Abstract: A system and methods are provided for controlling interventional devices using magnetic resonance imaging (“MRI”) guidance. In some aspects, the method includes arranging a pivoting guide about a subject's anatomy that is configured to direct an interventional device toward a selected target point within the subject's anatomy, generating, using an MRI system, MR data associated with markers placed on the pivoting guide, and determining a vector defining an orientation of the pivoting guide from locations for the markers identified using the MR data. The method also includes orienting the pivoting guide in multiple directions to determine multiple vectors, and identifying a pivot point for the pivoting guide using the determined vectors. The method further includes determining a trajectory for the interventional device using the identified pivot point and the selected target point, and controlling the interventional device along the determined trajectory.

Abstract: A system and methods are provided for controlling interventional devices using magnetic resonance imaging (“MRI”) guidance. In some aspects, the method includes arranging a pivoting guide about a subject's anatomy that is configured to direct an interventional device toward a selected target point within the subject's anatomy, generating, using an MRI system, MR data associated with markers placed on the pivoting guide, and determining a vector defining an orientation of the pivoting guide from locations for the markers identified using the MR data. The method also includes orienting the pivoting guide in multiple directions to determine multiple vectors, and identifying a pivot point for the pivoting guide using the determined vectors. The method further includes determining a trajectory for the interventional device using the identified pivot point and the selected target point, and controlling the interventional device along the determined trajectory.

Abstract: An image reconstruction method applicable to a number of different imaging modalities including magnetic resonance imaging (MRI), x-ray computed tomography (CT), positron emission tomography (PET), and single photon emission computed tomography (SPECT) is disclosed. A sparsifying image is reconstructed from a series of acquired undersampled data to provide a priori knowledge of a subject being imaged. An iterative reconstruction process is further employed to iteratively determine a correction image for a given image frame that, when subtracted from the sparsifying image, produces a quality image for the image frame.

Abstract: A three-dimensional projection reconstruction pulse sequence acquires two half echoes in a steady state free precession (SSFP) scan. A method for combining the two echoes to suppress either fat or water in the reconstructed image is described and includes shifting the phase of one echo and combining them in a regridding process used to transform the radial data to a Cartesian grid prior to image reconstruction. Images having either fat or water substantially suppressed are then produced by applying a phase difference mask to images reconstructed from the regridded data. These images are then further processed using information of the phase differences between the two half echoes. In this manner, more consistent and accurate suppression is achieved.

Abstract: A method for measuring the apparent transverse relaxation time (“T*2”) and apparent diffusion coefficient (“ADC”) of a hyperpolarized gas in a single breath-hold and consequently, with a single dose of the hyperpolarized gas contrast agent, is provided. The method employs a multiple-echo projection acquisition based pulse sequence. Individual images are reconstructed from data acquired during each of the individual echo times. Subsequently, T*2 and ADC are calculated using these reconstructed images. Furthermore, the method produces images indicative of ADC that have isotropic resolution, allowing for more reliable image registration. The inter-echo spacing and diffusion weighting b-value are varied during the pulse sequence employed when practicing the present invention; thus, a significant separation between the effects of diffusion and T*2 decay on the detected MR signals is possible. This separation allows for reliable measurements of these two parameters from a single echo-train.

Abstract: Acquisition of MR data during a fMRI study employs a hybrid PR pulse sequence to acquire projection views from which multi-slice image frames may be reconstructed that depict the BOLD response to an applied stimulus or performed task. Composite images are reconstructed at each slice using the combined interleaved projection views from all the acquired image frames. The composite images are used to reconstruct the highly undersampled image frames.

Abstract: A three-dimensional projection reconstruction pulse sequence acquires two half echoes in a steady state free precession (SSFP) scan. A method for combining the two echoes to suppress either fat or water in the reconstructed image is described and includes shifting the phase of one echo and combining them in a regridding process used to transform the radial data to a Cartesian grid prior to image reconstruction. Images having either fat or water substantially suppressed are then produced by applying a phase difference mask to images reconstructed from the regridded data. These images are then further processed using information of the phase differences between the two half echoes. In this manner, more consistent and accurate suppression is achieved.

Abstract: A method for measuring the apparent transverse relaxation time (“T2*”) and apparent diffusion coefficient (“ADC”) of a hyperpolarized gas in a single breath-hold and consequently, with a single dose of the hyperpolarized gas contrast agent, is provided. The method employs a multiple-echo projection acquisition based pulse sequence. Individual images are reconstructed from data acquired during each of the individual echo times. Subsequently, T2* and ADC are calculated using these reconstructed images. Furthermore, the method produces images indicative of ADC that have isotropic resolution, allowing for more reliable image registration. The inter-echo spacing and diffusion weighting b-value are varied during the pulse sequence employed when practicing the present invention; thus, a significant separation between the effects of diffusion and T2* decay on the detected MR signals is possible. This separation allows for reliable measurements of these two parameters from a single echo-train.

Abstract: An image reconstruction method applicable to a number of different imaging modalities including magnetic resonance imaging (MRI), x-ray computed tomography (CT), positron emission tomography (PET), and single photon emission computed tomography (SPECT) is disclosed. A sparsifying image is reconstructed from a series of acquired undersampled data to provide a priori knowledge of a subject being imaged. An iterative reconstruction process is further employed to iteratively determine a correction image for a given image frame that, when subtracted from the sparsifying image, produces a quality image for the image frame.

Abstract: A fast and efficient method for reconstructing an image from undersampled, parallel MRI data sets acquired with non-Cartesian trajectories includes the calculation of unsampled k-space data from the acquired k-space data and sets of calculated reconstruction coefficients. To reduce the computation time, only a few reference reconstruction coefficients are calculated using a matrix inversion step and the remaining reconstruction coefficients are produced by interpolating between the reference reconstruction coefficients.

Abstract: A calibration procedure is performed prior to an off-axis MR scan to measure the MRI system timing errors in applying a frequency modulation waveform to the system receiver. Phase errors which otherwise occur when performing non-Cartesian scans are either prospectively reduced by offsetting the timing error or retrospectively offset by applying phase corrections to the acquired image data.

Abstract: A three-dimensional projection reconstruction pulse sequence acquires two half echoes in a steady state free precession (SSFP) scan. A method for combining the two echoes to suppress either fat or water in the reconstructed image is described includes shifting the phase of one echo and combining them in a regridding process used to transform the radial data to a Cartesian grid prior to image reconstruction.

Abstract: A calibration procedure is performed prior to an off-axis MR scan to measure the MRI system timing error in applying a frequency modulation waveform to the system receiver. Phase errors which otherwise occur when performing non-Cartesian scans are either prospectively reduced by offsetting the timing error or retrospectively offset by applying phase corrections to the acquired image data.

Abstract: Two images are acquired using a three-dimensional projection reconstruction, SSFP pulse sequence. Different RF phase cycling patterns are used to acquire each image and a fat suppressed water image is produced by combining the two images. Data acquisition efficiency is increased by aquiring k-space data during substantially the entire readout gradient waveform produced during the SSFP pulse sequence.

Abstract: A 3D projection reconstruction pulse sequence is employed to acquire CEMRA images. In one application of the invention an undersampled, high resolution abdominal CEMRA image is acquired in a single breathhold. In another application of the invention a series of undersampled image frames are acquired during a CEMRA dynamic study Each image is produced by combining peripheral k-space data from adjacent image frames with the central and peripheral k-space data of an acquired image frame.

Abstract: A 3D projection reconstruction pulse sequence is employed to acquire CEMRA images. In one application of the invention an undersampled, high resolution abdominal CEMRA image is acquired in a single breathhold. In another application of the invention a series of undersampled image frames are acquired during a CEMRA dynamic study Each image is produced by combining peripheral k-space data from adjacent image frames with the central and peripheral k-space data of an acquired image frame.

Abstract: In accordance with the invention, spatially invariant B.sub.0 eddy currents induced by a slice-selection gradient, G.sub.Z in an MRI system, are compensated by phase modulating the RF excitation pulse with a compensating function. In one embodiment, the compensating function is based on a measure of the integral of the B.sub.0 eddy current. In another embodiment, a scaled copy of the excitation gradient can be used as an approximation of the compensating function.