1. A magnetic resonance method comprising:
performing magnetic resonance imaging in a main magnetic field;
measuring spatial data corresponding to the main magnetic field; and
determining at least one main magnetic field nonuniformity parameter from the spatial data corresponding to the main magnetic field; wherein:
the measuring and determining are performed concurrently with the performing of magnetic resonance imaging.
2. The magnetic resonance method as set forth in claim 1, wherein the performing of magnetic resonance imaging comprises:
acquiring a magnetic resonance imaging repetition, frame or dynamic, the acquiring including acquiring volumetric magnetic resonance imaging data;
repeating the acquiring; and
interspersing the measuring between or concurrently with repetitions of the acquiring.
3. The magnetic resonance method as set forth in claim 1, further comprising:
acquiring a magnetic resonance imaging repetition, frame or dynamic, the acquiring including acquiring volumetric magnetic resonance imaging data;
repeating the acquiring;
computing a main magnetic field shim current based on the determined at least one main magnetic field nonuniformity parameter; and
applying the computed main magnetic field shim current during the acquiring of a subsequent magnetic resonance imaging repetition, frame or dynamic.
4. The magnetic resonance method as set forth in claim 1, further comprising:
compensating for a change in the main magnetic field by adjusting the main magnetic field based on the at least one main magnetic field nonuniformity parameter.
5. The magnetic resonance method as set forth in claim 1, further comprising:
compensating for a change in the main magnetic field by adjusting an image reconstruction of imaging data collected by the performing of magnetic resonance imaging based on the at least one main magnetic field nonuniformity parameter.
6. The magnetic resonance method as set forth in claim 1, wherein the measuring and determining comprise:
reading at least two gradient echoes using magnetic field gradients imposed along a selected direction; and
computing a nonuniformity of the main magnetic field along the selected direction from the at least two gradient echoes.
7. The magnetic resonance method as set forth in claim 6, further comprising:
repeating the reading and computing for a plurality of selected directions; and
mapping the main magnetic field based on the computed nonuniformities along the selected directions.
8. The magnetic resonance method as set forth in claim 6, wherein the reading of at least two gradient echoes comprises:
applying a balanced magnetic field gradient along the selected direction, the balanced magnetic field gradient having at least two lobes of same polarity separated by a lobe of opposite polarity; and
reading the at least two gradient echoes during the two lobes of same polarity.
9. The magnetic resonance method as set forth in claim 6, wherein the reading of at least two gradient echoes comprises:
prior to the reading of the at least two gradient echoes, applying a radio frequency excitation.
10. The magnetic resonance method as set forth in claim 9, wherein the applying of a radio frequency excitation comprises:
applying a radio frequency excitation having a low flip angle.
11. The magnetic resonance method as set forth in claim 9, further including:
reading at least two other gradient echoes using magnetic field gradients imposed along a different direction; and
wherein the readings along the selected direction and along the different direction detect magnetic resonance excited by the same said applied radio frequency excitation.
12. The magnetic resonance method as set forth in claim 6, wherein the computing comprises:
Fourier transforming each gradient echo to reconstruct a projection along the selected direction; and
computing a complex phase difference between the projections reconstructed from the at least two gradient echoes, the nonuniformity of the main magnetic field along the selected direction corresponding to the complex phase difference.
13. The magnetic resonance method as set forth in claim 12, wherein the reading of at least two gradient echoes using magnetic field gradients imposed along a selected direction comprises:
imposing the multi-lobe magnetic field gradient includes at least five lobes along the selected direction, the multi-lobe magnetic field gradient including a \u2212a:+b:\u2212b:+b:\u2212a lobe area ratio where a and b represent gradient lobe areas and the positive and negative signs represent gradient lobe polarities; and
reading the at least two gradient echoes during the two +b lobes.
14. The magnetic resonance method as set forth in claim 1, wherein:
the measuring of spatial data corresponding to the main magnetic field includes reading coils of an array of spatially separated coils.
15. The magnetic resonance method as set forth in claim 14, wherein:
the performing of magnetic resonance imaging includes imaging using the array of spatially separated coils, the spatial data corresponding to the main magnetic field being extracted from the magnetic resonance imaging data.
16. The magnetic resonance method as set forth in claim 1, wherein the measuring of spatial data corresponding to a main magnetic field comprises:
exciting and sampling magnetic resonance at a resonance frequency different from the resonance frequency used in performing the magnetic resonance imaging; and
deriving spatial data corresponding to the main magnetic field from the sampled magnetic resonance.
17. The magnetic resonance method as set forth in claim 16, wherein the exciting and sampling of magnetic resonance at a resonance frequency different from the resonance frequency used in performing the magnetic resonance imaging is performed during the magnetic resonance imaging and further comprises:
sampling magnetic resonance at the resonance frequency different from the resonance frequency used in performing the magnetic resonance imaging at a plurality of spatial locations.
18. The magnetic resonance method as set forth in claim 1, wherein the measuring of spatial data corresponding to a main magnetic field comprises:
exciting and sampling magnetic resonance in an imaging subject of the magnetic resonance imaging; and
deriving spatial data corresponding to the main magnetic field from the sampled magnetic resonance.
19. A magnetic resonance imaging apparatus comprising:
a means for performing magnetic resonance imaging in a main magnetic field;
a means for measuring spatial data corresponding to the main magnetic field; and
a means for determining at least one main magnetic field nonuniformity parameter from the spatial data corresponding to the main magnetic field.
20. The magnetic resonance imaging apparatus as set forth in claim 19, wherein the measuring means comprises:
a plurality of magnetic field sensors disposed in the main magnetic field, the plurality of magnetic field sensors operating independently from the imaging means.
21. The magnetic resonance imaging apparatus as set forth in claim 20, wherein the magnetic field sensors are selected from a group consisting of:
Hall effect magnetic field sensors,
resonance-based active magnetic field sensors operating at a resonance frequency different from a magnetic resonance frequency of the acquiring means, and
a plurality of field-lock coils tuned to a magnetic resonance frequency of the acquiring means.
22. The magnetic resonance imaging apparatus as set forth in claim 19, wherein the measuring means comprises:
one or more radio frequency receive coils of the imaging means.
23. The magnetic resonance imaging apparatus as set forth in claim 19, further comprising:
a ferromagnetic structure disposed in the main magnetic field, the ferromagnetic structure inducing changes in the main magnetic field over time responsive to the magnetic resonance imaging.
24. The magnetic resonance imaging apparatus as set forth in claim 19, further comprising:
a means for adjusting the main magnetic field during the magnetic resonance imaging based on the at least one main magnetic field nonuniformity parameter.
25. The magnetic resonance imaging apparatus as set forth in claim 19, further comprising:
a means for reconstructing imaging data acquired by the means for performing magnetic resonance imaging, the reconstructing means adjusting the reconstructing based on the at least one main magnetic field nonuniformity parameter.
26. A magnetic resonance imaging apparatus comprising:
a magnetic resonance imaging scanner performing magnetic resonance imaging, the scanner including:
a main magnet generating a main magnetic field,
magnetic field gradient coils, and
at least one radio frequency antenna;
at least one magnetic field sensor measuring spatial data corresponding to the main magnetic field; and
a processor programmed to perform the method of claim 1 to determine the nonuniformity parameter.
27. The magnetic resonance imaging apparatus as set forth in claim 26, further comprising:
shim coils for shimming the main magnetic field; and
a reconstruction processors;
the processor being operatively connected with at least one of the shim coils and the reconstruction processor to adjust at least one of shim coil currents and resonance data reconstruction in accordance with the nonuniformity parameter.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of commissioning networks of wireless device, the method comprising:
generating a device query, wherein the device query comprises a request for device information;
broadcasting the device query at a first power level, wherein the first power level is a minimum power level;
receiving a first query response comprising first device information for a first wireless device within a network of wireless devices, wherein the first device information identifies an aspect of the first wireless device;
receiving a second query response comprising second device information for a second wireless device within the network, wherein the second device information identifies an aspect of the second wireless device;
generating a first wink message, wherein the first wink message comprises instructions for a receiving device to provide a visible indicator of receipt of the first wink message, wherein the receiving device is one of the wireless devices;
selecting the first wireless device;
transmitting the first wink message to the first wireless device;
receiving location information for the first wireless device from a location database, wherein the location information identifies the location of the first device; and
storing location associating information with the first wireless device in response to the visual indicator.
2. The method of claim 1, further comprising:
selecting the second wireless device;
generating a second wink message, wherein the second wink message comprises instructions for the receiving device to provide a visible indicator of receipt of the second wink message;
transmitting the second wink message to the second wireless device;
receiving location information from the location database for the second wireless device; and
associating the location information with the second wireless device.
3. The method of claim 1, wherein the first device information uniquely identifies the first device.
4. The method of claim 1, wherein the first device information identifies a function of the first device.
5. The method of claim 1, wherein the device query is broadcast via a directional antenna.
6. The method of claim 1, further comprising rebroadcasting the device query at a second power based on the received query responses.
7. A commissioning devices comprising:
an antenna configured to broadcast and receive information;
a processor, wherein the processor is configured to:
generate a device query, wherein the device query comprises a request for device information;
broadcast the device query at a first power level, wherein the first power level is a minimum power level;
receive a first query response comprising first device information for a first wireless device within a network of wireless devices, wherein the first device information identifies an aspect of the first wireless device;
receive a second query response comprising second device information for a second wireless device within a network, wherein the second device information identifies an aspect of the second wireless device;
generate a first wink message, wherein the first wink message comprises instructions for a receiving device to provide a visible indicator of receipt of the first wink message, wherein the receiving device is one of the wireless devices;
select the first wireless device;
transmit the first wink message to the first wireless device; and
receive location information from a location database for the first wireless device, wherein the location information identifies the location of the first wireless device; and
request storing of information associating the location information with the first wireless device in response to the visual indicator; and
memory configured to store information associating the location information with the first wireless device.
8. The device of claim 7, wherein the processor is configured to:
select the second wireless device;
generate a second wink message, wherein the second wink message comprises instructions for the receiving device to provide a visible indicator of receipt of the second wink message;
transmit the second wink message to the second wireless device;
receive location information from the location database for the second wireless device from the second wireless device; and
associate the location information with the second wireless device.
9. The device of claim 7, wherein the first device information uniquely identifies the first device.
10. The method of claim 7, wherein the first device information identifies a function of the first device.
11. The method of claim 7, wherein the antenna is a directional antenna.
12. The device of claim 7, wherein the processor is configured to rebroadcast the device query at a second power based on the received query responses.