Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
  • G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities

Definitions

• the main image is attached to the nuclei ⁇ MJf layer imaging ffiiE ⁇ method.
• MRI nuclear medicine experiment
• MR magnetic resonance
• NMR nuclear medicine experiment
• the MRI by the Fourier is described in the pulse sequence of the high frequency and gradient used when the method is used.
• RF is the high frequency
• 3 ⁇ 4 ⁇ are applied to the X axis.
• the CTX has an E (gradient magnetic field on the X-axis, a gradient field on the y-axis, and a Gz field on the z-axis ⁇ ⁇ ).
• the signal is a spin echo signal after a 180 ° pulse (hereafter, SE signal).
• SE signal indicates the timing of the signal of the gradient given to the transliteration.
• Spins in the slice plane in the vertical slice are driven explicitly.
• G ⁇ is used to make the spin ⁇ as to tongue and make it i 8 cr north, and is called a phase gradient.
• Gz-ichi is for restoring the spin decoration that was created by Oz + .
• One set of such pulse sequences is used for signal measurement of one view " ⁇ ". Such a pulse sequence is repeated with a period TR.
• the NMR signal may be measured using the inversion recovery method (hereinafter referred to as IR method).
• Fig. 4 shows the pulse sequence of the IR method. This IR method is 180. No, apply a rescue (1) to spin the whole body, set the recovery time to TI, and 9 0 to return. After a nos or ife, it is 180 when the time is reversed. Sprinkle the nut (2). As a result, an SE signal indicating is obtained at the time of further ⁇ T ⁇ 90. If f is ⁇ ⁇ ⁇ up to the peak of the SE signal, ⁇ is equal to 2 times. 1 80. Pulse ⁇ ) Next 180. No ,. The next view is made by using Luz (1).
• the purpose of this translation is to scan the time of the scan, i.e., tii ⁇ tf, and also to measure and store the phase distortion data for the first instar in the scan area in advance. It is in.
• i3 ⁇ 43 ⁇ 4ffi IE3 ⁇ 43 ⁇ 4i in the garden to be imaged, first the phantom was used to acidify the distortion in a small area of ffiS, and the measured values were used to measure the phase distortion in the image data measured for the male body. The area corresponding to the area The image data in the side page area is examined to determine whether the other part of the object data becomes zero, and the ES is changed to zero if ⁇ ⁇ is not used.
• the positive LV m 3 ⁇ 4IES of the leverage page area is calculated by using l®, and the correction amount of the side-by-side ⁇ 1 area is obtained by the same listening using the obtained translation effES.
• m denote the measured image data distortion for the subject.
• Figure 2 is a flowchart of the distorted map procedure
• Figure 3 shows the pulse sequence of MRI as ⁇ m
• Fig. 4 shows the pulse sequence of the IR method.
• Fig. 5 Curve showing the relationship between the image data obtained by the IR method and the recovery distance TI (? ⁇
• Fig. 6 Pro and Zoku diagrams showing the S component of the MRI device that implements the method of the invention of the country invention.
• Fig. 7 shows a pulse sequence for measuring distortion.
• the 8 A diagram and the 8 B Figure is Koboshiibitsu map ifc ⁇ l 3 ⁇ 4
• FIG. 6 shows the »S composition of the MRI apparatus returning the method of the present invention.
• reference numeral 1 denotes a magneto / socket assembly having a space for inserting a subject therein, and a fixed static magnetic field is applied to the sample so as to surround this space.
• Giving an F pulse An RF transmitting coil and a receiving coil for detecting the NMR signals of males 3 and others are arranged (hidden).
• the seasonal crane coil has three axes of X, Y and ⁇ (not shown).
• the gate control circuit 8 is operated in accordance with ci and ci ⁇ , and an RF pulse signal based on, for example, Fourier ⁇ is sent from RF3 ⁇ 43 ⁇ 4iiili 4 to the RF transmission coil.
• 10 is a translator for translating the S3 ⁇ 43 ⁇ 45 signal output signal as a symbol, referring to the output of the PIF listening circuit 9. This output signal is converted to a digital signal at AD ⁇ tl 11 and ff ⁇ 7 1 2 If: console for making a sequence of pulses, such as! ⁇ and various ⁇ , etc. 1 3 is an image created by 7 «7 It is a table.
• Input a signal based on the value tc. m 7 performs a V control signal based on the circulation value i: ⁇ and sends it to the sequence storage circuit 6.
• the sequence storage circuit 6 controls the gradient signal based on the retrospective signal (1) to control the ring circuit 3 to generate a predetermined pulse sequence, and controls the gate circuit 8.
• the gate circuit 8 is output by the RF circuit 9
• the RF signal is converted into a signal having a pulse width and length, and a RF pulse is supplied to RF f] 4.
• This RF-North is amplified in R F ⁇ I I ⁇ 4, and is given to the glue by Mt, Zo-assembly 1 in the static magnetic field generated by the magnetic field, and is given to the glue by the circuit 3 Resonate the spin.
• the SE signal generated by the bird was received and knitted by ffi3 ⁇ 4m5, m
• ⁇ Detection detector 10 uses the output of RF circuit 9 as a ⁇ signal to transit input MMRi, and sends its output signal to AD ⁇ Hl1.
• AD ⁇ ⁇ 11 1 Difficult to digital signal 7t NMR signal is
• An image Sii is formed by a predetermined c3 ⁇ 4 ⁇ according to the sequence ⁇ , and is formed by ⁇ ⁇ 13. In 1 ⁇ 7, the contents of the sequence storage circuit 6 can be rewritten, whereby various scan sequences can be realized.
• this month's ⁇ phase ffiE ⁇ method first measures the desired small area ⁇ 1 3 ⁇ 4 strain using a phantom on the cross section to be imaged, and uses the measured value to calculate ⁇ Of the transformed image data, the area corresponding to the distorted area
• ⁇ Ffl Complementary IES! ⁇
• Fig. 7 shows an example of a pulse sequence for phantom scan for distortion performed every 1 ⁇ °, and a simple spin echo pulse sequence with a warp gradient of 180.
• the pulse 3 ⁇ 43 ⁇ 4! # J3 ⁇ 4 is subjected to an operation to give a y gradient 1], and the direction is changed in the direction of ⁇ 1- ⁇ °, and the resolution is reduced.
• you scan 4 scans of a phantom for distortion measurement you can reduce the number of views in the whole scan as much as possible. This is a scan of the fiber, which is only 4% of the view of the book, and only 1.6% of the view is removed.
• the SE signal is measured, for example, by the sequence shown in FIG.
• FIG. 2 is a flowchart for the map in FIG. In the following, the method of translation is explained by following the words of the steps attached to the left side of the block in both figures.
• the data is entered and the image data is entered.
• the image data A (X, y) and the part corresponding to the high spatial circumference are cut into l! Number of image data D (X, y).
• the wave image data is used for distortion ffiEH.
• iSIS data Image ⁇ received itr ⁇ number i fiig ⁇ ! L3 ⁇ 43 ⁇ 4 image ⁇ ⁇ ⁇ (X, y) ⁇ ⁇ A (X, y) iiJ m (x, y) ⁇ page area S ⁇ ⁇ ⁇ ⁇ Image data.
• Other symbols also mean data at the respective coordinates (X, y >>).
• the desired location fiffi is obtained from the fiffi distortion ll ⁇ ffi image.
• the value of at a desired location is determined by the following equation.
• n starts from 0 to 3, and in the first ⁇ 3 ⁇ 4 ⁇ , the fiffl complement iEft ⁇ (X 0, yo) 'H «E obtained by the step' c, and the ffiE is; ⁇ the image data B (X 0, y 0>.
• ⁇ '(X ⁇ , y a ) ⁇ ( ", y n) ⁇ (x 0, y n)
• step e image data obtained by correcting the phase with ⁇ (X n , y n )
• step d If not, return to step d, and return the irm male to the end of ⁇ page area.
• the 2nd i50®t is located in the page area to the right of the 8th Al3 ⁇ 4 * t3 ⁇ 4map, for example. Try ⁇ gffiE ⁇ ⁇ for ES. At this time, assuming that the value is 1 ⁇ 3 ⁇ 4 2, it is placed in an area where fi ⁇ is not yet entered near ⁇ : ⁇ 2 8 as shown in the figure. In the same way, the values are arranged in the same manner.
• the imaging ffi distortion map for the page area is correct, and the process proceeds to step j in FIG.
• step i using the iDCTaiE amount for each region arranged in the distortion map, the male body 3 ⁇ 4t composed image ⁇ ⁇ pixel 'data is transformed.
• the distortion map data and « ⁇ previous image data A (X, y) are input,
• the present invention is not intended to be a statement 3 ⁇ 3 ⁇ 4. As described in ⁇ ⁇ debo 2 furry 3 ⁇ 4i7), it can also be used in the if ⁇ r of the three-dimensional Fourier method. % ⁇ , Measured values and other data UrT will be 35t data. Also, a point near 8 is near 26. Also, if you add to the feffi distortion measurement scan and devise the method of the area ⁇ , you can apply it to the ma ⁇ slice ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ The sequence of distortion 11 constant i, the imaging data ⁇ before and after But no. :

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• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Radiology & Medical Imaging (AREA)
• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• High Energy & Nuclear Physics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Magnetic Resonance Imaging Apparatus (AREA)

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• 1987
  • 1987-07-31 JP JP62192386A patent/JPS6434345A/ja active Granted
• 1988
  • 1988-07-30 WO PCT/JP1988/000770 patent/WO1989000833A1/ja unknown

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