JP5677908B2 - Magnetic resonance imaging apparatus, detection method, and program - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus having a plurality of coil elements, a detection method, and a program.

  When imaging a subject with a magnetic resonance imaging apparatus, the operator lays the subject in a cradle and then uses the positioning light to set a landmark on the subject. The landmark is used as a mark for defining the moving distance of the cradle when the subject is carried into the magnet bore. After setting the landmark, the cradle moves so that the landmark coincides with the magnetic field center of the magnet. Therefore, the imaging region of the subject can be carried into the magnet bore. As a technique for setting a landmark and carrying a subject into a bore of a magnet, for example, there is a method of Patent Document 1.

JP 2003-290169 A

  However, each time a subject is imaged, the landmark needs to be manually set by the operator, which causes a problem that the operator is burdened. Therefore, it is desired to reduce the work burden on the operator.

A first aspect of the present invention is a magnetic resonance imaging apparatus comprising a plurality of coil elements in a cradle that supports a subject,
Q map creating means for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
Detecting means for detecting the position of each part of the subject based on the Q map;
Is a magnetic resonance imaging apparatus.

A second aspect of the present invention is a detection method for detecting the position of each part of the subject using a magnetic resonance imaging apparatus having a plurality of coil elements in a cradle that supports the subject,
A Q map creating step for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
A detection step of detecting a position of each part of the subject based on the Q map;
Is a detection method.

A third aspect of the present invention is a program for a magnetic resonance imaging apparatus including a plurality of coil elements in a cradle that supports a subject,
A Q map creating process for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
Detection processing for detecting the position of each part of the subject based on the Q map;
Is a program for causing a computer to execute.

  By creating the Q map, the position of each part of the subject can be detected, so that setting of landmarks becomes unnecessary and the burden on the operator can be reduced.

1 is a schematic diagram of a magnetic resonance imaging apparatus according to a first embodiment of the present invention. It is explanatory drawing of the structure of the cradle 3a. It is a figure which shows an example of the combination of the coil element which can be selected. FIG. 3 is a diagram showing a flow when imaging a subject 12 using an MRI apparatus 100. It is a figure which shows a mode when the test object 12 sleeps on the cradle 3a. It is a figure which shows a mode when the transmitter 6 outputs the traveling wave FS (f) to the receiver 8. FIG. 6 is a diagram illustrating a state when a transmitter 6 outputs a traveling wave FS (f) to each coil element E. FIG. It is a figure which shows an example of Q map. It is a figure which shows the mode of matching roughly. FIG. 3 is a diagram illustrating a state in which a subject 12 is carried into a bore 21. It is a figure which shows the MRI apparatus of a 2nd form. It is a figure which shows the flow when image | photographing the test object 12 in a 2nd form. FIG. 3 is a diagram showing a state when a subject 12 is carried into a bore 21.

  Hereinafter, although the form for inventing is demonstrated, this invention is not limited to the following forms.

FIG. 1 is a schematic diagram of a magnetic resonance imaging apparatus according to the first embodiment of the present invention.
A magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus”, MRI: Magnetic Resonance Imaging) 100 includes a magnet 2, a table 3, and the like.

The magnet 2 has a bore 21 in which the subject 12 is accommodated. The magnet 2 includes a superconducting coil, a gradient coil, an RF coil, and the like.
The table 3 has a cradle 3 a for supporting the subject 12.

FIG. 2 is an explanatory diagram of the structure of the cradle 3a.
2A is a perspective view of the cradle 3a, and FIG. 2B is a view of the inside of the cradle 3a seen through from above.

  The cradle 3a incorporates a plurality of coil elements E for receiving magnetic resonance signals from the subject 12 (see FIG. 2B). In FIG. 2B, as a representative, one coil element is denoted by the symbol “E”. When receiving a magnetic resonance signal from the subject 12, a combination of coil elements used to receive the magnetic resonance signal of the subject 12 is selected from the plurality of coil elements E. The combination of coil elements that can be selected is determined in advance. FIG. 3 shows an example of a combination of selectable coil elements. In the first embodiment, it is assumed that seven coil element combinations C1 to C7 can be selected. From among the seven types of coil elements C1 to C7, an optimal combination of coil elements is selected according to the imaging region of the subject 12 and the like.

  The plurality of coil elements E built in the cradle 3 a are used when specifying the position of each part of the subject 12. The procedure for specifying the position of each part of the subject 12 using these coil elements E will be described later.

Returning to FIG. 1, the description will be continued.
The MRI apparatus 100 further includes a sequencer 5, a transmitter 6, a gradient magnetic field power supply 7, a receiver 8, a central processing unit 9, an operation unit 10, and a display unit 11.

  Under the control of the central processing unit 9, the sequencer 5 sends information for executing a pulse sequence to the transmitter 6 and the gradient magnetic field power supply 7.

  The transmitter 6 supplies a signal to an RF coil built in the magnet 2. The transmitter 6 outputs a traveling wave FS (f) for measuring the Q value of the coil element E embedded in the cradle 3a. The traveling wave FS (f) will be described later.

The gradient magnetic field power supply 7 supplies a signal to the gradient coil built in the magnet 2.
The receiver 8 processes the magnetic resonance signals received by the plurality of coil elements E and outputs them to the central processing unit 9.

  The central processing unit 9 implements various operations of the MRI apparatus 100 such as transmitting necessary information to the sequencer 5 and the display unit 11 and reconstructing an image based on data received from the receiver 8. The operation of each unit of the MRI apparatus 100 is controlled. The central processing unit 9 is constituted by a computer, for example. The central processing unit 9 includes a Q value calculating unit 91, a Q map creating unit 92, a detecting unit 93, an imaging region specifying unit 94, a coil element selecting unit 95, and the like.

The Q value calculation means 91 calculates a Q value representing the sharpness of resonance of each coil element E.
The Q map creating unit 92 creates a Q map that represents a map of the Q values calculated by the Q value calculating unit 91.
The detection means 93 detects the position of each part of the subject 12 based on the Q map created by the Q map creation means 92.
The imaging part specifying unit 94 specifies the imaging part of the subject 12.

  The coil element selection means 95 selects the combination of coil elements used when performing a scan from among the combinations C1 to C7 (see FIG. 3) of the coil elements.

  The central processing unit 9 is an example of the Q value calculation unit 91 to the coil element selection unit 95, and functions as these units by executing a predetermined program.

The operation unit 10 is operated by the operator 13 and inputs various information to the central processing unit 9. The display unit 11 displays various information.
The MRI apparatus 100 is configured as described above.

FIG. 4 is a diagram illustrating a flow when the subject 12 is imaged using the MRI apparatus 100.
In step ST1, the operator places the subject 12 on the cradle 3a. FIG. 5 shows a state when the subject 12 lies on the cradle 3a. FIG. 5 also shows the coil element E embedded in the cradle 3a.
When the subject 12 is placed in the cradle 3a, the process proceeds to step ST2.

  In step ST2, the Q value of each coil element E embedded in the cradle 3a is measured. Hereinafter, an example of a method for measuring the Q value of the coil element E will be described with reference to FIGS. 6 and 7.

  First, as shown in FIG. 6, the transmitter 6 outputs a traveling wave FS (f) (f: frequency of traveling wave) for measuring the Q value of the coil element E to the receiver 8. The receiver 8 receives the traveling wave FS (f) from the transmitter 6.

  Next, the transmitter 6 outputs a traveling wave FS (f) to each coil element E as shown in FIG. In each coil element E, the traveling wave FS (f) is reflected. At this time, the receiver 8 receives the reflected wave RS (f) from each coil element E.

As described above, the receiver 8 can receive the traveling wave FS (f) from the transmitter 6 and the reflected wave RS (f) from each coil element. Therefore, a ratio r (f) between the traveling wave FS (f) and the reflected wave RS (f) is obtained for each coil element E.
r (f) = FS (f) / RS (f) (1)

  In the first embodiment, the step of obtaining the ratio r (f) is performed while changing the frequency f of the traveling wave FS (f). Therefore, the frequency characteristic of the ratio r (f) can be obtained for each coil element E. The Q value calculation means 91 calculates a Q value representing the sharpness of resonance of each coil element E based on the frequency characteristic of the ratio r (f) of each coil element. When the Q value of the coil element is calculated, the process proceeds to step ST3.

  In step ST3, the map creating means 92 creates a Q map representing the map of Q values calculated in step ST2 (see FIG. 8).

FIG. 8 is a diagram illustrating an example of the Q map.
The Q value of the coil element E varies depending on the positional relationship with the subject 12. For example, when the distance between the coil element E and the subject 12 is long, the Q value of the coil element E tends to increase. On the other hand, when the distance between the coil element E and the subject 12 is short, the coil element E The Q value tends to increase. Therefore, the position of the subject 12 with respect to the cradle 3a can be known by creating the Q map. After creating the Q map, the process proceeds to step ST4.

  In step ST4, the detection means 93 detects the position of each part of the subject 12 based on the Q map created in step ST3. Hereinafter, this detection method will be described.

  First, the detection means 93 performs matching between the Q map created in step ST3 and the standard Q map. FIG. 9 schematically shows the state of matching. The standard Q map represents a Q map obtained when a human body having a standard body shape lies on the cradle 3a, and is prepared in advance before imaging the subject 12. As a standard Q map creation method, for example, there is a method in which each Q map of a plurality of subjects 12 is acquired in advance before the subject 12 is imaged, and the plurality of acquired Q maps are averaged. . The standard Q map is associated with position information of each part of a human body having a standard body shape. In the first embodiment, the standard Q map is associated with positional information of the human head, lungs, abdominal cavity, pelvic cavity, arms, and legs.

  The detection means 93 performs matching between the Q map created in step ST3 and the standard Q map. In the matching, the Q map created in step ST3 is moved, rotated, enlarged, reduced, etc., so that the positional deviation between the created Q map and the standard Q map is minimized. Since the standard Q map is associated with the positional information of the human head, lungs, abdominal cavity, pelvic cavity, arms, and legs, by performing matching, the head, lungs, abdominal cavity of the subject 12 are matched. The position of the pelvic cavity, arm, and leg can be detected. As a method for moving, rotating, enlarging, and reducing the Q map, for example, affine transformation can be used. The standard Q map may be moved, rotated, enlarged or reduced. Also, a plurality of standard Q maps are prepared for different physiques of the human body (for example, height), and a standard Q map that matches the physique of the subject 12 is selected from the plurality of standard Q maps. Matching may be performed. When matching is completed, the process proceeds to step ST5.

  In step ST5, the operator selects a protocol used when the subject 12 is imaged. The protocol is a rule that defines imaging conditions (such as pulse sequences used) and imaging sections (axial, sagittal, coronal, etc.) of the subject 12. The central processing unit 9 stores a plurality of protocols, and the operator can select a protocol for imaging the subject 12 from the plurality of protocols by operating the operation unit 10. . If a protocol is selected, it will progress to step ST6.

  In step ST6, the imaging region specifying means 94 specifies the imaging region. In the first form, the protocol is associated with information relating to the imaging region. Therefore, the imaging region specifying means 94 can specify the imaging region based on the protocol selected by the operator in step ST5. Note that the operator may specify the imaging region by inputting information on the imaging region. In the first form, the imaging region is assumed to be the pelvic cavity. If the imaging region is specified, the process proceeds to step ST7.

  In step ST7, the subject 12 is carried into the bore 21 so that the imaging region (pelvic cavity) specified in step ST6 reaches the magnetic field center C. FIG. 10 shows a state where the subject 12 is carried into the bore 21. When the subject 12 is carried into the bore 21, the process proceeds to step ST8.

  In step ST8, a localizer scan for acquiring image data of the imaging region at a low resolution is executed. When performing the localizer scan, the coil element selection means 95 (see FIG. 1) selects the coil element closest to the imaging region (pelvic cavity) from among the selectable coil element combinations C1 to C7 (see FIG. 3). Select a combination. In the first embodiment, the coil element combination C6 is selected. Therefore, in the localizer scan, image data of the subject 12 is acquired using the coil element combination C6. When the localizer scan ends, the process proceeds to step ST9.

  In step ST9, the operator sets scan conditions such as a slice position based on the image data obtained in step ST8, executes the main scan, and ends the flow.

  In the first embodiment, a Q map can be created, and the position of each part of the subject 12 can be detected based on the created Q map. Therefore, the subject 12 can be carried into the bore 21 without setting a landmark that serves as a mark for defining the moving distance of the cradle 3a, so that the operator does not need to set a landmark. Work burden can be reduced.

  In the first embodiment, when measuring the Q value of each coil element E, the transmitter 6 transmits the traveling wave FS (f), and the receiver 8 receives the reflected wave RS (f) (FIG. 6). And FIG. 7). Therefore, the Q value can be measured without the MRI apparatus 100 having a dedicated device for transmitting and receiving the traveling wave FS (f) and the reflected wave RS (f).

(2) Second Embodiment FIG. 11 is a diagram showing an MRI apparatus according to a second embodiment.
In the MRI apparatus 200 according to the second embodiment, the plurality of coil elements E are embedded under the lower surface 21a of the bore 21 of the magnet 2 instead of the cradle 3a. Other configurations are the same as those of the MRI apparatus 100 of the first embodiment.

FIG. 12 is a diagram showing a flow when the subject 12 is imaged in the second embodiment.
In step ST1, the operator places the subject 12 on the table as shown in FIG. If the subject 12 is laid down, the process proceeds to step ST11.

  In step ST11, the subject 12 is carried into the bore 21. FIG. 13 shows a state when the subject 12 is carried into the bore 21. When the subject 12 is carried into the bore 21, the process proceeds to step ST2.

  Steps ST2 to ST4 are the same as in the first embodiment. In the second embodiment, the subject 12 is first carried into the bore 21 before executing step ST2. By loading the subject 12 into the bore 21, the Q value of each coil element changes according to the relationship between the loading position of the subject 12 and the position of each coil element E. Therefore, after carrying the subject 12 into the bore 21, by executing steps ST2 to ST4, the position of each part of the subject 12 can be detected as in the first embodiment.

If the position of each part is detected, the process proceeds to step ST5.
Steps ST5 and ST6 are also the same as in the first embodiment. If an imaging region is specified in step ST6, the process proceeds to step ST7.

In step ST7, the position of the cradle 3a is adjusted as necessary. For example, if the positional deviation between the imaging region and the magnetic field center C is large, the position of the cradle 3a is adjusted so that the positional deviation is small, and the process proceeds to step ST8. On the other hand, if the positional deviation is sufficiently small, the process proceeds to step ST8 without adjusting the position of the cradle 3a.
Steps ST8 and ST9 are also the same as those in the first embodiment, and a description thereof will be omitted.

  Thus, the present invention can also be applied to the case where the coil element E is provided in the magnet 2.

2 Magnet 3 Table 3a Cradle 5 Sequencer 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Central processing unit 10 Operation unit 11 Display unit 12 Subject 91 Q value calculation unit 92 Q map creation unit 93 Detection unit 94 Imaging site identification unit 95 Coil element selection means 100, 200 MRI apparatus

Claims (9)

A magnetic resonance imaging apparatus comprising a plurality of coil elements in a cradle that supports a subject,
Q map creating means for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
Detecting means for detecting the position of each part of the subject based on the Q map;
A magnetic resonance imaging apparatus. A magnetic resonance imaging apparatus having a plurality of coil elements in a magnet,
Q map creating means for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
Detecting means for detecting the position of each part of the subject based on the Q map;
A magnetic resonance imaging apparatus.   The magnetic resonance imaging apparatus according to claim 1, further comprising a Q value calculating unit that calculates a Q value of each of the plurality of coil elements. A transmitter for outputting a signal for causing the transmission coil to transmit an RF pulse;
Receiving a magnetic resonance signal received by the plurality of coil elements;
The transmitter is
A traveling wave for measuring the Q value of the coil element is output to each of the plurality of coil elements,
The receiver is
The magnetic resonance imaging apparatus according to claim 3, wherein a reflected wave of the traveling wave is received from each of the plurality of coil elements. The transmitter outputs the traveling wave to the receiver while changing the frequency of the traveling wave, and further outputs the traveling wave to each of the plurality of coil elements while changing the frequency of the traveling wave. ,
The receiver receives the traveling wave from the transmitter, and further receives a reflected wave of the traveling wave from each of the plurality of coil elements,
The magnetic resonance imaging apparatus according to claim 4, wherein the Q value calculation unit calculates a Q value of each of the plurality of coil elements based on the traveling wave and the reflected wave received by the receiver. The detection means includes
The magnetic resonance imaging apparatus according to claim 1, wherein the position of each part of the subject is detected by matching the Q map with a standard Q map.   The magnetic resonance imaging apparatus according to claim 1, further comprising an imaging part specifying unit that specifies an imaging part of the subject. Using a magnetic resonance imaging apparatus having a plurality of coil elements in a cradle that supports a subject, a detection method for detecting the position of each part of the subject,
A Q map creating step for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
A detection step of detecting a position of each part of the subject based on the Q map;
A detection method comprising: A program of a magnetic resonance imaging apparatus having a plurality of coil elements in a cradle that supports a subject,
A Q map creating process for creating a Q map representing a map of the Q value based on the Q value of each of the plurality of coil elements;
Detection processing for detecting the position of each part of the subject based on the Q map;
A program to make a computer execute.