METHOD AND SYSTEM FOR MODIFYING PULSE SEQUENCES
First Claim
Patent Images
1. A method for modifying a pulse sequence, the method comprising the steps of:
- calculating timing and amplitudes of a pulse sequence;
performing a cost function analysis on desired gradient overlap regions of the pulse sequence;
determining the available encoding time based on the costliest axis per overlap region;
resetting a maximum gradient amplitude for one or more gradient axes based on the cost function analysis and/or resetting local slew rate, up to global slew rate, for one or more gradient axes based on the cost function analysis to utilize some or all of the available encoding time per overlap region;
applying a peripheral nerve stimulation (PNS) model based at least in part on the pulse sequence;
comparing an output of the PNS model to a PNS limit;
adjusting a global slew rate used to calculate the timing of the pulse sequence if the output of the PNS model exceeds the PNS limit;
recalculating timing and amplitudes of the pulse sequence based on the adjusted global slew rate and the reset maximum gradient amplitudes and/or the local slew rate; and
repeating the steps of applying, comparing, adjusting, performing, resetting, and recalculating until the output of the PNS model is within the PNS limit.
1 Assignment
0 Petitions
Accused Products
Abstract
Methods and systems are provided for modifying a pulse sequence. In one embodiment, a determination is made whether an estimated peripheral nerve stimulation (PNS) associated with a pulse sequence exceeds a PNS limit. If the estimated PNS exceeds the PNS limit, a slew rate associated with one or more axes of the pulse sequence may be reduced and the maximum gradient amplitudes for each axis of the pulse sequence may be adjusted. In one embodiment, adjustment of the maximum gradient amplitudes or local slew rate may be based upon a cost analysis performed on the pulse sequence.
-
Citations
20 Claims
-
1. A method for modifying a pulse sequence, the method comprising the steps of:
-
calculating timing and amplitudes of a pulse sequence; performing a cost function analysis on desired gradient overlap regions of the pulse sequence; determining the available encoding time based on the costliest axis per overlap region; resetting a maximum gradient amplitude for one or more gradient axes based on the cost function analysis and/or resetting local slew rate, up to global slew rate, for one or more gradient axes based on the cost function analysis to utilize some or all of the available encoding time per overlap region; applying a peripheral nerve stimulation (PNS) model based at least in part on the pulse sequence; comparing an output of the PNS model to a PNS limit; adjusting a global slew rate used to calculate the timing of the pulse sequence if the output of the PNS model exceeds the PNS limit; recalculating timing and amplitudes of the pulse sequence based on the adjusted global slew rate and the reset maximum gradient amplitudes and/or the local slew rate; and repeating the steps of applying, comparing, adjusting, performing, resetting, and recalculating until the output of the PNS model is within the PNS limit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
-
15. A magnetic resonance imaging (MRI) system, comprising:
-
an MRI scanner; scanner control circuitry capable of controlling operation of the scanner, the scanner control circuitry comprising; a memory capable of storing one or more routines for adjusting a pulse sequence; control circuitry capable of implementing the one or more routines, wherein the one or more routines, when executed, calculate timing and amplitudes for a pulse sequence, compare an estimate of peripheral nerve stimulation (PNS) associated with the pulse sequence against a PNS limit, adjust one or more of the slew rate and the maximum gradient amplitude for each axis if the estimate of PNS exceeds the PNS limit, and recalculate the timing and amplitudes for the pulse sequence until the estimate of PNS does not exceed the PNS limit; and system control circuitry capable of controlling operation of the scanner control circuitry. - View Dependent Claims (16, 17)
-
-
18. A computer-readable medium physically encoding one or more routines comprising:
-
a routine capable of calculating timing and amplitudes of a pulse sequence; a routine capable of comparing an estimate of peripheral nerve stimulation (PNS) associated with the pulse sequence against a PNS limit; a routine capable of adjusting one or more of a slew rate and a maximum gradient amplitude for each axis of the pulse sequence if the estimate of PNS exceeds the PNS limit; and a routine capable of recalculating the timing and amplitudes for the pulse sequence until the estimate of PNS does not exceed the PNS limit. - View Dependent Claims (19, 20)
-
Specification