JP5336731B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention measures nuclear magnetic resonance (hereinafter referred to as `` NMR '') signals from hydrogen, phosphorus, etc. in a subject and images nuclear density distribution, relaxation time distribution, etc. The present invention relates to sensitivity correction of an RF receiving coil in an apparatus called “MRI”.

  The MRI device measures NMR signals (echo signals) generated by the spins of the subject, especially the tissues of the human body, and forms the shape and function of the head, abdomen, limbs, etc. in two or three dimensions. It is a device that images. In imaging, the echo signal is given different phase encoding depending on the gradient magnetic field and is frequency-encoded and measured as time-series data. The measured echo signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.

  In such an MRI apparatus, the echo signal emitted from the subject is a high-frequency magnetic field, and this high-frequency magnetic field is detected by an RF receiving coil that is a type of a high-frequency antenna surrounding the subject. The RF receiving coil is required to have high sensitivity over a wide area and to detect an echo signal with a high S / N ratio. For example, a saddle type coil, a slotted tube resonator (hereinafter abbreviated as STR), a multiple element resonator (hereinafter referred to as MER, also referred to as a bird cage resonator), a solenoid coil, and the like are used. In addition, a circular coil or the like is also used for spinal or local use.

Regarding MER, for example, (Patent Document 1) and (Patent Document 2) disclose detailed configurations, and the structure of these RF receiving coils has been studied so that sensitivity distribution data is as uniform as possible on the image. Yes.

JP 61-95234 A JP-A-60-132547 JP 2002-315731 A JP 2000-268204 A

  However, in the RF receiving coil, there is generally a trade-off relationship between the S / N ratio of the received echo signal and the width of its sensitivity region. That is, in order to improve the S / N ratio of the received echo signal, it is necessary to narrow the sensitivity region. If the sensitivity region is widened, the S / N ratio of the received echo signal decreases. Therefore, the sensitivity area of the RF receiving coil cannot be expanded without limit. Therefore, in a practical RF receiving coil, the width of the sensitivity region is not necessarily sufficient as compared with the image region, and the sensitivity distribution may not be designed uniformly on the image. This tendency is particularly remarkable in the neck, spine, and head coils. In such a case, in the obtained image, the low sensitivity area becomes dark on the display, resulting in uneven brightness, and image information is not sufficiently displayed.

  As a method of correcting the non-uniformity of the sensitivity distribution of the RF receiver coil, the sensitivity distribution data of the RF receiver coil is acquired in advance before the main measurement for acquiring the image data, and is used to obtain a uniform distribution. A method of correcting image data so as to obtain a proper luminance distribution is known (Patent Document 3).

In this method, sensitivity distribution data (hereinafter referred to as reference data) I of the RF receiver coil is first obtained by imaging a human body equivalent phantom. ₀ Get (x, z). This reference data is given as a function of an image space (for example, x and z planes). Then, the original image data I (x, z) acquired by this RF receiving coil is used as reference data I corresponding to the sensitivity distribution data of this RF receiving coil. ₀ Image data I ′ (x, z) after sensitivity correction is obtained using (x, z). That is,
I '(x, z) = I (x, z) / I ₀ (x, z) (1)
As a result, the luminance nonuniformity of the image data is corrected, and the corrected image data has a substantially uniform luminance.

  In order to shorten the entire imaging time, it is desired that the acquisition time of the reference data is as short as possible. As one method, sensitivity distribution data is acquired with a size smaller than the image data, and this is used as image data. The reference data is enlarged to the same size. However, if the reference data is simply enlarged and the sensitivity is corrected as it is due to inhomogeneous static magnetic field, a sufficient effect may not be obtained.

  Therefore, an object of the present invention is to provide an MRI apparatus that can always perform accurate sensitivity correction even if the data sizes of sensitivity distribution data and image data are different.

In order to achieve the above object, the MRI apparatus of the present invention is configured as follows. That is,
The first RF receiving coil and the second RF receiving coil are provided, a measurement control means for measuring an echo signal from the subject, and a diagnostic image of the subject from the echo signal received by the second RF receiving coil An arithmetic processing unit for obtaining the sensitivity distribution data of the second RF receiving coil using the sensitivity images of the two RF receiving coils, and the luminance distribution of the diagnostic image using the sensitivity distribution data It performs sensitivity correction calculation for correcting the measurement control means, as the matrix size of the sensitivity image of the two RF receiving coil Naru rather smaller than the matrix size of the diagnostic image, for sensitivity image of the two RF receiving coils the echo signal is measured, processing means, and larger than the matrix size of the matrix size a diagnostic image of the sensitivity distribution data, and performs sensitivity correction calculation.

  According to the MRI apparatus of the present invention, accurate sensitivity correction can always be performed even if the data sizes of sensitivity distribution data and image data are different. As a result, the sensitivity distribution data acquisition time can be shortened, and the total inspection time can be shortened.

  Hereinafter, each embodiment of the MRI apparatus of the present invention will be described with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.

  First, an outline of an example of the MRI apparatus of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of an example of the MRI apparatus of the present invention. This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject, and as shown in FIG. 1, a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, and a reception system 6 And a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8.

  The static magnetic field generation system 2 generates a uniform static magnetic field in the space around the subject 1 in the direction of the body axis or in the direction perpendicular to the body axis. The permanent magnet method or the normal conduction method is provided around the subject 1 Alternatively, a superconducting static magnetic field generating means (not shown) is arranged.

  A gradient magnetic field generation system (gradient magnetic field generation means) 3 is composed of a gradient magnetic field coil 9 wound in three axial directions of X, Y, and Z, and a gradient magnetic field power source 10 that drives each gradient magnetic field coil 9. The gradient magnetic field power supply 10 of each coil is driven in accordance with a command from the sequencer 4 to apply gradient magnetic fields in the X, Y, and Z directions to the subject 1. More specifically, a slice selection gradient magnetic field pulse (Gs) is applied in one of X, Y, and Z directions to set a slice plane for the subject 1, and a phase encoding gradient magnetic field pulse is applied in the remaining two directions. (Gp) and a frequency encoding (or reading) gradient magnetic field pulse (Gf) are applied to encode position information in each direction into an echo signal.

  The transmission system 5 irradiates an RF pulse to cause nuclear magnetic resonance to the nuclear spins of atoms constituting the biological tissue of the subject 1, and includes a high frequency oscillator 11, a modulator 12, a high frequency amplifier 13, and a transmission side And a high frequency coil (RF transmission coil) 14a. The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at a timing according to a command from the sequencer 4, and the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1. By supplying to the RF transmission coil 14a, the subject 1 is irradiated with electromagnetic waves (RF pulses).

  The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil (RF receiving coil) 14b on the receiving side and an amplifier 15 And a quadrature phase detector 16 and an A / D converter 17. The MRI apparatus of the present invention, as an RF receiving coil 14a, an RF receiving coil for whole body having a substantially uniform sensitivity region over a wide range, and an RF suitable for imaging a specific part of a subject such as the head, cervical vertebra, and knee. A reception coil and a local coil such as a surface coil or an array coil formed by arranging the surface coil in an array are provided, and one or more suitable RF reception coils are selected and imaging is performed. After the response electromagnetic wave (NMR signal) of the response of the subject 1 induced by the electromagnetic wave irradiated from the RF transmission coil 14a is detected by the RF reception coil 14b arranged close to the subject 1 and amplified by the amplifier 15 Then, the signals are divided into two orthogonal signals by the quadrature phase detector 16 at a timing according to a command from the sequencer 4, converted into digital quantities by the A / D converter 17, and sent to the signal processing system 7.

  The sequencer 4 is measurement control means for controlling the measurement of echo signals by repeatedly applying a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) and a gradient magnetic field pulse in a predetermined sequence. The sequencer 4 operates under the control of the CPU 8 and sends various commands for measuring echo signals necessary for the reconstruction of the tomographic image of the subject 1 to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6. By controlling these systems, echo signal measurement is controlled.

  The signal processing system 7 includes an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 made up of a CRT or the like. When the echo signal data from the receiving system 6 is input to the CPU 8, the CPU 8 (calculation The processing means) performs arithmetic processing such as signal processing and image reconstruction, and displays the tomographic image of the subject 1 as a result on the display 20 and records it on the magnetic disk 18 of the external storage device. The CPU 8 includes a memory corresponding to the K space, and stores echo signal data. Hereinafter, the description of arranging the echo signal data in the K space means that the echo signal data is written and stored in this memory.

  The operation system 25 is used to input various control information of the MRI apparatus and control information of processing performed in the signal processing system 7, and includes a trackball or mouse 23 and a keyboard 24. The operation system 25 is arranged close to the display 20, and the operator interactively controls various processes of the MRI apparatus through the operation system 25 while looking at the display 20.

  In FIG. 1, the RF receiving coils 14a and 14b and the gradient magnetic field coil 9 on the transmitting side and the receiving side are installed in the static magnetic field space of the static magnetic field generating system 2 arranged in the space around the subject 1. Yes.

  Currently, the spin target species for imaging of the MRI apparatus is proton, which is the main constituent of the subject, as widely used in clinical practice. By imaging the spatial distribution of proton density and the relaxation phenomenon in the excited state, the form or function of the human head, abdomen, limbs, etc. is imaged two-dimensionally or three-dimensionally.

(First embodiment)
Next, a first embodiment of the MRI apparatus of the present invention will be described. In this embodiment, the sensitivity of the RF receiving coil is corrected by making the image size of the reference data of the RF receiving coil larger than the image size of the diagnostic image data. Hereinafter, the present embodiment will be described in detail based on the processing flow of the present embodiment shown in FIGS. FIG. 2 is a flowchart showing a processing flow, and FIG. 3 is a diagram schematically showing each processing.

  In step 201, a sensitivity image Iw (x, z) of the whole-body RF receiving coil is acquired. The operator sets the whole-body RF receiving coil for both transmission and reception. Based on the setting, the sequencer 4 performs transmission / reception using only the whole-body RF receiving coil and images the subject. Preferably, the same cross section as a diagnostic image described later is captured. Then, the CPU 8 acquires a sensitivity image of the whole-body RF receiving coil using the echo signal measured by imaging.

  When acquiring the sensitivity image, preferably, the image matrix of the sensitivity image is made smaller than the image matrix of the diagnostic image to shorten the imaging time for acquiring the sensitivity image. For example, when the diagnostic image matrix is 256 × 256, the imaging time can be shortened to 1/16 to 1/8 than the imaging time of the diagnostic image by setting the sensitivity image matrix to 16 × 16 or 32 × 32. This sensitivity image matrix may be changed according to the degree of change in sensitivity distribution of the whole-body RF receiving coil and the RF receiving coil in the next step. When the degree of change in the sensitivity distribution is small, the number of matrices may be small, and when the degree of change is large, the number of matrices may be large. FIG. 3 shows a sensitivity image 201 of the RF receiver coil for whole body. This sensitivity image 201 is an example acquired with a matrix size of a x b (a, b are powers of 2, for example, 16, 32, 64, etc.).

  Further, the sequence used for sensitivity image acquisition is not particularly limited, but preferably, in order to measure the echo signal in which only the sensitivity distribution data of the RF receiving coil is reflected while eliminating the influence of the static magnetic field inhomogeneity, A spin-echo sequence is suitable. When using a spin echo sequence, for example, TR = 100 msec TE = 10 msec, phase encoding number 32, frequency encoding number 32, FOV is wider than the region of interest of the subject and narrower than the sensitivity range of the RF receiving coil, 30 cm 2D or 3D imaging is performed.

  In step 202, a sensitivity image Ic (x, z) of the RF receiving coil is acquired. The operator sets the whole body RF receiving coil as the transmitting coil, attaches the desired RF receiving coil (for example, knee coil) to the subject, performs imaging using these RF coils, and the sensitivity of the RF receiving coil Get an image. Preferably, the same cross section as a diagnostic image described later is captured. At the time of imaging, preferably, the matrix size of the sensitivity image of the RF receiver coil is set to the same matrix size as the sensitivity image of the RF receiver coil for whole body in step 201, and the same sequence as when acquiring the sensitivity image of the whole body RF receiver coil The image is taken using. FIG. 3 shows a sensitivity image 202 of the RF receiving coil. This sensitivity image 202 is an example acquired with the same matrix size a x b as the sensitivity image of the RF receiver coil for whole body.

In step 203, RF receiver coil sensitivity distribution data Sc (x, z) is acquired. The CPU 8 divides the sensitivity image Ic (x, z) of the RF receiving coil acquired in step 202 by the sensitivity image Iw (x, z) of the RF receiving coil for whole body acquired in step 201 (203), From these ratios, the RF receiver coil sensitivity distribution data Sc (x, z) is obtained:

Sc (x, z) = Ic (x, z) / Iw (x, z)

FIG. 3 shows the sensitivity distribution data Sc (x, z) 204 of the RF receiving coil. This sensitivity distribution data Sc (x, z) 204 is an example acquired with the same matrix size axb as the whole body RF receiving coil and the sensitivity image of the RF receiving coil.

In step 204, reference data I ₀ (x, z) is obtained from the sensitivity distribution data Sc (x, z) obtained in step 203. The CPU 8 sets the image size of the sensitivity distribution data Sc (x, z) to be larger than the image size of the diagnostic image I (x, z) acquired in the next step 205, and the reference data I ₀ (x, z) Ask for 209. The obtained RF receiving coil reference data I ₀ (x, z) 209 is stored in an external storage device such as the magnetic disk 18. Details of this step will be described later.

  In step 205, a diagnostic image I (x, z) of the subject is acquired using the RF receiving coil. Using the RF receiving coil set in step 202, the operator images a desired cross section of the subject and obtains a diagnostic image thereof. The sequence used for imaging and its imaging parameters can be set arbitrarily, and this embodiment is not particularly limited. FIG. 3 shows an example of the diagnostic image 205. This diagnostic image is an example acquired with a matrix size AXB (A and B are powers of 2, for example, 128, 256, and 512).

In step 206, the sensitivity correction of the diagnostic image I (x, z) acquired in step 205 is performed using the reference data I ₀ (x, z) obtained in step 204. The CPU 8 corrects the sensitivity of the diagnostic image I (x, z) 205 by dividing I (x, z) 205 by I ₀ (x, z) 209 (210) based on the above equation (1). To obtain a corrected diagnostic image 211 having a uniform luminance distribution. FIG. 3 shows a diagnostic image 211 whose luminance has been corrected. The matrix size of the diagnostic image 211 after the brightness correction is the same as AXB as the diagnostic image 205.

Next, details of the processing for obtaining the reference data I ₀ (x, z) in step 204 will be described.
In step 204-1, the matrix size of the sensitivity distribution data is expanded. The matrix size of the sensitivity distribution data Sc (x, z) 204 obtained in step 203 is that the matrix size of the original sensitivity image 201 is generally larger than the matrix size of the diagnostic image I (x, z) 205. Since it is acquired with a small size, the CPU 8 enlarges the matrix size of the sensitivity distribution data 204 to an extent applicable to the matrix size of the diagnostic image 205. Conventionally, the matrix size of the sensitivity distribution data has been expanded so that the matrix size is the same as the matrix size of the diagnostic image, but in this embodiment, the CPU 8 is configured to be larger than the matrix size of the diagnostic image 205. The matrix size of the sensitivity distribution data 204 is expanded. For example, if the matrix size of the diagnostic image I (x, z) 205 is (AXB), the matrix size of the sensitivity distribution data Sc (x, z) 204 is

(A + σx) X (B + σz)

And That is, the x direction is enlarged by {(A + σx) / A} times, and the z direction is enlarged by {(B + σz) / B} times. Here, σx and σz are enlargement parameters, and the filtering parameters in the next step are used. The sensitivity distribution data in which the matrix size is enlarged is Sc ′ (x, z). FIG. 3 shows an example of the enlarged sensitivity distribution data 206. The matrix size of the expansion sensitivity distribution data 206 is as described above.

In step 204-2, a filtering operation (F) is performed on the expanded sensitivity distribution data to suppress the end value of the sensitivity distribution data. The CPU 8 multiplies the sensitivity distribution data Sc ′ (x, z) expanded in step 205-1 by the following Gaussian function f (x, z) 207 (205):
F {Sc ′ (x, z)} = Sc ′ (x, z) f (x, z)
f (x, z) = exp {-x ² / (2σx) − z ² / (2σz)} (2)
This Gaussian function f (x, 2) 207 is a function that decreases as the value of (x, z) increases, so by filtering this function, the end of the sensitivity distribution data with the matrix size expanded The value of is properly suppressed. FIG. 3 shows the Gaussian function f (x, z) 207 of the above equation (2) and the sensitivity distribution data F {Sc ′ (x, z)} 208 after filtering. The sensitivity distribution data 208 after filtering has the same matrix size (A + σx) X (B + σz) as the expanded sensitivity distribution data 206, but the values at the ends are suppressed by filtering. By performing this filtering, the occurrence of ringing artifacts can be suppressed.

In step 204-3, reference data I ₀ (x, z) is extracted from the filtered sensitivity distribution data. The CPU 8 extracts sensitivity distribution data having the same matrix size as that of the diagnostic image 205 from the central portion of the filtered sensitivity distribution data F {Sc ′ (x, z)} 208, and uses this as reference data I ₀ (x, z) 209. FIG. 3 shows the reference data I ₀ (x, z) 209. The matrix size of the reference data I ₀ (x, z) 209 is AXB which is the same as that of the diagnostic image 205.

  The above is the description of the processing flow of the present embodiment. In addition, the execution order of each step demonstrated with the said processing flow is not restricted to said order. Either step 201 or 202 may be performed first. In short, it is only necessary that the sensitivity images of both receiving coils have been acquired before step 203. Step 205 may be any step before step 206.

  As described above, according to the MRI apparatus of the present embodiment, the sensitivity distribution data having the sensitivity information of the RF receiving coil is enlarged after being enlarged larger than the diagnostic image of the subject, and the reference data and the diagnostic image 2 are filtered. By matching the two image data, accurate sensitivity correction can always be performed even if the size of the image data changes between the sensitivity distribution data acquisition and the image data acquisition. As a result, the sensitivity distribution data acquisition time can be shortened, and the total inspection time can be shortened.

(Second embodiment)
Next, a second embodiment of the MRI apparatus of the present invention will be described. In this embodiment, in the first embodiment, when the acquisition of a diagnostic image is performed by synchronous imaging (for example, electrocardiography or respiratory synchronization) in accordance with the movement of the subject, the sensitivity distribution data of the RF receiving coil In the acquisition, the same synchronous imaging is performed. Hereinafter, the present embodiment will be described in detail based on the processing flow of the present embodiment shown in FIG.

  In step 401, a desired imaging time phase is set. For example, the operator sets a desired imaging time phase via the imaging time phase setting GUI displayed on the display 20.

  In the case of ECG-synchronized imaging, the operator selects a desired point in time on the ECG waveform displayed on the display 20 with a mouse or the like, and the CPU 8 captures the delay time from the R wave at the selected point in time. Set as time phase. Alternatively, a window for inputting the delay time from the R wave is displayed on the display 20, the operator sets the delay time on the window, and the CPU 8 sets the delay time set by the operator as the imaging time phase. Also good.

  Further, in the case of respiratory synchronous imaging, a known navigator echo is acquired to monitor respiratory motion, and a waveform representing the respiratory motion is displayed on the display 20. When the operator selects a desired state with a mouse or the like on the respiratory motion waveform, the CPU 8 sets the selected respiratory motion state as the imaging time phase. Alternatively, since the amplitude of the respiratory motion fluctuates, the operator may designate a desired width that sandwiches the desired state, and the CPU 8 may set the width as the imaging time phase.

  In step 402, imaging is started and the body movement time phase is monitored. The sequencer 4 starts imaging in a predetermined sequence and acquires a signal (electrocardiogram waveform, navigator echo, etc.) indicating the body movement state of the subject. Then, the CPU 8 monitors the body movement of the subject from the acquired signal indicating the body movement state, and detects the body movement time phase. For example, in the case of electrocardiographic synchronization imaging, the CPU 8 monitors the electrocardiographic waveform. If it is respiratory synchronization imaging, the CPU 8 analyzes the navigator echo and monitors the respiratory motion state.

  In step 403, a desired body movement time phase is detected. The CPU 8 compares the desired imaging time phase set in step 401 with the body motion time phase detected in step 402, and determines whether or not the detected body motion time phase is a desired time phase. If it is the same time phase, the process proceeds to step 404, and if it is different, the process returns to step 402 and the detection of the body movement time phase is continued.

  At step 404, each image of the RF receiving coil is acquired. The sequencer 4 activates a predetermined sequence, performs body motion synchronization imaging, and acquires a sensitivity image and a diagnostic image of the RF receiving coil. Since this step performs the same processing as steps 201, 202, and 205 in FIG. 1, detailed description thereof is omitted.

  In step 405, the CPU 8 determines whether or not sufficient data necessary for image reconstruction is measured in the imaging in step 404. This is body motion synchronized imaging, and the sequencer 4 measures necessary data only in a desired time phase, so there are cases where all data cannot be measured in one time phase. In such a case, the process returns to step 404 to measure unmeasured data. Then, the CPU 8 repeats Step 404 until data necessary and sufficient for image reconstruction is measured.

  In step 406, sensitivity correction of the diagnostic image is performed. The CPU 8 reconstructs a diagnostic image using each image data acquired in step 404 and corrects its sensitivity. Since this step performs the same processing as steps 203, 204, and 206 in FIG. 1, detailed description thereof is omitted.

  The processing flow of this embodiment has been described so far.

As described above, according to the MRI apparatus of the present embodiment, even when performing body motion synchronization imaging of the subject, the same effects as in the first embodiment described above are not affected by the body motion of the subject. Can be obtained.
(Third embodiment)
Next, a third embodiment of the MRI apparatus of the present invention will be described. In this embodiment, in the first embodiment, the sensitivity distribution data of the whole-body RF receiving coil and the RF receiving coil is acquired in three dimensions, and sensitivity correction is performed on the diagnostic image using the three-dimensional reference data. It is. Hereinafter, the present embodiment will be described in detail based on the processing flow of the present embodiment shown in FIG.

  In step 501, the sequencer 4 activates a predetermined three-dimensional sequence to acquire a three-dimensional sensitivity image of the whole-body RF receiving coil. This corresponds to performing step 201 in FIG. 1 three-dimensionally, and the rest is the same as step 201, and thus detailed description thereof is omitted.

  In step 502, the sequencer 4 activates a predetermined three-dimensional sequence to acquire a three-dimensional sensitivity image of the RF receiving coil. This is equivalent to performing step 202 in FIG. 1 in three dimensions, and the other steps are the same as step 202, and thus detailed description thereof is omitted.

  In step 503, the CPU 8 acquires three-dimensional sensitivity distribution data of the RF receiving coil. This corresponds to performing step 203 in FIG. 1 three-dimensionally, and the rest is the same as step 203, and thus detailed description thereof is omitted.

  In step 504, the operator sets a desired two-dimensional imaging section in the three-dimensional space. As a setting method, for example, a method disclosed in Patent Document 4 can be used.

  In step 505, the sequencer 4 captures the diagnostic image of the imaging section set in step 504 using the RF receiving coil. This is equivalent to performing step 205 in FIG. 1 with the imaging section set in step 504, and the rest is the same as step 205, and thus detailed description thereof is omitted.

  In step 506, the CPU 8 determines the imaging cross section set in step 504 from the three-dimensional sensitivity image of the RF receiver coil for whole body acquired in step 501 and the three-dimensional sensitivity image of the RF receiver coil acquired in step 502. Each sensitivity image is acquired. For this purpose, a known MPR (Multi-Planer-Reconstruction) method can be used. Then, the CPU 8 acquires sensitivity distribution data of the RF receiving coil from the sensitivity image data in the imaging section of the whole-body RF receiving coil and the sensitivity image data in the imaging section of the RF receiving coil.

  In step 507, the CPU 8 acquires reference data from the sensitivity distribution data of the RF receiving coil acquired in step 506, and performs sensitivity correction of the diagnostic image of the same imaging cross section acquired in step 505 using this reference data. Since this step is the same as steps 204 and 206 in FIG. 1, detailed description thereof is omitted.

  In step 508, when the operator performs imaging of another imaging cross section, the operator returns to step 504 and repeats the processing of steps 504 to 507.

  The processing flow of this embodiment has been described so far. In the above description, the sensitivity distribution data of the RF receiving coil is obtained for each photographing section, and the example of performing the filtering of the expression (2) after expanding this is described. However, the three-dimensional sensitivity distribution data is expanded in three dimensions. You may perform 3D filtering later.

  As described above, according to the MRI apparatus of the present embodiment, if the same RF receiving coil and the same part of the same subject are to be imaged in order to acquire three-dimensional sensitivity distribution data, the imaging cross section Even if this is changed, it is not necessary to re-read the sensitivity distribution data, and the total imaging time can be shortened.

1 is an overall configuration diagram of an MRI apparatus to which the present invention is applied. The figure which shows the processing flow of 1st Embodiment. FIG. 3 is a diagram schematically showing each process in the process flow of FIG. The figure which shows the processing flow of 2nd Embodiment. The figure which shows the processing flow of 3rd Embodiment.

Explanation of symbols

  1 subject, 2 static magnetic field generation system, 3 gradient magnetic field generation system, 4 sequencer, 5 transmission system, 6 reception system, 7 signal processing system, 8 central processing unit (CPU), 9 gradient magnetic field coil, 10 gradient magnetic field power supply, 11 High-frequency transmitter, 12 modulator, 13 high-frequency amplifier, 14a high-frequency coil (transmitting coil), 14b high-frequency coil (RF receiving coil), 15 signal amplifier, 16 quadrature detector, 17 A / D converter, 18 magnetic disk , 19 Optical disc, 20 Display, 21 ROM, 22 RAM, 23 Trackball or mouse, 24 Keyboard, 51 Gantry, 52 Table, 53 Housing, 54 Processing device

Claims (5)

A measurement control means comprising a first RF receiving coil and a second RF receiving coil, and measuring an echo signal from the subject;
Arithmetic processing means for acquiring a diagnostic image of the subject from an echo signal received by the second RF receiving coil,
The arithmetic processing means obtains sensitivity distribution data of the second RF receiver coil using the sensitivity images of the two RF receiver coils, and corrects the luminance distribution of the diagnostic image using the sensitivity distribution data. A magnetic resonance imaging apparatus for performing computation,
The measurement control means such that said matrix size of sensitivity image of the two RF receiving coil Naru rather smaller than the matrix size of the diagnostic image, and measuring the echo signals for sensitivity image of the two RF receiving coils,
The magnetic resonance imaging apparatus, wherein the arithmetic processing means performs the sensitivity correction calculation with a matrix size of the sensitivity distribution data larger than a matrix size of the diagnostic image. The magnetic resonance imaging apparatus according to claim 1.
The measurement control means measures echo signals for the sensitivity image and the diagnostic image of the two RF receiving coils for each body movement time phase of the subject,
The magnetic resonance imaging apparatus, wherein the arithmetic processing means performs the sensitivity correction calculation for each body movement time phase of the subject. The magnetic resonance imaging apparatus according to claim 1.
Before Symbol measurement control unit, said two for sensitivity image of the RF receiving coil and an echo signal for the diagnostic image is measured respectively 3D,
The magnetic resonance imaging apparatus, wherein the arithmetic processing means performs the sensitivity correction calculation for each desired cross section of a three-dimensional diagnostic image. The magnetic resonance imaging apparatus according to any one of claims 1 to 3,
The magnetic resonance imaging apparatus, wherein the arithmetic processing means performs a filtering operation for compressing an end value of the sensitivity distribution data larger than a matrix size of the diagnostic image. The magnetic resonance imaging apparatus according to claim 4.
The arithmetic processing unit determines a filter function for performing the filtering operation according to an enlargement ratio that makes the matrix size of the sensitivity distribution data larger than the matrix size of the diagnostic image, and performs the filtering operation. Magnetic resonance imaging apparatus.

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