Passive MRI-guided tracking of metallic objects using artifact-reduced imaging with selective excitation

Patent metadata

Field	Value
Publication number	US-10139459-B2
Application number	US-201715474510-A
Country	US
Kind code	B2
Filing date	Mar 30, 2017
Priority date	Mar 30, 2017
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A method using 2D multi-spectral imaging (2DMSI) for MRI imaging of a metallic object (such as a biopsy needle) and region surrounding the metallic object within an imaging field of view of an MRI apparatus includes segmenting the imaging field-of-view into spatial-spectral bins, where the segmenting is based on off-resonance frequency induced by the metallic object and slice location; selectively exciting each frequency bin of the spatial-spectral bins by inverting a slice selection gradient between excitation and refocusing pulses; performing repeated acquisition with different radiofrequency modulations to produce acquired images of adjacent bins; composing a 2DMSI image by root-sum-of-squares combination of the acquired images of adjacent bins; and highlighting in the 2DMSI image an area of furthest off-resonance bins based on 2DMSI off-resonance information by thresholding image intensity in frequency bins, thereby indicating a contour of the metallic object.

First claim

The invention claimed is:

1. A method using 2D multi-spectral imaging (2DMSI) for MRI imaging of a metallic object and region surrounding the metallic object within an imaging field of view of an MRI apparatus, the method comprising:
segmenting the imaging field-of-view into spatial-spectral bins, where the segmenting is based on off-resonance frequency induced by the metallic object and the slice location;
selectively exciting each spatial-spectral bin by inverting a slice selection gradient between excitation and refocusing pulses;
performing repeated acquisition with different radiofrequency modulations to produce acquired images of adjacent frequency bins;
composing a 2DMSI image by combination of the acquired images of adjacent bins;
highlighting in the 2DMSI image an area of off-resonance bins based on 2DMSI off-resonance information by thresholding image intensity in frequency bins, thereby indicating a contour of the metallic object.

2. The method of claim 1 wherein highlighting in the 2DMSI image comprises color-coding the image area based on the sign of the off-resonance frequency of the bin.

3. The method of claim 1 wherein the method is continuously repeated to acquire a series of 2DMSI images.

4. The method of claim 1 further comprising changing a contrast of the 2DMSI image by selectively inverting each bin with an inversion pulse.

5. The method of claim 1 wherein only a subset of bins is acquired.

6. The method of claim 5 wherein the subset of bins comprises the on-resonant bin and the furthest off-resonance bins.

7. The method of claim 5 wherein the subset of bins comprises only the furthest off-resonance bins and where the information is used to highlight the corresponding image areas in a conventionally acquired MRI image.

8. The method of claim 1 wherein parallel imaging is used to accelerate the data acquisition.

Assignees

• Univ Leland Stanford Junior

Inventors

• Weber Hans
• Hargreaves Brian A

Classifications

• G01R33/4833

  using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices · CPC title

• G01R33/287 Primary

  involving active visualization of interventional instruments, e.g. using active tracking RF coils or coils for intentionally creating magnetic field inhomogeneities · CPC title

• G01R33/5611

  Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE (structural details of arrays of sub-coils G01R33/3415) · CPC title

• G01R33/286 Primary

  involving passive visualization of interventional instruments, i.e. making the instrument visible as part of the normal MR process · CPC title

• G01R33/56536

  due to magnetic susceptibility variations · CPC title