JP5922437B2 - Magnetic resonance equipment - Google Patents

Description

  The present invention relates to a magnetic resonance apparatus for imaging a subject based on a biological signal of the subject.

  A method for imaging the liver using a contrast agent is known (see Patent Document 1).

JP 2011-167408 A

  Since the liver is a part that moves by respiration, it is important to reduce body movement artifacts due to respiration. As one method for reducing body motion artifacts due to breathing, there is a method in which a subject holds his / her breath and the contrast agent is imaged while the subject is holding his / her breath. However, since the liver is located near the heart, artifacts due to heartbeat are also likely to occur. Therefore, it is also important to reduce body motion artifacts due to heartbeat. As a method of reducing body motion artifacts due to heartbeat, for example, a method of collecting data when the heart enters a diastole can be considered. However, when taking a contrast agent while the subject is holding his / her breath, the time to collect data cannot be limited to the diastole due to time constraints. Both need to collect data. Therefore, when collecting data in both diastole and systole, in order to reduce the influence of body motion artifacts, data in the low frequency region of k-space is collected in the diastole, while data in the high frequency region of k-space is collected. It is known how to collect the data during systole. In this method, the influence of heartbeat can be reduced to some extent, but on the other hand, there is a problem that a step difference in signal intensity becomes large at the boundary between the low frequency region and the high frequency region, and artifacts such as ghost are likely to occur. .

  Therefore, it is necessary to reduce the signal intensity step at the boundary between the low frequency region and the high frequency region as much as possible.

One aspect of the present invention is a determination means for determining a body movement state of the subject based on a biological signal of the subject;
Collecting view data in a low-frequency region of k-space when the subject is in a first body motion state, and a first high-frequency region in k-space when the subject is in a second body motion state; Scanning means for collecting view data in a second high frequency region;
A magnetic resonance apparatus comprising:
The first high frequency region has a first view adjacent to the low frequency region;
The second high frequency region has a second view adjacent to the low frequency region;
The low frequency region has a third view adjacent to the first view and a fourth view adjacent to the second view;
The scanning means includes
The data collection time difference Δt between the first view and the third view and the data collection time difference Δw between the second view and the fourth view satisfy the following conditions: This is a magnetic resonance apparatus that performs scanning.

Δt ≦ T
Δw ≦ T
Where T: period of biological signal

  By collecting data so that the time difference in data collection is equal to or less than one cycle of the biological signal, it is possible to reduce the step difference in signal intensity at the boundary between the high frequency region and the low frequency region.

1 is a schematic view of a magnetic resonance apparatus according to a first embodiment of the present invention. It is a figure which shows an imaging | photography site | part schematically. It is a figure which shows roughly the electrocardiogram signal and the sequence performed when scanning an imaging | photography site | part. It is a figure which shows roughly k space divided into the low frequency area | region and the high frequency area | region. It is explanatory drawing of ordering when collecting the data of each view of k space. View _V -51 data was _collected, V _-114, shows the _{V 52,} V _115. View _V -52 data was _collected, it shows a _{V -113, V 53, V 114} . It is explanatory drawing when collecting the data of the view of k space. It is a figure which shows the view from which data is collected by the sequence SQ of the i-7th time-i time. i + 1 th through i + 4 th sequence SQ view _V -51 data was collected _by, V _-114, shows the _{V 52,} V _115. i + 5 th through i + 8 th view _V -52 data was collected by the sequence _SQ, V _-113, shows the _{V 53,} V _114. It is a figure which shows the conditions of simulation Q1 and Q2. It is explanatory drawing of the ordering in simulation Q2. It is a figure which shows a simulation result. It is a figure which shows a simulation result. The (i + 1) -th to (i + m) -th sequence SQ is a diagram illustrating a case where data is collected according to ordering B, and data is collected according to ordering C from the i + (m + 1) -th sequence SQ. It is a figure which shows a simulation result. It is explanatory drawing of ordering when collecting the data of each view of k space in a 2nd form. View _V 51 the data has been _collected, V _26, V _-50, is a diagram showing a _{V -25.} View _V 50 the data has been _collected, V _27, V _-49, is a diagram showing a _{V -26.} It is explanatory drawing when collecting the data of the view of k space. j + 1-th to j + 4 th view _V 51 the data is collected by the sequence _SQ, V _26, V _-50, is a diagram showing a _{V -25.} It is explanatory drawing of ordering when collecting the data of each view of k space in a 3rd form. It is explanatory drawing when collecting the data of the view of k space. It is explanatory drawing of ordering when collecting the data of each view of k space in a 4th form. Shows a view _{V 52, V 115} the data was collected. Shows a view _{V 53, V 114} the data was collected. It is explanatory drawing when collecting the data of the view of k space. It is a figure which shows the view from which data are collected by the sequence SQ of the p-4th time-the pth time. The p + 1-th and p + 2 th sequence SQ is a diagram showing a view _{V 52, V 115} the data was collected. It is explanatory drawing of ordering when collecting the data of each view of k space in a 5th form. Shows a view _V 51, _{V 1} the data was collected. Shows a view _V 50, _{V 2} the data was collected. It is explanatory drawing when collecting the data of the view of k space. It is a figure which shows the view from which data are collected by the sequence SQ of the q-7th time-q time. The q + 1 th and q + 2 th sequence SQ is a diagram showing a view _V 51, _{V 1} the data was collected.

Hereinafter, although the form for inventing is demonstrated, this invention is not limited to the following forms.
(1) First Embodiment FIG. 1 is a schematic view of a magnetic resonance apparatus according to a first embodiment of the present invention.

  A magnetic resonance apparatus (hereinafter referred to as “MR apparatus”, MR: Magnetic Resonance) 100 includes a magnet 2, a table 3, a contrast medium injection device 4, a receiving coil 5, and the like.

  The magnet 2 includes a bore 21 in which the subject 14 is accommodated, a superconducting coil 22, a gradient coil 23, a transmission coil 24, and the like. The superconducting coil 22 applies a static magnetic field, the gradient coil 23 applies a gradient magnetic field, and the transmission coil 24 transmits an RF pulse. In place of the superconducting coil 22, a permanent magnet may be used.

  The table 3 has a cradle 3 a for supporting the subject 14. As the cradle 3a moves to the bore 21, the subject 14 is carried into the bore.

The contrast agent injection device 4 injects a contrast agent into the subject 14.
The receiving coil 5 is attached to the abdomen of the subject 14. A sensor 6 for acquiring an electrocardiogram signal is attached to the subject 14.

  The MR apparatus 100 further includes a sequencer 7, a transmitter 8, a gradient magnetic field power supply 9, a receiver 10, a control unit 11, an operation unit 12, and a display unit 13.

  Under the control of the control unit 11, the sequencer 7 sends information for executing the pulse sequence to the transmitter 8 and the gradient magnetic field power supply 9.

The transmitter 8 supplies current to the RF coil 24.
The gradient magnetic field power supply 9 supplies a current to the gradient coil 23.

  The receiver 10 processes the magnetic resonance signal received by the receiving coil 5 and outputs the signal to the control unit 11. A combination of the magnet 2, the receiving coil 5, the sequencer 7, the transmitter 8, the gradient magnetic field power source 9, and the receiver 10 corresponds to the scanning means.

  The control unit 11 transmits necessary information to the sequencer 7 and the display unit 13, and reconstructs an image based on data received from the receiver 10, so as to realize various operations of the MR apparatus 100. The operation of each part of the MR apparatus 100 is controlled. The control part 11 is comprised by the computer (computer), for example. The control unit 11 includes a determination unit 11a and a view setting unit 11b.

  The determination unit 11 a determines whether the heart is in a systole or a diastole based on the electrocardiogram signal acquired by the sensor 6.

  The view setting unit 11b sets a view for collecting k-space data based on the determination result of the determination unit 11a.

  The control part 11 is an example which comprises the judgment means 11a and the view setting means 11b, and functions as these means by running a predetermined program.

The operation unit 12 is operated by an operator and inputs various information to the control unit 11. The display unit 13 displays various information.
The MR apparatus 100 is configured as described above.

  FIG. 2 is a diagram schematically illustrating an imaging region, and FIG. 3 is a diagram schematically illustrating an electrocardiogram signal and a sequence executed when the imaging region is scanned.

  In this embodiment, a sequence SQ for acquiring data of an imaging region including the liver while acquiring an electrocardiogram signal in a state where a contrast medium is injected into the subject 14 and the subject 14 holds the breath. Execute. The sequence SQ is repeatedly executed at the repetition time TR.

In this embodiment, when data is embedded in the k space, the k space is divided into a low frequency region and a high frequency region. FIG. 4 is a diagram schematically showing a k-space divided into a low frequency region and a high frequency region. In FIG. 4, k-space with 256 views V _{−127 to} V ₁₂₈ is shown. The k space is divided into a low frequency region _RC and high frequency regions R _O1 and R _O2 . In the first embodiment, the low-frequency region _{R C} includes the view V _over 50 _{~V 51,} the high frequency region _{R O1} includes the view _V 52 _{~V 128,} the high frequency region _{R O2} is It is assumed that views V _{−51 to} V ₋₁₂₇ are included. However, the way of dividing the views included in the low frequency region R _C and the high frequency regions R _O1 and R _O2 is not limited to that in FIG. 4, and various methods can be used.

In the first embodiment, the view data of the low frequency region _RC is collected in the diastole of the heart, and the view data of the high frequency regions R _O1 and R _O2 is collected in the systole of the heart. However, view data for the low frequency region _RC may be collected during the systole of the heart, and view data for the high frequency regions R _O1 and R _O2 may be collected during the diastole of the heart. When all the data in the low frequency region _RC is filled and there is a view in the high frequency region R _O1 or R _O2 for which data has not yet been collected, the data is displayed in both diastole and systole. To collect.

  FIG. 5 is an explanatory diagram of ordering when data of each view in the k space is collected.

The ordering A indicates the ordering when collecting the view data of the low frequency region _RC , and the ordering B indicates the ordering when collecting the view data of the high frequency regions R _O1 and R _O2 . The order in which data is collected in each ordering is shown in parentheses.

In the diastole, the view data of the low frequency region _RC is collected according to ordering A. Ordering A first collects data of view V ₀ , collects data of view V ₀ , and then collects data of positive view and data of negative view alternately in order from view V ₀ ( So-called centric ordering). In FIG. 5, the data of the view V- ₅₀ adjacent to the high frequency region R _O2 is collected at the 101st, and the data of the view V ₅₁ adjacent to the high frequency region R _O1 is collected at the 102nd.

On the other hand, in the systole, view data of the high frequency regions R _O1 and R _O2 are collected according to the ordering B. The ordering B is an ordering (so-called reverse centric ordering) in which positive view data and negative view data in the high frequency regions R _O1 and R _O2 are alternately collected in order of increasing distance from the low frequency region _RC . First, data of the view V ₁₂₈ in the high frequency region R _O1 is collected, and second, data of the view V _-127 in the high frequency region R _O2 is collected. Hereinafter, positive view data and negative view data are alternately collected in order of increasing distance from the low frequency region _RC .

As described above, the view data of the low frequency region _RC is collected in the diastole, and the view data of the high frequency regions R _O1 and R _O2 is collected in the systole. Therefore, depending on the number of views in which data is collected in the systole and the number of views in which data is collected in the diastole, data collection of all views in the low frequency region _RC may be completed first. In some cases, the collection of data for all views of the high-frequency regions R _O1 and R _O2 is completed first. In FIG. 5, the collection of data for all views in the low frequency region _RC has been completed first, but the data uncollected regions a1 and a2 for which data has not yet been collected are present in the high frequency regions R _O1 and R _O2. Shown for cases included. In the first form, the data uncollected area a1 of the high frequency region R _O1 includes the views V _{52 to} V ₁₁₅ , and the data uncollected area a2 of the high frequency region R _O2 includes the views V _{-51 to} V _-114 . Contains. Data of these views is collected by ordering C different from ordering B. The ordering C will be specifically described below.

In ordering C, the following steps S1 to S4 are executed.

(Step S1) Among the views included in the data uncollected region a2 of the high frequency region R _O2 , the data of the view closest to the low frequency region _RC is collected.
(Step S2) Among the views included in the data uncollected area a2 of the high frequency area R _O2 , the data of the view farthest from the low frequency area _RC is collected.
(Step S3) Among the views included in the data uncollected area a1 of the high frequency area R _O1 , the data of the view closest to the low frequency area _RC is collected.
(Step S4) Among the views included in the data uncollected area a1 of the high frequency area R _O1 , the data of the view farthest from the low frequency area _RC is collected.

Referring to FIG. 5, the data non-acquisition region a2 of the high frequency region _{R O2,} which contains the view V _over 51 ~V _{over 114} data is not being collected. Among the views V _{-51 to} V _-114 in which data is not collected, the view closest to the low frequency region _RC is the view V- ₅₁ , and the view farthest from the low frequency region _RC is the view V _{−. 114} . Therefore, in step S1, data of the view V- ₅₁ is collected, and in step S2, data of the view V- ₁₁₄ is collected.

On the other hand, the data non-collection area a1 of the high-frequency area R _O1 includes views V _{52 to} V ₁₁₅ where data is not collected. Among the views V _{52 to} V ₁₁₅ for which data is not collected, the view closest to the low frequency region _RC is the view V ₅₂ , and the view farthest from the low frequency region _RC is the view V ₁₁₅ . Therefore, in step S3, data of the view V ₅₂ is collected, and in step S4, data of the view V ₁₁₅ is collected. 6, the view _V -51 data was _collected, V _-114, shows the V _{52, V 115.}

By executing the steps S1 to S4, view _{V -51, V -114,} data is collected in the order of _{V 52,} V _115. Referring to FIG. 6, in the high-frequency regions R _O1 and R _O2 , there are still data uncollected regions where data is not collected. In this case, the ordering C executes steps S1 to S4 again.

Referring to FIG. 6, the data non-acquisition region a2 of the high frequency region _{R O2,} which contains the view _V -52 _{~V -113} which data has not been collected. Among the views V _{-52 to} V _-113 in which data is not collected, the view closest to the low frequency region _RC is the view V- ₅₂ , and the view farthest from the low frequency region _RC is the view V _{−. 113} . Therefore, in step S1, data of the view V- ₅₂ is collected, and in step S2, data of the view V- ₁₁₃ is collected.

On the other hand, the data non-collection area a1 of the high-frequency area R _O1 includes views V _{53 to} V _{114 in} which no data is collected. Among the views V _{53 to} V ₁₁₄ for which data is not collected, the view closest to the low frequency region _RC is the view V ₅₃ , and the view farthest from the low frequency region _RC is the view V ₁₁₄ . Therefore, in step S3, data of the view V ₅₃ is collected, and in step S4, data of the view V ₁₁₄ is collected. Figure 7 shows a view _V -52 data was _{collected, V -113, V 53, V} 114.

View _{V -52,} V _-113, When data V _{53, V 114} is collected, and so on, the view _V 54 _{~V 113} contained in the data non-acquisition region a1 of the high-frequency region _{R O1} data, and until the data in the view _V -53 _{~V -112} contained in the data non-acquisition region a2 of the high frequency region _{R O2} is collected, step S1~S4 are repeatedly executed.

  In the above example, steps S1 to S4 are executed in the order of steps S1, S2, S3, and S4. However, as long as steps S1 to S4 are executed, the order is not limited to steps S1, S2, S3, and S4. For example, the order of steps S3, S4, S1, and S2 may be used, or the order of steps S1, S3, S2, and S4 may be used.

  In this embodiment, data of each view in k space is collected according to ordering A, B, and C while acquiring an electrocardiogram signal (cardiac cycle T). Hereinafter, the order in which the data of each view is collected will be described more specifically with reference to FIGS. 8 to 11 together with FIGS.

  FIG. 8 is an explanatory diagram when collecting k-space view data. FIG. 8 shows a view in which data is collected by the first to tenth sequences SQ.

  When executing the sequence SQ, the determination unit 11a (see FIG. 1) determines whether it is diastole or systole based on the electrocardiogram signal acquired by the sensor 6. As a method of determining whether it is a diastole or a systole, for example, there is a method of measuring an elapsed time from an R wave of an electrocardiogram signal and determining based on the measured elapsed time.

The view setting unit 11b (see FIG. 1) sets a view for collecting data based on whether the heart is in diastole or systole. When the systole is determined, the view data of the high frequency region R _O1 or R _O2 is collected according to the ordering B (see FIG. 5), and when it is determined as the diastole, the data is low according to the ordering A (see FIG. 5). collecting data of a view of the frequency region R _c. Since the time point t ₁ is a systole, the view data of the high frequency region R _O1 or R _O2 is collected according to the ordering B. Therefore, the view setting unit 11b sets the view V ₁₂₈ of the high frequency region _R01 as a view when data is collected in the first sequence SQ. Since the view V ₁₂₈ of the high frequency region R _O1 is set, the data of the view V ₁₂₈ is collected in the first sequence SQ.

After collecting the data in the view _{V 128,} determination unit 11a is the time _{t 2} it is determined whether diastolic or systolic (see FIG. 8). Since the time _{t 2} is the systolic, even the second sequence SQ, collects data of the view of the high frequency region _{R O1} or _{R O2} accordance ordering B. Therefore, the view setting unit 11b sets the view V- ₁₂₇ of the high-frequency region R _O2 according to the ordering B. Since the view V- ₁₂₇ is set, the data of the view V- ₁₂₇ is collected in the second sequence SQ.

After collecting the data in the view _{V -127,} determination unit 11a is the time _{t 3} it is determined whether diastolic or systolic. Since the time t ₃ is diastolic, the third sequence SQ, to collect data of the low frequency region R _c view according ordering A (see FIG. 5). Thus, the view setting section 11b is, as a view when collecting data in third sequence SQ, sets the view V ₀ which the low-frequency region R _C. Since the view V ₀ of the low frequency region _RC is set, the data of the view V ₀ is collected in the third sequence SQ.

When executing the sequence SQ after the fourth time, it is determined whether it is a diastole or a systole. If it is determined that it is a systole, the view data of the high-frequency region R _O1 or R _O2 is collected according to the ordering B, If it is determined as the diastole, view data in the low frequency region _RC is collected according to ordering A. Referring to FIG. 8, since the fourth to tenth sequences SQ are executed in the expansion period, the views V ₁ , V ₋₁ , V ₂ , V ₋₂ , V _{3 of the} low frequency region _RC according to the ordering A. , V ₋₃ , V ₄ are collected in order. Therefore, the data of the views V _{-3 to} V _{4 in} the low frequency region _RC are collected by the third to tenth sequences SQ.

Similarly, it is determined whether it is a diastole or a systole, and when it is determined that it is a systole, the view data of the high frequency region R _O1 or R _O2 is collected according to the ordering B, and when it is determined that it is a diastole, According to ordering A, the view data of the low frequency region _RC is collected. Therefore, each time the sequence SQ is executed, data is sequentially arranged in each view of the k space.

  FIG. 9 is a diagram illustrating a view in which data is collected by the i-7th to i-th sequence SQ.

Since the i-7th and i-6th sequences SQ are executed in the systole, high-frequency region view data is collected according to ordering B. In Figure 9, the data of the view _{V 116} of the high-frequency region _{R O1} is collected by i-7 th sequence SQ, view data _{V -115} high frequency region _{R O2} is collected by i-6 th sequence SQ. Further, since the i-5th to i-th sequence SQ is executed in the expansion period, view data of the low frequency region _RC is collected. Here, the i-5 th ~i th sequence SQ, the low-frequency region _{R C} of view V _{over 48, V} 49, V _{over 49,} V _50, V _-50, data _{V 51} is collected. When the i-th sequence SQ has been completed, the collection of data of all views _V -50 _{~V 51} of the low-frequency region _{R C} is completed.

Next, data collected by the (i + 1) th and subsequent sequences SQ will be described.
Referring to FIG. 9, all view data are collected in the low frequency region _RC . However, in the high frequency region R _O1, there is a data uncollected region a1 where data has not yet been collected, and in the high frequency region R _O2, there is a data uncollected region a2 where data has not yet been collected. Yes. The data non-acquisition region a1, includes the view _V 52 _{~V 115,} the data uncollected region a2 is included the view _V -51 _{~V -114.} Therefore, i + 1 and subsequent sequence SQ is performed to collect these views _V 52 _{~V 115} and views _V -51 _{~V -114.} Data for these views V _{52 to} V ₁₁₅ and views V _{−51 to} V ₋₁₁₄ are collected according to ordering C (see FIGS. 6 and 7). In addition, in the sequence SQ after the (i + 1) th time, since it is not necessary to collect the view data of the low frequency region _RC , it is used not only for the systole but also for the diastole to collect the view data of the high frequency region. . Thereby, the data of the view of the data uncollected area can be acquired in a short time.

  In ordering C, first, as described with reference to FIG. 6, data is collected according to steps S1 to S4.

  In this embodiment, ordering C starts from the (i + 1) th sequence SQ. Accordingly, when the i + 1-th to i + 4-th sequence SQ is executed, data is collected according to steps S1 to S4.

In i + 1 th sequence SQ, according to step S1, the data of the high frequency region _{R O2} in included in the view V _over 51 ~V _{over 114} is a data uncollected region a2, the low-frequency region _R closest to the _C view V _{over 51} To collect.
In i + 2 th sequence SQ, according to step S2, data of the high frequency region _{R O2} in in the view V _over 51 ~V _{over 114} included in the data non-acquisition region a2, the low-frequency region _{R C} from the farthest view V _{over 114} To collect.
In i + 3 th sequence SQ, according to step S3, in a view _V 52 _{~V 115} included in the data non-acquisition region a1 of the high-frequency region _{R O1,} collects data closest view _{V 52} in the low frequency region _{R C} .
In the (i + 4) th sequence SQ, the data of the view V ₁₁₅ farthest from the low frequency region _RC among the views V _{52 to} V ₁₁₅ included in the data uncollected region a1 of the high frequency region R _O1 is collected according to step S4. .

FIG. 10 shows views V ₋₅₁ , V ₋₁₁₄ , V ₅₂ , and V _{115 in} which data is collected by the (i + 1) th to i + 4th sequence SQ. At the boundary between the high frequency region R _O2 and the low frequency region _RC , the views V- ₅₀ and V- ₅₁ are adjacent to each other. At the boundary between the high frequency region R _O1 and the low frequency region _RC , the view V ₅₁ and _V52 is adjacent. Referring to FIG. 10, it can be seen that the data collection time difference Δt between adjacent views V ₋₅₀ and V _{−51 and} the data collection time difference Δw between adjacent views V ₅₁ and V ₅₂ are smaller than the cardiac cycle T.

The high-frequency region R _O1 includes a data uncollected region a1 (views V _{53 to} V ₁₁₄ ) for which data has not been collected yet, and the high-frequency region R _O2 includes data for which data has not yet been collected. An uncollected area a2 (views V- _{52 to} V- ₁₁₃ ) is included. Therefore, steps S1 to S4 are executed again in the (i + 5) th and subsequent sequences SQ.

In i + 5 th sequence SQ, according to step S1, the high-frequency region in _{R O2} of view V _over 52 ~V _{over 113} included in the data non-acquisition region a2, the low-frequency region _{R C} closest data view V _{over 52} To collect.
In i + 6 th sequence SQ, according to step S2, data of the high frequency region _R in the view V _over 52 ~V _{over 113} included in the data non-acquisition region a2 of the _O2, the low-frequency region _R farthest from _C view V _{over 113} To collect.
In i + 7 th sequence SQ, according to step S3, in a view _V 53 _{~V 114} included in the data non-acquisition region a1 of the high-frequency region _{R O1,} collects data closest view _{V 53} in the low frequency region _{R C} .
In the (i + 8) th sequence SQ, the data of the view V ₁₁₄ farthest from the low frequency region _RC among the views V _{53 to} V ₁₁₄ included in the data uncollected region a1 of the high frequency region R _O1 is collected according to step S4. .

FIG. 11 shows views V ₋₅₂ , V ₋₁₁₃ , V ₅₃ , and V _{114 in} which data is collected by the i + 5th to i + 8th sequence SQ. Referring to FIG. 11, the high frequency region R _O1 still includes the views V _{54 to} V ₁₁₃ for which no data is collected, and the high frequency region R _O2 includes the view V ₋ for which no data is collected. _53- V- ₁₁₂ is still included. Therefore, the i + 9 and subsequent sequence SQ, until the data of the remaining views _V -53 _{~V -112} and _V 54 _{~V 113} of the high frequency region are collected, step S1~S4 are repeatedly executed. In this way, data for all views in k-space are collected.

In the present embodiment, in the low frequency region _RC , the data of the central view V ₀ is first collected according to the ordering A, and then the data of the positive view and the data of the negative view are alternately arranged in the order closer to the view V _0. To be collected. On the other hand, in the high-frequency regions R _O1 and R _O2 , initially, the data of the view far from the low-frequency region _RC is first collected according to the ordering B, but the data of all the views in the low-frequency region _RC is collected. After that, data is collected according to ordering C. By collecting data in such an order, the step difference in signal strength between adjacent views can be reduced, so that image data with reduced artifacts can be obtained. In order to verify this, two simulations Q1 and Q2 were performed. Hereinafter, two simulations Q1 and Q2 will be described.

FIG. 12 is a diagram showing conditions for simulations Q1 and Q2.
In simulation Q1, data was collected according to the ordering of this embodiment. That is, as shown in FIGS. 5, 6, and 7, the view data of the low frequency region _RC is collected according to the ordering A, and the view data of the high frequency regions R _O1 and R _O2 is collected according to the ordering B and C. did.

On the other hand, in the simulation Q2, data was collected according to an ordering different from the simulation Q2. FIG. 13 is an explanatory diagram of ordering in the simulation Q2. In the simulation Q2, the view data in the low frequency region _RC was collected according to the ordering A as in the simulation Q1. However, the view data of the high frequency regions R _O1 and R _O2 were collected according to another ordering D, unlike the simulation Q1. The ordering D is ordering (so-called centric ordering) in which positive view data and negative view data are alternately collected in the order close to the low frequency region _RC .

The number of views of the low-frequency region _{R C} of the k-space, the number of views of the high-frequency region _{R O1} of k-space, the number of views of the high-frequency region _{R O2} k-space, the sequence SQ TR, cardiac cycle T is the same Simulation conditions were used.

14 and 15 are diagrams showing simulation results.
FIG. 14 is a graph showing the relationship between each view obtained by simulation Q1 and the data collection time point, and FIG. 15 is a graph showing the relationship between each view obtained by simulation Q2 and the data collection time point.

The simulation Q2 in FIG. 15, since the data in the low frequency region _{R C} of view V _over 50 _{~V 51} are collected according to ordering A (see FIG. 13), data in the view _{V 0} is first collected, then the view The data of the positive view and the negative view are collected alternately in order from V ₀ . Therefore, the further away from the view V ₀ , the later the time at which data is collected, and the data of the view V _{−50 in} the low frequency region Rc is collected at time t ₋₅₀ . On the other hand, since the view data of the high frequency regions R _O1 and R _O2 is collected according to the ordering D (see FIG. 13), the data is collected first from the view close to the low frequency region Rc. Thus, the simulation Q2, view data _{V -51} of the high-frequency region _{R O1} is collected at time _{t -51} immediately after the start of the data collection k-space. Therefore, the boundary between the low frequency region R _C and the high frequency region R _O2, cause large time difference Δt to the acquisition time of the data between adjacent views V _-50 and views V _-51, step of the signal strength growing.

In the above description, the boundary portion between the low frequency region _RC and the high frequency region R _O2 has been described, but the same can be considered for the boundary portion between the low frequency region _RC and the high frequency region R _O1 . The view V ₅₁ and the view V ₅₂ are adjacent to each other at the boundary between the low frequency region _RC and the high frequency region R _O1 . A large time difference Δw also occurs in the data collection time between the adjacent views V ₅₁ and V _52, and the step difference in signal intensity also increases.

Therefore, in FIG. 15, a step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 increases, and the image quality deteriorates.

On the other hand, in the simulation Q1 of FIG. 14, the view data of the low frequency region _RC is collected according to the ordering A (see FIG. 5), similarly to the simulation Q2. However, unlike the simulation Q2, the view data of the high frequency regions R _O1 and R _O2 are initially collected according to the ordering B, and when the data of all the views of the low frequency region R _C are collected, the data is switched to the ordering C. In ordering C, since data is collected according to steps S1 to S4, data of the view V- ₅₁ is collected in a short time after data of the view V- _{50 in} the low frequency region _RC is collected. . Therefore, the boundary between the low frequency region R _C and the high frequency region R _O2, it is possible to reduce the time difference Δt of data collection between adjacent views V _-50 and views V _-51, the signal strength level difference Can be reduced. Similarly, the data collection time difference Δw between the adjacent views V ₅₁ and V ₅₂ can be reduced even at the boundary portion between the low frequency region _RC and the high frequency region R _O1 , so that the signal intensity level difference can be reduced. Can be small.

Therefore, in FIG. 14, the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 can be reduced, so that the image quality can be improved.

Further, by collecting the data of the high-frequency region views V _{52 to} V ₁₁₅ and V _{−51 to} V _{−114 in} the ordering C, the data is collected in the order V and the view V ₁₁₆ in which the data is collected in the ordering B. The time difference in data collection with the view V ₁₁₅ can also be reduced. Therefore, it is possible to reduce the signal intensity difference between the views V ₁₁₅ and V ₁₁₆ in which data is collected with different ordering in the high frequency region R _O1 . Similarly, it is possible to step the signal strength between the views V _-114 and V _-115 to data in different ordering within the high frequency region R _O2 is collected also reduced. Therefore, the image quality can be further improved.

In the above example, as shown in FIG. 10, after collecting the data of all views in the low frequency region _RC by the i-th sequence SQ, the sequence SQ after the (i + 1) th time is the rest of the high-frequency region according to the ordering C. Collecting view data. However, even in the sequence SQ after the (i + 1) th time, data may be collected initially according to ordering B, and data may be collected according to ordering C from the middle. FIG. 16 shows a case where data is collected according to ordering B in the (i + 1) -th to i + m-th sequence SQ, and data is collected according to ordering C from the i + (m + 1) -th sequence SQ. In ordering B, so to collect data view farthest from the low-frequency region R _C, while being gathered by ordering B, the data in the view V _-51 and V ₅₂ are not collected. Thus, only the period x running ordering B, the time difference Δt of data collection between adjacent views _{V -50} and views _{V -51} becomes long, between the views _{V 51} and views _{V 52} adjacent The time difference Δw for data collection also becomes longer. However, Kirikaware from ordering B in ordering C, since the data in the view V _-51 and V ₅₂ are immediately collected, if the period x the ordering B is short, the time difference Δt and Δw can be sufficiently short, the signal strength The step can be reduced. However, if the period x of the ordering B is made too long, the time differences Δt and Δw become long, so that the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 increases, and the image quality is improved. to degrade. Therefore, in order to maintain good image quality, it is desirable that the time differences Δt and Δw are short. In order to verify this, a simulation was performed to examine how the image quality changes when the time difference between Δt and Δw is changed by changing the length of the period x of the ordering B. .

FIG. 17 is a diagram showing the simulation result.
The horizontal axis of the graph represents the values of the time differences Δt and Δw, and the vertical axis represents information entropy that serves as a ghost index. A smaller value of information entropy means that ghost is reduced.

  The information entropy increases with each cardiac cycle T as the time differences Δt and Δw increase. Therefore, if Δt and Δw are small, the information entropy can be set to a small value, so that the ghost can be reduced. Referring to the graph of FIG. 17, it can be seen that the information entropy can be sufficiently reduced if both the time differences Δt and Δw are within the cardiac cycle T. Therefore, by setting both the time differences Δt and Δw to the cardiac cycle T or less, an image with reduced ghost can be obtained. For this reason, it is desirable to set Δt and Δw to be equal to or less than the cardiac cycle T.

(2) Second Mode In the first mode, an example in which data of all views in the low frequency region _RC is first collected before data of all views of the high frequency regions R _O1 and R _O2 is collected. Explained. In the second embodiment, ordering will be described in a case where data of all views in the high frequency regions R _O1 and R _O2 is first collected before data of all views in the low frequency region _RC is collected. The hardware configuration of the MR apparatus is the same as that in the first embodiment.

FIG. 18 is an explanatory diagram of ordering when data of each view in the k space is collected in the second mode. Ordering A indicates ordering when data of views in the low frequency region _RC is collected, and ordering B indicates ordering of views in the high frequency regions R _O1 and R _O2 . The order in which data is collected in each ordering is shown in parentheses.

In the diastole, the view data of the low frequency region _RC is collected according to ordering A. As in the first embodiment, the ordering A first collects data of the view V ₀ , collects data of the view V ₀ , and then collects data of the positive view and the negative view in order from the view V ₀ . This is ordering that collects data alternately (so-called centric ordering).

On the other hand, in the systole, view data of the high frequency regions R _O1 and R _O2 are collected according to the ordering B.

The ordering B is an ordering (so-called inverse centric ordering) in which positive view data and negative view data are alternately collected in the order of distance from the low frequency region _RC , as in the second embodiment. First, data of the view V ₁₂₈ in the high frequency region R _O1 is collected, and second, data of the view V _-127 in the high frequency region R _O2 is collected. Hereinafter, positive view data and negative view data are alternately collected in order of increasing distance from the low frequency region _RC .

In FIG. 18, the collection of data for all the views in the high-frequency regions R _O1 and R _O2 has been completed first, but in the low-frequency region R _C , data uncollected regions b1 and b2 for which data has not yet been collected. Existing. In the second embodiment, the data uncollected area b1 includes a view _V 26 _{~V 51,} data uncollected area b2 includes a view V _over 25 ~V _-50. Data of these views is collected by ordering E different from ordering B. The ordering E will be specifically described below.

In ordering E, the following steps S1 to S4 are executed.

(Step S1) Among the views included in the data uncollected region b1 in the low frequency region _RC , data of a view closest to the high frequency region _RO1 is collected.
(Step S2) Among the views included in the low-frequency region _RC data uncollected region b1, the data of the view farthest from the high-frequency region _RO1 is collected.
(Step S3) Among the views included in the low-frequency region _RC data uncollected region b2, the data of the view closest to the high-frequency region _RO2 is collected.
(Step S4) Among the views included in the low-frequency region _RC data uncollected region b2, the data of the view farthest from the high-frequency region _RO2 is collected.

Referring to FIG. 18, the data uncollected region b1 in the low frequency region _RC includes views V _{26 to} V _{51 in} which no data is collected. Among the views V _{26 to} V ₅₁ for which data is not collected, the view closest to the high frequency region R _O1 is the view V ₅₁ , and the view farthest from the high frequency region R _O1 is the view V ₂₆ . Accordingly, in step S1, data of the view V ₅₁ is collected, and in step S2, data of the view V ₂₆ is collected.

On the other hand, the data uncollected region b2 in the low frequency region _RC includes views V _{-25 to} V _{-50 in} which no data is collected. In the view V _over 25 ~V _{over 50} data is not being collected, closest view to the high frequency region _{R O2} is view _{V -50,} farthest view from the high-frequency region _{R O2} is a view _{V -25} is there. Therefore, in step S3, data of the view V- ₅₀ is collected, and in step S4, data of the view V- ₂₅ is collected. 19, view _V 51 the data has been _collected, V _26, V _-50, shows a _{V -25.}

By executing the steps S1 to S4, view _{V 51, V 26, V -50} , data is collected in the order of _{V -25.} Referring to FIG. 19, in the low frequency region _RC , there is still a data uncollected region where data is not collected. In this case, the ordering E executes steps S1 to S4 again. The data non-collection region b1 in the low frequency region _RC includes views V _{27 to} V _{50 in} which no data is collected. Of the views V _{27 to} V ₅₀ for which data is not collected, the view closest to the high frequency region R _O1 is the view V ₅₀ , and the view farthest from the high frequency region R _O1 is the view V ₂₇ . Therefore, in step S1, data of the view V ₅₀ is collected, and in step S2, data of the view V ₂₇ is collected.

On the other hand, the data non-collection region b2 in the low frequency region _RC includes views V _{-26 to} V _{-49 in} which no data is collected. Of the views V _{-26 to} V _-49 for which data is not collected, the view closest to the high frequency region R _O2 is the view V- ₄₉ , and the view farthest from the high frequency region R _O2 is the view V- ₂₆ . is there. Therefore, in step S3, data of view V- ₄₉ is collected, and in step S4, data of view V- ₂₆ is collected. FIG. 20 shows views V ₅₀ , V ₂₇ , V ₋₄₉ , V _{−26 from} which data was collected.

When the data of the views V ₅₀ , V ₂₇ , V ₋₄₉ , and V ₋₂₆ are collected, the data of the views V _{28 to} V ₄₉ included in the data uncollected area b1 of the low frequency area _RC are similarly stored. Steps S1 to S4 are repeatedly executed until the data of the views V- _{27 to} V- ₄₈ included in the data uncollected area b2 are collected.

  In the above example, steps S1 to S4 are executed in the order of steps S1, S2, S3, and S4. However, as long as steps S1 to S4 are executed, the order is not limited to steps S1, S2, S3, and S4. For example, the order of steps S3, S4, S1, and S2 may be used, or the order of steps S1, S3, S2, and S4 may be used.

  In the second mode, data of each view in k-space is collected according to ordering A, B, and E while acquiring an electrocardiogram signal (cardiac cycle T). Hereinafter, the order in which the data of each view is collected will be described with reference to FIG.

  FIG. 21 is an explanatory diagram when collecting k-space view data. FIG. 21 shows a view in which data is collected by the sequence SQ of the j-7th to jth times.

Since the j-7th and j-6th sequences SQ are executed in the expansion period, the view data in the low frequency region _RC is collected according to the ordering A. In Figure 21, the data of the view _{V -24} in a low frequency region _{R C} is collected by the j-7 th sequence SQ, view data _{V 25} of the low-frequency region _{R C} is collected by the j-6 th sequence SQ The Further, since the j-5th to jth sequence SQ is executed in the systole, the view data of the high frequency regions R _O1 and R _O2 is collected. Here, the j-5 th ~j th sequence SQ, view _V 54 of the high-frequency region _{R O1} and _{R O2, V -53, V 53} , V -52, data V _{52, V -51} are collected . When the j-th sequence SQ is completed, data collection for all views in the high-frequency regions R _O1 and R _O2 is completed.

Next, data collected by the sequence SQ after the j + 1th time will be described.
Referring to FIG. 21, in the high frequency regions R _O1 and R _O2 , data of all views are collected. However, in the low frequency region _RC, there are data uncollected regions b1 and b2 for which data has not yet been collected. The data non-acquisition region b1, includes the view _V 26 _{~V 51,} the data uncollected area b2 is included the view _V -25 _{~V -50.} Accordingly, j + 1 and subsequent sequence SQ is performed to collect data for these views _V 26 _{~V 51} and _V -25 _{~V -50.} Data of these views _V 26 _{~V 51} and _V -25 _{~V -50} are collected in accordance with ordering E (see FIG. 19 and FIG. 20).

  In ordering E, as described above, data is collected according to steps S1 to S4.

  In the second mode, the ordering E is started from the (j + 1) th sequence SQ. Accordingly, when the j + 1-th to j + 4th sequence SQ is executed, data is collected according to steps S1 to S4.

In the (j + 1) -th sequence SQ, data of the view V ₅₁ closest to the high frequency region R _O1 among the views V _{26 to} V ₅₁ included in the data uncollected region b1 of the low frequency region R _C is collected according to step S1. .
In the j + 2th sequence SQ, the data of the view V ₂₆ farthest from the high-frequency region R _O1 among the views V _{26 to} V ₅₁ included in the data uncollected region b1 of the low-frequency region R _C is collected according to step S2. .
In j + 3 th sequence SQ, according to step S3, in a view V _over 25 ~V _{over 50} included in the low frequency region _{R C} data uncollected area b2, the closest view V _{over 50} data in the high frequency region _{R O2} To collect.
In j + 4 th sequence SQ, according to step S4, in a view V _over 25 ~V _{over 50} included in the low frequency region _{R C} data uncollected area b2, a high frequency region farthest view V _{over 25} data from _{R O2} To collect.

FIG. 22 shows views V ₅₁ , V ₂₆ , V ₋₅₀ , and V _{−25 in} which data is collected by the sequence SQ from the (j + 1) th time to the (j + 4) th time. The views V ₅₁ and V ₅₂ are adjacent to each other at the boundary between the high frequency region R _O1 and the low frequency region _RC, and the views V ₋₅₀ and V ₅₂ are adjacent to each other at the boundary between the high frequency region R _O2 and the low frequency region _{RC. -51} is adjacent. Referring to FIG. 22, it can be seen that the data collection time difference Δt between adjacent views V ₅₁ and V _{52 and} the data collection time difference Δw between adjacent views V ₋₅₀ and V ₋₅₁ are smaller than the cardiac cycle T.

Note that the low frequency region _RC still includes views V _{27 to} V ₅₀ and views V _{−26 to} V ₋₄₉ for which data is not collected. Therefore, in the sequence SQ after j + 5, steps S1 to S4 are repeatedly executed until data of the remaining views V _{27 to} V ₅₀ and views V _{−26 to} V _{−49 in} the low frequency region are collected. In this way, data for all views in k-space are collected.

In the second form, the view data of the low frequency region _RC is initially collected according to the ordering A, but after the data of all the views of the high frequency regions R _O1 and R _O2 are collected, from the ordering A Switch to ordering E. Therefore, since data of the view V ₅₁ of the low frequency region _RC is collected in a short time after the data of the view V ₅₂ of the high frequency region R _O2 is collected, the adjacent views V ₅₁ and V ₅₂ The data collection time difference Δt can be made equal to or less than the cardiac cycle T. Similarly, it can be below the low-frequency region R _C and the high frequency region R time difference data acquisition views V _-50 and V _-51 adjacent at the boundary between the _O2 [Delta] w and heart period T. Therefore, the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 can be reduced, and image data with good image quality can be obtained.

Further, by collecting the data of the views V _{26 to} V ₅₁ and V _{−25 to} V ₋₅₀ of the low frequency region _RC with the ordering E, the view V ₂₅ in which the data is collected with the ordering A and the data with the ordering E The time difference in data collection from the view V ₂₆ in which is collected can also be reduced. Therefore, a step difference in signal intensity between the views V ₂₅ and V ₂₆ in which data is collected with different ordering in the low frequency region _RC can be reduced. Similarly, view V- ₂₄ in the low frequency region _RC has data collected in ordering A, while view V- ₂₅ has data collected in ordering E, but these views V- ₂₄ and V- _{24 Since} the time difference in data collection of ₋₂₅ can be reduced, the step difference in signal intensity between the views V ₋₂₄ and V ₋₂₅ can also be reduced. Therefore, the image quality can be further improved.

(3) Third Embodiment In the third embodiment, a method for collecting data of each view according to ordering different from the first and second embodiments will be described. Note that the hardware configuration of the MR apparatus is the same as that of the first embodiment, and thus the description thereof is omitted.

FIG. 23 is an explanatory diagram of ordering when data of each view in the k space is collected in the third mode. The ordering F shows the ordering when collecting the data of the view in the low frequency region _RC , and the ordering G shows the ordering of the view in the high frequency regions R _O1 and R _O2 . The order in which data is collected in each ordering is shown in parentheses.

In the diastole, the view data of the low frequency region _RC is collected according to the ordering F. The ordering F is an ordering (so-called reverse centric ordering) in which positive view data and negative view data are alternately collected in the order close to the high frequency regions R _O1 and R _O2 . First, data of the view V ₅₁ adjacent to the high frequency region R _O1 is collected, and secondly, data of the view V- ₅₀ adjacent to the high frequency region R _O2 is collected. Third, view V ₅₀ data is collected, and fourth, view V- ₄₉ data is collected. Similarly, positive view data and negative view data are alternately collected in order from the views close to the high frequency regions R _O1 and R _O2 .

On the other hand, in the systole, view data of the high frequency regions R _O1 and R _O2 are collected according to the ordering G. The ordering G is ordering (so-called centric ordering) in which positive view data and negative view data are alternately collected in the order close to the low frequency region _RC . First, in the view of the high frequency region R _O1 , data of the view V ₅₂ adjacent to the low frequency region R _C is collected, and secondly, in the view of the high frequency region R _O2 , the low frequency region R _C Data for view V- ₅₁ adjacent to is collected. Third, data of the view V ₅₃ of the high frequency region R _O1 is collected, and fourth, data of the view V- ₅₂ of the high frequency region R _O2 is collected. Similarly, positive view data and negative view data are alternately collected in order from the view close to the low frequency region _RC .

  In the third mode, data of each view in k-space is collected according to ordering F and G while acquiring an electrocardiogram signal (cardiac cycle T). Hereinafter, the order in which the data of each view is collected will be described with reference to FIG.

  FIG. 24 is an explanatory diagram when collecting view data of k-space. FIG. 24 shows a view in which data is collected by the first to tenth sequences SQ.

Since the first and second sequences SQ are executed during the systole, view data in the high frequency region is collected according to the ordering G. Therefore, the data of the view V ₅₂ of the high frequency region R _O1 is collected in the first sequence SQ, and the data of the view V- ₅₁ of the high frequency region R _O2 is collected in the second sequence SQ.

On the other hand, since the third to tenth sequences SQ are executed in the expansion period, the view data of the low frequency region _RC is collected according to the ordering F. Therefore, in the third sequence SQ, data of the view V _{51 in} the low frequency region _RC is collected, and in the fourth sequence SQ, data of the view V- _{50 in} the low frequency region _RC is collected. Similarly, the fifth to tenth sequences SQ are executed in accordance with the ordering F, and data of the views V ₅₀ , V ₋₄₉ , V ₄₉ , V ₋₄₈ , V ₄₈ , and V ₋₄₇ are collected in order. Therefore, the data of the views V _{48 to} V ₅₁ and the views V _{−47 to} V _{50 in} the low frequency region _RC are collected by the third to tenth sequences SQ.

Similarly, it is determined whether it is a diastole or a systole, and if it is determined that it is a systole, the view data of the high frequency region R _O1 or R _O2 is collected according to the ordering G, and if it is determined that it is a diastole, According to ordering F, view data of the low frequency region _RC is collected. Therefore, data for each view in k-space can be collected.

In the third embodiment, in the low frequency region _{R C,} collected in order from the view closer to the high-frequency region _{R O1} and _{R O2,} whereas, in the high frequency region _{R O1} and _{R O2,} collected in order from the view closer to the low-frequency region _{R C} Is done. Therefore, since the time difference Δt of data collection between the adjacent views V ₅₁ and V _{52 at} the boundary portion between the high frequency region R _O1 and the low frequency region _RC can be sufficiently reduced, the time difference Δt is set to the cardiac cycle. T or less. Similarly, it is possible to time difference data acquisition between the views V _-50 and views V _-51 adjacent at the boundary between the high-frequency region R _O2 and the low-frequency region R _C [Delta] w is also sufficiently small, the time difference [Delta] w Can be less than or equal to the cardiac cycle T. Therefore, the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 can be reduced, and image data with good image quality can be obtained.

Note that the number of views which data is collected by the systole, such as by the number of views that data is collected in diastole, but the collection of data for all views in the low frequency region R _C is completed, the high-frequency region R _O1 And R _O2 may have a data uncollected area that includes views for which data has not yet been collected. In this case, not only the systole but also the diastolic phase can be used to collect view data of the high frequency region data uncollected region. Thereby, the data of the view of the data uncollected area can be acquired in a short time.

(4) Fourth Embodiment In the fourth embodiment, a method for collecting data of each view according to ordering different from the first to third embodiments will be described. Note that the hardware configuration of the MR apparatus is the same as that of the first embodiment, and thus the description thereof is omitted.

FIG. 25 is an explanatory diagram of ordering when data of each view in the k space is collected in the fourth mode. The ordering H indicates the ordering when collecting the data of the view in the low frequency region _RC , and the ordering I indicates the ordering of the view in the high frequency regions R _O1 and R _O2 . The order in which data is collected in each ordering is shown in parentheses.

In the diastole, the view data of the low frequency region _RC is collected according to the ordering H. The ordering H is ordering for collecting data of each view from the view V- ₅₀ adjacent to the high frequency region R _O2 toward the view V ₅₁ adjacent to the high frequency region R _O1 .

On the other hand, in the systole, view data of the high frequency regions R _O1 and R _O2 are collected according to the ordering I. Ordering I from the view _{V -51} of the high-frequency region _{R O2,} collects data of each view towards the view _{V -127,} After collecting data in the view _{V -127,} from the view _{V 128} of the high-frequency region _{R O1} low This is ordering for collecting data of each view toward the frequency domain _RC .

In FIG. 25, the collection of data for all the views in the low frequency region _RC has been completed first, but in the high frequency region _RO1 , there are views for which data has not yet been collected. In the fourth embodiment, in the high frequency region R _O1, there is a data uncollected region a where data is not collected. In the fourth mode, the data uncollected area a includes views V _{52 to} V ₁₁₅ . Data of these views is collected by ordering J different from ordering I. The ordering J will be specifically described below.

In ordering J, the following steps S1 and S2 are executed.

(Step S1) The data of the view closest to the low frequency region _RC among the views included in the data uncollected region a is collected.
(Step S2) The data of the view farthest from the low frequency region _RC among the views included in the data uncollected region a is collected.

Referring to FIG. 25, the data non-collection area a includes views V _{52 to} V ₁₁₅ in which data is not collected. Among the views V _{52 to} V ₁₁₅ for which data is not collected, the view closest to the low frequency region _RC is the view V ₅₂ , and the view farthest from the low frequency region _RC is the view V ₁₁₅ . Therefore, in step S1, data of the view V ₅₂ is collected, and in step S2, data of the view V ₁₁₅ is collected. FIG. 26 shows views V ₅₂ and V ₁₁₅ from which data was collected.

By executing steps S1 and S2, data is collected in the order of the views V ₅₂ and V ₁₁₅ . Referring to FIG. 26, in the high frequency region R _O1 , there is still a data uncollected region where data is not collected. In this case, ordering J executes steps S1 and S2 again.

The data uncollected area a, which contains the view _V 53 _{~V 114} that data has not been collected. Among the views V _{53 to} V ₁₁₄ for which data is not collected, the view closest to the low frequency region _RC is the view V ₅₃ , and the view farthest from the low frequency region _RC is the view V ₁₁₄ . Therefore, in step S1, data of the view V ₅₃ is collected, and in step S2, data of the view V ₁₁₄ is collected. FIG. 27 shows views V ₅₃ and V ₁₁₄ from which data was collected.

When the data of the views V ₅₃ and V ₁₁₄ are collected, the steps S1 and S2 are repeatedly executed until the data of the views V _{54 to} V ₁₁₃ included in the data uncollected area a are collected. .

  In the above example, steps S1 and S2 are executed in the order of steps S1 and S2. However, as long as steps S1 and S2 are executed, the order is not limited to steps S1 and S2, and may be the order of steps S2 and S1.

  In the fourth embodiment, data of each view in k space is collected according to ordering H, I, and J while acquiring an electrocardiogram signal (cardiac cycle T). Hereinafter, the order in which the data of each view is collected will be described with reference to FIG.

  FIG. 28 is an explanatory diagram when collecting k-space view data. FIG. 28 shows a view in which data is collected by the first to seventh sequence SQ.

Since the first to third sequence SQ is executed in the systole, view data in the high frequency region is collected according to the ordering I. In Figure 28, view _V -51 of the high-frequency region _{R O2,} V _-52, data _{V -53} are collected in the first to 3 th sequence SQ. Further, since the fourth to seventh sequence SQ is executed in the expansion period, view data of the low frequency region _RC is collected. Here, in the fourth to seventh sequences SQ, data of the views V- ₅₀ , V- ₄₉ , V- ₄₈ , and V- _{47 in} the low frequency region _RC are collected.

Similarly, it is determined whether it is a diastole or a systole, and when it is determined that it is a systole, the view data of the high frequency region R _O1 or R _O2 is collected according to ordering I, and when it is determined that it is a diastole, According to the ordering H, view data of the low frequency region _RC is collected. Therefore, each time the sequence SQ is executed, data is sequentially arranged in each view of the k space.

  FIG. 29 is a diagram illustrating a view in which data is collected by the sequence SQ of the p−4th to pth times.

Since the p-4th sequence SQ is executed in the systole, view data in the high frequency region is collected according to the ordering I. Here, in the sequence SQ of the (p−4) th time, data of the view V _{116 in} the high frequency region R _O1 is collected.

In addition, since the p-3th to pth sequence SQ is executed in the expansion period, view data in the high frequency region is collected. In FIG. 29, the data of the views V ₄₈ , V ₄₉ , V ₅₀ , and V ₅₁ in the low frequency region _RC are collected in the p-3th to pth sequence SQ. When the p-th sequence SQ is completed, data collection for all views in the low-frequency region _RC is completed.

  Next, data collected by the (p + 1) th and subsequent sequences SQ will be described.

Referring to FIG. 29, all view data are collected in the low frequency region _RC . However, in the high-frequency region R _O1, there is a data uncollected region a where data has not yet been collected. The data uncollected area a, which contains the view _V 52 _{~V 115.} Therefore, the sequence SQ after the (p + 1) th time is executed in order to collect the data of these views V _{52 to} V ₁₁₅ . Data of these views V _{52 to} V ₁₁₅ are collected according to ordering J (see FIGS. 26 and 27).

  In ordering J, as described above, data is collected according to steps S1 and S2.

  In the fourth mode, ordering J is started from the (p + 1) th sequence SQ. Therefore, when the p + 1 and p + 2 times of the sequence SQ are executed, data is collected according to steps S1 and S2.

In p + 1 th sequence SQ, according to step S1, in a view _V 52 _{~V 115} included in the data non-acquisition region a, it collects data closest view _{V 52} in the low frequency region _{R C.}
In the sequence SQ of the (p + 2) th time, the data of the view V ₁₁₅ farthest from the low frequency region _RC among the views V _{52 to} V ₁₁₅ included in the data uncollected region a is collected according to step S2.

FIG. 30 shows views V ₅₂ and V ₁₁₅ in which data is collected by the (p + 1) th and p + 2th sequence SQ. Note that the high frequency region R _O1 still includes views V _{53 to} V ₁₁₄ for which data has not been collected. Therefore, the p + 3 and subsequent sequence SQ, until the data of the remaining views _V 53 _{~V 114} of the high-frequency region _{R O1} is collected, steps S1 and S2 are repeated. In this way, data for all views in k-space are collected.

In a fourth form, the view data for the low frequency region _RC is collected according to ordering H, while the view data for the high frequency regions R _O1 and R _O2 are collected according to ordering I. Therefore, in the low frequency region R _C, data of the view V _-50 is first collected in the high frequency region, the data of the view V _-51 is first collected. Thereby, the time difference Δt (see FIG. 28) of data collection between the adjacent views V- ₅₀ and V- ₅₁ at the boundary portion between the high frequency region _R02 and the low frequency region _RC can be made equal to or less than the cardiac cycle T.

In the fourth embodiment, the view data in the high frequency region is initially collected according to the ordering I, but after all the view data in the low frequency region _RC is collected, the ordering I changes to the ordering J. Switch. Accordingly, since the data of the view V ₅₂ of the high frequency region _RC is collected within a short time after the data of the view V ₅₁ of the low frequency region _RC is collected, the adjacent views V ₅₁ and V ₅₂ The data collection time difference Δw (see FIG. 30) can be made equal to or less than the cardiac cycle T. Therefore, the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 can be reduced, and image data with good image quality can be obtained.

Further, by collecting data of the views V _{52 to} V _{115 in} the high frequency region R _O1 by the ordering J, the view V ₁₁₆ in which the data is collected in the ordering I and the view V ₁₁₅ in which the data is collected in the ordering J The time difference in data collection can also be reduced. Therefore, the step difference in signal intensity between the views V ₁₁₅ and V ₁₁₆ in which data is collected with different ordering in the high frequency region R _O1 can be reduced, and the image quality can be further improved.

(5) Fifth Mode In the fourth mode, an example in which data for all views in the low frequency region R _C is collected first before data for all views in the high frequency regions R _O1 and R _O2 is collected. Explained. In the fifth embodiment, ordering will be described in a case where data of all views in the high frequency regions R _O1 and R _O2 is first collected before data of all views in the low frequency region _RC is collected. The hardware configuration of the MR apparatus is the same as that in the first embodiment.

FIG. 31 is an explanatory diagram of ordering when data of each view in the k space is collected in the fifth embodiment. The ordering H indicates the ordering when collecting the data of the view in the low frequency region _RC , and the ordering I indicates the ordering of the view in the high frequency regions R _O1 and R _O2 . The order in which data is collected in each ordering is shown in parentheses.

In the diastole, the view data of the low frequency region _RC is collected according to the ordering H. The ordering H is an ordering that collects data of each view from the view V- ₅₀ adjacent to the high frequency region R _O2 toward the high frequency region R _O1 as in the fourth embodiment.

On the other hand, in the systole, view data of the high frequency regions R _O1 and R _O2 are collected according to the ordering I. Ordering I, like the fourth embodiment, when the view _{V -51} of the high-frequency region _{R O2,} collects data of each view towards the view _{V -127,} collects data in the view _{V -127,} a high frequency region This is ordering for collecting data of each view from the view V _{128 of} R _O1 toward the low frequency region _RC .

In FIG. 31, data collection for all views in the high frequency regions R _O1 and R _O2 has been completed first, but in the low frequency region _RC , there is a data uncollected region b for which data has not yet been collected. ing. In the fifth mode, the data uncollected area b includes views V _{1 to} V ₅₁ . Data of these views is collected by ordering K different from ordering H. The ordering K will be specifically described below.

In ordering K, the following steps S1 and S2 are executed.

(Step S1) Among the views included in the data uncollected area b, data of the view closest to the high frequency area R _O1 is collected.
(Step S2) Among the views included in the data uncollected region b, data of a view farthest from the high frequency region _R01 is collected.

Referring to FIG. 31, the data non-collection area b includes views V _{1 to} V _{51 in} which no data is collected. Among the views V _{1 to} V ₅₁ for which data is not collected, the view closest to the high frequency region R _O1 is the view V ₅₁ , and the view farthest from the high frequency region R _O1 is the view V ₁ . Therefore, in step S1, data of the view V ₅₁ is collected, and in step S2, data of the view V ₁ is collected. FIG. 32 shows views V ₅₁ and V ₁ from which data was collected.

By executing steps S1 and S2, data is collected in the order of the views V ₅₁ and V ₁ . Referring to FIG. 32, in the low frequency region _RC , there is still a data uncollected region b where data is not collected. In this case, ordering K executes steps S1 and S2 again.

The data non-collection area b includes views V _{2 to} V _{50 in} which no data is collected. Of the views V _{2 to} V ₅₀ for which data is not collected, the view closest to the high frequency region R _O1 is the view V ₅₀ , and the view farthest from the high frequency region R _O1 is the view V ₂ . Accordingly, in step S1, data of the view V ₅₀ is collected, and in step S2, data of the view V ₂ is collected. FIG. 33 shows the views V ₅₀ and V ₂ from which data was collected.

When the data of the views V ₅₀ and V ₂ are collected, the steps S1 and S2 are repeatedly executed until the data of the views V _{3 to} V ₄₉ included in the data uncollected area b are collected in the same manner. .

  In the above example, steps S1 and S2 are executed in the order of steps S1 and S2. However, as long as steps S1 and S2 are executed, the order is not limited to steps S1 and S2, and may be the order of steps S2 and S1.

  In the fifth embodiment, data of each view in k space is collected according to ordering H, I, and K while acquiring an electrocardiogram signal (cardiac cycle T). Hereinafter, the order in which the data of each view is collected will be described with reference to FIG.

  FIG. 34 is an explanatory diagram when collecting view data of the k space. FIG. 34 shows a view in which data is collected by the first to sixth sequence SQ.

Since the first to third sequence SQ is executed in the systole, view data in the high frequency region is collected according to the ordering I. In Figure 34, view _V -51 of the high-frequency region _{R O2,} V _-52, data _{V -53} are collected in the first to 3 th sequence SQ. Further, since the fourth to sixth sequences SQ are executed in the expansion period, view data in the low frequency region _RC is collected. Here, in the fourth to sixth sequences SQ, data of the views V- ₅₀ , V- ₄₉ , and V- _{48 in} the low frequency region _RC are collected.

Similarly, it is determined whether it is a diastole or a systole, and when it is determined that it is a systole, the view data of the high frequency region R _O1 or R _O2 is collected according to ordering I, and when it is determined that it is a diastole, According to the ordering H, view data of the low frequency region _RC is collected. Therefore, each time the sequence SQ is executed, data is sequentially arranged in each view of the k space.

  FIG. 35 is a diagram illustrating a view in which data is collected by the sequence SQ of the q-7th to qth times.

Since the q-7th sequence SQ is executed in the expansion period, the view data of the low frequency region _RC is collected according to the ordering H. Here, in the sequence SQ of the q-7th time, data of the view V _{0 in} the low frequency region _RC is collected.

Further, since the q-6th to qth sequences SQ are executed in the systole, data of the view in the high frequency region is collected. In FIG. 35, the data of the views V ₅₈ , V ₅₇ , V ₅₆ , V ₅₅ , V ₅₄ , V ₅₃ , and V ₅₂ in the high frequency region R _O1 are collected in the q−6th to qth sequence SQ. When the q-th sequence SQ is completed, data collection for all views in the high-frequency regions R _O1 and R _O2 is completed.

Next, data collected by the sequence SQ after the q + 1th time will be described.
Referring to FIG. 35, all the view data are collected in the high-frequency regions R _O1 and R _O2 . However, in the low frequency region _RC, there is a data uncollected region b where data has not yet been collected. The data uncollected area b includes views V _{1 to} V ₅₁ . Therefore, the sequence SQ after the (q + 1) th time is executed to collect data of these views V _{1 to} V ₅₁ . Data of these views V _{1 to} V ₅₁ are collected according to ordering K (see FIGS. 32 and 33).

  In ordering K, as described above, data is collected according to steps S1 and S2.

  In the fifth embodiment, ordering K is started from the (q + 1) th sequence SQ. Therefore, data is collected according to steps S1 and S2 when the sequence SQ of q + 1 time and q + 2 time is executed.

In the (q + 1) -th sequence SQ, data of the view V ₅₁ closest to the high-frequency region R _O1 is collected among the views V _{1 to} V ₅₁ included in the data uncollected region b according to step S1.
In q + 2 th sequence SQ, according to step S2, in a view _V 1 _{~V 51} included in the data non-acquisition region b, collects most distant view _{V 1} data from the high-frequency region _{R O1.}

FIG. 36 shows views V ₅₁ and V ₁ in which data is collected by the sequence SQ of the q + 1th time and the q + 2th time. Note that the low frequency region R _O1 still includes views V _{2 to} V ₅₀ for which data has not been collected. Therefore, in the sequence SQ after q + 3, steps S1 and S2 are repeatedly executed until data of the remaining views V _{2 to} V _{50 in} the low frequency region _RC is collected. In this way, data for all views in k-space are collected.

In the fifth form, view data for the low frequency region _RC is collected according to ordering H, while view data for the high frequency regions R _O1 and R _O2 are collected according to ordering I. Therefore, as in the fourth embodiment, the time difference Δt (see FIG. 34) of data collection between the views V- ₅₀ and V- ₅₁ adjacent to each other at the boundary portion between the high frequency region R _O1 and the low frequency region _RC is represented by the cardiac cycle T. It can be:

In the fifth mode, the view data in the low frequency region is initially collected according to the ordering H. However, after the data of all the views in the high frequency regions R _O1 and R _O2 are collected, the data from the ordering H is collected. Switch to ordering K. Therefore, since the data of the view V ₅₁ of the low frequency region _RC is collected within a short time after the data of the view V ₅₂ of the high frequency region R _O1 is collected, the adjacent views V ₅₁ and V ₅₂ The data collection time difference Δw (see FIG. 36) can be made equal to or less than the cardiac cycle T. Therefore, the step difference in signal intensity at the boundary between the low frequency region _RC and the high frequency regions R _O1 and R _O2 can be reduced, and image data with good image quality can be obtained.

  In the first to fifth embodiments, scanning is performed while acquiring an electrocardiogram signal. However, instead of the electrocardiogram signal, another signal (for example, a pulse wave signal) from which information on the cardiac cycle can be obtained may be acquired and scanned.

  In the first to fifth embodiments, examples in which imaging is performed with the subject 14 holding his / her breath are described. However, the present invention can also be applied to the case where imaging is performed with the subject 14 breathing freely. It should be noted that, under free breathing, the liver undergoes body motion due to heartbeat and body motion due to respiration, but generally it is considered that body motion due to respiration is greater than body motion due to heartbeat. Therefore, when imaging is performed under free breathing, the respiration signal of the subject 14 is acquired, and ordering may be executed so that the time differences Δt and Δw are equal to or less than one cycle of the respiration signal. By executing the ordering so that the time differences Δt and Δw are equal to or less than one cycle of the respiratory signal, the information entropy can be reduced, so that the image quality can be improved. When collecting the data of each view while acquiring the breathing signal, for example, during the period when the subject 14 exhales, the view data of the low frequency region is collected and the subject 14 breathes. What is necessary is just to collect the view data of a high frequency area | region in the period when it inhaled.

  Moreover, although the case where the liver is image | photographed is demonstrated in the 1st-5th form, it is not limited to a liver, If the site | part which moves by breathing or a heartbeat is image | photographed, for example, a kidney It can also be applied when shooting. In the present invention, when imaging a body moving part due to breathing or heartbeat, the time difference of data collection of adjacent views at the boundary between the high frequency region and the low frequency region is calculated as a biological signal such as a respiratory signal or an electrocardiogram signal. The image quality can be improved by executing the ordering so as to be equal to or less than one cycle.

  In the first to fifth embodiments, the case where the k space is two-dimensional (kx axis and ky axis) has been described. However, the present invention describes that the k space is three dimensional (kx axis, ky axis, and kz). It can also be applied to the case of an axis. Even when the k-space is three-dimensional, ordering is performed so that the time difference in data collection between adjacent views at the boundary between the high-frequency region and the low-frequency region is less than one cycle of a biological signal such as a respiratory signal or an electrocardiogram signal. By doing so, the image quality can be improved.

2 Magnet 3 Table 3a Cradle 4 Contrast medium injector 5 Reception coil 6 Sensor 7 Sequencer 8 Transmitter 9 Gradient magnetic field power supply 10 Receiver 11 Control unit 11a Judgment unit 11b View setting unit 12 Operation unit 13 Display unit 14 Subject 21 Bore 22 Superconducting coil 23 Gradient coil 24 Transmitting coil 100 MR device

Claims (14)

A determination means for determining a body movement state of the subject based on an electrocardiogram signal or a pulse wave signal of the subject;
Collecting view data in a low-frequency region of k-space when the subject is in a first body motion state, and a first high-frequency region in k-space when the subject is in a second body motion state; Scanning means for collecting view data in a second high frequency region;
A magnetic resonance apparatus comprising:
The first high frequency region has a first view adjacent to the low frequency region;
The second high frequency region has a second view adjacent to the low frequency region;
The low frequency region has a third view adjacent to the first view and a fourth view adjacent to the second view;
The scanning means includes
The data collection time difference Δt between the first view and the third view and the data collection time difference Δw between the second view and the fourth view satisfy the following conditions: A magnetic resonance apparatus that performs scanning.

Δt ≦ T
Δw ≦ T
Where T: period of the electrocardiogram signal or pulse wave signal
The scanning means includes
When collecting the view data of the low frequency region, after collecting the central view of k-space, the positive view data and the negative view data are alternately collected in the order close to the central view. Collect data according to the ordering
When collecting view data of the first high-frequency region and the second high-frequency region, according to a second ordering that alternately collects positive view data and negative view data in order from the low frequency region. Collect data,
When the data of all the views in the low frequency region are collected, if the data of the first view and the second view are not collected, the first order is satisfied according to the third ordering that satisfies the condition. The magnetic resonance apparatus of claim 1, wherein data for the second view and the second view are collected. The first high frequency region has a first data uncollected region where data is not collected at the time when data of all views of the low frequency region is collected,
The second high frequency region has a second data uncollected region where data is not collected at the time when data of all views of the low frequency region is collected,
The scanning means includes
The magnetic resonance apparatus according to claim 2, wherein in the third ordering, data is collected by repeating the following steps S1 to S4.

(Step S1) Of the views included in the first data uncollected area, the data of the view closest to the low frequency area is collected.
(Step S2) Among the views included in the first data uncollected area, data of a view farthest from the low frequency area is collected.
(Step S3) Among the views included in the second data uncollected area, the data of the view closest to the low frequency area is collected.
(Step S4) Of the views included in the second data uncollected area, the data of the view farthest from the low frequency area is collected.   In the third ordering, the view data in the first high-frequency region and the second high-frequency region are obtained not only in the second body movement state but also in the first body movement state. The magnetic resonance apparatus according to claim 2, which is collected. The scanning means includes
When collecting the view data of the low frequency region, after collecting the central view of k-space, the positive view data and the negative view data are alternately collected in the order close to the central view. Collect data according to the ordering
When collecting view data of the first high-frequency region and the second high-frequency region, according to a second ordering that alternately collects positive view data and negative view data in order from the low frequency region. Collect data,
When the data of the third view and the fourth view of the low frequency region are not collected when the data of all the views of the first high frequency region and the second high frequency region are collected. The magnetic resonance apparatus according to claim 1, wherein data of the third view and the fourth view are collected according to a third ordering that satisfies the condition. The low- frequency region includes a first data uncollected region in which data is not collected and data collected when all view data of the first high-frequency region and the second high-frequency region are collected. A second data uncollected area that has not been
The scanning means includes
6. The magnetic resonance apparatus according to claim 5, wherein in the third ordering, data is collected by repeating the following steps S1 to S4.

(Step S1) Of the views included in the first data uncollected area, the data of the view closest to the first high frequency area is collected.
(Step S2) Among the views included in the first data uncollected area, data of a view farthest from the first high frequency area is collected.
(Step S3) Of the views included in the second data uncollected area, the data of the view closest to the second high frequency area is collected.
(Step S4) Among the views included in the second data uncollected area, data of a view farthest from the second high frequency area is collected. The scanning means includes
When collecting view data in the low frequency region, first ordering that alternately collects positive view data and negative view data in the order closer to the first high frequency region and the second high frequency region. Collect data according to
When collecting the view data of the first high frequency region and the second high frequency region, according to the second ordering in which the positive view data and the negative view data are alternately collected in the order close to the low frequency region. The magnetic resonance apparatus according to claim 1, wherein data is collected.   When data of all views in the low frequency region is collected, if the view in which no data is collected is included in the first high frequency region and the second high frequency region, the first The view data in the first high-frequency region and the second high-frequency region are collected not only in the second body motion state but also in the first body motion state. Magnetic resonance device. The scanning means includes
When collecting view data of the low frequency region, collecting data according to a first ordering from the first high frequency region to the second high frequency region;
When collecting view data of the first high-frequency region and the second high-frequency region, the view data of the first high-frequency region is collected in order from the low-frequency region, and then from the low-frequency region, Collecting data according to a second ordering that collects data of the second high frequency region view in order of distance;
When the data of all the views in the low frequency region are collected, if the data of the second view is not collected, the data of the second view is collected according to the third ordering that satisfies the condition. The magnetic resonance apparatus according to claim 1. The second high-frequency region has a data uncollected region where data is not collected at the time when data of all views of the low-frequency region is collected,
The scanning means includes
The magnetic resonance apparatus according to claim 9, wherein in the third ordering, data is collected by repeating the following steps S1 and S2.

(Step S1) Of the views included in the data uncollected area, the data of the view closest to the low frequency area is collected.
(Step S2) Among the views included in the data uncollected area, data of a view farthest from the low frequency area is collected.   In the third ordering, the view data in the first high-frequency region and the second high-frequency region are obtained not only in the second body movement state but also in the first body movement state. The magnetic resonance apparatus according to claim 9 or 10, which collects the magnetic resonance apparatus. The scanning means includes
When collecting view data of the low frequency region, collecting data according to a first ordering from the first high frequency region to the second high frequency region;
When collecting view data of the first high-frequency region and the second high-frequency region, the view data of the first high-frequency region is collected in order from the low-frequency region, and then from the low-frequency region, Collecting data according to a second ordering that collects data of the second high frequency region view in order of distance;
When the data of the fourth view is not collected at the time when the data of all the views of the first high-frequency region and the second high-frequency region are collected, according to the third ordering that satisfies the condition, The magnetic resonance apparatus according to claim 1, wherein data of the fourth view is collected. The low frequency region has a data uncollected region in which data is not collected when data of all views of the first high frequency region and the second high frequency region are collected,
The scanning means includes
The magnetic resonance apparatus according to claim 12, wherein in the third ordering, data is collected by repeating the following steps S1 and S2.

(Step S1) Of the views included in the data uncollected area, the data of the view closest to the second high frequency area is collected.
(Step S2) Of the views included in the data uncollected area, the data of the view farthest from the second high frequency area is collected. Said first body movement state is a state when the heart diastole, the second body motion state is the state when the heart systole any one of claims 1 to 13 The magnetic resonance apparatus described in 1.