Artificially structured unit cells providing localized B1 magnetic fields for MRI and NMR devices

Patent metadata

Field	Value
Publication number	US-9927505-B2
Application number	US-201414334398-A
Country	US
Kind code	B2
Filing date	Jul 17, 2014
Priority date	Jul 17, 2014
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

Described embodiments include a system, apparatus, and method. An apparatus includes an array of at least two groups of at least two artificially structured electromagnetic unit cells. Each group of the at least two groups configured to be respectively linearly arranged with respect to the z-axis of the bore of MRI or NMR device. Each group of the at least two groups of artificially structured electromagnetic unit cells configured to transform an incident pulse of radiofrequency electromagnetic waves into a pulse of radiofrequency magnetic field B 1 orientated transverse to a segment of the z-axis and spatially proximate to the group. The apparatus includes a radiofrequency electromagnetic wave conducting structure configured to selectably distribute a received pulse of radiofrequency electromagnetic waves to a group of the at least two groups.

First claim

What is claimed is:

1. An apparatus comprising:
a radiofrequency electromagnetic wave conducting structure configured to selectively distribute a received pulse of radiofrequency electromagnetic waves as an incident pulse of radiofrequency electromagnetic waves to a group of at least two groups of artificially structured sub-wavelength electromagnetic unit cells;
the at least two groups of at least two artificially structured sub-wavelength electromagnetic unit cells,
each group of the at least two groups configured to be respectively linearly arranged with respect to a z-axis of a bore of a magnetic resonant imaging or a nuclear magnetic resonant device,
each group of the at least two groups of artificially structured sub-wavelength electromagnetic unit cells configured to transform the incident pulse of radiofrequency electromagnetic waves into a pulse of radiofrequency magnetic field B 1 orientated transverse to a segment of the z-axis (hereafter “transverse segment”) and spatially proximate to the group.

2. A system comprising:
a radiofrequency electromagnetic wave conducting structure configured to distribute a pulse of radiofrequency electromagnetic waves as an incident pulse of radiofrequency electromagnetic waves to a group of at least two selectable groups in response to a B 1 localization control signal;
an array of the at least two selectable groups,
each group of the at least two selectable groups including at least two artificially structured electromagnetic unit cells and configured to be respectively linearly arranged with respect to a z-axis of a bore of a magnetic resonant imaging or a nuclear magnetic resonant device, and
each group of the at least two artificially structured electromagnetic unit cells respectively configured to transform the incident pulse of radiofrequency electromagnetic waves into a pulse of radiofrequency magnetic field B 1 orientated transverse to a segment of a z-axis (hereafter “transverse segment) and spatially proximate to the group; and
a control circuit configured to generate the B 1 localization control signal defining a respective power distribution of a particular incident pulse of radiofrequency electromagnetic waves to each group of the at least two selectable groups, the respective power distribution collectively defining a particular pulse of radiofrequency magnetic field B 1 localized to a selected arbitrary examination segment transverse to the z-axis and within an examination region of the bore, the localized magnetic field B 1 having an intensity sufficient to excite a detectable magnetic resonance in magnetically active nuclei located within the selected arbitrary examination segment,
wherein the localized pulse of the radiofrequency magnetic field B 1 produces a quasi-focused radiofrequency magnetic field B 1 localized to include the selected arbitrary examination segment.

3. A system comprising:
a radiofrequency electromagnetic wave conducting structure configured to distribute a pulse of radiofrequency electromagnetic waves as an incident pulse of radiofrequency electromagnetic waves to a group of at least two selectable groups of artificially structured sub-wavelength electromagnetic unit cells in response to a B 1 localization control signal;
an array of the at least two selectable groups of artificially structured sub-wavelength electromagnetic unit cells,
each group of the at least two selectable groups including at least two artificially structured sub-wavelength electromagnetic unit cells and configured to be respectively linearly arranged with respect to a z-axis of a bore of a magnetic resonant imaging or a nuclear magnetic resonant device, and
each group of the at least two artificially structured sub-wavelength electromagnetic unit cells respectively configured to transform the incident pulse of radiofrequency electromagnetic waves into a pulse of radiofrequency magnetic field B 1 orientated transverse to a segment of a z-axis (hereafter “transverse segment) and spatially proximate to the group; and
a control circuit configured to generate the B 1 localization control signal defining a respective power distribution of a particular incident pulse of radiofrequency electromagnetic waves to each group of the at least two selectable groups of artificially structured sub-wavelength electromagnetic unit cells, the respective power distribution collectively defining a particular pulse of radiofrequency magnetic field B 1 localized to a selected arbitrary examination segment transverse to the z-axis and within an examination region of the bore, the localized magnetic field B 1 having an intensity sufficient to excite a detectable magnetic resonance in magnetically active nuclei located within the selected arbitrary examination segment.

4. The system of claim 3 , wherein each group of the at least two selectable groups is respectively individually accessible or controllable independent of their respective location or sequence in the array.

5. The system of claim 3 , wherein the selected arbitrary examination segment includes within its z-axis boundaries a transverse slice of the examination region selected for examination.

6. The system of claim 3 , further comprising:
a receiver configured to receive data indicative of a location along the z-axis of the transverse slice selected for examination.

7. The system of claim 3 , wherein the localized pulse of the radiofrequency magnetic field B 1 includes a first radiofrequency electric field E 1 intensity in the selected arbitrary examination segment and includes a second radiofrequency electric field E 2 intensity in a second arbitrary transverse segment of the examination region, the second radiofrequency electric field intensity less than the first radiofrequency electric field intensity.

8. The system of claim 7 , wherein the second radiofrequency electric field intensity is less than 66% of the first radiofrequency electric field intensity.

9. The system of claim 3 , wherein the localized pulse of the radiofrequency magnetic field B 1 includes (i) a first radiofrequency electric field E 1 intensity in the selected arbitrary examination segment, (ii) a second radiofrequency electric field E 2 intensity in a second arbitrary transverse segment of the examination region abutting the selected arbitrary transverse segment, and (iii) a third radiofrequency electric field E 3 intensity in a third arbitrary transverse segment of the examination region abutting the selected arbitrary transverse segment and positioned opposite to the second arbitrary transverse segment, the second and third radiofrequency electric field intensities each less than the first radiofrequency electric field intensity.

10. The system of claim 3 , wherein the localized pulse of the radiofrequency magnetic field B 1 is configured to produce a first specific absorption rate (SAR) in the selected arbitrary examination segment and to produce a second SAR in another arbitrary transverse segment of the examination region, the second SAR less than the first SAR.

11. The system of claim 10 , wherein the second SAR is less than 66% of the first SAR.

12. The system of claim 3 , wherein the respective power distribution further includes a respective power distribution collectively defining a particular pulse of radiofrequency magnetic field B 1 producing a minimized specific absorption rate (SAR) in the selected arbitrary examination segment.

13. The system of claim 12 , wherein the defined particular pulse of radiofrequency magnetic field B 1 is configured in response to a model-based estimation of the localized pulse respective power distribution providing the m

Assignees

• Elwha Llc

Inventors

• Driscoll Tom
• Smith David R
• Urzhumov Yaroslav A

Classifications

• G01R33/3415

  comprising arrays of sub-coils {, i.e. phased-array coils with flexible receiver channels} · CPC title

• G01R33/3607

  RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal · CPC title

• G01R33/345

  of waveguide type (G01R33/343 takes precedence) · CPC title

• G01R33/3614

  RF power amplifiers · CPC title

• G01R33/36 Primary

  Electrical details, e.g. matching or coupling of the coil to the receiver · CPC title