Local SAR Constrained Parallel Transmission RF Pulse in Magnetic Resonance Imaging
First Claim
1. A method of designing a parallel transmission radio frequency (RF) pulse for a magnetic resonance imaging (MRI) system, the method comprising:
- compressing a model for a subject to be scanned by the MRI system into a plurality of virtual observation points within the model based on comparisons of peak sensitivity to local specific absorption rate (SAR); and
defining, with a processor, the parallel transmission RF pulse for antenna of the MRI system that minimizes a weighted average of local SAR values with an iterative procedure that optimizes a set of weighting factors for the plurality of virtual observation points to maximize the minimized weighted average.
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Abstract
A method of designing a parallel transmission radio frequency (RF) pulse for a magnetic resonance imaging (MRI) system includes compressing a model for a subject to be scanned by the MRI system into a plurality of virtual observation points within the model based on comparisons of peak sensitivity to local specific absorption rate (SAR), and defining the parallel transmission RF pulse that minimizes a weighted average of local SAR values with an iterative procedure that optimizes a set of weighting factors for the plurality of virtual observation points to maximize the minimized weighted average.
261 Citations
20 Claims
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1. A method of designing a parallel transmission radio frequency (RF) pulse for a magnetic resonance imaging (MRI) system, the method comprising:
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compressing a model for a subject to be scanned by the MRI system into a plurality of virtual observation points within the model based on comparisons of peak sensitivity to local specific absorption rate (SAR); and defining, with a processor, the parallel transmission RF pulse for antenna of the MRI system that minimizes a weighted average of local SAR values with an iterative procedure that optimizes a set of weighting factors for the plurality of virtual observation points to maximize the minimized weighted average. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of applying a parallel transmission radio frequency (RF) pulse in a magnetic resonance imaging (MRI) system, the model being defined via a number of voxels, the method comprising:
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calculating a spatial matrix for each voxel of a model for a subject to be scanned by the MRI system, the spatial matrix being indicative of absorption sensitivity; designating a subset of the voxels as a plurality of virtual observation points for the model by iteratively evaluating the spatial matrices of the voxels to determine whether the absorption sensitivity of a respective one of the voxels is upper bounded by a global SAR-based overestimation of the absorption sensitivity of at least one previously evaluated voxel; defining the parallel transmission RF pulse that minimizes a weighted average of local specific absorption rate (SAR) over the virtual observation points with an iterative procedure that optimizes a set of weighting factors for the weighted average to maximize the minimized weighted average of local SAR over the virtual observation points; and transmitting the defined parallel transmission RF pulse. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A magnetic resonance imaging (MRI) system comprising:
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a data storage unit to store calibration data for a model for a subject to be scanned, the model having a number of voxels; a coil array for transmitting a parallel transmission radio frequency (RF) pulse to the subject; and a control system in communication with the data storage unit and the coil array; wherein the control system is configured to design the parallel transmission RF pulse to control local specific absorption rate (SAR) based on the model, a model compression in which the model is compressed into a plurality of virtual observation points within the model based on comparisons of peak sensitivity to SAR, and an iterative procedure applied to pulses configured to minimize a weighted average of local SAR values, the iterative procedure being configured to optimize a set of weighting factors for the plurality of virtual observation points to maximize the minimized weighted average. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification