CN102370484B - Magnetic resonance imaging device and magnetic resonance imaging method - Google Patents
Magnetic resonance imaging device and magnetic resonance imaging method Download PDFInfo
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Abstract
The invention provides a magnetic resonance imaging device capable of collecting and correctly describing the images of fluid and a magnetic resonance imaging method; wherein, the magnetic resonance imaging device involved with the implementation way of the invention possesses a collecting part and a generating part. The collecting part is used to shoot the fluid in a tested object and collect a plurality of images having different photography pulse sequence parameters, and the generating part is used to select the pixel values of positions in at least one image of the plurality of images, and uses the selected pixel values of the positions to generate mixed images.
Description
The cross reference of related application
The U.S. Patent application formerly 12/861 that the application submitted to based on August 23rd, 2010, the Japanese patent application No.2011-158397 formerly that on July 19th, 254 and 2011 submits to also requires its priority, and its full content is by reference in conjunction with in this application.
Technical field
Embodiments of the present invention relate to MR imaging apparatus and MR imaging method.
Background technology
In the past, as one of nuclear magnetic resonance, there is the method that does not use the fluid in contrast agent shooting subject.
Prior art document:
Patent documentation 1: No. 2009/0261825 description of U.S. Patent Application Publication
Patent documentation 2: No. 6801800 description of United States Patent (USP)
Patent documentation 3: TOHKEMY 2003-70766 communique
Patent documentation 4: TOHKEMY 2004-329614 communique
Non-patent literature 1:Fan, et al., " 3D Noncontrast MR Angiography of the Distal Lower Extremities Using Flow-Sensitive Dephasing (FSD)-Prepared Balanced SSFP; " Magnetic Resonance in Medicine, volume62, pages1523-1532 (2009)
Non-patent literature 2:Fan, et al., " 3D Non-Contrast-Enhanced MRA Using Flow-Sensitive Dephasing (FSD) Prepared Balanced SSFP:Identification of the Optimal First-Order Gradient Moment; " page1410,17th Annual Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine, Stockholm, Sweden, (May2-5,2010)
Non-patent literature 3:Fan, et al., " Carotid Arterial Wall MRI at 3T Using 3D Variable-Flip-Angle Turbo Spin-Echo (TSE) with Flow-Sensitive Dephasing (FSD); " Journal of Magnetic Resonance Imaging, volume31, pages645-654 (2010)
Non-patent literature 4:Fan, et al., " Non-Contrast-Enhanced Hand MRA Using Multi-directional Flow-Sensitive Dephasing; " page40517th Annual Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine, Stockholm, Sweden, (May2-5,2010)
Non-patent literature 5:Guo, et al., " 3D Non-Contrast MRA of Lower Extremities Using Balanced SSFP with Flow-Sensitive Dephasing (FSD) at 3T; " page3786,17th Annual Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine, Stockholm, Sweden, (May2-5,2010)
Non-patent literature 6:Haacke, et al., " Magnetic Resonance Imaging:Physical Principles and Sequence Design, " New York:Wiley-Liss, Chapter23, pages673-675 (1999)
Non-patent literature 7:Miyazaki, et al., " Peripheral MR Angiography:Separation of Arteries from Veins with Flow-spoiled Gradient Pulses in Electrocardiography-triggered Three-dimensional Half-Fourier Fast Spin-Echo Imaging; " Radiology, volume227, pages890-896 (June2003)
Non-patent literature 8:Wang, et al., " Improved Suppression of Plaque-Mimicking Artifacts in Black-Blood Carotid Atherosclerosis imaging Using a Multislice Motion-Sensitized Driven-Equilibrium (MSDE) Turbo Spin-Echo (TSE) Sequence; " Magnetic Resonance in Medicine, Vol.58, pages973-981 (2007)
Non-patent literature 9:Haacke, et al., " Magnetic Resonance Imaging:Physical Principles and Sequence Design, " New York:Wiley-Liss, chapter 23, pages 673-675 (1999)
Summary of the invention
But, according to previous methods, for example, exist and produce the pollution (contamination) that causes of vein etc., may not collect the situation of appropriate image.
The MR imaging apparatus that embodiment relates to possesses collection unit and generating unit.Fluid in above-mentioned collection unit shooting subject, collects the different multiple images of parameter (parameter) of camera pulse (pulse) sequence (sequence).In above-mentioned generating unit at least one image from above-mentioned multiple images, select the pixel value of the each position in image, use the pixel value of selected each position to generate mixing (hybrid) image.
Realization can be collected the effect of the image of depicting rightly fluid.
Accompanying drawing explanation
Fig. 1 is for by for example using, based at multiple images (, use the dim tremulous pulse image (DA (Dark Artery) image) of obtaining in different camera parameter (parameter of camera pulse sequence)) vision-mix (for example, mix DA image), collect and process the height summary frame (block) of MRI (the Magnetic Resonance Imaging) system (system) of the data (data) of magnetic resonance blood vessel shooting (MRA (Magnetic Resonance Angiography)) and scheme.
Fig. 2 utilizes to follow not to be 0 a leaning magnetic field moment (moment) FSD (Flow-Spoiled Dephasing) prepulsing (pre-pulse) (m1), makes the skeleton diagram of the typical MRI data collection pulse train that spin (spin) phase place flowing disperses in continuous MRI data collection pulse train.
The figure of the result of FSD MRA when Fig. 3 A adjusts to the very low DA of collection image for expression by a leaning magnetic field moment (m1).
The figure of the result of FSD MRA when Fig. 3 B adjusts to the very high DA of collection image for expression by a leaning magnetic field moment (m1).
Fig. 4 is for different leaning magnetic field moment values (m1 value), and the MRI signal response of the standard producing according to the blood flow that flows fast tremulous pulse, flow in slow tremulous pulse and vein is carried out to the curve chart shown in normalization.
Fig. 5 is the skeleton diagram for obtain the typical composition algorithm (algorithm) of vision-mix by synthetic multiple DA images with different parameters collection.
Fig. 6 is the detailed figure that represents typical composition algorithm.
Fig. 7 is the MRA image of emphasizing arterial signal.
Fig. 8 A is the figure that represents vision-mix.
Fig. 8 B represents to use the figure central or image that a middle leaning magnetic field moment values (m1 value) obtains.
Fig. 9 A is the figure of the improvement shown in being illustrated in when MRA image is in the past used to vision-mix.
Fig. 9 B is the figure of the improvement shown in while representing MRA image in the past to use vision-mix.
Figure 10 is the summary flow chart (flow chart) illustrating together with typical computer (computer) program (program) coding (code) tectosome that can utilize in typical embodiment and the operator's (operator) who prepares as operation (option) input.
Symbol description
10: pallet; 11: bed; 12: magnetostatic field B0 Magnet; 14:Gx, Gy, Gz gradient magnetic field coil group; 16:RF coil block; 18: shooting space; 20: System Forming Elements; 22:MRI system controller; 24: display; 26: keyboard; 28: printer; 30:MRI sequence controller; 32:Gx, Gy, Gz gradient magnetic field coil driver; 34:RF transmitter; 36: send receiving key; 38: program coding tectosome; 40:RF receptor; 42:MRI data processor; 44: vision-mix reconstruction algorithm code construction body; 46:MRA image storage; 50:MRI system program storage device.
The specific embodiment
MRI system shown in Fig. 1 comprises pallet portion 10 (illustrating in summary tangent plane) and the multiple relevant System Forming Elements 20 connecting to pallet portion 10.The indoor pallet portion 10 that at least arranges of covering.MRI system shown in Fig. 1 comprises in fact coaxial circles tubular magnetostatic field B0 Magnet 12, Gx, Gy and Gz gradient magnetic field coil group (set) 14, RF coil (coil) assembly (assembly) 16.The trunnion axis of the cylindric arrangement forming along these elements, has the shooting space 18 of the head that comprises in fact the patient 9 who is supported by bed 11.
MRI system controller 22 possesses the input/output port being connected with display (display) 24, with keyboard (keyboard) 26 and printer (printer) 28.Display 24 can be also the touch screen (touch-screen) of the input that can also control.
MRI system controller (controller) 22 is connected with the MRI sequence controller 30 of also controlling Gx, Gy and Gz gradient magnetic field coil driver (driver) 32 except controlling RF transmitter (transmitter) 34 and transmission receiving key (switch) 36 (while using same RF coil to sending and receive both sides).MRI sequence controller 30, for by the FSD (Flow-Spoiled Dephasing) with different leaning magnetic field moment values (m1 value) for example, is made to obtain pulse train (camera pulse sequence, pulse train) for realizing MRA data with available other (in the past) MRI pulse train combinations, comprises appropriate program coding tectosome 38.
Fig. 1 also shows from the several data processing element of MRI system and can access, and the summary of the MRI system program storage device 50 of storage in the Protector of computer-reader form (for example, relevant with reconstruction or the input of operator to this image reconstruction etc. of the vision-mix of non-contrast agent MRA) program coding tectosome.Program storage device 50 is divisible, at least a portion (is being stored in public place, directly be not connected with MRI system controller 22) within the process computer of System Forming Elements 20, can directly be connected with other computers of this program coding tectosome that needs immediately storing in common processing.
In fact, Fig. 1 to describe be to the unusual figure of typical MRI system of height simplification, can implement the figure after the mode of typical embodiment described later changes in addition.System Forming Elements can be divided into the different logical collection of " frame (box) (each element) ", and, generally form by rising to multiple digital information processor (DSP (Digital Signal Processors)), microprocessor (microprocessor), dedicated processes circuit (high-speed a/d conversion, high speed Fourier (Fourier) conversion, arrange process etc.).These processors are respectively " state machine (machine that state moves) " that clock (clock) is set, and its physical data treatment circuit within each clock cycle (or in each clock cycle of specified quantity) advances to another physical state from a certain physical state.
Treatment circuit (for example, CPU (Central Processing Unit), depositor (register), buffer (buffer), arithmetic unit etc.) physical state among processing is carried out, gradually change by each clock cycle, the physical state of corresponding data storage medium (for example, the bit storage position of magnetic storage medium) in system works from a certain state to another state transitions.For example, in the time that the process of reconstruction (process) of mixing MRA imaging finishes, from previous state (be for example located at the arrangement of the data value storage position that can get involved with computer-reader form in physical storage medium, all become in the same manner " 0 " value or " 1 " value), to the new state transitions for example, changing between minima and maximum so that the physical state of physical location that makes to arrange represents real physical phenomenon and situation (, the tremulous pulse of the patient in shooting space).This arrangement of the data value of storage is with to arrange by particular order the specific tectosome that the computer-controlled program of changing compute mode and make it to move in MRI system encodes in the time being written into successively (load) by command register and being carried out by more than 1 CPU of MRI system the same, shows and forms a certain physique body.
In typical embodiment shown below, the method after collection or MRA (the Magnetic Resonance Angiography) generation of image and the improvement of demonstration of carrying out data is shown.
In non-radiography magnetic resonance blood vessel shooting (MRA) method, do not use exogen contrast agent, just generate the MR image of arterial-venous angioarchitecture.In typical embodiment shown below, for example, to avoid pollution that vein causes (, overlapping the causing of tremulous pulse and vein is difficult to observe image), generating raising tremulous pulse is object with respect to non-radiography MRA image or contrary (, the generating the non-radiography MRA image of emphasizing vein) of the contrast (contrast) of background.
Various Flow-dephasing leaning magnetic field moments in heart beat cycle (for example, a leaning magnetic field moment) or time phase (for example, (or its contrary tremulous pulse cause) pollution irreducible minimum that the time delay (for example, the peak of R ripple (peak) value is to the time delay of signal collection) of heart beat cycle (cycle) or the view data of being collected by its both sides N set makes that vein causes while (or its contrary vein) maximized hybrid reconstruction algorithm of signal of tremulous pulse is synthesized.This processing can by user's (user) input constraint be irreducible minimum and automatically or semi-automatically carrying out.Substantially do not need correction (calibration) shooting for obtaining desirable or optimised parameter.
In non-radiography MRA method in the past, generally substantially obtain two such view data of the image (BA (Bright Artery) image, i.e. the bright image of arteriovenous) of tremulous pulse bright (signal value is high) and the image of tremulous pulse dimness (signal value is low) (DA (Dark Artery) image, i.e. the image of the bright tremulous pulse dimness of vein).By from BA view data (to each pixel (pixel)) deduct (subtracting shadow (subtraction)) DA view data, generate MRA image I.
I=BA-DA (formula 1)
Final subtraction image I only comprises the signal from the pixel of tremulous pulse idealizedly.The subtraction image data that as a result of obtain generally use maximum intensity projection (MIP (Maximum Intensity Projection)) form (format) to show, and make patient's health 3-D view.
The non-radiography MRA method that is called as FSD (Flow-spoiled Dephasin) use there is a leaning magnetic field moment (m1) that is not 0 leaning magnetic field prepulsing module (, the MRI of diagnosis use obtains the initial part in pulse train, for example, with reference to Fig. 2), make the spin phase place that flows disperse (dephasing (dephase)) thus obtain DA image (image of tremulous pulse dimness).
In the time that zero (zero) the inferior leaning magnetic field moment of 0 (null set) is combined with a heeling moment that is not 0, mobile spin phase place is disperseed, but does not affect static (background) spin.Vector (vector) direction of a leaning magnetic field moment (dephasing pulse (leaning magnetic field prepulsing) apply direction) can be used any or the simultaneous leaning magnetic field moment in the passage (channel) (x, y, z) of leaning magnetic field to operate.Like this, leaning magnetic field moment can be designed to Alongvector and optionally disperses spin.The signal of that phase place is disperseed, mobile spin is decayed in view data.The intensity of the degree of signal attenuation and a leaning magnetic field moment and not forming straight line property of flow velocity and proportional (Fig. 4).Tremulous pulse generally larger than vein flow velocity, be subject to the impact of the tremulous pulse that heart beat cycle produces stronger.Therefore, think that the signal attenuation of tremulous pulse is larger than vein, think that this decay meeting further becomes large in the systole of heart.
Read (readout) that FSD prepulsing module (module) can be attached to any MRI diagnosis in the past always existing scans (scan) sequence (for example, bSSFP (Balanced Steady-State Free Precession), FASE (Fast Asymmetric Spin Echo Fast Advanced Spin Echo again) etc.).It is the three-dimensional data being configured on thin tangent plane in order to use sufficient resolution to describe little vascular system that the data of generally reading obtain.Generally speaking FSD prepulsing module is the combination of 90 °-180 °-90 ° of bipolar (bipolar) leaning magnetic field and RF pulses.In the shooting of DA image, a general leaning magnetic field moment (m1) is set to the arbitrary numerical value beyond controlled 0.In the shooting of BA image, a general leaning magnetic field moment (m1) is set to little numerical value or 0.
At this, illustrate FSD, but disclosed method can be equally applicable to the MRI camera method for depict fluid at non-radiography based on subtraction.The method for example comprises FBI described herein (Fresh Blood Imaging) or the same non-radiography MRA method (cerebrospinal fluid (comprising CSF (Cerebral Spinal Fluid)) of different names.FS-FBI (Flow-Spoiled FBI) is elaborated, FS-FBI is the technology after FBI is improved, by using dephasing pulse (flow-spoiled dephasing pulse) rather than the prepulsing as FSD in echo train (echo train), for example, compare the signal value of the signal reduction arterial signal of vein.These non-radiography MRI methods generally have the synchronous or synchronous such common ground of PPG (Photo plethysmo graph) of use ECG (Electrocardiogram), have with based on T
1emphasize the MRA method of radiography in the past or non-radiography MRA method (for example, TOF (Time Of Flight) the contrast ground use T of camera method
2emphasize this common ground of image capture method.Non-radiography T
2emphasize that image capture method is in order to shorten camera time, although be not required, but still (Fast Spin Echo) pulse train is carried out to use FSE time and again.
Fig. 2 is the figure that the FSD pulse train that comprises 90 ° of-180 ° of-90 ° of RF prepulsing modules is roughly shown.For the repeatedly shooting of DA image, (as shown in the figure) comprises a leaning magnetic field moment (m1), but also not identical according to its intensity of difference of the DA view data obtaining.For the shooting of BA image, a leaning magnetic field moment (m1) is set as to 0.
In the past, obtained following two kinds of images.
When m1=0, the image (BA) that the tremulous pulse of cardiac dilatation phase is bright
M1 ≠ 0 o'clock, the image (DA) of the tremulous pulse dimness of paradoxical expansion
Then, from BA image, each pixel is deducted to DA image and generate final MRA image.As mentioned above, this is same with the FBI (Fresh Blood Imaging) of non-radiography MRA method.
Regrettably, in FSD in the past, one time leaning magnetic field moment prepulsing module spins to all mobile MR, produces phase shift to a certain degree.The decay of obtained MRI signal and the not forming straight line property of speed of nuclear spin and proportional (Fig. 4).Signal attenuation along with flow faster increase.In the time that a leaning magnetic field moment (m1) is too small, particularly, in mobile slow tremulous pulse, tremulous pulse is not fully decayed in DA image.Therefore, need to from final BA-DA subtraction image, deduct these pixel values (for example,, in Fig. 3 A, showing the maximum intensity projection (MIP) of the too small subtraction image of a leaning magnetic field moment (m1)).Equally, in the time that a leaning magnetic field moment (m1) is excessive, in the mobile situation about also decaying of DA image medium-sized vein (for example exist, in Fig. 3 B, show the maximum intensity projection (MIP) in the excessive subtraction image of a leaning magnetic field moment (m1)).The decay of vein produces the pollution (with reference to the arrow in Fig. 3 A and Fig. 3 B) on the vein location of pixels in final BA-DA subtraction image.Arterial signal a little less than representing with the arrow in Fig. 3 A, represents the pollution of vein with the arrow in Fig. 3 B.This problem particularly, in patient's peripheral vessel, becomes chaotic reason conventionally when in vein and the direct adjoining position of tremulous pulse.
Therefore, in FSD in the past, generally (a) disappears in order to prevent the too small and arterial signal of a leaning magnetic field moment (m1), (b) in order to prevent that a leaning magnetic field moment (m1) pollution excessive and that vein causes from entering produced problem, need to proofread and correct for a leaning magnetic field moment (m1) of optimal leaning magnetic field prepulsing module.The step of this correction can be by selecting 2D tangent plane, in each inspection, a Utopian leaning magnetic field moment (m1) is inferred in part shooting space.Replace, also can check based on implement FSD for representational group (cohort, statistical group) in other researchs, the group obtaining average, infers a Utopian leaning magnetic field moment (m1).This correction operation can produce unnecessary trouble, wastes the unnecessary time.Can make the wrong reason producing also increase.
The most important thing is to cause by using a single leaning magnetic field moment (m1) value, it not is the result of optimal angioarchitecture that part shooting object is depicted.In the time of each inspection, carry out the timing of a Utopian leaning magnetic field moment (m1) value, generally infer as basis take a part of blood vessel of the restriction in 2D tangent plane.In this 1 2D tangent plane, only comprise a little of 3D shooting object entirety.Even if flow velocity and pulsation also because the difference of blood vessel differs greatly, exist in a Utopian leaning magnetic field moment (m1) of therefore inferring in the method using based on this 2D tangent plane the major part of vascular structure are produced to the situation that is not best suited for result in shooting object.If a leaning magnetic field moment (m1) desirable according on average inferring of group, only has and cannot obtain the part of applicable result in vascular structure and do not produce, also cannot obtain appropriate result for each of each inspection object.
But at this, the step by according to the following stated is used vision-mix, can realization obtain (a) and strengthen the practicality FSD of the final subtraction image I that pollution that arterial signal, (b) vein cause reduces.Or also having vision-mix itself is very sufficient situation as the output image of (emphasizing tremulous pulse or vein) MRA, therefore also there is the situation that does not need final subtraction image.
For example, obtain multiple (N) data set (N >=2).Conventionally,, in the time carrying out FSD by several forms, obtain multiple set of the DA image in a different leaning magnetic field moment (m1) values.In example (Fig. 4), obtain N=3 image set (benchmark, centre, maximum).In benchmark image, m1=0 (cardiac dilatation phase), intermediate image m1=intermediate value (paradoxical expansion), maximum image m1=maximum (paradoxical expansion).The MRI signal that Fig. 4 produces the magnetic resonance blood cell core in the blood of vein, flow slow tremulous pulse and the fast tremulous pulse that flows is drawn as the function of m1.(on the position that use × symbol represents on m1 axle) obtains benchmark, centre and maximum these 3 image data sets.On signal curve, represent for the signal in selected these m1 values of type (type) of each blood vessel with circle symbol (zero).
Method shown here is used hybrid reconstruction algorithm, veneous signal is minimized and make arterial signal maximization (or on the contrary) on one side.For example, different N (N >=2) image set, can for example, by (using different Flow-dephasing moment (m1), a leaning magnetic field moment) or use time phase in different heart beat cycles (for example, time delay (for example, R crest value is to the time delay of signal collection) in heart beat cycle or obtain as the parameter of camera pulse sequence with its both sides.For example, can be by within Syst same time delay, use a different leaning magnetic field moment (m1) to be worth or use different direction vector (dephasing pulse (leaning magnetic field prepulsing) apply direction) or obtain with its both sides.And, can, by within different time delay, use same leaning magnetic field moment (m1) to get, or, different a leaning magnetic field moment (m1) value, direction vector and the combination of time delay also can be adopted.These images are by according to the known m1 corresponding with each input data set or heart beat cycle or its both sides, the relative signal deduction property of each key element being inferred, and make in the pixel of tremulous pulse, vein and background algorithm disconnected from each other thereby be input to.For example, by synthetic the pixel data of each input data set (, using selectivity location of pixels replacement algorithm), generate combination chart image set.The parameter that this mixing composition algorithm uses fixed value or the input of the selection based on user to adjust operates.In subtractive process, (for example, FSD) used combination chart image set, can generate and optimize arterial signal and veneous signal is suppressed to minimum final MRA image.Or, above-mentioned vision-mix itself can be used as the output image of MRA.
(Fig. 5) that can use the pixel data of each image set to generate combination chart image set X in the input of composition algorithm replaces the simple shadow (formula 1) that subtracts.In this composition algorithm, whether more at least two pixel data set mutually, be that the carrying out producing from tremulous pulse part, vein segment or background highly inferred to each pixel (pixel) of given image data set.The typical blended image data collection X of output, can use (in the blended image data collection) each X (x optionally obtaining one of image data set different from multiple (N), y, z) pixel value (pixel value) of position generates.Then, in common subtraction formula, use this combination chart image set X, when generating the final MRA image I after improving or designing rightly hybridization algorithm, blended image data collection itself can be used the final MRA image I after improving.
For example, can in a leaning magnetic field moment (m1) value, obtain N image data set (N >=2) as follows.
Benchmark: m1=0
Middle: m1=intermediate value
Maximum: the high value of m1=
Secondly, for with as a result of obtain 0 beyond a leaning magnetic field moment (m1) (be worth corresponding N-1, in this example, be two) data set, the pixel value that use obtains poor, the a certain pixel of inferring obtained specific image be tremulous pulse or vein, and (for example, by selectivity pixel value replacement algorithm) synthesizes blended image data collection X.Then, thus can be by using and calculate final image I blended image data collection X as DA image data set.
I (finally)=BA (tremulous pulse is bright)-X (DA mixing) (formula 2)
Fig. 5 is the general composition algorithm that shows the subtraction blended image data collection X that can generate non-radiography MRA image.Fig. 6 shows the example more specifically of the composition algorithm that generates blended image data collection X.Decision algorithm shown in use is evaluated the pixel data of assigned position (x, y, z) to all data sets (benchmark, centre, maximum), fill the value of the X (x, y, z) in blended image data collection X.
In building-up process, can there be multiple different modes.In this example of N=3 image set of employing, the process of Fig. 6 is more abundant.In order to judge that pixel is tremulous pulse or vein and use threshold parameter (ε).Hour be judged as significantly the pixel data (with reference to Fig. 4) of tremulous pulse than reference value at the pixel data of middle m1 value, therefore (x for algorithm, y, the data of the image data set of the maximum m1 value z) are filled X (x, y, z), and make this position (x, y, z) in signal maximize.In the time that the pixel data of middle m1 is similar to reference value, be judged as the pixel data of background or vein, therefore (x for algorithm, y, z) in the data of pixel data set of middle m1 value fill X (x, y,, and prevent the pollution that vein causes z).The fixed value of the measurement based on former can be freely adjusted or be selected for each anatomy tissue in the selection of threshold epsilon.For example, and (, in post processing) user also can adjust threshold epsilon alternately (interactive).In any method, the selection of threshold epsilon only affects the output after reconstruction.Owing to not affecting input data, therefore without determined the final judgement about threshold epsilon before the obtaining of data.Generate like this vision-mix X.In the generation of vision-mix X, can adopt many different hybridization algorithm/processes.If there is filling/displacement of carrying out advisably pixel, the situation that vision-mix X itself fully can be used as the output image of MRA.
Figure 10 shows the summary flow chart of the typical computer program code tectosome for realizing typical embodiment.At this, use in 100 and start to mix MRA routine, and use 102 data of calling aptly storage from storage device to obtain parameter (camera pulse sequential parameter, for example, m1 value).Also there is the situation of carrying out other required initialization procedures in this moment.
Judge 104 in, (for example,, by controlling picture/keyboard or the touch screen etc. of display) shows the options of the camera parameter pre-stored for alter operation person as required.In the time selecting, then, in operator's user interface (interface) 106, the value, the isoparametric decision/change of particular value of threshold parameter of low, the high level (level) of the quantity of the image that can obtain, m1 parameter.In the time not selecting, in step (step) 108, use the camera parameter of having stored, and use different m1 values to obtain N MRI data set.Particularly in this typical embodiment, (for example, use the parameter of each MRI parameter or heart beat cycle or its both) obtains at least one BA image and multiple DA image.
In step 110 after this, (for example, any particular algorithms as required) generates blended image data collection X, in step 112, generates and subtracts shadow MRA image.In step 114, export this image (at once or after a while from MRI system control position or as required from long-range) to storage device or display (or its both sides), then, by return to (return) thus in step 116, being back to aptly other program coding tectosomes finishes to mix MRA routine.
Even if the principal advantages of this hybridization method is in mobile slow tremulous pulse, also can provide the clear MRA view data (Fig. 7,8A and 8B) of depicting tremulous pulse in pollution irreducible minimum ground that vein is caused.Arterial signal can be emphasized 80-100% (Fig. 9 A).The pollution that vein causes almost can reduce to 0 (Fig. 9 B).
As other advantages of hybridization method, eliminate the burden of the correct correction of carrying out a leaning magnetic field moment (m1) in FSD process.In FSD method in the past, in order to obtain balanced between the minimizing of the maximization of arterial signal and pollution that vein causes, need the m1 value of careful selection DA shooting.In new hybridization method, can fix the maximum of m1.It is simple that the selection of the m1 relevant with the data set of intermediate range becomes.In the flowing an of part, must fully increase m1 in order to produce phase shift, but in order to make very doughtily vein decay, and can not be excessively strong.Simply therefore the selection of m1 becomes does not need aligning step, thereby has improved the robustness of FSD imaging.
Fig. 8 A shows the MIP of the subtraction image of the hybridization method generation being used as shown in example.Arterial signal is compared the middle data of m1=that only use shown in Fig. 8 B and the MIP image generating, grow in tip tremulous pulse.Fig. 9 A shows vision-mix (Fig. 8 A) with respect to the improvement of the intermediate image of type (Fig. 8 B) in the past.At this, white portion represents to see the improvement of object signal intensity.Fig. 9 B shows in vision-mix (Fig. 8 A), how to have improved the maximum image of type (Fig. 3 B) in the past.At this, black picture element represents the signal that expectation is deleted from final image.In Fig. 9 A and Fig. 9 B, Lycoperdon polymorphum Vitt all represents neutrality (, from FSD in the past unchanged).
As mentioned above, composition algorithm formula has multiple forms.For example, each pixel of more each data set mutually.In the above-mentioned example that has used N=3, can carry out the comparison between benchmark and centre, centre and maximum and benchmark and maximum for 3 different threshold parameters.In other examples, can be by being suitable for function (for example,, by the method for substitution numerical value (being suitable for) output judged result in the function of preparation) displacement arithmetic comparison.Relation between signal and m1 due to can by sine curve or same mathematical function analytical describe, therefore can will be suitable for as analytic function from the pixel data of each set.With counting property more similarly, can be used as the suitable parameters that result the obtains numerical value of the result by substitution numerical value is obtained in function (for example, as) to carry out the judgement of the characteristic (tremulous pulse, vein or background) of location of pixels.
Composition algorithm also can be designed as the final MRA image set I (for example, skipping the typical separation subtraction process of (skip) BA-X=I) of output.Now, from the selection of the pixel value of multiple images of obtaining, in vision-mix itself, only identify and comprise (tremulous pulse or the vein) pixel value as object.
In addition, can apply any MRA method take subtraction as basic mode in the process of this description.Be not limited to FSD, also can with the additive method Combination application such as FS-FBI.In FS-FBI, flow dephasing effect, is inside in the part of the separated prepulsing module in the RF echo series of pulse train of the FSE (Fast Spin Echo) using based on data collection rather than as FSD.Continue each RF echo of echo series of the leaning magnetic field that reading after adjustment, phase code (encode), section (slice) are selected.Provide size and the direction of the m1 flow-dephasing vector of effect to control.Like this, different FS-FBI data sets can be by using different leaning magnetic field moment (m1) or collecting with the Phase delay of different heart beat cycles or with its both sides.Different data sets can combine to collect by different m1 values, different m1 direction, different trigger delay (time delay) or its.Same with the example of above-mentioned FSD, N FS-FBI data set can be synthesized in order to generate vision-mix X.Or, then, can be used in the subtraction of having optimized the image I of tremulous pulse or having optimized the image I of vein for generating.
In addition, as fluid mobile in the subject of applying in embodiment, be not limited to blood, also can be equally applicable to CSF (cerebrospinal fluid), lymph (lymph) liquid, bile (bile), pancreatic juice (pancreatic juice) etc.Generally, the process of performance can be assisted and the fluid that moves from other or background, be separated the signal from certain fluid herein.And do not rely on relaxation properties (for example, the T of the fluid of MR
1, T
2, T
2 *(star (strar)) but only depend on its mobile characteristic.Suppose the fluid that separates and flow velocity, flow direction, heart beating or breathe between relation in, have and may confuse different characteristics near fluid, the combination of leaning magnetic field moment m1 and trigger delay (time delay) can be designed as the difference of these characteristics of applying in a flexible way.These data sets are concerned about the describing of fluid of object and application mix technology in order to optimize.
As mentioned above, can use the process in this description, generate the MRA image of optimizing vein for phlebography.That is, by composition algorithm or subtractive process or its both sides are added to change, can make arterial signal minimize, veneous signal is maximized.And in other examples, CSF (cerebrospinal fluid) has velocity ratio tremulous pulse or the slow such characteristic of vein.Therefore, the characteristic of this fluid can be neatly for distinguishing the such flow velocity of blood fast fluid and CSF.
In FSD in the past, only need to obtain N=2 image set.Therefore, in method in the past, can save and time of the proportional amount in (N-2)/2.For example, state in the use in the inspection of N=3 of new mixed method, cost is than the time of FSD long 50% in the past.Therefore,, in new method, can save the processing of correct scan and the correction data of spended time.Obtain and the time of processing cost of correction data can reasonably be estimated as the degree identical with the time of obtaining cost (general two minutes) of a data set.Therefore,, in N=3 inspection or hybridization, required time is tested roughly same degree with FSD in the past.
As mentioned above, the MR imaging apparatus relevant to embodiment (for example, MRI system) possesses collection unit and generating unit.Fluid in collection unit shooting subject, collects the different multiple images of camera pulse sequential parameter.At this, so-called " fluid " refers to such as blood, cerebrospinal fluid (CSF), lymph (lymph) liquid, bile (bile), pancreatic juice (pancreatic juice) etc.In addition, so-called " camera pulse sequence " refers to for example FSD or FS-FBI isopulse sequence.The dephasing pulse that so-called " parameter of camera pulse sequence " refers to the spin dephasing that for example makes fluid in addition (for example, be additional to and read leaning magnetic field pulse) leaning magnetic field moment value, dephasing pulse apply time delay (for example, the peak value of R ripple is to the time delay of signal collection) or its combination etc. in direction, heart beat cycle.If the fluid of drawing object for example and flow velocity, flow direction, heart beating or breathe between relation in, have and may confuse different characteristics near fluid, these parameter designing are the difference of these characteristics of applying in a flexible way.For example, collection unit, in the pulse train of FSD or FS-FBI etc., is carried out the mutually different collection of these parameters, and collects multiple images.In addition, in generating unit at least one image from multiple images, select the pixel value of the each position in image, and use the pixel value in each position of selecting to generate vision-mix.
In addition, the collection unit relevant from embodiment be the different multiple images of collection parameter in the paradoxical expansion of subject for example, thereby at least one image multiple images that generating unit is collected in paradoxical expansion, select the pixel value of each position to generate vision-mix.
In addition, the generating unit relevant to embodiment for example with position corresponding to the vein of subject on select high pixel value, on the position corresponding with the tremulous pulse of subject, select low-pixel value.Or, the generating unit relevant to embodiment for example with position corresponding to the tremulous pulse of subject on select high pixel value, on the position corresponding with the vein of subject, select low-pixel value.
In addition, the MR imaging apparatus relevant to embodiment for example also possesses the subtraction image generating unit that generates subtraction image according to vision-mix.Now, collection unit is for example collected at least one image within the cardiac dilatation phase of subject, and collects multiple images in the paradoxical expansion of subject.Generating unit for example selects the pixel value of each position to generate vision-mix at least one image from multiple images of collecting in paradoxical expansion, subtraction image generating unit is by solve the difference between image and the vision-mix of collecting within the cardiac dilatation phase of subject, thus generation subtraction image.But embodiment is not limited thereto, as mentioned above, according to the design of composition algorithm that for example generates vision-mix, for example, also can in vision-mix, only comprise the pixel value of the fluid of drawing object.And, for example, also can in vision-mix, only comprise and draw the fluid of object and the pixel value of background.
In addition, the collection unit relevant from embodiment collected the different multiple images of leaning magnetic field moment.For example, collection unit is collected image according to the 1st value a leaning magnetic field moment within the cardiac dilatation phase, collects multiple images according to a leaning magnetic field moment of the 2nd value and the 3rd value in paradoxical expansion.At this, as use Fig. 4 illustrated, the signal value producing at the mobile blood of intra-arterial of the subject of the signal value that the blood mobile intravenous of subject of the 1st value is produced and the 1st value is during as each reference value, for example, the 3rd value is the value that the signal of the mobile blood generation of intravenous and the both sides of the signal that the mobile blood of intra-arterial produces decay from each reference value.And for example, the 2nd value is the intermediate value between the 1st value and the 3rd value, the attenuation amplitude from reference value of the signal that the mobile blood of the decay amplitude ratio intra-arterial from reference value of the signal that the mobile blood of intravenous produces produces is little.
In addition, the generating unit relevant to embodiment is for example on the each position in image, difference and threshold value between the pixel value of the image of collecting by the pixel value of the image of collecting according to the 1st value and according to the 2nd value compare, when this difference is less than threshold value, select the pixel value of the image of collecting according to the 2nd value as the pixel value of this position, in the time that this differential ratio threshold value is large, thereby select the pixel value of the image of collecting according to the 3rd value to generate vision-mix as the pixel value of this position.
According to the MR imaging apparatus of above-mentioned at least one embodiment and MR imaging method, can collect the image of depicting rightly fluid.
Be illustrated for several embodiments of the present invention, but these embodiments illustrate as an example, be not intended to limit scope of invention.These embodiments can be implemented by other means, in the scope of main idea that does not depart from invention, can carry out various omissions, displacement, change.These embodiments or its distortion be included in invention scope or main idea in the same, in the invention described in being comprised within the scope of claim and its scope being equal to.
Claims (10)
1. a MR imaging apparatus, is characterized in that, comprising:
Collection unit, the fluid in shooting subject, collects the different multiple images of parameter of the camera pulse sequence of the intensity of the signal that affects this fluid generation;
Generating unit, selects the pixel value of the each position in image at least one image from above-mentioned multiple images, generate vision-mix with the pixel value of selected each position.
2. MR imaging apparatus according to claim 1, is characterized in that:
Above-mentioned collection unit is collected the different multiple images of above-mentioned parameter in the paradoxical expansion of above-mentioned subject;
In above-mentioned generating unit at least one image from multiple images of collecting in above-mentioned paradoxical expansion, select the pixel value of above-mentioned each position to generate above-mentioned vision-mix.
3. MR imaging apparatus according to claim 1, is characterized in that:
Above-mentioned generating unit is selected high pixel value on the position corresponding with the vein of above-mentioned subject, on the position corresponding with the tremulous pulse of above-mentioned subject, selects low-pixel value.
4. MR imaging apparatus according to claim 1, is characterized in that:
Above-mentioned generating unit is selected high pixel value on the position corresponding with the tremulous pulse of above-mentioned subject, on the position corresponding with the vein of above-mentioned subject, selects low-pixel value.
5. MR imaging apparatus according to claim 1, is characterized in that,
Also comprise: subtraction image generating unit, generates subtraction image according to above-mentioned vision-mix;
Above-mentioned collection unit is collected at least one image within the cardiac dilatation phase of above-mentioned subject, and collects multiple images in the paradoxical expansion of above-mentioned subject;
In above-mentioned generating unit at least one image from multiple images of collecting in above-mentioned systole, select the pixel value of above-mentioned each position to generate above-mentioned vision-mix;
Above-mentioned subtraction image generating unit is by solve the difference between image and the above-mentioned vision-mix of collecting within the cardiac dilatation phase of above-mentioned subject, and generates above-mentioned subtraction image.
6. MR imaging apparatus according to claim 5, is characterized in that:
Above-mentioned collection unit is collected the different multiple images of leaning magnetic field moment.
7. MR imaging apparatus according to claim 6, is characterized in that:
Above-mentioned collection unit is collected image according to the 1st value a leaning magnetic field moment within the above-mentioned cardiac dilatation phase, collects multiple images according to a leaning magnetic field moment of the 2nd value and the 3rd value in above-mentioned paradoxical expansion;
In the signal value that the intravenous blood according to being flowing in above-mentioned subject in above-mentioned the 1st value is produced and above-mentioned the 1st value according to the signal value of endarterial blood generation that is flowing in above-mentioned subject during as each reference value,
Above-mentioned the 3rd value is the value that basis is flowing in to the signal of above-mentioned intravenous blood generation and decays from each reference value according to the signal both sides that are flowing in above-mentioned endarterial blood generation,
Above-mentioned the 2nd value is the intermediate value between above-mentioned the 1st value and above-mentioned the 3rd value, little according to the attenuation amplitude from said reference value of signal that is flowing in above-mentioned endarterial blood generation according to the attenuation amplitude beguine from said reference value that is flowing in the signal that above-mentioned intravenous blood produces.
8. MR imaging apparatus according to claim 7, is characterized in that:
Above-mentioned generating unit is for the each position in image, difference and threshold value between the pixel value of the image of collecting by the pixel value of the image of collecting according to above-mentioned the 1st value and according to above-mentioned the 2nd value compare, in the time that this difference is less than threshold value, select the pixel value of the image of collecting according to above-mentioned the 2nd value as the pixel value of this position, in the time that this difference value is greater than threshold value, thereby select the pixel value of the image of collecting according to above-mentioned the 3rd value to generate vision-mix as the pixel value of this position.
9. MR imaging apparatus according to claim 2, is characterized in that:
Above-mentioned collection unit, in above-mentioned paradoxical expansion, is collected different multiple images time delay of the heart beat cycle based on above-mentioned subject.
10. a MR imaging method, is carried out by computer, it is characterized in that, comprising:
The fluid of shooting in subject, collects the collecting process of multiple images that the parameter of camera pulse sequence of the intensity of the signal that affect this fluid generation is different;
In at least one image from above-mentioned multiple images, select the pixel value of the each position in image, and use the pixel value of each position of selecting to generate the generation operation of vision-mix.
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Effective date of registration: 20160713 Address after: Japan Tochigi Patentee after: Toshiba Medical System Co., Ltd. Address before: Tokyo, Japan, Japan Patentee before: Toshiba Corp Patentee before: Toshiba Medical System Co., Ltd. |