CN101166462A - Magnetic resonance imaging apparatus - Google Patents

Abstract

While a magnetic resonance signal is received a plural number of times during shifting of a table (shifting means), a gradient magnetic field is applied in the direction of shifting the table with the application amounts (intensity and application time period) of the gradient magnetic field in the direction of shifting the table being varied for each of data acquisitions. Unlike the conventional phase encoding, the encoding using this gradient magnetic field in the direction of shifting the table is performed in such a manner that a series of phase encodings are performed at different positions of a subject to be examined. Therefore, Fourier transform cannot be applied to the image reconstruction. In view of this, the reconstruction is performed by deciding the distribution of the magnetization of total FOV for the subject in such a manner that minimizes the sum of the squares of the respective absolute values of the differences between the received signals and the signals established as parameters and calculated from the distribution of the magnetization. Even when the signal acquisition range in the direction of shifting the table is narrow, the inventive magnetic resonance imaging apparatus performs an imaging, while continuously shifting the table, thereby achieving a high-rate imaging having a wide view field.

Description

Magnetic resonance imaging apparatus

Technical field

The present invention relates to use the testing fixture (MRI:Magnetic ResonanceImaging) of nuclear magnetic resonance, NMR, relate in particular to and use portable workbench, the technology of making a video recording greater than the visual field in the photographic zone that limits in the device.In addition, relate to the equipment energy characteristic data that image in this camera technique reconstructs needs.

Background technology

The MRI device makes the hydrogen nuclei that is included in the procuratorial work object tissue that is positioned in the magnetostatic field space produce nuclear magnetic resonance, NMR, obtains the medical diagnostic imaging apparatus of the layer image of procuratorial work object from the NMR signal that produces.In the MRI device, be limited to the magnetostatic field space, so only can photograph in the past in narrower and small zone because can obtain the zone of signal, but this year, by movable workbench, can carry out the whole body photography, use the new progress of the whole body shielding (screening) of MRI to begin.

Whole body photography roughly is divided into two kinds of multistation Photographic technique (non-patent literature 1) and travelling table Photographic techniques (patent documentation 1, non-patent literature 2).No matter which kind of all is the limited photographic zones (being called sub FOV) at the MRI device, the method for being photographed in bigger zone (being called total FOV).The multistation Photographic technique is meant and whole body is divided into sub FOV and photographs, and these images are joined together the Photographic technique of making the whole body image.Because it is identical with common Photographic technique in the photography that each sub FOV carries out, so have the advantage that easily is suitable for camera work in the past, but also exist because magnetostatic field is inhomogeneous or the non-linear of leaning magnetic field causes in the anamorphose of office, junction surface, the rough shortcoming in bonding part, or because in movable workbench, can't photograph the elongated shortcoming of its minute photography time.Under the narrow situation in the visual field of movable workbench direction, increase the number of times that interrupts photography and travelling table, there is further elongated problem of photography time.

On the other hand, the travelling table Photographic technique is when making movable workbench, obtain the Photographic technique of signal, in to the travelling table Photographic technique of photographing along the section of the moving direction of workbench, must will read (read out) direction and be made as the moving direction of workbench, but have the advantage that obtains jointless image with the short time.

Patent documentation 1: the Japan Patent spy opens the 2003-135429 communique

Non-patent literature 1:ThomasK.Foo, Vincent B.Ho, Maureen N.Hood, HaniB.Marcos, Sandra L.Hess, and Peter L.Choyke, Radiology.2001:219:835-841.

Non-patent literature 2:DavidG.Kruger, Stephen J.Riederer, Roger C.Grimmk, andPhillip J.Rossman, Magn.Reson.Med.2002:47:224-231.

In above-mentioned travelling table Photographic technique, can obtain jointless image at short notice, but because exist read direction to be necessary for the restriction of movable workbench direction, thus exist sub FOV under situation about narrowing down on the moving direction, the problem that photography time increases.

That is, under the situation that sub FOV narrows down on the movable workbench direction, for obtaining the image of same exploring degree, by reducing the hits of frequency coding direction (read direction), the phase code number does not change.Usually photography time and phase code number are roughly proportional, and are subjected to from the influence of the hits of frequency coding direction few.Thereby on the movable workbench direction, the situation that sub FOV is narrow might as well, wide situation obtains the identical time of cost to the data that are used for a sub FOV, on the movable workbench direction, under the narrow situation of sub FOV, the photography time in the visual field of expansion is elongated.

Be head it off, consider at the enterprising line phase coding of movable workbench direction, but use the thinking methods in the past of using Fourier transformation for reconstructing, be difficult at the enterprising line phase coding of movable workbench direction.The reasons are as follows.In the travelling table Photographic technique, the scope of excitation changes usually on the movable workbench direction.During a signal instrumentation that reads, promptly in the time of the variation that can ignore excitation range, finish all codings, but under the situation of phase code, because give different codings to each signal instrumentation, before institute finished down to all codings, excitation range had greatly changed.In the image that utilizes Fourier transformation reconstructs, accept a series of prerequisite that is encoded to the object images scope, and be not suitable for this kind situation.

Summary of the invention

Therefore, though the object of the present invention is to provide a kind of under the narrow situation of the sub of movable workbench direction FOV, the MRI device that can photograph to the image of total FOV at short notice.

When MRI device of the present invention makes workbench (travel mechanism) mobile, apply leaning magnetic field along the movable workbench direction, change the applied amount (intensity or application time) of the leaning magnetic field of movable workbench direction when receiving magnetic resonance signals repeatedly, every acquisition data.Coding based on the leaning magnetic field of described movable workbench direction is to make a series of phase code at the new coding (being called the slip phase code) of checking that the different position of object is carried out.By according to the signal that makes reception with by secondary power and the mode that determine of the absolute value of the difference of the signal that calculates as the distribution of magnetization of coefficient settings minimumly, the distribution of magnetization of checking the total FOV in the object is reconstructed.

For by as the magnetized distribution of coefficient settings, i.e. the distribution of magnetization signal calculated of hypothesis, use non-linear, the equipment energy characteristic data such as magnetostatic field is inhomogeneous, irradiation coil activation profile, the distribution of trusted coil sensitivity of leaning magnetic field.MRI device of the present invention uses following equipment energy characteristic data to carry out image and reconstructs, and is used to obtain the measurement (below, be called equipment energy characteristic and measure) of the NMR signal of this equipment energy characteristic, by the NMR signal calculating apparatus performance data of measuring that is:.The measurement of equipment energy characteristic data can be independent of the measurement (below, be called this photography) of the NMR signal that is used to obtain the distribution of magnetization of checking object, also can carry out simultaneously with this photography.Under the former situation, for example, equipment energy characteristic is measured and is undertaken by the multistation Photographic technique.That is, make travel mechanism between a plurality of stations, move each station actuating unit feature measurement in travel mechanism.In addition, under the latter's the situation, the part of the NMR signal of measurement in this photography can be also used as the signal of obtaining the equipment energy characteristic data.A part of NMR signal of institute's dual-purpose is preferably the low frequency region data.

MRI device of the present invention can be useful in any of vertical magnetic field type, horizontal magnetic field type.In addition, the slip phase code is independent of frequency coding or phase code and carries out, and therefore, can also be useful in any photography of 2D, 3D, multistation.

According to the present invention as can be known,, make under the situation that the sub of movable workbench direction FOV dwindles by the phase code of sliding along the movable workbench direction, can be therewith corresponding and reduce slip phase code with respect to subFOV.Thus, therefore the constant that becomes of the required time of unit distance of coding work platform moving direction, does not influence the length of the sub FOV of movable workbench direction, thereby, can carry out high speed photography.

Description of drawings

Fig. 1 is the figure that expression is suitable for the general survey of MRI device of the present invention, (a) is horizontal magnetic field type device, (b) is vertical magnetic field type device.

Fig. 2 is the figure that expression is suitable for the configuration example of MRI device of the present invention.

Fig. 3 is that the total FOV of object and the figure that signal is obtained the relation in zone are checked in expression.

Fig. 4 is the figure of the order of the described travelling table photography of expression first embodiment of the present invention.

Fig. 5 is the figure that the indication device performance data obtains the relation of the sub FOV that uses sub FOV and this photography.

Fig. 6 is the figure of order of this photography of expression first embodiment.

Fig. 7 is the figure of an example of the expression pulse train that is used for travelling table photography.

Fig. 8 is the figure that is used for reconstituted signal of image and result in the expression 2D photography.

Fig. 9 is the figure of the relation of expression operating position and slip phase code.

Figure 10 is the figure that the expression signal is obtained the equipment energy characteristic in zone.

Figure 11 is other the figure of order of the travelling table photography of expression MRI device of the present invention.

Figure 12 is other the figure of example of the expression pulse train that is used for travelling carriage photography.

Figure 13 is that expression is used for the reconstituted signal of image of 3D photography and the figure of result.

Figure 14 is the figure of an example of order of the travelling table photography of expression the 5th embodiment of the present invention.

Figure 15 is the figure that the equipment energy characteristic data of expression the 5th embodiment of the present invention obtain order.

Figure 16 (a) is the figure that represents the relation of slip phase code in the modification of the 5th embodiment and operating position respectively (b).

Figure 17 is other the figure of example of the order of expression the 5th embodiment.

The figure of Figure 18 SPE data that to be expression obtained by other example of the order of the 5th embodiment.

Figure 19 is the inspection object of expression in the 6th and the 7th embodiment and the figure of the relation of coil.

Figure 20 be the explanation the 6th and the 7th embodiment the equipment energy characteristic instrumentation in coil position.

Figure 21 is the figure that object is checked in expression.

Figure 22 is the reconstruct image of expression based in the past travelling table method.

Figure 23 is the image that reconstructs of expression first embodiment.

Figure 24 is the figure that reconstruct image of expression based on the inspection object of Figure 21 of the 5th embodiment.

Figure 25 is the comparison of method and photography time of the present invention in the past.

Among the figure, 101-produces the Magnet of magnetostatic field; The 102-gradient magnetic field coil; 103-checks object; The 104-sequencer; 105-leaning magnetic field power supply; 106-high frequency magnetic field generator; 107-irradiation coil; The 108-receptor; The 109-computer; The 110-display; The 111-storage medium; The 112-shim; 113-shim power supply; The 114-receiving coil; The 301-workbench; The 302-Worktable control device.

The specific embodiment

Below, with reference to accompanying drawing, embodiments of the present invention are described.

At first, the structure that is suitable for MRI device of the present invention is described.Fig. 1 (a) and (b) are respectively the MRI schematic representation of apparatus of the MRI device and the vertical magnetic field type of horizontal magnetic field type, and MRI device of the present invention can be applicable to the MRI device of arbitrary type.In the MRI of horizontal magnetic field type device, the static field magnet 101 of the solenoid type of the magnetostatic field of employing generation horizontal direction etc., acceptor 103 is admitted in the hole of Magnet to lie in the state on the workbench 301, photographs.In addition, the MRI device of vertical magnetic field type spatially disposes a pair of static field magnet 101 up and down what place acceptor 103, and acceptor 103 is admitted in the magnetostatic field space to lie in the state on the workbench 301.And, arrow r represents the moving direction of workbench among the figure, and in the MRI device of the horizontal magnetic field type shown in (a), the magnetostatic field direction is consistent with r, in the MRI device of the vertical magnetic field type shown in (b), the moving direction of workbench is and the orthogonal direction of magnetostatic field direction.

Fig. 2 is the block diagram of the schematic configuration of expression MRI device, the structural element mark same-sign identical with Fig. 1.As shown in the figure, in the magnetostatic field space (photographing space) that static field magnet 101 produces, dispose: the unifluxor circle (shim coil) 112 that is used to improve the uniformity of magnetostatic field; Give the gradient magnetic field coil 102 of magnetostatic field gradient; The irradiation that is used for producing the high frequency magnetic field that the atomic nucleus (being generally proton) to the atom that constitutes the tissue of checking object (people) encourages is with coil 107; Be used to detect from the receiving coil 114 of checking the NMR signal that object sends etc.The workbench 301 that acceptor 103 is lied down is controlled by Worktable control device 302, when sending into acceptor 103 in the photographing space, it is moved in the space.Worktable control device 302 can carry out the speed of workbench, the control and the monitoring of position.

Above-mentioned unifluxor circle 112, gradient magnetic field coil 102, irradiation are connected with unifluxor circle power supply 113, leaning magnetic field power supply 105, high frequency magnetic field generator 106, receptor 108 respectively with receiving coil 114 with coil 107, and utilize sequencer 104 control actions.Sequencer 104 is controlled with the moment, the intensity (pulse train) of programming in advance, so that these device work, the control of start pulse sequence etc. is carried out in the driving of cooperating platform control device simultaneously.In addition, the MRI device possesses computer 109, display 110, storage medium 111 etc. as signal processing system.

In this kind structure, the high frequency magnetic field that high frequency magnetic field generator 106 produces, is applied to and checks on the object 103 with coil 107 by irradiation.Receive by receiving coil 114 from the signal of checking object 103 generations, and carry out detection at receptor 108.The nmr frequency that forms the benchmark of detection is provided with by sequencer 104.Signal after being detected is sent to computer 109, and the signal processing that carries out that image reconstructs herein etc.In the present invention, except that the computing of common corrected Calculation, Fourier transformation etc., carry out travelling table photography described later image alone and reconstruct computing especially.When the result of computer 109 is presented at display 110, be stored in the storage medium 111.As required, signal or condition determination after the detection are stored in the storage medium 111.

First embodiment

Next, the embodiment of the travelling table Photographic technique that the present invention is adopted describes.Fig. 3 represents the photographic zone (sub FOV) in the MRI device and constitutes the relation in the wide visual field (being the whole body total FOV of acceptor herein) of photography purpose that Fig. 4 represents to photograph and reconstructs the order of processing with image.

In the travelling table photography, as shown in Figure 3, workbench 301 (checking object 103) is moved to the direction of arrow 303, photograph simultaneously.Receiving coil 114 promptly is fixed on the receiving coil in the device, also is fixed on the combination of a plurality of coils on the acceptor, but herein to using the situation that is fixed on the receiving coil in the device as shown in Figure 3 to describe.The visual field when single signal is obtained (sub FOV) 304 can be set arbitrarily, but preferably is set in and the size that can receive the regional same degree of enough big signal.The visual field when signal of single is obtained is the size that has limited, but by movable workbench is photographed simultaneously, whole body (total FOV) 305 is photographed.Photography for 2D, 3D all can, and the slip phase directional is set at the movable workbench direction.For example among the 2D, section be coronalplane, sagittal plane all can, so long as in face, comprise the section of the axle of movable workbench direction, be not particularly limited.Read direction is chosen as and the orthogonal direction of movable workbench direction.In following embodiment, describe with 2D, if but increase slip phase code coding in addition, then constitute the situation of 3D.

Photography comprises shown in Fig. 4 (a): the step 601 that obtains equipment energy characteristic data 604 such as coil sensitivity; Obtain the step 602 of the data 605 of checking object; Operative installations performance data and inspection object data are to checking the step 603 that image 606 calculates that reconstructs of object.

In step 601, be used to try to achieve the distribution of magnetostatic field, the equipment energy characteristic data that the activation profile of coil 107 and the sensitivity distribution of receiving coil 114 etc. are used in irradiation.Try to achieve from image that magnetostatic field distributes or irradiation can be adopted known method with the activation profile of coil or the method for coil sensitivity distribution.For example distribute can be by obtaining different signal of echo time for magnetostatic field, and detect at the phase contrast of obtaining the signal that produces between the difference of time and obtain distributing.Irradiation can be by obtaining the different signal of irradiation power with the activation profile of coil, and detected intensity difference and obtain distribution.In addition sensitivity distribute can by to by as the view data that obtains of coil that having of body coil, even sensitivity distributed and compare by the view data that the coil that uses when the photography of step 602 obtains try to achieve.Perhaps, if obtain the view data of the emulation of homogenizing, only with this, the effect that magnetostatic field distribution, activation profile, sensitivity are distributed is as generalized equipment energy characteristic.And then, trying to achieve equipment energy characteristic, magnetostatic field distributed or activation profile, the sensitivity some in distributing is replaced with the equipment energy characteristic of trying to achieve for the acceptor of reality by the emulation of homogenizing, can access more accurate equipment energy characteristic data.These equipment energy characteristics are used for image described later and reconstruct.

Below, the photography (equipment energy characteristic instrumentation) that is used to try to achieve the equipment energy characteristic data is described particularly.

The equipment energy characteristic data comprise: leaning magnetic field is non-linear, magnetostatic field is inhomogeneous, shine the activation profile with coil, the sensitivity distribution of receiving coil etc.Wherein, leaning magnetic field is non-linear because do not rely on acceptor substantially, so needn't obtain in each photography, will wait the data of other instrumentation mensuration to be kept in the storage medium in advance with the photography of using emulation.

Thereby, in equipment energy characteristic instrumentation step 601, be used to try to achieve and photography by the distribution of the inhomogeneous signal intensity that causes of magnetostatic field, equipment energy characteristic data that signal intensity that irradiation constitutes with the activation profile of coil 107 and the sensitivity distribution of receiving coil 114 etc. is relevant with phase place.

Fig. 4 (b) is indication device characteristic instrumentation step 601 at length.As shown in the figure, this photography is that workbench is moved between station, and carries out RF at each station and send the multistation photography that the step that receives repeats, thereby obtains the view data (step 631) of each station.Photography in the case can be adopted known 2D Photographic technique or 3D Photographic technique.Because the equipment energy characteristic data change usually smoothly,, and can shorten photography time so low exploring degree is enough.

The equipment energy characteristic data can be by trying to achieve divided by the even image of total FOV at the image that each station obtains.Evenly image is meant the image that obtains under uniform situations such as coil sensitivity, and the even image of totalFOV for example can be made (step 632,633) by the image of synthetic each station.

In the photography that is used for trying to achieve the equipment energy characteristic data, the equipment energy characteristic data obtain the sub FOV of usefulness, as shown in Figure 5, are set at enough greatly, to cover the scope integral body of the signal obtained in this photography.In addition, overlapping sub FOV to a certain degree between station.Thus, be easy to carry out the interpolation of the synthetic and equipment energy characteristic data of even image.For obtaining correct equipment energy characteristic data, preferably only think that with each station image uniform zone covers the mode of total FOV, overlapping sub FOV.In addition, comparing, under the situation of preferential shortening photography time, more reducing overlapping with correctness.For making more uniform total FOV image, also can append and use other the photography of coil such as body coil.

After utilizing the photography of each station to obtain view data, the even image of the synthetic totalFOV of image that obtains by each station.Next, the image that each station is obtained is divided by this total FOV image, thus the position relation that obtains acceptor and coil on each station down, with by the distribution of the inhomogeneous signal intensity that causes of magnetostatic field, shine the equipment energy characteristic data that the sensitivity distribution of activation profile with coil, receiving coil is consistent.And, in this calculates, as required, give low pass filter, or shelter calculating of no acceptor regionally the image that obtains.Thus, with respect to noise acquisition device performance data stably.

The equipment energy characteristic data that so obtain are data of each station, but in image reconstructs, and need the equipment energy characteristic data of the position of the acceptor that changes continuously in this photography.When image reconstructs, can use the equipment energy characteristic data at hithermost station place, but preferably generate by the equipment energy characteristic data between each station are carried out interpolation.Thus, acquisition device performance data effectively.

Next, the step (this photography) 602 that obtains the data of checking object is described.In this step 602, as expression at length among Fig. 6 (a), mobile (step 607) of the platform of at first starting working.Next the transmission of carrying out RF receives (step 608).The transmission of RF is received in and makes movable workbench repeat (step 609) before covering total FOV.Travelling table is finished obtain (step 610) of data with after covering totalFOV.

The movable workbench scope that is used to cover total FOV under the situation of as shown in Figure 3 whole body photography, from till position to the position 301 of inspection object of describing with solid line 103 and workbench of the acceptor of dotted lines and workbench for being used to cover the moving range of total FOV.Usually, for can become in the translational speed of workbench fixing after, the beginning data obtain, interval as helping starting, began travelling table before moving range, and be positioned at the position that the formation signal is obtained the center in zone at the end of total FOV, the beginning data obtain, the other end at total FOV constitutes the moment that signal is obtained the position at regional center, finishes data and obtains.Operating position is detected by Worktable control device 30, and with its direct information sequencer.

Fig. 7 is illustrated in an example of the pulse train that adopts in the photography of step 608.And among Fig. 7, RF represents to encourage high-frequency impulse, Gs presentation layer to select leaning magnetic field, GP represent to slide phase code leaning magnetic field, Gr to represent to read leaning magnetic field.This pulse train is from being that pulse train is identical with general 2D gtadient echo in appearance, but the Gp axle is consistent with the moving direction of workbench, and on the moving direction of workbench each obtain the position different obtain data, change applied amount and apply on the leaning magnetic field this point different (intensity or time).In the present invention, the leaning magnetic field with this kind Gp axle is called slip phase code leaning magnetic field.

In photography, possess at first checking that object applies phase (dephase) with a layer leaning magnetic field 203, thereby average out with leaning magnetic field that layer leaning magnetic field 202 by the back applies.Next, apply excitation high-frequency impulse 201 simultaneously with layer leaning magnetic field 202, thereby only the layer of expecting is encouraged.Thus, only specific layer produces magnetic resonance signal 208.In addition, apply poly-phase (rephase) layer leaning magnetic field 204 at once, thereby will go the part of phase to turn back to original state by layer leaning magnetic field 202.Next, apply slip phase code leaning magnetic field 205.Apply simultaneously mutually with reading leaning magnetic field 206, thereby reach balance with the leaning magnetic field that leaning magnetic field 207 applies that reads by the back.Next apply and read leaning magnetic field 207, thereby cause once subtracting the magnetic resonance signal 208 that declines and becoming the big moment once more, the instrumentation signal with reading leaning magnetic field 206 by going mutually.At last, apply poly-mutually with slip phase code leaning magnetic field 209 with gather mutually with reading leaning magnetic field 210, the coding when magnetic resonance signal 208 is obtained returns former state, and purchases next excitation high-frequency impulse 211.

From excitation high-frequency impulse 201, behind the elapsed time TR, encourage to encourage high-frequency impulse 211, and repetition and above-mentioned same leaning magnetic field apply instrumentation with signal.But, when repeating, make slip phase code leaning magnetic field 205, poly-mutually with slip phase code leaning magnetic field 209 variation respectively, give the positional information of slip phase-encoding direction.

So, in movable workbench, the relation of carrying out the movement speed v of the workbench under the situation about obtaining of magnetic resonance signal 208 and TR every the TR time constitutes the relation with following formula (1) expression.

[several 1]

V＝FOV _total/N _total/TR (1)

In the formula, FOV _TotalThe size of the total FOV305 of expression movable workbench direction, N _TotalExpression reconstructs the matrix size of the movable workbench direction of image.

The maximum of field is made as G _Max, the value G (n) of the slip phase code leaning magnetic field 205 in then repeating for the n time represents with following formula (2).

[several 2]

G(n)＝G _max×(n％N _sub-N _sub/2)/(N _sub/2) (2)

In the formula, N _SubBe the most approaching

[several 3]

[Ntotal×FOVsub/FOVtotal]

Integer, n%N _SubBe divided by N with n _SubAfter remainder.

So, by giving the slip phase code, obtain signal S (n, ky).S (n, ky) in, ky represents the coordinate on the k space corresponding with y direction (read direction).(n ky) is the signal value at the some ky place on the k space of the magnetic resonance signal that receives for the n time to S.(n ky) shown in Fig. 8 (a), is being used for the reconstituted instrumentation memorizer 401 of image as the instrumentation data storage to signal S.

Reconstruct in the calculating (step 603) of image, use the instrumentation data 605 of this kind inspection object and, carry out image and reconstruct computing by the equipment energy characteristic 604 that step 601 obtains.Image reconstructs computing and distributes (initial value) as secondary power and mode minimum of the difference of the signal of the signal of calculation of parameter and actual reception with the magnetic moment that will check object, determines that the magnetic moment of checking object distributes.Below, be elaborated.

(n ky) can use the positional information of workbench to the signal S of instrumentation, represents with following formula (3).

[several 4]

$S(n,k_y)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}M(r,k_y)\exp (-r^{\′}k\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(3\right)$

(n ky) can represent with following formula (4) after read direction (y direction) is done Fourier transformation with signal S.

[several 5]

$s(n,y)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}m(r,y)\exp (-r^{\′}k\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(4\right)$

In formula (3), (4), r is the position of the moving direction of the workbench in the coordinate system that is fixed on the acceptor, and r ' is the position that is fixed on the movable workbench direction in the device rest frame on the whole.

[several 6]

r′＝r-r _table(n) (5)

And, r _Table(n) be the amount of movement of the workbench of the n time magnetic resonance signal when obtaining, can try to achieve by following formula (6).

[several 7]

r _table(n)＝n·v·TR (6)

In addition, k (n) is corresponding with the phase place rotation that the slip phase code leaning magnetic field of being accepted by the n time magnetic resonance signal produces, and defines with following formula (7).If it is expressed as chart, then as shown in Figure 9.

[several 8]

k(n)＝∫γG(n)dt (7)

In the formula, γ is a gyromagnetic ratios.

Have the non-linear of leaning magnetic field, and the leaning magnetic field of G (n) size skew G (n) (1+d (r ')) situation under, the phase place rotation that actual leaning magnetic field produces becomes

[several 9]

∫γG(n)(1+d(r′))dt＝(1+d(r′))∫γG(n)dt＝(1+d(r′))k(n)

The item k (n) of formula (3), (4) (1+d (r ')) be to have considered nonlinear of leaning magnetic field.

Function wn (r ') is in the position relation of acceptor when the n time signal obtained (reception) and coil, the size of the signal that the magnetization by size 1 that expression position r ' locates obtains and the function of phase place distribute definite by the distribution of magnetostatic field, the activation profile of RF coil and the sensitivity of receiving coil.They are obtained by instrumentation equipment energy characteristic data in step 601.Obtain in the zone (sub FOV, the length of movable workbench direction is FOV sub) at signal, the activation profile of the distribution of magnetostatic field, RF coil and the sensitivity of receiving coil distribute same, and outside sub FOV, receiving coil does not have under the situation of sensitivity, w _n(r ') becomes as shown in figure 10 stepped.

(r is that (r y) locates magnetization, promptly desires the image of the inspection object asked, and (r is ky) with (r y) carries out after the inverse Fourier transform quite about y M with m for the position of acceptor y) to m.

By with signal S (n, ky) on read direction, carry out Fourier transformation and the signal s that obtains (n y) is stored in the intermediate store 402 shown in Fig. 8 (b).This signal S (n ky) is checking a series of phase code of carrying out on the diverse location of object from-π to π, thus can't as ago by fourier transform method solve m (r, y).Therefore, among the present invention, at first with the distribution of magnetization m ' of supposition (r y) sets as parameter, use m ' (r, y), through type (4) calculate and try to achieve magnetic resonance signal s ' (n, y).Be the formula of separating (4), need know r ', k (n), (1+d (r ')), w _n(r '), but as mentioned above, r ' can be by formula (5), and k (n) can be tried to achieve by formula (7).In addition, (1+d (r ')) be the nonlinear data of expression leaning magnetic field, try to achieve w in advance _n(r ') try to achieve by the instrumentation of step 601.Thereby, by set m ' (r, y), through type (4) utilization calculate try to achieve s ' (n, y).

And, and so that the magnetic resonance signal s ' that tries to achieve by calculating (n, y) with the magnetic resonance signal s of practical measurement (n, the secondary power of the absolute value of difference y) and (following formula (8)) form minimum mode, (r y), carries out image thus and reconstructs to try to achieve m.

[several 10]

σ ²＝∑ _n|s(n，y)-s′(n，y)| ² (8)

(r y), for example can use null value, also can utilize in advance and carry out the positioning image of instrumentation with low spatial resolution to checking object as the distribution of magnetization m ' that supposes.In the latter case, can be with the optimization computation convergence of chien shih formula (8) in short-term.

Fig. 6 (b) represents the reconstituted order of this kind image.At first will be as distribution of magnetization 612 initialization (step 611) of the inspection object of the most optimized parameter.As mentioned above,, use null value or have under the positioning image data conditions, use its value as initial value.Next, use the initial value 612 and the equipment energy characteristic data of the distribution of magnetization of setting by step 611, and through type (4) is tried to achieve inspection object data 614 (step 613) by calculating.Judge (step 615) to the mean square error of the inspection object data (calculating data) of being tried to achieve by calculating 614 and the inspection object data (instrumentation data) 605 of actual instrumentation is whether enough for a short time, under enough little situation, with this moment the distribution of magnetization that is used to calculate as the image of checking object, reconstruct computing (step 617) thereby finish image.In step 615, for example judge the mean square error under the situation more than the preset threshold, make the mean square error to the direction that reduces, change the most optimized parameter (step 616), and repeat 613,615.(r y) is stored in the image storage 403 shown in Fig. 8 (c) m that so tries to achieve.

As described above, according to present embodiment, by on the moving direction of workbench, giving the photography of slip phase code, and carry out image by the distribution of magnetization of using supposition as the computing of the most optimized parameter and reconstruct, under the narrow situation in the photographic zone of movable workbench direction (sub FOV), can not prolong photography time yet, and can keep with the same image quality of previous methods and enlarged the photography in the visual field.

And, in the past, if, then can not carry out reconstructing based on the image of Fourier transformation at the enterprising line phase coding of movable workbench direction.Reconstruct method as image, replace Fourier transformation, can the mean square error be made as minimum optimization method, carry out image first and reconstruct by adopting.

Further,, reconstruct the equipment energy characteristic data that need, thus, can in the relatively shorter time, easily obtain proximate equipment energy characteristic data by multistation Photographic technique instrumentation according to the present invention.

And, in the above-described embodiment, as the method for imaging illustration pulse train of Fig. 7, but for example also can give the phase code of layer direction to this, carry out the 3D photography.In the case, only, can similarly carry out image and reconstruct by increasing the signal of handling, the dimension of position.

Second embodiment

And, in the above-described embodiment, the constant situation of the translational speed of workbench is illustrated, but the present invention also can be applicable to the situation of moving speed of table variable speed.Below, as second embodiment of the present invention, the situation of moving speed of table variable speed is described.

In the present embodiment, the order of the structure of device and photography is identical with the first above-mentioned embodiment.That is, in step 601, obtain equipment energy characteristic data 604 such as coil sensitivity, next in step 602, obtain the data 605 of checking object.At last in step 603, operative installations performance data 604 and check object data 605, the calculating inspection object reconstruct image 606.But in the present embodiment, sequencer 104 is according to predefined program, or from user's instruction, and the translational speed of workbench is changed.Because the operating position when signal is obtained can be held by Worktable control device, so under the constant as shown in Figure 9 situation of the relation of operating position and slip phase code, the encoding amount when its relation determines that each signal receives.For example, moving speed of table slow during change pulse train, to increase the step number of slip phase code.In pulse train shown in Figure 7, the slip phase code leaning magnetic field 205 of every TR change and poly-definite with the applied amount of leaning magnetic field 209 mutually by operating position.

In addition, in that (n y) tries to achieve m (r by obtaining signal S, y) image graph looks like to reconstruct in the step 603, use distribution of magnetization m ' as parameter (r, y), try to achieve signal s ' (r by formula (4) by calculating, y), and so that this signal s ' (r is y) with the magnetic resonance signal s (n of practical measurement, the secondary power of difference y) and mode minimum, (r, y), this is identical with first embodiment to try to achieve distribution of magnetization m.But ask signal s ' (r, in formula y) (4), the amount of movement r of the workbench when the n time magnetic resonance signal is obtained _Table(n) use the value that obtains by Worktable control device.

[several 11]

$s(n,y)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}m(r,y)\exp (-r^{\′}k\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(4\right)$

K (n) is a function (chart) shown in Figure 9, function w _n(r ') be equipment energy characteristic data by step 601 instrumentation.The distribution of magnetization m that so tries to achieve (r, y) as image data storage in image storage 403, and show as the wide visual field layer image of checking object.

So, according to present embodiment, with first embodiment similarly, can shorten photography time, and photography time as a whole can not prolong for the corresponding sub FOV of minimizing of the photographic zone on the movable workbench direction (sub FOV).And in the present embodiment, because speed is variable, so can follow the photography of endovascular contrast agent or only to desiring the part of photography at length, carry out the photography of spended time etc. with low speed, the degree of freedom of photography enlarges.

The 3rd embodiment

Next, the 3rd embodiment of the present invention is described.

Be characterised in that in the present embodiment, workbench is moved back and forth,, on multiple road, obtain the instrumentation data of checking object in acquisition device characteristic on the road.Figure 11 represents the flow process of the photography in the present embodiment.

As shown in the figure, at first make movable workbench total FOV (step 620), and obtain equipment energy characteristic data 604 (step 621) such as coil sensitivity.Equipment energy characteristic data 604 are stored in the memorizer.Next, make reverse move (step 622) of workbench, obtain the data 605 (step 623) of checking object.The data 605 of checking object are stored in the instrumentation memorizer 401.At last, operative installations performance data 604 and check object data 605, the calculating inspection object reconstruct image (step 624).

Obtain the step 623 of the data of checking object and calculate the step 624 that reconstructs image identical with first or second embodiment.Under the constant situation of the translational speed of workbench, same with first embodiment, the relation of operating position information and slip phase code amount shown in Figure 9 when obtaining based on the signal of determining by moving speed of table, give the slip phase code, and operating position information when using the signal of determining by moving speed of table to obtain, try to achieve the signal value of supposition.In addition, as second embodiment, under the situation of the translational speed that changes workbench arbitrarily, to the location of pixels of determining to reach signal of slip phase code amount, operating position information when using the signal that obtains by Worktable control device to obtain.

In the present embodiment, except that the effect of first and second above-mentioned embodiment, can be one of workbench reciprocal two kinds of the data of (discrepancy in device usually) acquisition device performance data and inspection object, so obtain checking the effect of whole shortening consuming time.In addition, because equipment energy characteristic data (the function w in the formula (4) _n) be not the value of ideal class shown in Figure 10, check the value of surveying when object is in device but adopt, so can access more fine image.Further, as the equipment energy characteristic data, by obtaining the low spatial resolution view data in advance, the most optimized parameter in the time of these data can being reconstructed computing as image (m ' (r, y)) use, thus can shorten the time of optimization computing.

The 4th embodiment

Next, the 4th embodiment of the present invention is described.

In the 4th embodiment, the structure of device is identical with above-mentioned first embodiment with the order of photography.That is, shown in Fig. 4 (a), obtain equipment energy characteristic data 604 such as coil sensitivity by step 601, next, obtain the data 605 of checking object by step 602.At last, by step 603, operative installations performance data 604 and check object data 605, the calculating inspection object reconstruct image 606.But, in the present embodiment, in the step 602, adopt the 3D photography as method for imaging.

Figure 12 represents an example of the pulse train that adopts in the present embodiment.Among the figure, RF represents to encourage high-frequency impulse, in addition, and the Gs presentation layer selects leaning magnetic field, GP represent to slide phase code leaning magnetic field, Gr to represent to read leaning magnetic field.This pulse train is from being that pulse train is identical with general 3D gtadient echo in appearance, but the Gp axle is consistent with the moving direction of workbench, and is that slip phase code axle, Gs axle are different on the phase code axle this point.

In this pulse train, possess at first and to use layer leaning magnetic field 203 mutually, thereby average out with leaning magnetic field that layer leaning magnetic field 202 by the back applies to checking that object applies.Next, apply excitation high-frequency impulse 201 simultaneously with layer leaning magnetic field 202, thereby only the layer of expecting is encouraged.Thus, only specific layer produces magnetic resonance signal 208.In addition, apply to gather and use layer leaning magnetic field 204 mutually, thereby will go the part of phase to turn back to former state at once by layer leaning magnetic field 202.

Next, apply phase code leaning magnetic field 215 and slip phase code leaning magnetic field 205.Apply simultaneously mutually with reading leaning magnetic field 206, thereby reach balance with the leaning magnetic field that leaning magnetic field 207 applies that reads by the back.Next apply and read leaning magnetic field 207, thereby cause once subtracting the magnetic resonance signal 208 that declines and becoming the big moment once more, the instrumentation signal with reading leaning magnetic field 206 by going mutually.Next, apply poly-mutually with phase code leaning magnetic field 216, poly-mutually with slip phase code leaning magnetic field 209 with gather mutually with reading leaning magnetic field 210, the coding when magnetic resonance signal 208 is obtained returns former state, and purchases next excitation high-frequency impulse 211.

From excitation high-frequency impulse 201, behind the elapsed time TR, encourage to encourage high-frequency impulse 211, and with the above-mentioned instrumentation with signal of applying that similarly repeats leaning magnetic field.But, when repeating, making slip phase code leaning magnetic field 205 reach to gather uses slip phase code leaning magnetic field 209 constant mutually, make phase code leaning magnetic field 215 and poly-mutually with phase code leaning magnetic field 216 variation successively, signal to a series of phase code carries out instrumentation (instrumentation of internal recycle), next, with different slip phase code leaning magnetic field 205 and the poly-instrumentation that carries out same internal recycle mutually with slip phase code leaning magnetic field 209, final to all slip phase codes, the phase-coded signal that instrumentation is all.Thus, obtained giving the positional information of layer direction and slip phase-encoding direction.

So, in movable workbench, the relation of carrying out the movement speed v of the workbench under the situation about obtaining of magnetic resonance signal 208 and TR every the TR time constitutes the relation with following formula (9) expression.

[several 12]

V＝FOV _total/N _total/(TR×Ns) (9)

In the formula, FOV _TotalThe size of the total FOV305 of expression movable workbench direction, N _TotalExpression reconstructs the matrix size of the movable workbench direction of image, the phase code number of Ns presentation layer direction.

In addition, repeating to obtain in the process of magnetic resonance signal 208, the maximum of slip phase code leaning magnetic field is being made as G _Max, then (whole as photography, the value G (n) of the slip phase code leaning magnetic field 205 during m (=j+Ns (n-1) is inferior) repeats formula (2) in the past represents the n time in the phase code step of layer direction the j time.

The signal S of instrumentation (ky) can represent with following formula (10) for n, kx by the positional information of use workbench.

[several 13]

$S(n,k_x,k_y)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}M(r,k_x,k_y)\exp (-r^{\′}k\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(10\right)$

Herein, kx, ky represent the coordinate on the k space corresponding with layer direction (x direction) and read direction (y direction) respectively.N represents the n time slip phase code.(n, kx ky) can be as the formula (11) after layer direction (x direction) and read direction (y direction) carry out Fourier transformation with this signal S.

[several 14]

$s(n,x,y)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}m(r,x,y)\exp (-r^{\′}\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(11\right)$

In these formulas (10), (11), r is the position of the moving direction of the workbench in the coordinate system that is fixed on the acceptor, and r ' is the position that is fixed on the movable workbench direction in the device rest frame on the whole,

[several 15]

r′＝r-r _table(n)(5)

And, r _Table(n) be the amount of movement of the workbench of the n time magnetic resonance signal when obtaining.In addition, k (n) with by the n time to pass through the phase place rotation that magnetic resonance signal that slip phase code leaning magnetic field produces accepts corresponding, former formula (7) definition, with its only on two-dimensional directional expression same with chart shown in Figure 9.Function w _n(r ') be the function that obtains by the measuring device performance data.

(n, kx ky) as shown in figure 13, are stored in the instrumentation memorizer 401 the signal S of instrumentation, and (ky) (n, x y) are stored in the intermediate store 402 the signal s after layer direction (x direction) and read direction (y direction) carry out Fourier transformation for n, kx with S.

In the case, this signal s (n, x y) are checking a series of phase code of carrying out on the diverse location of object from-π to π, thus can't by formula (11) by fourier transform method solve m (r, x, y).Therefore, with the distribution of magnetization m ' of supposition (r, x y) set as parameter, use m ' (r, x, y), through type (11) calculate and try to achieve magnetic resonance signal s ' (n, x, y).And so that the magnetic resonance signal s ' that tries to achieve by calculating (n, x, y) with the magnetic resonance signal s of practical measurement (n, x, the secondary power of the absolute value of difference y) with constitute minimum mode, (r, x y), carry out image thus and reconstruct to try to achieve m.In the present embodiment, (r, x y), can use null value, also can utilize in advance and carry out the positioning image of instrumentation with low spatial resolution to checking object as the distribution of magnetization m ' that supposes.

The 3D rendering data storage that obtains as the layer image of the section of stipulating, is implemented the Flame Image Process and the demonstration of projection or volume drawing (volume rendering) etc. in addition as required in image storage 403.

According to present embodiment, the not only planar visual field enlarges, and also can enlarge as the visual field of volume.If the method that enlarges with the planar visual field obtains volume, then need the reciprocal several of workbench, efficient is low, and is also uncomfortable for the patient, but with the 3D photography, movable workbench is once finished photography, can be effectively and the volume of photographing apace.

And, same with second embodiment in the present embodiment, can change moving speed of table as required.In addition, also can be same with the 3rd embodiment, workbench is moved back and forth, for example in acquisition device performance data on the road, instrumentation is checked the data of object on multiple road.

The 5th embodiment

In the above embodiment, during the acquisition device performance data, be illustrated being independent of the situation that this photography photographs, but obtaining of equipment energy characteristic data can be carried out simultaneously with this photography.Below, as the 5th embodiment of the present invention,, the method that obtains of carrying out the equipment energy characteristic data simultaneously with this photography is described with reference to Figure 14 and Figure 15.

In the present embodiment, the structure of device is identical with described first embodiment.But in the present embodiment, the order of photography is shown in Figure 14 (a), in initial step, carry out obtaining and this photography (625) of equipment energy characteristic data simultaneously, in following step, operative installations performance data and inspection object data calculate (626) to the image that reconstructs of checking object.

The low strap data that obtain in the time of the equipment energy characteristic data by only utilize frequency field in this photography realize.That is, only stay the low strap in the SPE data that in this photography, obtain, and utilize Fourier transformation, the low-pass pictures that the acquisition device data are used.At this moment, under the zone that can obtain signal is not in situation in the subFOV, get the low strap data thick and fast, and expansion FOV.For example, shown in Figure 14 (b), this travelling table similarly of photographing of this photography and first embodiment, photograph simultaneously (627,628), and only slip phase code step of low strap is increased by 0.5 (629).

Plant the SPE data that photography obtains thus, stay the low strap data of intensive instrumentation, and at first carry out initial point correction (Figure 15, step 641).This photography is because photograph in the travelling table position, so in each signal is obtained, the origin position difference.The origin position difference means that the deviant of leaning magnetic field staggers.The correction of origin position is the correction that staggering of the deviant of this kind leaning magnetic field revised, by signal being applied exp (r _Table(n) k (n) (1+d (r '))), can revise.That is, carry out the processing of following formula (13).

[several 16]

$S(n,k_y)\×\exp (-r_{\mathrm{table}}\left(n\right)k\left(n\right)(1+d\left(r^{\′}\right)))$

$={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}M(r,k_y)\exp (-\mathrm{rk}\left(n\right)(1+d\left(r^{\′}\right)))w_n\left(r^{\′}\right)\mathrm{dr}---\left(13\right)$

In following formula (13), comprise nonlinear of leaning magnetic field, but, also can apply exp (r signal ignoring under the nonlinear situation of leaning magnetic field _Table(n) signal k (n)).The processing of this situation is represented as shown in the formula (14).

[several 17]

$S(n,k_y)\×\exp (-r_{\mathrm{table}}\left(n\right)k\left(n\right))$

$\≈{\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}M(r,k_y)\exp (-\mathrm{rk}\left(n\right))w_n\left(r^{\′}\right)\mathrm{dr}---\left(14\right)$

After origin position revised, as shown in figure 15, be zero, fill up k-space, thereby make the k-space data (step 642) that a low-pass pictures is used by carrying out the high-band data are filled out.By these k-space data are carried out Fourier transformation, can obtain the low-pass pictures (step 643) at an operating position place.And, in the slip phase code of the enterprising line phase coding of movable workbench direction, because obtain for each data, the FOV difference reconstructs so can not utilize Fourier transformation to carry out image usually, but is only using under the low strap data conditions, because operating position is with low uncertainty, FOV not too changes, so as long as carry out the correction of the origin position of each data, can carry out image by Fourier transformation approx and reconstruct.

This low-pass pictures can obtain by a circulation of slip phase code, uses the low-pass pictures data of each position, can with first embodiment generating apparatus performance data similarly.Promptly, can access the equipment energy characteristic data by with the even view data of each low-pass pictures data divided by total FOV.By the equipment energy characteristic data that obtain in each position,, generate equipment energy characteristic data (644) as a whole by carrying out interpolation.

And the interval of position that can the acquisition device performance data is determined by the period of slip phase encoder.At interval narrow more, promptly install each image that performance data obtains usefulness to obtain the position close more, evenly the interpolation of the generation of image or equipment energy characteristic data is correct more.In the present embodiment, can be by the moving speed of table that slows down, or make the slip phase code step sparse, and increase the circulation of slip phase code as illustrated in fig. 16, the interval of obtaining the position is narrowed down.

In addition, 0.5 situation that the slip phase code of the low strap step increased is illustrated, but in the case, increases because signal is obtained number of times, so the photography time of this photography increases.Be the increase of the photography time that suppresses this photography, as shown in figure 17, can make signal obtain number of times and reduce by in high-band, for example increasing by two slip phase codes steps.Figure 16 (b) represents the variation of this kind slip phase code amount, and Figure 18 represents the SPE data that obtain with the photography based on this kind slip phase code step.

It is identical with first embodiment to use the equipment energy characteristic data so obtain and the view data that obtains simultaneously to carry out the reconstituted computing method of image.

According to present embodiment, do not need to be independent of this photography, and be used for the photography of acquisition device performance data, so can shorten photography time as a whole.

The 6th embodiment

And in the above embodiment, the situation that receiving coil is fixed on the device is illustrated, but also can be applicable to situation about being fixed on the acceptor.At first,, use is fixed on coil on the acceptor, and the method for carrying out this photography in advance after the acquisition device performance data describes as the 6th embodiment.

In the present embodiment, before this photography 602, carry out equipment energy characteristic instrumentation 601, the operative installations performance data is carried out image and is reconstructed 603 identical with first embodiment shown in Fig. 4 (a).But in the present embodiment, as shown in figure 19, because coil 114 is fixed on the acceptor 103, move so follow moving of acceptor (workbench 301), for total FOV is photographed, a plurality of coils are used alternatingly.Be used alternatingly under the situation of a plurality of coils, also can using a plurality of coils to receive simultaneously.

Plant thus signal that photography obtains for difference by the signal that each coil obtains, append the dimension suitable, and carry out the image that is suitable for formula (8) and reconstruct with the coil sequence number.For example, (n, ky c) represent with following formula (15) to obtain signal S by the C coil.

[several 18]

$S(n,k_y,c)={\∫}_{r=0}^{{\mathrm{FOV}}_{\mathrm{total}}}M(r,k_y)\exp (-r^{\′}k\left(n\right)(1+d\left(r^{\′}\right)))w_{n,c}\left(r^{\′}\right)\mathrm{dr}---\left(15\right)$

Herein, because the dimension of expression coil sequence number c and the dimension of signal sequence number n are cooperated, can be as n * c signal processing, so can use formula (3), (4) and (8) to carry out the reconstituted calculating of image.That is, to n, c carries out formula (8) summation as shown in the formula (16).

[several 19]

σ ²＝∑ _n，c|s(n，y，c)-s′(n，y，c)| ² (16)

On the other hand, for the equipment energy characteristic data obtain 601, ask the equipment energy characteristic data w shown in the formula (15) by coil _{N, c}(r ').At first to the C coil, the equipment energy characteristic data conditions that obtains about the signal that received by this coil is described.

Optimum is to set station as illustrated in fig. 20, so that magnetostatic field distributes, irradiation covers the sensitivity zone of receiving coil by the one or many photography in the zone all uniformly with the activation profile of coil.Stay uniform zone and engage from this photography result, can make the image of magnetostatic field sensitivity regional integration of the receiving coil when even thus with irradiation.In example shown in Figure 20, magnetostatic field and the image 1602a that shines homogeneous area in image 1601b by the magnetostatic field in the image 1601 of synthetic first station and irradiation homogeneous area and the image 1602 of second station obtain the image 1603 of the sensitivity regional integration of receiving coil.With the even image 1600 that the image of this sensitivity distribution of expression is made divided by common use multistation Photographic technique, the sensitivity that can access the c coil distributes.

＜image 1603〉image 1600 of ÷＜evenly 〉=sensitivity of＜the c coil distributes 〉

Next, divided by image 1603, can access remaining equipment energy characteristic, i.e. inhomogeneous, the irradiation coil activation profile of magnetostatic field by the image that will obtain by the c coil.

In the example of Figure 20, the image 1601 that will obtain at station 1, obtain 1602 respectively divided by composograph 1603 at station 2, obtain sensitivity in station 1, the station 2 equipment energy characteristic data beyond distributing thus.

＜image 1601〉÷＜image 1603 〉=＜equipment energy characteristic of station 1 〉

＜image 1602〉÷＜image 1603 〉=＜equipment energy characteristic of station 2 〉

Equipment energy characteristic data w for the c coil _{N, c}(r ') can by the receiving coil sensitivity is distributed, magnetostatic field is inhomogeneous, irradiation coil activation profile multiplies each other acquisition.

Coil for other also carries out same processing, for all coils, obtains the equipment energy characteristic data w that comprises that sensitivity distributes _{N, c}(r ').

After the equipment energy characteristic data obtain, obtain the step and the operative installations performance data of the data 605 of checking object and check object data, to checking reconstructing the step that image 606 calculates and similarly to carry out with aforesaid first embodiment of object.In the case, can carry out interpolation, also can when image reconstructs, use the equipment energy characteristic data of hithermost position the equipment energy characteristic data that obtain by each position.

The 7th embodiment

Next as the 7th embodiment, use is fixed on coil on the acceptor, and describes with the method that obtains that the equipment energy characteristic data are carried out in this photography simultaneously.In the case, carry out the photography same with the 5th embodiment, and in the obtaining of equipment energy characteristic data, as the 6th embodiment, distinguish each coil, (n, ky c) consider the signal that will be obtained by the c coil as S.

At first, in the present embodiment, the structure of device is identical with the 6th above-mentioned embodiment.The order of photography is shown in Figure 14 as the 5th embodiment, in step 625, side by side carry out obtaining and this photography of equipment energy characteristic data, in step 626, operative installations performance data 604 and inspection object data 605 calculate the image 606 that reconstructs of checking object.

Obtain in the present embodiment in the time of the equipment energy characteristic data, only utilize the low strap data of frequency field, and carry out the correction of the origin position of each data, and carry out approx reconstructing based on the image of Fourier transformation, this is identical with the 5th embodiment.But, same with the 6th embodiment in the present embodiment, to each coil acquisition device performance data.

At first, be conceived to the c coil, consideration obtains the equipment energy characteristic data conditions about the signal that is received by this coil.

Optimum is to set the low strap data as illustrated in fig. 20 and obtain the position, so that magnetostatic field distributes, irradiation covers the sensitivity zone of receiving coil by the one or many photography in the zone all uniformly with the activation profile of coil.Promptly, Figure 20 represents the coil position in the multistation, but as shown in figure 15, carry out the slip phase code step in the time of travelling table (being coil), so that set the center (position when obtaining low frequency component) of first circulation (from-π to π) of the slip phase code under the slip phase code situation in step is first camera positions of Figure 20, and the second circulation center (position when obtaining low frequency component) be second camera positions of Figure 20.Staying the low strap data from the SPE data, thereby to reconstruct the method for an image identical with the 5th embodiment, herein, from the image that utilizes first circulation and second circulation to obtain, stay the low strap data respectively, carry out the initial point correction, it is zero that the high-band data are filled out, and carries out Fourier transformation, thereby reconstructs image.

Next, by reconstituted each image making uniform image like this.Evenly image can engage each image, also can only stay and use uniform part, also can obtain by the multistation photography in advance.

From the image of each coil of so obtaining and the even image of generation, similarly obtain equipment energy characteristic with the 6th embodiment.That is, at first to the c coil, by carrying out synthetic image to the image of respectively obtaining the position divided by the uniform distribution image, the sensitivity that obtains the c coil distributes.Next, for the c coil, with the image of respectively obtaining the position divided by the image that will respectively obtain the position image after synthetic, thus, respectively obtained sensitivity in the position equipment energy characteristic beyond distributing.

＜image 1603〉image 1600 of ÷＜evenly 〉=sensitivity of＜the c coil distributes 〉

＜image 1601〉image 1603 of the influence that distributes of ÷＜only comprise sensitivity 〉=＜obtain the equipment energy characteristic of position 1 〉

＜image 1602〉image 1603 of the influence that distributes of ÷＜only comprise sensitivity 〉=＜obtain the equipment energy characteristic of position 2 〉

The sensitivity that so obtains distributes, magnetostatic field is inhomogeneous by making, the activation profile of irradiation coil multiplies each other, and obtains whole equipment energy characteristic data.In the case, can also can when reconstructing, image use the nearest equipment energy characteristic data that obtain the position to carrying out interpolation respectively obtaining the equipment energy characteristic data that the position obtains.

With above-mentioned embodiment similarly, the signal that signal that is obtained by this photography and operative installations performance data are calculated reconstructs image.

Embodiment

For confirming effect of the present invention, use inspection object as shown in figure 21, the comparative experiments of carrying out travelling table photography in the past and photographing based on the travelling table of first embodiment and the 5th embodiment.Among Figure 21, the two dimensional image of object is checked in the figure of downside (b) expression, and the figure of upside (a) is with the one-dimensional profile of its image projection in the r axle.The r axle of figure (b) and y axle are locative axles, and scale is 1 for making Pixel Dimensions.In addition, the longitudinal axis of the profile shown in the figure (a) is represented pixel value.Checking on the object to have a plurality of slits.Left end is a pixel with the gap width of central authorities, is arranged with the slit that width enlarges a pixel gradually on right side separately.Among the figure (b), the zone of white expression is the existence zone of checking object, has the non-existent zone of the object of inspection therebetween.

Photographic parameter is made as sub FOV=420mm * 210mm (64 pixels * 32 pixels), totalFOV=420mm * 1260mm (64 pixels * 192 pixels).

In the described photography of first embodiment, the r direction of principal axis is made as the moving direction of workbench, and, will be made as read direction with the vertical y direction of principal axis of the moving direction of workbench in the enterprising line slip phase code of this moving direction.In addition, carry out under the condition of SNR=60, the expression signal is obtained the w of scope _n(r ') be stair-stepping function shown in Figure 1.In the photography of the 5th embodiment, the r direction of principal axis is made as the movable workbench direction, and in the enterprising line slip phase code of this direction, and will be made as read direction with the vertical y direction of principal axis of the moving direction of workbench.In addition, under condition, carry out at SNR=50.

In the photography of in the past travelling carriage, the r direction of principal axis is made as the moving direction of workbench, and this direction is made as read direction, be made as the slip phase-encoding direction with the vertical y direction of principal axis of the moving direction of workbench.

Figure 22 represents to reconstruct image with what in the past travelling table method obtained, and Figure 23 represents to utilize the image that reconstructs that first embodiment obtains, and Figure 24 represents to utilize the image that reconstructs that the 5th embodiment obtains.The scale of Figure 22～Figure 24 is identical with Figure 21, so that pixel size is 1.From these images relatively as can be known, the slit that each can both a pixel of resolution width has enough resolution.In addition, the SNR of first embodiment is 60, and is identical with in the past method.So as can be known, utilize present embodiment, keep the image quality same with previous methods, and the photography that can broaden one's vision.In addition, for other embodiment, obtain same result.

On the other hand, for photography time, as shown in figure 25, if the photography time of the photography time 501 of travelling table Photographic technique in the past during with the sub FOV=40cm of movable workbench direction is made as 1, then follow narrowing down of sub FOV, time lengthening, in contrast, in the present embodiment, corresponding with dwindling of sub FOV, slip phase code number with respect to sub FOV reduces, so photography time 502 is constant.

In addition,, utilize method of the present invention, can in the fewer time, obtain proximate equipment energy characteristic data for the time of obtaining of equipment energy characteristic data.Under the situation of special acquisition device performance data at the same time, whole photography time does not increase yet.Under the situation of acquisition device performance data in advance, unnecessary cost has taken place in the discrepancy of workbench and photography time, but to the obtaining of equipment energy characteristic data, does not need the image of high-resolution, so photography is finished at short notice.

Particularly, as typical example, if consider that carrying out 1000 times signal with this photography obtains, then for obtaining tight equipment energy characteristic, the meter side of equipment energy characteristic data only needs the signal of this photography to obtain the numerical value of number of times, and the whole time of photography becomes 1001 times of this photography.In contrast, in the method by multistation acquisition device performance data of the present invention, whole photography time in the method for acquisition device characteristic is one times, i.e. the photography time of this photography at the same time below twice.

Industrial utilizability

According to the present invention, even on the movable workbench direction, signal is obtained in the narrow situation in zone, The travelling table photography can not take place to carry out in photography time with prolonging. Can on the movable workbench direction In the regional narrow device of photography, still can carry out at high speed the whole body photography.

Claims (13)

1. magnetic resonance imaging apparatus, it possesses:

High frequency magnetic field produces mechanism, and its generation puts on and is placed on the high frequency magnetic field that produces the inspection object in the photographing space that magnetostatic field is arranged;

Leaning magnetic field produces mechanism, and its generation puts on the leaning magnetic field of described inspection object;

Travel mechanism movably, it carries described inspection object;

Receiving mechanism, it receives the magnetic resonance signal that produces from described inspection object;

Image reconstructs mechanism, and it reconstructs the image of described inspection object based on the described magnetic resonance signal that receives;

Controlling organization, the action of its described each mechanism of control;

Indication mechanism, it shows reconstituted described image,

Described magnetic resonance imaging apparatus is characterised in that,

Described controlling organization is repeatedly to receive described magnetic resonance signal in the moving of described travel mechanism, and by each reception, change the mode of applied amount of leaning magnetic field of the moving direction of described travel mechanism, control described leaning magnetic field and produce mechanism and described receiving mechanism

Described image reconstructs mechanism so that signal that receives and secondary power and mode minimum by the absolute value of the difference of the signal that calculates as the distribution of magnetization of parameter setting are determined the distribution of magnetization greater than the described inspection object in the visual field of described photographing space.

2. magnetic resonance imaging apparatus as claimed in claim 1 is characterized in that,

The relation and the equipment energy characteristic data of the leaning magnetic field intensity of the position of the described travel mechanism when described image reconstructs mechanism's use signal acquisition, the position of described travel mechanism and moving direction calculate the signal that calculates by as the distribution of magnetization of parameter setting.

3. magnetic resonance imaging apparatus as claimed in claim 1 or 2 is characterized in that,

Described controlling organization makes described travel mechanism at the uniform velocity mobile when the reception of described magnetic resonance signal.

4. as each described magnetic resonance imaging apparatus in the claim 1～3, it is characterized in that,

Described controlling organization moves back and forth described travel mechanism, and reconstructs required equipment energy characteristic data by any the acquisition image in road or multiple road.

5. as each described magnetic resonance imaging apparatus in the claim 1～4, it is characterized in that,

Described controlling organization is controlled described leaning magnetic field and is produced mechanism and described receiving mechanism when the reception of described magnetic resonance signal, to apply the phase code leaning magnetic field with the moving direction different directions of described travel mechanism.

6. as each described magnetic resonance imaging apparatus in the claim 1～5, it is characterized in that,

The direction of described magnetostatic field is a vertical direction.

7. as each described magnetic resonance imaging apparatus in the claim 1～5, it is characterized in that,

The direction of described magnetostatic field is a horizontal direction.

8. magnetic resonance imaging apparatus, it possesses:

High frequency magnetic field produces mechanism, and its generation puts on and is placed on the high frequency magnetic field that produces the inspection object in the photographing space that magnetostatic field is arranged;

Leaning magnetic field produces mechanism, and its generation puts on the leaning magnetic field of described inspection object;

Travel mechanism movably, it carries described inspection object;

Receiving mechanism, it receives the NMR signal that produces from described inspection object;

Image reconstructs mechanism, and it reconstructs the image of described inspection object based on the described NMR signal that receives;

Controlling organization, the action of its described each mechanism of control;

Indication mechanism, it shows reconstituted described image,

Described magnetic resonance imaging apparatus is characterised in that,

Described controlling organization carries out the instrumentation of NMR signal that is used to try to achieve the equipment energy characteristic data as the equipment energy characteristic instrumentation; With

As the instrumentation of NMR signal of distribution of magnetization that is used to try to achieve described inspection object of this photography,

And in described photography, in the moving of described travel mechanism, repeatedly receiving described magnetic resonance signal, and receive, change the mode of applied amount of leaning magnetic field of the moving direction of described travel mechanism by each, control described leaning magnetic field and produce mechanism and described receiving mechanism

Described image reconstructs the NMR signal that mechanism uses instrumentation in described equipment energy characteristic instrumentation, calculates equipment energy characteristic, and uses this equipment energy characteristic, calculates the signal of supposition by the distribution of magnetization of supposition,

And so that in described photography secondary power and mode minimum of the absolute value of the difference of the signal of the signal of instrumentation and described supposition, determine greater than the described inspection object distribution of magnetization in the visual field of described photographing space.

9. magnetic resonance imaging apparatus as claimed in claim 8 is characterized in that,

Described controlling organization and is carried out the mode of described equipment energy characteristic instrumentation so that described travel mechanism moves in each position of described travel mechanism between a plurality of positions, control.

10. magnetic resonance imaging apparatus as claimed in claim 8 is characterized in that,

Described controlling organization carries out described equipment energy characteristic instrumentation and described photography simultaneously.

11. magnetic resonance imaging apparatus as claimed in claim 10 is characterized in that,

Described image reconstructs mechanism and will the part of the NMR signal of instrumentation use in the NMR signal that is used for trying to achieve described equipment energy characteristic in described photography.

12. as each described magnetic resonance imaging apparatus in the claim 8～12, it is characterized in that,

Described receiving mechanism possesses the receiving coil that is fixed on the device,

Described image reconstructs the signal that mechanism uses the receiving coil be fixed on the device to receive, and in described photography, calculates the equipment energy characteristic in each the travel mechanism position when NMR signal carried out instrumentation.

13. as each described magnetic resonance imaging apparatus in the claim 8～12, it is characterized in that,

Described receiving mechanism possesses the receiving coil that is fixed on the inspection object,

Described image reconstructs mechanism and uses and to be fixed on the signal that the receiving coil checked on the object receives, and in described photography, calculates the equipment energy characteristic in each the travel mechanism position when NMR signal carried out instrumentation.

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