JP2013240589A - Apparatus and method for magnetic resonance imaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality while performing the high-speed image taking process.SOLUTION: A magnetic resonance imaging apparatus includes: a sequence controlling unit that, by controlling an execution of a pulse sequence, acquires magnetic resonance (MR) signals corresponding to a plurality of channels in the pulse sequence executed as a series, the MR signals being configured to be arranged into a first region of a k-space at first intervals and into a second region larger than the first region at second intervals larger than the first intervals; an arranging unit that arranges the MR signals corresponding to the channels into the k-space as k-space data; and an image generating unit that generates first-interval k-space data corresponding to the channels based on the second-interval k-space data acquired by executing the pulse sequence and generates a magnetic resonance image based on the generated first-interval k-space data, the first-interval k-space data acquired by executing the pulse sequence, and sensitivity distributions corresponding to the channels.

Description

  Embodiments relate to a magnetic resonance imaging apparatus and method.

  In magnetic resonance imaging, the nuclear spin of a subject placed in a static magnetic field is magnetically excited with an RF (Radio Frequency) pulse at its Larmor frequency, and a magnetic resonance signal ( Hereinafter, an imaging method for appropriately generating an image from “MR (Magnetic Resonance) signal”).

  Conventionally, a parallel imaging (PI) method is known as one of high-speed imaging methods. In general, in the PI method, the imaging time is shortened by thinning and collecting k-space data. Since a folded image is generated from the thinned k-space data, the PI method uses the difference in sensitivity between the channels for k-space data collected in a plurality of channels having different sensitivities. Reconstruct an image without However, when the thinning rate (hereinafter referred to as “PIF (PI Factor)” as appropriate) is increased, the SNR (Signal Noise Ratio) decreases, so there is a certain limit to high-speed imaging. In addition, since there is a limit in PIF, there is a certain limit in improving time resolution.

Magnetic Resonance in Medicine 42; 952-962, Pruessmann K.P. et al, 1999 Magnetic Resonance in Medicine 47; 1202-1210, Griswold M.A. et al, 2002

  The problem to be solved by the present invention is to provide a magnetic resonance imaging apparatus capable of improving the image quality under high-speed imaging.

  The magnetic resonance imaging apparatus according to the embodiment includes a sequence control unit, an arrangement unit, and an image generation unit. The sequence control unit controls the execution of the pulse sequence, and is arranged at a first interval in the first region of the k space, and in a second region wider than the first region at a second interval wider than the first interval. Magnetic resonance signals for a plurality of arranged channels are collected in a pulse sequence executed in series. The arrangement unit arranges the magnetic resonance signals for the plurality of channels in k-space as k-space data. The image generation unit generates k-space data of the first interval for a plurality of channels based on the k-space data of the second interval collected by the execution of the pulse sequence, and the generated k-space data of the first interval and A magnetic resonance image is generated based on the k-space data at the first interval collected by the execution of the pulse sequence and the sensitivity distribution for a plurality of channels.

FIG. 1 is a functional block diagram showing the configuration of the MRI apparatus according to the first embodiment. FIG. 2 is a diagram for explaining an image generation method according to the first embodiment. FIG. 3A is a view for explaining an image generation method according to the first embodiment. FIG. 3B is a view for explaining an image generation method according to the first embodiment. FIG. 4 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 5 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 6 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 7 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 8 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 9 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 10 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 11 is a diagram for explaining a phase encoding pattern in the first embodiment. FIG. 12 is a diagram for explaining segmentation of k space in the second embodiment. FIG. 13 is a diagram for explaining an imaging scan in the second embodiment. FIG. 14 is a diagram for explaining an imaging scan in the third embodiment. FIG. 15 is a diagram for explaining an example of image generation according to the third embodiment. FIG. 16 is a diagram for explaining an imaging scan in a modified example of the third embodiment. FIG. 17 is a diagram for explaining changes in the signal value of an artery in the fourth embodiment. FIG. 18 is a diagram for explaining an imaging scan according to the fourth embodiment. FIG. 19 is a diagram for explaining an example of image generation according to the fourth embodiment. FIG. 20 is a diagram for explaining an example of a moving image according to the fourth embodiment. FIG. 21 is a diagram for explaining an imaging scan in a modification of the fourth embodiment. FIG. 22 is a view for explaining an imaging scan in the fifth embodiment. FIG. 23 is a diagram for explaining an imaging scan in a modification of the fifth embodiment. FIG. 24 is a view for explaining an imaging scan in the sixth embodiment. FIG. 25 is a diagram for explaining an imaging scan in Modification 1 of the sixth embodiment. FIG. 26 is a diagram for explaining an imaging scan in Modification 2 of the sixth embodiment. FIG. 27 is a view for explaining an imaging scan in Modification 3 of the sixth embodiment.

  Hereinafter, a magnetic resonance imaging apparatus and method according to embodiments will be described with reference to the drawings. In addition, it is not restricted to the following embodiment.

(First embodiment)
FIG. 1 is a functional block diagram showing the configuration of the MRI apparatus 100 according to the first embodiment. As shown in FIG. 1, the MRI apparatus 100 includes a static magnetic field magnet 101, a static magnetic field power supply 102, a gradient magnetic field coil 103, a gradient magnetic field power supply 104, a bed 105, a bed control unit 106, and a transmission coil 107. , A transmission unit 108, a reception coil array 109, a reception unit 110, a sequence control unit 120, and a computer 130. The MRI apparatus 100 does not include a subject P (for example, a human body). Moreover, the structure shown in FIG. 1 is only an example. For example, the sequence control unit 120 and each unit in the computer 130 may be configured to be appropriately integrated or separated.

  The static magnetic field magnet 101 is a magnet formed in a hollow cylindrical shape, and generates a static magnetic field in an internal space. The static magnetic field magnet 101 is, for example, a superconducting magnet or the like and is excited by receiving a current supplied from the static magnetic field power source 102. The static magnetic field power supply 102 supplies a current to the static magnetic field magnet 101. The static magnetic field magnet 101 may be a permanent magnet. In this case, the MRI apparatus 100 may not include the static magnetic field power source 102. In addition, the static magnetic field power source 102 may be provided separately from the MRI apparatus 100.

The gradient magnetic field coil 103 is a coil formed in a hollow cylindrical shape, and is disposed inside the static magnetic field magnet 101. The gradient coil 103 is formed by combining three coils corresponding to the X, Y, and Z axes orthogonal to each other, and these three coils individually supply current from the gradient magnetic field power supply 104. In response, a gradient magnetic field is generated in which the magnetic field strength varies along the X, Y, and Z axes. The gradient magnetic fields of the X, Y, and Z axes generated by the gradient coil 103 are, for example, a slice encode gradient magnetic field G _SE (or a slice selective gradient magnetic field G _SS ), a phase encode gradient magnetic field G _PE , and a frequency encode gradient. Magnetic field _GRO . The gradient magnetic field power supply 104 supplies a current to the gradient magnetic field coil 103.

  The couch 105 includes a top plate 105a on which the subject P is placed. Under the control of the couch control unit 106, the couch 105a is placed in a state where the subject P is placed on the cavity ( Insert it into the imaging port. Usually, the bed 105 is installed so that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 101. The couch controller 106 drives the couch 105 under the control of the computer 130 to move the couchtop 105a in the longitudinal direction and the vertical direction.

  The transmission coil 107 is arranged inside the gradient magnetic field coil 103 and receives a supply of RF pulses from the transmission unit 108 to generate a high-frequency magnetic field. The transmission unit 108 supplies an RF pulse corresponding to a Larmor frequency determined by the type of target atom and the magnetic field strength to the transmission coil 107.

  The reception coil array 109 is arranged inside the gradient magnetic field coil 103 and receives MR signals emitted from the subject P due to the influence of the high-frequency magnetic field. When receiving MR signal, receiving coil array 109 outputs the received MR signal to receiving section 110. In the first embodiment, the receiving coil array 109 has one or more, typically a plurality of coil elements.

  The transmission coil 107 and the reception coil array 109 described above are only examples. What is necessary is just to comprise by combining one or more among the coil provided only with the transmission function, the coil provided only with the reception function, or the coil provided with the transmission / reception function.

  The receiving unit 110 detects the MR signal output from the receiving coil array 109 and generates MR data based on the detected MR signal. Specifically, the receiving unit 110 generates MR data by digitally converting MR signals output from the receiving coil array 109. In addition, the reception unit 110 transmits the generated MR data to the sequence control unit 120. The receiving unit 110 may be provided on the gantry device side including the static magnetic field magnet 101, the gradient magnetic field coil 103, and the like.

  Here, in the first embodiment, MR signals output from the coil elements of the reception coil array 109 are output to the reception unit 110 in units called channels or the like by being appropriately distributed and combined. For this reason, MR data is handled for each channel in subsequent processing after the receiving unit 110. The relationship between the total number of coil elements and the total number of channels may be the same, when the total number of channels is small with respect to the total number of coil elements, or conversely, the total number of channels is large with respect to the total number of coil elements In some cases. In the following, when notation such as “each channel” or “each channel”, the processing may be performed for each coil element, or may be performed for each channel in which the coil elements are distributed and combined. Indicates good. Note that the timing of distribution / combination is not limited to the timing described above. MR signals or MR data may be distributed and combined in units of channels before processing by the control unit 133 described later.

  The sequence control unit 120 performs imaging of the subject P by driving the gradient magnetic field power source 104, the transmission unit 108, and the reception unit 110 based on the sequence information transmitted from the computer 130. Here, the sequence information is information defining a procedure for performing imaging. The sequence information includes the strength of the current supplied from the gradient magnetic field power source 104 to the gradient magnetic field coil 103 and the timing of supplying the current, the strength of the RF pulse supplied from the transmission unit 108 to the transmission coil 107, the timing of applying the RF pulse, and reception. The timing at which the unit 110 detects the MR signal is defined. For example, the sequence control unit 120 is an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), or an electronic circuit such as a central processing unit (CPU) or a micro processing unit (MPU).

  The sequence control unit 120 drives the gradient magnetic field power source 104, the transmission unit 108, and the reception unit 110 to image the subject P. As a result, when receiving MR data from the reception unit 110, the sequence control unit 120 sends the received MR data to the computer 130. Forward.

  The computer 130 performs overall control of the MRI apparatus 100, generation of MR images, and the like. The computer 130 includes an interface unit 131, a storage unit 132, a control unit 133, an input unit 134, a display unit 135, and an image generation unit 136. In addition, the control unit 133 includes an arrangement unit 133a.

  The interface unit 131 transmits sequence information to the sequence control unit 120 and receives MR data from the sequence control unit 120. Further, when receiving the MR data, the interface unit 131 stores the received MR data in the storage unit 132. The MR data stored in the storage unit 132 is arranged in the k space by the arrangement unit 133a. As a result, the storage unit 132 stores k-space data for a plurality of channels.

  The storage unit 132 stores MR data received by the interface unit 131, k-space data arranged in the k space by the arrangement unit 133a, image data generated by the image generation unit 136, and the like. For example, the storage unit 132 is a RAM (Random Access Memory), a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like.

  The input unit 134 receives various instructions and information input from the operator. The input unit 134 is, for example, a pointing device such as a mouse or a trackball, a selection device such as a mode change switch, or an input device such as a keyboard. The display unit 135 displays various information such as spectrum data and image data under the control of the control unit 133. The display unit 135 is a display device such as a liquid crystal display.

  The control unit 133 performs overall control of the MRI apparatus 100. Specifically, the control unit 133 generates sequence information based on imaging conditions input from the operator via the input unit 134, and controls the imaging by transmitting the generated sequence information to the sequence control unit 120. To do. The control unit 133 also controls image generation performed based on the MR data, and controls display on the display unit 135. In addition, the placement unit 133a reads the MR data generated by the reception unit 110 from the storage unit 132 and places it in the k space. For example, the control unit 133 is an integrated circuit such as an ASIC or FPGA, or an electronic circuit such as a CPU or MPU.

  The image generation unit 136 reads the k-space data arranged in the k-space by the arrangement unit 133a from the storage unit 132, and performs an reconstruction process such as Fourier transform on the read k-space data to generate an MR image.

  In addition, if the flow of the whole imaging by the MRI apparatus 100 described above is briefly described, in a certain examination, for example, the MRI apparatus 100 precedes an imaging scan that collects k-space data for generating a diagnostic image. Perform a preparatory scan. In this preparation scan, for example, a scan for collecting profile data indicating the sensitivity of each channel in the arrangement direction, a scan for collecting a positioning image, and a scan for collecting a sensitivity map indicating the sensitivity distribution of each channel. , A scan for collecting spectrum data for obtaining the center frequency of the RF pulse, a scan for obtaining a current value to be passed through a correction coil (not shown) for adjusting the uniformity of the static magnetic field, etc. Selected and done. In addition, as described in the second and subsequent embodiments, a scan for obtaining imaging parameters used in the imaging scan may be performed as the preparation scan.

  After these preparatory scans are performed, imaging scans are performed to collect k-space data for generating diagnostic images. Then, the MRI apparatus 100 generates an MR image using the k-space data stored in the storage unit 132. As will be described later, the image generation unit 136 according to the first embodiment generates an MR image using the sensitivity map collected in the preparation scan and the k-space data collected in the imaging scan. Note that, for example, the sensitivity map only needs to be collected before the image generation process, and thus does not necessarily have to be collected prior to the imaging scan.

  Next, an image generation method will be described with reference to FIGS. 2 and 3A to 3B. 2 and 3A to 3B are diagrams for explaining a method of generating an image according to the first embodiment. Note that the image generation method in the first embodiment can also be applied to the other embodiments other than the first embodiment. Further, the description of the k-space data described below is similarly applied to each of the other embodiments other than the first embodiment.

  First, k-space data to be subjected to image generation processing in the first embodiment will be described. In the first embodiment, the sequence control unit 120 controls the execution of the pulse sequence by the PI method, so that the sequence control unit 120 is arranged in the first region of the k space at the first interval, and in the second region wider than the first region. The k-space data arranged at the second interval wider than the first interval is collected for a plurality of channels. The k-space may be two-dimensional, three-dimensional, or other dimensional k-space.

  In the first embodiment, PIF = 2 is arranged in the central part of the k-space of 256 × 256 (or 256 × 256 × 256), and PIF = 4 is arranged in the whole including the peripheral part. An example of k-space data will be described, but this is only an example. For example, k-space data arranged in other PIFs, k-space data arranged in three or more types of PIFs, k-space data in which a part of k-space is zero-padded, and the like are also targeted. be able to. In the first embodiment, a pattern in which only the phase encoding direction is thinned out without thinning out the frequency encoding direction and the slice encoding direction will be described. However, the embodiment is not limited to this. For example, the phase encoding direction and the slice encoding direction can be appropriately changed, such as thinning out both. In the first embodiment, the PIF is set so that the second interval is an integral multiple of the first interval. However, the embodiment is not limited to this. The relationship between the two intervals may not be an integral multiple, and a value other than an integer may be used as the PIF. In addition, it is not necessarily limited to the relationship that the interval between the center portions (low frequency regions) is narrower than the interval between the peripheral portions (high frequency regions).

  Based on such k-space data, the overall flow of the image generation process will be briefly described first. As shown in FIG. 2, the image generation unit 136 uses the k-space data for a plurality of channels arranged at PIF = 4 in the whole including the peripheral portion among the k-space data stored in the storage unit 132. Then, an intermediate MR image is generated (step S01). Note that the MR image generated in step S01 is referred to as an “intermediate MR image” in order to distinguish it from the final output MR image.

  Next, the image generation unit 136 inversely reconstructs the intermediate MR image generated in step S01, thereby generating k-space data for a plurality of channels arranged with PIF = 2 over the entire periphery including the peripheral part. (Step S02). Then, the image generation unit 136 generates a final output MR image based on the PIF = 2 k-space data generated in step S02, the actually collected k-space data, and the sensitivity map for a plurality of channels. (Step S03). Note that the image generation unit 136 may perform image processing such as MIP (Maximum Intensity Projection) or MPR (Multi Planer Reconstruction) on the final output MR image.

  Such image generation processing will be described in detail with reference to FIGS. 3A and 3B. In the description of FIGS. 3A and 3B, three channels are assumed as a plurality of channels. However, the embodiment is not limited to this, and an arbitrary number of channels may be used. 3A and 3B, a two-dimensional k-space is illustrated for convenience of explanation, but the same can be applied to a three-dimensional k-space.

  3A and 3B, the sensitivity maps for a plurality of channels are collected by a preparation scan or the like under the control of the sequence control unit 120. 3A and 3B, the k-space data for a plurality of channels is collected by an imaging scan under the control of the sequence control unit 120, and is arranged in the k-space by the arrangement unit 133a. That is, the k-space data is arranged with PIF = 2 at the center of the k-space having a size of 256 × 256 (or 256 × 256 × 256), and arranged with PIF = 4 in the whole including the peripheral portion.

  As shown in (a) of FIG. 3A, the image generation unit 136 includes a plurality of channels of k-space data stored in the storage unit 132 for a plurality of channels arranged with PIF = 4 on the whole including the peripheral portion. Are read out as processing targets. Next, as illustrated in (b) of FIG. 3A, the image generation unit 136 reconstructs k-space data with PIF = 4 for each channel, and generates a folded image for a plurality of channels. Subsequently, as illustrated in (c) of FIG. 3A, the image generation unit 136 applies the sensitivity map of each channel to each folded image of each channel, and performs the unfolding process of the PI method, thereby performing intermediate processing. An MR image is generated.

  Next, as illustrated in (d) of FIG. 3B, the image generation unit 136 applies each of the sensitivity maps of each channel to the generated intermediate MR image, so that the sensitivity of each channel is reflected (( After generating the second (second) intermediate MR image, each generated (second) intermediate MR image is reversely reconstructed to generate k-space data for a plurality of channels. For example, the image generation unit 136 applies the sensitivity map of each channel to each pixel in the intermediate MR image shown in FIG. 3B (c), and obtains a weighted (second) intermediate MR image for a plurality of channels. Generate. Since the (second) intermediate MR image is an unfolded image, the image generation unit 136 performs the folding (weight according to the weight determined depending on the phase of the position where the data is arranged in the k space. (The weight is determined from the discrete Fourier transform formula). Then, the image generation unit 136 generates k-space data for a plurality of channels arranged by PIF = 2 in the whole including the peripheral part by thinning out the k-space data of each channel.

  Subsequently, as illustrated in FIG. 3B (e), the image generation unit 136 combines the generated PIF = 2 k-space data and the actually collected k-space data to include the entire peripheral portion. Are generated, and k-space data of PIF = 2 for a plurality of channels is generated. This combination may be an overwriting process using actually collected k-space data, or a weighting process for both. Next, as illustrated in (f) of FIG. 3B, the image generation unit 136 reconstructs each k-space data of PIF = 2 for each channel, and generates a folded image for a plurality of channels. Then, as shown in (g) of FIG. 3B, the image generation unit 136 applies the sensitivity map of each channel to each folded image of each channel, and performs the PI method unfolding process to obtain the final output. MR images are generated.

  In the description using FIG. 2 and FIGS. 3A to 3B, an example in which k-space data arranged by two types of PIFs is an object of processing has been described, but the embodiment is not limited to this, and 3 The present invention can also be applied to the case where k-space data arranged with more than one type of PIF is to be processed. In this case, for example, the image generation unit 136 may repeat the above-described processing sequentially.

  Further, in the description using FIG. 2 and FIGS. 3A to 3B, an example in which a SENSE (sensitivity encoding) technique is applied as the PI method for image generation has been described. However, the embodiment is not limited thereto, and SMASH The present invention can also be applied to the case of applying (simultaneous acquisition of spatial harmonics) technology (for example, GRAPPA (generalized auto-calibrating partially parallel acquisition)) or a combination of GRAPPA and SENSE. Alternatively, for example, a SENSE technique (K. P. Pruessmann et al. Magnetic Resonance in Medicine 46: 638-651, 2001) corresponding to an arbitrary sampling pattern may be applied.

  For example, when applying GRAPPA, the sequence control unit 120 collects k-space data at the center without thinning out as a sensitivity map for a plurality of channels. First, the image generation unit 136 calculates an interpolation coefficient for interpolating k-space data with PIF = 4 with PIF = 2 from k-space data with PIF = 2. Next, the image generation unit 136 estimates the thinned-out PIF = 2 k-space data by applying the calculated interpolation coefficient to the PIF = 4 k-space data of each channel. Further, the image generation unit 136 calculates an interpolation coefficient for interpolating k-space data with PIF = 2 from the sensitivity map. Next, the image generation unit 136 applies the calculated interpolation coefficient to the k-space data of PIF = 2 of each channel obtained by combining the estimated k-space data and the actually collected k-space data. Estimate the remaining k-space data. Thus, the image generation unit 136 generates an MR image by reconstructing using k-space data in which all lines are filled.

  For example, when GRAPPA and SENSE are combined, the image generation unit 136 calculates an interpolation coefficient for interpolating k-space data with PIF = 4 with PIF = 2 from k-space data with PIF = 2. Next, the image generation unit 136 estimates the thinned-out PIF = 2 k-space data by applying the calculated interpolation coefficient to the PIF = 4 k-space data of each channel. Thereafter, as in the case of applying the SENSE technology (similar to the processing after (e) in FIG. 3B), the image generation unit 136 actually collects the generated P-space = 2 k-space data and PIF = 2. By combining with k-space data, k-space data with PIF = 2 for a plurality of channels is generated. Next, the image generation unit 136 reconstructs each k-space data of PIF = 2 for each channel, and generates a folded image for a plurality of channels. Then, the image generation unit 136 applies the sensitivity map of each channel to each of the folded images of each channel and performs an unfolding process of the PI method to generate an MR image.

  The SNR of the MR image generated in this way is improved as compared with the MR image generated from the k-space data arranged with PIF = 4 in the entire k-space.

  Subsequently, the phase encoding pattern in the first embodiment will be described with reference to FIGS. 4 to 11 are diagrams for explaining the phase encoding pattern in the first embodiment. Note that the phase encoding pattern described below can be appropriately selected and applied in each embodiment described in the second and subsequent embodiments. Further, the embodiment of the phase encoding pattern is not limited to the pattern described below. It may be a phase encoding pattern described in the second embodiment or later and other patterns. In addition, the sequence control unit 120 does not necessarily need to control the execution of all of the phase encoding patterns described below, and may control a part of the execution. In addition, the content described below as a phase encoding pattern can be applied by replacing it with a slice encoding pattern, for example.

  Each pattern does not depend on the type of pulse sequence. The types of pulse sequences can be broadly divided into groups called “SE (Spin Echo) system” using RF pulses for refocus and “FE (Field Echo)” using gradient magnetic fields for refocusing. There are groups called “systems” etc., but each pattern can be applied to both. The SE system includes, for example, FSE (Fast SE) and FASE (Fast Asymmetric SE). On the other hand, the FE system includes FFE (Fast FE), bSSFP (balanced Steady-State Free Precession), and the like. Note that bSSFP may be handled as a series different from the SE system and the FE system. There is also EPI (Echo Planar Imaging) as a type of pulse sequence. Each pattern can be applied to collection of two-dimensional data and collection of three-dimensional data.

  Note that MR signals collected under the control of the sequence control unit 120 become k-space data only after being digitally converted and then placed in k-space by the placement unit 133a. The description will be made using the expression “the control unit 120 collects k-space data” as appropriate. Hereinafter, the MR signal corresponding to the k-space data may be referred to as an “echo signal”.

  The sequence control unit 120 controls the execution of the pulse sequence so that the sequence controller 120 is arranged in the first region of the k space at the first interval, and is arranged in the second region wider than the first region at the second interval wider than the first interval. MR signals for a plurality of channels are collected in a pulse sequence executed in a series. The phase encoding patterns collected by the sequence control unit 120 will be described in three groups. The first group is a pattern in which all k-space data arranged in k-space at different intervals is collected continuously without waiting time. The second group is a pattern that is divided and collected at different intervals. In other words, the second group is a pattern in which k-space data arranged in the k-space at the first interval and k-space data arranged in the k-space at the second interval are collected with a waiting time. is there. The third group is divided and collected as in the second group. However, the third group is not collected at different intervals, but the k-space data collected and divided is arranged in the k space. This is the pattern that will be placed. In other words, the third group is a pattern in which k-space data arranged in the k-space at the first interval and the second interval are collected together as a result of collecting the k-space data while waiting for a waiting time. The division is not limited to two divisions and may be three or more divisions.

4 and 5 show the first group of phase encoding patterns. The sequence control unit 120 is arranged at the center of the k space with PIF = 2, and the k space data arranged with PIF = 4 on the whole including the peripheral part is converted into a sequential order, a centric order, Or it collects continuously without waiting time in a scroll (scroll) order. In FIG. 4, the numbers shown in the table on the right side indicate the order of collection. Further, the sequence control unit 120 collects the k-space data while applying a phase encoding gradient magnetic field G _PE phase encode amounts shown in FIG. That is, in the case of sequential order, the sequence control unit 120 continuously collects k-space data in the order along the phase encoding direction from the phase encoding at one end of the k space, for example, as shown in FIG. Also, if the centric order, the sequence control unit 120 is, for example, as shown in FIG. 4, while changing the polarity of the phase encoding gradient G _PE alternately, gradually reach the periphery of the phase encoding of the central portion In addition, k-space data is continuously collected. In the case of scroll order, for example, as shown in FIG. 4, the sequence control unit 120 collects k-space data along a certain direction from the phase encoding of the central part, and when the end of the k-space is reached, the sequence control unit 120 Collect k-space data corresponding to the remaining phase encoding of the polarity.

  FIG. 5 shows this on the time axis. In FIG. 5 and the like, “TR (Repetition Time)” is a repetition time. In addition, “S” means one slice (Slice) in the case of collecting two-dimensional data, and one slice encoding (Slice Encode) in the case of collecting three-dimensional data. Alternatively, “S” may mean one segment. “H” indicates that k-space data corresponding to the peripheral portion of the k space, that is, the high-frequency region is collected, and “L” indicates k-space data corresponding to the central portion of the k-space, that is, the low-frequency region. Indicates to collect.

  As shown in FIG. 5A, in the case of sequential order, the sequence control unit 120 collects the peripheral part by PIF = 4, the central part by PIF = 2, and the peripheral part by PIF = 4 in 1TR. Are continuously collected without waiting time. Further, as shown in FIG. 5B, in the case of the centric order, the sequence control unit 120 waits for the collection of the central part by PIF = 2 and the collection of the peripheral part by PIF = 4 within 1TR. Do it continuously without putting. Further, as shown in FIG. 5C, in the case of the scroll order, the sequence control unit 120 also collects the central part by PIF = 2 and the peripheral part by PIF = 4 within 1TR. Do it continuously without putting. In addition, in FIG. 5, although the example which collects both the center part and peripheral part of k space was demonstrated within 1TR, embodiment is not restricted to this. The collection of the central portion and the peripheral portion of the k space may be performed by a plurality of TRs exceeding 1TR. Similarly, in the second group, the third group, and other embodiments described below, for example, the collection of k-space data corresponding to one slice, one slice encode, and one segment is 1TR. It may be performed with more than one TR. Further, in FIG. 5, the example in which the central portion is collected with PIF = 2 and the peripheral portion is collected with PIF = 4 has been described, but the embodiment is not limited thereto. The density relationship may be reversed, such as collecting the central part with PIF = 4 and collecting the peripheral part with PIF = 2. The same applies to the second group, the third group, and other embodiments described below.

  6 and 7 show the second group of phase encoding patterns. The sequence control unit 120 first collects k-space data arranged at the center of the k space with PIF = 2, and after that, after waiting for a time, it is arranged at the periphery of the k space with PIF = 4. Collect k-space data. FIG. 7 shows this on the time axis. As shown in FIG. 7A, the sequence control unit 120 collects the peripheral part by PIF = 4 after collecting the central part by PIF = 2 in 1TR and then waiting for a waiting time. Do. Further, for example, as shown in FIG. 7B, the sequence control unit 120 collects the peripheral part by PIF = 4 within 1TR, and then waits for a waiting time before the center by PIF = 2. Department collection may be performed. Each collection may be either a sequential order or a centric order.

  Next, FIGS. 8 and 9 show a third group of phase encoding patterns. The sequence control unit 120 first collects some k-space data among the k-space data arranged with PIF = 2 in the center of the k-space with PIF = 4, and then sets a waiting time, K-space data arranged with PIF = 2 in the center of k-space and k-space data arranged with PIF = 4 in the peripheral part are collected with PIF = 4. In this example, the phase encoding of the k-space data collected in the first half and the phase encoding of the k-space data collected in the second half are shifted by “2”. As a result, when k-space data collected in a divided manner is arranged in k-space, it is arranged in k-space at different intervals.

  This is shown on the time axis in FIG. As shown in (A) of FIG. 8, the sequence control unit 120 collects the central part by PIF = 4 within 1TR, and then waits for a time to shift the phase encoding by “2”. , Collect the whole with PIF = 4. Further, for example, as shown in FIG. 8B, the sequence control unit 120 shifts the phase encoding by “2” after waiting for a waiting time after performing the entire collection with PIF = 4 within 1TR. In this state, the central portion may be collected by PIF = 4. Each collection may be a sequential order, a centric order, or a scroll order. In the case of this third group of phase encoding patterns, the collection of the central part by PIF = 4 and the collection of the central part in the whole collection by PIF = 4 are collected at the same time phase. It may be desirable to synchronize the timing.

  10 and 11 illustrate a case where a ramp-up pulse or a preparation portion is applied before the imaging scan, or a case where a flip-back pulse is applied after the imaging scan. FIG. FIG. 10 corresponds to the phase encoding pattern 1 described above, (A) corresponds to the sequential order, and (B) corresponds to the centric order and scroll order. FIG. 11 corresponds to the phase encoding patterns 2 and 3 described above, and (A) and (B) are obtained by switching the collection order.

  For example, bSSFP is assumed as a pulse sequence executed in an imaging scan. In bSSFP, excitation by RF pulses is repeated to maintain the nuclear spin in the static magnetic field in a steady state. For example, the sequence control unit 120 applies a + α / 2 excitation pulse or a −α / 2 excitation pulse as a ramp-up. Subsequently, the sequence control unit 120 repeatedly applies the + α excitation pulse and the −α excitation pulse alternately for each TR. The nuclear spin in the static magnetic field is maintained in a steady state by the + α excitation pulse and the −α excitation pulse.

  10 and 11, the part indicated by the symbol a is a pulse applied as a ramp-up. As shown in FIG. 10, when the acquisition is continuously performed without waiting time within 1TR, a ramp-up pulse may be applied before the imaging scan. In addition, as shown in FIG. 11, when the collection is performed in 1TR, a ramp-up pulse may be applied before each acquisition. Note that, even in the case where the collection is performed in one TR, the ramp-up pulse may be applied only before one of the acquisitions.

  For example, the sequence controller 120 may apply a fat suppression pulse, an IR (Inversion Recovery) pulse, an STIR (Short Time IR) pulse, a T2 prep pulse, a flow prep pulse, or the like as a preparation portion. The T2 prep pulse is applied before the imaging scan in order to obtain T2 enhancement. For example, a 90 ° pulse, a 180 ° pulse, and a −90 ° pulse are applied. The flow prep pulse is applied to selectively enhance (or suppress) a blood vessel in a specific traveling direction. For example, a rephase pulse, a dephase pulse, a small intensity MPG ( Motion Probing Gradient) pulse or the like is applied in at least one of a frequency encoding direction, a phase encoding direction, and a slice encoding direction.

  In FIGS. 10 and 11, the portion indicated by the symbol b is a preparation portion pulse. As shown in FIG. 10, in the case where acquisition is performed continuously without waiting time within 1TR, a preparation portion pulse may be applied before the imaging scan. Also, as shown in FIG. 11, in the case where acquisition is performed by being divided within 1TR, it is only necessary to apply a preparation portion pulse before each acquisition. Even in the case where acquisition is performed by dividing within 1TR, the preparation portion pulse may be applied only before one acquisition.

  In the first embodiment, after a ramp-up pulse is applied, a preparation portion pulse is applied, and then an imaging scan is executed. It can be considered that the effect of the pulse in the preparation portion can be remarkably applied by applying the pulse in the preparation portion at a stage where it is brought close to a steady state to some extent by ramping up.

  For example, the sequence control unit 120 may apply a flip back pulse (for example, T2 plus) for returning the longitudinal magnetization of the nuclear spin after the imaging scan. By applying the flip back pulse, the imaging time can be shortened.

  10 and 11, the pulse indicated by the symbol c is a flip back pulse. As shown in FIG. 10, in the case where acquisition is continuously performed without waiting time within 1TR, a flip-back pulse may be applied after the imaging scan. In addition, as shown in FIG. 11, when the collection is performed in 1TR, a flip-back pulse may be applied after each acquisition. Note that even when acquisition is performed by being divided within one TR, a flip-back pulse may be applied only after one acquisition.

  It should be noted that not all of the above-mentioned pulses have to be applied, and only a part of them needs to be applied. Also, the order of application can be changed as appropriate.

  As described above, according to the first embodiment, by collecting a combination of collecting a central part in k-space with PIF = 2 and collecting a wider peripheral part with PIF = 4, for example, The imaging time can be shortened compared to the imaging time when imaging the entire k-space with PIF = 2. Further, according to the first embodiment, it is possible to suppress the reduction in SNR by a method of supplementing and reconstructing k-space data with PIF = 2 based on k-space data with PIF = 4. That is, according to the first embodiment, the image quality can be improved under high-speed imaging.

  Further, according to the first embodiment, since the k-space data is collected so that the interval between the central portions (low frequency regions) of the k space is narrower than the interval between the peripheral portions (high frequency regions), the image contrast is determined. As a result of collecting a large amount of low-frequency components, it is possible to more efficiently suppress the SNR reduction. In addition, according to the first embodiment, the time for collecting the central part of the k space is shortened, so that it is possible to expect the influence of motion and the reduction of signal blur. Further, in the first embodiment, for example, in the phase encoding patterns of the second group and the third group, since the collection by the sequence control unit 120 is all the collection at equal intervals of the PI method, the generation of sound is prevented. The suppression effect can also be expected.

(Second Embodiment)
In the second embodiment, assuming an MRI apparatus 100 having the same configuration as that of the first embodiment, an example in which a still image of a heart in a certain cardiac phase is imaged without contrast is described as an application application example. To do. Specifically, in the second embodiment, a three-dimensional segmented FFE (hereinafter referred to as “seg.FFE”) using electrocardiogram synchronization is used as an imaging scan.

  Note that the embodiment is not limited to this. The imaging target is not limited to a still image of the heart, but may be other parts such as the head, lung field, and abdomen, and other parts such as cerebrospinal fluid (CSF (Cerebrospinal Fluid)) and lymph fluid. It may be an image. Moreover, it is not restricted to electrocardiogram synchronization, For example, you may use together with respiration synchronization and respiration synchronization. The imaging scan is performed using seg. For example, other types of pulse sequences may be used.

  An imaging scan will be described. FIG. 12 is a diagram for explaining segment division of the k space in the second embodiment. In FIG. 12, for convenience of explanation, a k-space corresponding to one-slice encoding is illustrated two-dimensionally, and an example in which a 256 × 256 k-space is divided into 16 segments will be described as an example. The horizontal axis corresponds to frequency encoding, and the vertical axis corresponds to phase encoding. Each segment includes 16 lines of k-space data. As will be described later, for example, the sequence control unit 120 transmits an echo signal of one line or a plurality of lines included in each segment from all the segments between the R wave and the next R wave (between 1 RR). collect. Then, the sequence control unit 120 collects the entire echo signal corresponding to one image by repeating this collection over a plurality of heartbeats while changing the line to be collected.

  Here, as shown in FIG. 12, for example, for “Segment 8” and “Segment 9” corresponding to the central part of the k-space, the sequence control unit 120 collects echo signals at PIF = 2, and for other segments. Collects echo signals at PIF = 4. That is, the sequence control unit 120 collects echo signals of 8 lines out of 16 lines for the segment corresponding to the central part of the k space, and 4 out of 16 lines for the segment corresponding to the peripheral part of the k space. Collect line echo signals. As described above, the sequence control unit 120 collects the number of lines collected from the segment corresponding to the central part of the k space to be larger than the number of lines collected from the segment corresponding to the peripheral part of the k space.

  In FIG. 12, for example, the first, fifth, ninth, and thirteenth lines included in “Segment1” are “a1”, “b1”, “c1”, and “d1”, respectively. Similarly, for example, the first, fifth, ninth, and thirteenth lines included in “Segment2” are set to “a2”, “b2”, “c2”, and “d2”, respectively. On the other hand, for example, the first, third, fifth, seventh, ninth, eleventh, thirteenth, and fifteenth lines included in “Segment8” are respectively represented by “a81”, “a82”, “ b81 "," b82 "," c81 "," c82 "," d81 ", and" d82 ".

  FIG. 13 is a diagram for explaining an imaging scan in the second embodiment. For example, the sequence control unit 120 collects each line at the position of the phase encode “a” illustrated in FIG. 12 in order from “Segment 1” to “Segment 16” during the first 1RR. That is, as shown in FIG. 13, the sequence control unit 120 collects PIF = 4 corresponding to the peripheral part of the k space, collects PIF = 2 corresponding to the central part of the k space, and applies to the peripheral part of the k space. Corresponding collections of PIF = 4 are collected continuously without waiting time in sequential order. In addition, the sequence control unit 120 sets the delay time from the R wave so that the optimum delay time derived by the preparation scan becomes the collection timing of the line corresponding to the center of the k space, for example, “a81”. To do.

  In addition, as shown in FIG. 13, the sequence control unit 120 similarly converts each line at the position of the phase encodes “b”, “c”, and “d” shown in FIG. 12 into “Segment 1” for each subsequent RR. To “Segment 16”. Thus, for example, the sequence control unit 120 collects echo signals corresponding to one slice encoding between 4 RRs, and further repeats each slice encoding to collect echo signals arranged in a three-dimensional k-space. To do.

  The echo signals collected in this way are then placed in the k space and are processed by the image generating unit 136. Similar to the first embodiment described above, the image generation unit 136 may use a method of applying a SENSE technique, a method of applying GRAPPA, a method of combining GRAPPA and SENSE, or the like as a PI method of image generation. .

  In the second embodiment, the example of the sequential order has been described as shown in FIG. 13, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a centric order or a scroll order.

  As described above, according to the second embodiment, the image quality can be improved under high-speed imaging as in the first embodiment. More specifically, according to the second embodiment, since the time for collecting echo signals between 1 RRs is shortened as a result of increasing the PIF at least in the periphery of the k space, the influence of motion and signal blurring are reduced. Reduction can be expected. Further, since the k-space data is collected at a relatively narrow interval at the center of the k-space, it is possible to suppress the SNR reduction.

(Third embodiment)
In the third embodiment, assuming an MRI apparatus 100 having the same configuration as that of the first embodiment, as an application application example, a blood flow image of the lower limbs is captured in a non-contrast and the arteriovenous is separated. An example of generating a blood flow image will be described. This application example is sometimes called “FBI (Fresh Blood Imaging)” or the like in the sense of imaging fresh blood pumped from the heart. Specifically, in the third embodiment, three-dimensional FSE synchronized with electrocardiogram is used as an imaging scan. In the third embodiment, a preparatory scan is performed to find a systolic cardiac time phase in which the arterial signal value is suppressed and a diastole cardiac time phase in which the arteriovenous signal value is high. As the preparatory scan, a two-dimensional FSE based on electrocardiogram synchronization is used. This preparatory scan may be referred to as “ECG (Electrocardiogram) -prep” or the like.

  Note that the embodiment is not limited to this. The imaging target is not limited to the blood flow image of the lower limbs, and may be other parts such as the head, lung field, abdomen, and heart, or other fluid images such as cerebrospinal fluid and lymph. May be. Moreover, it is not restricted to electrocardiogram synchronization, For example, you may use together with respiration synchronization and respiration synchronization. Further, the preparation scan and the imaging scan are not limited to the FSE, and may be FASE combining the FSE with the half Fourier method, EPI, or the like. Further, the preparation scan may be omitted.

  First, the preparation scan will be briefly described. The sequence control unit 120 determines the collection timing of the echo signal in the imaging scan by performing the preparation scan based on the electrocardiogram synchronization prior to the imaging scan. For example, the sequence control unit 120 sets a plurality of delay times from the peak value of the R wave of the ECG signal, and generates echo signals for generating images of each delay time while changing the delay times over a plurality of heartbeats. collect.

  The image generation unit 136 generates an image for each delay time from the collected echo signals while changing the delay time. The cardiac phase where the blood flow is a high signal value for each systole and diastole, that is, the optimum delay time, for example, each image for each delay time is displayed on the display unit 135 and is derived by comparative observation by the operator. The Alternatively, it is derived by comparative analysis of signal values within a predetermined area of each image. Thus, the two optimum delay times derived by the preparation scan are set as the collection timing of the echo signal arranged at the center of the k space in the imaging scan. In the following, an example is described in which the PI method, which is acquired by combining different intervals, is applied to an imaging scan. However, the PI method can be similarly applied to a preparation scan.

  Note that the preparation scan and the imaging scan are generally performed by matching the imaging conditions other than the two-dimensional and the three-dimensional (for example, the type of the pulse sequence and the imaging parameters) from the viewpoint of matching the image quality and the like. The embodiment is not limited to this. Both may be performed in the same two-dimensional or three-dimensional manner, and imaging conditions may be different. The same applies to other embodiments other than the second embodiment.

  Next, an imaging scan will be described. FIG. 14 is a diagram for explaining an imaging scan in the third embodiment. For example, the sequence control unit 120 collects echo signals of systole and diastole corresponding to one slice encoding during 2RR. For example, when a predetermined delay time elapses from the peak of the R wave, the sequence control unit 120 first collects systolic echo signals arranged at the center of the k space with PIF = 2. Subsequently, when a predetermined delay time further elapses, the sequence control unit 120 first changes the centric order signal while changing the expansion period echo signal arranged in the entire k space from PIF = 2 to PIF = 4. Or it collects continuously without putting waiting time in the scroll order. That is, in the third embodiment, the sequence control unit 120 collects only the echo signal in the central part for the systole and collects the entire echo signal for the diastole. As will be described later, when the systolic image is generated, the echo signals of the peripheral portion collected for the diastole are used.

  In the third embodiment, as illustrated in FIG. 14, the example in which the systolic echo signal is collected first and then the diastolic echo signal is collected has been described, but the embodiment is limited to this. Instead of collecting the diastolic echo signal, the systolic echo signal may be collected. In the third embodiment, an example in which echo signals in the diastolic phase are collected for the entire k space and used for systolic image generation will be described. However, the embodiment is not limited to this, Systolic echo signals may be collected for the entire k-space and used for diastole image generation. In the third embodiment, the example of the centric order and the scroll order has been described as shown in FIG. 14, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order.

  The echo signals collected in this way are then placed in the k space and are processed by the image generating unit 136. Similar to the first embodiment described above, the image generation unit 136 may use a method of applying a SENSE technique, a method of applying GRAPPA, a method of combining GRAPPA and SENSE, or the like as a PI method of image generation. .

  FIG. 15 is a diagram for explaining an example of image generation according to the third embodiment. FIG. 15 shows a method of applying SENSE technology. Further, in FIG. 15, for convenience of explanation, description will be made using two-dimensional k-space data and a two-dimensional image. However, as described above, when three-dimensional k-space data is acquired by an imaging scan, Typically, a three-dimensional image is generated from three-dimensional k-space data.

  As shown in FIG. 15, in the systolic k-space data, only the central portion is arranged with PIF = 2. On the other hand, in the k-space data in the expansion period, the peripheral portion is arranged with PIF = 4 and the central portion is arranged with PIF = 2. In FIG. 15, the vertical stripe pattern indicates k-space data actually collected.

  The image generation unit 136 generates images for each systole and diastole. For example, the image generation unit 136 generates an expansion period image by performing the processes (a) to (g) described with reference to FIGS. 3A and 3B on the expansion period k-space data. Further, the image generation unit 136 uses (for example, duplicates) the diastole k-space data when generating the systole image. Here, two methods can be considered from the viewpoint of diverting the expansion period k-space data at which stage. In FIG. 15, a black pattern indicates k-space data generated by duplication or reverse reconstruction.

  As shown in FIG. 15 (A), one method is a method of filling “actually collected k-space data” in the diastole by duplicating it as k-space data in the peripheral part of the systole. . In this case, as shown in FIG. 15A, systolic k-space data is arranged with PIF = 4 in the whole including the peripheral portion and arranged with PIF = 2 in the central portion. Therefore, the image generation unit 136 performs the processes (a) to (g) described with reference to FIGS. 3A and 3B on the k-space data, thereby generating a systolic image.

  In another method, as shown in FIG. 15B, after generating k-space data of PIF = 2 for the diastole, the k-space data of the peripheral part is converted into the k-space data of the peripheral part of the systole. It is a method of filling by duplicating as. In this case, the image generation unit 136 first performs the processes (a) to (d) (or (e)) described with reference to FIGS. 3A and 3B on the k-space data actually collected in the expansion period. And k-space data with PIF = 2 is generated for the expansion period. Subsequently, the image generation unit 136 replicates the k-space data of the peripheral part of the diastole as the k-space data of the peripheral part of the systole. The systolic k-space data is arranged with PIF = 2 in the entire k-space, as shown in FIG. Therefore, the image generation unit 136 generates a systolic image by performing the processes (e) to (f) described with reference to FIG. 3B on the k-space data.

  Here, as shown in FIG. 15, in the systolic image, veins (VE (vein)) are drawn with bright blood (white) having a high signal value, and arteries (AR (artery)) are depicted. , Rendered with a bright blood with a low signal value. This is because, during systole, the arterial flow rate is high compared to the venous flow rate flowing at low speed. In FIG. 15, for convenience of explanation, an artery drawn with bright blood having a low signal value is represented by a dotted line. On the other hand, as shown in FIG. 15, in the diastole image, both veins and arteries are depicted with bright blood having a high signal value. This is due to the slow flow rates of both veins and arteries during diastole. In FIG. 15, for the convenience of explanation, “bright blood” usually drawn in white is represented by a hatched pattern or the like.

  Therefore, the image generation unit 136 generates, for example, an image in which only the artery is depicted by performing a difference process for each pixel between the systolic image and the diastole image. In addition, in this difference process, you may weight appropriately. In addition, this difference processing is not limited to the case of performing between images, and may be performed between k-space data.

  Note that when FASE is used as a preparation scan or an imaging scan, for example, the sequence control unit 120 collects k-space data in the central part with PIF = 2 and the k-space data in the peripheral part only on one side for the PIF. Collect at = 4. Further, the image generation unit 136 estimates the k-space data of the peripheral portion on the opposite side using the actually collected k-space data for the expansion period, so that both peripheral portions are arranged with PIF = 4, K-space data is obtained in which the central portion is arranged with PIF = 2. In this estimation, there is a risk of deviation in the phase encoding direction. In such a case, the image generation unit 136 may perform correction.

  In the third embodiment, the example in which the collection of the echo signal in the systole and the collection of the echo signal in the diastole is performed in the same TR, but the embodiment is not limited thereto. For example, the sequence control unit 120 may perform collection of echo signals in systole and collection of echo signals in diastole with different TRs. Alternatively, after collecting echo signals for a plurality of slice encodes and systoles, echo signals for a plurality of slice encodes and diastole may be collected.

(Modification of the third embodiment)
In the third embodiment, an example of collecting echo signals in systole and diastole using 2RR as TR has been described, but the embodiment is not limited thereto. Echo signals of systole and diastole may be collected using 3RR or more or 1RR as TR.

  FIG. 16 is a diagram for explaining an imaging scan in a modification of the third embodiment. For example, when a predetermined delay time elapses from the peak of the R wave, the sequence control unit 120 first changes the systolic echo signal arranged in the entire k space from PIF = 2 to PIF = 4, Collect continuously without waiting time in centric order or scroll order. Subsequently, when a predetermined delay time further elapses, the sequence control unit 120 collects the echo signals in the expansion period arranged at the center of the k space with PIF = 2. That is, in the modification of the third embodiment, the sequence control unit 120 collects only the echo signal in the central part for the diastole and collects the entire echo signal for the systole. In the case of generating an diastolic image, the peripheral echo signals collected for the systole are used. When 1RR is set to TR, it is considered difficult to finish collecting the echo signals in the diastole due to the relationship with the next R wave. For this reason, in the modification of the third embodiment, the echo signal of only the central part is collected in the diastole. In this case, it is desirable to apply a flip-back pulse (for example, T2 plus) after collecting the systolic and diastolic echo signals, as indicated by the symbol d in FIG. As in the third embodiment, the order of collection and the like can be changed as appropriate in this modification.

  As described above, according to the third embodiment, the image quality can be improved under high-speed imaging as in the first embodiment. More specifically, according to the third embodiment, as a result of increasing the PIF at least in the periphery of the k-space and collecting only the central part in one of the systole and the diastole, Since the time for collecting echo signals corresponding to one slice encoding is shortened, it is possible to reduce the influence of motion and signal blur. Further, since the k-space data is collected at a relatively narrow interval at the center of the k-space, it is possible to suppress the SNR reduction. Furthermore, if the collection time of the echo signal is shortened, 1RR can be set to TR as in the modified example, and the imaging time can be further shortened.

(Fourth embodiment)
In the fourth embodiment, assuming an MRI apparatus 100 having the same configuration as that of the first embodiment, as an application application example, a blood flow image of the lower limbs is captured non-contrastly, and the arteriovenous is separated. An example of generating a “moving image” of a blood flow image will be described. This application example is sometimes referred to as “Time-Resolved MRA (MR Angiography)” using FBI (of arteriovenous separation type). Specifically, in the fourth embodiment, three-dimensional FSE synchronized with electrocardiogram is used as an imaging scan.

  Note that the embodiment is not limited to this. The imaging target is not limited to the blood flow image of the lower limbs, and may be other parts such as the head, lung field, abdomen, and heart, or other fluid images such as cerebrospinal fluid and lymph. May be. Moreover, it is not restricted to electrocardiogram synchronization, For example, you may use together with respiration synchronization and respiration synchronization. Further, the imaging scan is not limited to FSE, and may be, for example, FASE in which a half Fourier method is combined with FSE, EPI, or the like.

  In the fourth embodiment, an example in which the preparatory scan is not performed will be described. However, the embodiment is not limited to this. That is, in the fourth embodiment, as will be described later, echo signals corresponding to a plurality of cardiac time phases are collected while changing the delay increment in a section where the change in the arterial signal value is severe during one RR. . For this reason, for example, in order to identify this section, echo signals are collected in relatively coarse increments for the entire 1RR, and preparation for identifying a section in which the signal value of the artery is severely changed from each generated image A scan may be performed.

  FIG. 17 is a diagram for explaining a change in the signal value of an artery in the fourth embodiment. The vertical axis represents the signal value of the artery, and the horizontal axis represents the cardiac phase for 1 RR. As described in the third embodiment, in the systole, the arterial flow rate is higher than the flow rate of the venous flowing at a low speed, and thus the signal value of the artery is low. On the other hand, in the diastole, the arterial flow rate is also low, and the signal value is high. FIG. 17 shows the state of this change, and particularly shows that the change is severe in a section indicated by two dotted lines (hereinafter referred to as “interest section”).

  Therefore, in the fourth embodiment, the sequence control unit 120 divides the cardiac time phase in the interest interval into a predetermined number so that the moving image in the interest interval is obtained, and for each divided cardiac time phase. Collect echo signals. For example, it is assumed that 1RR is 650 to 1,300 msec and the section of interest is 200 msec. For example, the sequence control unit 120 divides this 200 msec section of interest into 10 and controls the execution of the pulse sequence so that the delay time increment from the R wave peak becomes 20 msec.

  FIG. 18 is a diagram for explaining an imaging scan in the fourth embodiment. For example, when a predetermined delay time elapses from the peak of the R wave during the first 1 RR, the sequence control unit 120 changes the systolic echo signal arranged in the entire k space from PIF = 2 to PIF = 4. While changing, collect continuously without waiting time in centric order or scroll order. Subsequently, in each RR, the sequence control unit 120 increases the delay time from the peak of the R wave by 20 msec and collects echo signals of each cardiac phase arranged at the center of the k space at PIF = 2. . For example, comparing the delay time “D1” with the delay time “D2”, the delay time “D2” is 20 msec longer than the delay time “D1”. As described above, in the fourth embodiment, the sequence control unit 120 collects only echo signals at the center for each cardiac time phase in the interval of interest, and collects the entire echo signals for systole. As will be described later, when an image of each cardiac time phase is generated, the peripheral echo signals collected for the systole are used.

  In the fourth embodiment, an example will be described in which systolic echo signals are collected for the entire k-space and used for image generation of each cardiac phase within the interval of interest. However, the present invention is not limited thereto, and diastole echo signals may be collected for the entire k-space and used for image generation for each cardiac phase. In the fourth embodiment, as shown in FIG. 18, an example of a centric order or a scroll order has been described. However, the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order.

  The echo signals collected in this way are then placed in the k space and are processed by the image generating unit 136. Similar to the first embodiment described above, the image generation unit 136 may use a method of applying a SENSE technique, a method of applying GRAPPA, a method of combining GRAPPA and SENSE, or the like as a PI method of image generation. .

  FIG. 19 is a diagram for explaining an example of image generation according to the fourth embodiment. FIG. 19 shows a method of applying SENSE technology. In FIG. 19, for convenience of explanation, the description will be made using two-dimensional k-space data and a two-dimensional image. However, as described above, when three-dimensional k-space data is acquired by an imaging scan, Typically, a three-dimensional image is generated from three-dimensional k-space data.

  As shown in FIG. 19, the k-space data of each cardiac time phase in the section of interest is arranged with PIF = 2 only at the center. On the other hand, in the systolic k-space data, the peripheral part is arranged with PIF = 4 and the central part is arranged with PIF = 2. In FIG. 19, the vertical stripe pattern indicates the actually collected k-space data.

  The image generation unit 136 generates images for each cardiac time phase and systole in the interval of interest. For example, the image generation unit 136 generates the systolic image by performing the processes (a) to (g) described with reference to FIGS. 3A and 3B on the k-space data of the systole. Further, the image generation unit 136 diverts (for example, duplicates) the systolic k-space data when generating an image of each cardiac phase within the interval of interest. Here, as in the third embodiment, two methods can be considered from the viewpoint of diverting the systolic k-space data at which stage. In FIG. 19, a black pattern indicates k-space data generated by duplication or reverse reconstruction.

  Since this method is the same as that of the third embodiment, one method will be described as follows. As shown in (A) of FIG. 19, each method uses “actually collected k-space data” in the systole. This is a method of filling by duplicating the k-space data around the cardiac phase. In another method, as shown in FIG. 19B, after generating k-space data of PIF = 2 for the systole, the k-space data of the peripheral part is converted into the k-value of the peripheral part of each cardiac phase. This is a method of filling by copying as spatial data.

  Then, the image generation unit 136 generates an image in which only the artery is depicted, for example, by performing a difference process for each pixel between each cardiac time phase image and the systolic image. In addition, in this difference process, you may weight appropriately. In addition, this difference processing is not limited to the case of performing between images, and may be performed between k-space data.

  Here, as shown in FIG. 19, the systolic image is an image in which veins are depicted in bright blood (white) with a high signal value and arteries are depicted in bright blood with a low signal value. On the other hand, in the image of each cardiac phase in the interval of interest, the veins are depicted with bright blood having a high signal value. In addition, since the signal value of the artery gradually increases from the systole to the diastole, it is depicted by bright blood with a gradually high signal value (in FIG. 19, an image of a certain cardiac phase). Showing). In FIG. 19, for the convenience of explanation, “bright blood” which is usually drawn in white is expressed in black.

  FIG. 20 is a diagram for explaining an example of a moving image according to the fourth embodiment. As shown in FIG. 20, the image generation unit 136 according to the fourth embodiment can generate a moving image in which an artery is depicted with a bright blood with gradually high signal values. In FIG. 20, for convenience of explanation, “Bright Blood” is expressed in black, and the state in which the signal value gradually increases is expressed in a manner in which black gradually increases. However, in general, “bright blood” means that veins and arteries are drawn in white compared to the background signal. In this case, the artery is drawn so as to gradually float in white as the signal value gradually increases from the systole to the diastole.

(Modification of the fourth embodiment)
Further, in the fourth embodiment, an example has been described in which echo signals of each cardiac phase in the interval of interest are collected by different RRs, but the embodiment is not limited to this. Echo signals for a plurality of cardiac phases may be collected within 1 RR.

  FIG. 21 is a diagram for explaining an imaging scan in a modified example of the fourth embodiment. For example, as in the fourth embodiment described above, the sequence control unit 120, during a first 1 RR, when a predetermined delay time elapses from the peak of the R wave, the systolic echo signal arranged in the entire k space. Are continuously collected without changing the waiting time in the centric order or scroll order while changing from PIF = 2 to PIF = 4. Subsequently, in the next RR, the sequence control unit 120 receives echo signals corresponding to the delay time “D1”, the delay time “D3”, the delay time “D5”, the delay time “D7”, and the delay time “D9”. Collect at PIF = 2. Furthermore, in the next RR, the sequence control unit 120 performs echo signals corresponding to the delay time “D2”, the delay time “D4”, the delay time “D6”, the delay time “D8”, and the delay time “D10”. Are collected at PIF = 2. When the collection time of echo signals for each cardiac phase is longer than the time resolution (for example, 20 msec), the collection of each cardiac phase may be alternately assigned to a plurality of RRs.

  In the modification of the fourth embodiment, the example of the centric order and the scroll order has been described as shown in FIG. 21, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order.

  The allocation of each cardiac phase shown in FIG. 21 is only an example. For example, when the acquisition time is shorter than the time resolution, echo signals of each cardiac phase may be collected continuously by the amount that can be collected by each RR. For example, the sequence control unit 120 may continuously collect echo signals corresponding to the delay time “D1” to the delay time “D10” with PIF = 2 during one RR.

  As described above, according to the fourth embodiment, the image quality can be improved under high-speed imaging as in the first embodiment. More specifically, according to the fourth embodiment, the echo signal can be collected from the systole having a signal difference to the diastole by increasing the delay time (for example, 10 msec to 20 msec). An image with less blur can be obtained. Furthermore, as in the modification, echo signals for a plurality of cardiac phases can be collected between 1 RR, and the imaging time can be shortened. The embodiment is not limited to the above-described fourth embodiment and its modifications. For example, the sequence control unit 120 may collect echo signals arranged in the entire k space not only in the first 1 RR but also in the second and subsequent RRs.

(Fifth embodiment)
In the fifth embodiment, assuming an MRI apparatus 100 having the same configuration as that of the first embodiment, an example in which a moving image of a blood flow image of the heart is captured without contrast will be described as an application application example. This application example is a technique for labeling a fluid that flows into or out of an imaging region, and is sometimes referred to as “Time-SLIP (Time-Spatial Labeling Inversion Pulse)”. Specifically, in the fifth embodiment, three-dimensional FSE synchronized with electrocardiogram is used as an imaging scan.

  Note that the embodiment is not limited to this. The method of the fifth embodiment is not limited to moving images, and can be similarly applied to capturing still images. The imaging target is not limited to the blood flow image of the heart, and may be, for example, other parts such as the head, lung field, abdomen, and lower limbs, and other fluid images such as cerebrospinal fluid and lymph fluid. It may be. Moreover, it is not restricted to electrocardiogram synchronization, For example, you may use together with respiration synchronization and respiration synchronization. Further, the imaging scan is not limited to FSE, and may be, for example, FASE in which a half Fourier method is combined with FSE, bSSFP, or the like.

  In the fifth embodiment, an example in which the preparatory scan is not performed will be described. However, the embodiment is not limited to this. As in the fourth embodiment, echo signals are collected in a relatively coarse increment for the entire 1RR, and a preparatory scan is performed from each of the generated images to identify a section of interest in which the arterial signal value changes drastically. Also good.

  First, Time-SLIP will be briefly described. In Time-SLIP, a fluid that flows into or out of an imaging region is labeled in a labeling region that is independent of the imaging region. For example, the labeling region is set in the aorta located upstream of the myocardium. Then, the signal value of the fluid that flows into or out of the imaging region after a predetermined time becomes relatively high or low, and the fluid is rendered. The predetermined time may be referred to as BBTI (Black-Blood Time to Inversion) time or the like.

  FIG. 22 is a diagram for explaining an imaging scan in the fifth embodiment. In FIG. 22, for the pulse sequence, only labeled pulses are shown for convenience of explanation. In addition, displays such as “BBTI = 1” to “BBTI = 6” indicate that the BBTI time, that is, the elapsed time from the application of the labeling pulse gradually increases.

  For example, when a predetermined delay time elapses from the peak of the R wave, the sequence control unit 120 applies a region non-selection inversion pulse and a region selection inversion pulse as labeling pulses. Usually, the region non-selective inversion pulse is applied to the entire imaging region, and the region selective inversion pulse is applied to the labeling region. Whether or not to apply a region non-selective inversion pulse can be selected depending on how the signal is rendered.

  A typical example will be described. For example, it is assumed that the labeling area is set in the imaging area. First, when the sequence control unit 120 applies a region non-selection inversion pulse to the entire imaging region, the longitudinal magnetization component of the tissue in the entire imaging region is reversed. Subsequently, the sequence control unit 120 applies the region selection inversion pulse only to the labeled region in the imaging region. Then, the longitudinal magnetization component of the tissue in the labeled region is reversed again. After BBTI time from the application, the tissue to which only the region non-selective inversion pulse is applied, that is, the tissue other than the labeled tissue is recovered and its longitudinal magnetization component becomes 0 (Null Point). The sequence control unit 120 collects echo signals at this timing, for example. As a result, only the labeled fluid is visualized with a high signal value. Since the labeled fluid flows out to the imaging region, it may be referred to as “flow out” or the like.

  On the other hand, for example, it is assumed that the labeling area is set outside the imaging area. When the sequence control unit 120 applies the region selection inversion pulse only to the labeled region outside the imaging region, the longitudinal magnetization component of the tissue in the labeled region is reversed. The labeled fluid then flows into the imaging region, but since the tissue in the imaging region has not been applied with the inversion pulse, there is a difference between the longitudinal magnetization components of the two. The sequence control unit 120 collects echo signals after BBTI time. As a result, only the labeled fluid is visualized with a low signal value. Since the labeled fluid flows into the imaging region, it may be referred to as “flow-in” or the like.

  Note that the sequence control unit 120 may use pCASL (Pulsed Continuous Arterial Spin Labeling) that continuously emits a labeling pulse. Moreover, the position and number of labeling regions can be arbitrarily changed. Further, an IR (Inversion Recovery) pulse, a SAT (saturation) pulse, a SPAMM (Spatial Modulation of Magnetization) pulse, a DANTE pulse, or the like may be used as a pulse for labeling. The SAT pulse is a pulse that saturates the longitudinal magnetization component by tilting the magnetization vector of the labeled region by 90 °. The SPAMM pulse and the DANTE pulse form a region saturated with a desired pattern such as a stripe pattern, a grid pattern, or a radial pattern by adjusting the gradient magnetic field.

  As shown in FIG. 22, for example, the sequence control unit 120, when a predetermined delay time (for example, BBTI = 1) elapses from the peak of the R wave during the first 1RR, echoes arranged in the entire k space. The signal is continuously collected without changing the waiting time in the centric order or scroll order while changing from PIF = 2 to PIF = 4. Subsequently, in each RR, the sequence control unit 120 collects echo signals of each cardiac phase arranged at the center of the k space with PIF = 2 while gradually increasing the delay time from the peak of the R wave. . Thus, in the fifth embodiment, the sequence control unit 120 collects the entire echo signal for a certain BBTI time, and collects the echo signal only for the central part for other BBTI times. When an image for each BBTI time is generated, a peripheral echo signal collected for a certain BBTI time is used.

  In the fifth embodiment, the example of the centric order and the scroll order has been described as shown in FIG. 22, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order.

  Note that the image generation processing in the fifth embodiment can be performed, for example, in the same manner as in the fourth embodiment. That is, for example, the image generation unit 136 performs the processes (a) to (g) described with reference to FIGS. 3A and 3B on the k-space data of “BBTI = 1”, so that “BBTI = 1”. Generate an image of Further, when generating an image of another BBTI time, the image generation unit 136 diverts (for example, duplicates) the k-space data of “BBTI = 1” and is arranged with PIF = 2 in the entire k-space. K-space data is generated. Then, the image generation unit 136 generates an image for each BBTI time by performing the processes (e) to (f) described with reference to FIG. 3B on the k-space data.

(Modification of the fifth embodiment)
In the fifth embodiment, an example in which echo signals for each BBTI time are collected by different RRs has been described, but the embodiment is not limited thereto. Within one RR, echo signals corresponding to a plurality of BBTI times may be collected. In addition, two images are collected at the same cardiac phase by performing collection with labeling by region-selective inversion pulses and collection without labeling by region-selective inversion pulses, and the two collected images There is a technique for extracting only the labeled fluid and suppressing the background signal by differential processing. This technique may be further applied. Note that this difference processing is not limited to the case where the images are performed between images, and may be performed between k-space data.

  FIG. 23 is a diagram for explaining an imaging scan in a modification of the fifth embodiment. In FIG. 23, the ECG waveform signal is omitted. This is because in Time-SLIP, ECG is only a trigger for applying a labeling pulse. The BBTI time is the elapsed time from the labeling pulse.

  For example, the sequence control unit 120 first applies a region non-selective inversion pulse, and does not apply the region selective inversion pulse (ie, does not perform labeling), and echoes arranged in the entire k space. The signal is continuously collected without changing the waiting time in the centric order or scroll order while changing from PIF = 2 to PIF = 4. Subsequently, the sequence control unit 120, after applying both the region non-selection inversion pulse and the region selection inversion pulse (that is, after labeling), is k-space data having different BBTI times. The k-space data arranged at the center of the k-space is continuously collected with PIF = 2.

  In the modification of the fifth embodiment, the example of the centric order and the scroll order has been described as shown in FIG. 23, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order. Further, the order of collection without labeling and collection with labeling may be reversed.

  Then, for example, the image generation unit 136 performs the processes (a) to (g) described with reference to FIGS. 3A and 3B on the k-space data collected without labeling, so that the background Generate an image of the signal. In addition, when generating an image of each BBTI time collected by performing labeling, the image generation unit 136 diverts (for example, duplicates) k-space data collected without performing labeling, and k-space K-space data arranged with PIF = 2 is generated. Then, the image generation unit 136 generates an image for each BBTI time by performing the processes (e) to (f) described with reference to FIG. 3B on the k-space data. Subsequently, the image generation unit 136 performs a differential process on the background signal image and the image of each BBTI time for each pixel, thereby rendering only the labeled fluid and reducing the background signal. Generate. In addition, in this difference process, you may weight appropriately. In addition, this difference processing is not limited to the case of performing between images, and may be performed between k-space data.

  As described above, according to the fifth embodiment, the image quality can be improved under high-speed imaging as in the first embodiment. More specifically, according to the fifth embodiment, since the time resolution of the BBTI time can be increased, an image with less blur can be obtained. Further, as in the modification, echo signals for a plurality of BBTI times can be collected between 1 RR, and the imaging time can be shortened.

(Sixth embodiment)
In the sixth embodiment, assuming the MRI apparatus 100 having the same configuration as that of the first embodiment, as an application application example, an example in which the blood flow dynamics of the myocardium is imaged by non-electrocardiographic synchronization by contrast imaging. explain. This application example may be referred to as “myocardial perfusion” or the like. Myocardial perfusion is a technique for obtaining a T1-weighted image showing temporal changes in myocardial staining by continuously taking a cross-sectional image of the left ventricular short axis at high speed after administering a contrast agent as a bolus from a vein.

  Note that the embodiment is not limited to this. The imaging target is not limited to the blood flow dynamics of the myocardium, but may be other parts such as the chest and liver, or may be the dynamics of other fluids such as cerebrospinal fluid and lymph. Any non-electrocardiographic imaging by contrast can be applied in the same manner. Further, for example, segmented FFE or FFE_EPI in which FFE and EPI are combined can be applied to the imaging scan.

  FIG. 24 is a diagram for explaining an imaging scan in the sixth embodiment. For example, the sequence control unit 120 first waits in the centric order or the scroll order while changing the echo signal arranged in the entire k-space from PIF = 2 to PIF = 4 before administration of the contrast agent. Collect continuously without placing. Subsequently, after administration of the contrast agent, the sequence control unit 120 continuously collects k-space data arranged at the center of the k-space at PIF = 2.

  In the sixth embodiment, an example of a centric order or a scroll order has been described as shown in FIG. 24, but the embodiment is not limited to this. As described in the first embodiment, the present invention can be similarly applied to a sequential order. Further, the collection described as before imaging may be collected after a predetermined time has elapsed after imaging. In addition, the acquisition before contrast is not limited to the acquisition performed while changing from PIF = 2 to PIF = 4. For example, the entire k space may be acquired with PIF = 2, or the entire k space may be acquired with PIF = 4 may be collected. The same applies to acquisition before contrast in each modification of the sixth embodiment described below.

  For example, the image generation unit 136 performs the processes (a) to (g) described with reference to FIGS. 3A and 3B on the k-space data before contrast, thereby generating an image before contrast. . Further, when generating each image after contrast enhancement, the image generation unit 136 diverts (for example, duplicates) k-space data before contrast enhancement, and k-space data arranged with PIF = 2 in the entire k-space. Is generated. Then, the image generation unit 136 performs the processes (e) to (f) described with reference to FIG. 3B on the k-space data, thereby generating each post-contrast image. Subsequently, the image generation unit 136 performs an image difference process on the pre-contrast image and the post-contrast image for each pixel, thereby generating an image in which only the contrasted blood vessel is depicted. In addition, in this difference process, you may weight appropriately. In addition, this difference processing is not limited to the case of performing between images, and may be performed between k-space data.

(Modification 1 of 6th Embodiment)
FIG. 25 is a diagram for explaining an imaging scan in Modification 1 of the sixth embodiment. FIG. 25 illustrates an example in which a left ventricular short-axis multi-slice image is continuously captured at high speed. As shown in FIG. 25, for example, the sequence control unit 120 first determines an echo signal arranged in the entire k space for each slice (for example, slices 1 to 3) before administration of the contrast agent. While changing from 2 to PIF = 4, continuously collecting without waiting time in centric order or scroll order. Subsequently, after administration of the contrast agent, the sequence control unit 120 collects k-space data arranged at the center of the k-space continuously for each slice at PIF = 2. This continuous collection may be referred to as “dynamic imaging”, and each time phase may be referred to as “dynamic time phase”. As shown in FIG. 25, the sequence control unit 120 continuously collects k-space data of each slice for each dynamic time phase. For example, the sequence control unit 120 collects k-space data of slices 1 to 3 for the dynamic time phase 1, and subsequently collects k-space data of slices 1 to 3 for the dynamic time phase 2.

(Modification 2 of the sixth embodiment)
FIG. 26 is a diagram for explaining an imaging scan in Modification 2 of the sixth embodiment. FIG. 26 shows an example in which the k-space data after contrast agent administration is collected in synchronization with the electrocardiogram in comparison with FIG. That is, the sequence control unit 120, for example, after the contrast agent is administered, at each RR, at a timing when a certain delay time has elapsed from the peak value of the R wave of the ECG signal, the k space arranged in the center of the k space Data is collected at PIF = 2. The other points are the same as in the sixth embodiment.

(Modification 3 of the sixth embodiment)
FIG. 27 is a diagram for describing an imaging scan in Modification 3 of the sixth embodiment. FIG. 27 shows an example in which k-space data of each dynamic time phase after contrast medium administration is collected in electrocardiographic synchronization in comparison with FIG. That is, for example, after the contrast agent is administered, the sequence controller 120 converts the k-space data of each dynamic time phase into PIF = at the timing when a certain delay time has elapsed from the peak value of the R wave of the ECG signal in each RR. Collect at 2. The time phases of the slices 1, 2, and 3 are consistent among the plurality of RRs. Other points are the same as in the first modification of the sixth embodiment.

  As described above, according to the sixth embodiment and its modifications, the image quality can be improved under high-speed imaging as in the first embodiment. More specifically, according to the sixth embodiment, since the time resolution can be increased, an image with less blur can be obtained. Furthermore, the imaging time can be shortened.

(Other embodiments)
Note that the embodiment is not limited to the above-described embodiment.

(Application of each embodiment)
In the embodiment described above, there are a case where it is described as a general-purpose imaging scan (or a preparation scan) and a case where it is described as an application application example, but these are not limited to this division. For example, you may apply the phase encoding pattern demonstrated by the general purpose positioning in 1st Embodiment to each application after 2nd Embodiment. Conversely, each pattern described as an application application example in the second and subsequent embodiments may be handled as a general-purpose pattern applicable to other applications. The same applies to the pattern described as a modification of the embodiment. Furthermore, even in the case where the specific imaging target and the type of the pulse sequence are specified and described in each embodiment and its modification examples, the embodiment is not limited to this, and other imaging target and other types are also described. The pulse sequence may be applied. In each embodiment, a flip back pulse or the like may be added as appropriate.

(Image generation method)
In the above-described embodiment, as the PI method for image generation, it has been described that a technique applying a SENSE system technique, a technique applying GRAPPA, and a technique combining GRAPPA and SENSE can be applied. It is not limited to. The image may be generated by other methods. In this case, the image generation unit 136 is based on, for example, a combination of k-space data arranged in the k-space by the arrangement unit 133a, information on the sensitivity of each channel, and knowledge data given separately, or a combination thereof. Thus, an MR image is generated.

(Switch between TR)
Further, in the above-described embodiment, an example in which the phase encoding to be collected is not particularly changed when each slice encoding, each slice, and each segment is repeatedly collected for each TR has been described. However, the embodiment is not limited to this. Even if the same PIF = 4 or PIF = 2, even if the phase encoding to be collected is switched, such as collecting even phase encoding in one TR and collecting odd phase encoding in the next TR. Good.

  In the above-described embodiment, the case where the range of phase encoding that is “the center of k-space” is constant in each TR has been described, but the embodiment is not limited to this. For example, when collecting k-space data on the side where the k-space data is diverted (for example, the side to be duplicated), the central range (for example, the range collected at PIF = 2) is set slightly wider. May be. Or, conversely, when collecting k-space data on the side where the k-space data is diverted (for example, the replicating side), the range of the central portion may be set slightly wider.

  In the above-described sixth embodiment, an example of imaging by contrast has been described. In the case of this contrast enhancement, both the timing at which temporal resolution should be prioritized and the timing at which spatial resolution should be prioritized may be included. For example, after contrast medium administration, an organ such as the liver is collected with a spatial resolution after collection with increased temporal resolution. In such a case, it may be collected while changing the PIF with the lapse of time after contrast medium administration.

  Further, when collecting k-space data of different time phases in each TR as in the patterns shown in FIG. 18 and FIG. 22, for example, according to the remaining time until the next R wave, for example, PIF = 2 The width of the collected range may be variable. When making it variable, the width may be adjusted in consideration of matching the recovery of magnetization, or a flip back pulse may be applied. Alternatively, the k-space data that can be collected by each TR may be collected once, and then the image generation unit 136 may perform image generation except for k-space data that cannot be used for image generation.

(Specific numerical values, processing order)
In addition, the specific numerical values and processing order exemplified in the above-described embodiment are merely examples in principle. For example, the PIF, the number of types of intervals, the direction of thinning, the size of k-space, the number of segments, the increment of delay time, the number of cardiac phases at the time of moving image collection, etc. can be arbitrarily changed. Also, the order of processing can be arbitrarily changed, for example, processing that can be performed in parallel can be performed in parallel.

  For example, the timing at which the k-space data is arranged at the first interval in the first area of the k-space and the timing at which the k-space data is arranged at the second interval in the second area are not necessarily the same timing. For example, in the case of a pattern in which k-space data arranged at the second interval is collected in advance, it is only necessary that k-space data is arranged at the second interval in the second area in the k-space at a certain stage. . In other words, at this stage, the k-space data at the first interval may not be arranged in the first region of the k-space. At this stage, the image generation unit 136 can execute a process of generating k-space data at the first interval from the k-space data at the second interval. The sequence control unit 120 and the arrangement unit 133a may collect and arrange k-space data in the first region at the first interval in parallel with the process by the image generation unit 136. When performed in parallel, the entire processing time from acquisition to MR image generation can be shortened. Furthermore, the embodiment includes a case where the k space in which the k space data is arranged at the first interval and the k space in which the k space data is arranged at the second interval are not the same k space.

  In addition, for example, when k-space data corresponding to systole (or diastole) is collected and arranged in advance, or k-space data corresponding to “BBTI = 1” is collected and arranged in advance. If the k-space data corresponding to the pre-contrast image is collected and arranged in advance, the image generation unit 136 uses the k-space data collected and arranged in advance to perform MR. Image generation processing may be started.

(Image processing system)
In the above-described embodiment, the case where the MRI apparatus 100 that is a medical image diagnostic apparatus executes various processes has been described. However, the embodiment is not limited thereto. For example, an image processing system including the MRI apparatus 100 and the image processing apparatus may execute the various processes described above. Here, the image processing device is, for example, a workstation, an image storage device (image server) of a PACS (Picture Archiving and Communication System), a viewer, various devices of an electronic medical record system, or the like. In this case, for example, the MRI apparatus 100 performs collection by the sequence control unit 120. On the other hand, the image processing apparatus receives MR data or k-space data collected by the MRI apparatus 100 from the MRI apparatus 100 or from an image server via a network, or from an operator via a recording medium. It is received by being input and stored in the storage unit. Then, the image processing apparatus may perform the above-described various processing (for example, processing by the placement unit 133a and processing by the image generation unit 136) for the MR data and k-space data stored in the storage unit.

(program)
The instructions shown in the processing procedures shown in the above-described embodiments can be executed based on a program that is software. The general-purpose computer stores this program in advance and reads this program, so that the same effect as that obtained by the MRI apparatus 100 of the above-described embodiment can be obtained. The instructions described in the above-described embodiments are, as programs that can be executed by a computer, magnetic disks (flexible disks, hard disks, etc.), optical disks (CD-ROM, CD-R, CD-RW, DVD-ROM, DVD). ± R, DVD ± RW, etc.), semiconductor memory, or a similar recording medium. As long as the computer or embedded system can read the storage medium, the storage format may be any form. If the computer reads the program from the recording medium and causes the CPU to execute instructions described in the program based on the program, the same operation as the MRI apparatus 100 of the above-described embodiment can be realized. Further, when the computer acquires or reads the program, it may be acquired or read through a network.

  Further, an OS (Operating System) operating on a computer based on instructions from a program installed in a computer or an embedded system from a storage medium, database management software, MW (Middleware) such as a network, etc. A part of each process for realizing the above may be executed. Furthermore, the storage medium is not limited to a medium independent of a computer or an embedded system, but also includes a storage medium in which a program transmitted via a LAN (Local Area Network) or the Internet is downloaded and stored or temporarily stored. Further, the number of storage media is not limited to one, and the processing in the embodiment described above is executed from a plurality of media, and the configuration of the medium may be any configuration included in the storage medium in the embodiment. .

  The computer or the embedded system in the embodiment is for executing each process in the above-described embodiment based on a program stored in a storage medium, and includes a single device such as a personal computer or a microcomputer. The system may be any configuration such as a system connected to the network. In addition, the computer in the embodiment is not limited to a personal computer, and includes an arithmetic processing device, a microcomputer, and the like included in an information processing device, and is a generic term for devices and devices that can realize the functions in the embodiment by a program. .

  According to the magnetic resonance imaging apparatus and method of at least one embodiment described above, image quality can be improved under high-speed imaging.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 MRI apparatus 120 Sequence control part 133 Control part 133a Arrangement part 136 Image generation part

Claims (20)

By controlling the execution of the pulse sequence, a plurality of channels arranged at a first interval in a first region of k-space and arranged at a second interval wider than the first interval in a second region wider than the first region. A sequence controller that collects the minute magnetic resonance signals within a series of pulse sequences executed;
An arrangement unit for arranging magnetic resonance signals for the plurality of channels in k-space as k-space data;
Based on the k-space data of the second interval collected by the execution of the pulse sequence, the k-space data of the first interval for a plurality of channels is generated, the generated k-space data of the first interval, A magnetic resonance imaging apparatus comprising: an image generation unit configured to generate a magnetic resonance image based on k-space data of the first interval collected by execution and sensitivity distributions for a plurality of channels.   The plurality of sequence control units are arranged at a first interval in the first region, which is a central portion of k space, and are arranged at the second interval in the second region including a peripheral portion of k space. The magnetic resonance imaging apparatus according to claim 1, wherein magnetic resonance signals for channels are collected. The sequence control unit collects magnetic resonance signals arranged in the entire k-space with a combination of the first interval and the second interval for the first image, and the k-space for the second image at the first interval. Collect magnetic resonance signals placed in the center,
When generating the second image, the image generation unit collects k-space data arranged in the peripheral part of the k-space based on the k-space data collected for the first image and arranged in the k-space. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is filled.   The image generation unit arranges k-space data collected for the first image and arranged in the peripheral part of the k space corresponding to the first image in the peripheral part of the k space corresponding to the second image. The magnetic resonance imaging apparatus according to claim 3, wherein the magnetic resonance imaging apparatus is replicated as k-space data.   The image generation unit reconstructs an intermediate magnetic resonance image based on k-space data of the second interval collected for the first image, and reversely reconstructs the intermediate magnetic resonance image based on a sensitivity distribution. 4. The k-space data at the first interval is generated, and the generated k-space data at the first interval is duplicated as k-space data arranged in a peripheral portion of the k space corresponding to the second image. Magnetic resonance imaging equipment.   The image generation unit reconstructs an intermediate magnetic resonance image based on the k-space data of the second interval, and reversely reconstructs the intermediate magnetic resonance image based on a sensitivity distribution for a plurality of channels, thereby The magnetic resonance imaging apparatus according to claim 1, wherein k-space data of a first interval for a channel is generated.   The image generation unit reconstructs an intermediate magnetic resonance image based on the k-space data of the second interval, and reversely reconstructs the intermediate magnetic resonance image based on a sensitivity distribution for a plurality of channels, thereby The magnetic resonance imaging apparatus according to claim 2, wherein k-space data at a first interval for a channel is generated.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the sequence control unit continuously collects all magnetic resonance signals arranged in the k space at the first interval and the second interval without waiting time. .   The sequence control unit collects a magnetic resonance signal arranged in the k space at the first interval and a magnetic resonance signal arranged in the k space at the second interval with a waiting time, respectively. Item 2. The magnetic resonance imaging apparatus according to Item 1.   2. The sequence control unit according to claim 1, wherein the sequence control unit collects magnetic resonance signals arranged in the k-space at the first interval and the second interval as a result of collecting the magnetic resonance signals while waiting for a time. Magnetic resonance imaging device. When collecting magnetic resonance signals arranged in k-space divided into a plurality of segments, the sequence control unit collects one or a plurality of lines included in each segment from all segments in each TR (Repetition Time). And collecting the magnetic resonance signals arranged in the entire k-space by repeating the collection a plurality of TRs,
2. The magnetic field according to claim 1, wherein the magnetic field is collected so that the number of lines collected from the segment corresponding to the central portion of the k space is larger than the number of lines collected from the segment corresponding to the peripheral portion of the k space. Resonance imaging device. The sequence control unit collects magnetic resonance signals arranged in the entire k space in a combination of the first interval and the second interval in the first cardiac time phase, and k in the second cardiac time phase at the first interval. Collecting magnetic resonance signals placed in the center of the space,
When generating the second cardiac time phase image, the image generation unit is arranged in the peripheral part of the k space based on the k space data collected in the first cardiac time phase and arranged in the k space. The magnetic resonance imaging apparatus of claim 1, wherein the k-space data is filled.   The sequence control unit collects magnetic resonance signals arranged in the entire k-space at a combination of the first interval and the second interval during the systole, and is arranged at the center of the k-space at the first interval in the diastole The magnetic resonance imaging apparatus according to claim 12, wherein acquisition of a flip back pulse for returning the longitudinal magnetization of the nuclear spin is repeated after every acquisition of the magnetic resonance signal to be performed. When the sequence control unit collects magnetic resonance signals for a plurality of cardiac time phases while increasing the delay time from the characteristic wave within a predetermined interval from the systole to the diastole, for the cardiac phase as a reference, A magnetic resonance signal arranged in the entire k-space is collected by a combination of the first interval and the second interval, and for each other cardiac time phase, the magnetic resonance signal arranged in the central portion of the k-space at the first interval Collect and
When generating an image of each cardiac time phase, the image generation unit collects the reference cardiac time phase and arranges it in the peripheral part of the k space based on the k space data arranged in the k space. The magnetic resonance imaging apparatus according to claim 1, wherein the k-space data is filled.   The sequence control unit, when collecting magnetic resonance signals arranged at the center of k space at a first interval for each of the other cardiac time phases, outputs magnetic resonance signals for a plurality of cardiac time phases within one heartbeat. The magnetic resonance imaging apparatus according to claim 14, which is continuously collected. The sequence control unit collects magnetic resonance signals arranged in the entire k-space at a combination of the first interval and the second interval without applying a labeling pulse to the labeling region, and labels the labeling region. Collecting the magnetic resonance signals arranged in the central part of the k space at the first interval for each elapsed time while increasing the elapsed time after applying the activation pulse,
When generating an image to which a labeling pulse is applied, the image generating unit is collected without applying the labeling pulse, and is arranged in the peripheral part of the k space based on the k space data arranged in the k space. The magnetic resonance imaging apparatus of claim 1, wherein the k-space data is filled. The sequence control unit collects magnetic resonance signals arranged in the entire k space at a combination of the first interval and the second interval without administering the contrast agent, and after the contrast agent administration, the sequence control unit collects the magnetic resonance signals at the first interval. Magnetic resonance signals arranged at the center of the slab are collected continuously for multiple time phases,
When generating an image after administration of a contrast agent, the image generation unit collects the contrast agent without being administered, and arranges the image generation unit in a peripheral part of the k space based on k space data arranged in the k space. The magnetic resonance imaging apparatus of claim 1, wherein the magnetic resonance imaging apparatus is filled with k-space data. a memory for storing k-space data and a processor;
The processor is
By controlling the execution of the pulse sequence, a plurality of channels arranged at a first interval in a first region of k-space and arranged at a second interval wider than the first interval in a second region wider than the first region. Minute magnetic resonance signals are collected in a sequence of pulses executed in series,
The magnetic resonance signals for the plurality of channels are arranged in k space as k space data,
Based on the k-space data of the second interval collected by the execution of the pulse sequence, the k-space data of the first interval for a plurality of channels is generated, the generated k-space data of the first interval, A magnetic resonance imaging apparatus that generates a magnetic resonance image based on k-space data of first intervals collected by execution and sensitivity distributions for a plurality of channels. A magnetic resonance imaging method executed in a magnetic resonance imaging apparatus,
By controlling the execution of the pulse sequence, a plurality of channels arranged at a first interval in a first region of k-space and arranged at a second interval wider than the first interval in a second region wider than the first region. Minute magnetic resonance signals are collected in a sequence of pulses executed in series,
The magnetic resonance signals for the plurality of channels are arranged in k space as k space data,
Based on the k-space data of the second interval collected by the execution of the pulse sequence, the k-space data of the first interval for a plurality of channels is generated, the generated k-space data of the first interval, Generating a magnetic resonance image based on the k-space data of the first interval collected by the execution and the sensitivity distribution for a plurality of channels;
Magnetic resonance imaging method. a memory for storing k-space data and a processor;
The processor is
By controlling the execution of the pulse sequence, a plurality of channels arranged at a first interval in a first region of k-space and arranged at a second interval wider than the first interval in a second region wider than the first region. Minute magnetic resonance signals are collected in a sequence of pulses executed in series,
An arrangement unit for arranging magnetic resonance signals for the plurality of channels in k-space as k-space data;
A magnetic resonance imaging apparatus that generates a magnetic resonance image based on the k-space data and sensitivity distributions for a plurality of channels.

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