U.S. patent application number 09/777479 was filed with the patent office on 2001-07-05 for mri coil and mri apparatus.
This patent application is currently assigned to GE YOKOGAWA MEDICAL SYSTEMS, LIMITED.. Invention is credited to Furuta, Osamu, Hayaklawa, Kazuhiko.
Application Number | 20010007054 09/777479 |
Document ID | / |
Family ID | 15640636 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010007054 |
Kind Code |
A1 |
Furuta, Osamu ; et
al. |
July 5, 2001 |
MRI coil and MRI apparatus
Abstract
In order to mitigate the feeling of confinement experienced by a
subject (patient) and improve the SIN ratio of an MRI coil when
used as a head coil, there is provided an MRI coil 10 comprising a
pair of opposing coils 1 and 2 whose coil surfaces face each other
with an imaging space interposed, and a quadrature coil 3 which has
a coil surface orthogonal to the coil surfaces of the opposing
coils 1 and 2 and surrounds the imaging space. When the MRI coil 10
is used as a head coil, the quadrature coil 3 is fitted over the
eyes of a subject H, and the opposing coils 1 and 2 are positioned
near the ears of the subject H.
Inventors: |
Furuta, Osamu; (Tokyo,
JP) ; Hayaklawa, Kazuhiko; (Tokyo, JP) |
Correspondence
Address: |
MOONRAY KOJIMA
Box 627
Williamstown
MA
01267
US
|
Assignee: |
GE YOKOGAWA MEDICAL SYSTEMS,
LIMITED.
|
Family ID: |
15640636 |
Appl. No.: |
09/777479 |
Filed: |
February 6, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09777479 |
Feb 6, 2001 |
|
|
|
09289907 |
Apr 13, 1999 |
|
|
|
Current U.S.
Class: |
600/422 ;
324/318; 600/410 |
Current CPC
Class: |
G01R 33/341 20130101;
G01R 33/34053 20130101; G01R 33/34061 20130101 |
Class at
Publication: |
600/422 ;
600/410; 324/318 |
International
Class: |
A61B 005/055 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 1998 |
JP |
10-157029 |
Claims
1. An MRI coil comprising: a pair of opposing coils whose coil
surfaces face each other with an imaging space interposed; and an
orthogonal coil which has a coil surface orthogonal to the coil
surfaces of the opposing coils and surrounds the imaging space.
2. The MRI coil of claim 1, wherein the opposing coils and the
orthogonal coil are integrally combined so that their positions
relative to one another are maintained unchanged, and part of the
coil surfaces of the opposing coils are opened outward.
3. The MRI coil of claim 1, wherein the opposing coils are
pivotally attached to the orthogonal coil, and the pair of opposing
coils is allowed to be opened in an inverted V-like shape.
4. An MRI apparatus comprising static magnetic field generating
means for generating a static magnetic field to be applied to a
subject during image capture, wherein the MRI coil of claim 1 is
employed to acquire NMR signals from the subject.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an MRI (magnetic resonance
imaging) coil, and more particularly, to an MRI coil capable of
mitigating feeling of confinement experienced by a subject
(patient) and improving the S/N ratio when used as a head coil.
[0002] An example of a conventional MRI head coil is shown in FIG.
1.
[0003] The MRI head coil 70 has a cylindrical shape containing an
imaging space therein for accommodating the head of a subject
H.
[0004] The conventional MRI head coil 70 has the following
problems:
[0005] (1) Since the coil has a cylindrical shape enveloping the
head of the subject H and has few opening portions, visual and
auditory perception of the subject H is extensively restricted and
the subject's exhaled breath fills the coil, giving the subject H a
confined feeling.
[0006] (2) Since the coil envelops the head of the subject H, the
coil requires a cavity having a greater size than the distance from
the tip of the nose to the back of the head, and the coil therefore
cannot be significantly reduced in size. Thus, because the distance
between the subject H and the coil cannot be reduced, the S/N ratio
is lowered.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide an MRI
coil capable of mitigating the confined feeling experienced by a
subject (patient) and improving the S/N ratio when used as a head
coil.
[0008] In accordance with a first aspect of the present invention,
there is provided an MRI coil comprising a pair of opposing coils
whose coil surfaces face each other with an imaging space
interposed, and a quadrature coil which has a coil surface
orthogonal to the coil surfaces of the opposing coils and surrounds
the imaging space.
[0009] When the MRI coil of the first aspect is used as a head
coil, the quadrature coil is fitted over the head of the subject,
and the opposing coils are positioned near the ears of the subject.
In this condition, the quadrature coil overhangs the eyes of the
subject, but does not cover the head top, nose or mouth. The
opposing coils are placed near the ears of the subject, but do not
completely cover the ears. Moreover, the exhaled breath of the
subject does not fill the coil. Hence, the coil does not give the
subject a confined feelings Furthermore, since the quadrature coil
does not cover the nose, the coil does not require a cavity having
a greater size than the distance from the tip of the nose to the
back of the subject H's head, and the coil can be reduced in size.
The reduced size shortens the distance between the subject and the
coil, thereby improving the S/N ratio.
[0010] In accordance with a second aspect of the present invention,
there is provided the MRI coil as described regarding the first
aspect, wherein the opposing coils and the quadrature coil are
integrally combined so that their positions relative to one another
are maintained unchanged, and part of the coil surfaces of the
opposing coils are opened outward.
[0011] A coil is preferably disposed as close to the subject as
possible in order to improve the S/N ratio. Accordingly, the
spacing between the opposing coils is made slightly greater than
the size of the subject. However, this may result in difficulties
in fitting the coil over the head of the subject when the coil is
used as a head coil. The MRI coil of the second aspect has part of
the coil surfaces of the opposing coils opened outward,
facilitating fitting of the coil over the head of the subject.
Moreover, since the opposing coils and the quadrature coil are
integrally combined so that their relative positions remain
unchanged, the coil requires no pivotal attachment mechanism,
thereby simplifying the structure.
[0012] In accordance with a third aspect of the present invention,
there is provided the MRI coil as described regarding the first
aspect, wherein the opposing toils are pivotally attached to the
quadrature coil, and the pair of opposing coils is allowed to be
opened in an inverted V-like shape.
[0013] A coil is preferably disposed as close to the subject as
possible in order to improve the S/N ratio. Accordingly, the
spacing between the opposing coils is made slightly greater than
the size of the subject. However, this may result in difficulties
in fitting the coil over the head of the subject when the coil is
used as a head coil. The MRI coil of the third aspect has the pair
of opposing coils that is allowed to be opened in an inverted
V-like shape, facilitating fitting of the coil over the head of the
subject. Moreover, this eliminates the need to form part of the
opposing coils in an opened shape, thereby simplifying the shape of
the opposing coils.
[0014] The MRI coil of the present invention may be used as, for
example, a knee coil for imaging the knee.
[0015] In accordance with a fourth aspect of the present invention,
there is provided an MRI apparatus comprising static magnetic field
generating means for generating a static magnetic field to be
applied to a subject during image capture, wherein the MRI coil as
described regarding any of the first through third aspects is
employed to acquire NMR signals from the subject.
[0016] The MRI coil and MRI apparatus of the present invention can
thus mitigate feeling of confinement experienced by a subject
(patient) and improve the S/N ratio when the coil is used as a head
coil.
[0017] Further objects and advantages of the present invention will
be apparent from the following description of the preferred
embodiments of the invention as illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a conventional MRI head
coil.
[0019] FIGS. 2 (a) - (c) are views taken from three orthogonal
directions of an MRI head coil in accordance with the first
embodiment of the present invention.
[0020] FIG. 3 illustrates the MRI head coil of FIG. 2 prior to
being fitted over a subject.
[0021] FIG. 4 illustrates the MRI head coil of FIG. 2 fitted over
the subject.
[0022] FIG. 5 is a perspective view of an MRI head coil in
accordance with the second embodiment of the present invention.
[0023] FIG. 6 illustrates the configuration of a vertical magnet
MRI apparatus in accordance with the third embodiment of the
present invention.
[0024] FIG. 7 illustrates imaging of the head in the vertical
magnet MRI apparatus of FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention will now be described in more detail
with reference to its embodiments shown in the accompanying
drawings.
[0026] First Embodiment
[0027] FIGS. 2(a) - (c) are respectively a front elevational view,
a right side view and a plain view of an MRI head coil in
accordance with the first embodiment of the present invention.
[0028] The MRI head coil 10 comprises a pair of opposing coils 1
and 2 whose coil surfaces face each other with an imaging space
interposed, and a quadrature coil 3 which has a coil surface
orthogonal to the coil surfaces of the opposing coils 1 and 2 and
surrounds the imaging space.
[0029] The opposing coils 1 and 2 have a generally circularly
annular shape as a whole, except that their respective front
peripheral portions 1a and 2a are opened outward.
[0030] The quadrature coil 3 has a generally track-like annular
shape (i.e., an annular shape consisting of semicircles and
straight lines like a race track for field sports).
[0031] The opposing coils 1 and 2 and the quadrature coil 3 are
integrally combined so that their relative positions are maintained
unchanged.
[0032] FIG. 3 illustrates the MRI head coil 10 being fitted over
the head of a subject.
[0033] A cradle C is provided with a head rest R for supporting the
head of the subject H a certain distance above the cradle C, and a
concave portion K for inserting the MRI head coil 10 below the head
rest R. The MRI head coil 10 is set behind the head of the subject
H.
[0034] First, the subject H is laid on the cradle C at a position
such that the head of the subject H is supported by the head rest
R.
[0035] The MRI head coil 10 is then slid to be fitted over the head
of the subject H. That is, the MRI head coil 10 is slid to a
position at which the quadrature coil 3 overhangs the eyes of the
subject H.
[0036] FIG. 4 is a cross sectional view illustrating the MRI head
coil 10 fitted over the head of the subject H.
[0037] The opposing coils 1 and 2 are electrically connected so
that their currents flow in the same direction (the connection may
be either serial or parallel), to constitute so-called Helmholtz
coils. This generates a homogeneous magnetic field in the imaging
space between the opposing coils 1 and 2.
[0038] The quadrature coil 3 is "quadrature connected" with respect
to the opposing coils 1 and 2. This achieves effective reception of
NMR signals.
[0039] The above-described MRI head coil 10 offers the following
advantages:
[0040] (1) The quadrature coil 3 overhangs the eyes of the subject
H, but does not cover the head top, nose or mouth. The opposing
coils 1 and 2 are placed near the ears of the subject H, but do not
completely cover the ears. Moreover, the exhaled breath of the
subject H does not fill the coil. Hence, the coil does not give the
subject H a confined feeling.
[0041] (2) Since the quadrature coil 3 does not cover the nose, the
coil does not require a cavity having a greater size than the
distance from the tip of the nose to the back of the subject H's
head, and the coil may be reduced in size. The reduced size
shortens the distance between the subject H and the coil, thereby
improving the S/N ratio.
[0042] (3) Since the front peripheral portions 1a and 2a of the
opposing coils 1 and 2 are opened outward, the coil is easy to fit
over the head of the subject H.
[0043] (4) Since the opposing coils 1 and 2 and the quadrature coil
3 are integrally combined so that their relative positions are
maintained unchanged, the coil requires no pivotal attachment
mechanism, thereby simplifying the structure.
[0044] Second Embodiment
[0045] FIG. 5(a) is a perspective view of coils in an MRI head coil
in accordance with the second embodiment of the present
invention.
[0046] The MRI head coil 20 comprises a pair of opposing coils 4
and 5 whose coil surfaces face each other with an imaging space
interposed, and a quadrature coil 6 which has a coil surface
orthogonal to the coil surfaces of the opposing coils 4 and 5 and
surrounds the imaging space.
[0047] The opposing coils 4 and 5 have a generally circularly
annular shape.
[0048] The quadrature coil 6 has a generally track-like annular
shape.
[0049] The opposing coils 4 and 5 and the quadrature coil 6 are
integrally combined by means of covers 14 - 16 as will be described
hereinafter.
[0050] FIG. 5 (b) is a perspective view of the covers for the MRI
head coil 20.
[0051] The opposing coil 4 is contained in a left cover 14. The
opposing coil 5 is contained in a right cover 15. The quadrature
coil 6 is contained in a central cover 16.
[0052] The left and right covers 14 and 15 are pivotally attached
to the central cover via hinges, and are allowed to be opened in an
inverted V-like shape. That is, the opposing coils 4 and 5 are
allowed to be opened in an inverted V-like shape.
[0053] FIG. 5 (c) is a perspective view of the MRI head coil 20
with its covers 14 and 15 opened.
[0054] While the opposing coils 4 and 5 shown in FIG. 5 (c) are
opened in an inverted V-like shape in the horizontal direction, the
opposing coils can instead be configured to be opened in a V-like
shape in the upward or downward direction.
[0055] The above-described MRI head coil 20 offers the following
advantages:
[0056] (1) Since the coil has a large opening portion, the coil
intercepts only a small portion of the field of view of the subject
H and is not filled with the exhaled breath of the subject H,
thereby giving the subject H no feeling of confinement.
[0057] (2) Since the quadrature coil 6 does not cover the nose, the
coil does not require a cavity having a greater size than the
distance from the tip of the nose to the back of the subject H's
head, and the coil can be reduced in size. The reduced size
shortens the distance between the subject H and the coil, thereby
improving the S/N ratio.
[0058] (3) Since the opposing coils 4 and 5 are opened in an
inverted V-like shape, the coil is easy to fit over the head of the
subject H.
[0059] (4) The opposing coils 4 and 5 can have a simple shape.
[0060] Third Embodiment
[0061] FIG. 6 illustrates the configuration of a vertical magnet
MRI apparatus employing the MRI head coil of the present
invention.
[0062] The vertical magnet MRI apparatus 100 comprises a vertical
magnet apparatus 30, a movable chair 40 and a movable table (not
shown).
[0063] The vertical magnet apparatus 30 has a vertical opposing
magnet 31 whose opposing surface is vertically disposed, another
vertical opposing magnet 32 (not shown) which is disposed opposite
to the magnet 31, a rail 33 (34) provided on the opposing surface
of the vertical opposing magnet 31 (32), a table stopper apparatus
(not shown) and a chair stopper apparatus 35.
[0064] The rail 33 (34) is provided for supporting the cradle
coming out of the movable table.
[0065] The table stopper apparatus and the chair stopper apparatus
35 are provided with connectors for establishing electrical
connection with the movable table or the movable chair 40.
[0066] The movable chair 40 has a supporting panel 41 for
supporting the MRI head coil 10 slidably in the vertical
direction.
[0067] In imaging operation, the subject H is seated on the movable
chair 40 with the movable chair 40 drawn out of the vertical magnet
apparatus 30 as shown in FIG. 6. At this time, the MRI head coil 10
is raised. Then the MRI head coil 10 is lowered to be fitted over
the head of the subject H. Subsequently the movable chair 40 is
moved into the space between the opposing surfaces of the vertical
magnet apparatus 30 as shown in FIG. 7. Thereafter, the imaging is
performed.
[0068] The above-described vertical magnet MRI apparatus 100 allows
imaging of the head to be easily done with a subject seated on a
chair.
[0069] Many widely different embodiments of the invention may be
configured without departing from the spirit and the scope of the
present invention. It should be understood that the present
invention is not limited to the specific embodiments described in
the specification, except as defined in the appended claims.
* * * * *