Method for obtaining T1-weighted and T2-weighted NMR images for a plurality of selected planes in the course of a single scan
First Claim
1. A method for obtaining T1-weighted and T2-weighted NMR image data for a plurality of selected planes in an object in the course of a single scan using nuclear magnetic resonance techniques, said method comprising:
- a. positioning an object in a static homogeneous magnetic field;
b. obtaining NMR imaging data for a T1-weighted image and a T2-weighted image in a first selected plane of said object by subjecting said object to a plurality of repetitions of a repetition sequence composed of NMR excitation and magnetic field gradient pulses, each repetition sequence including (i) applying a first excitation pulse and reading out a first NMR signal produced by said first excitation pulse at a time TE1 after said first excitation pulse, and (ii) applying a second excitation pulse and reading out a second NMR signal produced by said second excitation pulse at a time TE2 after said second excitation pulse, said first and second excitation pulses each being applied in a manner so as to only excite selected nuclei in said first selected plane of said object, said first excitation pulse being applied during said repetition sequence after a recovery time interval TR1 from a preceding excitation pulse and said second excitation pulse being applied during said repetition sequence after a recovery time interval TR2 from a preceding excitation pulse, said repetition sequence being repeated at a repetition time interval Trep which is equal to the sum of said TR1 and TR2 intervals, and said plurality of repetitions of said repetition sequence being carried out in a manner to encode spatial information into a collection of said first and second NMR signals to obtain said NMR image data for a T1-weighted image and a T2-weighted image for said first selected plane, said TE1 and TR1 being selected so that said collection of said first NMR signals is representative of T1-weighted imaging data, and said TE2 and TR2 being selected so that said collection of said second NMR signals is representative of T2-weighted imaging data; and
c. carrying out step (b) set forth above for at least one additional selected plane of said object to obtain NMR imaging data for T1-weighted and T2-weighted images for said at least one additional selected plane, said repetition time interval Trep at which said repetition sequence is repeated for said at least one additional selected plane being substantially the same as said repetition time interval Trep at which said repetition sequence is repeated for said first selected plane, each of said first and second excitation pulses for each repetition of said repetition sequence for said at least one additional selected plane being applied in a manner so as to only excite selected nuclei in said at least one additional selected plane, and each step (i) for each repetition of said repetition sequence for said at least one additional selected plane being carried out during the corresponding repetition of said repetition sequence for said first selected plane at a different portion of said repetition time interval Trep for said first selected plane than said step (i) for said first selected plane, and each step (ii) for each repetition of said repetition sequence for said at least one additional selected plane being carried out during the corresponding repetition of said repetition sequence for said first selected plane at a different portion of said repetition time interval Trep for said first selected plane than said step (ii) for said first selected plane.
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Abstract
A method for obtaining in the course of a single scan T1-weighted and T2-weighted NMR imaging data for a plurality of selected planes in an object using nuclear magnetic resonance techniques. The method is accomplished by positioning an object to be imaged in a static homogeneous magnetic field and then carrying out a plurality of repetitions of a repetition sequence composed of NMR excitation and magnetic field gradient pulses for a plurality of selected planes in the object. The repetition sequences for each of the selected planes include a combination of a T1-weighted pulse sequence having a TE1 and TR1 suitable for obtaining T1-weighted NMR imaging data and a T2-weighted pulse sequence having a TE2 and TR2 suitable for obtaining T2-weighted NMR imaging data. The repetition sequence for each selected plane is repeated a plurality of times and carried out in a manner so as to encode spatial information into the collection of NMR signals. Also, the T1-weighted and T2-weighted pulse sequences for each selected plane is carried out during the recovery time intervals provided in the repetition sequence for other selected planes. In this manner, T1 and T2-weighted NMR image data for a plurality of planes are obtained in a single scan in significantly reduced time.
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Citations
32 Claims
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1. A method for obtaining T1-weighted and T2-weighted NMR image data for a plurality of selected planes in an object in the course of a single scan using nuclear magnetic resonance techniques, said method comprising:
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a. positioning an object in a static homogeneous magnetic field; b. obtaining NMR imaging data for a T1-weighted image and a T2-weighted image in a first selected plane of said object by subjecting said object to a plurality of repetitions of a repetition sequence composed of NMR excitation and magnetic field gradient pulses, each repetition sequence including (i) applying a first excitation pulse and reading out a first NMR signal produced by said first excitation pulse at a time TE1 after said first excitation pulse, and (ii) applying a second excitation pulse and reading out a second NMR signal produced by said second excitation pulse at a time TE2 after said second excitation pulse, said first and second excitation pulses each being applied in a manner so as to only excite selected nuclei in said first selected plane of said object, said first excitation pulse being applied during said repetition sequence after a recovery time interval TR1 from a preceding excitation pulse and said second excitation pulse being applied during said repetition sequence after a recovery time interval TR2 from a preceding excitation pulse, said repetition sequence being repeated at a repetition time interval Trep which is equal to the sum of said TR1 and TR2 intervals, and said plurality of repetitions of said repetition sequence being carried out in a manner to encode spatial information into a collection of said first and second NMR signals to obtain said NMR image data for a T1-weighted image and a T2-weighted image for said first selected plane, said TE1 and TR1 being selected so that said collection of said first NMR signals is representative of T1-weighted imaging data, and said TE2 and TR2 being selected so that said collection of said second NMR signals is representative of T2-weighted imaging data; and c. carrying out step (b) set forth above for at least one additional selected plane of said object to obtain NMR imaging data for T1-weighted and T2-weighted images for said at least one additional selected plane, said repetition time interval Trep at which said repetition sequence is repeated for said at least one additional selected plane being substantially the same as said repetition time interval Trep at which said repetition sequence is repeated for said first selected plane, each of said first and second excitation pulses for each repetition of said repetition sequence for said at least one additional selected plane being applied in a manner so as to only excite selected nuclei in said at least one additional selected plane, and each step (i) for each repetition of said repetition sequence for said at least one additional selected plane being carried out during the corresponding repetition of said repetition sequence for said first selected plane at a different portion of said repetition time interval Trep for said first selected plane than said step (i) for said first selected plane, and each step (ii) for each repetition of said repetition sequence for said at least one additional selected plane being carried out during the corresponding repetition of said repetition sequence for said first selected plane at a different portion of said repetition time interval Trep for said first selected plane than said step (ii) for said first selected plane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for obtaining T1-weighted and T2-weighted NMR image data for at least two selected planes in an object in a single scan using nuclear magnetic resonance techniques, said method comprising:
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positioning an object in an NMR imaging apparatus which includes means for generating a magnetic field, means for exciting selected nuclei to generate NMR signals and for reading of such NMR signals to provide a collection of NMR signals from selected regions of an object placed in said NMR imgaging apparatus, and means for obtaining NMR imaging data from said collection of NMR signals; conducting a plurality of NMR sampling operations to obtain NMR imaging data from a first selected plane of said object, said step of conducting said sampling operations for said first plane being commenced at a first time during the course of a single scan and being continued substantially throughout said single scan so as to obtain NMR imaging data for producing T1-weighted and T2-weighted images for said first selected plane of said object; conducting a plurality of NMR sampling operations to obtain NMR imaging data from a second selected plane of said object which is different from said first selected plane, said step of conducting said sampling operations for said second selected plane being commenced at a second time during the course of said single scan which is later than said first time but prior to completion of said step of conducting said sampling operations for said first selected plane, and said step of conducting said NMR sampling operations for said second selected plane being continued substantially throughout said single scan to obtain NMR imaging data for producing T1-weighted and T2-weighted images for said second selected plane; each of said plurality of NMR sampling operations including first and second sets of NMR excitation and reading operations, one of said first and second sets of NMR excitation and reading operations being performed in a manner to provide T1-weighted NMR imaging data and the other of said first and second sets of excitation and reading operations being performed in a manner to provide T2-weighted imaging data; and each of said first set of operations being performed at a different time during the course of said single scan than each other of said first set of operations and each of said second set of operations, and each of said second set of operations being performed at a different time during the course of said single scan than each other of said second set of operations and each of said first set of operations. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A method for obtaining first and second NMR imaging data for at least two selected planes in an object in a single scan using nuclear magnetic resonance techniques, said method comprising:
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positioning an object in an NMR imaging apparatus which includes means for generating a magnetic field, means for exciting selected nuclei to generate NMR signals and for reading of such NMR signals to provide a collection of NMR signals from selected regions of an object placed in said NMR imaging apparatus, and means for obtaining NMR imaging data from said collection of NMR signals; conducting a plurality of NMR sampling operations to obtain NMR imaging data from a first selected plane of said object, said step of conducting said sampling operations for said first plane being commenced at a first time during the course of a single scan and being continued substantially throughout said single scan so as to obtain NMR imaging data for producing first and second images for said first selected plane of said object; conducting a plurality of NMR sampling operations to obtain NMR imaging data from a second selected plane of said object which is different from said first selected plane, said step of conducting said sampling operations for said second selected plane being commenced at a second time during the course of said single scan which is later than said first time but prior to completion of said step of conducting said sampling operations for said first selected plane, and said step of conducting said NMR sampling operations for said second selected plane being continued substantially throughout said single scan to obtain NMR imaging data for producing first and second images for said second selected plane; each of said plurality of NMR sampling operations including a first NMR excitation operation followed by a first NMR reading operation and a second NMR excitation operation followed by a second NMR reading operation, said first NMR excitation operations being performed at a first interval of time after a preceding NMR excitation operation to provide first NMR imaging data for producing said first images and said second NMR excitation operation being performed at a second interval of time after a preceding first NMR excitation operation to provide second NMR imaging data for producing said second images, said first interval of time being different from said second interval of time, whereby the overall time for obtaining said first and second NMR imaging data for said first and second selected planes is minimized.
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Specification