Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-02-06
2001-11-20
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C324S309000, C324S318000
Reexamination Certificate
active
06321108
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
An example of a conventional MRI head coil is shown in FIG.
1
.
The MRI head coil
70
has a cylindrical shape containing an imaging space therein for accommodating the head of a subject H.
The conventional MRI head coil
70
has the following problems:
(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.
(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
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.
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.
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 feeling. 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.
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.
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.
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 coils are pivotally attached to the quadrature coil, and the pair of opposing coils is allowed to be opened in an inverted V-like shape.
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.
The MRI coil of the present invention may be used as, for example, a knee coil for imaging the knee.
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.
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.
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.
REFERENCES:
patent: Re. 32619 (1988-03-01), Damadian
patent: 4534358 (1985-08-01), Young
patent: 5390672 (1995-02-01), Jones
patent: 5519321 (1996-05-01), Hagen et al.
patent: 6011396 (2000-01-01), Eckels et al.
Furuta Osamu
Hayaklawa Kazuhiko
GE Yokogawa Medical Systems Limited
Kojima Moonray
Smith Ruth S.
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