JP2010158459A - Magnetic resonance apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To collect, in a short photographing time, an echo for generating a blood vessel image using an in-flow effect and an echo for generating the blood vessel image using a T2* emphasis effect. <P>SOLUTION: The blood vessel image using the in-flow effect and the blood vessel image using the T2* emphasis effect are each generated by one or more echoes selected from among a plurality of echoes generated during a 1TR period. The blood vessel image using the T2* emphasis effect is generated by the echo having the sufficient T2* emphasis effect. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a magnetic resonance imaging apparatus that captures a blood flow image.

In a magnetic resonance imaging apparatus, a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field are formed in a space that accommodates an imaging target, magnetic resonance signals that generate spins of the imaging target are collected, and an image is generated based on the magnetic resonance signals. Magnetic resonance signals are collected as data that fills a two-dimensional (or higher dimensional) Fourier space, i.e., k-space, and is collected into two-dimensional (or higher dimensional) inverse Fourier. An image is generated (reconstructed) by the conversion.

As a sequence for imaging a blood flow image of an artery, a time-of-flight (TOF: Time) in which a strong signal can be obtained from blood flow flowing into the imaging section.
of Flight) method is often used (Patent Document 1). As a sequence for capturing a blood flow image, an FS-BB (Flow-Sensitive BB) method or the like is known (Patent Document 2). In addition, SWI (Susceptibility Weighted Imaging) technology for creating and displaying an image in which contrast of tissues having different magnetic susceptibility is enhanced using phase information of MR (Magnetic Resonance) data has been proposed (Patent Document 3). It has been applied to depict blood flow images of veins (Patent Document 2).

JP-A-5-154132 JP 2008-272248 A JP 2006-255046 A

However, the conventional sequence for capturing blood flow images of both arteries and veins has a problem that the imaging time becomes long.

Therefore, an object of one embodiment of the present invention is to capture blood flow images of both an artery and a vein in a short imaging time.

Another object of the present invention is to collect echoes for generating a blood vessel image using an inflow effect and echoes for generating a blood vessel image using a T2 * enhancement effect in a short imaging time. And

Another object of the present invention is to reduce the influence of displacement caused by movement of a subject.

Another object of the present invention is to generate images of arteries and veins with a high signal-to-noise ratio.

In one embodiment of the present invention, a blood vessel image using an inflow effect and a blood vessel image using a T2 * enhancement effect are each generated by one or more echoes selected from a plurality of echoes generated within a 1TR period. A blood vessel image using the T2 * enhancement effect is generated from an echo having a sufficient T2 * enhancement effect.

In another aspect of the invention,
A control unit that executes a pulse sequence for imaging including a plurality of readout gradient magnetic fields;
A data collection unit for collecting a plurality of echoes generated according to the plurality of readout gradient magnetic fields;
A data processing unit that generates a first blood vessel image using an inflow effect based on the plurality of echoes, and a second blood vessel image using a T2 * enhancement effect;
With
The pulse sequence is applied with the number of read gradient magnetic fields necessary to generate the inflation effect and the T2 * enhancement effect within the same TR period.
A magnetic resonance apparatus is provided.

In another aspect of the invention,
The data processing unit generates the first blood vessel image based on one or more echoes acquired with a short TE among the plurality of echoes.

In another aspect of the invention,
When generating the first blood vessel image based on the plurality of echoes, the data processing unit generates the blood vessel image by applying a weighting function to each echo.

In another aspect of the invention,
The first blood vessel image using the inflation effect is a blood vessel image having an artery as a region of interest.

In another aspect of the invention,
The data processing unit generates the second blood vessel image based on one or more echoes acquired with a long TE among the plurality of echoes.

In another aspect of the invention,
When generating the second blood vessel image based on the plurality of echoes, the data processing unit applies the weighting function to each echo to generate the second blood vessel image.

In another aspect of the invention,
The second blood vessel image using the T2 * enhancement effect is a blood vessel image having a vein as a region of interest.

In another aspect of the invention,
The data processing unit generates the first blood vessel image using at least one echo having a shorter TE than the echo used to generate the second blood vessel image, and generates the first blood vessel image. The second blood vessel image is generated using at least one echo having a longer TE than the echo to be used.

In another aspect of the invention,
The data processing unit uses one of the plurality of echoes for both the first blood vessel image and the second blood vessel image.

In another aspect of the invention,
The imaging pulse sequence is a three-dimensional imaging sequence.

In another aspect of the invention,
The control unit executes a saturation pulse sequence that saturates spins flowing from outside the imaging region.

In another aspect of the invention,
The imaging pulse sequence includes a phase compensation pulse of gradient moment nulling that suppresses signal loss of blood flow.

In another aspect of the invention,
Each of the plurality of readout gradient magnetic fields is a unipolar lead gradient magnetic field.

In another aspect of the invention,
Each of the plurality of readout gradient magnetic fields is a bipolar lead gradient magnetic field.

In another aspect of the invention,
The data processing unit applies the MIP method to the first blood vessel image and applies the MinIP method to the second blood vessel image to generate images in which blood vessels are emphasized.

In another aspect of the invention,
The data processing unit
A phase image corresponding to an image obtained from an echo generated according to the readout gradient magnetic field is generated,
By applying a filtering process to the phase image, a phase mask image representing a portion having a large phase shift and a portion having a small phase shift is generated,
By multiplying the image obtained from the echo by the phase mask image a predetermined number of times, an image in which the phase change due to the magnetic susceptibility is emphasized is generated, and the first or second based on the image in which the phase change is emphasized A blood vessel image is generated.

According to one embodiment of the present invention, it is possible to provide an apparatus that captures blood flow images of both an artery and a vein in a short imaging time.

According to another aspect of the present invention, echoes for generating a blood vessel image using the inflow effect and echoes for generating a blood vessel image using the T2 * enhancement effect are collected in a short imaging time. Can do.

According to another aspect of the present invention, it is possible to provide an apparatus that reduces the influence of displacement caused by the movement of a subject.

According to another aspect of the present invention, it is possible to provide a device that generates arterial and venous images having a high signal-to-noise ratio.

FIG. 1 is a configuration diagram showing a configuration of an MRI apparatus according to an embodiment of the present invention. FIG. 2 is a conceptual diagram illustrating an imaging pulse sequence used for imaging a blood vessel image using an inflation effect and a blood vessel image using a T2 * enhancement effect in a preferred embodiment of the present invention. FIG. 3 is a conceptual diagram illustrating an imaging pulse sequence used for imaging a blood vessel image using an inflation effect and a blood vessel image using a T2 * enhancement effect in a preferred embodiment of the present invention. FIG. 4 is a conceptual diagram for explaining a photographing slab and a saturation slice selected in photographing according to a preferred embodiment of the present invention. FIG. 5 is a schematic diagram for explaining a photographing slab and a saturation slice selected in photographing in a preferred embodiment of the present invention. FIG. 6 is a conceptual diagram illustrating a saturation pulse sequence used in a preferred embodiment of the present invention. FIG. 7 is a graph illustrating the weighting function applied to the vein image in the preferred embodiment of the present invention. FIG. 8 is a conceptual diagram illustrating a procedure for obtaining a phase mask processed image in which the phase change due to the magnetic susceptibility of the vein image is enhanced using the phase mask image.

Exemplary embodiments of a magnetic resonance imaging method and apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited thereby.

In FIG. 1, the static magnetic field magnet unit 12 is provided to form a static magnetic field in the static magnetic field space 11 in which the subject 40 is accommodated. The static magnetic field magnet unit 12 is a horizontal magnetic field type, and a superconducting magnet (not shown) is provided along the body axis direction of the subject 40 placed in the static magnetic field space 11 in which the subject 40 is accommodated. Create a static magnetic field. In addition to the horizontal magnetic field type, the static magnetic field magnet unit 12 may be a vertical magnetic field type or a permanent magnet.

The gradient coil unit 13 forms a gradient magnetic field in the static magnetic field space 11 so that the magnetic resonance signal received by the RF coil unit 14 has three-dimensional position information. The gradient coil unit 13 preferably includes three sets of coils for generating gradient magnetic fields in the X-axis direction, the Y-axis direction, and the Z-axis direction that are orthogonal to each other. The gradient driving unit 23 controls the pulse current supplied to each coil of the gradient coil unit 13 to synthesize the gradient magnetic fields in the three axes (X axis, Y axis, Z axis) directions that are physical axes. Each gradient magnetic field in the logical axis direction composed of the slice direction gradient magnetic field Gs, the phase direction gradient magnetic field Gp, and the frequency direction gradient magnetic field Gr orthogonal to each other can be arbitrarily set.

For example, the RF coil unit 14 is disposed so as to surround the entire head, which is an imaging region of the subject 40, and is configured to be used for both transmission and reception. The RF coil unit 14 transmits an RF signal, which is an electromagnetic wave, to the subject in the static magnetic field space 11 to form a high-frequency magnetic field, and excites proton spins in the imaging region of the subject 40. The RF coil unit 14 receives an electromagnetic wave generated from the excited proton as a magnetic resonance signal. The RF coil unit 14 may be provided so that the transmission coil and the reception coil are independent.

The RF drive unit 22 drives the RF coil unit 14 to form a high-frequency magnetic field in the static magnetic field space 11, and a gate modulator (not shown), an RF power amplifier (not shown), and an RF oscillator (not shown). And have. Based on the control signal from the control unit 30, the RF drive unit 22 modulates the RF signal from the RF oscillator into a signal having a predetermined timing and a predetermined envelope using a gate modulator. The RF signal modulated by the gate modulator is amplified by the RF power amplifier and then output to the RF coil unit 14.

The gradient driving unit 23 drives the gradient coil unit 13 based on a control signal from the control unit 30 to generate a gradient magnetic field in the static magnetic field space 11. The gradient drive unit 23 includes three systems of drive circuits (not shown) corresponding to the three systems of gradient coils of the gradient coil unit 13.

The data collection unit 24 includes a phase detector (not shown) and an analog / digital converter (not shown) in order to collect magnetic resonance signals received by the RF coil unit 14. The data collection unit 24 detects the phase of the magnetic resonance signal from the RF coil unit 14 using a phase detector using the output of the RF oscillator of the RF drive unit 22 as a reference signal, and outputs the detected signal to an analog / digital converter. Then, the magnetic resonance signal, which is an analog signal phase-detected by the phase detector, is converted into a digital signal by the analog / digital converter and output to the data processing unit 33.

The table 25 has a cradle 26 on which the subject 40 is placed. The table 25 moves the subject 40 placed on the cradle 26 between the inside and the outside of the accommodation space 11 based on a control signal from the control unit 30.

The control unit 30 includes a computer, a program that causes each unit to execute an operation corresponding to a predetermined scan (scan) using the computer, and a memory in which the program is loaded. The control unit 30 is connected to the operation unit 32, processes the operation signal input to the operation unit 32, and controls the RF drive unit 22, the gradient drive unit 23, the data collection unit 24, and the table 25. And a scanning processor which is a computer that outputs a control signal to perform control. Further, the control unit 30 controls the data processing unit 33 based on an operation signal from the operation unit 32 in order to obtain a desired image.

The storage unit 31 is configured by a storage device such as a hard disk device. The storage unit 31 stores the magnetic resonance data before the image image reconstruction process collected by the data collection unit 24, the image data subjected to the image image reconstruction process by the data processing unit 33, and the like.

The operation unit 32 is configured by an operation device such as a keyboard and a mouse, and outputs an operation signal corresponding to the operation of the operator to the control unit 30.

The data processing unit 33 is configured by a reconfiguration processor that is a computer. The data processing unit 33 is connected to the data collecting unit 24 and performs an image image reconstruction process on the magnetic resonance data output from the data collecting unit 24 to generate an image.

The display unit 34 includes a display device such as a display, and displays an image of the subject 40 generated by the data processing unit 33. Also, various windows for inputting various parameters such as scan parameters, which will be described later, are displayed on the display screen of the display unit 34.
<Pulse sequence>

FIG. 2 shows an imaging pulse sequence (pulse sequence) used for imaging arterial and venous blood flow images in a preferred embodiment of the present invention. In the figure, the first stage shows a gradient magnetic field Gr in the frequency direction, the second stage shows a gradient magnetic field Gp in the phase direction, the third stage shows a gradient magnetic field Gs in the slice direction, and the fourth stage shows a sequence of RF pulses. This pulse sequence is a gradient echo (GRE: Gradient).
Echo) is a pulse sequence based on the method. The pulse sequence proceeds from left to right along the time axis t. FIG. 2 shows a pulse sequence in one repetition time (1TR). In a preferred embodiment of the present invention, as will be described later, a predetermined change is applied to the gradient magnetic field in each direction, and this pulse sequence is repeated in a plurality of TR periods. Here, you may use the RF spoiling method which provides a different transmission phase to RF pulse for every repetition time.

As indicated by reference numeral 281 in the figure, α ° excitation of the spin is performed by the α ° pulse. At this time, a gradient magnetic field 270 is applied on the slice axis, and selective excitation is performed for a predetermined slice. FIG. 3 illustrates in greater detail the gradient field 270 on the slice axis applied in the preferred embodiment of the present invention. As shown in the figure, the gradient magnetic field 270 on the slice axis has a slice selection gradient magnetic field 271 and a slice refocusing gradient magnetic field 273. In this embodiment, in order to obtain a three-dimensional image of the imaging slab 311 shown in FIG. 4, the imaging slab 311 (in this example, 8 cm thick) is excited together. In this respect, it can be said that the imaging pulse sequence of FIG. 2 is a three-dimensional imaging sequence. Specifically, according to a known three-dimensional volume imaging method, a slab having a thickness of 8 cm is excited together by an RF pulse, and thereafter, a slice encoding gradient magnetic field 275 for giving position information in the slice direction is applied. A phenomenon in which the signal intensity of a fluid is lowered due to the presence of a spin that moves after application of an RF pulse is called a flow void. The gradient magnetic field 275 includes a gradient moment nulling phase compensation pulse component that prevents this flow void from occurring. By including the gradient moment nulling phase compensation pulse in the gradient magnetic field 275, zero-order and first-order moment nulling is performed, and signal loss of blood flow in the slice direction can be suppressed. In this example, as shown in FIG. 4, in order to obtain an axial image of the subject 40, the imaging slab 311 is selected. Then, the head of the subject 40 is selected as the imaging slab 311 for the purpose of acquiring images of arteries and veins in the brain of the subject 40. The present invention is not limited to the arteries and veins in the brain of the subject 40, and can be applied to imaging of other arteries and veins such as the abdominal aorta of the subject 40 and veins in the vicinity thereof. Further, the subject 40 is not limited to a human but may be other animals.

Returning to FIG. 2 and continuing the explanation, the gradient magnetic field 277 is a sum of a killer pulse for spoiling the transverse magnetization and a slice rewinder gradient magnetic field with respect to the slice encode gradient magnetic field 275. .

After the α ° pulse excitation, the phase encoding of the spin is performed by the gradient magnetic field 261 on the phase axis. In addition, a gradient moment nulling phase compensation pulse 211 is applied on the frequency axis, then the spin is dephased by the gradient magnetic field 213 on the frequency axis, and then a series of readout gradient magnetic fields 231 to 246 are applied. To generate a gradient echo. Here, due to the inflow effect, the blood flow signal flowing from outside the imaging region becomes a higher signal than the signal generated in the stationary tissue. As will be described later, a blood flow signal flowing from a specific region can be suppressed by applying a saturation pulse to a region outside the region of interest. As a result, the blood flow signal of the vein due to the inflow effect cannot be drawn, and the blood flow of the artery can be drawn. Similarly to the phase compensation pulse 275 applied to the slice axis, the phase compensation pulse 211 can suppress the signal loss of the blood flow in the frequency direction.

Gradient echoes are generated in response to the readout gradient magnetic fields 231 to 246 in FIG. In this example, there are 16 lead-out gradient magnetic fields 231 to 246, and each corresponding TE (echo) in 1TR period.
16 gradient echoes occur at (time). In this example, each readout gradient magnetic field 231 to 246 has the same shape. In this example, a so-called monopolar (monopolar) type readout gradient magnetic field is used, but instead of this, a bipolar (bi−) in which the readout gradient magnetic field is periodically inverted between positive and negative. A polar-type readout gradient magnetic field can also be used. In this example, 16 continuous readout gradient magnetic fields 231 to 246 are applied, but one readout gradient magnetic field for the first blood vessel image (hereinafter simply referred to as “TOF image”) by the inflow effect is provided. After applying the above, the application of the readout gradient magnetic field is stopped, and one or more readout gradient magnetic fields for the second blood vessel image by T2 * enhancement (hereinafter simply referred to as “T2 * enhancement image”) are applied after a predetermined time has elapsed. It can also be applied.

The gradient echo is collected as raw data by the data collection unit 24. In this example, data of a total thickness of 8 cm is collected for 40 slices at 2 mm intervals. If this thickness (8 cm thick) is large, signal decrease accompanying a decrease in the inflow effect occurs on the downstream side of the blood flow, so that it is also possible to divide the target region into a plurality of thin slabs. The collected raw data is divided into raw data used to reconstruct a TOF image and raw data used to reconstruct a T2 * weighted image by a process described later. 33 is processed by each processing method.

The gradient magnetic field 215 on the frequency axis in FIG. 2 is a killer pulse for spoiling transverse magnetization, and the gradient magnetic field 263 on the phase axis is a phase rewinder gradient magnetic field with respect to the phase encode gradient magnetic field 261.

Such a pulse sequence is repeated until the three-dimensional k-space is filled with a period TR (repetition time) (for example, 40 × 256 = 10240 is repeated when acquiring data for 40 slices / 256 views). . At each repetition, the phase encoding gradient magnetic field 261, the rewinder pulse 263, the slice encoding gradient magnetic field in the gradient magnetic field 275, and the slice rewinder gradient magnetic field in the gradient magnetic field 277 are changed, and different encoding is performed each time. As a result, 16 sets of three-dimensional k-space data are obtained for each echo.
<Saturation>

In the case where only the arterial blood flow is depicted in the first blood vessel image without depicting the venous blood flow, as shown schematically in FIG. 5, the region into which the vein flows (saturation slice, Saturation (saturation) of the spin of FIG. 4, reference number 313).

Saturation is performed using a pulse sequence (saturation pulse sequence) as shown in FIG. As shown in the figure, the saturation slice is selectively excited by a 90 ° pulse and a gradient magnetic field to the slice axis Gs, and then, for example, a gradient magnetic field is applied to the frequency axis Gr to disperse the spin phase.

As a result, it is possible to prevent the venous blood flowing from the saturation slice into the imaging slab from generating a gradient echo. By adding such a saturation pulse sequence before the pulse sequence shown in FIG. 2, an image of venous blood flow can be blocked. When imaging is performed by dividing the imaging region into a plurality of slabs, a saturation slice can be set on the vein inflow side of the imaging slab in each imaging.
<Image reconstruction>

Data obtained by the pulse sequence of FIG. 2 is collected in the memory (k space) of the data processing unit 33. The data processing unit 33 reconstructs a three-dimensional image of the subject 40 by performing three-dimensional inverse Fourier transform on the k-space data. The data processing unit 33 further adds the three-dimensional image in a specific direction (for example, the slice direction) to generate a tomographic image in which blood vessels are displayed in a three-dimensional manner.

In a preferred embodiment of the present invention, image reconstruction is performed from two echoes corresponding to the readout gradient magnetic fields 231 and 232, respectively, and the obtained images are added to obtain a TOF image. Also, image reconstruction is performed from 12 consecutive echoes corresponding to the readout gradient magnetic fields 235 to 246, and the obtained images are added to obtain a T2 * weighted image. Alternatively, image reconstruction is performed from six consecutive echoes corresponding to the readout gradient magnetic fields 231 to 236, and the obtained images are added to obtain a TOF image. Further, image reconstruction is performed from 14 consecutive echoes corresponding to the readout gradient magnetic fields 233 to 246 that overlap with this range, and the obtained images are added to obtain a T2 * weighted image. In other words, one echo generated by the sequence of FIG. 2 may be used for the TOF image or may be used for the T2 * weighted image, depending on the selection. Needless to say, the two may be sorted so that all echoes obtained by imaging are used, such as 4 echoes for the TOF image and 12 echoes for the T2 * weighted image. It should be noted that the echoes used need not be continuous, for example, three consecutive echoes corresponding to the readout gradient magnetic fields 232, 234, 237 and continuous corresponding to the readout gradient magnetic fields 239, 241, 244, 245. A TOF image or a T2 * weighted image can be generated by the four echoes. That is, when n echoes are collected sequentially over time, the TOF image can be generated from one or more of the 1st to n−1th echoes, and the T2 * weighted image is the second one. It can be generated from one or more of the n th echoes.

However, the blood flow due to the inflow effect has a higher signal intensity immediately after excitation. Therefore, an echo having a short elapsed time (TE) from the application of the RF pulse 281, that is, an echo generated by the readout gradient magnetic field 231 and the readout gradient magnetic fields 231 to 234 located near the readout gradient magnetic field 231 is generated. Suitable for reconstruction of TOF images. Further, by using the saturation pulse described above together, it is possible to reconstruct an arterial image in which the artery has a higher signal strength than the surrounding tissue due to the inflation effect.

The data processing unit 33 reconstructs a tomographic image (arterial image) of the imaging target 40 by performing inverse Fourier transform on k-space data corresponding to each short TE echo (arterial echo). The reconstructed image is stored in the memory. At this stage, the reconstructed image can also be displayed on the display unit 34.

On the other hand, blood degradation products such as deoxy-hemoglobin promote T2 * as TE becomes longer, causing a decrease in signal. For this reason, the T2 * weighted image can reflect the difference in magnetic susceptibility in the contrast as TE becomes longer. Therefore, when an image is reconstructed by combining echoes having an elapsed time (TE) from the application of the RF pulse 281 of 25 ms to 45 ms, preferably longer than 30 ms, an image with a reduced vein signal can be obtained. That is, the T2 * weighted image is an image (vein image) in which veins are differentiated from other tissues.

In a preferred embodiment of the present invention, echoes (venous echoes) generated by readout gradient magnetic fields 235-246 with TE longer than 30 ms are used for vein images. Also in the case of reconstruction of a vein image, the data processing unit 33 reconstructs a tomographic image of the imaging target 40 by performing inverse Fourier transform on k-space data corresponding to each vein echo. The reconstructed image is stored in the memory. At this stage, the reconstructed image can also be displayed on the display unit 34.

As described above, in the present invention, two types of images depicting the artery and the vein can be obtained from the echoes collected in one imaging (in the 1TR period), and efficient imaging can be performed. Further, since two types of images can be collected by a series of pulse sequences, there is no problem of displacement due to the movement of the subject 40, and an image when the subject 40 is substantially in the same state can be obtained. The echo used for the reconstruction of the TOF image is called “arterial echo”, and the readout gradient magnetic field corresponding to this “arterial echo” is called “arterial readout gradient magnetic field”. Similarly, an echo used for image reconstruction using a T2 * weighted image is referred to as a “venous echo”, and a readout gradient magnetic field corresponding to the “venous echo” is referred to as a “venous readout gradient magnetic field”. To do.

The TOF image depicts arterial blood flow white (high luminance value) and black background (low luminance value). In the preferred embodiment of the present invention, the images obtained from each reconstructed arterial echo are added to form a single arterial image. Thereafter, image processing by the maximum projection method (MIP method: Maximum Intensity Projection) is applied to the added image to generate an arterial image in which the artery is emphasized. The SN ratio of the image can be improved by adding the two images. The image in which the artery is emphasized is stored in the memory and displayed on the display unit 34.

On the other hand, the vein image by T2 * enhancement depicts the blood flow of the vein in black (low luminance value). In the preferred embodiment of the invention, the 12 reconstructed images are summed into a single vein image. Thereafter, image processing based on a minimum projection method (MinIP method) is applied to the added vein image to generate a vein image in which the vein is emphasized. By adding the images, the SN ratio of the images can be improved.

Further, as described above, T2 * is promoted as TE becomes longer. For this reason, in the preferred embodiment of the present invention, the weighting curve (weighting function) 300 shown in FIG. 7 is used, and T2 * increases the specific gravity of the further promoted vein image and lowers the vein signal. The SN ratio of the whole vein image is improved. That is, the weighting function 300 is a function that is set so that a higher weight is applied as the time during which the vein readout gradient magnetic field corresponding to each of the plurality of vein echoes is applied increases. The weighting function 300 may be a linear function having a predetermined slope, a parabolic curve, or the like.

Similar to the vein image, when an arterial image is generated based on a plurality of echoes, an arterial image can be generated by applying a weighting function to each echo according to the degree of the inflow effect in each echo.

In the present invention, the vein image is generated by the above-described reconstruction processing of the T2 * emphasized image. However, the magnetization of the vein image by the T2 * enhancement is optionally used by using a phase mask image similar to the SWI. It is also possible to obtain a vein image in which the phase change due to the rate is further enhanced. This procedure will be described with reference to FIG.

That is, using some or all of the 12 echoes generated by the readout gradient magnetic fields 235 to 246, the data processing unit 33 generates a phase image 401 corresponding to the image 405 by T2 * enhancement by a well-known method. Can do. Next, the data processing unit 33 generates a phase mask image 403 representing a portion with a large phase shift and a portion with a small phase shift from the phase image 401. This phase mask image 403 is an image in which the absolute value of the pixel value of the portion where the phase shift is large on the phase image is high and the pixel of the portion where there is no phase difference is set to zero. The phase mask image 403 can be generated by filtering the phase image 401 and removing the phase disturbance of low frequency components. Examples of the filter include a high-pass filter. The data processing unit 33 multiplies the image 405 by T2 * enhancement by the phase mask image 403 a predetermined number of times (one to several times) to obtain a phase mask processed image 407 in which the phase change due to the magnetic susceptibility is further enhanced. Thereafter, the phase mask processed images 407 obtained from the vein echoes are added, and image processing by the minimum projection method is applied to the obtained vein images to generate a phase mask processed image 409 that emphasizes the veins. The phase mask processed image 409 in which the vein is emphasized is also stored in the memory and displayed on the display unit 34.

In a preferred embodiment of the present invention, arterial images and vein images are generated by combining appropriate echoes from a plurality of obtained echoes. For this reason, after confirming the arterial image and the vein image on the display unit 34, the operator changes the number and / or range of echoes used to generate one or both images, and regenerates these images. It can also be created. In this case, there is no need to perform a new shooting, the k-space data stored in the memory is specified according to the number and / or range selected by the operator, and the above-described procedure is performed using the specified k-space data. Thus, an arterial image and / or a vein image can be recreated.

In a preferred embodiment of the present invention, an artery image (including an artery image and an artery image with an artery enhanced) and a vein image (a vein image, a vein image with a vein enhanced, a phase masked image, and a vein are further provided. (Including the emphasized phase mask processed image) is displayed as a separate image on the display unit 34, but both can be combined and displayed. In this case, it is desirable to perform scaling correction and contrast correction so that both or one of the images is suitable for synthesis. In addition, prior to synthesis, a process for facilitating the discrimination between the two, such as coloring a vein blue and an artery red, can be performed.

As mentioned above, although demonstrated centering on the suitable Example of this invention, the thought of this invention is not limited to this Example, A various deformation | transformation form is employable.

1: MRI apparatus 11: Static magnetic field space 12: Static magnetic field magnet unit 13: Gradient coil unit 14: RF coil unit 22: RF drive unit 23: Gradient drive unit 24: Data collection unit 25: Table 26: Cradle 30: Control unit 31: Storage unit 32: Operation unit 33: Data processing unit 34: Display unit 40: Subject

Claims (16)

A control unit that executes a pulse sequence for imaging including a plurality of readout gradient magnetic fields;
A data collection unit for collecting a plurality of echoes generated according to the plurality of readout gradient magnetic fields;
A data processing unit that generates a first blood vessel image using an inflow effect based on the plurality of echoes, and a second blood vessel image using a T2 * enhancement effect;
With
The pulse sequence is applied with the number of read gradient magnetic fields necessary to generate the inflation effect and the T2 * enhancement effect within the same TR period.
Magnetic resonance device. The data processing unit generates the first blood vessel image based on one or more echoes acquired in a short TE among the plurality of echoes.
The magnetic resonance apparatus according to claim 1. The data processing unit generates the blood vessel image by applying a weighting function to each echo when generating the first blood vessel image based on the plurality of echoes.
The magnetic resonance apparatus according to claim 2. The first blood vessel image using the inflow effect is a blood vessel image having an artery as a region of interest.
The magnetic resonance apparatus according to claim 1. The data processing unit generates the second blood vessel image based on one or more echoes acquired in a long TE among the plurality of echoes.
The magnetic resonance apparatus according to claim 1. The data processing unit generates the second blood vessel image by applying a weighting function to each echo when generating the second blood vessel image based on the plurality of echoes.
The magnetic resonance apparatus according to claim 5. The second blood vessel image using the T2 * enhancement effect is a blood vessel image having a vein as a region of interest.
The magnetic resonance apparatus according to claim 1. The data processing unit generates the first blood vessel image using at least one echo having a shorter TE than the echo used to generate the second blood vessel image, and generates the first blood vessel image. The magnetic resonance apparatus according to claim 1, wherein the second blood vessel image is generated by using at least one echo having a longer TE than an echo to be used. The data processing unit uses one of the plurality of echoes for both the first blood vessel image and the second blood vessel image.
The magnetic resonance apparatus according to claim 1. The imaging pulse sequence is a three-dimensional imaging sequence.
The magnetic resonance apparatus according to claim 1. The control unit executes a saturation pulse sequence that saturates spins flowing from outside the imaging region.
The magnetic resonance apparatus according to claim 1. The imaging pulse sequence includes a phase compensation pulse of gradient moment nulling that suppresses signal loss of blood flow.
The magnetic resonance apparatus according to claim 1. Each of the plurality of readout gradient magnetic fields is a unipolar lead gradient magnetic field,
The magnetic resonance apparatus according to claim 1. Each of the plurality of readout gradient magnetic fields is a bipolar lead gradient magnetic field,
The magnetic resonance apparatus according to claim 1. The data processing unit applies an MIP method to the first blood vessel image, applies a MinIP method to the second blood vessel image, and generates an image in which blood vessels are emphasized, respectively. A magnetic resonance apparatus according to claim 1. The data processing unit
A phase image corresponding to an image obtained from an echo generated according to the readout gradient magnetic field is generated,
By applying a filtering process to the phase image, a phase mask image representing a portion having a large phase shift and a portion having a small phase shift is generated,
By multiplying the image obtained from the echo by the phase mask image a predetermined number of times, an image in which the phase change due to the magnetic susceptibility is emphasized is generated, and the first or second based on the image in which the phase change is emphasized Generating blood vessel images,
The magnetic resonance apparatus according to claim 1.