Magnetic resonance apparatus and method for determining the location of a positionable object in a subject
First Claim
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1. A method for determining a location of a positionable object in an examination subject by magnetic resonance comprising the steps of:
- (a) disposing an examination subject in magnetic field gradients while acquiring magnetic resonance signals comprising a reference image of at least one slice of the examination subject using a whole body antenna, and frequency coding said magnetic resonance signals in a first direction with alternating signs and phase coding said magnetic resonance signals in a second direction with alternating signs;
(b) attaching at least one radio-frequency reception coil having a small sensitivity region to an object whose position is to be determined and acquiring magnetic resonance signals, in the presence of said magnetic field gradients while said reference image is acquired, from said radio-frequency reception coil, said magnetic resonance signals having a frequency/phase spectrum associated therewith, and identifying a current position of said object from said frequency/phase spectrum of said magnetic resonance signals;
(c) defining a new slice position dependent on said current position of said object and updating said reference image, to obtain an updated reference image only by employing said new slice position in said updated reference image; and
(d) multiply repeating steps (a), (b), and (c).
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Abstract
In a method for the location determination of a positionable object in an examination subject by means of magnetic resonance and apparatus for the implementation of the method a reference image is acquired from at least one slice of the examination subject. The current position of the subject is determined by at least one radio-frequency reception coil attached to the object. A slice position in which the reference image is updated is determined on the basis of this current position.
80 Citations
20 Claims
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1. A method for determining a location of a positionable object in an examination subject by magnetic resonance comprising the steps of:
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(a) disposing an examination subject in magnetic field gradients while acquiring magnetic resonance signals comprising a reference image of at least one slice of the examination subject using a whole body antenna, and frequency coding said magnetic resonance signals in a first direction with alternating signs and phase coding said magnetic resonance signals in a second direction with alternating signs; (b) attaching at least one radio-frequency reception coil having a small sensitivity region to an object whose position is to be determined and acquiring magnetic resonance signals, in the presence of said magnetic field gradients while said reference image is acquired, from said radio-frequency reception coil, said magnetic resonance signals having a frequency/phase spectrum associated therewith, and identifying a current position of said object from said frequency/phase spectrum of said magnetic resonance signals; (c) defining a new slice position dependent on said current position of said object and updating said reference image, to obtain an updated reference image only by employing said new slice position in said updated reference image; and (d) multiply repeating steps (a), (b), and (c). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for determining a location of a positionable object in an examination subject by magnetic resonance comprising:
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a whole body antenna; means for generating magnetic gradient fields; means for acquiring nuclear magnetic resonance signals from the whole body antenna comprising a reference image of at least one slice of an examination subject disposed in said magnetic gradient fields, and for phase coding said magnetic resonance signals in a first direction with alternating signs and for phase coding said magnetic resonance signals in a second direction with alternating signs; at least one radio-frequency reception coil having a small sensitivity region, attached to an object whose position is to be determined; means for acquiring magnetic resonance signals, in the presence of said magnetic field gradients, from said radio-frequency reception coil while said reference image is acquired, said magnetic resonance signals having a frequency/phase spectrum associated therewith, and for identifying a current position of said object from said frequency/phase spectrum of said magnetic resonance signals; means for defining successive, respective new slice positions dependent on successive current positions of said object and for successively updating said reference image, to obtain an update reference images only by incorporating each new slice position in said respective updated images. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification