Magnetic resonance imaging device
First Claim
1. A method of measuring a temperature distribution of an object to be examined based on nuclear magnetic resonance signals emitted from the object comprising the steps of:
- a) forming image data from the nuclear magnetic resonance signals measured at time t1;
b) extracting an object part from the image data;
c) calculating a spatial phase distribution from the extracted image data;
d) calculating a spatial temperature distribution based on the spatial base distribution;
e) performing steps from a) to d) for nuclear magnetic resonance signals measured at time t2 and calculating a spatial temperature distribution at time t2; and
f) subtracting the spatial temperature distributions calculated for measurements at t1 and t2 and calculating a temperature change distribution;
wherein the step c) includes a step of correcting arctangent aliasing produced in the spatial phase distribution; and
wherein, in the step of correcting arctangent aliasing, a point in a region in which the temperature has not changed is selected as a base point of phase value.
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Accused Products
Abstract
An MRI apparatus and method in which image data is produced using NMR signals obtained in plural measurements performed at different times respectively. Data is calculated indicating temperature distribution within the object for image data of each measurement time and spatial discontinuity of the calculated temperature distribution data is corrected. Temperature change distribution within the object between different measurement times is calculated by subtracting the corrected temperature distribution data of each measurement time, and the calculated temperature change distribution is transformed to indicative data for supply to a display for display.
29 Citations
21 Claims
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1. A method of measuring a temperature distribution of an object to be examined based on nuclear magnetic resonance signals emitted from the object comprising the steps of:
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a) forming image data from the nuclear magnetic resonance signals measured at time t1;
b) extracting an object part from the image data;
c) calculating a spatial phase distribution from the extracted image data;
d) calculating a spatial temperature distribution based on the spatial base distribution;
e) performing steps from a) to d) for nuclear magnetic resonance signals measured at time t2 and calculating a spatial temperature distribution at time t2; and
f) subtracting the spatial temperature distributions calculated for measurements at t1 and t2 and calculating a temperature change distribution;
wherein the step c) includes a step of correcting arctangent aliasing produced in the spatial phase distribution; and
wherein, in the step of correcting arctangent aliasing, a point in a region in which the temperature has not changed is selected as a base point of phase value.
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2. A method of measuring a temperature distribution of an object to be examined based on nuclear magnetic resonance signals emitted from the object comprising the steps of:
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a) forming image data from the nuclear magnetic resonance signals measured at different times t1 and t2;
b) obtaining image data difference by performing subtraction on two image date after extracting an object part from each image data;
c) calculating a spatial phase distribution from the image data difference;
d) calculating a spatial temperature distribution representing temperature changes between the time t1 and t2 based on the spatial phase distribution;
wherein the step c) includes a step of correcting arctangent aliasing produced in the spatial phase distribution; and
wherein, in the step of correcting arctangent aliasing, a point in a region in which the temperature has not changed is selected as a base point of phase value.
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3. A magnetic resonance imaging (MRI) apparatus comprising means for imparting a static magnetic field to an object to be examined, means for applying a plurality of gradient magnetic fields to the object, means for generating radio-frequency pulses to cause magnetic resonance in atomic nuclei of atoms constituting the object, detecting means for measuring nuclear magnetic resonance (NMR) signals from the object, operating means for performing operations on the NMR signals to produce temperature information of the object, and display means for displaying a result of the operations,
wherein the operating means comprises means for producing image data using the NMR signals obtained in plural measurements performed at different times respectively, means for calculating data indicating temperature distribution within the object for image data of each measurement time, means for correcting spatial discontinuity of the calculated temperature distribution data, means for calculating temperature change distribution within the object between different measurement times by subtracting the corrected temperature distribution data of each measurement time, and means for transforming the calculated temperature change distribution to indicative data to supply to the display means.
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7. A magnetic resonance imaging (MRI) apparatus comprising means for imparting a static magnetic field to an object to be examined, means for applying a plurality of gradient magnetic fields to the object, means for generating radio-frequency pulses to cause magnetic resonance in atomic nuclei of atoms constituting the object, detecting means for measuring nuclear magnetic resonance (NMR) signals from the object, operating means for performing operations on the NMR signals to produce temperature information of the object, and display means for displaying a result of the operations,
wherein the operating means comprises means for producing a complex image using the NMR signals obtained in plural measurements performed at different times respectively, means for extracting an object part from each complex image, means for calculating spatial phase distribution for each complex image, means for correcting arctangent aliasing produced in the spatial phase distribution, means for calculating temperature distribution data based on the corrected spatial phase distribution, means for calculating temperature change distribution from the difference between the calculated temperature distribution data, and means for forming images of the temperature change distribution.
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16. A method of measuring a temperature distribution within an object to be examined based on nuclear magnetic resonance (NMR) signals emitted from the object comprising the steps of:
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a) forming image data from the NMR signals measured at time t1;
b) extracting an object part from the image data;
c) calculating a spatial phase distribution from the extracted image data;
d) correcting arctangent aliasing generated in the spatial phase distribution;
e) calculating a temperature distribution based on the corrected spatial phase distribution;
f) performing steps from a) to e) for NMR signals measured at time t2 and calculating a temperature distribution at time t2;
g) subtracting the temperature distributions calculated for measurements at t1 and t2 to produce a temperature change distribution of the object part; and
h) displaying the temperature change distribution on a display device as an image. - View Dependent Claims (17, 18, 19)
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20. A method of measuring a temperature distribution of an object to be examined based on nuclear magnetic resonance (NMR) signals emitted from the object comprising the steps of:
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a) forming a first image data from the NMR signals measured at time t1;
b) forming a second image data from the NMR signals measured at time t2;
c) subtracting the first image data from the second image data to produce a difference image data;
d) calculating a spatial phase distribution from the difference image data;
e) correcting arctangent aliasing generated in the spatial phase distribution;
f) calculating a temperature change distribution within the object between the time t1 and time t2 based on the corrected spatial phase distribution; and
g) displaying the temperature change distribution as an image.
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21. A method of measuring and displaying a temperature distribution of an object to be examined based on nuclear magnetic resonance (NMR) signals emitted from the object comprising the steps of:
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a) forming image data from the NMR signals measured from the object;
b) calculating a spatial phase distribution of the image data;
c) correcting arctangent aliasing generated in the spatial phase distribution;
d) calculating a temperature distribution within the object based on the corrected spatial phase distribution; and
e) displaying the temperature distribution as an image.
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Specification