing an example of the positioning image 134a in which the second imaging area is drawn. When the imaging area for line profile imaging is determined, the display control function 135e draws the imaging area LP for line profile imaging on the positioning image 134a as shown in Figure 3, and displays it on the display 134.

Although not shown, at this time, the display control function 135e displays a screen that prompts the operator to input whether or not to confirm the imaging area for line profile imaging. After receiving the input of confirmation from the operator, the imaging processing function 135a executes line profile imaging while the subject P is holding his breath. Next, the detection function 135c detects the upper edge of the liver from the line profile.

Here, we will specifically explain a method for detecting the upper end of the upper edge of the liver from a line profile. Figure 4 shows an example of the upper edge of the liver included in a line profile.

The detection function 135c detects the position on the line profile 134b where the brightness gradient is maximum as the upper end RS of the upper edge of the liver. This is because the lungs are located above the liver, and the lungs are depicted darker (lower brightness) in the magnetic resonance image, while the liver is depicted brighter (higher brightness) than the lungs, resulting in a large brightness gradient at the boundary between the liver and the lungs.

This makes it possible to easily detect the upper end of the upper edge of the liver by simply calculating the luminance gradient on the line. In other words, by using the upper edge of the liver as the reference site, the detection function 135c can detect the reference site using a simple method.

More specifically, the detection function 135c finds the position where the luminance gradient is maximum on multiple lines (lines along the Z-axis) parallel to the body axes included in the line profile 134b, and detects the point closest to the head side among them as the upper end RS of the upper edge of the liver.

The detection function 135c corrects the position of the first imaging region based on the positional relationship of the upper end portion RS detected from each of the positioning image 134a and the line profile 134b, and the relative positional relationship between the upper end portion RS of the liver and the first imaging region IP acquired by the acquisition function 135d. The position of the upper edge of the liver in the positioning image is compared with the position of the upper edge of the liver in the line profile to detect a change in the position of the upper edge of the liver.

The correction function 135f corrects the positional relationship of the first imaging region to the position of the upper edge of the liver in the Z-axis direction according to the amount of change in the position of the upper edge of the liver detected by the detection function 135c, so that it matches the relative positional relationship between the upper edge of the liver and the first imaging region acquired by the acquisition function 135d.

Then, the imaging processing function 135a generates sequence information based on the first imaging area corrected by the correction function 135f, and performs the actual imaging.

In the above description, an example was described in which the "processor" reads out a program corresponding to each function from a memory circuit and executes it, but the embodiment is not limited to this.

The term "processor" refers to circuits such as, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)).

If the processor is a CPU, for example, the processor realizes a function by reading and executing a program stored in a memory circuit. On the other hand, if the processor is an ASIC, instead of storing a program in a memory circuit, the function is directly built into the processor circuit as a logic circuit.

Note that each processor in this embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining multiple independent circuits to realize its functions. Furthermore, multiple components in FIG. 1 may be integrated into a single processor to realize its functions.

Next, we will explain the flow of the correction process for the first imaging region executed by the magnetic resonance imaging apparatus 100 of this embodiment configured as described above.

Figure 5 is a flowchart showing an example of the flow of the positioning process according to this embodiment. The premise of this flowchart is that the subject P is placed on the top plate 105a, and the top plate 105a is inserted into the imaging port.

First, the imaging processing function 135a captures a positioning image while the subject P is holding his/her breath (step S51). Then, the determination function 135b determines the first imaging area based on the positioning image (step S52).

The display control function 135e draws a display indicating the first imaging area on the positioning image and displays it on the display 134 (step S53). Furthermore, the display control function 135e displays an input screen for determining whether or not to confirm the first imaging area on the display 134, and accepts input from the operator regarding whether or not to confirm the first imaging area (step S54).

If an input indicating that the first imaging area is not to be confirmed is received from the operator (step S54: No), the determination function 135b receives an input from the operator to modify the first imaging area, and determines the first imaging area based on the input content (step S56). Then, the process returns to step S53.

On the other hand, if a confirmation input is received from the operator (step S54: Yes), the detection function 135c detects the upper end of the upper edge of the liver, which serves as the reference site, from the positioning image (step S55).

The display control function 135e draws a display indicating the reference part on the positioning image and displays it on the display 134 (step S57). Furthermore, the display control function 135e displays an input screen for determining whether or not to confirm the reference part on the display 134, and accepts input from the operator as to whether or not to confirm the reference part (step S58).

If the detection function 135c receives an input from the operator indicating that the position is not confirmed (step S58: No), the detection function 135c receives an input from the operator to correct the position of the reference site (the upper end of the upper edge of the liver) and detects the reference site (the upper end of the upper edge of the liver) based on the input (step S60). Then, the process returns to step S57.

On the other hand, if a confirmation input is received from the operator (step S58: Yes), the acquisition function 135d acquires the relative positional relationship between the reference site (the upper end of the upper edge of the liver) detected by the detection function 135c and the first imaging area determined by the determination function 135b (step S59). The acquisition function 135d stores the acquired relative positional relationship in, for example, the memory circuitry 132.

Then, the determination function 135b determines the second imaging area based on the reference site (the upper end of the upper edge of the liver) detected by the detection function 135c (step S61).

The display control function 135e draws a display indicating the second imaging area on the positioning image and displays it on the display 134 (step S62). Furthermore, the display control function 135e displays an input screen for determining whether or not to confirm the second imaging area on the display 134, and receives input from the operator regarding whether or not to confirm the first imaging area (step S63).

If an input indicating that the second imaging area is not to be confirmed is received from the operator (step S63: No), the determination function 135b receives an input from the operator to modify the second imaging area, and determines the first imaging area based on the input (step S65). Then, the process returns to step S62.

On the other hand, if a confirmation input is received from the operator (step S63: Yes), the imaging processing function 135a performs line profile imaging while the subject P is holding his/her breath (step S64).

When the imaging processing function 135a performs line profile imaging, the detection function 135c detects the reference site (the upper end of the liver) on the line profile (step S66).

The correction function 135f corrects the position of the first imaging area by moving the first imaging area by the amount of movement of the reference position based on the reference position detected in step S66 while maintaining the relative positional relationship between the reference part acquired in step S59 and the first imaging area (step S67).

Then, the imaging processing function 135a generates sequence information based on the first imaging area corrected by the correction function 135f, performs the actual imaging, and ends the process (step S68).

In this manner, in the magnetic resonance imaging apparatus 100 of this embodiment, the detection function 135c as a first detection unit detects a reference portion that serves as an index of the imaging position from a positioning image for determining the imaging position of the actual imaging, the acquisition function 135d as an acquisition unit acquires the relative positional relationship between the imaging position and the reference portion, the detection function 135c as a second detection unit detects the position of the reference portion from a linear partial image including the reference portion that was imaged prior to the actual imaging after the positioning image was captured, and the correction function 135f as a correction unit corrects the imaging position during the actual imaging based on the relative positional relationship between the imaging position and the reference portion acquired by the acquisition function 135d and the positional relationship of the reference portion detected by the detection function 135c as the first detection unit and the detection function 135c as the second detection unit.

As a result, even if the subject P holds his/her breath at different times when the positioning image is captured and when the actual image is captured, the correction function 135f can correct the first imaging area so that the relative positional relationship between the reference part and the imaging area when the positioning image is captured and the relative positional relationship between the reference part and the imaging area in the actual image do not change. This makes it possible to prevent a situation in which the desired area cannot be imaged due to the influence of the subject P's breathing.

Furthermore, when performing breath-hold imaging using a magnetic resonance imaging apparatus, the subject P typically holds his or her breath from the exhalation state while imaging is performed, but holding one's breath from the exhalation state is often more uncomfortable than holding one's breath from the inhalation state. Therefore, for example, it is possible that, depending on the subject P, even if he or she is able to hold his or her breath from the exhalation state when imaging the positioning image, he or she will not be able to hold his or her breath from the exhalation state during the actual imaging.

Even in such a case, the magnetic resonance imaging apparatus 100 of this embodiment can correct the first imaging area so that the relative positional relationship between the reference part and the first imaging area does not change between imaging of the positioning image and actual imaging, so there is no need to ask the subject P to hold his breath after exhaling during actual imaging. In other words, the burden on the subject P can be reduced.

In addition, since the line profile is a linear partial image, the line profile imaging is completed in a shorter time than the actual imaging. As a result, the magnetic resonance imaging apparatus 100 according to this embodiment can correct the imaging position without imposing a burden on the subject P.

(First Modification)
In the above embodiment, the upper end of the upper edge of the liver is used as the reference part, but a part other than the upper end of the upper edge of the liver may be detected as the reference part. In this case, for example, the detection function 135c first detects the entire upper edge of the liver. The determination function 135b determines the area of the upper edge of the liver including the part (boundary part) facing the lungs on the positioning image as the second imaging area.

The detection function 135c detects the boundary portion included in the second imaging area determined by the determination function 135b as a reference portion. The acquisition function 135d acquires the relative positional relationship between the boundary portion and the first imaging area.

After the imaging processing function 135a captures the line profile, the detection function 135c first detects the point where the luminance gradient is maximum for each line along the Z axis included in the line profile. The detection function 135c then detects the curve connecting these points as the boundary portion. The detection function 135c compares the boundary portion on the positioning image with the boundary portion on the line profile to detect a change in the position of the boundary portion.

The correction function 135f corrects the positional relationship of the first imaging area to the position of the boundary area in the Z-axis direction in accordance with the change in the position of the boundary area detected by the detection function 135c so that it matches the relative positional relationship between the boundary area and the first imaging area acquired by the acquisition function 135d.

(Second Modification)
In the above embodiment, the imaging target is the liver and the gallbladder, but the imaging target may be tissue other than the liver and the gallbladder. The magnetic resonance imaging apparatus 100 of this modification may also image tissue such as the heart.

The effect of the diaphragm moving due to breathing varies depending on the tissue being imaged. This is because the distance to the diaphragm and the properties of the tissue vary for each tissue, and so the extent to which the tissue moves when the diaphragm moves also differs for each tissue.

The correction function 135f of this modified example corrects the first imaging region using a coefficient that is predefined for each target tissue, in addition to the relative positional relationship between the reference part and the first imaging region. Note that this coefficient represents the degree to which the target tissue moves when the diaphragm moves a certain distance, assuming that the movement of the liver when the diaphragm moves a certain distance is 1.

According to at least one of the embodiments described above, positional deviation during breath-hold imaging can be corrected.

(Third Modification)
In the above-described embodiment, the magnetic resonance imaging apparatus 100 executes various processes. However, some or all of the various processes may be executed by an apparatus other than the magnetic resonance imaging apparatus 100 .

For example, another information processing device connected to the magnetic resonance imaging apparatus 100 via a network or the like may have some or all of the imaging processing function 135a, the determination function 135b, the detection function 135c, the acquisition function 135d, the display control function 135e, and the correction function 135f.

(Variation 4)
In the above embodiment, the computer system 130 is a part of the magnetic resonance imaging apparatus 100. However, the computer system 130 may be configured as a device (e.g., a control device) separate from the magnetic resonance imaging apparatus 100. In this case, the computer system 130 controls the operation of each part of the magnetic resonance imaging apparatus 100 to execute the various processes described above.

Although several 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 forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and spirit of the invention.

REFERENCE SIGNS LIST 100 Magnetic resonance imaging apparatus 101 Static magnetic field magnet 103 Gradient magnetic field coil 104 Gradient magnetic field power supply 105 Bed 105a Top 106 Bed control circuit 107 Transmitting coil 108 Transmitting circuit 109 Receiving coil 110 Receiving circuit 120 Sequence control circuit 130 Computer system 131 NW interface 132 Memory circuit 133 Input interface 134 Display 135 Processing circuit 135a Imaging processing function 135b Decision function 135c Detection function 135d Acquisition function 135e Display control function 135f Correction function P Subject

Claims (9)

a first determination unit that determines the first imaging position based on a target tissue to be imaged that is depicted in a positioning image, which is a coronal image for determining a first imaging position of main imaging, the positioning image being imaged in a breath-holding state in which the subject's breathing is stopped;
a second determination unit that detects an entire upper edge of the liver from the positioning image, and determines, within the entire upper edge of the liver, a region including a boundary portion facing the lungs on the positioning image as a second imaging position of a partial image that is a linear coronal image including a reference portion serving as an index of the first imaging position, the region being imaged after the positioning image is captured and prior to the main imaging;
a first detection unit that detects, from the positioning image , the boundary portion included in the determined second imaging position as the reference portion;
an acquisition unit that acquires a relative positional relationship between the first imaging position in the positioning image and the boundary portion detected from the positioning image ;
a second detection unit that detects, from the partial image captured prior to the main imaging, a point at which a luminance gradient is maximum for each line along a body axis of the subject included in the partial image, and detects a curve connecting these points as the boundary portion ;
a correction unit that compares the boundary portion on the positioning image with the boundary portion on the partial image to detect a change in a position of the boundary portion, and corrects a positional relationship of the first imaging position with respect to a position of the boundary portion in the body axis direction in accordance with the detected change in the position of the boundary portion so that the positional relationship coincides with the acquired relative positional relationship;
A magnetic resonance imaging apparatus comprising: The magnetic resonance imaging apparatus according to claim 1, wherein the correction unit calculates an amount of change in the position of the reference part on the positioning image based on the position of the reference part detected by the first detection unit and the second detection unit, and moves the first imaging position by the amount of change based on the position of the reference part detected by the second detection unit while maintaining the relative positional relationship between the first imaging position and the reference part. The first detection unit detects a boundary position between tissues as a reference site.
2. A magnetic resonance imaging apparatus according to claim 1. The first detection unit detects a boundary position between the lungs and the liver as the reference site.
4. A magnetic resonance imaging apparatus according to claim 3. The first detection unit detects an upper end portion, which is a portion of a boundary position between the lungs and the liver that is closest to a head side, as the reference portion.
5. A magnetic resonance imaging apparatus according to claim 4. The second detection unit detects the position of the reference portion based on a change in luminance value of pixels constituting the partial image.
2. A magnetic resonance imaging apparatus according to claim 1. The first determination unit determines a first imaging position of the partial image based on the reference part.
2. A magnetic resonance imaging apparatus according to claim 1. The correction unit corrects a positional relationship of the first imaging position with respect to the reference site based on a detection result of the second detection unit and a coefficient representing a movement of a tissue corresponding to a tissue to be imaged in the main imaging.
8. A magnetic resonance imaging apparatus according to claim 1. a first determination step of determining the first imaging position based on a target tissue to be imaged depicted in a positioning image, which is a coronal image for determining a first imaging position of main imaging, the positioning image being imaged in a breath-holding state in which the subject's breathing is stopped;
a second determination step of detecting an entire upper edge of the liver from the positioning image, the target tissue including the liver, and determining, within the entire upper edge of the liver, a region including a boundary portion facing the lungs on the positioning image, as a second imaging position of a partial image, the partial image being a linear coronal image including a reference portion serving as an index of the first imaging position, the region being imaged after the positioning image is captured and prior to the main imaging;
a first detection step of detecting, from the positioning image , the boundary portion included in the determined second imaging position as the reference portion;
an acquisition step of acquiring a relative positional relationship between the first imaging position in the positioning image and the boundary portion detected from the positioning image ;
a second detection step of detecting points at which a luminance gradient is maximum for each line along a body axis of the subject included in the partial image captured prior to the main imaging, and detecting a curve connecting these points as the boundary portion;
a correction step of comparing the boundary portion on the positioning image with the boundary portion on the partial image to detect a change in a position of the boundary portion, and correcting a positional relationship of the first imaging position with respect to a position of the boundary portion in the body axis direction in accordance with the detected change in position of the boundary portion so that the positional relationship coincides with the acquired relative positional relationship;
A program for causing a computer to execute the following.

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