Method to measure tissue texture using NMR spectroscopy with VOI length in an analysis direction defined by receiver bandwidth
A method for selective sampling to assess texture of a specimen using magnetic resonance (MR) excites the specimen and refocuses to provide a sample rod within the specimen. An encoding gradient pulse is applied to induce phase wrap creating a spatial encode for a specific k-value and orientation. A low non-zero magnitude gradient is then applied acting as a time dependent phase encode to produce a time varying trajectory through 3D k-space of k-value encodes while simultaneously recording multiple sequential samples of the signal at a sequence of k-values proximate the specific k-value. The receiver bandwidth is set to delineate a length of a VOI within the rod during the data sampling. The samples are then post processed at the sequence of k values, recorded within a time span while the non-zero magnitude gradient is applied, to characterize the textural features of tissue in the VOI.
1. A method for selective sampling to assess tissue texture using magnetic resonance (MR) comprising:
transmitting a first RF pulse with a first gradient chosen for first slice selection in a specimen;
transmitting a second RF pulse with application of a second gradient chosen for slice selective refocusing in a region defined by an intersection of the first slice and a second slice defining a rod within the specimen;
applying an encoding gradient pulse to induce phase wrap to create a spatial encode for a specific k-value and orientation;
applying a low non-zero magnitude gradient having a first magnitude acting as a time dependent phase encode to produce a time varying trajectory through 3D k-space of k-value encodes;
simultaneously recording multiple sequential samples of the NMR RF signal at a sequence of k-values across a neighborhood proximate the specific k-value defined by height and pulse width of the non-zero magnitude gradient in a single excitation;
setting a first receiver bandwidth to delineate a length of a VOI within the rod during the data sampling; and
post processing the samples at the sequence of k values, recorded within a time span while the non-zero magnitude gradient is applied, to characterize the textural features of the specimen in the VOI.
2. The method as defined in claim 1 further comprising:
refocusing;
applying a low non-zero magnitude gradient with a magnitude equal to but in an opposite direction to the first magnitude;
simultaneously recording multiple sequential samples of the NMR RF signal in a reverse of the sequence of k-values to sweep back through the same range of k-values allowing implementation of phase cycling.
3. The method as defined in claim 1 further comprising selecting a center frequency of the first receiver bandwidth for positioning of the VOI along the rod.
4. The method as defined in claim 3 wherein the step of post processing includes resetting receiver bandpass for one or more additional bandwidths within the first receiver bandwidth providing one or more subsets of the VOI.
5. The method as defined in claim 3 wherein the step of post processing includes selecting one or more alternative center frequencies within the first receiver bandwidth providing one or more subsets of the VOI.
6. The method as defined in claim 3 further comprising interleaving in time domain, excitation, signal acquisition, and recovery time for the rod with additional excitation, signal acquisition, and recovery for additional non intersecting rods, to create 1D images for multiple rods.
7. A method using magnetic resonance (MR) for generating an image displaying a distribution of measured textures in a specimen comprising:
transmitting a first RF pulse with a first gradient chosen for first slice selection in a specimen;
transmitting a second RF pulse with application of a second gradient chosen for slice selective refocusing in a region defined by an intersection of the first slice and a second slice defining a rod within the specimen;
applying an encoding gradient pulse to induce phase wrap to create a spatial encode for a specific k-value and orientation;
applying a low non-zero magnitude gradient acting as a time dependent phase encode to produce a time varying trajectory through 3D k-space of k-value encodes;
setting a first receiver bandwidth to delineate a length of a first VOI within the rod during the data sampling;
simultaneously recording multiple sequential samples of the NMR RF signal at a sequence of k-values across a neighborhood proximate the specific k-value defined by height and pulse width of the non-zero magnitude gradient;
post processing the samples at the sequence of k values, recorded within a time span while the non-zero magnitude gradient was applied, iterating a pass band within the first bandwidth providing an array of VOIs for a plurality of measured or derived values; and
plotting each VOI in the array as an intensity or color on a 2D or 3D grid matching the structure of the specimen to generate an image displaying the distribution of the measured textures.
8. A method using magnetic resonance (MR) for identifying boundaries in measured textures in a specimen comprising:
transmitting a first RF pulse with a first gradient chosen for first slice selection in a specimen;
transmitting a second RF pulse with application of a second gradient chosen for slice selective refocusing in a region defined by an intersection of the first slice and a second slice defining a rod within the specimen;
applying an encoding gradient pulse to induce phase wrap to create a spatial encode for a specific k-value and orientation;
applying a low non-zero magnitude gradient acting as a time dependent phase encode to produce a time varying trajectory through 3D k-space of k-value encodes;
setting a first receiver bandwidth to delineate a length of a first VOI within the rod containing a boundary during the data sampling;
simultaneously recording multiple sequential samples of the NMR RF signal at a sequence of k-values across a neighborhood proximate the specific k-value defined by height and pulse width of the non-zero magnitude gradient; and
post processing the samples at the sequence of k values, recorded within a time span while the non-zero magnitude gradient was applied, setting the bandwidth in multiple ranges with less bandwidth than the first bandwidth thereby increasing resolution for locating the position of the boundary.