Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2002-12-04
2004-06-01
Lefkowitz, Edward (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
Reexamination Certificate
active
06744251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inspection apparatus using nuclear-magnetic-resonance (NMR), or an NMR inspection apparatus, which enables an examiner to designate directly a section of a subject to be imaged while watching the subject.
2. Description of Related Art
The nuclear magnetic resonance-imaging apparatus, or MRI apparatus, is a medical image-processing apparatus that causes the nuclear magnetic resonance of water molecules in a section of a subject and reconstructs a sectional image from NMR signals. In general, a slicing magnetic field gradient is applied to a region of a subject to be examined to designate a section to be imaged in the subject. At the same time, an excitation pulse is applied to the subject to excite its spins. An MRI signal (echo) is generated and measured in the phase of focusing of the excited spins. To add positional information to the excited spins, a phase-encoding magnetic field gradient and a read-out magnetic field gradient normal to each other are applied to the subject for the time period from the excitement of the subject to the acquisition of the echo. Measured echoes are arranged in the k-space by an axis of abscissa “kx” and an axis of ordinate “ky”. Each echo is represented by a line parallel to the kx-axis. The data in the k-space undergo inverse Fourier transformation to reconstruct an image of the designated section.
The pulse to generate an echo and the magnetic field gradients are applied to the subject in accordance with prescribed pulse sequences. Various pulse sequences for various purposes are known. For example, in the gradient-echo method, or GE method, the pulse to generate an echo is repeatedly applied to a subject. Every time the pulse is applied to the subject, the phase-encoding magnetic field gradient applied to the subject is changed. In this way, the necessary number of echoes for reconstructing a sectional image are measured.
FIG. 1A
shows pulse sequences for the GE method. A pulse
201
for a slicing magnetic field gradient in the z-direction and an RF pulse
202
of proton's resonance frequency “f
0
” for a high-frequency magnetic field to excite the spins of a subject to be examined are applied to the subject in order to induce the NMR of protons in the subject. Then, a pulse
203
for a phase-encoding magnetic field gradient is applied to the subject to add positional information in the phase-encoding direction (y-direction) to the phase of the excited spins and another pulse
206
for a read-out magnetic field gradient for dephasing in the x-direction is applied to the subject. Next, while a pulse
207
for a read-out magnetic field gradient is being applied to add the positional information in the read-out direction (x-direction) to the excited spins, an NMR signal (an echo)
208
is measured. The necessary number of echoes for reconstructing a sectional image are measured while the procedure from the application of the pulse
201
to the measurement of the echo
208
is being repeated in a “TR” cycle. The echoes are arranged in the k-space (
209
) as shown in FIG.
1
B and undergo two-dimensional inverse Fourier transformation to reconstruct a sectional image.
In MRI, while watching an image displayed on a display, the examiner designates a section to be imaged as follows. First, an image of the whole region of interest is taken as a reference image and displayed on the display. Second, a line segment is displayed on the display and the position and angle of the line segment is moved and changed by using a mouse or a cursor to designate a section and take its image. As the need arises, the examiner designates and images a section repeatedly while making changes on the reference image. There is a method of designating a section of a subject by using a plate-like joystick instead of a mouse (JP-A No. 238915/1997: prior art-1). This method enables the examiner to designate a section intuitively because he can designate the inclination of a section as the inclination of the joystick.
In accordance with the prior art-1, the examiner, watching an image on a display at a distance from the subject, designates indirectly a section to be imaged; accordingly, it is difficult for him to grasp the position of a section being designated. In accordance with the prior art-1, the examiner can directly designate the inclination of a section to be imaged with a joystick, but he cannot directly designate the position of the section because the joystick is typically fixed to something.
SUMMARY OF THE INVENTION
The present invention provides a NMR inspection apparatus that enables the examiner to designate directly a section of a subject to be imaged.
One aspect of the present invention is directed to an NMR inspection apparatus that comprises (i) means for generating a static magnetic field, (ii) means for generating magnetic field gradients in first, second, and third directions normal to one another, (iii) means for generating a high-frequency magnetic field, (iv) means for detecting NMR signals derived from a subject, (v) means for processing detected NMR signals, (vi) a section-designating unit for designating a plane including a section of the subject to be imaged, and (vii) a control unit for controlling the means for generating magnetic field gradients, the means for generating a high-frequency magnetic field, the means for detecting NMR signals, the means for processing detected NMR signals, and pulse sequences for taking an image of the section of the subject to be imaged. The means for generating magnetic field gradients is controlled so that a prescribed part of a plane designated by the section-designating unit is the section of the subject to be imaged.
The section-designating unit has reference objects to be set at two or three reference points and is held in the hand of an examiner to be moved and operated in the immediate neighborhood of the subject lying in static magnetic field and magnetic field gradients generated by the means for generating a static magnetic field and the means for generating magnetic field gradients. The examiner, watching the subject, can move and operate the section-designating unit as if he were handling the probe of ultrasound diagnosis equipment. In a preferred embodiment of section-designating unit, the examiner can designate a section of the subject to be imaged by putting the unit into contact with the subject. In another preferred embodiment of section-designating unit, the examiner can designate a section of the subject to be imaged without putting the unit into contact with the subject.
By using the NMR signals derived from the two or three reference objects by the pulse sequences for imaging, the means for processing detected NMR signals finds a plane which includes the middle point between the two reference objects and whose normal vector is a vector connecting the two reference objects or a plane including the three reference objects in terms of reference spatial coordinates. The control unit controls the means for generating magnetic field gradients so that a prescribed part of the plane is the section of the subject to be imaged.
Preferred methods of NMR examination in accordance with the present invention are summarized below.
(1) A method of NMR examination comprising the steps of: (i) designating a plane including a section of the subject to be imaged with the section-designating unit, which has reference objects to be set at two or three reference points and is held in the hand of an examiner to be moved and operated in the immediate neighborhood of the subject lying in the static magnetic field and magnetic field gradients, (ii) finding a plane which includes the middle point between the two reference objects and whose normal vector is a vector connecting the two reference objects or a plane including the three reference objects in terms of reference spatial coordinates, and (iii) controlling the magnetic field gradients so that a prescribed part of the plane is the section of the subject to be imaged.
(
Ochi Hisaaki
Taniguchi Yo
Umemura Shin'ichiro
Yamamoto Yukari
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Reed Smith LLP
Vargas Dixomara
LandOfFree
Inspection apparatus using nuclear-magnetic-resonance does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Inspection apparatus using nuclear-magnetic-resonance, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inspection apparatus using nuclear-magnetic-resonance will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3342790