JP6708504B2 - Magnetic resonance imaging equipment - Google Patents

Description

The present invention relates to a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus) having a blood vessel imaging function, and particularly to an MRI apparatus for performing TOF (Time-off-Flight) imaging using a two-dimensional selective excitation pulse as a presaturation pulse and its control. Regarding the method.

Since a two-dimensional selective excitation pulse (hereinafter referred to as a 2DRF pulse) can selectively excite a region having a predetermined shape, by applying this as a presaturation pulse in TOF imaging, the dominant region of a specific blood vessel can be confirmed. it can. TOF imaging using such a presaturation pulse is disclosed in Non-Patent Document 1, for example, and is referred to as Selective TOF MRA. The 2DRF pulse used as the presaturation pulse is called a BeamSaturation pulse (BeamSat pulse for short).

In Selective TOF MRA, in addition to normal TOF imaging that does not use the BeamSat pulse, it is necessary to perform imaging that also uses the BeamSat pulse for the number of blood vessels for which the dominant region is to be examined. Therefore, the imaging time is extended in proportion to the number of blood vessels. For example, the imaging time of TOF is usually about 5 minutes, but a total of about 10 minutes (5 minutes×2 times) of imaging time is required to examine the dominant region of two left and right internal carotid arteries. When the imaging time is long, not only the inspection efficiency is poor, but also the positional deviation depending on the body movement of the subject occurs, so that the accuracy of the inspection also deteriorates. Further, in Selective TOF MRA, in order to visualize only the blood vessels suppressed by the BeamSat pulse, a difference image between the imaging using the BeamSat pulse and the imaging not used is acquired. If there is the above-mentioned positional deviation between these two images, a difference difference also occurs.

As a technique for shortening a blood vessel imaging time using a presaturation pulse, a method capable of high-speed imaging by effectively acquiring a signal has been proposed. For example, the technique disclosed in Patent Document 1 discloses a method of shortening the imaging time by cutting the encoding in the slice direction or the phase direction of the 3D data to be acquired.

Selective TOF MRA using Beam Saturation pulse, Takashi Nishihara, et al, Proc. ISMRM 2012, 2497

JP, 2014-100392, A

In the technique described in Patent Document 1, when an image is projected from the direction in which 3D data is desired to be observed, the image quality is degraded by making the direction in which the encoding is reduced coincide with the above-described observed direction. There is an advantage that an image having excellent visibility of blood vessels can be obtained. However, when the encoding is simply cut or the number of encodings is reduced, the problem that the signal of the BeamSat pulse application region or the region displaced due to the body motion becomes high in the difference image, and the visibility of the blood vessel is deteriorated particularly in the projection image. There is.

The present invention is based on the technique described in Patent Document 1 and focuses on the difference in the fineness of the structure between an organ or tissue around a blood vessel and a target blood vessel in which positional misalignment is likely to be a problem, and a direction to reduce the number of encodings Regarding the above, the above problem is solved by limiting the band for acquiring data.

Specifically, the MRI apparatus of the present invention performs 3D blood vessel imaging using a presaturation pulse, an imaging unit that collects 3D-k spatial data, and an imaging condition setting unit that sets imaging conditions by the imaging unit. And a control unit that controls the operation of the imaging unit. The condition set by the imaging condition setting unit includes a setting of a data direction in which the number of encodes in the 3D-k space data is reduced, and the control unit sets a data direction for the data direction set by the imaging condition setting unit. A band setting unit that sets a k-space band for acquiring

ADVANTAGE OF THE INVENTION According to this invention, by restricting the band which acquires data to the band which matched the target blood vessel, the high signal of the organ or tissue other than the blood vessel or the BeamSat pulse application region was suppressed, and the visibility of the blood vessel was excellent. An image is obtained.

The figure which shows the whole structure of the MRI apparatus to which this invention is applied. The figure which shows an example of the pulse sequence of the MRI apparatus of this invention. (A), (b) is a figure which shows an example of a presaturation pulse, respectively. The functional block diagram of the calculating part of 1st embodiment. The figure which shows the flow of operation|movement of the MRI apparatus of 1st embodiment. FIG. 6 is a diagram showing an example of a GUI displayed on a display unit in the MRI apparatus of the first embodiment. (A) And (b) is a figure which shows the pulse sequence example of the prescan of 1st embodiment, respectively. The figure which shows the example of an image display for band setting. The figure which shows the example of the difference image acquired by different encoding. The figure which shows the flow of operation|movement of the MRI apparatus of 2nd embodiment. The functional block diagram of the calculating part of 3rd embodiment. The figure which shows the flow of operation|movement of the MRI apparatus of 3rd embodiment. (A)-(c) is a figure explaining the relationship between a site|part and a zone|band. The figure which shows the flow of operation|movement of the MRI apparatus of 4th embodiment. The figure which shows an example of GUI displayed on a display part in the MRI apparatus of 4th embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the overall configuration of the MRI apparatus to which the present invention is applied will be described. FIG. 1 shows the configuration of a typical MRI apparatus. As an imaging system, this MRI apparatus includes a magnet 102 that generates a static magnetic field in a space where the subject 101 is placed, a gradient magnetic field coil 103 that generates a gradient magnetic field in this space, and a subject placed in the static magnetic field space. An RF coil 104 for applying a high-frequency magnetic field, an RF probe 105 for detecting an MR signal generated by the subject 101, and a bed 112 for placing the subject 101 and bringing the subject 101 into a static magnetic field space are provided. The arithmetic control system includes a signal processing unit 107, an arithmetic unit 108, a control unit 111, and a storage device 115. The arithmetic control system also includes an input unit 113 and a display unit 114 as a user interface for communicating with the operator.

The gradient magnetic field coil 103 is composed of gradient magnetic field coils in three directions of X, Y and Z, and generates a gradient magnetic field according to a signal from the gradient magnetic field power source 109. By the combination of the three directions of X, Y, and Z, the three directions orthogonal to each other, the slice direction, the phase encoding direction, and the reading direction can be arbitrarily set. The RF coil 104 generates a high frequency magnetic field according to the signal from the RF transmitter 110. The signal received by the RF probe 105 is detected by the signal detection unit 106, subjected to signal processing by the signal processing unit 107, and then subjected to arithmetic processing such as image reconstruction and correction by the arithmetic unit 108 to be converted into an image. The image is displayed on the display unit 114. The gradient magnetic field power supply 109, the RF transmission unit 110, and the signal detection unit 106 are controlled by the control unit 111, and the control time chart is generally called a pulse sequence. There are various pulse sequences depending on the imaging method, and these basic forms are stored in advance in the internal memory of the control unit 111 or the storage device 115 as a program. Further, the imaging conditions necessary for generating the pulse sequence can be input from the input unit 113 and confirmed on the display unit 114.

The MRI apparatus of this embodiment stores a TOF pulse sequence as a pulse sequence and executes this under a specific condition. An example of the TOF pulse sequence is shown in FIG. In FIG. 2, the horizontal axis is the time axis, the RF/Signal axis is the application of the RF pulse and the measurement of the echo signal, Gs is the gradient magnetic field in the slice direction, Gp is the gradient magnetic field in the phase encoding direction, and Gr is the reading direction. Represents the gradient magnetic field of.

The pulse sequence shown in FIG. 2 is a pulse sequence in which a presaturation pulse 210 is added to the pulse sequence 200 of the 3D-gradient echo (GrE) system. The presaturation pulse 210 is a pulse that excites a region (referred to as a presati region) different from the target imaging region in order to saturate the blood flowing into the region to be imaged by the pulse sequence 200 (target imaging region). The presaturation pulse may be a conventional slice selection type pulse as shown in FIG. 3A or a BeamSat pulse as shown in FIG. 3B, but a BeamSat pulse is used in this embodiment. The BeamSat pulse is composed of an RF pulse 211 having a predetermined shape and gradient magnetic fields 212 and 213 in two or three directions with oscillating amplitudes, here a gradient magnetic field Gx in the X direction and a gradient magnetic field Gy in the Y direction. Unlike the conventional slice selection, for example, only a columnar region determined by the direction of the gradient magnetic field can be selectively excited. Therefore, a plurality of blood vessels in the same slice that are conventionally excited at the same time by the presaturation pulse can also be separately excited, and the degree of freedom in setting the presaturation region is large. Although not shown in FIG. 3, a crusher gradient magnetic field pulse having a large magnetic field intensity is applied after such a pull saturation pulse. Thereby, the signal in the specific area can be suppressed.

Since the pulse sequence 200 is generally similar to the 3D-GrE system pulse sequence, detailed description thereof will be omitted, but slice encoding or phase encoding is performed according to an instruction from an operator or a result of prescan described later. For one of the measurements, the number of encodes is thinned out.

The MRI apparatus according to the present embodiment controls a band (k-space band) in which data is further acquired in a direction in which the number of encodes is thinned, on the premise of measurement in which the number of encodes is thinned. The band is controlled in consideration of the fineness of the structure of the blood vessel to be imaged and its surrounding tissues and organs. Specifically, the control unit 111 executes a pre-scan for setting the optimum band, determines the band manually or automatically based on the image obtained by the pre-scan, or an imaging condition specified by the operator. The band is automatically determined based on the information of the imaged region or the tissue to be removed from the image. Hereinafter, embodiments of a control method and a device configuration for realizing the control method will be described in detail.

<First embodiment>
In the present embodiment, the operator inputs the optimum band, and the imaging unit uses the input optimum band to set an offset amount of the band in the encoding thinning direction (hereinafter, referred to as an encoding reduction direction). Then, imaging without presaturation pulse and imaging with presaturation are performed. At this time, the operator acquires and presents information necessary for determining the optimum band.

First, the function of the calculation unit of this embodiment will be described with reference to FIG. The arithmetic unit realizes the functions of the arithmetic control system of the MRI apparatus shown in FIG. 1 (a part of the functions of the arithmetic unit 108 and the functions of the control unit 111). As the main functional unit, the above-described 3D-TOF imaging is performed. An imaging control unit (including an imaging condition setting unit) 401 that controls the operation of the imaging system according to the pulse sequence and the imaging condition set by the user, and automatically or manually sets a band in the encoding reduction direction during 3D-TOF imaging. The band setting unit 402 performs an operation such as Fourier transform on the 3D-k space data acquired by 3D-TOF imaging to create image data, or performs a difference between k-space data or image data to create a difference image. An image reconstructing unit 403 that performs calculations necessary for image reconstruction, and a display image that causes image data to be displayed on the display unit 114 together with other incidental information are created and displayed in accordance with a command or the like input via the input unit 113. A display control unit 404 for controlling is provided.

The functions of these arithmetic control systems are realized, for example, by executing a program installed in a CPU, and part of the functions is realized by hardware such as ASIC and FPGA.

Next, the operation of the MRI apparatus of this embodiment will be described in detail with reference to FIG. In FIG. 5, steps S12, S15, and S17 on the right side mainly show the setting process associated with the operation via the input unit of the operator, and the steps on the left side show the operation of the other devices (show other process flow). The same applies to the drawings).

[Step S11]
First, after arranging a desired imaging region of the inspection object in the center of the static magnetic field space (inspection space), preliminary imaging (prescan 1) for determining a detailed imaging position and a region to be preexcited by the presaturation pulse is performed. .. The pulse sequence executed in the prescan 1 is basically the same as the 3D-TOF pulse sequence 200 shown in FIG. 2, and the presaturation pulse 210 is not used. The imaging condition of the pre-scan 1 is not particularly limited, but a relatively wide area is selected as the target imaging area and imaging is performed. Further, when the data of the prescan 1 is used in step S14 for determining a band described below, the preliminary imaging (prescan 2) executed in step S14 is made to match the imaging condition. As the imaging conditions, specifically, the RF condition of the prescan 1, the TR, the step width in the encoding direction, and the like are made to match the RF condition of the prescan 2, the TR, the encode step width, and the like. Here, a case where the data of the prescan 1 is used will be described as an example.

The image reconstruction unit 403 reconstructs an image using the echo signal obtained in the prescan 1, and the display control unit 404 causes the display unit 114 to display the image. As the image, for example, a MIP (Maximum Intensity Projection) image in which 3D data is projected is created and displayed.

[Step S12]
When the operator looks at the image displayed on the display unit 114 and inputs the target imaging region, the region to be excited by the presaturation pulse, and the encoding reduction direction (slice encoding direction or phase encoding direction), this is input. According to the above conditions, the imaging control unit 401 calculates and sets a pulse sequence including a presaturation pulse. As for the area setting, as shown in FIG. 6, for example, the target imaging area is designated by enclosing it in a rectangular (rectangular parallelepiped) frame 601 on the MIP image 600 displayed on the display unit 114, and the presaturation position is set. It is specified by a columnar positioning UI 602 that imitates the excitation shape of the saturation pulse. The target presaturation region is the location where the positioning UI 602 and the blood vessel intersect, and is displayed by hatching, for example.
The imaging control unit 401 uses the designated coordinates on the screen to calculate, for example, the strength of the slice selection gradient magnetic field and the encoding step width, and sets the pulse sequence (function of the imaging condition setting unit). The direction in which the number of encodings is thinned may be selected by the operator by displaying a GUI including a box for the display control unit 404 to select the direction together with the image for specifying the region on the display unit 114.

[Step S13]
At the presaturation position set in step S12, a presaturation pulse is added and a 3D-TOF pulse sequence is executed. This image capturing is a preliminary image capturing (pre-scan 2) for setting a band in the direction in which the number of encodes is thinned out, and several encodings (for example, about 5 to 10 encodings) are performed while advancing the encoding in the direction by one encoding from zero. measure. This number of encodings may be held in advance inside the arithmetic control system, or may be set by the operator in the previous step (for example, S12).

FIG. 7 shows an example of the pulse sequence of the prescan 2. FIG. 7A shows a case of thinning out the encoding in the slice direction, and FIG. 7B shows a case of thinning out the encoding in the phase encoding direction. Both have the same basic form as the pulse sequence 200 of FIG. 2, but in these pulse sequences, only the encoding near the center of the ks space or the kp section is acquired in the encoding thinning direction.

Although not shown in FIG. 7, in the prescan 2, it is necessary to blank the presaturation pulse, for example, for about 1 second before acquiring the data until the blood in the target imaging region is sufficiently suppressed. Further, in order to shorten the time of the prescan 2, the number of encodes in the direction not selected in step S12 may be reduced.

[Step S14]
The data obtained by the prescan 2 and the data obtained by the prescan 1 are subjected to difference between the same encodings, and the difference data is subjected to 2D-Fourier transform for each encoding to reconstruct an image. The image thus obtained is, for example, an image of a slice plane when the encoding reduction direction is the slice direction Gs, and is displayed on the display unit 114 as an image for each encoding. FIG. 8 shows an example of the display screen. Here, in step S13, images of 6 encodings from encoding E=0 to 5 are picked up, and 6 difference images are displayed. FIG. 9 shows two actually captured head difference images. The left side of FIG. 9 is for the case of encoding E=0, and the right side is for the case of encoding E=5. As can be seen from these comparisons, the encoding E=5 has a better blood vessel depiction ability.

[Step S15]
The operator can select the encoding, that is, the band in which the target blood vessel rendering capability is the best, by comparing the displayed images, and sets this band as the offset amount from the encoding 0. As for the setting method, the displayed image may be selected, or as shown in FIG. 9, a numerical value may be input (selected).

[Step S16] to [Step S18]
When the offset amount is set via the input unit 114, main imaging is started with the set offset amount as the designated band. In the main imaging, the 3D-TOF imaging pulse sequence shown in FIG. 2 is executed under both conditions of no presaturation pulse (S16) and with presaturation pulse (S18). At this time, with respect to the direction designated in step S12, the thinning of the encoding is performed and the imaging is performed with the set offset amount. For example, when the data of one encoding is obtained by thinning out the encoding, only the band specified by the offset amount is acquired, and when the data of the predetermined number of encodes is acquired, the band specified by the offset amount (for example, , +5 and -5) as the center, and data of a plurality of encodings are acquired.

The imaging without presaturation pulse (S16) and the imaging with presaturation pulse (S18) may be performed continuously, but in the flow shown in FIG. 5, the stage where the imaging without presaturation pulse (S16) is completed. In step S17, the measurement is temporarily stopped and the operator's instruction is awaited. In this case, for example, as shown in FIG. 8, a “Continue” button for continuing the measurement and a “Stop” button for ending the measurement are displayed to wait for the operation of the operator. Alternatively, the push button of another device may be facilitated. By inserting step S17 as described above, the operation is shared with a known blood vessel imaging technique, DSA (Digital Subtraction Angiography), so that the operator can proceed with imaging in a familiar procedure. However, this procedure is not essential in this embodiment.

When the button for continuing the measurement is selected, the imaging control unit 401 executes the 3D-TOF imaging pulse sequence with presaturation pulse. The encoding at this time is also the designated band in the encoding reduction direction. In addition, when the position of the subject 101 is shifted after the imaging in step S16 and no meaningful information is obtained even after performing S18, the measurement may be stopped and step S16 may be repeated.

[Step S19]
The image reconstruction unit 403 subtracts the measurement data obtained by the imaging in steps S16 and S18 to create a difference image. The difference may be applied to the data before image reconstruction (RAW DATA) or to the reconstructed image. The display control unit 404 causes the display unit 113 to display the difference image. The display method is arbitrary. For example, only the difference image may be displayed, or the difference image may be a semitransparent color image and may be superimposed on the blood vessel image or the morphological image acquired in advance such as in step S11. .. This allows more intuitive confirmation of hemodynamics.

As described above, according to the MRI apparatus of the present embodiment, the images acquired by a plurality of encodings are presented, and the main imaging is performed by designating the encoding having the best blood vessel rendering ability. The number of encodings can be reduced to shorten the imaging time and improve the image quality.

In the above description, the imaging conditions such as TR and the encoding step width are matched between the prescan 1 executed in step S11 and the prescan 2 executed in step S13 to reduce the number of scans for acquiring the difference data. Although the case has been described, in the pre-scan 2, the imaging with and without the pre-saturation pulse may be performed. In that case, although the prescan time is extended, the prescan 2 is not limited by the imaging conditions of the prescan 1, so that the band can be changed more finely, and the optimum band can be found with high accuracy. be able to. Further, at this time, the TRs are matched between the imaging with and without the presaturation pulse, and the same presaturation pulse that does not affect the target imaging region even without the presaturation pulse is applied to the MT by the presaturation pulse. Since the (Magnification Transfer) effect can be matched in both imagings, it is possible to reduce signals such as skull parenchyma in the difference image. This can further improve the visibility of blood vessels.

<Second embodiment>
The present embodiment is characterized in that the restriction of presaturation position designation is added based on the configuration of the first embodiment. Since the functional block diagram shown in FIG. 4 is common, the operation of this embodiment will be described below with reference to the flow shown in FIG. Note that, in FIG. 10, processes having the same contents as those in FIG. 5 are denoted by the same reference numerals, and overlapping description will be omitted.

First, as in the first embodiment, prescan 1 is performed to display an image (S11). Looking at this image, the operator sets the image pickup area and the encoding reduction direction (S21). The excitation position of the presaturation pulse is not specified here yet. When the imaging region is designated by the frame 601 as shown in FIG. 6 and the direction in which the encoding is thinned (for example, the slice direction) is set, the calculation unit 108 excites the region overlapping the imaging region with the presaturation pulse. Restrict (S22). Therefore, for example, as shown in FIG. 6, a mark corresponding to the excitation profile (theoretical value) of the presaturation pulse is displayed as the presaturation positioning UI 602, and the positioning UI 602 is moved (rotated) to the position of the target blood vessel. Also includes) to determine the presaturation position. At this time, the movement range of the positioning UI 602 is limited so that the UI cannot be moved to a position overlapping the frame 601 that specifies the imaging region. The operator can set the target blood vessel to a position where it can be excited by moving the positioning UI 602 within the movable range or changing the angle (S23).

The actual excitation profile of the presaturation pulse may be broader than the theoretical value of the excitation profile used to create the positioning UI 602. In consideration of such a case, for example, a restriction may be provided so that an area having a predetermined size larger than the UI 602 does not overlap the imaging area.

Then, the pre-scan 2 of step S13 is performed at the pre-saturation position set in step S23. Next, the creation and display of the difference image (S14) and the band setting process (S15), and the main imaging and the image display with the set band as the offset amount (S16 to S19) are the same as in the first embodiment. is there. Note that the pre-saturation position is also the pre-saturation position set in step S23 for the main imaging.

According to the present embodiment, by limiting the pre-sallation excitation region so as not to overlap the imaging region, the difference image obtained in step S14 is an image of only blood vessels. As a result, it becomes easy to make a determination when determining the optimum band in which an image with excellent blood vessel rendering capability is obtained. Also, in the main imaging, an image with excellent blood vessel depiction ability can be obtained.

<Third embodiment>
In the first and second embodiments, the result of prescan (prescan 2) for band determination is displayed, and the operator determines the offset amount in the direction in which encoding is reduced in the main imaging based on the displayed result. However, in this embodiment, the apparatus analyzes the result of the prescan and determines the optimum band based on the result.

As shown in FIG. 11, the configuration of the arithmetic control system of the present embodiment is the same as that of the first embodiment except that the band setting unit 402 of the functional block diagram shown in FIG. 4 is replaced with a band calculating unit 405 for calculating the band by the system. Is the same as. Further, as shown in FIG. 12, the operation of the arithmetic control system of this embodiment is the same as that of the second embodiment except that steps S14 and S15 shown in FIG. 10 are replaced by difference data calculation step S24 and band calculation step S25. It is the same. Hereinafter, the present embodiment will be described focusing on the points different from the second embodiment.

First, after performing the prescan 1 and the image display (S11) for setting the image pickup area, the setting of the image pickup area and the encoding reduction direction is accepted (S12). After setting the presaturation restricted area, the setting of the presaturation position is accepted (S22, S23). The limitation of the presaturation position may be performed by limiting the movement of the positioning UI 602, as in the second embodiment. At this time, in consideration of the actual excitation profile, the positioning UI 602 may be provided in a region larger than the theoretical excitation profile.

Next, prescan 2 for band setting is performed for a predetermined encoding at the set presaturation position (S13), and the difference from prescan 1 is calculated for each encoding (S24). In the difference data, the presaturation region does not overlap the imaging region, and therefore only the signal from the blood vessel is dominant.

The band calculation unit 405 extracts the characteristic amount such as the peak intensity or the signal integrated value of the difference data of each encoding, and determines the encode that maximizes the peak intensity or the signal integrated value. These feature quantities are indicators of blood vessel visualization ability, and when these are the maximum, the blood vessel visualization ability is estimated to be the best, so the band calculation unit 405 sets this encoding to the optimum band, that is, the offset amount (S25). ). In order to improve the accuracy of the optimum band estimation, the difference data is Fourier-transformed into real-space data, and the scalp and skull that may become high signals are automatically clipped, and then the inverse Fourier transform is performed again to obtain k. It is also possible to return to the spatial data and estimate the optimum band based on the feature amount.

After that, the main imaging (S16 to S19) is performed with the set offset amount for the encoding reduction region, as in the first and second embodiments.

According to the present embodiment, by setting the limit on the presaturation position, the accuracy of the optimum band setting can be improved, and the optimum band is automatically set using the feature amount of the image obtained in the prescan 2. You can decide.

<Fourth Embodiment>
In the first to third embodiments, based on the result of the prescan (prescan 2) for band determination, the offset amount in the direction in which the encoding is reduced in the main imaging is set manually or automatically. The MRI apparatus of the embodiment automatically determines and determines the optimum band based on the imaged region set as the imaging condition without performing the pre-scan for band determination.

The configuration of the arithmetic control system of the present embodiment is the same as that of the functional block diagram shown in FIG. 10, but the relation between the site of the subject and the band is previously tabulated in the memory of the arithmetic control system or an external storage device. Store things. The relationship between the site of the subject and the band is a predetermined band having the highest ability to visualize the structure of each site for a plurality of sites having different fineness of structure.

The relationship between the part and the band will be described with reference to FIG. FIG. 13A is a diagram showing a tomographic image (xy cross section) of the brain 500 as an example, and the parenchyma 510 and blood vessels 520 of the brain are included in this image. The diameter of the blood vessel 520 is, for example, about 1 to 2 mm, but the structure of the brain parenchyma including the blood vessel is about 1 to 3 cm. In the graph on the right side of FIG. 13A (FIG. 13B), the vertical axis represents the y direction of the image, and the horizontal axis represents the signal intensities of blood vessels and brain parenchyma. When the signal represented by this graph is Fourier-transformed into k-space data as shown in FIG. 13C, the brain parenchyma signal exists in a relatively narrow band 511 with the center of the k-space interposed therebetween. , The blood vessel signal exists in a wider band 512. In the above example, the bandwidth of the brain parenchyma of 1 to 3 cm is 66.6 to 200 [m ⁻¹ ] and the bandwidth of the blood vessel of ¹ to 2 mm is 1000 to 2000 [m ⁻¹ ]. Therefore, when the k-space center is 0, the lower limit is 33.3 to 100 [m ⁻¹ ] and the upper limit is 500 to 1000 [m ⁻¹ ] where blood vessel signals and brain parenchymal signals are mixed. It is a difficult range, that is, a zone where blood vessels are dominant. Similarly, the range in which the lower limit is −1000 to −500 [m ⁻¹ ] and the upper limit is −100 to −33.3 [m ⁻¹ ] is a band where blood vessels are dominant.

In this way, the structure (for example, diameter) of the region and the band are obtained by Fourier transform, and the band corresponds to the encoding that defines the k-space. From this relationship, the optimum band or encoding of the region to be imaged The offset amount can be calculated. For example, the offset amount is an intermediate value in the range in which blood vessels are dominant, which is 300 [m ⁻¹ ] in the above example.

Based on the above description, the processing of the arithmetic control system of this embodiment will be described below. FIG. 14 shows a processing flow of the arithmetic control system. 14, steps having the same processing contents as those in FIGS. 5 and 10 are denoted by the same reference numerals, and overlapping description will be omitted.

[Step S11]
First, similarly to the first embodiment, prescan 1 is performed to display an image.

[Step S31]
The operator receives the setting of the imaging condition and the imaging region, the setting of the presaturation pulse position, and the setting of the direction for reducing the encoding. The method of setting the imaging region is not particularly limited, but the diameter of the target blood vessel and the target region are selected on the imaging condition setting screen (UI) of MRA as shown in FIG. 15, for example. Although only the diameter of the target blood vessel may be used, by designating the target site together, the size of the surrounding site and tissue can also be estimated, so that the band in which the target blood vessel is dominant can be accurately set in the next step.

[Step S32]
The band calculation unit 402 uses the imaged region set in step S31 and the table 450 representing the relationship between the region and the band stored in the storage device, and uses the band having the highest imaging capability of the imaged region (optimum). Bandwidth) is calculated and set as an offset amount.

[Steps S16 to S19]
After that, the main imaging is performed with the set offset amount in the set encoding reduction direction, the operation procedure (S17) similar to that of the DAS is appropriately adopted, and the difference image is created and displayed as in the first embodiment. Is.

According to the present embodiment, the optimum band is calculated and determined on the device side without performing the prescan, so that the imaging time can be shortened.

Also in the present embodiment, as in the second embodiment, a function of limiting the prescan area may be added. For example, steps S21 to S23 shown in FIG. 10 are added to step S31 of FIG. That is, the setting of the imaging region and the encoding reduction direction is accepted in the setting step S31 of the imaging condition and the imaging region by the operator (S21). If the encoding reduction direction is set, a range in which the presaturation position is restricted is calculated so that the imaging region and the presaturation position do not overlap in that direction (S22). This allows the operator to set the presaturation position at a position that does not overlap the imaging area (S23).

After that, the optimum band is calculated using the imaging region set in step S31 and the table 450 stored in the storage device, and the main imaging is performed using the calculated optimum band and the presaturation position set in step S23. What is performed (S16 to S19) is the same as the operation of the above-described fourth embodiment.

Although the respective embodiments of the present invention have been described above, these embodiments and their modifications can be appropriately combined unless technically contradictory. It is also included in the present invention that elements other than the arithmetic and control system are appropriately omitted or new elements are added. Further, in the above embodiments, the function of the arithmetic control system is described as the function performed by the arithmetic unit and the control unit of the MRI apparatus, but a part (function other than imaging) may be realized by an arithmetic apparatus other than the MRI apparatus. It is possible.

According to the present invention, in 3D-blood vessel imaging, an MRI apparatus capable of high-speed imaging by effectively acquiring a signal and a control method thereof are provided.

102: static magnetic field magnet, 103: gradient magnetic field coil, 104: RF coil, 105: RF probe, 106: signal detector, 107: signal processor, 108: calculator, 109: gradient magnetic field power supply, 110: RF transmitter. , 112: bed, 113: input unit, 114: display unit, 115: storage device, 401: imaging control unit, 402: band setting unit, 403: image reconstruction unit, 404: display control unit, 405: band calculation unit. ..

Claims (9)

An imaging unit that performs 3D blood vessel imaging using a presaturation pulse and collects 3D-k spatial data, an imaging condition setting unit that sets imaging conditions by the imaging unit, and a control unit that controls the operation of the imaging unit. And an input unit for accepting the designation of the k-space band by the operator ,
The conditions set by the imaging condition setting unit include a data direction setting for reducing the number of encodes of the 3D-k space data,
The control unit includes a band setting unit that sets a k-space band for acquiring data with respect to the data direction set by the imaging condition setting unit, and the band setting unit sets the k-space band received by the input unit. A magnetic resonance imaging apparatus, which is set as a condition for the 3D blood vessel imaging . An imaging unit that performs 3D blood vessel imaging using a presaturation pulse and collects 3D-k spatial data, an imaging condition setting unit that sets imaging conditions by the imaging unit, and a control unit that controls the operation of the imaging unit. And an input unit that receives input of information regarding an imaging region by an operator ,
The conditions set by the imaging condition setting unit include a data direction setting for reducing the number of encodes of the 3D-k space data,
The control unit includes a band setting unit that sets a k-space band for acquiring data in the data direction set by the imaging condition setting unit, and the band setting unit uses information received by the input unit. A magnetic resonance imaging apparatus, characterized in that a k-space band of the imaging region is determined and set as a condition for the 3D blood vessel imaging . The magnetic resonance imaging apparatus according to claim 2 , wherein
The magnetic resonance imaging apparatus characterized in that the information regarding the imaged region includes any of the name, size, diameter, and structural feature of the tissue to be removed from the imaged region or image. An imaging unit that performs 3D blood vessel imaging using a presaturation pulse and collects 3D-k spatial data, an imaging condition setting unit that sets imaging conditions by the imaging unit, and a control unit that controls the operation of the imaging unit. And a calculation unit that creates a difference image between 3D blood vessel imaging using presaturation pulses and 3D blood vessel imaging without presaturation ,
The conditions set by the imaging condition setting unit include a data direction setting for reducing the number of encodes of the 3D-k space data,
The control unit includes a band setting unit that sets a k-space band for acquiring data with respect to the data direction set by the imaging condition setting unit, and a predetermined band is set for the data direction set by the imaging condition setting unit. Controlling the imaging unit to perform 3D blood vessel imaging using a presaturation pulse for a plurality of encoded
The calculation unit creates, for each of the plurality of encodings, a difference image between the first 3D blood vessel imaging using the presaturation pulse and the second 3D blood vessel imaging without the presaturation, and displays the difference image on the display device. magnetic resonance imaging apparatus characterized by letting. An imaging unit that performs 3D blood vessel imaging using a presaturation pulse and collects 3D-k spatial data, an imaging condition setting unit that sets imaging conditions by the imaging unit, and a control unit that controls the operation of the imaging unit. And a calculation unit that creates a difference image between 3D blood vessel imaging using presaturation pulses and 3D blood vessel imaging without presaturation ,
The conditions set by the imaging condition setting unit include a data direction setting for reducing the number of encodes of the 3D-k space data,
The control unit includes a band setting unit that sets a k-space band for acquiring data with respect to the data direction set by the imaging condition setting unit, and has a predetermined direction for the data direction set by the imaging condition setting unit. Controlling the imaging unit to perform a first 3D blood vessel imaging using a presaturation pulse for a plurality of encodings;
The calculation unit creates difference data between the first 3D blood vessel imaging using the presaturation pulse and the second 3D blood vessel imaging without using the presaturation, for each of the plurality of encodes,
The magnetic resonance imaging apparatus , wherein the band setting unit determines the k-space band based on difference data of the plurality of encodes . The magnetic resonance imaging apparatus according to claim 5, wherein
The magnetic resonance imaging apparatus, wherein the band setting unit determines the k-space band using at least one of a peak intensity and a signal integration value of difference data of the plurality of encodes. The magnetic resonance imaging apparatus according to claim 4 or 5 , wherein
The second 3D blood vessel imaging is positioning imaging for determining an imaging region,
The magnetic resonance imaging apparatus, wherein the control unit controls the imaging unit to perform the positioning imaging at the same TR and encoding steps as the first 3D blood vessel imaging. The magnetic resonance imaging apparatus according to any one of claims 1 to 7 ,
The condition set by the imaging condition setting unit includes a presaturation position,
The magnetic resonance imaging apparatus, wherein the control unit controls the presaturation pulse position so as not to overlap the imaging region. The magnetic resonance imaging apparatus according to any one of claims 1 to 8 ,
The magnetic resonance imaging apparatus, wherein the presaturation pulse is a beam saturation pulse.

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