Magnetic resonance imaging apparatus and imaging position determining method

Abstract

To provide a technique for automatically setting an imaging position with consideration given to a respiratory motion of a subject, thereby reducing a user's burden and enabling robust imaging against variation of an organ position.SOLUTION: Using a scout image acquired over at least one cycle of a periodic motion of the subject, an imaging position for a main imaging is determined according to imaging conditions. At this time, a predetermined tissue is extracted from the scout image, and multiple imaging ranges are calculated, including a minimum imaging range that embraces the tissue and a maximum imaging range that embraces a range where the tissue is displaced within the cycle of the periodic motion. Then, according to the imaging conditions, any of the imaging ranges is determined as the imaging position. When the periodic motion is a respiratory motion, the imaging conditions include a breathing method designated by the user, and the imaging range is selected based on thus designated breathing method, and the imaging position (slice position) is automatically set.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a magnetic resonance imaging (MRI) device that measures nuclear magnetic resonance (hereinafter referred to as "NMR") signals from hydrogen, phosphorus, etc. in a subject and images the nuclear density distribution, relaxation time distribution, etc., and in particular to a technique for determining the position at which to image the subject. [Background technology]

[0002] In MRI examinations, anatomical cross sections are typically captured for each examination site, but the patient's body shape and posture vary from examination to examination. For this reason, even when performing the same imaging sequence or analysis, it is necessary to adjust the patient's imaging position for each examination.

[0003] Furthermore, because there are individual differences among subjects, the above operations may vary depending on the skill of the operator. The abdomen in particular is a region where there is significant individual variability among subjects, and in the case of breath-holding imaging, the position of organs also varies depending on the respiratory phase, making it difficult to set the imaging position for the subject. Furthermore, there is a trend to reduce breath-holding imaging in order to reduce the burden on the subject, but in this case, the position of organs also varies due to breathing, making it even more difficult to set the imaging position for the subject that takes breathing into consideration, and there is also greater variability among operators.

[0004] In an MRI examination, in addition to the setting of the imaging position as described above, it is necessary to adjust the imaging parameters to suit the purpose of the examination. Therefore, if the imaging position is not set appropriately, and the setting position is incorrect or the range is insufficient, resulting in the occurrence of artifacts, the imaging must be retaken, which increases the burden on the user.

[0005] As a technology for reducing the burden on a user in setting an imaging position, for example, Patent Document 1 discloses a technology for automatically detecting and setting an imaging position by tracking the edges of an organ based on an edge-enhanced image of the liver. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5660807 specification Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 only automatically calculates organ positions from captured images and does not take into account changes in organ positions due to the subject's breathing. Therefore, the technology described in Patent Document 1 may cause a discrepancy between the image used to detect the imaging position and the actual breath-hold imaging position, making it impossible to avoid imaging failures due to such changes in the subject's organ positions. In addition, breath-hold imaging is required to suppress respiratory movement during imaging, which places a heavy burden on the subject.

[0008] An object of the present invention is to provide a technology for automatically setting an imaging position that takes into account the respiratory movement of a subject, thereby reducing the burden on the user and enabling imaging that is robust against changes in organ position. [Means for solving the problem]

[0009] To solve the above problem, slice positions are automatically set based on a predetermined scout scan, taking respiratory motion into consideration.

[0010] That is, the MRI apparatus of the present invention includes an imaging unit that acquires an image of a subject based on nuclear magnetic resonance, and an imaging position determination unit that calculates an imaging range of the subject and determines an imaging position. The imaging position determination unit calculates multiple imaging ranges, including a minimum imaging range that includes a predetermined tissue and a maximum imaging range that includes a range in which the tissue displaces within a cycle of periodic motion, using images acquired by the imaging unit through a scout scan, and determines one of the multiple imaging ranges as the imaging position for the main scan depending on imaging conditions.

[0011] The imaging position determination method of the present invention determines the imaging position for main imaging according to imaging conditions using a scout image acquired over at least one period of the subject's periodic motion. At this time, a predetermined tissue is extracted from the scout image, and multiple imaging ranges are calculated, including a minimum imaging range that includes the tissue and a maximum imaging range that includes the range in which the tissue moves within the period of the periodic motion. One of the multiple imaging ranges is determined as the imaging position according to the imaging conditions.

[0012] When the periodic movement is respiratory movement, the imaging conditions include a breathing method designated by the user, and the imaging range is selected based on the designated breathing method, and the imaging position (slice position) is automatically set. [Effects of the Invention]

[0013] According to the present invention, the imaging position (slice position) is automatically set based on the subject's body type, the positions and ranges of the organs, and the phase of periodic movement (respiratory phase), thereby reducing the burden of manual operation on the user, reducing variations due to differences in operator skill, and further preventing imaging failures and reducing the burden on the subject.

[0014] Furthermore, by selecting the breathing method during imaging as an imaging condition, the user can automatically set the optimal position and range for the selected breathing method. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing an overall outline of an MRI apparatus to which the present invention is applied. [Figure 2] FIG. 1 is a diagram showing the flow of an examination using the MRI apparatus of the present invention. [Figure 3] Functional block diagram of an imaging position determination unit according to the first embodiment. [Figure 4] Flow showing the process of determining the imaging position according to the first embodiment [Figure 5] A diagram showing an example of a GUI for specifying a breathing method. [Figure 6] A flow chart showing the details of the process in Figure 4 [Figure 7] FIG. 1 is a diagram illustrating an example of a position detection method. [Figure 8] A flow chart showing details of the process S43 in FIG. 4 [Figure 9] A diagram explaining estimation of respiratory phase [Figure 10] FIG. 1 is a diagram illustrating how multiple imaging ranges are determined. [Figure 11] Functional block diagram of a computer according to a second embodiment [Figure 12] Flow showing parameter adjustment after imaging position determination in embodiment 2 [Figure 13] An example of a GUI that presents options for parameter adjustment. [Figure 14] Flow showing the process when a user selects an option DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described. In all the drawings for explaining the embodiment of the present invention, the same reference numerals are used to designate parts having the same functions, and repeated description thereof will be omitted. The MRI apparatus of this embodiment includes an imaging unit that acquires an image of a subject based on nuclear magnetic resonance, an imaging position determination unit that calculates the imaging range of the subject and determines the imaging position, and a measurement control unit that controls the imaging unit to perform a scout scan including acquiring a moving image of one or more cycles of the periodic motion of the subject.

[0017] The configuration of a typical MRI apparatus to which this embodiment is applied is shown in FIG. 1. As shown in the figure, the MRI apparatus includes an imaging unit 100 including a magnet 102 that generates a static magnetic field in a space (examination space) in which a subject 101 is placed, a gradient coil 103 that generates a gradient magnetic field in the examination space, an RF coil 104 that generates a high-frequency magnetic field in a predetermined region of the subject 101, and an RF probe 105 that detects MR signals generated by the subject 101, and a computer 200 that controls the imaging unit 100 and performs various calculations required for imaging. The computer 200 includes functions such as a measurement control unit 210 that controls the imaging unit 100, a calculation unit 220 that performs calculations such as image creation, and an imaging position determination unit 230 that performs various calculations related to imaging position determination. The computer 200 is also connected to a UI unit 300 that includes a display device 301 and an input device 302 for interfacing with a user. The MRI apparatus further includes a bed 112 for placing the subject in the examination space.

[0018] The gradient magnetic field coil 103 is composed of gradient magnetic field coils in three directions, X, Y, and Z, and generates each gradient magnetic field in response to a signal from a gradient magnetic field power supply 109. The RF coil 104 generates a high frequency magnetic field in response to a signal from an RF transmitter 110. A signal from the RF probe 105 is detected by a signal detector 106, processed by a signal processor 107, and converted into an image signal by calculation.

[0019] The gradient magnetic field power supply 109, RF transmitter 110, and signal detector 106 perform imaging according to a time chart called a pulse sequence. During imaging, a high-frequency magnetic field is applied to induce nuclear magnetic resonance in the nuclei of atoms constituting the tissue of the subject, and a nuclear magnetic resonance signal (echo signal) emitted from the subject in response is detected. By applying an appropriate combination of gradient magnetic fields in various directions, different phase encodings are imparted to the echo signals, and the signal detector 106 collects the echo signals obtained by each phase encoding. The number of phase encodings is typically selected to be 128, 256, 512, or the like per image. Each echo signal is typically obtained as a time-series signal consisting of 128, 256, 512, or 1024 sampling data. The computer 200 performs a two-dimensional Fourier transform on this data to create an MR image, which is then displayed on the display device 301.

[0020] The computer 200 includes a memory, a CPU, and a GPU, and the functions of the measurement control unit 210, the calculation unit (image generation / image processing) 220, and the imaging position determination unit 230 are executed by uploading programs that realize those functions to the CPU, etc. However, some of the functions realized by the computer 200 may also be realized in programmable ICs such as ASICs and FPGAs, and these are also treated as part of the computer 200 in the present invention.

[0021] Next, we will explain the flow of an examination, including setting the imaging position in the MRI apparatus configured as described above. Figure 2 shows a flowchart of control by the measurement control unit 210. First, examination information is registered (S21), and a scout image is captured (S22). The examination information includes information about the subject, the examination area (target disease), and the examination protocol (imaging type, sequence, etc.), and may be entered by the user via a user interface or may be read from information stored in advance on a recording medium, etc. Scout images are relatively low-resolution images that cover a wide range of the subject and are used to determine the imaging position. Scout images include 2D images and moving images acquired over at least one cycle of the subject's periodic motion. Here, 2D images are referred to as 2D scout images to distinguish them from moving images.

[0022] The imaging position determination unit 230 automatically calculates the imaging range using the scout image (S23), and performs positioning (imaging range adjustment) on the scout image (S24). The automatic calculation of the imaging range and its adjustment will be described in detail in the embodiments described later. Following the imaging range adjustment, parameters are adjusted manually or within the system as needed (S25), and a main scan for examination is executed (S26). The parameter adjustment (S25) mainly involves imaging parameters that determine the pulse sequence, i.e., slice thickness, number of slices, matrix size, repetition time TR, etc., and is executed when adjustment is necessary following the adjustment of the imaging range.

[0023] The MRI apparatus of this embodiment is characterized in that the imaging position determination unit 230 uses the scout image acquired by the imaging unit 100 to calculate multiple imaging ranges including a minimum imaging range that includes a predetermined tissue and a maximum imaging range that includes a range in which the tissue displaces within a cycle of periodic motion, and determines one of the multiple imaging ranges as the imaging position for main imaging depending on the imaging conditions.

[0024] A specific embodiment of the processing of the imaging position determination unit 230 will be described below.

[0025] <Embodiment 1> In this embodiment, the processing of the imaging position setting unit 230 will be described by taking as an example a case where an imaging position is set to a region where respiratory movement (movement caused by breathing) occurs. The region where respiratory movement occurs is mainly the abdomen, and the description will be given here by taking as an example a case where the imaging region is the abdomen.

[0026] In this embodiment, 2D scout images and moving images are used to set an appropriate imaging position for the region where respiratory movement occurs according to the imaging conditions. The position and positional fluctuation of the imaging target are estimated from these images, and multiple imaging ranges are calculated using these estimation results. Furthermore, based on the calculated imaging ranges, the imaging range or navigator echo acquisition position according to the imaging technique related to respiratory movement desired by the user is determined.

[0027] To achieve this function, the imaging position determination unit 230 of this embodiment includes: a tissue extraction unit that extracts an organ to be imaged by using an image acquired by a scout scan; a phase calculation unit that calculates the phase of the subject's periodic motion by using a moving image; and an imaging range calculation unit that calculates multiple imaging ranges including a minimum imaging range and a maximum imaging range by using the organ position extracted by the tissue extraction unit and the periodic motion phase calculated by the phase calculation unit, and determines one of the multiple imaging ranges as the imaging position for the main scan depending on the imaging conditions.

[0028] 3 shows an example of a functional block diagram of the imaging position determination unit 230. As shown in the figure, the imaging position determination unit 230 includes a preprocessing unit 231 that performs filtering on an image, a tissue extraction unit 233 that extracts a desired imaging region from the preprocessed image, an imaging range calculation unit 235 that calculates an imaging range from the extracted imaging region, a respiratory phase calculation unit 237 that calculates a respiratory phase based on the imaging region for each time phase extracted from the moving image, and a navigator position determination unit 239.

[0029] Next, the flow of processing by the imaging position determination unit 230 will be described with reference to the flow in Fig. 4. Note that the flow in Fig. 2 will be referenced as necessary.

[0030] First, when registering examination information (FIG. 2: S21), a specification 20 of the subject's breathing method is accepted as one of the imaging conditions via the UI unit 300 (S41) (FIG. 2: S27). The breathing method is either breath-holding or natural breathing, and is determined by the user in consideration of the subject's condition, imaging technique, etc. The imaging method corresponding to the subject's breathing method is determined by the specification of the subject's breathing method. FIG. 5 shows an example of a screen displayed on the display device 301 for accepting specification of the subject's breathing method. In the example shown, a selection is made between breath-hold imaging and respiratory-gated imaging (natural breathing), and in the case of breath-hold imaging, a selection is made between breath-holding during inspiration or breath-holding during expiration.

[0031] The imaging position determination unit 230 inputs the scout image acquired by the imaging unit 100, the moving images captured continuously at high speed, and the examination information, along with the breathing method specified by the user, and using these, the system can automatically calculate the imaging range that includes the imaging target area without excess or deficiency, in accordance with the breathing method specified by the user (S42 to S44).

[0032] The automatic calculation process is roughly divided into processing for a 2D scout image (S42), processing for a moving image (S43), imaging range calculation processing (S44), and imaging position determination processing (S45). Each processing will be described in detail below.

[0033] <Scout image processing S42> In abdominal imaging, a 2D scout image is a low-resolution two-dimensional image acquired along the subject's body axis, including the COR plane, and optionally the AX and SAG planes. As shown in FIG. 6, the preprocessing unit 231 first performs filtering on the acquired 2D scout image to remove noise (S421), and then performs edge enhancement to enhance the contrast of the anatomy (S422).

[0034] Next, the tissue extraction unit 233 extracts the imaging target region using the edge-enhanced scout image. To this end, the edge-enhanced scout image is first binarized using a discriminant analysis method or the like to create a mask in which the area where the subject is present is represented by 1 and the area where the subject is not present is represented by 0 (S423). The area where the subject is present is estimated from this mask. For example, if the imaging target is the abdomen, the abdomen and upper limbs may be simultaneously imaged in the scout image, and the positions of the abdomen and upper arms are estimated. Once the position of the abdomen has been estimated, the midline is estimated using the mask image of the abdomen (S424). The abdomen and upper arms can be automatically distinguished, for example, from the area and positional relationship (such as the distance from the center of the image) of multiple regions with a pixel value of 1, and a known automatic discrimination algorithm can be used. For midline estimation, a commonly established algorithm can be used, such as a method of superimposing an original image and its inverted image and determining the perpendicular bisector of the center of gravity of the original image and the inverted image as the midline of the image.

[0035] Next, for the abdominal image extracted using the mask (referred to as a mask image), one-dimensional projection images are created in the craniocaudal direction for each of the right and left halves of the body, separated down the midline, and the boundary position between the lung field and the diaphragm is estimated (S426). This process S426 will be described in detail with reference to FIG. 7. Assume that an abdominal mask 701, as shown in FIG. 7, is obtained in the mask image generation step S423. An abdominal mask image (not shown) is obtained by multiplying this mask 701 by the scout image. This abdominal mask image is projected in a direction perpendicular to the body axis, resulting in a one-dimensional projection image 702 in the craniocaudal direction. As shown in the figure, the image of the subject portion exhibits a significant change in signal value between the lung field and the diaphragm. Therefore, a gradient 703 is calculated for the subject portion of the projection image, and the position where the maximum peak is obtained is estimated as the boundary position (x, y) between the lung field and the diaphragm. Starting from the estimated pixel, the boundary between the mask image and the background is searched pixel by pixel to detect the boundary line between the lung field and the diaphragm.

[0036] Next, the position of the imaging region (for example, the liver) is extracted using the boundary position (x, y) of the diaphragm as the starting point (S427). A known image processing method such as an active shape model or a region growing method can be used to extract the organ position.

[0037] This completes the processing (S42) for the two-dimensional scout image.

[0038] <Video processing S43> A moving image is an image acquired by the imaging section 100 capturing images over at least one period of the subject's respiratory movement, and is made up of a plurality of frame images.

[0039] Details of step S43 are shown in Fig. 8. As shown in the figure, in this step, the pre-processing unit 231 also processes the moving image (noise removal and edge enhancement), and then, similar to the processing of the 2D scout image (S423 to S426), calculates the boundary position (x, y) of the diaphragm in the first frame image of the moving image that has been subjected to edge enhancement processing (S431).

[0040] Next, the respiratory phase calculation unit 237 performs the following process. That is, for pixels having feature values ​​at the boundary position (x, y), the movement amount for each frame is calculated using optical flow or the like (S432). This movement amount corresponds to the movement amount of the diaphragm due to breathing. By performing this process on frame images of one or more respiratory cycles, a movement amount variation 900 is obtained, as shown in FIG. 9. FIG. 9 shows an example in which the respiratory cycle is estimated from the variation in the boundary position (the position of the boundary where the brightness changes from white to black) for multiple pixels (1 × 7 pixels in the illustrated example) in the craniocaudal direction including the position of the diaphragm for each frame. From this variation in movement amount, the respiratory phase during the subject's free breathing is estimated (S433).

[0041] The navigator position determination unit 239 sets the diaphragm boundary position (x, y) calculated in step S432 as the application position of the navigator echo (S434). If the breathing method (20 in FIG. 2) specified as the imaging condition is respiratory-gated imaging, this information 40 is passed to the imaging unit 100, and the imaging unit 100 performs imaging to acquire a navigator echo from a region crossing the diaphragm boundary position, for example. If breath-hold imaging is not selected as the breathing method, this step S434 may be omitted.

[0042] <Image capture range calculation S44> In this process, the imaging range is calculated based on the organ positions extracted in step S427. The minimum rectangular range including the top, bottom, left, and right edges of the mask is calculated as the range in which the subject exists, and the FOV, rectangular FOV, and anti-aliasing size are calculated. This process will be described with reference to FIG.

[0043] 10 shows an example of the results of organ position extraction. First, the upper end (x_lt, y_lt), lower end (x_lb, y_lb), left end (x_ll, y_ll), and right end (x_lr, y_lr) of the liver are calculated using the extracted liver position image 901. The rectangular area circumscribing these four points, i.e., the rectangular area connected by (x_ll, y_lt), (x_lr, y_lt), (x_ll, y_lb), and (x_lr, y_lb), is calculated as the minimum imaging area.

[0044] From the respiratory phases obtained in the moving image processing (S43), liver position extraction is also performed for each frame image of the inspiration phase and expiration phase, and rectangular areas 902-1 and 902-2 are obtained for inspiration and expiration, respectively. The area connected by the upper side (x_ll, y_lt) (x_lr, y_lt) of the expiration rectangular area and the lower side (x_ll, y_lb) (x_lr, y_lb) of the inspiration rectangular area is calculated as the maximum imaging area 903. Note that instead of obtaining the rectangular areas for inspiration and expiration from the frame images of those phases, the amount of diaphragm movement for each frame obtained in step S432 may be used. In this case, the respiratory phase of the scout image from which organ position extraction was performed is identified from the variation in the amount of movement, and the difference between this and the amount of movement during inspiration and expiration is added to the rectangular area obtained from the liver position image 901.

[0045] This process calculates a total of three imaging ranges: minimum imaging ranges 902-1 and 902-2 during breath holding, and imaging range 903 during free breathing. In this way, the optimal imaging range can be set depending on whether the patient is breathing or not.

[0046] <Image capture position determination S45> Finally, the imaging position determination unit 230 calculates the imaging position according to the examination information and the input breathing method. The imaging position includes the slice position and angle.

[0047] Specifically, in S41, if breath-hold imaging during exhalation is selected, the imaging range is set to the minimum imaging range 920, and the slice position is calculated so that the upper end of the imaging range is positioned at the position of the exhalation phase. Similarly, if breath-hold imaging during inhalation is selected, the imaging range is set to the minimum imaging range 920, and the slice position is calculated so that the upper end of the imaging range is positioned at the position of the inhalation phase.

[0048] Furthermore, in S41, if respiratory-gated (free-breathing) imaging is selected, the imaging range is set to the maximum imaging range 930, and the slice position is calculated so that the upper end of the imaging range is positioned in the expiratory phase.

[0049] The imaging position determination unit 230 outputs the parameters and numerical values ​​(slice position, imaging range, FOV or RFOV, anti-aliasing size, etc.) 50 that determine the imaging position calculated in the above process S45 to the measurement control unit 210 or the display device 301. The imaging position determination unit 230 automatically sets the position and angle of the slice line in accordance with the imaging range that matches the breathing method specified by the user (S45). In addition, in the case of a scan task in which respiratory induction is specified, the imaging position determination unit 230 automatically sets the navigator echo application position.

[0050] As described above, the MRI apparatus of this embodiment detects changes in organ position due to respiratory motion (respiratory phase) using scout images and moving images, calculates the minimum and maximum imaging ranges using the results, and automatically sets the imaging range according to the breathing method. This makes it possible to handle both breath-holding imaging and free-breathing imaging, and to perform imaging with an appropriate imaging range for breath-holding imaging at any respiratory phase. This reduces the burden on the user associated with setting the imaging position, prevents imaging failures, and reduces the burden on the subject and the user.

[0051] <Embodiment 2> In the first embodiment, the imaging range can be automatically set using a scout image, thereby enabling the imaging range to be set according to the subject's body type. However, when the imaging range (FOV, number of slices, slab thickness, etc.) is changed according to the subject's body type, it may be necessary to change the values ​​of related parameters. Changing the values ​​of related parameters may unintentionally change the desired imaging conditions that have been set. For example, this may result in an extension of the imaging time or a decrease in spatial resolution.

[0052] This embodiment is characterized by the addition of a function that, when it becomes necessary to adjust the imaging parameters following the automatic setting of the imaging range, determines whether or not adjustment of the imaging parameters is necessary so that the imaging conditions desired by the user are achieved, and automatically adjusts the parameters.

[0053] Fig. 11 shows a functional block diagram of the computer 200 to which the above functions have been added. In Fig. 11, the imaging position determination unit 230 has the same configuration as that shown in Fig. 3. As shown in the figure, in this embodiment, a parameter adjustment unit 240 is added to the computer 200. Below, the processing of the imaging position determination unit 230 and the parameter adjustment unit 240 in this embodiment will be described with reference to Fig. 12, focusing on differences from the first embodiment.

[0054] In this embodiment, a scout image is captured (S61), an imaging range is calculated on the scout image, and an adjustment is made as necessary to determine the imaging position (S62), as in the previous embodiment. The imaging parameters determined by the determined imaging range are reflected in the parameters of the task for actually capturing the inspection image (S63).

[0055] At this point, the parameter 60 related to the imaging range is a value manually set by the user or automatically calculated by the system.

[0056] Here, when the user selects a task set as an imaging parameter (S64), the parameter adjustment unit 240 executes a parameter consistency check (S65). In this process S65 (consistency check), since the parameter 60 related to the imaging range has been changed from its default value, a process is executed to determine whether any parameters need to be changed in conjunction with the change, and to calculate the values ​​to be set if such changes are necessary. The check to determine whether any of the parameters 60 need to be changed in conjunction with the change is performed using information set in the system, such as a lookup table. For example, if the FOV of the parameter 60 is greater than the default value (S66), increasing the FOV will not prevent imaging, i.e., there are no parameters that need to be changed, so the value is simply changed to the value of the parameter 60 (S67). On the other hand, if the FOV is smaller than the default value, the value of the parameter 60 remains the default value.

[0057] Furthermore, if the number of slices among the calculated parameters 60 is greater than the default value (S68), the number of imaging slices increases, so imaging is possible but the imaging time will be extended. In this case, rather than starting imaging as is, it is necessary to determine whether or not other parameters need to be changed depending on the case in which the user would like, such as whether to prioritize imaging time or whether an extension of imaging time is acceptable.

[0058] In such a case, the changeable parameters and setting values ​​are calculated for each pattern corresponding to each case and displayed on the operation screen of the display device 301 (S611 to S613). At this time, options (Suggestions) are presented to the user as criteria for determining which case (pattern) to select (S611). An example of the Suggestions display is shown in FIG. 13. In this example, four options are presented: (1) scan the required region without reducing the set resolution even if it extends the total task time; (2) cover the required region even if it results in lower resolution without extending the time; (3) reflect an increase in the number of slices within the range that does not result in a parameter check failure; and (4) return to the original (default) parameters. By displaying these Suggestions, the parameters can be adjusted according to the user's priorities. In addition to the Suggestions (1) to (4), conventional Suggestions (e.g., changing the TR) may be displayed and these options may be additionally selectable.

[0059] When the user selects a desired case from the options (suggestions) displayed on the display device 301 (S612), the parameter values ​​are changed to the parameter values ​​calculated for the selected case (S613), and imaging is performed (S69). The flow of processing in which the parameter adjustment unit 240 automatically calculates the parameters in accordance with the four options described above is shown in FIG.

[0060] A suggestion is displayed (S71), and if the user selects case (1) (S72), parameter adjustment is performed to divide the imaging into multiple times (S77). If case (2) is selected (S73), depending on whether 2D or 3D imaging is selected (S75), the slice thickness is increased and the slice spacing is automatically calculated (S78) for 2D imaging, and the slab thickness is increased for 3D imaging (S79). If case (3) is selected (S74), the number of slices (2D) / number of slice encodes (3D) is increased (S710) for both 2D and 3D imaging (S76). If case (4) is selected (S74), the original state is maintained without any changes (S711). At this time, the imaging range is also restored to the value before adjustment.

[0061] According to this embodiment, in addition to the same effects as those of the first embodiment, parameters can be automatically calculated in conjunction with changes in the imaging range, thereby reducing the effort required by the user. Furthermore, the dependency of parameter setting on the operator is reduced, reducing setting errors that can lead to failed examinations. Furthermore, multiple options are presented to the user in an easily understandable manner along with the results of automatic calculations, allowing the user to select the desired changes and set the parameters accordingly. [Explanation of symbols]

[0062] 100: Imaging unit, 200: Computer, 210: Measurement control unit, 220: Calculation unit (image generation unit), 230: Imaging position determination unit, 231: Preprocessing unit, 233: Tissue extraction unit, 235: Imaging range calculation unit, 237: Respiratory phase calculation unit, 239: Navigator position determination unit, 240: Parameter adjustment unit, 300: UI unit, 301: Display unit, 302: Input device.

Claims

1. an imaging unit that acquires an image of a subject based on nuclear magnetic resonance; and an imaging position determination unit that calculates an imaging range of the subject and determines an imaging position; the imaging position determination unit calculates, using an image acquired by the imaging unit executing a scout scan, a plurality of imaging ranges including a minimum imaging range that includes a predetermined tissue and a maximum imaging range that includes a range in which the tissue displaces within a cycle of periodic motion, and determines one of the plurality of imaging ranges as the imaging position for the main scan depending on imaging conditions.

2. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus is characterized in that the imaging position determination unit includes a tissue extraction unit that detects the position and area of ​​a target organ from the image obtained by the scout scan.

3. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus according to claim 1, wherein the imaging position determining unit calculates a phase of periodic motion of the subject from an image obtained by the scout scan.

4. 2. The magnetic resonance imaging apparatus according to claim 1, The periodic motion is respiratory motion, 10. The magnetic resonance imaging apparatus according to claim 9, further comprising a UI unit that displays a GUI for allowing a user to select either breath-hold imaging or respiratory gating as the imaging condition.

5. 2. The magnetic resonance imaging apparatus according to claim 1, the imaging conditions include breath-hold imaging; The magnetic resonance imaging apparatus according to claim 1, wherein the imaging position determining unit determines the imaging position at a position according to the phase of respiratory movement, with the imaging range set to a minimum imaging range, during breath-hold imaging.

6. 2. The magnetic resonance imaging apparatus according to claim 1, the imaging conditions include respiratory-gated imaging; The magnetic resonance imaging apparatus according to claim 1, wherein the imaging position determining unit determines the imaging position by setting an imaging range as a maximum imaging range during respiratory-gated imaging.

7. 2. The magnetic resonance imaging apparatus according to claim 1, the imaging conditions include respiratory-gated imaging; The magnetic resonance imaging apparatus according to claim 1, wherein the imaging position determining unit includes a navigator position determining unit that determines an application position of a navigator echo used in the respiratory gated imaging.

8. 2. The magnetic resonance imaging apparatus according to claim 1, The magnetic resonance imaging apparatus further comprises a parameter adjustment unit that adjusts values ​​of imaging parameters in accordance with the imaging range calculated by the imaging position determination unit.

9. 9. The magnetic resonance imaging apparatus according to claim 8, The magnetic resonance imaging apparatus according to claim 1, wherein the parameter adjustment unit compares imaging parameters determined by the imaging range with preset imaging parameters, and determines whether or not the imaging parameters need to be changed.

10. 9. The magnetic resonance imaging apparatus according to claim 8, The magnetic resonance imaging apparatus, wherein the imaging parameters include a slice thickness, a number of slices, and an FOV.

11. 9. The magnetic resonance imaging apparatus according to claim 8, The magnetic resonance imaging apparatus according to claim 1, wherein the parameter adjustment unit calculates imaging parameter values ​​using a plurality of patterns according to the priority of imaging conditions.

12. 12. The magnetic resonance imaging apparatus according to claim 11, The magnetic resonance imaging apparatus, wherein the parameter adjustment unit presents a GUI that allows a user to select a priority of imaging conditions.

13. 1. A method for determining an imaging position of a subject in magnetic resonance imaging, comprising: calculating a plurality of imaging ranges including a minimum imaging range that includes a predetermined tissue and a maximum imaging range that includes a range in which the tissue moves within a period of the periodic motion, using an image acquired by performing a scout scan; An imaging position determination method comprising determining one of a plurality of imaging ranges as the imaging position for a main scan in accordance with imaging conditions.

14. The imaging position determination method according to claim 13, An imaging position determination method, comprising: determining whether or not an imaging parameter needs to be changed after calculating an imaging range; and, if a change is required, calculating a value of the imaging parameter.

Images