Kawin Assignee Setsompop

US Patent:

8076939, Dec 13, 2011

Filed:

Apr 10, 2009

Appl. No.:

12/422017

Inventors:

Kawin Setsompop - Cambridge MA, US
Elfar Adalsteinsson - Belmont MA, US
Vijayanand Alagappan - Aurora OH, US
Lawrence Wald - Cambridge MA, US

Assignee:

The General Hospital Corporation - Boston MA

International Classification:

G01V 3/00

US Classification:

324309

Abstract:

A system and method for producing an image indicative of characteristics of a radiofrequency (“RF”) coil with a magnetic resonance imaging (“MRI”) system is disclosed. The method includes acquiring MR signals while performing a pulse sequence with the MRI system and driving the RF coil at a selected transmission power. This process is repeated a plurality of times to drive the RF coil at a different transmission powers during each repetition. A plurality of images are reconstructed from the acquired MR signals and an image indicative of RF reception characteristics of the RF coil is produced from the reconstructed images. Subsequently, an image indicative of RF transmission characteristics of the RF coil is produced using the image indicative of the RF receiver response. More specifically, only one data acquisition is necessary for each RF coil element to produce the image indicative of the RF transmission characteristics for that coil element.

US Patent:

8085044, Dec 27, 2011

Filed:

Aug 20, 2009

Appl. No.:

12/544714

Inventors:

Kawin Setsompop - Cambridge MA, US
Borjan A. Gagoski - Cambridge MA, US
Elfar Adalsteinsson - Belmont MA, US
Vijayanand Alagappan - Streetsboro OH, US
Lawrence L Wald - Cambridge MA, US

Assignee:

The General Hospital Corporation - Boston MA

International Classification:

G01V 3/00

US Classification:

324309

Abstract:

A method for producing a spatially and spectrally selective radiofrequency (“RF”) excitation pulse includes establishing a desired spatial RF excitation pattern and establishing a desired spectral RF excitation pattern. The method also includes estimating an RF transmission profile map indicative of the transmission characteristics of an RF coil and determining, from the desired spatial and spectral excitation patterns and the estimated RF transmission profile map, at least one magnetic field gradient waveform indicative of locations in k-space to which RF energy is to be deposited. The method further includes determining, from the established spatial and spectral excitation patterns, the estimated RF transmission profile map, and the determined at least one gradient waveform, at least one RF excitation pulse waveform that will produce the desired spatial and spectral excitation patterns.

US Patent:

8148985, Apr 3, 2012

Filed:

Oct 15, 2009

Appl. No.:

12/580076

Inventors:

Adam C Zelinski - Watertown MA, US
Kawin Setsompop - Cambridge MA, US
Elfar Adalsteinsson - Belmont MA, US
Vivek Goyal - Cambridge MA, US

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01V 3/00

US Classification:

324309, 324318

Abstract:

A method for reducing maximum local specific absorption rate (“SAR”) in a magnetic resonance imaging (“MRI”) system is disclosed. More specifically, a plurality of candidate radio frequency (“RF”) pulses are designed and the manner in which they are applied to a subject is determined such that the maximum local SAR is substantially reduced relative to applying the candidate RF pulse that produces the lowest maximum local SAR alone. Put another way, this “time-multiplexing” of a set of RF pulses that each produce approximately the same excitation pattern yields a lower maximum local SAR than does transmitting the individual RF pulse having the lowest local SAR over many repetition times (“TRs”). A convex optimization method is utilized to determine the manner in which the RF pulses are multiplexed in time such that a substantially lower maximum local SAR is achieved.

US Patent:

8405395, Mar 26, 2013

Filed:

Apr 15, 2010

Appl. No.:

12/761314

Inventors:

Kawin Setsompop - Cambridge MA, US
Lawrence L. Wald - Cambridge MA, US

Assignee:

The General Hospital Corporation - Boston MA

International Classification:

G01V 3/00

US Classification:

324309, 324318

Abstract:

A method for multi-slice magnetic resonance imaging, in which image data is acquired simultaneously from multiple slice locations using a radio frequency coil array, is provided. By way of example, a modified EPI pulse sequence is provided, and includes a series of magnetic gradient field “blips” that are applied along a slice-encoding direction contemporaneously with phase-encoding blips common to EPI sequences. The slice-encoding blips are designed such that phase accruals along the phase-encoding direction are substantially mitigated, while providing that signal information for each sequentially adjacent slice location is cumulatively shifted by a percentage of the imaging FOV. This percentage FOV shift in the image domain provides for more reliable separation of the aliased signal information using parallel image reconstruction methods such as SENSE. In addition, the mitigation of phase accruals in the phase-encoding direction provides for the substantial suppression of pixel tilt and blurring in the reconstructed images.

US Patent:

20130002249, Jan 3, 2013

Filed:

Apr 23, 2012

Appl. No.:

13/453208

Inventors:

Lawrence L. Wald - Cambridge MA, US
Kawin Setsompop - Charlestown MA, US

International Classification:

G01R 33/48
G01R 33/341

US Classification:

324309, 324322

Abstract:

A method for reducing local specific absorption rate (“SAR”) during imaging of a subject with a magnetic resonance imaging (“MRI”) system is provided. A radio frequency (“RF”) excitation pattern is selected for an RF coil array to be used during the imaging. In this RF excitation pattern, locations in which local SAR exceeds a preselected threshold value are identified. Examples of threshold values include regulatory limits on local SAR. Using the identified local SAR hotspot locations, a cancellation electric field pattern that is defined by so-called “dark modes” of the coil array is determined. Imaging of the subject commences using the RF coil array and the MRI system, in which the RF coil array is used to simultaneously produce an RF excitation field and a cancellation electric field using the respective field patterns. This simultaneous production of the RF excitation and cancellation electric fields reduces local SAR at the hotspot locations.

US Patent:

20130015854, Jan 17, 2013

Filed:

Jul 13, 2011

Appl. No.:

13/181868

Inventors:

Elfar Adalsteinsson - Belmontt MA, US
Hans-Peter Fautz - Forchheim, DE
Kawin Setsompop - Charlestown MA, US
Lawrence Wald - Cambridge MA, US

International Classification:

G01R 33/44

US Classification:

324307

Abstract:

In a magnetic resonance apparatus and operating method therefor, and in a processor that is programmed to design RF pulses for operating such a magnetic resonance apparatus, the RF pulses are designed to mitigate off-resonance effects caused by inhomogeneity of the basic (B0) magnetic field in the magnetic resonance apparatus. The RF pulses of a parallel transmit array are designed with different spatial phase distributions, that deviate from a constant phase from pulse-to-pulse, with the absolute value of the difference between respective spatial phase distributions of any two successively radiated RF pulses corresponding to the off-resonance that is caused by B0-inhomogeneity during the time between the radiation of the successive pulses. Additionally, or separately, currents supplied to the shim coils can be taken into account in the design of the RF pulses as an additional degree of freedom, with the shimming of the basic magnetic field produced by the shim currents deviating from shim currents designed to ideally produce a homogenous B0 field.

US Patent:

20130099784, Apr 25, 2013

Filed:

Apr 23, 2012

Appl. No.:

13/453205

Inventors:

Kawin Setsompop - Charlestown MA, US
Lawrence L. Wald - Cambridge MA, US

International Classification:

G01R 33/54

US Classification:

324309

Abstract:

A method for imaging a subject with a magnetic resonance imaging (MRI) system using controlled aliasing is provided. A radio frequency (RF) excitation field is applied to excite the spins in a volume-of-interest that may include multiple slice locations. Using the MRI system, a readout magnetic field gradient is established following the application of the RF excitation field to form echo signals. These echo signal receive a differential encoding by way of establishing, while the readout gradient is established, alternating magnetic field gradients along two directions, such as the partition-encoding and phase-encoding directions. Image data is acquired from the formed echo signals and images of the subject are reconstructed from the acquired image data.

US Patent:

7336145, Feb 26, 2008

Filed:

Nov 15, 2006

Appl. No.:

11/599905

Inventors:

Adam Charles Zelinski - Cambridge MA, US
Elfar Adalsteinsson - Belmont MA, US
Kawin Setsompop - Cambridge MA, US
Lawrence L. Waid - Cambridge MA, US
Joerg Ulrich Fontius - Neunkirchen, DE

Assignee:

Siemens Aktiengesellschaft - Munich

International Classification:

G01V 3/00

US Classification:

334309, 324307

Abstract:

Waveforms for radio-frequency (RF) excitations pulses used in magnetic resonance imaging are designed according to a Least Squares QR (LSQR) algorithm or a Conjugate Gradient Least Squares (CGLS) algorithm, to solve the linear system of equations that arises in a multi-channel RF transmit arrangement. Better management of SAR and other factors is achieved with RF pulses designed according to these algorithms, compared to the conventionally employed singular value decomposition (SVD) algorithm.